GETOTECH - TX ERFO SAM HOUSTON 215(1).pdf

SUBMITTED TO:

HDR Engineering, Inc.

1670 Broadway, Suite 3400 Denver, Colorado 80202

BY:

Shannon & Wilson, Inc.

1321 Bannock St., Suite 200 Denver, Colorado 80204

(303) 825-3800 www.shannonwilson.com

GEOTECHNICAL DESIGN REPORT

TX ERFO Sam Houston 215(1) Stubblefield Lake Road

WALKER COUNTY, TEXAS

November 2019

Shannon & Wilson No: 102477-001

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CONTENTS

1 Introduction

2 Project and Site Description

3 Subsurface Explorations and Laboratory Testing

3.1 Field Investigation

3.2 Geotechnical Laboratory Testing

4 Regional Geology and Subsurface Conditions

4.1 Regional Geology

4.2 Subsurface Conditions

4.3 Groundwater

4.4 Subsurface Variations

5 Geologic Hazard Evaluation

5.1 Seismic Hazards

5.2 Corrosion

6 Geotechnical Recommendations

6.1 Driven H Piles

6.1.1 Axial Design

6.1.2 Lateral Resistance

6.2 Abutment and Wingwalls

6.2.1 Subsurface Parameters

6.2.2 Analysis

6.2.2.1 Analysis Geometry and Parameters

6.2.2.2 Results

6.2.3 Wall Drainage

7 Construction Considerations

7.1 Driven Pile Installation

7.1.1 Wave Equation Analysis of Pile Driving

7.1.2 Pile Driving Equipment

7.1.3 Monitoring of Pile Driving

7.1.4 Dynamic Testing of Pile Driving

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7.2 Sheet Pile Installation

7.3 Earthwork and Grading

7.3.1 Excavation

7.3.2 Fill Placement and Compaction

8 Closure

9 References

Exhibits Exhibit 5‐1: Seismic Design Ground Motion Parameters

Exhibit 6‐1: Sheet Pile Wall Design Strength Parameters

Exhibit 6‐2: Sheet Pile Wall Geometry

Exhibit 6‐3: Sheet Pile Wall/Abutment Recommendations

Table Table 1: Geotechnical Parameters for Deep Foundation Design

Figures Figure 1: Vicinity Map

Figure 2: Site and Exploration Plan

Figure 3: Recommended P‐Multipliers for Laterally Loaded Groups of Piles of Shafts

Figure 4: Pile and Driving Equipment Data

Appendices Appendix A: Suburface Explorations

Appendix B: Laboratory Test Results

Appendix C: Drilling Photographs

Important Information iv

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ACRONYMS

AASHTO American Association of State Highway and Transportation Officials

ACI American Concrete Institute

ASTM ASTM International

CAPWAP Case Pile Wave Analysis Program

CBR California Bearing Ratio

CDOT Colorado Department of Transportation

FHWA Federal Highway Administration

FP‐14 Federal Standard Specifications for Construction of Roads and

Bridges on Federal Highway Projects, FP‐14

HDR HDR Engineering, Inc.

ISRM International Society for Rock Mechanics ksi Kips per Square Inch

LL Liquid Limit

LRFD Load and Resistance Factor Design

PGA Peak Ground Acceleration

PI Plasticity Index

PL Plastic Limit

SPT Standard Penetration Test

USCS Unified Soil Classification System

USGS United States Geological Survey

UU Unconsolidated‐Undrained

Geotechnical Design Report

102477-001 November 2019

1 INTRODUCTION

This report summarizes the results of our subsurface exploration and laboratory testing program and presents geotechnical design recommendations and construction considerations for the proposed Stubblefield Lake Road Bridge Replacement Project (the

Project) in Walker County, Texas (Figure 1). Our services were completed in general accordance with our Task Order Agreement No. 006/10001000038635 with HDR

Engineering, Inc. (HDR) dated March 6, 2019. Our conclusions and recommendations in this report are based on:

The limitations of our approved scope, schedule, and budget described in our contract;

Our understanding of the Project and information provided by HDR;

Subsurface conditions observed in the borings at the time our explorations were completed; and

The results of testing performed on samples collected from the explorations.

The objective of our geotechnical studies was to provide recommendations and construction considerations, as presented herein, for the proposed bridge replacement. The authorized scope of services was based on this objective and this report should not be used for other purposes without Shannon & Wilson, Inc.’s (Shannon & Wilson’s) review. If a service is not specifically indicated in this report, do not assume that it was performed.

2 PROJECT AND SITE DESCRIPTION

The Project is located in Walker County, Texas, north of Houston. Stubblefield Lake Road crosses over the north end of Lake Conroe where three adjacent existing northeast‐ southwest orientated bridges were damaged beyond repair during Hurricane Harvey

(Figure 2). The three existing bridges consist of a two‐lane roadway multi‐span bridge with two adjacent wooden pedestrian bridges located east and west of the main bridge. The existing vehicular traffic bridge is five spans and is approximately 132 feet long, 25 feet wide and constructed of prestressed concrete double tee beams founded on steel pipe piles. The wooden pedestrian bridges are approximately 179 feet and 153 feet in length for the western and eastern bridges, respectively, and are founded on timber piles. For the purposes of this report, the three bridges are referred to as a single structure and the northeast bridge abutment is assumed to be oriented north, and all subsequent directions reference this

ʹproject northʹ orientation.

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The proposed replacement bridge will consist of a 54‐foot‐wide, 186‐foot‐long, three‐span structure. The proposed bridge abutments and the interior bents will be founded on driven

H‐piles. We understand that the proposed roadway grade will be raised a maximum of

2 feet at the proposed bridge abutments. The bridge abutment and wingwalls will consist of driven steel sheet piles with the wingwalls extending parallel to the roadway approximately

98 and 90 feet back from the north and south abutment walls, respectively. Based on discussions with HDR, we understand the abutment walls and wingwalls within 25 feet of the abutments will retain soil with a 6‐foot maximum height with a 4‐foot‐wide horizontal bench and riprap armored slope that extends downward at a 2 horizontal:1 vertical (2H:1V).

Portions of the proposed abutment wall will require channel infilling and cuts to achieve this 6‐foot retaining wall height and horizontal bench. The wingwall heights greater than

25 feet from the abutment wall will be less than 4.5 feet in height.

3 SUBSURFACE EXPLORATIONS AND LABORATORY

TESTING

3.1 Field Investigation

Shannon & Wilson conducted a field exploration program on April 29 and 30, 2019, to explore subsurface conditions at the proposed replacement bridge location. The subsurface exploration program consisted of drilling and sampling four borings (designated SW‐01 through SW‐04), as shown in Figure 2.

Appendix A presents a discussion of the drilling and sampling procedures used to complete the borings. Appendix A also presents the individual exploration logs and an explanation of the symbols and terminology used. Photographs of the drilling locations are included in

Appendix C.

3.2 Geotechnical Laboratory Testing

Geotechnical laboratory tests were completed on selected samples retrieved from the borings to estimate index and engineering properties. Index tests included natural water content, grain size analysis, and Atterberg limits. Engineering properties tests included unconsolidated unconfined triaxial test, corrosion, proctor, and California Bearing Ratio

(CBR) testing. Laboratory test results and a discussion of the testing procedures are included in Appendix B. The natural water content, fines content, and Atterberg limits are also shown on the individual boring logs included in Appendix A.

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4 REGIONAL GEOLOGY AND SUBSURFACE

CONDITIONS

4.1 Regional Geology

A geologic map for Houston, Texas (Barnes and others, 1981) indicates that surficial soil near the Stubblefield Lake Road Bridge consists of Quaternary alluvium from the Jacinto

River as it enters Lake Paula (northern leg of Lake Conroe). Underlying the alluvium are the Pliocene Willis Formation and Miocene Fleming Formation, which are comprised of mostly clay, silt and sand, consistent with the borings completed at the site.

4.2 Subsurface Conditions

Boring SW‐01, the southern‐most boring, encountered sands with varying percentages of clay to a depth of 12 feet. Stiff clay with sand was then encountered to a depth of 22 feet overlying medium dense sand to the termination depth of the boring at a depth of 25 feet.

At the southern bridge abutment, boring SW‐02 encountered medium dense, silty sand and stiff clay with sand fill to a depth of 7 feet. Loose to medium dense, clayey sand and silty sand were then encountered to a depth of 27 feet where claystone was encountered to the termination depth of the boring at approximately 50 feet.

At the northern bridge abutment, boring SW‐03 encountered 7 feet of medium dense sand fill with varying percentages of clay and silt. Very loose to medium dense, clayey sand and sand with silt was then encountered to a depth of 32 feet. Claystone bedrock was encountered from 32 feet to the termination depth of the boring at approximately 60 feet.

The northern‐most boring, SW‐04, encountered approximately 3 feet of medium dense, silty sand fill overlying stiff, sandy clay to a depth of 12 feet. Loose to medium dense, clayey sand was then encountered to a depth of 22 feet overlying medium dense sand with silt to the termination depth of the boring at 25 feet.

4.3 Groundwater

During drilling, groundwater was encountered in borings SW‐01 through SW‐04 at depths ranging from about 10.5 to 18 feet below the existing ground surface (Elevation 196 to

188 feet). The groundwater level at the time of drilling is noted on each boring log included in Appendix A. Groundwater fluctuations are likely and will depend on seasonal variations, local precipitation and runoff, and other factors, but will primarily be influenced by water levels in Lake Conroe and flood events.

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4.4 Subsurface Variations

The explorations were performed to evaluate subsurface conditions at the Project site. Our observations are specific to the locations, depths, and times noted on the logs and may not be applicable to all areas of the site. No amount of explorations or testing can precisely predict the characteristics, quality, or distribution of subsurface and site conditions.

Potential variation includes, but is not limited to:

The conditions between explorations may be different.

The passage of time or intervening causes (natural and manmade) may result in changes to site and subsurface conditions.

If conditions different from those described herein are encountered during construction, we should review our description of the subsurface conditions and reconsider our conclusions and recommendations.

5 GEOLOGIC HAZARD EVALUATION

5.1 Seismic Hazards

The Houston area is in an area of low potential for damaging earthquakes. Unfortunately, it is not possible to accurately estimate the timing or location of future earthquakes. Based on a recent geologic map by the U.S. Geological Survey (USGS), the Project is located within the gulf‐margin normal faults (Wheeler, 1999). However, the fault belt shows only sparse, low‐ magnitude seismicity within the fault. Therefore, in our opinion, the potential for ground surface fault rupture is low.

Liquefaction may occur in loose, saturated, cohesionless soils when subjected to earthquake ground shaking. Based on the subsurface conditions encountered at the site and the relatively low peak ground acceleration (PGA) for this area, it is our opinion that the risk of liquefaction is low.

Using the American Association of State Highway and Transportation Officials (AASHTO)

Load and Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO, 2017) criteria, and based on subsurface conditions encountered in our borings at the proposed bridge (assuming that similar conditions are present from the maximum depth of our boring to a depth of 100 feet), Site Class D is recommended for the proposed bridge.

Ground motion parameters were determined for the Project site using the USGS AASHTO

2009 Web Service Documentation Web Application (USGS, 2009) and procedures

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102477-001 November 2019 recommended by AASHTO (2017). Exhibit 5‐1 presents recommended seismic design ground motion parameters.

Exhibit 5-1: Seismic Design Ground Motion Parameters

Design Parameter Value

Site Class D

Short-period Spectral Acceleration, SS 0.052 g

Long-period Spectral Acceleration, S1 0.024 g

Site Factor, Fpga 1.6

Site Factor, Fa 1.6

Site Factor, Fv 2.4

Peak Design Spectral Acceleration, AS 0.037 g

Short-period Design Spectral Acceleration, SDS 0.083 g

Long-period Design Spectral Acceleration, SD1 0.057 g

TO 0.138 sec.

TS 0.69 sec.

NOTES:

Based on AASHTO 2009 Guide Specifications.

g = gravity; sec. = seconds

5.2 Corrosion

The soil and bedrock materials in Texas can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, samples of clayey sand and claystone bedrock were tested for pH, resistivity, water soluble sulfates, and chlorides. The results are presented in Table B‐1 in Appendix B.

The resistivity measured in the samples ranged from 820 to 4,000 ohm‐centimeters. Based on correlations developed by Roberge (2012), these values suggest an extremely corrosive to moderately corrosive subsurface. FHWA (2016) recommends sacrificial steel for piles in fresh water be designed assuming a corrosion rate of 0.002 inches per year.

The concentration of water‐soluble sulfates measured in the samples was 0.01 percent by weight (100 parts per million). Based on classifications as defined by American Concrete

Institute (ACI) ACI‐318‐14 (ACI, 2014), these test results suggest a negligible degree of sulfate attack on concrete exposed to site soils (exposure class S0).

We recommend that a specialist in corrosion‐resistance design review the results included in

Table B‐1 to determine actual construction materials and methods based on the test results.

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6 GEOTECHNICAL RECOMMENDATIONS

As discussed in Section 2.0, we understand the proposed bridge will consist of a three‐span structure founded on driven piles. The borings indicate that bedrock was encountered at a depth of approximately 27 feet and 32 feet below ground surface in borings SW‐02 and SW‐

03 (Elevation 179 and 174 feet, respectively). In our opinion, driven piles are a cost‐effective and appropriate foundation system for the bridge based on the subsurface conditions encountered at the site.

Drilled shafts were considered as an alternative to driven piles; however, due to constraints of overwater construction with drilled shafts, HDR indicated that drilled shafts were not the preferred alternative and are not discussed herein.

6.1 Driven H Piles

We understand that driven H‐piles will be used to support the proposed abutments and bents. The design criteria presented herein were developed based on recommendations presented in the AASHTO LRFD Bridge Design Specifications (AASHTO, 2017). In addition, the 2016 Federal Highway Administration (FHWA) Manual “Design and

Construction of Driven Pile Foundations” (FHWA, 2016) was used to supplement driven pile design procedures and develop the axial resistance parameters.

6.1.1 Axial Design

Driven piles will need to extend through overburden soils and develop capacity in the bedrock. We recommend using a factored compressive axial resistance of 18 kips per square inch (ksi) times the cross‐sectional area of the steel H‐piles (accounting for any loss of section as a result of corrosion and/or use of sacrificial steel), assuming 50 ksi steel. The geotechnical resistance should be confirmed by dynamic testing (i.e., the nominal geotechnical resistance indicated by the dynamic testing multiplied by the resistance factor should be greater than or equal to the factored structural axial load on the pile). AASHTO

(2017) recommends a strength limit resistance factor of 0.65, assuming dynamic testing is completed as described in Section 7.1.4. A resistance factor of 1.0 is recommended for the service limit state. A resistance factor of 1.0 is recommended for the extreme limit states, except a resistance factor of 0.8 is recommended for uplift.

Pile installation may encounter hard driving within the bedrock. As such, we recommend that a protective rock tip be welded to the end of each pile to reduce the possibility of pile damage during driving. Depending on the pile section selected by the designer and driving system selected by the contractor, we anticipate that bedrock penetrations of H‐piles will be

Geotechnical Design Report

102477-001 November 2019 approximately 5 to 15 feet in the rock. For cost estimating purposes, we recommend assuming a bedrock penetration on the order of 15 feet. The structural engineer should confirm a minimum penetration that considers the required lateral resistance and uplift. To further estimate pile penetration and select a hammer that will not overstress the piles, we recommend completing a wave equation analysis (see Section 7.1.4). A resistance factor of

1.0 is appropriate for the structural resistance of the pile during driving. Further discussion on wave equation analysis and pile installation is provided in Section 7.1.

A minimum spacing of three widths/diameters (center‐to‐center) for axial loads is recommended to reduce the stress overlap between the adjacent piles. If this condition cannot be met, a reduction in axial resistance parameters (i.e., consideration of group effects) may be necessary. Lateral resistance of driven piles is discussed in Section 6.1.2. If battered piles are to be implemented for lateral loading, we recommend that the pile be battered no flatter than 4V:1H.

For properly designed and installed piles, we estimate settlement to be on the order of

½ inch. This settlement value does not include elastic compression of the pile under service conditions. Differential settlement across the bridge would be expected to be about

50 percent of this value. About 75 percent of the settlement is anticipated to occur as the load is applied with the remaining settlement occurring within the first year following construction. Based on the proposed nominal grade raises and the granular nature of the subsurface materials, we do not anticipate long‐term settlement that could result in downdrag loads to develop on the piles.

6.1.2 Lateral Resistance

We recommend that lateral resistance be determined based only on the deep foundation elements. To determine the lateral resistance of an individual driven pile, and the deflection, shear, and moment along the pile, we have provided input parameters for the commercial software LPILE by Ensoft, Inc. (2017) in Table 1. Group action can be analyzed using p‐multipliers within LPILE. P‐multipliers (i.e., group reduction factors) for loading perpendicular and parallel to a line of piles are presented on Figure 3.

6.2 Abutment and Wingwalls

We understand that retaining walls will be located on either side of the bridge and on both sides of the roadway to accommodate a grade raise. Initially, vinyl sheet piles were considered for the Project but based on a deflection tolerance of less than 2 inches at the top of the wall, the vinyl sheet piles would require anchors for the full length of the wall. As a result, stiffer steel sheet piles were selected for the Project. The sheet pile retaining wall

Geotechnical Design Report

102477-001 November 2019 design recommendations presented in the following sections are based on design guidelines presented in AASHTO LRFD Bridge Design Specification.

6.2.1 Subsurface Parameters

The sheet pile walls were designed using force‐moment equilibrium methods, with factored active and passive earth pressure parameters. Exhibit 6‐1 summarizes the total weight and long‐term drained shear strength for each soil/rock layer.

Exhibit 6-1: Sheet Pile Wall Design Strength Parameters

Location

Elevation

Representative Soil/Rock Description

Total Unit Weight (pcf)

Drained Shear Strength

Top Bottom Friction Angle

(deg) Cohesion

(psf)

South Abutment Wingwall

(SW-02)

208 199 Wall Backfill Material 135 34 0

199 190 Loose to Medium Dense, Clayey Sand 120 30 0

190 179 Very Loose to Loose, Silty and Clayey Sand 115 28 0

< 179 Claystone 130 0 3,000

North Abutment Wingwall

(SW-03)

208 199 Wall Backfill Material 135 34 0

199 174 Very Loose to Medium Dense, Clayey Sand to Sand

115 28 0

< 174 Claystone 130 0 3,000

NOTE:

deg = degrees; pcf = pounds per cubic foot; psf = pounds per square foot

6.2.2 Analysis

The proposed sheet pile walls were analyzed using force‐moment equilibrium methods, with the active and passive earth pressure parameters using the software developed by the

U.S. Army Corps of Engineers CWALSHT (1990). The software also estimates defections.

6.2.2.1 Analysis Geometry and Parameters

For our analysis, HDR provided cross sections every 25 feet along each abutment/wingwall.

We analyzed select cross sections based on (a) retained fill height, (b) the overall slope angle in front of the wall, (c) the proposed riprap conditions, and (d) the subsurface conditions encountered in borings SW‐02 and SW‐03. Exhibit 6‐2 provides the sheet pile wall geometry that we used in design.

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Exhibit 6-2: Sheet Pile Wall Geometry

Loading Case

Sheet Pile Wall Section

Analyzed Cross

Section

Exposed Wall

Height (ft)

Top Wall Elevation

(ft)

Bench Elevation

(ft)

Bottom Slope

Elevation

(ft) Front Slope Conditions

1 Side Wall STA 200+75

4.5 208.0 203.5 200.5 10H:3V slope (16.7 deg.)

2 Side Wall

STA

201+00 6.0 208.0 202.0 200.0

4-foot bench, 2H:1V rip rap slope (26.6 deg.)

STA

101+75

6.0 208.0 202.0 198.5 4-foot bench, 2H:1V rip rap slope (26.6 deg.)

South

Abutment

STA

101+75

6.0 208.0 202.0 179.0

4-foot bench, 2H:1V rip rap slope (26.6 deg.)

North

Abutment

STA

201+25 6.0 208.0 202.0 179.0 4-foot bench, 2H:1V rip rap slope (26.6 deg.)

NOTES:

deg. Degrees; ft = feet; H:V = horizontal:vertical; STA = Station

We calculated lateral earth pressures assuming the sheet pile walls will be infilled with

Backfill Material identified in Section 704.03 of Federal Standard Specifications for

Construction of Roads and Bridges on Federal Highway Projects, FP‐14 (FP‐14). The parameters assume the walls will deflect sufficiently to achieve active conditions. In accordance with AASHTO (2017) a load factor of 1.5 was applied to active earth pressures and a resistance factor of 0.75 was applied to passive earth pressures.

Additionally, we assumed that the walls will incorporate weep holes or an equivalent drainage system such that unbalanced groundwater will not accumulate in the retained fill

(see Section 6.2.3). Accordingly, our design recommendations do not include unbalanced hydrostatic pressure above the base of the exposed height behind the walls. For a rapid drawdown analysis, we assumed groundwater within the wall backfill remains at Elevation

202 feet, and the lake water level is dropped to Elevation 193 feet (half of the total channel depth) and 179 feet (bottom of channel).

Surcharge loads from motor vehicles/traffic and construction equipment will induce additional lateral loads on retaining walls. For our analysis, we assumed a live load of

250 psf.

HDR selected a 12‐inch sheet pile depth for design. To estimate the cantilevered wall deflections, we assumed a minimum sheet pile moment of inertia of 184 in4.

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6.2.2.2 Results

Exhibit 6‐3 summarizes recommended minimum tip elevations and estimated deflections, and the maximum factored bending moment for each wall section. Based on discussions with HDR, the deflection criteria at the top of the wingwalls is required to be less than or equal to 2 inches. If a sheet pile with different stiffness is selected, the cantilevered wall deflections should be re‐evaluated. For the cantilevered abutment walls, we estimated a deflection greater than 2 inches, therefore we assume that sheet piles at the abutments will be tied to the pile cap. Exhibit 6‐3 provides the factored load that will be transferred to the pile cap for the anchored system at the abutments.

Exhibit 6-3: Sheet Pile Wall/Abutment Recommendations

Loading Case

Exposed Wall Height

(ft) Sheet Pile Wall

Section

Factored Bending Moment

(kip-ft)

Top of Wall

Deflection (I=184in4)

(inches)

Minimum Sheet

Pile Tip Elevation

(ft)

Factored Load

Transferred to Pile Cap

(lbs/ft)

1 ≤ 4.5 Cantilevered 20 0.8 187 -

2 4.5 to 6.0 Cantilevered 33 2.0 183 -

3 6.0 South Abutment Tied to Pile Cap 6 - 184 1,500

4 6.0 North Abutment Tied to Pile Cap

6 - 179 1,500

NOTES:

A minimum sheet pile moment of inertia of 184 in4 was assumed to achieve a deflection of less than or equal to 2 inches at the top of the wall.

ft = feet; kip-ft = kip-feet; lbs/ft = pounds per foot

6.2.3 Wall Drainage

The earth pressure parameters provided for the proposed retaining walls assume a free‐ draining backfill condition. As such, it will be important to control surface water and to provide drainage measures that reduce the potential for water to accumulate behind walls, particularly considering the proximity of walls to Lake Conroe.

If the wall backfill is not allowed to drain, a rapid drawdown condition could occur following flood events, i.e., water could be trapped in the backfill after flood waters recede.

As such, we recommend that weep holes be included within sheet pile wall to keep water from being trapped in the backfill. We recommend the placement of an 18‐inch, free draining granular drainage layer behind the wall that hydraulically connects to the weep holes.

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Surface water behind the wall should not be allowed to discharge directly into the wall backfill materials. In addition, water should not be allowed to discharge or pond around retaining structures.

7 CONSTRUCTION CONSIDERATIONS

7.1 Driven Pile Installation

7.1.1 Wave Equation Analysis of Pile Driving

In accordance with Section 551 of FP‐14 (FHWA, 2014), a wave equation analysis of pile driving (WEAP) should be completed using the selected pile type and the Contractor’s pile driving equipment. Information required for such an analysis is presented on Figure 4. The wave equation analysis should be completed prior to the start of driving production piles at the site. The WEAP analysis should be used to establish preliminary driving criteria and to confirm that the Contractor’s selected hammer is capable of installing the pile and mobilizing adequate axial resistance without damaging the pile. Production driving criteria should be determined by dynamic testing (see Section 7.1.4) in accordance with Section 551 of FP‐14 (FHWA, 2014).

7.1.2 Pile Driving Equipment

Fixed‐lead pile driving equipment is recommended for driving the piles. The use of hanging or swinging leads is not recommended unless they are constructed to be held in a fixed position during driving operations. Similar to Section 551.05 of FP‐14 (FHWA, 2014), the recommended ranges of hammer energies for driving the piles may be determined using a WEAP. All pile‐driving equipment should be designed, constructed, and maintained in a manner suitable for the work to be accomplished for this Project. Per FP‐14 (2014), the

Contractor will be responsible for installing the piles, including determining the appropriate hammer‐cushion system to drive the piles to the depths required without damaging the piles during installation.

7.1.3 Monitoring of Pile Driving

Pile driving should be monitored by taking a continuous driving record of each pile. For this purpose, the Contractor should mark the pile in 1‐foot increments. During re‐strike (if required), additional 1‐inch increments between the 1‐foot marks would be necessary.

The pile‐driving record should be complete. The form should have spaces to record hammer stroke (diesel hammers), blows per foot, time, date, reasons for delays, and other

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102477-001 November 2019 pertinent information. In addition, the record should include tip elevation, driving criteria, and initials of inspectors making final acceptance of the pile. The pile‐driving records should be reviewed on a daily basis. For this purpose, we recommend that an experienced and qualified geotechnical engineer familiar with the subsurface conditions at the Project site be assigned to assist in construction monitoring.

It is often difficult to estimate the energy delivered by diesel hammers with visual observation. The Saximeter, developed by Pile Dynamics, Inc., can be used to record hammer strokes and provide an estimate of the driving energy of diesel hammers. If the

Contractor selects a diesel hammer, we recommend a Saximeter be considered by the inspection staff to monitor pile driving.

7.1.4 Dynamic Testing of Pile Driving

Dynamic testing during pile driving is required by AASHTO (2017) to confirm that piles are not damaged during installation and is specified in Section 551 of FP‐14 (FHWA, 2014).

Dynamic testing should also be completed to confirm adequate geotechnical axial resistance.

The resistance factor of 0.65 (on the resistance determined from dynamic testing) recommended in Section 6.1.1 assumes that dynamic pile testing with signal matching, e.g., Case Pile Wave Analysis Program (CAPWAP), is completed on a minimum of two piles, but no less than 2 percent of the production piles at the bridge, and that production driving criteria are developed based on the results of the dynamic testing. As a result, and as presented in Section 551.13 of FP‐14 (FHWA, 2014), the Contractor’s pile driving schedule should consider that acceptance criteria for production piles will not be available prior to completing dynamic testing.

7.2 Sheet Pile Installation

We anticipate that the steel sheet piles can be installed with a vibratory hammer or impact hammer. Considering the ground conditions encountered at the site, in our opinion, sheet pile installation will encounter easy to moderate driving conditions in the overburden clayey sands. We anticipate that steel sheet piles can be driven to the minimum tip elevations shown on Exhibit 6‐3, which are above the anticipated top of bedrock elevation.

As such, we do not anticipate difficult driving conditions due to the claystone bedrock.

7.3 Earthwork and Grading

Earthwork, including site preparation, embankment construction, placement of fill, and subgrade preparation, should conform to the requirements provided in Division 200 of the

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Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP‐14 (2014).

7.3.1 Excavation

The fill and native soil can likely be excavated using conventional excavating equipment, such as a rubber‐tired backhoe or tracked hydraulic excavator.

7.3.2 Fill Placement and Compaction

Wall backfill should meet the requirements of Backfill Material (FP‐14 704.03) as modified below. These modifications include a maximum fines content of 35 percent, a maximum

Plasticity Index of 10, and be free of organics, debris, and other deleterious material. If a drainage layer at the face of the wall is not used, as discussed in Section 6.2.3, we recommend the backfill consist of FP‐14 704.01 Foundation Fill or 704.07 Select Borrow.

Silty and clayey sand onsite materials excavated throughout the Project may be used as wall backfill if the material meets the minimum requirements of FP‐14 Backfill Material. Based on our laboratory testing, the onsite subgrade materials encountered at the abutment locations may be suitable for use as backfill of the new walls. Some excavated materials may have high fines contents and should only be used as common fill (e.g., landscaping areas).

Fill should be placed in uniform, horizontal layers with the loose lift thickness not exceeding

8 inches for heavy, self‐propelled compactors, or 4 inches for hand‐operated mechanical compactors. The appropriate lift thickness will depend on the Contractor’s equipment and the moisture content and quality of the Backfill Material. Compaction of backfill adjacent to walls can result in higher lateral earth pressures against the walls. Therefore, small equipment that is hand‐operated should be required within a line extending upward from the base of the structure at 0.5H:1V, to a maximum horizontal distance of 5 feet from the face of the wall to reduce this potential.

Modified Backfill Material should be moisture conditioned within 2 percentage points of the optimum moisture content and to at least 95 percent of the maximum dry density as determined by AASHTO T99 (standard Proctor compaction effort) in accordance with FP‐14

Section 208. It should be noted that as the amount of fines increases in the Modified Backfill

Material (portion of soil particles passing a U.S. Standard No. 200 sieve), soil becomes more sensitive to small changes in moisture content, and adequate compaction becomes more difficult to achieve.

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8 CLOSURE

This report has been prepared for the exclusive use of HDR and Central Federal Lands

Highway Division for the purpose of providing geotechnical recommendations for the

Stubblefield Lake Road Bridge project. This geotechnical design report should not be used without our approval if any of the following occurs:

Assumptions stated in this report have changed.

Project details change or new information becomes available such that our analysis and recommendations may be affected.

A substantial period of time has passed since the date of this report.

If any of these occur, we should be retained to review the applicability of our analyses and recommendations.

Within the limitations of scope, schedule and budget, the analyses, conclusions and recommendations presented in this report were prepared in accordance with generally accepted professional geotechnical and geological principles and practice in this area at the time this report was prepared. We make no other warranty, either express or implied.

Shannon & Wilson, Inc. has prepared “Important Information about Your Geotechnical

Report,” to assist you and others in understanding the use and limitations of our reports.

Geotechnical Design Report

102477-001 November 2019

9 REFERENCES

American Concrete Institute (ACI), 2014, Building code requirements for structural concrete and commentary, Farmington Hills, Mich., ACI 318‐14.

American Association of State Highway and Transportation Officials (AASHTO), 2017, AASHTO LRFD bridge design specifications, Customary U.S. units, 8th edition:

Washington, D.C., American Association of State Highway and Transportation

Officials.

Barnes, V.E., Shell Development Co., Amerada Petroleum Corp., Brown, T.E., Waechter, N.B., and Dillon, R.L, 1974, rev. 1981, Geologic atlas of Texas, San Antonio sheet

(revised 1982): University of Texas at Austin, Bureau of Economic Geology, Geologic Atlas of Texas 29, scale 1:250,000.

Ensoft, Inc., 2017, LPILE 2017, A Program for Analyzing Stress and Deformation of

Individual Piles or Drilled Shafts Under Lateral Load, Austin, Texas.

Roberge, P.R., 2012, Handbook of corrosion engineering, Second Edition: McGraw‐Hill, New York, New York.

U.S. Army Corps of Engineers, Water Experiment Station Information Technology Library, 1990, CASE / GCASE Program CWALSHT, Design/Analysis of Sheet‐Pile Walls By

Classical Methods, Program X0031, Version 1.0.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), 2016, Design and Construction of Driven Pile Foundations. Publication No.

FHWA‐NHI‐16‐009. Available from:

https://www.fhwa.dot.gov/engineering/geotech/pubs/gec12/nhi16009_v1.pdf.

U.S. Department of Transportation (USDOT), Federal Highway Administration (FHWA), 2014, Federal standard specifications for construction of roads and bridges on

Federal Highway projects, FP‐14 English Units: U.S. Department of

Transportation and Federal Highway Administration, available from http://flh.fhwa.dot.gov/resources/pse/specs/.

U.S. Geological Survey (USGS) AASHTO 2009 Web Service Documentation Web

Application (USGS, 2009). Available from:

https://earthquake.usgs.gov/ws/designmaps/

Wheeler, R.L., compiler, 1999, Fault number 924, Gulf‐margin normal faults, Texas, in

Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 05/07/2019 12:58

PM.

Geotechnical Design Report

Driven Pile

Parameters 3

Location Top Bottom Top Bottom

Pile Factored Axial

Resistance Lpile

Soil Type

Total Unit

Weight 8

Drained Friction Angle

Undrained Shear

Strength (Boring ID) (ft) (ft) (ft) (ft) (ft) (ksi) (pcf) (deg) (psf)

0 7 206 199 Medium Dense Silty Sand - Sand (Reese) 120 30 -

7 16 199 190 Loose to Medium Dense Clayey Sand - Stiff Clay w/o

Free Water 120 30 -

16 27 190 179 Very Loose to Loose Silty and Clayey Sand - Sand (Reese) 115 28 -

27 37 179 169 CLAYSTONE: very weak 18 Stiff Clay w/o Free Water 125 - 3,000

37 50 169 156 CLAYSTONE: very weak 18 Stiff Clay w/o Free Water 130 - 8,000

0 7 206 199 Medium Dense Silty and Clayey Sand - Sand (Reese) 120 30 -

7 32 199 174 Very Loose to Medium Dense Clayey Sand to Sand with Silt - Sand (Reese) 115 28 -

32 42 174 164 CLAYSTONE: very weak 18 Stiff Clay w/o Free Water 125 - 3,000

42 60 164 146 CLAYSTONE: very weak 18 Stiff Clay w/o Free Water 130 - 8,000

NOTES:

5 The LPile parameters shown are for a horizontal ground surface. Sloping ground surface modifications should be included per Ensoft, Inc.'s recommendations for Lpile.

8 For design below the water table, the effective unit weight (' = - w , w = 62.4 pcf) must be used.

ksf = kips per square foot; ksi = kips per square inch; psf = pounds per square foot; pcf = pounds per cubic foot; deg = degrees; ft = foot

2 The groundwater elevation is based on the observerved groundwater at the time of drilling. Design groundwater elevations should correspond to lake flood elevation.

Table 1 - Geotechnical Parameters for Deep Foundation Design

Groundwater

Elevation 2 Representative Soil/Rock

Description

LPILE PARAMETERS FOR

LATERAL ANALAYSIS 4, 5, 6, 7

Elevation 1

Depth Below Existing Ground

Surface

South Abutment

(SW-02)

North Abutment

(SW-03)

3 Pile factored axial resistance is based on typical achievable geotechnical resistance without damaging the pile during driving, assuming a yield stress of 50 ksi.

1 Ground surface elevations provided by HDR.

4 The LPile parameters shown are for a single shaft or pile. For group effects, see Figure 3 for recommended p-multipliers.

6 A resistance factor of 1.0 should be used for lateral analyses.

7 The lateral loading analysis should consider the potential for loss of material from flooding and scour.

102477-001 Page 1 of 1 102477_T1 - Deep Foundations - 11/12/2019

VICINITY MAP

FIG. 1

TX ERFO Sam Houston 215(1) Stubblefield Lake Road Walker County, Texas

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

November 2019 102477-001

F i l e n a m e

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C

F L

T

X

S t u b b l e f D r a f t i n g

F i g u r e d w g

D a t e o g i n d k m

MT

0 2 4

Approximate Scale in Miles

Amarillo

Dallas

Houston San Antonio

El Paso Project

Location

Texas

PROJECT

LOCATION

New Waverly

P o s s u m

W l k

R d

C o u n t y

C o u n t y i n

SITE AND EXPLORATION PLAN

FIG. 2

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

TX ERFO Sam Houston 215(1) Stubblefield Lake Road

Walker County, Texas

Approximate Scale in Feet

100 200

November 2019 102477-001

F i l e n a m e

I E

F D

E N s

C

F

T

X

S t u b b l e f D r a f t i n g

F i g u r d w g

D t e o g i n d k m

MT

1. Map adapted from aerial imagery provided by Google Earth

Pro, reproduced by permission granted by Google Earth ™

Mapping Service.

NOTES

Geotechnical Boring Designation and

Approximate Location

LEGEND

SW-01

SW-01

SW-02

SW-03

SW-04

102477-001_Fig 3 - P-Multipliers

NOTE:

Reference: AASHTO LRFD Bridge Design Specifications (2012) - Table 10.7.2.4-1 (from Hannigan et al., 2006)

The P-multipliers provided above were developed for vertical piles/shafts only. Batter piles provide a much stiffer response than vertical piles/shafts when loaded in the direction of the batter.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

1.20

2 3 4 5 6 p -M u lt ip li er

S/B

1st Row 2nd Row 3rd Row or Higher

Geotechnical and Environmental Consultants

SHANNON & WILSON, INC.

RECOMMENDED P-MULTIPLIERS

FOR LATERALLY LOADED

GROUPS OF PILES OR SHAFTS

2nd Row

3rd Row

1st Row

4th Row

Load Direction

Trailing Rows

Leading Row For Load acting in this direction, use p-Multiplier of the 1st Row

S

B

November 2019 102477-001

FIG. 3

TX ERFO Sam Houston 215(1)

Walker County, Texas

11/13/2019-102477-001_AA A-i

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Appendix A: Subsurface Explorations

Appendix A

Subsurface Explorations

CONTENTS

A.1 Introduction ........................................................................................................................... A‐1

A.2 Explorations ........................................................................................................................... A‐1

A.2.1 Soil and Rock Classification System ...................................................................... A‐1

A.2.2 Standard Penetration Test (SPT) ............................................................................ A‐2

A.2.3 Shelby Tube Sampling ............................................................................................. A‐2

A.2.4 Pocket Penetrometer ................................................................................................ A‐2

A.2.5 Bulk Sampling .......................................................................................................... A‐3

Figures Figure A‐1: Soil Description and Log Key

Figure A‐2: Rock Classification and Log Key

Figure A‐3 through A‐6: Log of Borings SW‐01 through SW‐04

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A.1 INTRODUCTION

Shannon & Wilson, Inc.’s (Shannon & Wilson’s) field exploration program was conducted on April 29 and 30, 2019, and consisted of drilling four borings, designated as SW‐01 through SW‐04 at the locations shown on Figure 2. Photographs of boring locations are provided in Appendix C. The methods used to conduct the field exploration program are described below.

A.2 EXPLORATIONS

The borings were coordinated (including subcontractor coordination and utility locates) and observed by Shannon & Wilson. Individual boring logs are presented in Figure A‐2. These exploration logs represent our interpretation of the contents of the field logs and select results of laboratory testing. The borings were drilled by Envirotech Drilling Services, Inc.

(Envirotech) of Houston, Texas (under subcontract to Shannon & Wilson) using a truck‐ mounted CME 75 drill rig. The borings were advanced to depths ranging from 25.5 to

59.9 feet. Boring SW‐03 was advanced using 4‐inch diameter solid‐stem‐auger techniques.

At 20 feet, Envirotech switched to mud rotary drilling techniques. Borings SW‐01 and

SW‐02 and SW‐04 were advanced using 8‐inch diameter hollow‐stem‐auger drilling techniques. On completion of drilling, the borings were backfilled with cuttings and repairs to the existing pavement were made with quikcrete concrete.

A.2.1 Soil and Rock Classification System

During exploration, our representative collected samples and prepared field logs of the explorations. Soil classification for this project was based on ASTM International (ASTM)

Designation: D2487, Standard Practice for Classification of Soils for Engineering Purposes

(Unified Soil Classification System), and ASTM Designation: D2488, Standard Practice for

Description and Identification of Soils (Visual‐Manual Procedure). The Unified Soil

Classification System is summarized in Figure A‐1.

The bedrock encountered in the borings was found to be very dense and hard when considered as a lithified soil material. However, when compared with other types of bedrock using the International Society for Rock Mechanics (ISRM) classification of rock strength, the rock resembles a very low strength rock. Therefore, for completeness, the boring logs contain dual descriptions of the bedrock using the Unified Soil Classification

System (USCS) and rock classification shown in Figure A‐2, where appropriate.

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A.2.2 Standard Penetration Test (SPT)

Disturbed samples were obtained in the borings in general accordance with the Standard

Penetration Test (SPT) (ASTM Designation: D1586). The SPT consists of driving a 2‐inch outside diameter, 1.375‐inch inside diameter split‐spoon sampler a distance of 18 inches with a 140‐pound hammer free‐falling a distance of 30 inches. An automatic hammer system was used to advance the samplers. During sampling, the Shannon & Wilson field representative recorded the number of blows for each 6‐inch increment of penetration and summed the blow counts for the last two 6‐inch increments. This sum is recorded as the penetration resistance number, or N‐value. If high penetration resistance prevented driving the total length of the sampler, the Shannon & Wilson field representative recorded the partial penetration depth and blow count. The N‐values provide a means for evaluating the relative density or compactness of cohesionless (granular) soils and consistency or stiffness of cohesive (fine‐grained) soils (see Figure A‐1). The raw N‐values are shown on the individual boring logs. Representative portions of the split‐spoon sample obtained in conjunction with the SPT were placed in a screw‐top plastic jar and transported to our laboratory.

A.2.3 Shelby Tube Sampling

Relatively undisturbed soil/rock samples were obtained using Shelby tube samplers in general accordance with ASTM D1587, Standard Practice for Thin‐Walled Tube

Geotechnical Sampling of Soils. The locations of these samples are shown on the individual boring logs. These samples were collected by using the hydraulic ram of the drill rig to push the thin‐walled tube sample into the soil/rock at the bottom of the borehole at the desired depth. The thin‐walled tube was connected to the drill rods via a rigid sampling head. After pushing, the drill rods were retracted and the tube was detached from the sampling head. The Shelby tubes were then capped and transported for laboratory testing.

A.2.4 Pocket Penetrometer

Select cohesive soil samples were tested in the field using a pocket penetrometer. The penetrometer estimates the unconfined compressive strength of a clay soil by shearing the clay with a one‐quarter‐inch‐diameter penetrometer and measuring the resistance (in units of tons per square foot) with a calibrated spring. Where taken, the field measurements from the pocket penetrometer are shown on the individual boring logs.

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A.2.5 Bulk Sampling

A bulk soil sample was obtained by collecting the drill cuttings from the upper 5 feet of

Boring SW‐04. Approximately 20 to 30 pounds of cuttings were placed in a 5‐gallon bucket, sealed with a lid, and transported to our laboratory for further analysis and testing.

November 2019 102477-001

Stubblefield Lake Road Walker County, Texas

1Gravel, sand, and fines estimated by mass. Other constituents, such as organics, cobbles, and boulders, estimated by volume.

2Reprinted, with permission, from ASTM D2488 - 09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure), copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.

A copy of the complete standard may be obtained from ASTM International, www.astm.org.

140 pounds with a 30-inch free fall.

Rope on 6- to 10-inch-diam. cathead 2-1/4 rope turns, > 100 rpm

NOTE: If automatic hammers are used, blow counts shown on boring logs should be adjusted to account for efficiency of hammer.

10 to 30 inches long Shoe I.D. = 1.375 inches Barrel I.D. = 1.5 inches Barrel O.D. = 2 inches

Sum blow counts for second and third 6-inch increments.

Refusal: 50 blows for 6 inches or less; 10 blows for 0 inches.

RELATIVE

CONSISTENCY

N, SPT,

BLOWS/FT.

5% to 12% fine-grained:

with Silt or with Clay 3

15% or more of a second coarse-grained constituent:

with Sand or with Gravel 5

< 5%

5 to 10%

15 to 25%

30 to 45%

50 to 100%

Surface Cement Seal

Asphalt or Cap

Slough

Inclinometer or Non-perforated Casing

Vibrating Wire Piezometer

N, SPT,

BLOWS/FT.

< 4 4 - 10

10 - 30 30 - 50

> 50

DESCRIPTION

< #200 (0.075 mm = 0.003 in.)

#200 to #40 (0.075 to 0.4 mm; 0.003 to 0.02 in.)

#40 to #10 (0.4 to 2 mm; 0.02 to 0.08 in.)

#10 to #4 (2 to 4.75 mm; 0.08 to 0.187 in.)

SIEVE NUMBER AND/OR APPROXIMATE SIZE

#4 to 3/4 in. (4.75 to 19 mm; 0.187 to 0.75 in.)

3/4 to 3 in. (19 to 76 mm)

3 to 12 in. (76 to 305 mm)

> 12 in. (305 mm)

Fine Coarse

Fine Medium Coarse

BOULDERS

COBBLES

GRAVEL

FINES

SAND

Sheet 1 of 3

CONSTITUENT2

SOIL DESCRIPTION

AND LOG KEY

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Absence of moisture, dusty, dry to the touch

Damp but no visible water

Visible free water, from below water table

FIG. A-1

Shannon & Wilson, Inc. (S&W), uses a soil identification system modified from the Unified Soil Classification System (USCS). Elements of the USCS and other definitions are provided on this and the following pages. Soil descriptions are based on visual-manual procedures (ASTM D2488) and laboratory testing procedures (ASTM D2487), if performed.

STANDARD PENETRATION TEST (SPT)

SPECIFICATIONS

Hammer:

Sampler:

N-Value:

Dry

Moist

Wet

MOISTURE CONTENT TERMS

Modifying (Secondary)

Precedes major constituent

Major

Minor Follows major constituent

1All percentages are by weight of total specimen passing a 3-inch sieve.

2The order of terms is: Modifying Major with Minor.

3Determined based on behavior.

4Determined based on which constituent comprises a larger percentage.

5Whichever is the lesser constituent.

COARSE-GRAINED

SOILS

(less than 50% fines)1

NOTE: Penetration resistances (N-values) shown on boring logs are as recorded in the field and have not been corrected for hammer efficiency, overburden, or other factors.

PARTICLE SIZE DEFINITIONS

RELATIVE DENSITY / CONSISTENCY

Sand or Gravel 4

30% or more coarse-grained:

Sandy or Gravelly 4

More than 12% fine-grained:

Silty or Clayey 3

15% to 30% coarse-grained:

with Sand or with Gravel 4

30% or more total coarse-grained and lesser coarse-grained constituent is 15% or more:

with Sand or with Gravel 5

Very soft Soft Medium stiff Stiff Very stiff Hard

Very loose Loose…