minnesota department of transportation office of materials & … · 2015. 11. 30. · design...

Minnesota Department of Transportation Office of Materials & Road Research 1400 Gervais Avenue Maplewood, MN 55109

Memo TO: Josie Tayse, Final Design Project Manager

Metro District, Waters Edge

FROM: Paul Martin, Assistant Foundations Engineer Geotechnical Engineering Section

Concur: Rich Lamb, Foundations Design Build Engineer

Geotechnical Engineering Section

DATE: November 3, 2015

SUBJECT: SP 7005-105, TH 169 From Scott CSAH 14 to Old Shakopee Rd Overhead Sign Foundation Recommendations

1.0 Project Summary This report is provided in response to a request by the Metro District to provide a subsurface investigation and foundation recommendations for overhead sign structures being reconstructed along TH 169 as part of a sign replacement project. The sign structure types will include both Sign Bridge and Cantilever. Each sign structure will be supported with either spread footings or drilled shaft foundations.

2.0 Subsurface Investigation A review of available documents indicated the soil conditions could be variable and that bedrock might be encountered by drilled shaft foundations. The soils at the proposed sign locations were investigated using Cone Penetration Test (CPT) Soundings on August 17, 2015 and a Penetration Test soil boring (SPT) at a location near where one of the CPT soundings encountered refusal. The CPT soundings were interpreted for general soil behavior type. No soil samples were taken so the interpreted soil behavior type may not exactly match what soil is present, but should indicate how it behaves if compared to standard soils. Based on the results of the investigation, we determined that the foundation soils in the area generally consist of mostly loose to very dense sand and loamy sand with some layers of sandy loam below ten feet and scattered thin layers of silt at depth. The CPTs met refusal at depths shallower than the typical drilled shaft foundation at the locations of OH 121-169 and OH 119-169. The boring encountered dolostone bedrock at a depth of 29 feet at the location of OH 119-169.

Groundwater was detected in some of the CPT soundings and measured in the SPT boring at a depth of about 12 feet. Perched water should also be expected in areas where layered soils exist. Please refer to the attached sounding and boring logs for the most complete description of the foundation soils. Table 1, below, provides a summary of the soil and groundwater conditions encountered.

1 of 3 An Equal Opportunity Employer

Paul S Martin

SP 7005‐105 TH 169 Overhead Signs Foundation Recommendations

November 3, 2015

Table 1, Summary of Estimated Soil and Groundwater Conditions Sounding

# Sign ID Exploration Location

GroundwaterDepth (feet) Summary of Interpreted Soils

InterpretedN‐Value

T01 OH 119‐169 N 213533.2 E 467921.8 Measured 11.9’ Sands to bedrock at 29’ 8‐50+

c‐01 OH 122‐169 N 213615.6 E 469716.5 ‐‐*

Sands to 18’, Sandy Loam to 22’, then Sand. 7‐50+

c‐02 OH 121‐169 N 213617.2 E 468632.4 ‐‐*

Sands to 10’, then layered Sandy Loam and Sand. Refusal at 26’ 7‐50+

c‐03 OH 119‐169 N 213504.8 E 467928.9 ‐‐ Primarily Sands, Refusal at 10’ 12‐50+

c‐04 OH 119‐169 N 213455.2 E 467926.7 ‐‐

Layered Sands and Sandy Loam, Refusal at 27’ 22‐50+

*Perched groundwater layers may occur 3.0 Existing Signs According to the SP 7005-69 plans, existing sign bridge OH 119-169 is currently supported on drilled shafts extending 8 ½ to 9 ½ feet below the surface, existing cantilever OH121-169 is on 5’ to 6 ½-foot shafts, and existing cantilever OH122-169 is supported on 6’ to 7-foot shafts.

4.0 Foundation analysis As part of the overhead sign standard drawings (revised 11-21-2014), standard foundations were developed to support overhead signs. These standard foundations consist of two spread footing and two drilled shaft designs to be used on different sign pole sizes (see Drawing ST-3, Standard Overhead Sign Supports Interim Design B).

• Spread Footings: 12 ½ ft. x 18 ft. and 9 ft. x 14 ft. • Drilled Shafts: 3 ft. diameter, 23 ft. deep and

4 ft. diameter, 29 ft. deep In addition, the standard foundation notes state the following requirements:

• All spread footings shall have an allowable design bearing pressure of 1 ¼ tons per square foot

• The drilled shafts have an allowable design lateral

bearing pressure of 250 lbs. per square foot per foot of depth

Based on previous research, these requirements will be met in all but the weakest mineral soils, and therefore represent very conservative soil characteristics for design. In lieu of new foundation designs we checked the foundation soils to see if they met those requirements.


SP 7005‐105 TH 169 Overhead Signs Foundation Recommendations November 3, 2015

The recommendations contained in the paragraphs below are based on our analysis. Due to the risk of shafts being interrupted by bedrock, we recommend the sign bridge OH119-169 and cantilever OH 121-169 foundations consist of spread footings. Spread footings are also a very favorable option for use on OH122-169, but based on CPT c01, a drilled shaft foundation will also work at this location. We recommend the new foundations be designed to meet the requirements of the current standard design tables. Casing will be needed in order to extend the shafts below the groundwater surface.

Foundation Recommendations Based on review of the existing subsurface conditions and proposed structures, we recommend:

1. The overhead sign structures be supported with spread footing foundations as detailed in the typical Foundation Detail Sheet, Drawing ST-3 located on the Traffic Engineering website.

2. Table 1 above, showing the estimated soil and water conditions be forwarded along with a copy of the attached Boring and Sounding Logs to the bidding contractors.

3. That drilled shaft excavations extending below groundwater be temporarily cased to allow the excavation to be advanced and to prevent caving and undermining of nearby structures and pavements. That the casing be removed as the concrete is placed. Attachments: Exploration Plan SPT Index Sheet Boring Log T01, Unique Number 79734 CPT Index Sheet Sounding Logs c-01 through c-04, Unique Numbers 79702-79705 cc: J. Tayse, Signing Engineer E. Peterson, Metro Signing J. Brunner, Chief Geotechnical Engineer


Vane Shear Test Washed Sample (Collected during plug drilling)

Minnesota Department of Transportation Geotechnical Section

Boring Log Descriptive Terminology (English Units)

USER NOTES, ABBREVIATIONS AND DEFINITIONS - Additional information available in Geotechnical Manual. This boring was made by ordinary and conventional methods and with care deemed adequate for the Department's design purposes. Since this boring was not taken to gather information relating to the construction of the project, the data noted in the field and recorded may not necessarily be the same as that which a contractor would desire. While the Department believes that the information as to the conditions and materials reported is accurate, it does not warrant that the information is necessarily complete. This information has been edited or abridged and may not reveal all the information which might be useful or of interest to the contractor. Consequently, the Department will make available at its offices, the field logs relating to this boring. Since subsurface conditions outside each borehole are unknown, and soil, rock and water conditions cannot be relied upon to be consistent or uniform, no warrant is made that conditions adjacent to this boring will necessarily be the same as or similar to those shown on this log. Furthermore, the Department will not be responsible for any interpretations, assumptions, projections or interpolations made by contractors, or other users of this log. Water levels recorded on this log should be used with discretion since the use of drilling fluids in borings may seriously distort the true field conditions. Also, water levels in cohesive soils often take extended periods of time to reach equilibrium and thus reflect their true field level. Water levels can be expected to vary both seasonally and yearly. The absence of notations on this log regarding water does not necessarily mean that this boring was dry or that the contractor will not encounter subsurface water during the course of construction. WATER MEASUREMENT

Augered Plug Drilled Split Tube Sample (SPT N60 2 in. spilt tube with liners) Thin Wall Sample (3 in. Shelby Tube) Core Drilled (NV Core Barrel unless otherwise noted) Continuous Soil Sample Augered & Jetted Jetted Augered & Plug Drilled

WS

PD

CS

A/J Jet A/P

AB ........................ After Bailing AC ........................ After Completion AF......................... After Flushing w/C ....................... with Casing

Index Sheet No. 3.0 March 2003 G:\geotech\Public\Forms\INDEX30.doc

w/M ...................... with Mud WSD ..................... While Sampling/Drilling w/AUG.................. with Hollow Stem Auger MISCELLANEOUS NA ........................ Not Applicable w/ ......................... with w/o ....................... with out sat ........................ saturated DRILLING OPERATIONS AUG ................. Augered CD .................... Core Drilled DBD.................. Disturbed by Drilling DBJ .................. Disturbed by Jetting PD .................... Plug Drilled ST..................... Split Tube (SPT test) TW.................... Thinwall (Shelby Tube) WS.................... Wash Sample NSR.................. No Sample Retrieved

WH ................... Weight of Hammer WR ................... Weight of Rod Mud.................. Drilling Fluids in Sample CS .................... Continuous Sample SOIL/CORE TESTS SPT N60 ............ ASTM D1586 Modified Blows per foot with 140 lb. hammer and a standard energy of 210 ft-lbs. This energy represents 60% of the potential energy of the system and is the average energy provided by a Rope & Cathead system. MC.................... Moisture Content COH ................. Cohesion γ ....................... Sample Density LL..................... Liquid Limit PI...................... Plasticity Index Φ ...................... Phi Angle REC.................. Percent Core Recovered RQD ................. Rock Quality Description (Percent of total core interval consisting of unbroken pieces 4 inches or longer) ACL .................. Average Core Length (Average length of core that is greater than 4 inches long) Core Breaks .... Number of natural core breaks per 2-foot interval. DISCONTINUITY SPACING Fractures Distance Bedding Very Close........ 36 inches ..........Thick DRILLING SYMBOLS

RELATIVE DENSITY Compactness - Granular Soils BPF

very loose....................................0-4 loose ...........................................5-10 medium dense ............................11-24 dense ..........................................25-50 very dense...................................>50

Consistency - Cohesive Soils BPF

very soft.......................................0-1 soft ..............................................2-4 firm ..............................................5-8 stiff ..............................................9-15 very stiff.......................................16-30 hard.............................................31-60 very hard .....................................> 60

COLOR blk .................. Black wht ...........White grn ................. Green brn............Brown orng ............... Orange yel.............Yellow dk ................... Dark lt ...............Light IOS ................. Iron Oxide Stained GRAIN SIZE /PLASTICITY VF............. Very Fine pl ............Plastic F ............... Fine slpl .........Slightly Cr ............. Coarse Plastic SOIL/ROCK TERMS C............... Clay Lmst .......Limestone L ............... Loam Sst ..........Sandstone S............... Sand Dolo........Dolostone Si.............. Silt wx...........weathered G .............. Gravel (No. 10 Sieve to 3 inches) Bldr .......... Boulder (over 3 inches) T ............... till (unsorted, nonstratified glacial deposits) Mn/DOT Triangular Textural Soil Classification System

100%

100%

C

90807060 50 40 302010

90

80

70

60

50

40

30

20

10

(plastic)

(slightly plastic)

SC

SCL CL

L SL SiL

Si

SiCL

LSS Si

90

80

70

60

50

40

30

20

10

100 %

% Sand % Clay

% Silt

0.49

1.00

N/A

10

3

5

8.0742.5

22.5728.0

25.0725.5

27.0723.5

29.0721.5

37.0713.5

37

33

10

8

8

-20

25

26

16

42

97

10

80

250/.3

Sand, brown and moist

Fine Sand, light brown to light Gray, moist to saturated

Loamy Sand with a little Gravel, gray, saturated

Sand and Gravel with stone chips and pieces light gray,saturated

Driller indicates Sandstone Sand, No Sample Recovered.

Approximate Top of Bedrock

DOLOSTONE; gen fresh w/slight weathering; crystalline tomedium grained sand; thin to med bedded w/one high anglejoint near 30.5'; Dolomitic Sandstone zones common; 1" softlight green shale bed at 35.3'; vugs up to 1/2" common; hard;tan to IOS yellow.

Water measured at 11.9' with auger

Bottom of Hole - 37.0'

State Project Bridge No. or Job Desc. Boring No.

7005-105 750.5US Highway T.H. 169 Overhead Signs T01Trunk Highway/Location

OH 119-169Ground Elevation

(DTM)

211304 CME Fat Tire

No Station-Offset Information Available

CME Automatic Calibrated 8/31/15Completed

(ft.)Location Drill Machine

HammerLongitude (West)=93°26'24.73"Drilling

SHEET 1 of 1

Latitude (North)=44°46'59.78"

Scott Coord:X=467922 Y=213533

or MemberFormation

Soi

lMC(%)

Classification

Other Tests

MINNESOTA DEPARTMENT OF TRANSPORTATION - GEOTECHNICAL SECTION

LABORATORY LOG & TEST RESULTS - SUBSURFACE EXPLORATION

(pcf)N60

UNIQUE NUMBER 79734

Depth

COH

Soil Class:JAH Rock Class: Edit: Date: 9/23/15

Breaks

Or Remarks

Elev.

SPT

REC ACL

Dril

ling

Ope

ratio

n

Lith

olog

y

RQD Core

Index Sheet Code 3.0G:\GINT\PROJECTS-ACTIVE\7005-105.GPJ

Roc

k

DE

PT

H

(psf)

(%)

U.S. Customary Units

5

10

15

20

25

30

35

(%) (ft)

1.0' Sand heave afteraugering to 19.5'

set auger to 27.0'

PRAIRIE DU CHIEN GROUP

Minnesota Department of Transportation Geotechnical Section

Cone Penetration Test Index Sheet 1.0 (CPT 1.0) USER NOTES, ABBREVIATIONS AND DEFINITIONS

This Index sheet accompanies Cone Penetration Test Data. Please refer to the Boring Log Descriptive Terminology Sheet for information relevant to conventional boring logs.

This Cone Penetration Test (CPT) Sounding follows ASTM D 5778 and was made by ordinary and conventional methods and with care deemed adequate for the Department's design purposes. Since this sounding was not taken to gather information relating to the construction of the project, the data noted in the field and recorded may not necessarily be the same as that which a contractor would desire. While the Department believes that the information as to the conditions and materials reported is accurate, it does not warrant that the information is necessarily complete. This information has been edited or abridged and may not reveal all the information which might be useful or of interest to the contractor. Consequently, the Department will make available at its offices, the field logs relating to this sounding.

Since subsurface conditions outside each CPT Sounding are unknown, and soil, rock and water conditions cannot be relied upon to be consistent or uniform, no warrant is made that conditions adjacent to this sounding will necessarily be the same as or similar to those shown on this log. Furthermore, the Department will not be responsible for any interpretations, assumptions, projections or interpolations made by contractors, or other users of this log.

Water pressure measurements and subsequent interpreted water levels shown on this log should be used with discretion since they represent dynamic conditions. Dynamic Pore water pressure measurements may deviate substantially from hydrostatic conditions, especially in cohesive soils. In cohesive soils, water pressures often take extended periods of time to reach equilibrium and thus reflect their true field level. Water levels can be expected to vary both seasonally and yearly. The absence of notations on this log regarding water does not necessarily mean that this boring was dry or that the contractor will not encounter subsurface water during the course of construction.

CPT Terminology

CPT ............. Cone Penetration Test CPTU ........... Cone Penetration Test with Pore Pressure measurements SCPTU ......... Cone Penetration Test with Pore Pressure and Seismic measurements Piezocone...Common name for CPTU test

(Note: This test is not related to the Dynamic Cone Penetrometer DCP)

qT TIP RESISTANCE The resistance at the cone corrected for water pressure. Data is from cone with 60 degree apex angle and a 10 cm2 end area. fs SLEEVE FRICTION RESISTANCE The resistance along the sleeve of the penetrometer.

FR Friction Ratio Ratio of sleeve friction over corrected tip resistance. FR = fs/qt Vs Shear Wave Velocity A measure of the speed at which a siesmic wave travels through soil/rock. PORE WATER MEASUREMENTS Pore water measurements reported on CPT Log are representative of water pressures measured at the U2 location, just behind the cone tip, prior to the sleeve, as shown in the figure below. These measurements are considered to be dynamic water pressures due to the local disturbance caused by the cone tip. Dynamic water pressure decay and Static water pressure measurements are reported on a Pore Water Pressure Dissipation Graph.

U2

SBT SOIL BEHAVIOR TYPE Soil Classification methods for the Cone Penetration Test are based on correlation charts developed from observations of CPT data and conventional borings. Please note that these classification charts are meant to provide a guide to Soil Behavior Type and should not be used to infer a soil classification based on grain size distribution. The numbers corresponding to different regions on the charts represent the following soil behavior types: 1. Sensitive, Fine Grained 2. Organic Soils - Peats 3. Clays - Clay to Silty Clay 4. Silt Mixtures - Clayey Silt to Silty Clay 5. Sand Mixtures - Silty Sand to Sandy Silt 6. Sands - Clean Sand to Silty Sand 7. Gravelly Sand to Sand 8. Very Stiff Sand to Clayey Sand 9. Very Stiff, Fine Grained Note that engineering judgment, and comparison with conventional borings is especially important in the proper interpretation of CPT data in certain geo- materials. The following charts are used to provide a Soil Behavior Type for the CPT Data.

Robertson CPT 1990 Soil Behavior type based on friction ratio

Robertson CPTU 1990 Soil Behavior type based on pore pressure

where ... QT.......................... normalized cone resistance Bq .......................... pore pressure ratio Fr ........................... Normalized friction ratio σvo ........................ overburden pressure σ’vo ....................... effective over burden pressure u2 .......................... measured pore pressure u0 .......................... equilibrium pore pressure G:\GEOTECH\PUBLIC\FORMS\CPTINDEX.DOC January 30, 2002

End of Data

Bottom of Hole 32.77

State Project

OH 122-169Bridge No. or Job Desc.

Tip Resistance(psi)UBC 1990 FR

c-01Trunk Highway/Location

(DTM)T.H. 169 Overhead Signs7005-105

Pore Pressure(psi)

Depth

Sounding No.

Elevation

Friction Ratio(%)

Interpreted SoilBehavior Type Sleeve Friction

(psi)

757.5Ground Elevation

Location CPT Machine

8/17/15

Tyler Lueck

SHEET 1 of 1

CPT-STD

203094 CPT Truck


Index Sheet Code 3.0

Scott Co. Coordinate: X=469717 Y=213616 (ft.)


Longitude (West)=93°25'59.85" CPT Operator

Hole Type

Date Completed


Soil Class: Rock Class: Edit: Date: 9/23/15

CONE PENETRATION TEST RESULTS

UNIQUE NUMBER 79702

0

5

10

15

20

25

30

G:\GINT\PROJECTS-ACTIVE\7005-105.GPJ

757.5

752.5

747.5

742.5

737.5

732.5

727.5


20 16 12 8 4 0 0 2 4 6 8 100 2 4 6 8 10 800 1600 2400 3200 4000

G:\geotech\cptdata\th169\7005-105-Tyler (08-18-2015)\7005-105\Cone\E17G1501C.DAT

0 4 8 12 16

End of Data


State Project





Pore Pressure(psi)

Depth

Sounding No.

Elevation

Friction Ratio(%)


(psi)



8/17/15

Tyler Lueck

SHEET 1 of 1

CPT-STD

203094 CPT Truck






Hole Type

Date Completed




UNIQUE NUMBER 79703

0

5

10

15

20

25


756.8

751.8

746.8

741.8

736.8

731.8


20 16 12 8 4 0 0 2 4 6 8 100 2 4 6 8 10 800 1600 2400 3200 4000


0 4 8 12 16

End of Data

Bottom of Hole 9.99

State Project





Pore Pressure(psi)

Depth

Sounding No.

Elevation

Friction Ratio(%)


(psi)



8/17/15

Tyler Lueck

SHEET 1 of 1

CPT-STD

203094 CPT Truck






Hole Type

Date Completed




UNIQUE NUMBER 79704

0

5


753.5

748.5


20 16 12 8 4 0 0 2 4 6 8 100 2 4 6 8 10 800 1600 2400 3200 4000


0 4 8 12 16

End of Data


State Project





Pore Pressure(psi)

Depth

Sounding No.

Elevation

Friction Ratio(%)


(psi)



8/17/15

Tyler Lueck

SHEET 1 of 1

CPT-STD

203094 CPT Truck






Hole Type

Date Completed




UNIQUE NUMBER 79705

0

5

10

15

20

25


753.4

748.4

743.4

738.4

733.4

728.4


20 16 12 8 4 0 0 2 4 6 8 100 2 4 6 8 10 800 1600 2400 3200 4000


0 4 8 12 16

SP7005-105OH Sign Foundation RecsLAYOUTOF3Copy of spt INDEX30_2005DRILLING SYMBOLS

borlogCopy of CPT Indexcptlogs

2015-11-03T15:23:[email protected]

minnesota department of transportation office of materials & … · 2015. 11. 30. · design...

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