A1.2_Appendix_B_-_B44_-_Final_Geotechnical_Report.pdf

6200 Savoy Drive, Suite 600, Houston, TX 77063 Phone 832.251.8200 Fax 832.251.8201 info@kenallinc.com

July 17, 2018

US Army Corps of Engineers Fort Worth District, South Western Division 819 Taylor Street, Fort Worth, Texas, 76102

Attention: Mr. Erik J. Lagerquist

Re: Geotechnical Investigation Report

Buildings B44 Improvements JBSA Fort Sam Houston San Antonio, TX Kenall Project No. 8021 JBSA Work Order Nos.: 67061 Kenall Contract No.: W9126G-17-D-0017

Dear Mr. Lagerquist:

Kenall is pleased to submit this draft geotechnical investigation report for the above referenced project. The geotechnical investigation was conducted in accordance with the referenced JBSA work orders.

This report briefly describes the testing procedures employed in our investigation, presents the field exploration and laboratory testing results, and provides the conclusions and recommendations of our studies. An engineering analyses was performed to develop geotechnical design recommendations for this project, and to provide guidelines for the earthworks during construction.

We appreciate the opportunity to work with you on this phase of the project. If you have any question concerning the report or require additional information, please do not hesitate to contact the either of the undersigned.

Very Truly Yours, Kenall

Srujan Chikyala, P.E. Rajesh Tolikonda, P.E.

Project Manager Project Engineer

Copies Submitted: (1) mailto:info@kenallinc.com

Project No.8021

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 PROJECT DESCRIPTION

3.0 PURPOSE AND SCOPE

4.0 FIELD EXPLORATION

5.0 LABORATORY TESTING

6.0 GENERAL SUBSURFACE CONDITIONS

6.1 Soil Conditions

6.2 Groundwater Conditions

7.0 FOUNDATION ANALYSIS AND RECOMMENDATIONS

7.1 Drilled Straight Shaft Footings

7.2 Groundwater Control

8.0 GENERAL CONSTRUCTION RECOMMENDATIONS

8.1 Earthwork and Fill Compaction

8.2 Foundation Excavation and Construction

8.3 Site Drainage

8.4 Vegetation Control

8.5 Design Review

9.0 LIMITATIONS

LIST OF ATTACHMENTS

1.0 INTRODUCTION

This report presents the results and analysis of the geotechnical investigation performed by Kenall for the proposed improvements for building 44 in Joint Base San Antonio (JBSA), Fort Sam Houston (FSH) in San Antonio, Texas. The proposed project consists of various improvements on FSH base.

2.0 PROJECT DESCRIPTION

The project consisted of the evaluation of the existing buildings and proposing required improvements for Joint Base San Antonio in Fort Sam Houston. The proposed project consists of various improvements which included addition of elevator to building B44. Building B44 is located at 1400 E Grayson Street, San Antonio, Texas.

3.0 PURPOSE AND SCOPE

The purpose of this geotechnical study is to explore soil and groundwater conditions at the subject site, as well as performing field and laboratory tests to aid in engineering analyses for developing geotechnical design recommendations for the addition of stairs and CMU Wall for the proposed improvements of building B44.

The scope of services for this project includes, but is not necessarily limited to:

• Drilling two (2) deep soil borings up to a depth of 25 feet within the project area to evaluate the subsurface stratigraphy and groundwater conditions.

• Performing pertinent laboratory tests pursuant to prescribed American Society of Testing and Materials (ASTM) standards and local practices to evaluate the physical and engineering properties of subsurface soils.

• Reviewing the field and laboratory data and conducting engineering analyses to develop guidelines for foundation design and construction recommendations.

The scope of services did not include an environmental assessment for determining the presence or absence of wetlands, or hazardous or toxic materials in the soil, surface water, groundwater, or air that is on, below, or around the site. Any statements in this report or on the boring logs regarding odors, colors, and unusual or suspicious items or conditions are strictly for informational purposes. Prior to development of this site, an environmental assessment is advisable.

A geologic fault study to evaluate the possibility of surface faulting at this site was beyond the scope of this investigation. Should you desire a more detailed fault study, please contact us.

4.0 FIELD EXPLORATION

The field portion of this study was conducted on July 5th, 2018 and July 16, 2018 at the project location, which is in San Antonio, Texas. The subsurface soil conditions were explored by advancing and sampling two (2) soil borings. Borings B-1 and B-2 were drilled near building B2006. Boring B-1 was drilled to a depth of twenty five (25) feet and B-2 was abandoned at a depth of 4 feet due to the obstruction encountered below the existing ground surface. The approximate boring locations are shown on the Boring Location Plans, Plate No. 1, attached to the end of this report.

Sample depths, soil stratum descriptions, and soil classifications (Based on the ASTM Unified Soil Classification System) are presented on the attached Boring Logs, Plate Nos. 2. A key to the terms and symbols used on the boring logs are shown on Plate No. 3.

Undisturbed samples of the soil were obtained at two-foot intervals continuously to a depth ten (10) feet, and at five-foot intervals thereafter. Samples of the soil were obtained by means of three-inch outer diameter Shelby tube sampler. All undisturbed samples were extruded mechanically from the Shelby tubes in the field, wrapped in aluminum foil, and sealed in a plastic bag to prevent moisture loss and disturbance.

All the samples were transported to our geotechnical laboratory for examination, testing, and analysis.

In addition, disturbed samples of subsurface soils were obtained by using the split spoon sampling procedure in general accordance with ASTM D1586, Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils. The samples of subsurface materials were obtained by using a split spoon sampler with a two-inch outside diameter, 1.375-inch inside diameter, and a 21-inch barrel, as a part of standard penetration test. The test was performed by driving the sampler into the soil by repeated blows on a 140-pound hammer dropped thirty (30) inches. The number of hammer blows required to advance the sampler twelve (12) inches (after seating) was recorded for each standard penetration test on the appropriate boring log.

5.0 LABORATORY TESTING

The soil samples retained from the soil borings were examined and classified by either a geotechnical engineer or a senior technician in our laboratory. Laboratory tests were then performed on selected soil samples as directed by the geotechnical engineer in accordance with prescribed ASTM standards. The tests results were then used to evaluate physical and engineering properties of the soils so that recommendations for the engineering design and earthwork construction could be developed. The details of the laboratory tests and their respective ASTM Standards are provided in Table A below.

Table A: Details of Laboratory Tests Performed

Test Name Test Method

Moisture Content ASTM D 2216 Minus # 200 Sieve ASTM D 1140 Atterberg Limits ASTM D 4318A Unconsolidated and Undrained Triaxial ASTM D 2850

The tests noted above were performed to establish index properties and to aid in the proper classification of the subsurface soils. Detailed test results for each boring are shown on the attached Boring Logs, Plate Nos. 2.

6.0 GENERAL SUBSURFACE CONDITIONS

6.1 Soil Conditions

The site is relatively level. The surface consisted of grass at the time of our investigation. The specific subsurface stratigraphy determined by our field exploration is shown in detail on the attached boring logs. However, the stratigraphy can be generalized as follows:

Stratum I: For boring B-1: from the ground level to a depth of 6 feet and from 10 feet to a depth of 25 feet. The soil of this layer consists of brown, stiff to very stiff fat clay material.

Stratum II: For boring B-1: from a depth of 6 feet to a depth of 10 feet. The soil of this stratum consists of brown, hard sandy lean clay.

The information in this report summarizes conditions as found on the date the borings were drilled. The soil symbols indicated in the stratum descriptions and on the boring logs represent the Unified Soil Classification (ASTM D-2488) group symbols and are based primarily on visual observation and limited laboratory testing of the specimens recovered. Criteria for visual-manual classification of soil samples are given in Plate No. 4 attached to the end of this report.

6.2 Groundwater Conditions

Ground water was not encountered in both soil borings during the drilling operation.

It should be noted that the groundwater table may be expected to fluctuate with environmental variations, such as frequency and magnitude of rainfall, and at the time of year when construction begins.

Since groundwater level variations are anticipated, design drawings and specifications should incorporate such possibilities and provide for dewatering, as required, during construction.

7.0 FOUNDATION ANALYSIS AND RECOMMENDATIONS – CMU WALL AND

STAIR CASE

The current project consists of the improvements of building B44, which included addition of CMU wall and stair case. Based on subsurface conditions encountered in soil borings (Section 6.1) the onsite soils consist of high plasticity clays within the depth of moisture change (13 ft below natural grade). Based on our experience with general area we understand it is desired to support the new building on straight shafts.

A grading plan was not available during writing this report. For the purpose of writing this report we have assumed nominal cuts and fills are required to achieve the final grades. The following design recommendations were developed assuming the existing grade is within 2 ft of final grade.

7.1 Drilled Straight Shaft Footings

The proposed elevator can be supported on a foundation system comprised of cased straight shaft foundation bearing at a depth of twenty-five (25) feet below the existing grade. The footings may be sized for a net allowable bearing pressure of 6,000 pounds per square feet for dead plus sustainable live loads. The bearing pressure contains a factor of safety of 3.0 and can be increased 50 percent for total load conditions.

Caving of straight shaft will occur during construction due to presence of sand materials and calcareous nodules. In order to minimize the possibility of shaft caving during construction, contractor should be prepared to case the holes.

The concrete should be placed in a timely manner after drilling to minimize the potential for caving of the foundation soils. No footings should be poured without the prior approval of the Project Engineer, Architect or Owners Representative. A detailed settlement analysis was not authorized, nor performed, at this time since the exact size and locations of the footings are not known at this time. It is anticipated that the footings designed using the recommended allowable bearing capacity will experience small settlements that will be well within the tolerable limits for the proposed additions.

A detailed settlement analysis can be performed, if desired.

Foundation reinforcement design will be responsibility of project structural engineer

7.2 Groundwater Control

Groundwater was not encountered during drilling of both boring, B-1. Ground water was not encountered in both soil borings during the drilling operation. It should be noted that the groundwater table may be expected to fluctuate with environmental variations, such as frequency and magnitude of rainfall, and at the time of year when construction begins.

8.0 GENERAL CONSTRUCTION RECOMMENDATIONS

The recommendations in this report are based on the subsoil conditions encountered in the field exploration and laboratory testing. Due to the geological deposition in the Tule formation, variations could occur in the subsurface conditions within the site. If significant variation is noticed during construction, Kenall should be contacted to review and verify the conclusions presented in this report. During Construction, it is highly recommended to retain Kenall to perform construction inspections to make sure that the construction is performed as per the design.

8.1 Earthwork and Fill Compaction

The site should be stripped to suitable depths to remove any top soil and miscellaneous fill material. The exposed subgrade should then be proof-rolled with a 20-ton pneumatic roller or loaded dump truck to locate weak and soft areas. Any soft or loose material exposed should be removed and replaced with well-compacted material. The proof-rolling should be performed under the supervision of a licensed Professional Geotechnical Engineer.

Samples of the subgrade soil should be obtained prior to compaction operations for laboratory moisture/density testing (Proctor Tests). The tests will provide a basis for evaluating the in-place density requirements during compaction operations. A qualified soil technician should perform sufficient in-place density tests during the filling operations to verify that proper levels of compaction are being attained.

Prior to placing any new fill, the natural subgrade should be scarified to a minimum depth of six (6) inches. The scarified soils should then be recompacted to a minimum of 95 percent of the standard Proctor maximum dry density (ASTM D-698) and within the range of 1 percentage point below to 3 percentage points above the material’s optimum.

Any select, non-expansive fill (structural fill) used at the site should have a Liquid Limit less than 35 and a Plasticity Index between 10 and 20. The select fill material should be placed in maximum of eight (8) inch loose lifts and compacted to a minimum of 95 percent of the maximum dry density as per ASTM D-698. The moisture content should be within 1 percentage point below to 3 percentage points above material’s optimum.

Clay soils with plasticity index greater than or equal to 25 used as fill should be compacted to a dry density between 95 to 98 percent of standard Proctor maximum dry density (ASTM D-698) and within the range of 2 to 6 percentage points above the material’s optimum.

Sandy clay soils with a plasticity index less than 25 used a fill should be compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D-698) and within the range of 1 percentage point below to 3 percentage points above the material’s optimum.

8.2 Foundation Excavation and Construction

The foundation excavations should be inspected under the supervision of a licensed Professional Geotechnical Engineer to confirm that the bearing soils are similar to those encountered in our field exploration and that the foundation areas have been properly prepared. The geotechnical engineer should be immediately notified should any subsoil conditions be uncovered that will alter the conclusions and recommendations contained in this report. Further investigation and supplemental recommendations may be required if such a condition is encountered.

For drilled piers, the concrete should be placed in a timely manner after drilling to minimize the potential for caving of the foundation soils. Piers should not be poured without the prior approval of a licensed Professional Geotechnical Engineer. Prior to placement of concrete, the foundations excavations should be inspected to verify that:

1. The foundations bear in the proper bearing strata.

2. The drilled shaft is to the proper dimensions and reinforcing steel is placed as shown on the structural drawings.

3. The shaft has been drilled plumb within specified tolerances.

4. Excessive cutting, buildup of cutting, and any other soft compressible materials have been removed from the bottom of the excavations.

5. Any groundwater seepage observed in the pier excavations and sloughing of soils has been handled properly.

8.3 Site Drainage

It is recommended that site drainage be well developed. Drainage is important from the standpoint of soil stability. Surface water should be directed away from the foundation soils (use a minimum slope of 5% within 10 feet of foundation). No ponding of surface water should be allowed near the structure. Good drainage should be provided not only under the structure, but the general area should be well drained.

8.4 Vegetation Control

We recommend trees not to be closer than half the canopy diameter of mature trees from the structure, typically a minimum of 20 feet. This will minimize possible foundation settlement caused by the tree root systems.

8.5 Design Review

Review of the design and construction plans, as well as the specifications, should be performed by Kenall before release. The review is aimed at ensuring that the geotechnical design recommendations and construction criteria presented in this report have been properly interpreted. Design review is not within the scope of work authorized in this study. Should you elect to retain Kenall to perform a design review, additional fees would be applicable.

9.0 LIMITATIONS

This report is prepared for the exclusive use of USACE, JBSA FSH, and the design team for the specific application to the improvements of building B44 in Fort Sam Houston, Texas. Our report was prepared in accordance with 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 our subsurface exploration. The borings indicate subsurface conditions only at the specific locations and time, and only to the depths penetrated. The borings do not necessarily reflect strata variations that may exist in subsurface conditions within the site. The validity of the recommendations is based in part on assumptions about the stratigraphy made by the Geotechnical Engineer. Such assumptions may be confirmed only during earthwork and construction. If subsurface conditions during construction differ from those described here, the recommendations in this report must be reevaluated.

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 of this report are modified or verified in writing by Kenall. Kenall is not responsible for any claims, damages, or liability associated with subsequent interpretation of subsurface data, or reuse of the subsurface data or engineering analyses without expressed written authorization of Kenall.

LIST OF ATTACHMENTS

The following illustrations are attached to this report:

Plate No.

Boring Location Plan

Boring Logs

Symbols and Terms used on Boring Logs 3

Scale:

Not to Scale

Approved By:

SC

Prepared By:

RT

Approved By:

KP Borings Location Map

Building B44 (http://www.maps.google.com)

Project No.:

Plate No. 1 http://www.maps.google.com/

FAT CLAY(CH), with sand, brown, stiff to very stiff

SANDY LEAN CLAY(CL), with sand, brown, hard

FAT CLAY(CH), with sand, brown, very stiff

-with some calcareous nodules between 18 to 20 feet

SS-1

SS-2

SS-3

SS-4

SS-5

SS-6

U-7

SS-8

4.54.54.54.5

104.50.272

SHEET 1

SHEETS1OF

1. PROJECT

2. LOCATION (Coordinates or Station)

3. DRILLING AGENCY

4. LABORATORY TESTING AGENCY

5. DEPTH OF WATER

Fort Sam Houston N 29.4 E

TTL/Drash

Kenall Inc.

6. DEPTH OF HOLE

BORING LOG

Hole No. B-1

INSTALLATION

7. ELEVATION OF HOLE

8. DATUM FOR ELEVATION

9. ELEVATION OF GROUNDWATER

10. DRILLING DATE and TIME

11. CLASSIFICATION REFERENCE

12. ENGINEER

N/A

ASTM

JBSA FSH

COMPLETED: 7/5/18STARTED: 7/5/18

USACE SWD

ENG FORM: SWG 1836 BOR

G R

A P

H

IC

LO

G

B44

25 ft

TOD: N/A ft

TOD: 24-HR:

24-HR:

DISTRICT

D E

P T

H (f t)

E

LE

V A

T

IO

N (f

t) MATERIAL DESCRIPTION

S A

M P

LE

T

Y P

E

N U

M B

E R

R E

C O

V E

R Y

S P

T

N

P E

N E

T R

O M

E T

E R

(t sf

P

E N

E T

R O

M E

T E

R (t sf

P E

N E

T R

O M

E T

E R

(t sf

P

E N

E T

R O

M E

T E

R (t sf

P E

N E

T R

O M

E T

E R

(t sf

P

E N

E T

R O

M E

T E

R (t sf

M O

IS

T

U R

E C

O N

T E

N T

F

IN

E S

C O

N T

E N

T

P

LA

S T

IC

IT

Y

IN

D E

X

P

LA

S T

IC

LI

M

IT

LI

Q

U

ID

LI

M

IT

D R

Y U

N

IT

W T

(p cf

U N

C O

N F

IE

D

C O

M P

R E

S S

IO

N

(t sf

Penetration Resistance Blow per Foot

0.25 to 0.50

Very Dense

MHOL OH

CLASSIFICATION OF GRANULAR SOILS

CLAYEY GRAVELS, GRAVEL - SAND -

CLAY MIXTURES

15-30

HIGHLY ORGANIC SOILS

UNIFIED SOIL CLASSIFICATION CHART-ASTM 2487

2.0

ML

Water level encountered during drilling operations

KEY TO SOIL CLASSIFICATION

AND SYMBOLS

- having inclined planes of weakness that are slick and glossy in appearance

- containing shrinkage cracks, frequently filled with fine sand or silt; usually more or less vertical

- composed of thin layers of varying colors and texture

- composed of alternate layers of different soil types

- containing appreciable quantities of calcium carbonate

- containing appreciable quantities of ferrous materials

- having wide range in grain sizes and substantial amounts of all intermediate particle size

- predominantly of one grain size, or having a range of sizes with some intermediate size missing

Very Loose

CLEAN

GRAVELS

GROUNDWATER

PLASTICITY CHART

>30

Less than 0.25

Description

Gravel

6"

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

GRAVEL

AND

GRAVELLY

SOILS

>50

WELL-GRADED GRAVELS, GRAVEL -

SAND MIXTURES, LITTLE OR NO

FINES

0-15

15-35

35-65

65-85

No Recovery

0.50 to 1.00 Loose

Dense

ORGANIC SILTS AND ORGANIC

SILTY CLAYS OF LOW PLASTICITY

POORLY-GRADED SANDS,

GRAVELLY SAND, LITTLE OR NO

FINES

0.42

Medium Fine 4.7619.1

(APPRECIABLE

AMOUNT OF FINES)

(LITTLE OR NO FINES)

FINE

GRAINED

SOILS

0.002

Coarse

3/4"

CL-ML

CL

RELATIVE DENSITY-GRANULAR SOILS

or or

1.00 to 2.00

2.00 to 4.00

Hard 4.00 & Higher

0-2

CH

Clay

CONSISTENCY OF COHESIVE SOILS

Auger Sample

MORE THAN 50%

OF COARSE

FRACTION

PASSING ON NO.

4 SIEVE

LETTERGRAPH

Cobbles Silt or Clay

U.S. Standard Sieve Size (s)

Boulders

COARSE

GRAINED

SOILS

TYPICAL

DESCRIPTIONS

NOTE: DUAL SYMBOLS ARE USED TO INDICATE BORDERLINE SOIL CLASSIFICATIONS

Soft

Firm

WELL-GRADED SANDS, GRAVELLY

SANDS, LITTLE OR NO FINESCLEAN SANDS

3"

SILTS

AND

CLAYS

Very Stiff

INORGANIC SILTS, MICACEOUS OR

DIATOMACEOUS FINE SAND OR

SILTY SOILS

Very Soft

SAMPLE TYPES

Stiff

Blows Per Foot

MORE THAN 50%

OF MATERIAL IS

SMALLER THAN

NO. 200 SIEVE

SIZE

Water level after drilling operations

Slickensided

Fissured

Laminated

Interbedded

Calcareous Nodules

Ferrous Nodules

Well Graded

Poorly Graded

Grab Sample Shelby Tube Split Spoon

0-4

4-10

10-30

30-50

TERMS CHARACTERIZING SOIL STRUCTURE

20 40

ORGANIC CLAYS OF MEDIUM TO

HIGH PLASTICITY, ORGANIC SILTS

2-4

PEAT, HUMUS, SWAMP SOILS WITH

HIGH ORGANIC CONTENTS

Water level after 24 hours

MAJOR DIVISIONS

POORLY-GRADED GRAVELS,

GRAVEL - SAND MIXTURES, LITTLE

OR NO FINES

SILTY GRAVELS, GRAVEL - SAND -

SILT MIXTURES

SYMBOLS

(LITTLE OR NO FINES)

SANDS WITH

FINES

LIQUID LIMIT

LESS THAN 50

LIQUID LIMIT

GREATER THAN 50

LIQUID LIMIT

Unconfined Compressive Strength-TSF

MORE THAN 50%

OF MATERIAL IS

LARGER THAN

NO. 200 SIEVE

SIZE

SILTY SANDS, SAND - SILT

MIXTURES

CLAYEY SANDS, SAND - CLAY

MIXTURES

Fine 76.2152

10 40

Relative Density-%

85-100

P L A S T I C I T Y

I N D E X

Description

4-8

8-15

GRAVELS WITH

FINES

0.074

MORE THAN 50%

OF COARSE

FRACTION

RETAINED ON NO.

4 SIEVE

(APPRECIABLE

AMOUNT OF FINES)

INORGANIC CLAYS OF HIGH

PLASTICITY

Grain Size in mm

Coarse

Sand

Medium Dense

INORGANIC SILTS AND VERY FINE

SANDS, ROCK FLOUR, SILTY OR

CLAYEY FINE SANDS OR CLAYEY

SILTS WITH SLIGHT PLASTICITY

INORGANIC CLAYS OF LOW TO

MEDIUM PLASTICITY, GRAVELLY

CLAYS, SANDY CLAYS, SILTY

CLAYS, LEAN CLAYS

SAND

AND

SANDY

SOILS

SILTS

AND

CLAYS

Approved By: KP Prepared By: RT

Plate No.3Project No.