geotechnical engineering study proposed 4 … · 7.1 subgrade preparation and structural select...

GEOTECHNICAL ENGINEERING STUDY

PROPOSED 4-STORY HOTEL

CORPUS CHRISTI, TEXAS

Prepared by:

Tolunay-Wong Engineers, Inc.

826 South Padre Island Drive

Corpus Christi, Texas 78416

January 10, 2017

Project No. 16.53.076 / Report No. 13604

TWE Project No. 16.53.076

Report No. 13604

i

TABLE OF CONTENTS

1 INTRODUCTION AND PROJECT DESCRIPTION 1-1

1.1 Introduction 1-1

1.2 Project Description 1-1

2 PURPOSE AND SCOPE OF SERVICES 2-1

3 FIELD PROGRAM 3-1

3.1 Soil Borings 3-1

3.2 Drilling Methods 3-1

3.3 Soil Sampling 3-1

3.4 Boring Logs 3-2

3.5 Groundwater Measurements 3-2

4 LABORATORY SERVICES 4-1

5 SITE AND SUBSURFACE CONDITIONS 5-1

5.1 General 5-1

5.2 Site Description and Surface Conditions 5-1

5.3 Subsurface Conditions 5-1

5.4 Subsurface Soil Properties 5-1

5.5 Groundwater Observations 5-2

5.6 Shrink / Swell Potential 5-3

6 FOUNDATION RECOMMENDATIONS 6-1

6.1 Discussion 6-1

6.2 Drilled and Underreamed Piers 6-1

6.3 Grade Beams 6-3

6.4 Lightly Loaded Interior Floor Slabs 6-4

7 EARTHWORK CONSIDERATIONS 7-1

7.1 Subgrade Preparation and Structural Select Fill 7-1

7.2 Drainage 7-2

8 PAVEMENT DESIGN RECOMMENDATIONS 8-1

8.1 New Pavement Sections 8-1

8.2 Pavement Section Materials 8-3

8.3 Pavement Drainage and Maintenance 8-4

9 LIMITATIONS AND DESIGN REVIEW 9-1

9.1 Limitations 9-1

9.2 Design Review 9-1

9.3 Construction Monitoring 9-1

9.4 Closing Remarks 9-1


Report No. 13604

ii

TABLES AND APPENDICES

TABLES

Table 4-1 Laboratory Testing Program 4-1

Table 5-1 Groundwater Level Measurements 5-2

Table 5-2 General Relationship between P.I. and Shrink/Swell Potential 5-3

Table 6-1 Material Excavation and Replacement with Resulting PVR 6-4

Table 7-1 Compaction Equipment and Maximum Lift Thickness 7-1

Table 8-1 Vehicle Classification and Traffic Loading 8-1

Table 8-2 Rigid Pavement Design Values 8-2

Table 8-3 Recommended Minimum Typical Rigid Pavement Thicknesses 8-2

Table 8-4 Rigid Pavement Components 8-3

APPENDICES

Appendix A: Soil Boring Location Plan

TWE Drawing No. 16.53.076-1

Appendix B: Log of Project Borings and a Key to

Terms and Symbols used on Boring Logs


1-1 Report No. 13604

1 INTRODUCTION AND PROJECT DESCRIPTION

1.1 Introduction

This report presents the results of our geotechnical engineering study performed for the proposed

new 4-story hotel in Corpus Christi, Texas. Our geotechnical engineering study was conducted in

accordance with TWE Proposal No. P16-C076, dated August 30, 2016, and authorized by Mr.

Bhakta.

1.2 Project Description

The project involves construction of a new hotel with associated parking and driveway areas. The

new building will be four-stories high with a footprint of about 70-ft. by 230-ft. We understand

that the structure will have a lightly loaded interior floor slab supported by compacted structural

fill material with the superstructure concentrated loads supported by drilled piers. We assume

maximum structural loads will be on the order of 8 to 9 klf (klf = kips per linear foot) for load

bearing walls, and 150 to 200-kips (1 kip = 1,000 lbs.) for concentrated columns. Additionally, an

outdoor pool will be constructed on the south side of the hotel. The finished floor elevation of the

new building will be approximately 2.5-ft. above the existing natural grade at the site. Area

paving is planned to be reinforced concrete and will be primarily subjected to light traffic

conditions (automobiles and light trucks) with occasional delivery truck and solid waste disposal

truck traffic.

TWE Project No. 16.53.076 2-1 Report No. 13604

2 PURPOSE AND SCOPE OF SERVICES

The purposes of our geotechnical engineering study were to investigate the soil and groundwater

conditions within the project site and to provide geotechnical design and construction

recommendations for the proposed facility.

Our scope of services performed for the project consisted of:

1. Drilling two (2) soil borings to depths of 25-ft. & 50-ft. within the project site to

evaluate subsurface stratigraphy and groundwater conditions;

2. Performing geotechnical laboratory tests on recovered soil samples to evaluate the

physical and engineering properties of the strata encountered;

3. Providing geotechnical design and construction recommendations for suitable

foundation system for support of the new hotel;

4. Providing geotechnical design recommendations for rigid (concrete) pavement

sections including subgrade preparation and required component thicknesses; and,

5. Providing geotechnical construction recommendations including site and subgrade

preparation, excavation considerations, fill and backfill requirements, compaction

requirements, foundation installation and overall quality control monitoring, testing

and inspection services.

Our scope of services did not include any environmental assessments for the presence or absence

of wetlands or of hazardous or toxic materials within or on the soil, air or water within this

project site. Any statements in this report or on the boring logs regarding odors, colors or

unusual or suspicious items or conditions are strictly for the information of the Client. A

geological fault study was also beyond the scope of our services associated with this geotechnical

engineering study.


3 FIELD PROGRAM

3.1 Soil Borings

TWE conducted an exploration of subsurface soil and groundwater conditions at the project site

on November 23, 2016 by drilling, sampling, and logging two (2) soil borings to depths of 25-ft.

and 50-ft. below existing grades. The soil boring locations are presented on TWE Drawing No.

16.53.076-1, and can be found in Appendix A of this report. Drilling and sampling of the soil

borings were performed using conventional truck-mounted drilling equipment. Our field

personnel coordinated the field activities and logged the boreholes. The boring locations were

staked at the site by TWE and the latitude and longitude for each boring location were

determined by hand held GPS device and are presented on the boring logs.

3.2 Drilling Methods

Field operations were performed in general accordance with the Standard Practice for Soil

Investigation and Sampling by Auger Borings [American Society for Testing and Materials

(ASTM) D 1452]. The soil borings were drilled using a truck-mounted drilling rig equipped with

a rotary head. The boreholes were advanced using dry-auger and hollow stem drilling methods.

Samples were obtained continuously from existing ground surface to a depth of 12-ft., at the 13-

ft. to 15-ft. depth interval and at intervals of 5-ft. thereafter until the boring completion depths

were reached.

3.3 Soil Sampling

Fine-grained, cohesive soil samples were recovered from the soil borings by hydraulically pushing

3-in diameter, thin-walled Shelby tubes a distance of about 24-in. The field sampling procedures

were conducted in general accordance with the Standard Practice for Thin-Walled Tube Sampling

of Soils (ASTM D 1587). Our geotechnician visually classified the recovered soils and obtained

field strength measurements using a pocket penetrometer. A factor of 0.67 is typically applied to

the penetrometer measurement to estimate the undrained shear strength of the Gulf Coast cohesive

soils. The samples were extruded in the field, wrapped in foil, placed in moisture sealed

containers and protected from disturbance prior to transport to the laboratory.

Cohesionless and semi-cohesionless samples were collected with the standard penetration test

(SPT) sampler driven 18-in by blows from a 140-lb hammer falling 30-in in accordance with the

Standard Test Method for Standard Penetration Test (SPT) and Spilt-Barrel Sampling of Soils

(ASTM D 1586). The number of blows required to advance the sampler three (3) consecutive 6-

in depths are recorded for each corresponding sample on the boring logs. The N-value, in blows

per foot, is obtained from SPTs by adding the last two (2) blow count numbers. The

compactness of cohesionless and semi-cohesionless samples are inferred from the N-value. The

samples obtained from the split-barrel sampler were visually classified, placed in moisture sealed

containers and transported to our laboratory.

The recovered soil sample depths with corresponding pocket penetrometer measurements and

SPT blowcounts are presented on the boring logs in Appendix B.


3.4 Boring Logs

Our interpretations of general subsurface soil and groundwater conditions at the soil boring

locations are included on the boring logs. Our interpretations of the soil types throughout the

boring depths and the locations of strata changes were based on visual classifications during field

sampling and laboratory testing results in accordance with Standard Practice for Classification

of Soils for Engineering Purposes (Unified Soil Classification System) (ASTM D 2487) and

Standard Practice for Description and Identification of Soils (Visual-Manual Procedure) (ASTM

D 2488).

The boring logs include the type and interval depth for each sample along with its corresponding

pocket penetrometer measurements and SPT blow counts. The boring logs and a key to terms

and symbols used on boring logs are presented in Appendix B.

3.5 Groundwater Measurements

Groundwater level measurements were attempted in the open boreholes during dry-auger drilling.

Water level readings were attempted in the open boreholes when groundwater was first

encountered and after a ten (10) to fifteen (15) minute time period. The groundwater

observations are summarized in Section 5.5 of this report entitled “Groundwater Observations.”


4 LABORATORY SERVICES

A laboratory testing program was conducted on selected samples to assist in classification and

evaluation of the physical and engineering properties of the soils encountered in the project borings.

Laboratory tests were performed in general accordance with ASTM International standards. The

types of the laboratory tests performed are presented in Table 4-1. A brief description of the

testing methods is listed below.

Table 4-1: Laboratory Testing Program

Test Description Test Method

Amount of Material in Soils Finer than No. 200 Sieve ASTM D 1140

Unconfined Compressive Strength of Cohesive Soil (UC) ASTM D 2166

Water (Moisture) Content of Soil ASTM D 2216

Liquid Limit, Plastic Limit and Plasticity Index of Soils ASTM D 4318

Density (Unit Weight) of Soil Specimens ---

Amount of Materials in Soils Finer than No. 200 (75-µm) Sieve (ASTM D 1140)

This test method determines the amount of materials in soils finer than the No. 200 (75-µm)

sieve by washing. The loss in weight resulting from the wash treatment is presented as a

percentage of the original sample and is reported as the percentage of silt and clay particles in the

sample.

Unconfined Compressive Strength of Cohesive Soil (ASTM D 2166)

This test method determines the unconfined compressive (UC) strength of cohesive soil in the

undisturbed or remolded condition using strain-controlled application of an axial load. This test

method provides an approximate value of the strength of cohesive materials in terms of total

stresses. The undrained shear strength of a cohesive soil sample is typically one-half (1/2) the

unconfined compressive strength.

Water (Moisture) Content of Soil by Mass (ASTM D 2216)

This test method determines water (moisture) content by mass of soil where the reduction in

mass by drying is due to loss of water. The water (moisture) content of soil, expressed as a

percentage, is defined as the ratio of the mass of water to the mass of soil solids. Moisture

content may provide an indication of cohesive soil shear strength and compressibility when

compared to Atterberg Limits.

Liquid Limit, Plastic Limit and Plasticity Index of Soils (ASTM D 4318)

This test method determines the liquid limit, plastic limit and the plasticity index of soils. These

tests, also known as Atterberg limits, are used from soil classification purposes. They also

provide an indication of the volume change potential of a soil when considered in conjunction

with the natural moisture content. The liquid limit and plastic limit establish boundaries of

consistency for plastic soils. The plasticity index is the difference between the liquid limit and

plastic limit.


Dry Unit Weight of Soils

This test method determines the weight per unit volume of soil, excluding water. Dry unit

weight is used to relate the compactness of soils to volume change and stress-strain tendencies of

soils when subjected to external loadings.

Soil properties including moisture content, dry unit weight, Atterberg Limits, grain size

distribution, penetration resistance, and compressive strength are presented on the project boring

logs in Appendix B.


5 SITE AND SUBSURFACE CONDITIONS

5.1 General

Our interpretations of soil and groundwater conditions within the project site are based on

information obtained at the soil boring locations only. This information has been used as the

basis for our conclusions and recommendations included in this report. Subsurface conditions

may vary at areas not explored by the soil borings. Significant variations at areas not explored by

the soil borings will require reassessment of our recommendations.

5.2 Site Description and Surface Conditions

The site is an approximate 2-acre tract of land located south of South Padre Island Dr. (TX HWY

358, SPID) frontage road near Airline Rd., in Corpus Christi, Texas. The vacant property is

specifically located behind several existing businesses which can be accessed from the frontage

road. The site is also accessible by utilizing a connector street which runs between Williams Dr.,

and SPID frontage road. At the time of our field investigation, the site was covered by native

vegetation (grass and weeds), with overgrown brush and trees towards the southern area of the

property. Topographic survey information provided by the client for the site indicated an

approximate change in elevation of about 1 to 1.5-ft. in the proposed location of the building

foundation. The site was observed to be at a higher elevation along its east boundary and

decreased in elevation towards the north, west, and south boundaries. Poor drainage was

exhibited on the north side of the property.

5.3 Subsurface Conditions

The soil profile encountered in the project borings consisted mostly of cohesive soils, with a

clayey sand stratum in boring B-2. Sandy Fat Clay (CH), Fat Clay with Sand (CH), Lean Clay

with Sand (CL), Fat Clay (CH), and Sandy Lean Clay (CL) soils were encountered from existing

grade to termination depths of 25-ft. and 50-ft. below existing grade. The Clayey Sand (SC)

stratum was present below about 10-ft. and extended to about 14.5-ft. in Boring B-2. The

consistency of the clay soils was typically stiff to hard, but soft between about 13-ft and 16-ft in

boring B-1. The relative density of the clayey sand stratum ranged from medium dense to very

dense. Detailed descriptions of the soils encountered at the boring locations are presented on the

boring logs in Appendix B.

5.4 Subsurface Soil Properties

Results of Atterberg Limit tests on selected cohesive soil samples from the project borings

indicated liquid limits (LL) ranging from 30 to 80 with corresponding plasticity indices (PI)

ranging between 15 to 64. In-situ moisture contents of the soils ranged from 14% to 29%. The

amount of material passing the No. 200 sieve ranged from 54% to 90% within the selected

cohesive samples tested for grain size distribution.

Undrained shear strengths derived from field pocket penetrometer readings ranged from 0.50-tsf.

to 4.50+-tsf. Undrained shear strengths derived from laboratory unconfined compressive (UC)

strength testing ranged from 0.47-tsf. to 2.84-tsf., with corresponding dry unit weights ranging


from 95-pcf. to 105-pcf. Shear strengths of cohesive soils inferred from SPT blow counts varied

from soft to stiff.

The results of Atterberg Limit tests performed on the selected semi-cohesionless samples (clayey

sand) from Boring B-2 indicated a liquid limit of 38 with a corresponding PI of 26. In-situ

moisture content and percent finer than No. 200 sieve tests for the clayey sands ranged from 20%

to 24% and 39% to 47%, respectively.

Tabulated laboratory test results at the recovered sample depths are presented on the boring logs

in Appendix B.

5.5 Groundwater Observations

Groundwater measurements were attempted in the project borings during dry-auger drilling.

Groundwater level measurements are shown in Table 5-1 below.

Table 5-1:

Groundwater Level Measurements

Boring

No.

Boring

Depth

(feet)

Groundwater Level Depth

Encountered

During Drilling

(feet)

Observed in the Open Borehole after 10 to 15

minutes (feet)

B-1 50’ 15’ 11’-6”

B-2 25’ 13’ 9’-6”

Groundwater levels may fluctuate with climatic and seasonal variations and should be verified

before construction. Accurate determination of the static groundwater level is typically made with a

standpipe piezometer. Installation of a piezometer to evaluate the long-term groundwater condition

was not included within the current scope of services.


5.6 Shrink / Swell Potential

The tendency for a soil to shrink and swell with change in moisture content is a function of clay

content and type which are generally reflected in soil consistency as defined by Atterberg Limits. A

generalized relationship between shrink/swell potential and soil plasticity index (PI) is shown in

Table 5-2 below.

Table 5-2:

General Relationship Between PI and Shrink/Swell Potential

P.I. Range Shrink/Swell Potential

0 – 15 Low

15 – 25 Medium

25 – 35 High

> 35 Very High

The amount of expansion that will actually occur with increase in moisture content is inversely

related to the overburden pressure. Therefore, the larger the overburden pressure, the smaller the

amount of expansion. Near-surface soils are thus most susceptible to shrink/swell behavior because

they experience low amounts of overburden. Overall, the cohesive soils at this site possess high to

very high shrink/swell potential.


6 FOUNDATION RECOMMENDATIONS

6.1 Discussion

The soils above a depth of about 12-ft at this site are plastic sandy fat clays and fat clays with

sand, which can experience significant shrink/swell movements with change in moisture content.

Based on the expansive nature of the shallow clay soils and the anticipated column loads for the

structure, a foundation system that is capable of transferring column loads to below the zone of

seasonal moisture change is needed for the project. A foundation system such as drilled and

underreamed piers can be used for this purpose. Recommendations for design and construction

of drilled and underreamed piers are provided below.

6.2 Drilled and Underreamed Piers

Drilled and underreamed piers can be used for support of the proposed hotel at the site. Design

and construction recommendations pertaining to drilled and underreamed piers are provided in

the following report sections.

6.2.1 Pier Depth

Drilled and underreamed piers should be founded at a depth of about 24-ft. below the top of the

building pad within the natural clay soils. At this depth, the piers should be founded below any

water bearing strata as well as the weaker soils in the range of about 13-ft to 16-ft in boring B-1.

We recommend that drilled and underreamed piers have a minimum shaft diameter of 18-in. to

facilitate inspection of the excavation and reinforcement placement.

We recommend the ratio of underream to shaft diameter be no greater than 3. The angle of

underreamed bells to horizontal should not be less than 45° to avoid potential collapse of the

bells. In the event of borehole sloughing or caving at the time of bell drilling, a larger angle of

60° should be used. If stable excavation of bells cannot be completed because local anomalies

are encountered or sloughing and caving occurs, TWE should be contacted to investigate the

problem and modify our recommendations accordingly.

6.2.2 Allowable Bearing Pressures

Drilled and underreamed piers founded on undisturbed natural soils at a depth of about 24-ft.

below the top of building pad can be designed using a net allowable bearing pressure of 6,000

pounds per square foot (psf) for dead plus sustained live load or 9,500-psf for total load

conditions, whichever condition governs. These net allowable bearing pressure values contain a

factor of safety of 3.0 and 2.0 against bearing capacity failure, respectively. The clear spacing

between underreamed piers should be a minimum of one (1) underream diameter to avoid

influence of adjacent footings.


6.2.3 Settlement

Settlement of properly constructed drilled and underreamed piers bearing on natural soils at a

depth of about 24-ft. below the top of the building pad, and designed using the allowable bearing

pressures presented above, should be less than 1-in. Drilled piers should have a clear spacing of

one (1) underream diameter of the larger adjacent underream. Differential settlements between

drilled piers will be governed by variation in subsurface conditions, structural loading conditions,

and quality of the pier construction such as cleanliness of the underream.

6.2.4 Uplift Load Due to Swell Pressure

Swell pressure induced uplift loads acting on drilled piers can be estimated using a unit uplift

skin friction (fs) in pounds per square foot (psf) acting on the outer perimeter of the shaft from

the bottom of the structural select fill building pad, if present, to a depth of about 12-ft below top

of the building pad. The estimated uplift skin friction derived from the subsurface conditions

encountered in the project boring can be taken as 800-psf. The piers should be adequately

reinforced to resist the tensile loads without inducing any distress to the structure or piers.

6.2.5 Uplift Resistance

The allowable uplift capacity of drilled and underreamed piers within the project site could be

calculated using the following equations:

For Df/B > 1.5

Qa = Wf/1.2 + [8.1(B2 – b

2)/FS]

For Df/B < 1.5

Qa = Wf/1.2 + [3.5(Df/B)2(B

2 – b

2)/FS]

where:

Qa = Allowable Uplift Capacity (kips)

Wf = Weight of Footing (kips)

Df = Depth of Base of Footing below Ground Surface (ft)

B = Diameter of Underream (ft)

b = Diameter of Shaft (ft)

FS = Factor of Safety (2.0 for transient loads, 3.0 for sustained loads)

It is recommended that a total unit weight of 150-pcf be used for concrete to calculate the weight

of the footing. The weight of the footing should be reduced by a factor of safety of 1.2.


6.2.6 Underreamed Pier Construction

The following items will be important to the successful completion of drilled and underreamed

piers.

All pier excavations should be observed by TWE to determine when the proper bearing

stratum is encountered and to record other observations regarding pier excavations. Pier

excavations should be checked for size and depth prior to the placement of steel and

concrete. Precautions should be taken during the placement of the pier reinforcement

and concrete to prevent loose excavated material from falling into the excavation.

Drilled piers should be installed in accordance with the Manual on Drilled Shafts:

Construction Procedures and Design Methods, [U.S. Department of Transportation-

Federal Highway Administration (Pub. No. FHWA-IF-99-025) and ADSC: The

International Association of Foundation Drilling Contractors (Pub. No. ADSC-TL-4),

August 1999] by Lymon, C. Reese and Michael W. O'Neill.

To minimize the length of time the soils are left unsupported and exposed to the

elements, we recommend that structural pier concrete be on site and prepared for

placement prior to belling (underreaming). Reinforcing steel and concrete should be

placed immediately after acceptance of the underream. This should help to reduce the

possibility of sloughing/caving and/or intrusion of groundwater into open excavations by

minimizing the time the bell remains open without concrete

Based on the subsurface conditions and the depth of the static groundwater level

encountered in the borings, sandy semi-cohesive soils with groundwater are anticipated

to be encountered in drilled pier excavations. We anticipate the use of temporary steel

casing or other appropriate measures to facilitate proper drilled pier installation.

Temporary casing should be sealed in the clay soils below the water bearing clayey

sands. A positive head of plastic concrete must be maintained above the static

groundwater level during extraction of the casing.

Reinforcement steel cages placed in pier shafts should be designed to be stable during

the placement of concrete. Prompt placement of concrete in excavations as they are

completed, cleaned and inspected is strongly recommended to limit deterioration of the

bearing stratum. Under no circumstances should a pier be drilled that cannot be filled

with concrete before the end of the working day.

6.3 Grade Beams

Grade beams spanning between drilled piers should be structurally suspended above the

subgrade. A minimum 8-in void space should be provided between the bottom of the grade

beams and the top of the subgrade. Cardboard carton forms are commonly used for this purpose.

The sides of excavations should be protected from sloughing, thus, filling the void space.


6.4 Lightly Loaded Interior Floor Slabs

Surface and near surface soils encountered in the project borings for this site possess high

shrink/swell potential with changes in moisture content. Based on the results of our field and

laboratory programs, the Potential Vertical Rise (PVR) for the existing subsurface soil profile at

this site, as determined by Test Method TEX-124-E is calculated to be about 5.0 to 5.5-in for

”dry” moisture conditions. It is generally accepted that a primary source of foundation distress in

the Coastal Bend is soil movements associated with shrink/swell behavior of the underlying

supporting soils. It is therefore recommended that measures be taken to reduce potential

shrink/swell movements below ground supported floor slabs for the proposed building.

Typically, potential movements below lightly loaded interior floors are reduced to the order of

one (1)-in or less, although in some instances movements of more than one (1)-in are acceptable.

The most positive means of reducing potential floor slab movement at this site is the use of a

structurally suspended floor system. The floor slab is structurally suspended above the subgrade

with a minimum crawl space of 8-in. Loads from the floor slab are carried to grade beams which

transfer the loads to columns and the drilled pier foundation. The crawl space subgrade should

be shaped and graded to avoid ponding of water on its surface. Water should be drained to the

perimeter of the crawl space and carried well away from the building prior to discharging.

As an alternate, floor slabs for the proposed building may also consist of ground-supported units

provided that potential shrink/swell movements are reduced to tolerable levels. A typical method

of reducing the swell potential includes removal of a portion of the existing clay soils and

installation of non-expansive structural fill beneath the floor slab. The amount of removal and

replacement needed is dependent upon the amount of shrink/swell movement that the foundation

and/or superstructure can tolerate and determined by the structural engineer.

It is our understanding that the finished floor elevation (FFE) will be approximately 2.5-ft. above

existing grade. TWE recommends that non-expansive structural fill material be utilized to bring

the existing grade up to FFE. Utilizing this information, a summary of PVR values with

corresponding excavation and replacement material amounts for “dry” moisture conditions are

provided in Table 6-1 below. This method has beneficial results but does not totally eliminate

the potential for shrink/swell movements.

Table 6-1:

Material Excavation and Replacement with Resulting PVR

Amount of Excavation

(feet)

Amount of Replacement

(feet) Resulting PVR (in.)

0 2 4.0 to 4.5

2 4 2.75 to 3.25

4 6 2.0 to 2.5

6 8 1.5 to 1.75

8 10 1.0 to 1.25


Based on these results, we recommend that site preparation include:

Removal of the existing soils to the specified depth listed above in Table 6-1 for the

allowable PVR determined by the structural engineer.

After achieving specified subgrade elevation, proof-roll exposed subgrade and compact as

indicated below.

After testing and acceptance of subgrade, immediate placement and compaction of non-

expansive structural select fill as listed in Table 6-1, within the footprint of the proposed

new building as indicated below.

Maintain moisture in select fill pad until the concrete floor slab is constructed.

The subgrade to receive non-expansive structural fill should be proof-rolled as indicated below in

Section 7.1. After proof-rolling, the subgrade should be scarified to a depth of 8-in, moisture

adjusted to above (0 to +4%) optimum moisture content, and compacted to at least 95% of

maximum dry density determined by ASTM D 698. After testing is accepted, the first lift of

structural fill should be immediately placed and compacted.

Material and compaction requirements for non-expansive structural fill are provided below in

Section 7.1 of this report. It is recommended that select fill be used for elevation of the building

pad above existing grade at least 12 inches to provide positive drainage away from the building.

It should be noted that these methods for reducing shrink/swell movements are designed for

normal seasonal changes in soil moisture content of the subgrade soils. Excessive shrink/swell

movements can be expected if increases in soil moisture content occur as a result of broken water

and sewer lines, improper drainage of surface water, shrubbery and trees planted near the

foundation slab and excessive lawn or shrubbery irrigation. Gutter and downspouts should be

provided and runoff should be carried away from the building before discharging unto flatwork

or paving.

Due to the expansive nature of the subgrade soils at this site, special care should be taken not to

allow the exposed subgrade soils to become extremely wet or extremely dry of the existing

moisture content. Therefore, delays between excavation and fill placement should be avoided. If

construction occurs during rainy weather and the exposed subgrade soils are allowed to become

wet or saturated, removal and replacement of excessively soft, wet soils or lime-stabilization

should be anticipated. The depth of undercutting should be determined in the field by TWE.

It is recommended that a vapor barrier such as polyethylene sheeting be provided beneath the soil

supported floor slab. Adequate construction joints and reinforcement should be provided to

reduce the potential for cracking of the floor slab due to differential movement and volume

change in concrete. Crawl spaces below suspended floor systems should be thoroughly

ventilated to reduce potential for moisture to be trapped below floors.


7 EARTHWORK CONSIDERATIONS

7.1 Subgrade Preparation and Structural Select Fill

Any subgrade to receive fill soils or pavements should be proof rolled with at least a 20-ton

pneumatic roller, loaded dump truck, or equivalent, to detect weak areas. Such weak areas

should be removed and replaced with soils exhibiting similar classification, moisture content,

and density as the adjacent in-place soils. Subsequent to proof rolling, and just prior to

placement of select fill, the exposed subgrade should be compacted to at least 95% of the

maximum dry density at a moisture above (0 to +4%) the optimum moisture in accordance with

Standard Proctor (ASTM D 698) procedures.

Proper site drainage should be maintained during construction so that ponding of surface runoff

does not occur and cause construction delays and/or inhibit site access. Due to the nature of the

subgrade, the cohesive soils can become wet and soft. If the subgrade becomes wet and soft,

consideration can be given to removal or replacement of the wet material with structural fill

material.

The maximum loose thickness for each lift will depend on the type of compaction equipment

used. Recommended fill layers are summarized in Table 7-1 below.

Table 7-1: Compaction Equipment and Maximum Lift Thickness

Compaction Equipment Maximum Lift Thickness

Mechanical Hand Tamper 4.0-in

Pneumatic Tired Roller 6.0-in

Tamping Foot Roller 8.0-in

Sheepsfoot Roller 8.0-in

Non-expansive structural fill for this project should consist of a clean low-plasticity sandy clay (CL)

or clayey sand (SC) material with a liquid limit of less than 40 and a plasticity index between 7 and

20. The select fill should be placed in thin lifts, not exceeding 8-in loose measure, moisture

conditioned to between -2% and +3% of optimum moisture content, and compacted to a minimum

95% of the maximum dry density as determined by ASTM D 698 (Standard Proctor).

Prior to any filling operations, samples of the proposed borrow materials should be obtained for soil

classification and laboratory moisture-density testing. The tests will provide a basis for evaluation

of fill compaction by in-place density testing. A qualified soil technician should perform sufficient

in-place density tests during the earthwork operations to verify that proper levels of compaction are

being attained.


7.2 Drainage

The performance of the foundation system for the proposed building and site pavement will not

only be dependent upon the quality of construction but also upon the stability of the moisture

content of the near surface soils. Therefore, we highly recommend that site drainage be developed

so that ponding of surface runoff near the building or pavement does not occur. Accumulations of

water near the structure foundation or pavement could cause significant moisture variations in the

soils adjacent to the foundation and pavement thus increasing the potential for structural distress.


8 PAVEMENT DESIGN RECOMMENDATIONS

8.1 New Pavement Sections

It is our understanding that a rigid pavement system is preferred for proposed driveways and

parking areas associated with this project. Since detailed traffic loads and frequencies were not

available at the time of this report, we have assumed traffic frequencies and loading for similar

projects that have been completed in the past. The assumed traffic frequencies and loads used to

design pavement sections for this project are presented in Table 8-1 below.

Table 8-1: Vehicle Classification and Traffic Loading

Pavement Area Traffic Design Index Description

Light-Duty

Pavements DI-1

Designed using traffic conditions of 20,000 18-kip

equivalent single axle loads (ESALs).

Heavy-Duty

Pavements DI-2

Designed using traffic conditions of 120,000 18-

kip equivalent single axle loads (ESALs).

Based on the estimated traffic conditions and methods found in the AASHTO, Guide for Design of

Pavement Structures, design recommendations for rigid pavement sections using a 20 year design

life are provided in the following sections of this report. The DI-2 pavement sections provided

should be used for routes used by delivery and waste disposal trucks. A reinforced concrete pad

should be placed at the location so that the waste disposal truck’s loading end tires rest on the pad

during waste bin unloading. The traffic conditions presented above should be verified by the civil

design engineer. TWE should be contacted for possible further recommendations if actual traffic

conditions vary from those presented above.

8.1.1 Rigid Pavement Design

The primary design requirements needed for rigid pavement design according to the AASHTO

Guide include the following:

28-day Concrete Modulus of Rupture, psi;

28-day Concrete Elastic Modulus, psi;

Effective Modulus of Subgrade Reaction, pci (k-value);

Serviceability Indices;

Load Transfer Coefficient;

Drainage Coefficient;

Overall Standard Deviation;

Reliability, %; and,

Design Traffic, 18-kip Equivalent Single Axle Load (ESAL)

In our analysis, we assumed U.S. climatic region I (wet and no freeze characteristics), the values

used for our analyses are presented in Table 8-2 on the following page.


Table 8-2: Rigid Pavement Design Values

Description Value

28-day Concrete Modulus of Rupture (Mr) 620-psi

28-day Concrete Elastic Modulus 5,000,000-psi

Effective Modulus of Subgrade Reaction 50-pci

Serviceability Indices Initial 4.5

Terminal 2.5

Load Transfer Coefficient 3.2

Drainage Coefficient 1.0

Overall Standard Deviation 0.39

Reliability 80

Design Traffic, 18-kip Equivalent Single Axle Load (ESAL) – Light-Duty Pavement (DI-1) 20,000

Design Traffic, 18-kip Equivalent Single Axle Load (ESAL) – Heavy-Duty Pavement (DI-2) 120,000

Table 8-3 below, provides the recommended minimum typical pavement section derived from

our analysis using the AASHTO Pavement Design Guide.

Table 8-3: Recommended Minimum Typical Rigid Pavement Thicknesses

Traffic Design Index RC LSS CS

DI-1

Option A 5.0-in. 8.0-in. ---

Option B 6.0-in. --- 8.0-in.

DI-2

Option A 7.0-in. 8.0-in. ---

Option B 8.0-in. --- 8.0-in.

RC = Reinforced Portland Cement Concrete

LSS = Lime Stabilized Subgrade

CS = Compacted Subgrade

Reinforcing steel consisting of deformed steel rebar should be used in concrete pavement.

Thickness is based on concrete flexural strength, soil modulus and traffic volume. Selection of

steel is dependent on joint spacing, slab thickness and other factors as discussed in Portland Cement

Association publications. The following suggested guidelines for the concrete pavement should be

modified by the civil-structural engineer based upon the actual configuration of the pavement layout

and published Portland Cement Association and ACI articles. Table 8-4 on the following page

presents these guidelines.


Table 8-4: Rigid Pavement Components

Component Description

Minimum Reinforcing Steel #3 bars should be spaced at 18-in on centers in both directions.

Minimum Dowel Size 3/4-in bars, 18-in in length, with one (1) end treated to slip

should be spaced at 12-in on centers at each joint.

Control Joint Spacing

Maximum control joint spacing should be 15-ft. If sawcut,

control joints should be cut as soon as the concrete has hardened

sufficiently to permit sawing without excessive raveling which is

usually within four (4) to twenty-four (24) hours of concrete

placement.

Isolation / Expansion Joints Expansion joints should be used in areas adjacent to structures,

such as manholes and walls.

8.2 Pavement Section Materials

Reinforced Concrete (RC)

RC should be provided in accordance with TxDOT Item 421 “Hydraulic Cement Concrete”,

2004. Concrete should be designed to meet a minimum average flexural strength (modulus of

rupture) of at least 620-psi at 28-days or a minimum average compressive strength of 4,500-psi at

28-days. Reinforcing steel consisting of deformed steel rebar should be used in accordance with

TxDOT Item 440 “Reinforcing Steel.”

The first few loads of concrete should be checked for slump, air and temperature on start-up

production days to check for concrete conformance and consistency. Concrete should be

sampled and strength test specimens [two (2) specimens per test] prepared on the initial day of

production and for each 400-yd2 or fraction thereof of concrete pavement thereafter. At least one

(1) set of strength test specimens should be prepared for each production day. Slump, air and

temperature tests should be performed each time strength test specimens are made. Concrete

temperature should also be monitored to ensure that concrete is consistently within the

temperature requirements.

Lime Stabilized Subgrade

Lime stabilization of the subgrade soils can be considered for the pavement sections included in

Table 8-3 above. Proper preparation and lime stabilization of the pavement subgrade will

improve long-term pavement performance by reducing plasticity of the clay soils, increasing their

load carrying capacity, and improving their workability.

After completion of necessary stripping and clearing, the exposed soil subgrade should be

carefully evaluated by probing and testing. Any unsuitable material (shell, gravel, organic

material, wet, soft or loose soil) still in place should be removed. The exposed soil subgrade

should be further evaluated by proofrolling with a heavy pneumatic tired roller, loaded dump


truck or similar equipment weighing at least 20-tons to ensure that soft or loose material does not

exist beneath the exposed soils. Proofrolling procedures should be observed routinely by a

qualified representative of TWE. Any undesirable material revealed should be removed and

replaced in a controlled manner with soils similar in classification or select fill. If lime

stabilization is not used, the subgrade should be compacted as indicated below.

Once final subgrade elevation is achieved and prior to placement of reinforced concrete wearing

surface, the exposed surface of the pavement subgrade soil should be scarified to a depth of 8-in

and mixed with hydrated lime in conformance with TxDOT Item 260 “Lime Treatment (Road-

Mixed)”. It is estimated that 7% hydrated lime by dry unit weight of soil will be required.

Assuming an in-place unit weight of 120-pcf for the roadway subgrade soils, 7% lime by dry unit

weight equates to about 50-lbs of lime per square yard of treated subgrade. The actual quantity

of lime required should be determined after the pavement area is stripped and subgrade soils are

exposed by use of a laboratory soil treatability study. Lime used during chemical stabilization

should be Type A hydrated lime or Type B commercial slurry. The lime stabilized subgrade

should be compacted to a minimum 95% of the maximum dry density as determined by ASTM D

698 at a moisture content within the range of 4% above optimum.

Lime stabilization should extend at least 1-ft beyond the pavement edge to reduce effects of

seasonal shrinking and swelling. In areas where hydrated lime is used for stabilization, routine

sampling and Atterberg limit tests should be performed to verify the resulting plasticity index of

the stabilized mixture is at/or below 20.

Mechanical lime stabilization of the pavement subgrade will not prevent normal seasonal

movement of the underlying untreated materials. Therefore, good perimeter surface drainage

with a minimum 2% slope away from the pavement is recommended.

8.3 Pavement Drainage and Maintenance

Providing drainage away from the pavement and maintaining the pavement to prevent infiltration

of water into the subgrade soils is essential. Water ponding adjacent to the pavement will

infiltrate the subgrade and result in high maintenance costs and premature pavement failure and,

therefore, should be avoided. Periodic maintenance should be performed on the pavement

sections to seal any surface cracks and prevent infiltration of water into the subgrade.


9 LIMITATIONS AND DESIGN REVIEW

9.1 Limitations

This report has been prepared for the exclusive use of Kantibhai Bhakta and the project team for

specific application to the design and construction of the proposed new 4-story hotel in Corpus

Christi, Texas. Our report has been prepared in accordance with the generally accepted

geotechnical engineering practice common to the local area. No other warranty, express or

implied, is made.

The analyses and recommendations contained in this report are based on the data obtained from

the referenced subsurface explorations within the project site. The soil borings indicate

subsurface conditions only at the specific location, time and depth penetrated. The soil borings

do not necessarily reflect strata variations that could exist at other locations within the project

site. The validity of our recommendations is based in part on assumptions about the stratigraphy

made by the Geotechnical Engineer. Such assumptions may be confirmed only during

construction and installation of the project structures. Our recommendations presented in this

report must be reevaluated if subsurface conditions during the construction phase are different

from those described in this report.

If any changes in the nature, design or location of the project are planned, the conclusions and

recommendations contained in this report should not be considered valid unless the changes are

reviewed and the conclusions modified or verified in writing by TWE. TWE is not responsible

for any claims, damages or liability associated with interpretation or reuse of the subsurface data

or engineering analyses without the expressed written authorization of TWE.

9.2 Design Review

Review of the design and construction drawings as well as the specifications should be

performed by TWE before release. The review is aimed at determining if the geotechnical design

and construction recommendations contained in this report have been properly interpreted.

Design review is not within the authorized scope of work for this study.

9.3 Construction Monitoring

Construction surveillance is recommended and has been assumed in preparing our

recommendations. These field services are required to check for changes in conditions that may

result in modifications to our recommendations. The quality of the construction practices will

affect foundation performance and should be monitored. TWE would be pleased to provide

construction monitoring, testing and inspection services for the project.

9.4 Closing Remarks

We appreciate the opportunity to be of service during this phase of the project and we look

forward to continuing our services during the construction phase and on future projects.

TWE Project No. 16.53.076 Report No. 13604

APPENDIX A

SOIL BORING LOCATION PLAN

TWE DRAWING NO. 16.53.076-1

COPYRIGHT © 2015 GOOGLE MAP. ALL RIGHTS RESERVED.

B-2

COPYRIGHT © 2015 GOOGLE MAP. ALL RIGHTS RESERVED.

B-1

Sheet: 1

File: C:\Users\ecrochet\Desktop\Desktop_Folder\CAD\CAD\XREF\TWE_Logo.pdf

Missing or invalid reference

R S S Architects L.L.C. Drawing # A-201

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Boring Location Plan Proposed Hotel - Mccor Hospitality Corpus Christi, Texas

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SOIL BORING LOCATION

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PROJECT LOCATION

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Drawn

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Scale

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Checked

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Approved

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BORING

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LONGITUDE

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LATITUDE

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DEPTH

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LEGEND

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SOIL BORING COORDINATES

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SYMBOL

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DESCRIPTION

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TWE DRAWING NO.

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VICINITY MAP

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R.S.

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11/21/2016

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R.A.S.

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11/28/2016

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D.R.R.

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12/20/2016

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N.T.S.

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16.53.076-1

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B-1

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50'

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N 27° 42' 8.20"

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W 97° 21' 53.40"

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B-2

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25'

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N 27° 42' 9.94"

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W 97° 21' 52.69"

TWE Project No. 16.53.076 Report No. 13604

APPENDIX B

LOGS OF PROJECT BORINGS AND A KEY TO

TERMS AND SYMBOLS USED ON BORING LOGS

0

5

10

15

20

25

30

35

Stiff to hard dark gray SANDY FAT CLAY (CH) withtrace organics

-color changes to dark brown with calcareous nodules

-with gypsum crystals and ferrous stains

-color changes to light brown

-with sand seams and partings, becomes soft below13.5-ft.

Stiff to hard light brown FAT CLAY with SAND (CH),gypsum crystals, and ferrous stains

-with sand seams

-with gypsum crystals and calcareous nodules

Stiff to very stiff tan and gray FAT CLAY (CH)

-with calcareous nodules and ferrous stains

(P) 4.50+

(P) 4.50+

(P) 1.50

(P) 1.25

(P) 0.50

(P) 4.50+

(P) 2.75

(P) 3.50

3/6"5/6"5/6"

2/6"1/6"2/6"

5/6"6/6"7/6"

14

23

23

25

29

21

106

100

102

104

64

59

55

51

47

38

1.40

1.49

1.49

5

14

6

63

70

75

54

73

90

TOLUNAY-WONG ENGINEERS, INC.

LOG OF BORING B-1PROJECT: Proposed Hotel

Corpus Christi, TexasCLIENT: Mccor Hospitality

COMPLETION DEPTH: 50 ft REMARKS: Groundwater was encountered at a depth of 15-ft. during drilling operations.After a 15-min. waiting period, water level was at a depth of 11'-6" belowexisting grade. At the completion of drilling, the open borehole was backfilledwith soil cuttings.

DATE BORING STARTED: 11/23/2016DATE BORING COMPLETED: 11/23/2016LOGGER: J. DesaiPROJECT NO.: 16.53.076

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MATERIAL DESCRIPTION

COORDINATES: N 27° 42' 08.20"W 97° 21' 53.40"

SURFACE ELEVATION: --DRILLING METHOD:

Dry Augered: 0-ft. to 50-ft.Wash Bored: -- to --

(P)

PO

CK

ET

PE

N (

tsf)

(T)

TO

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AN

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psf)

ST

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EN

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RA

TIO

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ST

(blo

ws/ft)

MO

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EN

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%)

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NIT

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(pcf)

LIQ

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LIM

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(%)

PLA

ST

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ST

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TH

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FA

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%)

CO

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G

PR

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PA

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#200

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2

35

40

45

50

55

60

65

70

Stiff to very stiff tan and gray FAT CLAY (CH),slickensided with calcareous nodules and ferrous stains

Firm tan and gray SANDY LEAN CLAY (CL)

Bottom @ 50'

(P) 1.50

(P) 3.75

(P) 3.25

26

20

98

108 30 15

2.84

0.47

11

4

87

69






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COORDINATES: N 27° 42' 08.20"W 97° 21' 53.40"



(P)

PO

CK

ET

PE

N (

tsf)

(T)

TO

RV

AN

E (

psf)

ST

D. P

EN

ET

RA

TIO

N

TE

ST

(blo

ws/ft)

MO

IST

UR

E

CO

NT

EN

T (

%)

DR

Y U

NIT

WE

IGH

T

(pcf)

LIQ

UID

LIM

IT

(%)

PLA

ST

ICIT

Y

IND

EX

(%

)

CO

MP

RE

SS

IVE

ST

RE

NG

TH

(ts

f)

FA

ILU

RE

ST

RA

IN (

%)

CO

NF

ININ

G

PR

ES

SU

RE

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PA

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#200

SIE

VE

(%

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OT

HE

R T

ES

TS

PE

RF

OR

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D

2

0

5

10

15

20

25

30

35

Stiff to hard dark gray and brown FAT CLAY with SAND(CH), trace organics

-color changes to gray and brown

-color changes to brown

-color changes to brown and light brown, with gypsumcrystals and ferrous stains

-color changes to light brown and gray, becomesslickensided

Medium dense to very dense light brown and grayCLAYEY SAND (SC)

-color changes to brown and gray

Very stiff to hard brown and gray LEAN CLAY withSAND (CL), trace calcareous nodules

-color changes to gray with sand seams

-color changes to brown and gray

Bottom @ 25'

(P) 4.50

(P) 2.50

(P) 1.50

(P) 2.00

(P) 1.50

(P) 0.50

(P) 4.50+

(P) 3.75

2/6"50/6"

20

28

28

20

24

19

96

95

96

107

108

69

80

38

44

50

64

26

29

1.18

1.56

2.64

8

15

9

67

73

82

47

39

74






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COORDINATES: N 27° 42' 09.94"W 97° 21' 52.69"



(P)

PO

CK

ET

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N (

tsf)

(T)

TO

RV

AN

E (

psf)

ST

D. P

EN

ET

RA

TIO

N

TE

ST

(blo

ws/ft)

MO

IST

UR

E

CO

NT

EN

T (

%)

DR

Y U

NIT

WE

IGH

T

(pcf)

LIQ

UID

LIM

IT

(%)

PLA

ST

ICIT

Y

IND

EX

(%

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CO

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RE

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IVE

ST

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TH

(ts

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CO

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G

PR

ES

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