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Response To L.A. County Review Sheet The Old Wrightwood Ranch Lots 1, 2 and 3 of Tract 45783 Los Angeles County, California
Project No. 2-1161-00 June 18, 1992
Prepared For:
Spindler Engineering 16823 Saticoy Street Van Nuys, CA 91406
Attn. Mr. Larry Gray
&@D - -- A.G.I. GEOTECHNICAL, INC.
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A.G.I. GEOTECHNICAL, INC. 7247 Hayvenhurst Avenue, Unit A-2 - Van Nuy•, CA 11406 • (818) 785-5244 - FAX (818) 785-1251
316 Tejon Place, Palos Verdes Estates, CA 90274
June 18, 1992
Spindler Engineering 16823 Saticoy Street Van Nuys, CA 91406
Attention: Mr. Larry Gray
Project No. 2-1161-00
Subject: Response To L.A. County Review Sheet The Old Wrightwood Ranch Lots 1, 2 and 3 of Tract 45783 Los Angeles County, California
Dear Mr. Gray:
In accordance with your request, we have prepared this report in
order to update the project as the new Consultants of Record and to
respond to a County Review Sheet, dated 4/16/92. The scope of work
for this project included review of the referenced reports, maps
and publications (see list of references in the appendix),
discussions with you (the client) and with the County Geologist,
excavation of an approximately 123-foot long exploratory trench in
the vicinity of Lot 1 and the preparation of this report (including
maps and other graphics) which presents our findings and a response
to the County Review Sheet. A copy of the Review Sheet is included
in the appendix.
presented below.
For convenience, an itemized response is
Engineering Geology • Soil Engineering
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June 18, 1992
1. L.A. County:
Project No. 2-1161-00 Page 2
The consultant geologist and geotechnical engineer must
designate a safe buildable area free of geotechnical hazards
on each lot.
A.G.!.:
In order to designate a safe buildable area, it was first
necessary to agree upon a "target area" for the investigation.
The reason for this is that the entire parcel is within the
Alquist Priolo Special Studies Zone for the San Andreas Fault
Zone. In lieu of an investigation of the entire parcel for
evidence of active faulting (i.e., continuously trenching the
length of the parcel), it was decided to limit the
investigation to an area of the parcel which is most likely to
be developed. The area chosen for the investigation (by Mr.
Larry Gray of Spindler Engineering) included an approximately
so-foot wide zone along the south side of the proposed access
road measured from approximately the midpoint of Lot 2.
In order to determine whether any active fault splays of the
San Andreas Fault cross this "target area," an approximately
123-foot long continuous trench was excavated on Lot 1 in a
direction approximately perpendicular to the mapped trend of
the San Andreas Fault. The trench was excavated with a
backhoe to a maximum depth of approximately 14 feet. The
trench extended from the level area in the vicinity of the
proposed access road (at the approximate midpoint of an east
trending gulley) south up the existing natural slope (see
Plate 1). The trench location was plotted by inspection in
the field using site topography as depicted on the referenced
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June 18, 1992 Project No. 2-1161-00 Page 3
development plan by Spindler Engineering. No field stakes
were provided and no property corner markers could be located.
Geologic units encountered in the exploratory trench included
slopewash, residual soil, weathered and creep-affected
bedrock, and bedrock of the Pelona Schist Formation.
The slopewash encountered was generally three to six feet
thick and consisted of dark brown silty coarse sand with
bedrock fragments in a moist and moderately firm condition.
Note: The term slopewash is herein used to distinguish soil
which has apparently undergone transport and deposition from
soil which has apparently formed in place due to weathering of
the underlying bedrock. The term includes topsoil.
Beneath the slopewash was a zone of highly weathered and
creep-affected bedrock which ranged in thickness from four to
ten feet. It consisted of a variable mix of greenish gray to
gray residual soil (clayey silt to sandy silt), "residual core
fragments" of bedrock within residual soil and hard (but
creep-affected) bedrock. The variability in the thickness of
this zone was apparently due to the variable hardness of the
underlying bedrock. In areas dominated by hard and brittle
siliceous metamorphic rocks, bedrock with identifiable
structure and continuity extended nearly to the ground surface
whereas areas dominated by softer mica schists were overlain
by a thick zone of weathered material containing little or no
visible bedrock structure. In areas where foliation in the
bedrock was identifiable beneath the weathered zone, a change
in dip angle was generally discernable across the transition
from relatively unweathered bedrock to highly weathered (and
creep-affected) bedrock.
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June 18, 1992 Project No. 2-1161-00 Page 4
The bedrock underlying the site has been assigned to the
Pelona Schist Formation. Bedrock observed in the trenoh
generally consisted of dark gray mica schists and siliceous
metamorphic rocks which have been weathered differentially
according to composition. The bedrock was generally highly
fractured and moderately hard to locally very hard. Foliation
in the bedrock generally strikes in a northwest direction and
dips moderately to steeply to the south.
Although the bedrock was generally highly fractured, no
through-going gouge zones, disrupted soil contacts, springs,
seeps, etc. were observed in the trench.
The results of our field investigation indicate that
residential construction is feasible south of the proposed
access road within the setback limits shown on the
accompanying map. The setback limits are based on a 15'
setback from each end of trench T-lA and on a projected trend
of N65°W across the site, which is the general trend of the
san Andreas fault in the site area. The setback limits
presented shall supersede the setback limits contained in the
referenced reports.
The setback limits presented herein necessitate a
reinterpretation of subsurface conditions on Lot 3 from those
presented in the referenced reports. It is our opinion that
the southern of the two fault traces depicted in the previous
geotechnical maps does not cross Lot 3 between previous trench
T-2 and the east property line as shown. The control points
for this segment of the above inferred fault appear to be (1)
a contact between slopewash and alluvium (labeled "Probable
Fault Trace") encountered in Trench T-2 and (2) one of several
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June 18 1 1992 Project No. 2-1161-00 Page 5
segmented photolineaments presented by Allen Seward during an
investigation for the parent tract. Apparently neither of
these control points for the inferred fault received the
benefit of verification by continuous trenching into bedrock
across their path. The continuous trench excavated by this
office (into bedrock) on Lot l is located across the projected
traces of both the photolineament by Allen Seward and across
the "Probable Fault Trace" reported in Trench T-2.
It should be recognized, however, that the setback limits
presented herein do not dispute the presence of the remaining
fault traces depicted on the previous geotechnical maps
(mainly north of the proposed access road). In addition,
because the site is entirely within the Alquist-Priolo Special
Studies Zone, we recommend that the remainder of the site
which has not been trenched in a continuous fashion be
designated as Restricted Use pending future investigation.
The Restricted Use designation applies to all habitable
structures but does not apply to sheds, detached garages,
roads, driveways or septic systems.
Note: All recommendations presented in the referenced
geotechnical reports concerning grading and/or construction of
the proposed improvements which are not amended herein remain
in effect and should be followed. All grading should be
observed by a representative of this off ice to see that the
work is performed in accordance with our recommendations and
to ensure that site conditions are as anticipated.
Any future development plans for the subject lots should be
reviewed by a representative of this office to ensure that all
pertinent design recommendations and required setbacks are
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June 18, 1992 Project No. 2-1161-00 Page 6
taken into account. If, at any time, it is desired to remove
the Restricted Use designation for any of the remaining
portions of the parcel, an additional detailed field
investigation would be required. Depending on where any
future proposed structures are located on Lot 1, it may become
necessary to excavate and recompact the loosely backfilled
trench excavated for this investigation.
rt should be recognized that the subject site is located in a
very seismically active area. The intent of this
investigation and report is to minimize the risk of primary
ground rupture beneath proposed habitable structures by
requiring them to be located away from known active fault
traces. Such required building setbacks will reduce the risk
of damage to structures during small to moderate earthquakes
by reducing the risk of primary differential fault movement
occurring beneath the structures. such building setbacks,
however, do not prevent damage during large earthquakes due to
ground shaking. (In addition, surface ruptures during
earthquakes do not always follow previous ground breaks and
may occur anywhere within a fault zone).
If a large-magnitude earthquake were to occur on the San
Andreas Fault in the Wrightwood area, many homes will
experience severe structural damage or even collapse,
including any future homes constructed on the subject lots.
No guarantee is herein expressed or implied that any portion
of the subject parcel will be free from primary ground
rupture, damaging ground shaking, debris flow or rock fall
during a major seismic event.
should be made known to any
renters, etc. It is understood
Full disclosure of this fact
future buyers, developers,
that the homeowner or renter
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June 18, 1992 Project No. 2-1161-00 Page 7
2.
assumes all responsibility for the risk associated with
residing in the Wrightwood area.
L.A. County: Provide a "change of consultants" letter from
the new geotechnical consultants stating that they are the
Consultants of Record and that they have reviewed the reports
by the previous consultants and agree with their findings,
conclusions, and recommendations or present their own.
A.G.I.
3.
We have prepared a Change-Of-Consultants letter for the
subject project, dated June 18, 1992. As mentioned above, we
have reviewed the previous geotechnical reports for the
project and generally agree with their findings and
recommendations. However, we herein modify the previous
recommendations concerning Restricted Use Areas. It may be
necessary to modify other recommendations as new development
plans become available or as conditions encountered during
grading may warrant. Additional field work and/or analyses
may be needed on a lot-by-lot basis as plans become available.
L.A. County:
Provide a letter from the consultants regarding Restricted Use
Areas (showing where they are and referencing reports).
A.G.I.
Because the Restricted Use Area boundaries serve as the limits
of the "safe buildable areas" referred to in item no. 1, the
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June 18, 1992 Project No. 2-1161-00 Page 8
reader is referred to the above discussion. Restricted Use
Areas are shown on Plate 1.
4. L.A. County:
Depict Restricted Use Areas on the Final Map.
A.G.!.
No response. Compliance is under the purview of the Civil
Engineer.
s. L.A. county:
Submit 3 copies of the Final Map that have been signed and
stamped on each sheet by the geotechnical consultants.
A.G.!.
We will review the Final Map when it becomes available.
6. L.A. county:
Provide a receipt for verification fees of $360.
A.G.!.
No response.
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June 18, 1992 Project No. 2-1161-00 Page 9
This opportunity to be of service is sincerely appreciated. If you
have any questions, please contact our office.
Respectfully submitted,
A.G.I. Geotechnical, Inc. - ----_-·::-.:>"" _.----1
// ........... / .. -··:>-;...-5----~----..,.-:_.,_/ -- ,/
{_ __,'{__,,,,_ -Eric Smith
Senior Geologist
1~0-! <-~f"-----Keith W. Ehlert, C.E.G. 1242
ES/KWE:el
Enclosures: List of References Figure 1: Location Map (including overlay of A.P.
Zone) Figure 2: Geologic/Seismic Hazard Map (Envicom,
1975) Plate 1: Site Geologic Map (including Restricted
Use Areas) Plate 2: Log of Trench T-lA Copy of Review Sheet, dated 4/16/92
Distribution: (6) Spindler Engineering Attn. Mr. Larry Gray
I I I I I I I I I I I I I I I I I I I
June 18, 1992 Project No. 2-1161-00
R E F B R B N C E S
Barrows, A.G., and others, 1985, Earthquake Hazards and Tectonic History of the San Andreas Fault Zone, Los Angeles County, California: California Division of Mines and Geology Open File Report No. 85-10.
Envicom Corporation, 1975, Investigation of the San Andreas Fault Zone, Expected Earthquake Shaking and Slope Instability, Wrightwood, San Bernardino County, California, dated July 1975.
Hart, Earl W., 1990, Fault-Rupture Hazard Zones in California, Alquist-Priolo Special studies Zones Act of 1972 with Index to Special Studies Zones Maps: California Division of Mines and Geology Special Publication No. 42.
Los Angeles County Department of Public Works, Materials Engineering Division, Geologic Review Sheet, dated April 16, 1992.
Ross, D.C., 1969, Map showing Recently Active Breaks along the San Andreas Fault between Tejon Pass and Cajon Pass, Southern California: U.S. Geological Survey Map I-553.
RSA Associates, Inc., 1988, Alquist-Priolo study and Soils Engineering and Engineering Geologic Report Update, Job No. 3775-oo, dated January 4, 1988.
RSA Associates, Inc., 1988, Results of Percolation Tests, Job No. 3775-01, dated July 13, 1988,
RSA Associates, Inc., 1990, Response to L.A. County Review Sheets, Job No. 3775-02, dated July 30, 1990.
RSA Associates, Inc., 1990, Response to L.A. County Review Sheets Dated 10/25/90, Job No. 3775-03, dated December 4, 1990.
RSA Associates, Inc., 1991, Response to L.A. County Review Sheets Dated 10/25/90, Job No. 3775-03, dated January 31, 1991.
RSA Associates, Inc., 1991, Response to L.A. County Review Letter Dated June 19, 1991, Job No. 3775-04, dated August 6, 1991.
RSA Associates, Inc., 1991, Response to County Geotechnical Engineering Review Letter Dated June 19, 1991 and County Geologic Review Letter Dated June 26, 1991, Job No. 3775-05, dated August 22, 1991.
RSA Associates, Inc., 1991, Debris Flow, [Analysis Of Potential for) Job No. 3775-05, dated September 18, 1991.
I I I I I I I I I I I I I I I I I I I
June 18, 1992 Project No. 2-1161-00
R E F E R E N C B S
Spindler Engineering, Grading Plan - Tract 45783, dated September 1, 1987.
State of California, Special Studies Zones, Mount San Antonio Quadrangle, Official Map-Effective July 1, 1974, Scale: 1"=2000 1 •
u.s. Geological Survey, Mount San Antonio, California, Quadrangle (1988), scale: 1 11-2000 1 •
.. ·~
' -
LOCATION MAP
Source: U.S.G.S. Mount San Antonio Quadrangle (1988) FIGURE 1 Project No. Date: 2-1161-00 6/18/92
~&@O~ A.G.I. GEOTECHNICAL, INC. Scale: 1 .. _ 2000 , Revised:
Drawn by: TW
I I I I I I I I I I I I I I I I I I I
LOCATION MAP
Source: U.S.G.S. Mount San Antonio Quadrangle (1988)
Project No. 2-1161-00
~&@D~ A.C.I. OEOTECHNICAL, INC. Scala: l" " 2000'
FIGURE 1 Date: 6/18/92
Revised:
Drawn by: TW
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Explanation:
------------
GEOLOGI({SEISMIC HAZARD MAP
Fault Hazard Zone. Includes 1857 Break (heavier dashed line) and other faults in the Zone of Major Faulting
\ \
Source: Envicom Corporation, Geologic/Seismic Hazards Map (Plate 1), Wrightwood, CA. June lg75 Fl GURE 2
- ill@D - ~-· A.G.I. GEOTECHNICAL, INC.
Project No. 2-1161-00
Scale: l" "' 400 ,
Approved by: _ ..... _ c:::....-1-...... .
' / ·/
Date: 6/l8/g2
Revised:
Drawn by: TW
I T01
FROM:MATERIALS ENG.D!U. ro: 818 785 5244 3· 12PM APR 22, 1992
Subd1v1slon S1ctlcn GEOLOGIC REVlrll
I FRI>!• Materials Eng1n .. r1ng Dlvhlon
SUBJECT! REVIEW OF FINAL MAP WITH PROCESSIHO
Dat11 4/18/92
I CENTER DATE __,3""'/2,,_4"'"/"'92._ ____ _
45783 I PARC Et OR TRACT MAP . tfO. :
LOCATION: 1'Wrlghtwood
HZn Unit of Traet: \
Job I L12 ! ~ Z § 1 //
I [!] Th1' m~p has not in~t th• requlramonts for filing for th• following reasons•
I I I
The consultant gtologlst and g1ottchnlcal •ngln11r must des1gnat1 1 'aft bu1ldab1t aria fr11 of gtot1chnlcal hazards on .. ch lot.
Provide a "chang1 of consultants" letter from th• newgeoteehnlca1 consultants stating that thly are thl Consultants of Record and that thay have reviewed the reports by the previous consultants and a9r11 with their findings, conclusions, and recommandatlon• or present their own.
Prcvlde a 11tt1r from the consultants re9ardlng Restricted Use Areas (show1ng whar1 they 1r1 and refar1nc1ng reports).
Depict Re1trlct1d Us1 AR11s on the Final Map.
Submit 3 cop11S of the Final M1p that have been sl;n•d and stamped on tlch sheet by tht ;tottchnlcal consultants.
Provide a receipt for verification f"s of $360.
1 Prepued by -~"'----"'---;,."', -~...-:-=---- Reviewed by ___________ _
I !Jr Oate 4/16/92
Charles N11tl1.
I G3:45783
I
P.02
-...... __ -....... ...........__
' . ' OVERSIZED~·~·
DOCUMENT HA.S BEEN PULLED AND SCANNED WITH THE MAP·.
FILE. .. .. _
... - ' ·-
' ,,,,
•
RSA Associates, Inc. Since 1956
C..:arporale C.>ffice: I S.414 (.abrito Road, Unit A, Van Nuy~, C:A q1406 • !818) 989·5338 • 26545-Bl Felix Valde.z: Avenue, Kanc:hoC:.'!lifornia. CA 92}9U• (714J 1)7b-8J82
A-v.Jutf Z I ( p~.- ?--"- It') ~ly;J.O..,. i990
The Old Wrightwood Ranch, Inc. c/o Spindler Engineering 7120 Hayvenhurst Avenue, Ste 200 Van Nuys, CA 71406
Job No.: Log No.:
3775-02 17407
Attention: Mr. Larry G. Gray Vice President
PROCESSING l,t11iiEH LAl~D DEV. DIV.
Subject: RESPONSE TO L.A. COUNTY REVIEW SHEETS DATED 6/19/90 AND 6/27/90 Lots l, 2 and 3, Tract 41777
Dear Mr. Gray:
The following are our responses to questions raised in the
L.A. County Geologic Review Sheets dated 6/27/90 and in the
Geotechnical Engineering Review Sheet dated 6/19/90.
GEOLOGIC REVIEW SHEET {6/27/90)
L.A. COUNTY:
l. Section 309 code requirement not met.
RSA:
We already provided a 309 statement on
preliminary . report of January 4, 1988.
located in a very high risk area. We
page 2 3 of our
This site is
feel that this
site as well as most of the community of Wrightwood has
Engineering Geology• Soil Engineering• Material Testing
1. ' ,,
The Old Wrightwood Ranch, Inc. -Juiy-.3..G-, 19 9 0
Job No.: 3775-02 Log No.: 17407 Page 2 hv;Jojf "J,/J
a safety factor less than 0.5 during a large earthquake
event on the San Andreas Fault, We reco:mmend compliance
with Section 308{c) where the applicant has submitted a
geological report complying with Section 309 which
report indicates that the site appears to be
geologically safe for the proposed use in the absence of
a major earthquake but is located in an area subject to
a hazard of a geological nature,
L.A. COUNTY:
2. Submit complete "geologic map" of Tract 45783 with
appropriate geologic cross sections. Indicate on cross
sections the depth of surficial materials and nature of
bedrock materials especially in the area of proposed
building sites.
RSA:
We have included is a copy of our original ,Geologic Map
and Cross Sections. A 15 foot setback has been shown on
the south side of the southern-most fault trace.
L.A. COUNTY:
3. Indicate on the geologic map the grading necessary in
order to create a building pad for each lot (1,2,3) and
any corrective work necessary (see attached Geotechnical
Engineering review sheet).
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Log No.: 17407 Page J
RSA:
No building plans have been submitted to us. The
current owner plans to provide only street improvements
at this time. However, the following recommendations
apply to any future proposed grading for building pads.
L.A. COUNTY:
4. Submit all necessary slope stability calculations (gross
and surficial) (static and seismic) for all natural and
envisioned graded slopes which may affect the proposed
building sites.
RSA:
calculations were made by simplified Bishop's method to
evaluate the minimum safety factor. Because .,no bedrock . ,.·,
sample was available a cohesion value o~ '500. psf and an.
angle of internal friction of JO degree is used as
representative cross bedding shear strength of the
bedrock. The cohesion value is assumed to be zero in
the case of shearing along bedding planes, Some
appropriate friction angles and cohesion value for
rocks and joint filling material reported by Hoek and
Bray are attached to this report to justify the use of
the above mentioned shear strength parameters. The
minimum static safety factor is 1.7 that is higher than
1.5 the minimum required by the Code.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Log No.: 17407 Page 4
Pseudostatic analysis were made to evaluate the minimum
seismic safety factor of the slope. Although in these
calculations the lower limit of estimated repeatable
ground acceleration corresponding to an earthquake on
San Andreas Fault having a magnitude of 8.25 is used,
the calculated minimum safety factor is only about O. 5
and much below 1.1 required by the building code. We do
not recommend any mitigation measures because in our
opinion mitigation measures are not feasible. The owner
may contact the Land Development Department of Los
Angeles County to sign a hold harmless agreement.
No calculations were made to evaluate the stability of
slope surface, because topsoil and slopewash are
classified as loose in our geologic report. Mitigation
measures were recommended in our original report No.
3775-00 dated January, 1987.
GEOTECHNICAL ENGINEERING REVIEW SHEET (6/19/90)
L.A. COUNTY:
1. Provide additional consolidation test results to
determine the area and depth of collapsible soils.
RSA:
Because no building pad was anticipated to be located on
the flatter portion of the site, no consolidation tests
were performed on alluvium. If it is decided to
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Log No.: 17407 Page 5
construct at the end of the driveway in the flat portion
of the site, all topsoil, slopewash, alluvium and
weathered bedrock in the area of proposed development
and 25 feet beyond building lines in all directions
should be removed, and replaced as compacted fill to the
proposed finish grade in order to decrease the
probability of liquefaction and subsidence. All
excavations or soil removals and all building pads on
the slope or flat part should be examined by our
geologist for verification of the required established
15 foot setback from a fault trace and to inspect during
construction grading for the potential of ground
rupture.
L.A. COUNTY:
2. All soils subject to hydroconsolidation under the
structures and beyond the line of influence of the
RSA:
building foundation must be mitigated.
mitigation measures.
Comply. Please see above item.
L.A. COUNTY:
Recommend
3. Areas not recommended to be mitigated must be designated
as "Restricted Use Area" if the depth of collapsible
soils is more than 4 feet.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Loq No.: 17407 Page 6
RSA:
Since depth of topsoil, slopewash and alluvium exceed 4
feet, the subject site should be considered as
restricted area unless on-site materials are processed
in accordance with our recommendations.
4. Provide the following for the proposed slough wall:
RSA:
a. Volume calculations to determine the total amount of slopewash material which could break loose. The slough wall must be designed to contain 100% of the volume and must consider splash-over effects.
b. Design parameters including impact forces.
c. Required wall height.
No building plans have been submitted to us. The
current plans show only a street improvement at this
time. However, if it is intended to locate a building
pad at the end of the driveway. Because this flat
portion of the site is located inside a natural drainage
channel, a civil engineer should design appropriate
diversion channels and determine the height of the
building pad in order to be at least 2 feet above the
anticipated highest flood elevation. All required
setbacks from this channel should be in accordance with
setback requirements of the agencies having
jurisdiction.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 LogNo.: 17407 Page 7
When the building plans become available to us we will
calculate the required height of slough walls in
accordance with the L.A. county requirements. All
slough walls should
least 150 lbs/cu. ft.
resist an impact pressure of at
of equivalent pressure and they
should be founded on firm sound bedrock or compacted
soils in accordance with our recommendations.
L.A. COUNTY:
5. Show the following on the geotechnical map:
RSA:
a. Existing and proposed grades.
b. Proposed building sites.
c. All grading and corrective work required for the building sites.
d. The area and overexcavation depth required for soils subject to hydroconsolidation and for slopewash and alluvial material.
e. Location of private sewage disposal system.
f. Restricted Use Area.
The grading plan is for a proposed street access only.
No proposed building sites have been designated at this
time.
a. To be provided by the project civil engineer.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Log No.: 17407 Page s
b. To be provided by the project civil engineer or architect.
c. To be provided by the project civil engineer.
d. Appropriate recommendations are provided in our reports, we will show the limits on our plans when the building pad locations are available to us,
e. To be provided by the project civil engineer in accordance with the recommendations in our report No. 3775-00 and 3775-01.
f. All of the subject site should be considered as restricted use area unless the on-site materials are processed in accordance with our recommendations,
L.A. COUNTY:
6. Show the following on the grading plans:
a. The area and overexcavation depth required for soils subject to hydroconsolidation and for slopewash and alluvium material.
b. Location of private sewage disposal system.
c. Proposed slough wall.
d. Proposed building sites.
Again, the proposed building sites are unknown. However, our recommendations for the future location,
grading and foundation work for these structures should
be followed.
RSA Associates, Inc.
I ,
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Log No.; 17407 Page 9
RSA:
a. We will indicate the area on our plans when building plans become available to us, the depth of removal is the depth to the sound bedrock.
b. To be provided by the civil engineer in accordance with our recommendations.
c. We will show them on our plans when building plans become available to us.
d. To be provided by the civil engineer or architect.
L.A. COUNTY:
7. Provide data on the possible adverse impact of the
private sewage disposal system relative to site
stability and adjacent properties.
RSA:
The sewage disposal system should be designed in
accordance with our previous recommendations presented
in our reports No. 3775-00 and 3775-01. However, if a
building area is located on the flat portion of the
site, we recommend the sewage disposal to be at least
100 feet away from the building area in order not to
saturate the soil close to the building, to avoid
eventual liquefaction and/or loss of strength due to the
anticipated severe shaking.
L.A. COUNTY:
8. The Geotechnical Engineer must review the grading plans
and sign and stamp the plans in verification of his
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Log No.: 17407 Page 10
RSA:
recommendations and the recommendations of the approved
geotechnical report.
We will review the grading plans upon our clients
request.
L.A. COUNTY:
9. Requirements of the Geology Unit must be complied with.
see response to Geologic Review Sheet (6/27/90) above.
L.A. COUNTY:
10. Please include a copy of this review sheet with your
response.
RSA:
Comply.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 21, 1990
Job No.: 3775-02 Log No.: 17407 Page 11
This opportunity to be of service is greatly appreciated. If you have any questions concerning this report, please do not
hesitate to contact this office.
Very truly yours,
RSA ASSOCIATES, INC.
~~~~U..-Michael Scullin, C.E.G. 170
i~.E. 861
MS/SM/JAV:el
Enclosures: Geologic Map Stability Section Calculations
Seyed Morteza Mortazavi, Ph.D. R.C.E. C 044091
Typical shear strength data
Distribution: (6) The Old Wrightwood Ranch, Inc.
RSA Associates, Inc.
Job No. _3_1--'1 ____ s_._o _z ___ I
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Job No. 3 '1 '1-r- .,.. 2 . Date 7- - ]o -1,q "'
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RSA Associates, Inc.
Job No. s'{'f)- 0 2 Section A - A/ Date t - lo - l'/ ~ u
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RSA Associates, Inc.
.. ... , , ·--·" -TA --
Table 4.3 Some Approximate Friction Angles and Cohesion Values for Rocks and Join1 Infilling Materials
Rock
Andcsitc Basalt Chalk Diorite Granite Grcywacke Limestone Monzonite Porphyry Quartzite Sandstone Schist Shale Siltstone Slate
•• (intact rock)
45 48-SO
53-SS ·S0-64.
f
45-SO 30-60 48-65
64 45-SO 26-70 45-64 -so 4S-60
Infilling material
Rcmolded clay gouge C~lcitic shear zone material Shale fault material Hard rock Breccia Compacted hard rocic aggregate Hard rock fill
••(discontinuity)
31-35 47 3S-4J
40 44 27-38
37 43
From Hoek and Bray 1974; U.S. Department of Transportalion. 1977.
q,• (ultimate)
28-30
31-33
33-37 28-32 30-34 26-34 25-34
27-32
25-34
c (massive rock) kNm-2
100-300
50-150
100-300
50-l50
25-100 . -
•• (approximate)
10-20 20-27 14-22 22-30 40 38
' '
' '
' : I
I ,
OVERSIZED ~~
DOCUMENT HA.S BEEN PULLED.
A.ND SCANNED WITH THE MA.P
FILE. ·--
. ' '
•
Since 1956 RSA Associates, Inc.
Corporate Office; 15414 Cabrito Ro,ld, Uni I A. Vdn Nuys. CA g140b • (B 18) 989-5338 • 2854.5-82 Fi!lix V.i.ldez Av~nue, REln(hO C.l:liforn'ia. CA 92J9U· (:' 14) 67&-8382
January 31, 1991
The Old Wrightwood Ranch, Inc. c/o Spindler Engineering 7120 Hayvenhurst Avenue, Ste. 200 Van Nuys, CA 71406
Attention: Mr. Larry G. Gray Vice President
Job No.: Log No.:
Subject: RESPONSE TO L.A. COUNTY REVIEW SHEETS Dated 10/25/90 Lots 1, 2 and 3, Tract 45783 (Fonnerly a part of Tract 41777) Wrightwood Area Los Angeles County, California
Dear Mr. Gray:
3775-03 17811
.. ,,.., ..,..,,
The following are our responses to questions raised in the
Los Angeles county Geologic Review Sheet and in the
Geotechnical Engineering Review Sheet, both dated 10/25/90,
GEOI.OGIC REVIEW SHEET (10/25/90
1. L.A. COUNTY:
The fault trace flattens northward as it nears the
ground surface (T-1 and T-2). During a future rupture
Engineering Geology• Soil Engineering• Material Testing
• The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 2
RSA:
along this fault the trace could flatten to the south.
Should this occur, would the recommended 15' setback be
sufficient to preclude the chance of a fault rupture
occurring beneath a structure?
The contacts between Qsw and Qal, shown in the logs for
Trenches T-1 and T-2, were not meant to depict a fault
trace. The inference depicted is that the sub-vertical
portion of the contact represents a fault scarp that was
fairly rapidly buttressed by slopewash before
significant scarp degradation took place. Once the
scarp was buttressed, normal slopewash deposition
continued across this contact in a northerly direction.
The geometry of the inferred fault scarp suggests a
sub-vertical fault. We do not anticipate significant
flattening of the fault trace either to the north or to
the south should a future seismic event occur on this
inferred fault. We believe a 15' setback will be
adequate to protect proposed structures from possible
fault rupture should an earthquake occur on this fault.
We have, however, reevaluated the recommended setback
with respect to the northwest corner of the subject
parcel. Based on the findings of Envicom Corporation
(1975), Mr. Alan E. Seward (1981) and RSA Associates
(1988) it is clear that the topographic bench at the
north end of the parcel is underlain by one or more
subsidiary faults of the San Andreas Fault Zone. Most
of this topographic bench (and its associated anomalous
RSA Associates, Inc.
.. The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 3
east-trending swale) is included in the setback
(restricted use area) which we established previously.
There is, however, a triangular-shaped area,
encompassing portions of lots 1 and 2, which lies
outside the current setback line but which is part of
the topographic bench. There is reasonable probability
that this section may also be underlain by subsidiary
faults of the San Andreas Fault Zone. Therefore, we
have extended our original setback line to follow a more
linear course along the southern edge of this
topographic anomaly
recommend that no
(see revised Geologic Map). We
structures for human occupancy be
constructed north of this setback line. The area north
of the setback line, however, may be used for private
sewage disposal systems.
2. L.A. COUNTY:
RSA:
The consultants must depict the following on the
geologic map (for each lot): a) a safe building site;
b) any grading required to create this safe building
site; c) recommended sewage disposal area.
Provided all of our recommendations are followed during
grading and construction, all areas south of the setback
line may be considered safe (for the intended use, as
determined by traditional methods of analysis) from
hazards associated with normal hillside processes, as
well as from the hazard of ground rupture due to
RSA Associates, Inc.
•
•
The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 4
faulting.
Appendix A.
See Seismic Stability calculations in the
It must be noted that the current engineering practice
is based on the existing ground motion records to date.
No records have yet been obtained of strong ground
motions in the immediate vicinity of a fault. The
nearest strong motion record to fault rupture was 80 ID
in the 1966 Parkfield earthquake, with a 5, 5 Richter
magnitude. Larger measured magnitudes have been
recorded at a substantially greater distances. Hence,
the current engineering practice for immediately
adjacent to strong ground fault rupture has been
extrapolated, and has never been verified to date by
engineering measurements.
Therefore, although analysis indicates that "safe"
building sites exist at the subject site, one must
realize that there exists a risk that the intensity of
projected ground shaking, ground lurching, or
seismically-induced earth flows as a result of a major
earthquake occur on the San Andreas Fault in the
vicinity of wrightwood may exceed that projected herein
and result in damage and/or slope failures. For this reason we recommend that the owner, and future buyers be
provided with copies of our reports and made aware of
these hazards .
At present, the tentative map proposes street grading
only. It is our understanding that the lots are to be
recorded and sold ungraded. This, of course, is common
practice. All potential purchasers, however, should be
RSA Associates, Inc.
• The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 5
informed in writing of the potential hazards associated
with the subject parcel which are described above and in
our previous reports.
a. Comply. We have shown recommended building sites
for each lot. As stated above, these sites are
safe from the hazard of ground rupture and from
hazards associated with normal hillside processes
provided all of our recommendations are followed
during construction.
b. The tentative map proposes street grading only.
The grading plan serves as the base for our
Geologic Map. It is our understanding that the
three lots included in the subject parcel will
likely be developed separately.
c. The recommended sewage disposal area is shown on
the plot plan accompanying our report of
percolation testing, dated July 13, 1988. The
reader is referred to that report. Restricted use
areas may be used for private sewage disposal
systems.
3. L.A. COUNTY:
Verify date of report (Job No. 3775-02): a. 7/30/90
(pp. 1 and 2, calculations and 2 plates) or; 8/21/90
(pp. 3-11).
RSA Associates, Inc.
• The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 6
RSA:
This clerical error has been corrected.
date of the report is 8/21/90.
The correct
4, L.A. COUNTY:
Comply with Geotechnical Engineering Unit's review sheet
... dated 10/25/90, attached.
RSA:
See response to Geotechnical Engineering Review Sheet,
dated 10/25/90, below.
5. L.A. COUNTY:
Reports should address Tract 45783, not 41777.
RSA:
This oversight has been corrected.
GEOTECHHICAL ENGINEERING REVIEW SHEET (10/25/90)
L L.A. COUNTY:
The report indicates that the seismic slope stability
analysis is below safety factor 1.1. Recommend
mitigation measures, a hold harmless agreement is not
acceptable.
RSA Associates, Inc.
• The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 7
RSA:
We have reviewed and re-computed our analysis. The
results are presented in the Appendix. In accordance
with current accepted Los Angeles County geotechnical
engineering practice, the pseudo-static analysis
indicates that a minimum factor of safety of 1. L+~ts
at the site. It is our opinion that all residential
- ---- structures in Wrightwood will be subjected to very high
9)l'tl'1Dd motion due to earthquake activity on the San Andreas Fault. The site, if built with impact walls and
diverter walls, appears to be geologically safe for the
proposed use but is located in an area (Wrightwood)
where the hazards, as analyzed herein, may be exceeded
in the event of severe activity along the San Andreas
Fault.
Potential Hazards
The method of
required by
pseudo-static analysis of slopes as
Los Angeles County evaluates seismic
stability of deep seated potential failure. We are not
aware of known seismically induced deep seated
landsliding in hard rock formations such as at the subject site. The well known cases of massive
seismically induced ground failure were a result of
severe loss of strength of sensitive clays or from pore
pressure buildup in fine sandy materials brought about
by the intensity of shaking. The site bedrock is not
subject to severe loss of strength. It is our opinion,
given the favorable results of pseudo-static analysis
RSA Associates, Inc.
• The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.; 17811 Page a
that the possibility of seismically induced bedrock
failure is very low.
On the other hand, buildup of pore pressure due to
shaking in the surficial soils resulting in flows merits
consideration. It is our opinion that the potential of
seismically induced debris flows at the subject site are
probably not greater than the potential under severe
rain or snow melt. We base this on our shear test
results, which indicate firm materials, slopes are less
than 2:1 in steepness, and the that previous
investigation on the subject site by Allen E. Seward
Engineering Geology Inc. and Brian Robinson and
Associates, Inc. found sufficient jointing and
permeability in the Pelona Schist to suggest that a
phreatic surface may not be able
bedrock contact. Without a
liquifaction can not occur.
2. L.A. COUNTY:
to form along the
phreatic surface
As previously requested, provided the following
information for the proposed slough wall:
a. Volume of debris anticipated to break loose.
b. Wall height and/or required catchment area.
Show the proposed slough wall on the geotechnical
cross-section.
RSA Associates, Inc.
• The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 9
RSA:
a. We have calcula.ted the watershed which is tributary
to the proposed development area to be
approximately 2.32 acres. Using guidelines
outlined in·the city of Los Angeles• Memorandum of
General Distribution #63, we have assumed a value
of 400 cubic
debris which
event. Thus
yards per acre for the volume of
could break loose during a single
the volume of debris anticipated to
break loose is 928 cubic yards,
b. All slough walls should be a minimum 5 feet high
and
of
should be designed to resist
at least 150 lbs/sq.ft,,
an impact pressure
equivalent fluid
pressure. No catchment area is required. It is
pro_p(>~l:l<'! __ t.o~ -dly~""i_J;:·:th"e_ii;;-;.- t·~-th-;-;ri:;;te proposed ---- '' 1-··-· .. ··-·· .......... """"'"""" '"-··-·-· --··· ·-·,,···· •'"" "'"' __ ..,_
street. _The low ridge north of the proposed road
-·-wTrr·a~t- in combination with the slough walls to
prevent any mud flow which is generated on-site
from affecting down-slope properties.
Recommended slough walls are shown on the attached
Area Map and on the revised cross section A-A'.
3. L.A. COUNTY:
Comply with item No. 5 of the Geotechnical Engineering
Review Sheet dated 6/19/90.
Item 5 of Review Sheet 6/19/90 states:
RSA Associates, Inc.
•
•
The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 10
RSA:
Show the following on the geotechnical map:
a. Existing and proposed grades
b. Proposed building sites ·
c. All grading and corrective work required for the
building sites
d. The area and overexcavation depth required for
soils subject to hydroconsolidation and for
slopewash and alluvial material
e. Location of private sewage disposal system
f. Restricted Use Area
The tentative map proposes only street grading at this
time. It is our understanding that the lots included in
this parcel are to be t-ecorded and sold ungraded.. It is
common practice to do so provided full disclosure is
made in writing to prospective buyers concerning any
potential geologic hazards associated with the property.
We have shown recommended building sites on the revised
Geologic Map. We have established restricted use areas
and shown them on the revised Geologic Map. We have
sbown recommended areas for private sewage disposal (See
RSA report, dated July 13, 1988). It would, however, be
fruitless for us to speculate on the configuration of
the proposed future building sites. We have made
recommendations for all grading and corrective work
necessary for the building sites. These recommendations
should be followed by any design civil engineer who
prepares a grading plan for any of these lots. We will
RSA Associates, Inc.
• The Old Wrightwood Ranch, Inc. January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page 11
be happy to review any such grading plan with respect to
our recommendations when such becomes available.
4, L.A. COUNTY:
RSA:
Th~ Geotechnical Engineer must review the grading plans
and sign and stamp the plans in verification of his
recommendations and the recommendations for the approved
geotechnical report.
plans for review.
Submit a complete set of signed
We will review the grading plans upon our client's
request.
S. L.A. COUNTY:
RSA:
The Geotechnical Engineer must sign, stamp and indicate
the date of registration expiration on the soils report
and all addenda.
No comment.
6. L.A. COUNTY:
Requirements of the Geology Unit must be complied with.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. January 31, 1991
RSA:
Job No.: 3775-03 Log No.: 17811 Page 12
See response to Geologic Review Sheet, dated 10/25/90,
above.
7. L.A. COUNTY:
Please include a copy of this review sheet with your
response.
RSA:
Comply.
This opportunity to be of service is greatly appreciated. If
you have any questions concerning this report, please do not
hesitate to contact this office.
Very truly yours,
RSA ASS CIA INC.
c is, Dietz R.G~ Expires: 3/31/92
~~ Michael Scullin, C.E.G.
CD/MS/JAV: el
170 ~·
Enclosures: Location Map, Geologic Map Geologic Cross Section, Area Map Copy of Geologic Review Sheet, dated 10/25/90 Copy of Geotechnical Engineering Review Sheet, dated 10/25/90
Distribution: (6) Mr. Larry G. Gray
RSA Associates, Inc.
LOCATION MAP
Antonio USGS Mount San l ( 1988) Quadrang e
RSA Associates, Inc.
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page: A. l
STRENGTH PARAMETERS FOR STABILITY ANALYSIS
General:
We obtained adopted "peak" and "ultimate" bedrock shear
strength parameters as discussed herein. The subject site
and ascending hillside is underlain with the Pelona Schist.
The Pelona Schist is foliated. Foliation dips favorably into
slope. The purpose of this discussion is to determine the
strength across foliation. Except for the weathered zone
immediately below the contact with slopewash, the schist is
too hard to sample with standard sampling equipment and test
in the standard soils test direct shear machine. We returned
to the site and obtained hard chunk samples of the Pelona
Schist from the remaining spill from our old trench
excavations taking the hard chunks as having come from the
bottom of trenches in the more competent bedrock.
Where the strength of rock in a formation are relatively
high, the over all strength of the formation will be
controlled primarily by discontinuities such as bedding
planes, joints and fractures (slippage along
discontinuities), and secondarily by the strength (or
rupture) of the intact rock material. For the case at hand,
the significant discontinuities consist of joints and
fractures.. Foliation is favorably oriented for gross
stability. The rock formation mass quality and strength of
intact rock in formation must be determined.
RSA Associates, Inc.
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
strength of Intact Rock
Job No.: 3775-03 Log No.: 17811 Page: A.2
In order to quantify the strength parameters
rock material, the unconfined compressive
determined. The Chunk samples obtained from
of the intact
strength was
the site were
sent to Smith Emery's laboratory to be cored and cut with
their rock cutting equipment into a test prisms. The samples
were returned to our laboratory and submerged under water
for one week. Only one out of four samples was cored so that
its axis was perpendicular to the foliation, however, all
sa~ples were tested. The samples were placed in a concrete
compression test machine and loaded to rupture, Failure
occurred abruptly with diagonal cracks and/or vertical splits
forming. As expected for anisotropic materials, samples that
failed along foliation plane tested weaker, than the sample
that failed across foliation.
Table 1 below.
The results are presented in
The results of Sample No. 3, the sample which failed across
foliation, were taken as the cross bedding unconfined
compressive strength. A value of 1000 ksf (6944psi) was
adopted for subsequent calculations.
\.
RSA Associates, Inc.
• Appendix A Job No.: 3775-03
Log No.: 17811 Page: A.3
The Old Wrightwood Ranch, Inc January 31, 1991
Table 1
Compressive strength
Sample Least Rupture No. Height Dim lid Factor FQ;rce Area i:?:tress
1
2
3
4
Sample No,
l
2
3
4.25 11 1.75 11 2.43
4.51 11 1.75 11 2.58
3.20" 1.75 11 1.83
2.75 11 1.75 11 1.57
Comments
1. 00
1. 00
0.98
0.96
No visible joints. along foliation.
No visible joints. along foliation.
No visible joints, failed along plane foliation.
4200# 2.41112 1746psi
5200# 2.41112 2162psi
19250# 2.41 112 7830psi
3700# 2.41 11 2 1538psi
Foliation 75 •, Sample failed
Foliation 30', Sample failed
Foliation horizontal. 65' from horizontal
Sample across
4 Vertical joints. No foliation within sample. Sample failed along vertical splits and along plane 65' from the horizontal. Ruptured sample appeared to be more weathered than other samples.
Mass Quality of Bedrock Formation
The rock mass quality of the formation must be determined.
The method of engineering classification of jointed rock mass
of the CSIR (Commonwealth Scientific and Industrial Research
Organization) after Bieniawski was utilized and a tabulation
RSA Associates, Inc.
, Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page: A. 4
for classification is presented in Plate Al. Six
classification parameters are required:
1. strength of intact rock
2. Drill core quality RQD
3. Joint spacing
4. Joint condition
5. Groundwater
6. orientation of joints
The first item was determined by laboratory testing. The
last four items were determined by observation and judgement
of our geologist. The RQD was approximated by an empirical
relationship based a spacing of joint sets
Engineering, by J. A. Frankl in and M. B.
presented in EQ.Q.t
Dusseault, 1989,
pp 51-2. Three near orthagonal joint sets were observed in a
road cut at the end of Timberline Drive with an average
spacing of 8 11 •
Volumetric Joint Count, Jv = 1/.2 + 1/.2 + 1/.2 = 15 / m2
RQD = 115 - 3.3Jv RQD = 65.5
The engineering classification of jointed rock mass for the
Pelona Schist formation of the hillside in question is
presented in Table 2 below. We computed a CSIR rating of 51
but conservatively adopted 44 for fair quality rock mass in
subsequent calculations.
RSA Associates, Inc.
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page: A.5
1.
2.
3.
Table 2
Engineering Classification of Jointed Rock Mass
Strength: (50-100 MPa) = (7500-15000 psi)
RQO: assume 50-75%
Joint Spacing: 8" o. 3-lm
Rating
7
13
20
4. Joint Condition: slightly rough, soft wall < 1 mm 12
6.
4.
Ground water: moderate pressure (conservative)
Orientation: Slope / Favorable
4
-5
51 Overall CSIR Rating =
"Peak" Shear Strength
The peak strength was determined by a simplified empirical
failure criterion developed by Hoek and Brown, presented in
Rock Slope Engineering, by E. Hoek and J. w. Bray, the
revised third edition. The method utilizes the unconfined
compression of clear rock and the CSIR rating of rock mass
quality. The formula and applicable constants are
reproduced in Plate A2 herein. The parameters of this
formula are the unconfined compressive strength of the clear
rock, three empirical constants depending upon the
engineering classification of jointed rock mass, and the type
or origin of rocJc. The category for lithif ied argillaceous
rock was selected for schist. The constants A, B, and T were
taken for a conservatively adopted CSIR rating of 44,
RSA Associates, Inc.
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
nominally a fair quality rock mass.
Job No.: 3775-03 Log No.: 17811 Page: A.6
For a
strength of 1000 ksf and the constants A = .234,
= -.0005 the following equation results:
compressive
B = .675 1 T
r = .234x(lOOO ksf) (o / (1000 ksf) - (-.0005)) .675
A plot of this formula is presented in Plate A3. A straight ·---~
\ line fit of a "cohesion" intercept of 3000 psf and phi = 35 • ) f-~,,,. L
./ 0
can be made. The above meth~ of determining peak stren_g:tlr/ ~/, = "">::-has been used in mining ~-;.;gii'iEHn--inq-----and----may ___ not-- be
appropriate for long term strength. However, it would be
quite appropriate as a seismic strength parameter for pseudo-
static analysis.
"Ultimate" Shear Strength
If the rock is sheared beyond the peak strength; shearing
will proceed along the cracks and ruptures that formed as the
peak was reached. As the cracks will probably not be
perfectly planar, the shear strength along these
discontinuities would consist of a basic phi angle
corresponding to the type of rock and the angle of the
asperities or the roughness of the joint or rupture surface.
The strength drops past the peak as slippage continues. The
ultimate strength of the rock is reached as the steeper
asperities along the joint/rupture surface are rode over or
sheared off. As slippage continues, more extensive damage
occurs to the joint surface and the remaining asperities are
eventual worn where only the residual strength of the base
rock remains along the slip surface.
RSA Associates, Inc.
I\~~. ·"'r';....., I.._~ -·- .-··' (J< .. i,_. '
i' ·--'
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page: A.7
The following relations are based on N. Barton's method as
extended in the article "Strength, Deformation and
Conductivity Coupling Of Rock Joints", by N. Barton, S.
Bandis, K Bakhtar, Int. J, Rock Mech. Min. Sci. & Geomech.
Abstr. Vol. 22 No. 3 pp. 121-140, 1985. Originally Barton's
method was an empirical relation of the peak strength along
an existing joint surface. The required parameters are:
1. JRC Joint Roughness Coefficient which may
determined visually or by testing.
2, JCS - Joint Wall Compressive Strength - may be
determined by Schmidt hammer rebound tests.
3. ¢r - Residual friction angle.
The formula is
T ~ o tan (¢r + JRC log10 (JCS/a))
The parameters should be determined by testing, however, for
the case at hand, we selected a JRC = 20, JCS = 80 ksf,
¢r .. 28' by fitting the parameters to approximate the peak
relation 99mputed--by:.-, .. HQek and Brown's method above. A
residual .phi angle of 30' ··-;,<Jld probably be reasonable. The
.joint roughness coeff~c,j.,ent·· appears reasonable for rock just
ruptured. ±he ·· J~int strength coefficient fitted is
considerable less than that tested for intact rock. However,
surface weakening due to rupturing is to be expected. A plot
of the curve is presented in Plate A3.
RSA Associates, Inc.
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page: A.8
The above cited article presents a standard method for
determining the shape of load deformation curve of rock based
a extensive research data. As the rock is strained past the
peak strength, Barton 1 s original relations is maintained,
except that the JRC is replaced with a JRC(mobilized) which
diminishes to zero as the residual strength is reached. The
ultimate strength is that computed substituting
JRC(ultimate) = 0.5 x JRC(peak) into the above relation. The
ultimate strength is plotted also in. l'l.ate A:t,._ A straight · ···
line fit of a "cohesion" intercept;.'6f 1000 psf a-~. phi = 32 • ) O I+, can be made. \...._ ·-~· ·1"" ':'· Z
0
To determine the load-deformation relation, deformation at
various stress levels must be determined. The peak
deformation, 6(peak) is given as
where
Ln JRCN' 33 6(peak) ~ 500 x Ln.33
= Joint length in spacing of cross at 18" = .45 m at
situ joints depth.
taken as average in meters, estimated
JRC adjusted to length of in situ joint. The same as determined above for the case at hand.
6(peak) = 0.0031 m = 0.12 11
The ultimate deflection 6 (ultimate) = lo x 6 (peak) . The
residual strength is reached at 6(residual) = 100 x 6(peak).
6(ultimate) = 1.2"
6(residual) - 12"
These values are required in deformation analyses.
RSA Associates, Inc.
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page: A.9
SEISMIC STABILITY ANALYSIS
Since no continuous geologic structural weaknesses were
found that
calculations
daylighted or paralleled the slope, the
were made assuming homogenous strength
conditions and a circular type potential failure surface.
Calculations were performed on an IBM PC computer utilizing
the program STABL5/PC. Section A-A' was modeled for
analysis of the gross hillside stability. The gross
stability calculations were repeated to search for the most
critical computed surface under static conditions.
The search routine of the program was utilized, which
generates trial surfaces according to the search limitations
imposed. Points for initiation of trial circles were
selected in the area around to base of slope of the whole
hill side below the existing bench area through which the
fault traces pass, and the area of the toe of ascending slope
above bench. Four initiation points for generation of 40
trial surf aces from each point were specified around the
lower toe and five initiation points for generation of 40
trial surf aces from each point were specified around the
upper toe. The termination limits only the randomly
generated trial surfaces whose terminating point fall between
these two horizontal coordinates are accepted by the program
for analysis - were specified from just below the minor
break in slope to the last profile coordinates defined. The
ultimate shear strength parameters from our previous reports
were utilized(~= 30', c = 500 psf). The initial search did
not indicate an initiation point of sharply reduced factors
of safety, except that the lowest computed factor of safety
was obtained initiating at the toe in each search. For a
RSA Associates, Inc.
Appendix A The Old Wrightwood Ranch, Inc January 31, 1991
Job No.: 3775-03 Log No.: 17811 Page: A.10
plot of the results see the attached computer print out in
Plates A4 and A5.
Two detailed searches were then performed, with each of the
above described toes defined as the initiation point for the
generation of 100 surfaces. The lower termination limit was
left unchanged.
to the lower
The upper termination limit was moved closer
limit. The most critical computed static
factor of safety was 1.990 from the lower toe and 1.869 from
the upper toe. For a plot of the results see the attached
computer print presented in Plates A6 and A7.
The most critical surface from the detailed search from each
toe was modeled and run with the peak shear strength
parameters (If' "' 35' C "' 3000 psf), and a pseudostatic
horizontal out of slope acceleration of .5g, and a vertical
upward acceleration of .25g to analyze seismic loading. The
computer factor of safeties of 1.100 for the lower toe and
1. 367 for the upper toe were
commonly accepted value of 1. 1.
presented in Plate AS.
obtained, greater than the
The computer print out is
RSA Associates, Inc.
]
J J J J J J J
__ J ]
J J J J J J J J
TAnllU. THI GEOMEmANJCS (:l.ASSll'ICAnON SYSTEM ro• JOllnm ROCll MASSES'
A. ~TIOH Pilla.AMITIU ANDntltHI lATINCf
.. 1"911.ftof hlni..laiMI'._,. >I ... ... I ••• U1111 .t •11illql ~PHl!Mwti ...---· ....._MP, "9r•md
in•lmrilll
• Uniii.:d1111IQ111111:~ -MP,
>100 t•·• ..... :i ... it~• :a.11 ••• - " " , - • ' • I
Drill .. qt111111titr ~ ... ,_ ,, __ ... _
:5-51'1> <"" I ..... .. " .. I I >
8C*lnf .. lcillt• »• 1~:11• ll·tlllt w-••• <ti-
' ...... .. .. .. ... I
v~" "1!.ll"' 111trf1C11. '~~MitfKm. Sl~fy ~ .wlMiB. S1id.ftl.lid..t ..,...,~ s.n:::o• Niii! coailnooua. N11 ~-.(:·-.. ~~<JIML i" .... tepmr111~. H.11d Hlild ~ ..,.11 taci.. Sol\lolnt-.Hfl!ld:_ ~< '111."'lt\fcl ..
CIJndttkin ol .... '""' wall tvt;l. .. juhmi-111inlll CrPt'l 1-1 m•. ! >l•a. • Contin\IOui: ioin411 ConU•llMQI
lolnG
·~ ... " .. " ' I • • I
lnllow plllt 10 iii N- <:-1$ -.,.,.ill I ~' 11'1 likn/miift -;.UI lllW"'illl ' h.Jn...i ~- I .. .. .. ..
Croundw•ler ..... ! I
lotntw.lw~ I ., ........ 2 '
>I.I
' ~pri~p11J .....
l :.1nvM.t ' .. .. .. G~""I COl'ldUIMI Cam"""tr cl:ry
~ IMlly lilll91"111101I NWMWllllllf~ ....... I rnodllftl~~ ·- " ' I • • I
Sutt1 udl~ -W11r.dMI .r . ..,..__ ·- ,. u.- .... -,.,., .... I _, -· -ti
_,,
"''• ,......._ • _, _, _,, _,, ·- • _, _,. i _,. -·
C. AIXK MAM~ ~ '11£111: IATINCt -- ' I • .. .. • - V•r'J 11101J rock """'- ··- --- V*l'J fl!*" l"llld!
Rallftf IOCl-to ,._,. ,,_,. I ,._,. <"
D Mf.ANINC OF mOCJI; .. ,,.. aAWl:I
o.1.- ' • .. .. y
... \•Hap !lilnd•up llmti ID f .. 'I lo!' ~fn 11t1mA fi--ihil 5111' ~ ... llPM 1-.•Swz-m.,,.. I ~hi-rot, ..... ~ ...• ,., ....... .,. Cohnlan n( lhli n11;• lllllllt. th , ... .,. __ ... ' lailTtll .,.. fridkin •na'-' .t th. ~Ii: IMll .... ...... ,. .... I »·•· .... I
C.v•bUMY'lll.,. V•ry poor W1111111 CIM '*9dlt,. •• I Will~mcf.U,. ........ ... "',...-, ! CO!ldf~WiMI. ·tr--i."'tlJll"Q.M_....,.. .... ..,........"'._~~illlt~U..-......._..~IMllil •I~ .. ..,..,r,tttui. • 191 ...... •Ul't/W. i"'~dll.amn.. .. .-...*'~
from Hunt, 1984 P/ak A I
t • 0
• • • • 0 .. • ~ • .. ~ • 0
0 g & 0 ~
• • .. • • .. ' • • g ~
0 • • • .. 5 • •
• 0 0 • • • g
• 0
~ g
• • ~ ~
~ • ... 5 • • •
- .
source: ~ Slope Engineering, E. Hoek & J.W, Revised Third Edition, page 108.
Bray,
- -APPROX I HATE RELATio"SHIP l!HllEEM ~OC( l<A$S "Q.uALtl'r AHO EllP1"1C~ CONSTANTS
__. • • "' N __. ll
__. ... .. "' .. ' 1 « 11 :!!;:! .... u 11 >o< "' .. j!: ~ ,., ... :i! .. g ·~ w- i: !I! 1: EllJ'il'ical faii"1"<1 cl'itel'itm " ... • .a • " ... .11 1-U j ... JN _ .... .. _ _, ... ... l ~.ii i ;J :;! '"lfu ~ ~ i! .a ;:t ...... "
'Iii 0'3 + lfli0ca3 • 1Ge2 ....
~I ~tnS .... "' ll f~3 li"~ 01 l2:;; j .... " <:> ,. .... u ...... .... .. "' "' g~ ~ i~9 1 ....
~1 ; gt; ·~ 'll
- ""~(•I a T_ )1 "'.., - .. - .... '""' _,.,_
11· t · .1' .. - ~~Ci """ :! "'" .,. ll < ..... _j- . . e . ·11- J -<:> "'" ..... 11111
i~ r O~OMJ :! :;: 11 .. .,_
:& .; l ~~ i:: -i~>~ u where T • i(m - /m2 ~ ~.) ].! "'"' ·~!
... u-<> .... -\2 "' .... ,,. 1
_.,, "' - " ll1 ...... eg w~~~ ... " 1- "' ...... l!'i:;~ .a 1 11~ "'u u ~ ...... .=! .... 0 _, --<:> u .... .... .. .... ., "--'"' u :! i
INTACT ROCK SAHPLES m • 7.0 .. - 10.0 .. . 15.0 ... 17.0 m • 25.0
Laborato111 li1f.s sps.cf.nums • - 1.0 ... 1.0 •• 1.0 5 • 1.0 • - 1.0 IN• f>'om joint• A• 0.816 A• 0.918 A• 1.044 A• 1.086 A• 1.220
CSilil r-;;1ting 100 B • 0.658 e - o.677 B • 0.692 B • 0.696 B • 0.705
NGI rating 500 T • ·0. 140 T • ·0.099 T • ·0.067 T • ·0.059 T • -o.040
VERY GOOO QUALITY ROCK MASS .. - 3.5 m • 5.0 m • 7.5 •• 8.5 ... 12. 5 Tightly inter!ooking ""'1is- s - o. 1 5 - 0.1 5 .. 0.1 :!. ... 0.1 ' . 0.1 tw>bed rock IJith """"atlwr- A • 0.651 A• 0.739 A• 0.848 A• 0.883 A• 0.998 sd jt7int.s at •Jm. CSIR rating 85 B • 0.679 B • 0.692 B • 0.702 B • 0.705 e-0.712
NGI rating 100 T • ·0.028 T • -0.020 T • ·0.01) T • -0.012 T • -0.008
GOOD QUALITY ROCK HASS m • 0.1 "' • 1.0 m • 1.5 m • 1.7 .. - 2.5 l're•h to sti!Jhtiy woatlwNd • - 0.004 s • 0.004 ' • 0.004 ' - 0.004 s • O.OO!i reek, • i41htt11 diotw>bed A• 0.)69 A • 0.427 A• 0.501 A• 0.525 lirith Joint• at J ta Jm. A• 0.603 CSlfl r'.;,ting 65 B • 0.669 B • 0.68) B - 0.695 B • 0.698 8. 0.707 NGI ratfrtg 10 T • -0.006 T • ·0.004 T • ·0.003 T • •0.002 T • ·0.002
FAIR QUALITY ROCK HASS m • 0.1 .. m • 0.20 m - 0. 30 .. * o.3i. m •_0.50 Ssvel'tJt oeto of model'<ltel11 I • 0.0001 5 • 0.0001 $ • 0.0001 • - 0.0001 5 • 0.0001 ""atlwl'fld joints •pao•d at A • 0.198 A - 0.2)4 A• 0.280 A • 0.295 A•0.346 O.J to lm. CSIR <atlng 44 B • 0.662 8 • 0.675 I • 0.688 B • 0.691 B•0.700
NGI <otlng 1.0 T • ·0.0007 T • ·0.0005 T • -0.0003 T • ·0.0003 T • -0.0002
POOR QUALITY ROCK HASS m - 0.04 m"" 0.05 "'. 0.08 .. - 0.09 llt • 0.1]
llum«-.. """'th<Nd Join ts •• 0.00001 • - 0.00001 •• 0.00001 I • 0.00001 •• 0.00001 at JO to ~0- IJith •- A• 0.115 A • 0. 129 A • 0.16? A• 0.172 A• 0.20)
""""" . d1'la» ...,.te f'O<>k. CSIR <>ting H B • 0.646 8 - 0.655 8. 0.672 B • 0.676 B • 0.686
NGI <atlng 0.1 T • ·0.0002 T • -0.0002 T • ·0. 0001 T • •0.0001 T • ·0.000I
VERY POOR QUALITY ROCK 1'ASS m • 0.007 m • 0.010 m - 0.015 Ill. 0.017 m • 0.025
""""'"""' hoavH11 ...,athored • • 0 • • 0 • • 0 I • 0 •• 0 Joint. -a • ~- ..ttlt A • 0.042 A • 0.050 A • 0.061 A • 0.065 A - 0.078 11""11• - ..... ts IJith , ......
CSIR <atlng ) I• 0.534 B • 0.539 •• 0.546 B • 0.548 B - 0.556
NGI roting 0.01 T • 0 T • 0 T • 0 T • 0 T - 0
. ---· ··--·~·----·-····-·-·~·---·· ·--····---~ ·-···--- .... ·----+·-----------------~
49 b() Q a;i
Jj m ;I.. cd a;i
.!:I
E1npirical Shear SLrengt.11 Relations Pclona Schist
2 c:J '-
- -· --·· --·--· --· ..
>< f" e u . '_·-_;_
/__ __ [J __ UJtir 1c1lc _ 0
1 5 ' -------··· ' -
1 D
I k>< k 8c [Jr- JWn
Ben 011
__ BCJttQn __ -- --------------+---
IJ) 5
D
Pet:J( ¢-::::35 .. c =.3.5J!sf
Ulfitn.a. = 32c C = /,O f(ef
ltssumed l?esdlkOLJ
¢ =28° c "" 0
I I '··· 10 20 25
Norrnal Stress KSF
1
1
1
** PCSTABL5M ** by
Purdue University
--slope stability Analysis-simplified Janbu, Simplified Bishop
or Spencer·s Method of Slices
Run Date: Time of Run: Run By: Input Data Filename: output Filename:
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
10 Top Boundaries 10 Total Boundaries
1-24-91 7:51 AM CD B: 3775A01.GIN B: 3775A01. POU
SECTION A-A' GROSS STABL - INITIAL EARCH - TOE BELOW FAULT
s
Boundary X-Left Y-Left X-Right Y-Right Soil Type No. (ft) (ft) (ft) (ft) Below Bnd
1 .oo 190.00 130.00 192.00 1 2 130.00 192.00 200.00 210.00 1 3 200.00 210.00 280.00 245.00 1 4 280.00 245.00 400.00 249.00 1 5 400.00 249.00 885.00 440.00 1 6 885.00 440.00 1112.00 500.00 1 7 1112.00 500.00 1240.00 560.00 1 8 1240.00 560.00 2090.00 680.00 1 9 2090.00 680.00 2240.00 710.00 1
10 2240.00 710.00 3000.00 710.00 1
ISOTROPIC SOIL PARAMETERS
1 Type(s) of Soil
Soil Total saturated Cohesion Friction Pore Pressure Piez. Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pcf) (pcf) (psf) (deg) Param. (psf) No.
1 135.0 135.0 500.0 30.0 .oo .o 0
A-·4-.J
/ ---~~~-
1
A Critical Failure Surface Searching Method, Using A Random Technique For Generating Circular Surfaces·, Has Been Specified.
160 Trial Surfaces Have Been Generated.
40 Surfaces Initiate From Each Of 4 Along The Ground Surface Between X =
and X -
Points 80.00
230.00
Equally Spaced ft.
Each Surface Terminates Between and
ft.
x = 800.00 ft. x =3000.00 ft.
Unless Further Limitations Were Imposed, The Minimum Elevation At Which A surface Extends Is Y = .oo ft.
100.00 ft. Line Segments Define Each Trial Failure surface.
Following Are Displayed The Failure Surfaces Examined. First.
Ten Most critical Of The Trial They Are Ordered - Most Critical
* * Safety Factors Are Calculated By The Modified Bishop Method * *
Failure Surface Specified By 14 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 229.89 187.31 3 329.88 188.56 4 429.63 195.73 5 528.77 208.81 6 626.96 227.75 7 723.85 252.47 8 819.11 282.90 9 912.40 318.92
10 1003.38 360.42 11 1091.74 407.24 12 1177.18 459.21 13 1259.37 516.16 14 1331. 76 572.95
Circle Center At X = 259.0 • y = 1870.9 and Radius, 1683.9 '
*** 1.991 ***
Individual data on the 19 slices
Water Water Tie Tie Earthquake Force Force Force Force Force surcharge
Slice Width Weight Top Bot Norm Tan Hor Ver Load No. Ft(m) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg)
1 70.0 100567.6 .o .o .0 .o .o .o .o 2 29.9 115101.5 .o .o .o .o .o .o .0 3 50.1 313974.4 .o .o .o .o .o .o .o 4 49.9 387774.8 .o .o .o .o .o .o .o 5 70.1 537190.3 .o .o .o .0 .0 .0 .o 6 29.6 240625.3 • 0 .o .o .o .o .o .o 7 99.1 ******** .o .o .o .o .o .o .o 8 98.2 ******** .0 .o .o .o .o .o .o 9 96.9 ******** .o • 0 .o .o .o .o .o
10 95.3 ******** .o .o .o .o .o .o • 0 11 65.9 ******** .o • 0 .o .o .o .o . 0 12 27.4 480757.2 .o .o .o • 0 . 0 .o . 0 13 91.0 ******** • 0 .o .o . 0 .o .o . 0 14 88.4 ******** • 0 .o .o . 0 .o .o . 0 15 20.3 229492.2 . 0 . 0 . 0 .o .o .o .o 16 65.2 667742.8 . 0 .o • 0 .o .o • 0 .o 17 62.8 545344.9 . 0 • 0 .o . 0 • 0 • 0 .o
• 18 19.4 135787.8 .o . 0 .o • 0 • 0 • 0 . 0 19 72.4 227552.3 .o . 0 .o • 0 • 0 . 0 • 0
Failure Surface Specified By 11 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 230.00 223.13 2 329.99 221. 77 3 429.82 227.66 4 528.96 240.76 5 626.88 261. 01 6 723.09 288.30 7 817. 06 322.48 8 908.32 363.39 9 996.37 410.79
10 1080.75 464.45 11 1157.06 521.12
Circle Center At X = 298,7 ; Y = 1601.2 and Radius, 1379.8
*** )
1
Failure Surface Specified By 16 Coordinate Points
Point x-surf Y-Surf No. (ft) {ft)
1 130.00 192.00 2 230.00 191.79 3 329.91 196.04 4 429.53 204.73 5 528.67 217.85 6 627.12 235.36 7 724.70 257.25 8 821.20 283.45 9 916.45 313.93
10 1010.24 348,61 11 1102.39 387.44 12 1192.73 430,33 13 1281. 07 477.20 14 1367.23 527.95 15 1451.04 582.49 16 1463.75 591. 59
Circle Center At X - 185.0 ; Y = 2434.1 and Radius, 2242.7
*** 2.017 ***
Failure Surface Specified By 14 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 180.00 204.86 2 279.39 215.92 3 378.37 230.17 4 476.84 247.60 5 574.69 268.19 6 671.84 291.91 7 768 .17 318.75 8 863.59 348.68 9 957.99 381. 66
10 1051. 29 417. 66 11 1143.37 456.64 12 1234.16 498.57 13 1323.55 543.39 14 1394.34 581. 79
Circle Center At X = -112.9 ; Y = 3292,9 and Radius, 3101.9
*** 2.023 *** )
1
A4.4
Failure surface Specified By 12 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 180.00 204.86 2 280.00 205.88 3 379.73 213.21 4 478.79 226.83 5 576.81 246.67 6 673.37 272.67 7 768.10 304.71 8 860.61 342.67 9 950.54 386.40
10 1037.54 435.72 11 1121.24 490.43 12 1171.04 527.68
Circle Center At X = 214.7 ; Y = 1780.9 and Radius, 1576.4
*** 2.029 ***
Failure Surface Specified By 13 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
l 130.00 192.00 2 229.73 184.60 3 329.73 184.72 4 429.44 192.35 5 528.29 207.45 6 625.73 229.93 7 721. 20 259.67 8 814.18 296.50 9 904.12 340.21
10 990.52 390.55 11 1072.90 447.24 12 1150.79 509.96 13 1168.33 526.40
Circle Center At X - 278.2 ; Y = 1513.9 and Radius, 1330.1
• *** 2.048 ***
l
Failure Surface Specified By 12 Coordinate Points
Point x-surf Y-Surf
A4.5
No, (ft) (ft)
1 130.00 192.00 2 229.87 186.82 3 329.83 189.37 4 429.31 199.62 5 527.69 217.51 6 624.41 . 242.93 7 718.87 275.75 8 810.52 315.75 9 898.81 362.70
10 983.22 416.33 11 1063.23 476.31 12 1080.85 491. 77
circle Center At X = 247,4 i y = 1477.6 and Radius, 1290.9
*** 2,049 ***
Failure Surface Specified By 11 Coordinate Points
Point X-Surf '!-Surf No. (ft) (ft)
l 230.00 223.13 2 328.53 206.05 3 428.38 200.62 4 528.19 206.93 5 626.56 224.87 6 722.16 254.21 7 813.67 294.54 8 899.82 345.31 9 979.44 405.82
10 1051. 43 475.23 11 1060.58 486.41
Circle Center At X = 424,6 i Y = 1053.2 and Radius, 852.6
*** 2.061 ***
l
• Failure Surface Specified By 10 Coordinate Points
Point X-Surf 'l-Surf No. (ft) (ft)
l 230.00 223.13 2 328.35 205.05 3 428.18 199.22 4 527.97 205.74
1
•
5 6 7 8 9
10
626.19 721. 36 812.01 896,77 974.35
1038.58
224.51 255.23 297.45 350.51 413.61 480.59
Circle Center At X = 425.4 ; Y = 1008.0 and Radius, 808.8
*** 2,070 ***
Failure Surface Specified By 11 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 228.98 177.76 3 328.89 173.52 4 428.72 179.33 5 527.47 195.13 6 624.12 220.77 7 717.72 255.97 8 807.32 300.39 9 892.00 353.58
10 970.91 415.00 11 1040.09 480.99
circle Center At X = 321.0 ; Y = 1168.6 and Radius, 995.l
*** 2.093 ***
y A x I s F T
.00 375.00 750.00 1125.00 1500.00 1875.00
x .oo +----*----+---------+---------+---------+---------+ . * ..4*
- ..• 12* - •• " • 12
375.00 + ..... 4* ••••• 12 • .•••• 914 ....... 4 .••••• 12 • ........ 54.
A 750.00 ••••... 124
I •
• • • 12 .. ..47.* .312 ..
. 312 .. .. 127
x 1125.00 • • • • • .3.4*6 .31.2 •
• 31* .41 .. .3.4
• • • .3 I 1500.00 +
•
• s 1875.00 +
• •
* ..
2250.00 + *
• F 2625.00 +
T 3000.00 + * ...
l - -·
1
)<
1
1
** PCSTABL5M ** by
Purdue University
--Slope stability Analysis-Simplified Janbu, Simplified Bishop
or Spencer·s Method of Slices
Run Date: Time of Run: Run By: Input Data Filename: output Filename:
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
10 Top Boundaries 10 Total Boundaries
1-24-91 8:07 AM CD B:3775A03.GIN B:3775A03.POU
SECTION A-A' GROSS STABL - INITIAL SEARCH - TOE ABOVE FAULT
Boundary X-Left Y-Left X-Right Y-Right Soil Type No. (ft) (ft)
1 .00 190.00 2 130.00 192.00 3 200.00 210.00 4 280.00 245.00 5 400.00 249.00 6 885.00 440.00 7 1112.00 500.00 8 1240.00 560.00 9 2090.00 680.00
10 2240.00 710.00
ISOTROPIC SOIL PARAMETERS
1 Type(s) of soil
Soil Total Saturated Type unit wt. unit wt.
No. (pcf) (pcf)
1 135.0 135.0
Cohesion Intercept
(psf)
500.0
(ft)
130.00 200.00 280.00 400.00 885.00
1112.00 1240.00 2090.00 2240.00 3000.00
Friction Angle (deg)
30. 0
(ft) Below Bnd
192.00 210.00 245.00 249.00 440.00 500.00 560.00 680.00 710.00 710.00
Pore Pressure
Param.
Pressure Constant
(psf)
.oo .o
1 1 1 1 1 1 1 1 1 1
Piez. Surface
No.
0
1
A Critical Failure surface Searchinq Method, Using A Random Technique For Generating Circular Surfaces, Has Been Specified.
200 Trial surfaces Have Been Generated.
40 surfaces Initiate From Each Of 5 Points Along The Ground Surface Between X m 300.00
and X = 500.00
Equally ft. ft.
Each Surface Terminates Between and
x = 800.00 ft. x -3000.00 ft.
Spaced
_VnJ.ess.'f'urther Limitations Were Imposed, The Minimum Elevation At Which A Surface Extends Is Y = .oo ft.
100.00 ft. Line Segments Define Each Trial Failure Surface.
Followinq Are Displayed The Failure surfaces Examined. First.
Ten Most Critical Of The Trial They Are Ordered - Most Critical
* * Safety Factors Are Calculated By The Modified Bishop Method * *
Failure surface Specified By 8 Coordinate Points
Point x-surf Y-surf No. (ft) (ft)
1 400.00 249.00 2 499.72 256.47 3 598.34 273.06 4 695.01 298.64 5 788,92 332.99 6 879.29 375.81 7 965.34 426.76 8 1040.37 481.07
circle Center At X = 369,2 • y - 1333.5 and Radius, 1085.0 •
*** 1.888 ***
Individual data on the 8 slices
AE1.~
Water Water Tie Tie Earthquake Force Force Force Force Force Surcharge
Slice Width Weight Top Bot Norm Tan Hor Ver Load No. Ft(m) Lbs(kq) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs{kg) Lbs{kg) Lbs(kg)
1 99.7 214090.1 .o .0 .o .o .o .o .o 2 98.6 571488.2 .0 .o .0 .o .o .o .o 3 96.7 786911.l • 0 .o .o .o .o .o .0 4 93.9 860376.3 .o .o .o .o .o .o .o 5 90.4 799754.6 .o .o .0 .o .o .o .o 6 5.7 47317.7 .o .0 .o .o .o .o .o 7 80.3 516686.2 .o .o .o .o .o • 0 .o 8 75.0 174596.6 .o .o .o .o .o .o .o
Failure Surface Specified By 8 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 499.36 260.34 3 597.39 280.09 4 693.38 308.11 5 786.64 344.20 6 876.49 388.10 7 962.28 439.48 8 1008.13 472.55
circle Center At X = 319.l ; Y = 1407.9 and Radius, 1161.8
*** 1.891 ***
1
Failure Surface Specified By 8 Coordinate Points
Point x-surf Y-Surf No. (ft) {ft)
1 350.00 247.33 2 449.82 241.26 3 549.45 249.79 4 646.78 272.76 5 739.72 309.67 6 826.28 359.73 7 904.63 421.87 8 933.75 452.89
circle Center At x = 442.1 ; Y ~ 917.6 and Radius, 676.6
*** 1.893 ***
A5.s
Failure Surface Specified By 11 Coordinate Points
Point x-surf Y-surf No. (ft) (ft)
1 400.00 249.00 2 499.91 253.22 3 599.30 264.27 4 697.70 282.09 5 794.64 306.61 6 889.69 337.71 7 982.38 375.25 8 1072.28 419.04 9 1158.97 468.88
10 1242.05 524,54 11 1298.53 568.26
Circle Center At X = 388.4 ; Y - 1708,9 and Radius, 1459.9
*** 1.904 ***
1
Failure Surface Specified By 7 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 500.00 288.38 2 599.81 294.59 3 697.68 315.10 4 791.58 349.49 5 879.55 397.04 6 959.76 456.76 7 963.85 460.84
Circle Center At X = 507.0 ; y ~ 981.1 and Radius, 692.8
*** 1.942 ***
Failure Surface Specified By 9 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 300.00 245.67 2 399.01 231.62 3 499.0l 230.79
1
1
4 5 6 7 8 9
598.23 694.95 787.46 874.13 953.45
1008.52
243.19 268.60 306.58 356.45 417.35 472.65
Circle Center At X = 455.3 ; Y - 984.1 and Radius, 754.6
*** 1.946 ***
Failure surface Specified By 6 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 500.00 288.38 2 599.95 291.50 3 697.49 313.53 4 789.08 353.68 5 871.39 410.48 6 905.72 445.48
circle Center At X = 535.2 ; Y = 799.9 and Radius, 512.8
*** 1.954 ***
Failure Surface Specified By 7 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 499.04 235.15 3 598.78 242.27 4 694.84 270.05 5 782.99 317.28 6 859.34 381.86 7 909.28 446.42
Circle center At X - 515.2 : Y = 711.3 and Radius, 476.5
*** 1.966 *** ) I I
..
1
Failure Surface Specified By 8 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 350.00 247.33 2 448.52 230.21 3 548.49 232.90 4 645.95 255.29 5 737.07 296.49 6 818.24 354.89 7 886.28 428.18 8 895.16 442.69
Circle Center At X = 485.2 ; y = 728.5 and Radius, 499.8
*** 1.967 ***
Failure Surface Specified By 8 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 350.00 247.33 2 448.12 228.05 3 548.ll 229.37 4 645.69 251. 25 5 736.67 292.76 6 817.16 352.10 7 883.71 426.74 8 892.44 441.97
Circle Center At X = 491.8 ; y = 705.3 and Radius, 479.5
*** 1.987 ***
y A x I s F T
.00 375.00 750.00 1125.00 1500.00 1875.00
x .00 +----·----+---------+---------+---------+---------+ * * * 6
375.00 + .6* .•• 3.
T 3000.00 + *
1
1
1
** PCSTABL5M ** by
Purdue University
--Slope stability Analysis-Simplified Janbu, Simplified Bishop
or Spencer·s Method of Slices
Run Date: Time of Run: Run By: Input Data Filename: Output Filename:
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
10 Top Boundaries 10 Total Boundaries
1-24-91 8:28 AM CD B:3775A07.GIN B:3775A07.POU
SECTION A-A' GROSS STABL - DETAILED SEARCH - TOE BELOW FAULT
Boundary X-Left Y-Left X-Right Y-Right Soil Type No. (ft) (ft)
1 .oo 190.00 2 130.00 192.00 3 200.00 210.00 4 280.00 245.00 5 400.00 249.00 6 885.00 440.00 7 1112.00 500.00 8 1240.00 560.00 9 2090.00 680.00
10 2240.00 710.00
ISOTROPIC SOIL PARAMETERS
1 Type(s) of Soil
Soil Total Saturated Type Unit Wt, Unit Wt.
No. (pcf) (pcf)
1 135.0 135.0
cohesion Intercept
(psf)
500.0
(ft)
130.00 200.00 280.00 400.00 885.00
1112.00 1240.00 2090.00 2240.00 3000.00
Friction Angle (deg)
30.0
(ft) Below Bnd
192.00 210.00 245,00 249.00 440.00 500.00 560.00 680.00 710.00 710.00
Pore Pressure
Param.
Pressure Constant
(psf)
.oo .o
l 1 1 l 1 1 1 1 1 l
Piez. Surf ace
No,
0
1
A Critical Failure Surface Searching Method, Using A Random Technique For Generating Circular Surfaces, Has Been Specified.
200 Trial surfaces Have Been Generated.
200 Surfaces Initiate From Each Of 1 Points Equally Spaced Along The Ground Surface Between X - 130.00 ft.
· and X = 130.00 ft.
Each surf ace Terminates Between and
x .. 800.00 ft. x -1500.00 ft.
Unless Further Limitations Were Imposed, The Minimum Elevation At Which A Surface Extends Is Y = .oo ft.
100.00 ft. Line Segments Define Each Trial Failure Surface.
Following Are Displayed The Failure Surfaces Examined. First.
Ten Most Critical Of The Trial They Are Ordered - Most Critical
* * Safety Factors Are Calculated By The Modified Bishop Method * *
Failure surface Specified By 14 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 230.00 191. 71 3 329.86 196.91 4 429.29 207.58 5 527.99 223.69 6 625.65 245.19 7 721.98 272.01 8 816.70 304.09 9 909.52 341.31
10 1000.15 383.57 11 1088,32 430.74 12 1173.78 482.67 13 1256.26 539.22 14 1292.98 567.48
circle Center At X = 186;:1; • y--= 2007.2 and Radius, 1816.0 •
*** 1.990 ***
Individual data on the 19 slices
Water water Tie Tie Earthquake Force Force Force Force Force surcharge
Slice Width Weight Top Bot Norm Tan Hor Ver Load No. Ft(m) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs (kg) Lbs(kg) Lbs(kg)
l 70.0 86008.4 .o .o .o .o .0 .o .o 2 30.0 100476.7 .0 .o .o .o .o .o .o 3 50.0 277096.6 .o .o .o .o .o .o .o 4 49.9 338077.2 .o .o .o .o .o .o .0 5 70.l 446527.2 .0 .o .o .o .o .o .o 6 29.3 192842.6 .o .o .o .o .o .o ,0 7 98.7 857221.4 .o .o .0 .o .0 .o . 0 8 97.7 ******** .o .o .o .o .o .o .o 9 96.3 •••••••• .o .o .o .o .o .o .o
10 94.7 ............ .o • 0 .o .o .o .0 • 0 11 68.3 ******** .o .o .o .o .o .o .o 12 24.5 353610.9 . 0 .o .o .o .o .o • 0 13 90,6 ******** .o .o .o .o .o .o . 0 14 88.2 892028.6 .o .o . 0 .o .o . 0 • 0 15 23.7 188386.4 .o .o .o .o .o .o .o 16 61.8 421850.7 .o .o .0 .o .o .o .o 17 66.2 349600.4 .o • 0 .0 .o .0 .o .o 18 16.3 60354.3 . 0 .o .o .o .o .o .o 19 36.7 57198.5 . 0 .o .o .o .o • 0 • 0
Failure Surf ace Specified By 15 Coordinate Points
Point x-surf ¥-Surf No, (ft) (ft)
l 130.00 192.00 2 229.99 193.36 3 329.81 199.34 4 429.25 209.93 5 528.09 225.10 6 626.13 244.82 7 723.15 269.05 8 818.95 297.74 9 913.31 330.82
10 1006.05 368.23 11 1096.96 409.89 12 1185.85 455.70 13 1272.53 505.58 14 1356.81 559.40 15 1387.07 580.76
Circle Center At X = 150,6 • y = 2355.2 and Radius, 2163.3 •
..... 1.990 ***
A6.3
J.
Failure Surface Specified By 14 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 229.88 187.19 3 329.87 188.60 4 429.58 196.23 5 528.63 210.04 6 626.62 229.98 7 723.18 255.97 8 817.94 287.92 9 910.53 325.70
10 1000.59 369.17 11 1087.77 418.15 12 1171.74 472.45 13 1252.17 531.87 14 1294.90 567.75
Circle Center At x = 257.7 ; Y = 1789.5 and Radius, 1602.6
*** 1.995 ***
Failure Surface Specified By 14 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 229.73 199.33 3 329.07 210.80 4 427.85 226.38 5 525.90 246.04 6 623.04 269.76 7 719.12 297.50 8 813.96 329.19 9 907.41 364.80
10 999.30 404.26 11 1089.47 447.50 12 1177.76 494.44 13 1264.04 545.0l 14 1300.65 568.56
Circle Center At X = 4.7 ; y = 2589,6 and Radius, 2400.9
*** 2.011 ***
1
Failure surface Specified By 15 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 229.53 201.68 3 328.68 214.70 4 427.33 231.05 5 525.38 250.71 6 622.71 273.66 7 719.22 299.87 8 814.78 329.32 9 909.30 361.97
10 1002.67 397.78 11 1094.78 436.71 12 1185.53 478.72 13 1274.81 523.76 14 1362.53 571. 78 15 1374.77 579.03
Circle Center At X = -107.6 1 Y = 3153.1 and Radius, 2970.6
*** 2.018 ***
Failure surface Specified By 16 Coordinate Points
Point x-surf Y-surf No. (ft) (ft)
1 130.00 192.00 2 230.00 192.09 3 329.90 196.49 4 429.52 205.20 5 528.68 218.20 6 627.17 235.46 7 724.84 256.95 8 821.48 282.64 9 916.93 312.47
10 1011.00 346.39 11 1103.52 384.33 12 1194.32 426.24 13 1283.22 472.02 14 1370.07 521.59 15 1454.70 574.86 16 1482.79 594.28
Circle Center At X = 178.6 : y = 2504.3 and Radius, 2312.8
*** 2.026 ***
1
Failure Surface Specified By 15 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 229.62 183.25 3 329.58 180.39 4 429.53 183.43 5 529.13 192.37 6 628.03 207.16 7 725.89 227.76 8 822.35 254.09 9 917.10 286.07
10 1009.80 323.59 11 1100.12 366.50 12 1187.76 414.67
--13 1272.40 467.93 14 1353.75 526.08 15 1428.69 586.64
circle Center At X = 328.0 ; Y = 1875.0 and Radius, 1694.6
*** 2.026 ***
Failure Surface Specified By 15 Coordinate Points
Point x-surf Y-Surf NO. (ft) (ft)
1 130.00 192.00 2 229.34 203.51 3 328.27 218.08 4 426.70 235.70 5 524.55 256.35 6 621. 71 280.02 7 718.09 306.68 8 813.60 336.30 9 908.15 368.86
10 1001.65 404.33 11 1094.01 442.66 12 1185.14 483.83 13 1274.96 527.80 14 1363.37 574.52 15 1370.14 578.37
circle Center At X - -192.7 : Y ~ 3412.2 and Radius, 3236.3
*** 2.035 ***
l}G.t ~ - ·-··· -·~ -
1
Failure surface Specified By 16 coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 229.60 200.97 3 328.87 213.00 4 427.73 228 •. 09 5 526.07 246.23 6 623.80 267.39 1 720.84 291. 56 8 817.08 318.71 9 912.44 348.82
10 1006.83 381. 86 11 1100.15 417. 79 12 1192.31 456.59 i:r 1283.24 498.21 14 1372.84 542.62 15 1461. 02 589.77 16 1464.33 591.67
Circle Center At X = -110.4 ; Y = 3421.9 and Radius, 3238.9
*** 2.038 ***
Failure surface Specified By 13 Coordinate Points
Point x-surf Y-surf No. (ft) (ft)
1 130.00 192.00 2 229.86 186.70 3 329.84 188.49 4 429.45 197.37 5 528.18 213.28 6 625.53 236.14 1 721. 01 265.85 8 814 .15 302.25 9 904.48 345.16
10 991.53 394.37 11 1074.89 449.62 12 1154.11 510.63 13 1175.73 529.88
Circle Center At X - 254.6 : Y = 1596.6 and Radius, 1410.2
*** 2.041 ***
' .
1
..
y A x I s F T
.oo 375.00 750.00 1125.00 1500.00 1875.00
x .oo +----·----+---------+---------+---------+---------+ * . . *
.1. * - •.• 14
375.00 +.. * - ••• 31 • ••..• 714 • • • • - ..... 31 . • • • • • ... . . 8 .
A 750.00 +, •••• 714 .. . . . . • • • 714 .. - ........ 0 . • *
..... 614 . . - •..••.. 614 . .
. . . . . • • • 14 • x 1125.00 + ••••• 625*0
•••.... 6210 ...... 721*
...•• 6 .1 .••. 62 .
• • • 67 I 1500.00 + •• 6
s 1875.00 +
2250.00 +
F 2625.00 +
T 3000.00 +
*
*
*
. - ...
1
1
l
** PCSTABL5M ** by
Purdue University
--Slope Stability Analysis-simplified Janbu, Simplified Bishop
or Spencer"s Method of Slices
Run Date: Time Of Run: Run By: Input Data Filename: Output Filename:
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
10 Top Boundaries 10 Total Boundaries
1-24-91 8:36 AM CD B:3775A08.GIN B:3775A08.POU
SECTION A-A' GROSS STABL - DETAILED SEARCH - TOE ABOVE FAULT
Boundary X-Left Y-Left X-Right Y-Right Soil Type No. (ft) (ft)
1 .oo 190.00 2 130.00 192.00 3 200.00 210.00 4 280.00 245.00 5 400.00 249.00 6 885.00 440.00 7 1112.00 500.00 8 1240.00 560.00 9 2090.00 680.00
10 2240.00 710.00
ISOTROPIC SOIL PARAMETERS
l Type(s) of Soil
Soil Total Saturated Type Unit wt. Unit wt.
No. (pcf) (pcf)
1 135.0 135.0
Cohesion Intercept
(psf)
500.0
(ft)
130.00 200.00 280.00 400.00 885.00
1112.00 1240.00 2090.00 2240.00 3000.00
Friction Angle (deg)
30.0
(ft) Below Bnd
192.00 210.00 245.00 249.00 440.00 500.00 560.00 680.00 710.00 710.00
Pore Pressure
Param.
Pressure Constant
(psf)
.oo .o
1 1 l l 1 l 1 1 l 1
Piez. Surf ace
No.
0
•
1
A Critical Failure Surface Searching Method, Using A Random Technique For Generating circular Surfaces, Has Been Specified.
200 Trial Surfaces Have Been Generated.
200 Surfaces Initiate From Each Of Alonq The Ground Surface Between X
and X
1 Points = 400.00 .. 400.00
Equally ft. ft •
Each Surf ace Terminates Between and
x = 800.00 ft. x -1500.00 ft.
Spaced
Unless Further Limitations Were Imposed, The Minimum Elevation At Which A Surface Extends ls Y = .oo ft.
100.00 ft. Line Seqments Define Each Trial Failure Surface.
Following Are Displayed The Failure Surfaces Examined. First.
Ten Most Critical Of The Trial They Are Ordered - Most Critical
* * Safety Factors Are Calculated By The Modified Bishop Method * *
Failure surface Specified By 8 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 499.81 255.21 3 598.20 273.07 4 693.82 302.35 5 785.34 342.63 6 871.52 393.37 7 951.15 453.86 8 956.32 458.85
circle Center At X = 397.7 : Y - 1097.4 and Radius, 848.4
Individual data on the 8 slices
Water Water Tie Tie Earthquake Force Force Force Force Force Surcharge
Slice Width Weight Top Bot Norm Tan Hor Ver Load No. Ft(m) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg) Lbs(kg)
1 99,8 222986.6 ,0 .0 .o .o .o .o .0 2 98.4 578338.8 .o .o .o .o .o .0 .o 3 95.6 750902.0 .0 .o .o .o .o .o .o 4 91.5 744334.9 .o .o .o .o .o .o .o 5 86.2 578396.9 .o .o .o .o .o .o .o 6 13.5 70722.4 .o .o .o .o .o .o .o 7 66.1 178626.0 .o .o .o .o .o .o .o 8 5.2 1265.0 .o .o .o .o .o .o . 0
Failure Surface Specified By 8 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 499.72 256.47 3 598.02 274.81 4 693.73 303.82 5 785.67 343.13 6 872.76 392.28 7 953.94 450.68 8 965.79 461. 35
Circle Center At X = 383.1 ; y = 1154.0 and Radius, 905.1 •
• •• 1.870 •••
1
Failure Surface Specified By 7 Coordinate Points
Point x-surf Y-surf No. (ft) (ft)
1 400.00 249.00 2 499.77 255.86 3 597.98 274.69 4 693.20 305.22 5 784.05 347.01 6 869.21 399.44 7 937.56 453.89
circle Center At X = 393.2 ; y = 1077.2 and Radius, 828.2
••• 1.871 •••
l
Failure Surface Specified By 7 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 499.91 253.36 3 598.27 271.37 4 693.24 302.70 5 783.01 346.74 6 865.90 402 .69 7 916.89 448.43
Circle Center At X = 418.3 • y = 976.5 and Radius, I
*** 1.873 ***
Failure surface Specified By 8 Coordinate Points
Point X-Surf Y-surf No. (ft) (ft)
1 400.00 249.00 ·2 499.72 256.42
3 598.26 273.45 4 694.70 299.92 5 788.12 335.59 6 877.65 380.13 7 962.46 433.12 8 1016.72 474.82
Circle Center At X = 374.9 ; y - 1272.7 and Radius,
*** 1.880 ***
Failure surface Specified By 7 Coordinate Points
Point No.
1 2 3 4 5 6 7
X-Surf (ft)
400.00 499.36 597.09 692.22 783.82 870.96 950.30
Y-Surf (ft)
249.00 260.34 281.52 312.33 352.46 401. 51 457.26
727.7
1024.0
..
circle Center At x = 336.l ; Y - 1249.6 and Radius, 1002.7
*** 1.887 ***
l
Failure Surface Specified By 8 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 499.36 260.29 3 597.35 280.25 4 693.21 308.73 5 786.20 345.51 6 875.60 390.31 7 960.74 442.77 8 996.65 469.51
circle Center At X = 323.8 ; y = 1372.8 and Radius, 1126.3
*** 1.888 ***
Failure Surface Specified By 8 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 499.98 247.12 3 599.38 258.09 4 696.55 281. 71 5 789.89 317.60 6 877.85 365.16 7 958.99 423.61 8 1012.42 473.68
circle Center At x = 465.2 : Y = 1018.2 and Radius, 771.9
• *** 1.890 ***
l
Failure Surface specified By 9 coordinate Points
·. .. Point x-surf Y-surt
No. (ft) (ft)
1 400.00 249.00 2 499.91 253.22 3 598.97 266.91 4 696.28 289.94 5 790.96 322.12 6 882.16 363.14 7 969.05 412. 64 8 1050.85 470.16 9 1073.96 489.94
circle Center At x = 405.6 ; Y - 1300.7 and Radius, 1051.7
*** 1.899 ***
Failure Surface Specified By 9 Coordinate Points
Point x-surf Y-Surf No. (ft) (ft)
1 400.00 249.00 2 500.00 248.91 3 599.39 259.90 4 696.96 281. 85
• 5 791.48 314.47 6 881. 81 357.38 7 966.82 410.04 8 1045.47 471.80 9 1060.26 486.32
circle Center At X = 450.8 ; Y ~ 1148.1 and Radius, 900.5
*** 1.901 ***
1
y A x s F T
.00 375.00 750.00 1125.00 1500.00 1875.00
• x .oo +----*----+---------+---------+---------+---------+ * * *
375.00 + * •• 1
••
• • • • • • .16
• • • .1 • A 750.00 +. • •
• • • 81. .13*
• • .81 .·91111 5
• • • .9 x 1125.00 + • • * •
• • • • • • • *
• • • • • • •
I 1500.00 + •
s 1875.00 +
*
2250.00 + *
•
F 2625.00 +
T 3000.00 + * ....
•
•
l
•
1
•
** PCSTABL5M ** by
Purdue University
--Slope stability Analysis-Simplified Janbu, Simplified Bishop
or Spencer's Method of Slices
Run Date: Time of Run: Run By: Input Data Filename: output Filename:
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
10 Top Boundaries 10 Total Boundaries
2-1-91 10:52 am CD a:3775a30.in a:3775a30.out
SECTION A-A' GROSS STABL - SEISMIC
Boundary X-Left Y-Left X-Right Y-Right Soil Type No. (ft) (ft)
1 .00 190.00 2 130.00 192.00 3 200.00 210.00 4 280.00 245.00 5 400.00 249.00 6 885.00 440.00 7 1112.00 500.00 8 1240.00 560.00 9 2090.00 680.00
10 2240.00 710.00
ISOTROPIC SOIL PARAMETERS
l Type(s) of Soil
Soil Type
No.
1
Total Saturated unit wt. unit wt.
(pcf) (pcf)
135.0 135.0
Cohesion Intercept
(psf)
3000.0
(ft)
130.00 200.00 280.00 400.00 885.00
1112.00 1240.00 2090.00 2240.00 3000.00
Friction Angle (deg)
35.0
(ft) Below Bnd
192.00 210.00 245.00 249.00 440.00 500.00 560.00 680.00 710.00 710.00
Pore Pressure
Param.
Pressure Constant
(psf)
.oo .o
1 1 1 l 1 1 1 1 1 1
Piez. surf ace
No.
0
•
1
•
l
•
A Horizontal Earthquake Loading Coefficient Of .soo Has Been Assigned
A Vertical Earthquake Loading Coefficient Of .250 Has Been Assigned
Cavitation Pressure = .o psf
Trial Failure Surface Specified By 14 Coordinate Points
Point X-Surf Y-Surf No. (ft) (ft)
1 130.00 192.00 2 230.00 191.71 3 329.86 196.91 4 429.29 207.58 5 527.99 223.69 6 625.65 245.19 7 721.98 272.01 8 816.70 304.09 9 909.52 341. 31
10 1000.15 383.57 11 1088.32 430.74 12 1173.78 482.67 13 1256.26 539.22 14 1292.98 567.48
Circle Center At X = 186.1 ; y - 2007.1 and Radius, 1816.0
Factor Of Safety For The Preceding Specified Surface = 1.100
WARNING - Factor Of Safety Is Calculated By The Modified Bishop Method. This Method Is Valid Only If The Failure Surface Approximates A Circle.
x
.Y A x I s F T
.00 375.00 750.00 1125.00 1500.00 1875.00
.00 +----*----+---------+---------+---------+---------+
375.00 +
* *
s * s
s s *
s
A 750.00 + s s
* s s s
x 1125.00 + * s
S* s
I 1500.00 +
s 1875.00 +
*
2250.00 + *
• F 2625.00 +
T 3000.00 + * 1
Trial Failure Surface Specified By 8 Coordinate Points
Point x-surf Y-Surf No • (ft) (ft)
• 1 400.00 249.00 2 499.81 255.21
• 3 598.20 273.07 4 693.82 302.35 5 785.34 342.63 6 871.52 393.37 7 951.15 453.86 8 956.32 458.85
Circle Center At X = 397.7 : y = 1097.4 and Radius, 848.4
ft/313
1
•
•
•
Factor Of Safety For The Preceding Specified Surface = 1.367
WARNING - Factor Of Safety Is Calculated By The Modified Bishop Method. This Method Is Valid Only If The Failure Surface Approximates A Circle.
y A x I s F T
.00 375.00 750.00 1125.00 1500.00 1875.00
x .00 +----*----+---------+---------+---------+---------+ * * *
375.00 + *
A 750.00 +
x 1125.00 +
I 1500.00 +
s 1875.00 +
2250.00 +
F 2625.00 +
s
s s
s s *
s
* *
*
*
I i .;
I • •
T 3000.00 +
•
,
' ' OVERSIZED -~·
DOCUMENT HAS BEEN PULLED AND SCANNED WITH THE MAP
FILE.
. - . . '
. ,' ·'· ~'' .
--Since 1956
RSA Associates, Inc.
Corporal!;' ()ffi(E": 15414 (Jbrito Rodd, Umr A, Van Nuy~, CA 91401) • (81 BJ 989-53.18 • 26545·82 Feliii:. V.:ildc.z Avenue, R:anchaCaliforniJ, CA 91390 • !71 4! b7b-8JB2
September 18, 1991
The Old Wrightwood Ranch, Inc. c/o Spindler Engineering 7120 Hayvenhurst Avenue, Ste. 200 Van Nuys, CA 91406
Attention: Mr. Larry Gray
Subject: DEBRIS FLOW Lots 1, 2 and 3, Tract 45783 Wrightwood Area Los Angeles County, California
Dear Mr. Gray:
Job No.: 3775-05 Log No.: 18677
On August 6, 1991, we prepared a response to concerns raised in the Los Angeles County Geotechnical Review Sheet dated June 19, 1991. In that response, we stated that debris would be diverted to the private driveways.
The total distance from the slough walls to the private driveway and then to the County road (Logwood Drive) varies from 400 to 600 feet. Therefore, it is our opinion that a possible debris flow will not adversely affect the County road.
If you have any questions concerning this letter, please do not hesitate to contact this office.
Very truly yours, RSA ASSOCIATES, INC.
- -
Edward Barton, R.G.E.
EB:el
Distribution: (6) The Old Wrightwood Ranch, Inc.
Engineering Geology• Soil Engineering• Material Testing
Since 1956 RSA Associates, Inc.
Corporitlt' Office; 15414 Cabrilo Rucld, Ul"lil A, Van Nuys, CA 9140b •(618) qgq_5335 • l6S45-B:! Felix Valdi?.l AveruJe. Rancho California, CA 92390• l7 l 4J676-8l82
August 22 1 1991 Job No.: 3775-05 Log No.:_ 18616
\~~ L~~~ ~ ~~ ® ·, . SE? G ~ '991 The Old Wrightwood Ranch, Inc.
c/o Spindler Engineering 7120 Hayvenhurst Avenue, Ste. 200 Van Nuys, CA 91406
Attention: Mr. Larry G. Gray
PROCtti~11111.:i 1.itNll:R Lf\NO OE.V. Q\V.
Subject: RESPONSE TO COUNTY GEOTECHNICAL ENGINEERING REVIEW LETTER DATED JUNE 19, 1991 AND COUNTY GEOLOGIC REVIEW LETTER DATED JUNE 26, 1991 Lots 1, 2 and 3, Tract 45783 (formerly a part of Tract 41777) Wrightwood Area Los Angeles County, California
Dear Mr. Gray:
The following are our responses to questions raised in the
Los Angeles county Geotechnical Engineering Review Sheet
dated June 19, 1991 and the Los Angeles Geologic Review Sheet
dated June 26, 1991,
L.A. COUNTY GEOTECHNICAL ENGINEERING:
1. As previously requested, show the following on the
geotechnical map.
a. Existing and proposed grades.
b. The area and overexcavation depth required for
soils subject to hydroconsolidation and for
slopewash and alluvial material.
c. Location of private sewage disposal system.
d. Restricted Use Area.
Engineering Geology• Soil Engineering• Material Testing
The Old Wrightwood Ranch, Inc. August 22, 1991
Job No.: 3775-05 Log No.: 18616 Page 2
RSA:
The Geologic Map dated August 8, 1991 is attached.
a. The existing grades and the proposed grades for the
private driveways are shown on the map. The exact
locations and grades of the houses has not, to our
knowledge, been determined.
b. As noted in the report, the site is mantled with
three feet or less of topsoil. In our report dated
January 4, 1988 we recommended that the existing
topsoil, slopewash and weathered bedrock within the
proposed development areas should be removed and
recompacted. The area of removal shal1 extend
beyond the edge of footing at least 3 feet or equal
to the depth of removal, whichever is greater.
When the building sites are determined, a grading
plan showing the extent of removal and recompaction
should be prepared.
c. The approximate limits of possible disposal areas
has been transferred from our Plot Plan which
accompanied our report dated July 13, 1988 to the
attached Geologic Map.
d. The restricted use area is shown on the attached
Geologic Map.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 22, 1991
Job No.: 3775-05 Log No.: 18616 Page 3
L.A. COUNTY GEOTECHNICAL ENGINEERING:
2, Debris flow may not be directed into street right of
way. Recommend appropriate mitigation. If the debris
flow is contained by slough walls, then recommend
catchment area to accommodate the debris flow.
RSA:
As noted in our letter dated January 31, 1991, the
volume of debris was computed to be 928 cubic yards and
would be diverted to the private driveways. If this
volume were evenly distributed, the depth of the debris
would be two feet or less.
•• L.A. COUNTY GEOTECHNICAL ENGINEERING: ••
3. Please include a copy of this [.eview sheet with your
response. •
RSA:
Comply.
L.A. COUNTY GEOLOGY:
1. Please provide a response to item 2 of previous geologic
review sheet dated 10/25/90.
RSA Associates, Inc.
The Old Wrightwood Ranch, Inc. August 22, 1991
RSA:
See answer to No. 1 above.
2. L.A. COUNTY GEOLOGY:
Job No.: 3775-05 Log No.: 18616 Page 4
The geotechnical Engineering Unit's requirements are
attached (review is dated 6/19/91).
RSA:
Comply.
This opportunity to be of service
If you have any questions
not hesitate to co ii .,.!his off· ':? 1·,;'.-' / , '
.. ~ ...... ·-.'!-
1242
EB/KWE:el
Enclosures: Geologic Map Copy of Geotechnical Engineering Review Sheet, dated June 19, 1991 and Geologic Review Sheet dated June 26, 1991
Distribution: (6) The Old Wrightwood Ranch, Inc.
RSA Associates, Inc.
...., 1..1' .... - .... ~ • - - -
~~~of.L STATUS CHEO:S (818) 4$!·4032
clEOLOOIC RliVl~ $H(ET • •. I
•'' Arl;•ln County Oeplrtatnt of P~bl I~ ~- .s 900 So, Fro=nt Avo., Alhani>r1, CA OlllOl
KA.TE.RIALS fl«llHEERll«l PIVIS!OH Tl!.. (Ill) 458·49<3
Tr"t/PM _ __,y""'s ..... -..-;2.,,.11-Hl,_,_____ Lot(S) , _ 1 Par&nt Tr11ct --~ ....... tt ... 2 ... 2..,_ ____ Location iJ'1144.,.,.n;i SI tt AddrtU -~-...l'r"'il ....... -----:--.-~-.,.....~..-t"""'.-r-""'"°"n--Gto l og1 st Devoloper/owner ""'"' Ctottchftlc-=i1~e~ng-:-:1-ne-or_.-=-=-=,..,..,,..T""-- Englnear/Arcll. -· -~...._......._....._ __ _
Revlw af1 :!:!: Gradlnt P.O. Ho. 121r - B~!tdlng P.C. Ho. Fon
Dl$t. Ottlco °2',.)
F k "'--
0 ISTa !BUTI OH
..1. Olstrlct Offlc•
...1.. Ctologlst ~ G.otechnlcal Eng. 1 S"tlon fl le
.J... Gradlng S.ctloh
...1.. Englneer/Developtr
_ Gte1og1c ~~rt(1) Oited --...,...,_.-..,,.....-------------------Goot8'1\nlcal Enslnttr1na l'PQrt(a) Dtt.td _____ ,........,. _ _,....,...., ......... -..,_-.._...._ ______ _ ~Geology Ind Gtohchnlcal Ensln .. r!ng Report(s) Dltld 1:?1-1~. f·2-frf'0: z-/; ... 12;: 1- ~-BB
Action: _ Plin II geol091Qll)' lpprovod. k_ PIM II not '!'PfllVecl for r ... sans below. _ Plan 15*roved 9eologleal1)' •\lb.J•d ? st2141T PLAHS fat RECHECK. IDt;lYd• a copy
't4 condlt1ons below, af thb rey!e. SKtlon 300 Code Rl1J1trutnt >»» _ Met _ llot Mot
Ro1urku ·1,.. Plwt... fGY~J.t- .;;.. Cf.f(?i:M.J.f. i-u ~HM g,, c?f. ivcr"'~""'J
8 ur~, l (.,, c, \Ile...., .!'/.re•f 4.f..l. ,t.) .. a.,e.. B2,
""''"'"-'"--F7\__.;t-;;;;...._....G:"'u='t ... AA4="--7..,ce.aoC~-F:.::" .. ~t~J ":;..:H=:..n.!.J~=.---:0U~11~).J.f~\:..-._._f t:;fi,...V~i~r.:;..ti;::;,M,>.;i-f:.!!.i:.i..,fs~..::"'i.:;.,.4-.=---a~'.,J Crev~fW l.r J.p.f~ 6 .. 1,-11 ) ..
Propar.cl b)' tfli a Q2=0l •8-®3ZA
Rtvt""9d1>1 ___ ~------D&t1 {i/.k'lt . •'
( ll'!Dl
- t..· (( It.
GEOTECHNICAL ENGINEERING REVlflr/ SHEET
COUNTY OF LOS ANGELES Addre$s: 900 So. Fremont Ave. DEPARTMENT Of PUBLIC WORKS
Alhambra, CA 91803 Telephone: (816) 450~4926 Materials Engineering Div1s1on
UnBraded· S1te lots Tract 45783 Parent ~77 __ Location ~oOd Dr1v~htwood Deve1oper/~r 91~ Rffoh~od ·Ranch; Inc. Engineer S~1ndter ng neer JS cor~ Gaotechn1ca Engineer RSA ( .R. 3 ?s~o31 Geo10911t Same as above
Grading Plan Check No. 3968
Revtew of:
D1itrlct Off1ee e.o -Sheet 1 of l
DISTRIBUTION:
Drainage and Grading sect. ~Geo/Soils Central File ~ D1str1ct Engineer = Geolog1 st
Geotechn1cal Engineer - Engineer -
Geotechnical Report dated 1/31/91
Action:
Geo1og1c Report dated 1/31/91
Before approval for feas1b111ty the fo1tow1ng lnfonnatlon is required to assess the development 1$ $hown on the tentative map:
Remarks:
1, As prev1ous1y requested, show the following on the geotechn1ca1 map:
_1. ·Existing and proposed grades. b. The area and overexcavat1on depth required for soils subject to hydroconso1tdat1on . and for slope wuh and a11uv1a1 material. ' c. 'Location of private aewage disposal system. d. · Rutrfcttd Use Area. -
2. Debris flow may not be directed Into 1treet right of way. Recomnend appropriate mltJgation. If the debris flow is contained by $lOugh walls, then reconrnend catchment area to accomnodate the debris now.
·r 3. Please Include a cop,v of thU review sheet w1th you response • . ,
Date 6119/91
, Ok1ah Alhayek C:45783~