Appendix_C_-_Geotech_Report.pdf

USMA NEW CADET BARRACKS

United States Military Academy, West Point, NY

Contract No. W912DS-12-C-0018

FINAL DESIGN REPORT

RFP APPENDIX VOLUME 5 of 6

GEOTECHNICAL ENGINEERING ANALYSIS REPORT

STV/URS JOINT VENTURE

225 Park Avenue South

New York, NY 10003

September 10, 2012

TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS

i

SECTION 1. EXECUTIVE SUMMARY

SECTION 2. INTRODUCTION

2.1 GENERAL

2.2 PROJECT LOCATION AND DESCRIPTION

2.3 SCOPE OF WORK TASKS

2.4 REPORT ORGANIZATION

SECTION 3. SUBSURFACE CONDITIONS

3.1 GENERAL

3.2 SUBSURFACE INVESTIGATIONS

3.2.1 2006 Investigation

3.2.2 2012 Investigation

3.2.2.1 Rock Outcrop Survey

3.2.2.2 Test Borings ………………………...……………………………...……… 10

3.2.2.3 Detailed Logging of Rock Core ………………………...……….… 10

3.2.2.4 Laboratory Testing ……………...…………………………...……….10

3.2.3 Borehole Geophysical Surveys

3.3 GENERALIZED SUBSURFACE CONDITIONS

3.4 GROUNDWATER CONDITIONS……..…...………………………………………………….12

SECTION 4. EVALUATIONS AND RECOMMENDATIONS FOR FOUNDATION DESIGN

4.1 GENERAL

4.2 FOUNDATION DESIGN

4.2.1 Foundation Type and Subgrade Conditions

4.2.2 Allowable Bearing Pressures and Footing Design

4.3 SEISMIC CONSIDERATIONS

4.3.1 Seismic Site Classification

4.3.2 Soil Liquefaction Potential

4.4 LATERAL PRESSURE ON BELOW-GRADE WALLS

4.5 PERMANENT GROUNDWATER CONTROL

SECTION 5. EXCAVATION FOR BUILDING AND STABILITY OF HILLSIDE SLOPES

5.1 GENERAL

5.2 ANALYSIS APPROACH

5.3 INPUT PARAMETERS FOR ANALYSIS AND DESIGN

5.3.1 DIPS Analysis

5.3.2 ROCPLANE Analysis

5.3.3 SWEDGE Analysis

5.3.4 Rock Bolt Design

5.4 ANALYSIS RESULTS

5.4.1 DIPS Analysis

5.4.2 Eastern Facing Rock Slopes

TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS (Cont.)

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5.4.3 Northern Facing Rock Slopes

5.4.4 Rock Bolt Structural Design

SECTION 6. PROTECTION AGAINST LONG-TERM ROCK FALLS

6.1 GENERAL

6.2 ANALYSIS APPROACH

6.3 INPUT PARAMETERS FOR ANALYSIS AND DESIGN

6.3.1 CRSP Analysis

6.3.2 Rock Fence Design

6.4 ANALYSIS RESULTS

6.4.1 CRSP Analysis

6.4.2 Rock Fence Design

SECTION 7. GEOTECHNICAL CONSIDERATIONS FOR OTHER CONSTRUCTION

7.1 GENERAL

7.2 PROPOSED BUILDING EAST WALL EXCAVATION

7.3 WIDENING OF DE RUSSY ROAD

7.4 STORM WATER DETENTION TANK EXCAVATION

7.5 FUTURE ANALYSES FOR 100% SUBMISSION

7.5.1 Cooling Tower

7.5.2 Landscaped Area West of the Formation Area

SECTION 8. LIMITATIONS

LIST OF TABLES

Table No. 1 Summary of Borings Performed in 2012

Tables Nos. 2 to 9 Summary of Results CRSP Analyses

LIST OF FIGURES

Figure No. 1 Test Boring Location Plan

Figure Nos. 2 to 9 Subsurface Profiles A-A’ through H-H’

Figure No. 10 Example Rock Slope Configuration with Benches and Rock Fences

Figure No. 11 Rock Bolt Configuration North and East Facing Slopes

Figures Nos. 12 to 19 Rock Slope Geometries Analyzed with CRSP

Figure No. 20 Rock Bolt Configuration East Building Wall

Figure No. 21 De Russy Road Rock Excavation Plan

LIST OF APPENICES

TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS (Cont.)

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Appendix A Analysis of East Facing Rock Slopes

Appendix B Analysis of North Facing Rock Slopes

Appendix C CRSP Analysis Results

Appendix D Rock Fence Design

Appendix E Analysis of Rock Cut at the East Building Wall

Appendix F Analysis of Rock Cut at De Russy Road

SECTIONSECTIONSECTIONSECTIONONE Executive Summary

This report presents the results of geotechnical engineering analyses performed in support of the design of a proposed New Cadet Barracks at The United States Military Academy in West

Point, New York. Specifically, this report provides the basis of design of excavations required for siting of the new building, stabilization of the resultant excavation side slopes, geotechnical recommendations for design of foundations for support of the new building, and geotechnical considerations for other construction.

The following are the key geotechnical findings and recommendations in support of the design of this project:

Generalized Subsurface Conditions

1. Based on the results of 26 test borings, the site generally consists of up to 0 feet to 9 feet of soil overlying bedrock. Generally, the test borings that were completed in the parking lot overlooking Brewerton Road encountered 3 feet to 9 feet of granular fill which typically consisted of brown c-f sand with varying amounts of silt and gravel. The three test borings completed in and near De Russy Road and De Russy Loop encountered between 4 feet and 9 feet of gray medium to fine gravel with some sand with cobbles and boulders. The remaining borings were all completed on the hillside adjoining the two parking lots. Of the thirteen borings performed in this area, eight of them had less than 5 feet of overlying topsoil that generally consisted of brown sand and silt mixtures with varying amounts of gravel. In six of the borings, bedrock was encountered at or within about one foot beneath the surface.

2. Bedrock generally consists of slightly to highly weathered, slightly to closely fractured, gneiss and granite gneiss. The rock core recoveries ranged from 60% to 100%, and the

Rock Quality Designation (RQD) values ranged from 0 to 100%, but were typically between 36% and 78%. The rock is classified as Hard Sound Rock to Soft Rock. The top of rock is estimated to be at depths ranging from approximately 0 to 9 feet below the ground surface, corresponding to approximately El. +280 to +185 feet.

3. From the stereonet analysis of the field rock outcrop mapping, the average strike of rock foliation in outcrop (n=23) is about 015 (N15E) with an average dip of 47 degrees to the east. Minor and outcrop-scale tight to isoclinal folds were noted in areas, which accounts for some of the variability in the strike and dip data set. A well-developed joint set (n=7) has an average strike of 146 (S34E) and an average dip of 80 degrees to the west. A weak to strong lineation (n=4) has an average trend of 030 (N30E) and an average plunge of 13 degrees.

Considerably more detailed data was obtained from the borehole geophysical surveys.

This data was utilized for the evaluation of mass rock stability during and subsequent to excavation for the new building as described in Section 5.

Foundation Recommendations

1. Assuming that the ground floor slab will be established at El. 200 feet, rock excavation will be required over much of the site to establish foundation subgrades for the building.

Therefore, the building column and wall loads can be supported on spread footings bearing on bedrock. However, on the east side of the proposed building, along the northern face, as much as 9 feet of fill soils were encountered in the borings above top of rock. Since these soils are not considered suitable for support of the proposed building, soil excavation will be required to establish suitable subgrades for lowered footings bearing on competent rock. This foundation scheme is recommended as backfilling these areas with structural fill and founding footings higher up on the compacted fill would likely result in unacceptable and damaging differential settlements between those footings bearing on rock and those bearing on the compacted fill soil.

2. The maximum allowable design bearing capacity for footings bearing on bedrock for most of the building site is recommended to be 20 tons per square foot (tsf). However, weaker rock conditions were generally encountered in the borings where fill soils were placed on the east side of the site. Consequently, in this area, the recommended maximum allowable design bearing capacity is reduced 8 tsf. The approximate extents of the areas where 8 tsf and 20 tsf bearing values may be found following excavation are shown in Figure 1 of this report. In any case, a transitional area where it is currently unknown if 8 tsf or 20 tsf rock will be encountered during construction. Consequently, it is recommended that two foundation schedules, one for rock with 8 tsf bearing capacity and one for rock with 20 tsf bearing capacity, be prepared for footings falling within this area. During excavation, the appropriate foundation schedule can then be selected based on the results of the rock subgrade inspection by a qualified geotechnical engineer.

3. The proposed building will be founded on bedrock. Therefore the recommended seismic site classification is Site Class B. Therefore, if the Seismic Use Group is I or II, the Seismic

Design Category is “B”. The appropriate Seismic Use Group should be determined by the

Architect or Structural Engineer.

4. The United Facilities Criteria (UFC) 3-310-04 Section 3-20.3 “Soils and Foundations”

States that the International Building Code (IBC) Chapter 18 shall apply. The New York

State IBC Section 1804.2d allows a 1/3 increase in allowable foundation pressure when using the alternate load combinations in Section 1605.3.2 that include wind or seismic loads. Therefore, when using the applicable load combinations, a 1/3 increase in the allowable foundation pressure present is permitted for seismic load cases.

5. Seismic induced soil liquefaction is not a concern for the project because the proposed building will be founded on bedrock.

6. It is recommended that below grade walls retaining soils be designed using the following unit weight and earth pressure coefficients:

Soil Unit Weight 120 pounds per cubic foot (pcf)

Coefficient of Active Earth Pressure, Ka 0.3

Coefficient of Passive Earth Pressure, Kp 3.2

Coefficient of At Rest Earth Pressure, K0 0.5

In addition, a seismic lateral soil force of 6H

(lb/ft of wall), where H is the total vertical height of the wall, in feet, should be included. This force should be applied at a distance of H/3 from the top of the wall (i.e., wall pressure is an inverted triangle).

7. Where walls are cast directly against a rock face, rock pressures against the wall may develop depending on the condition and dip of the rock. If the rock dips into the excavation this could result in relatively large pressures. Since this is generally the case at the retaining wall to be located at the east wall of the proposed building, it is recommended that permanent rock anchors be installed to retain the rock mass and therefore eliminate rock pressures acting on the wall. The design of the rock anchors should take into consideration any external loads acting on the rock mass which may be from the transfer of building loads at foundation level.

8. The recommended lateral pressures do not include any surcharge loads adjacent to the walls or at the ground surface. It is recommended that a uniform (i.e., rectangular) lateral pressure distribution of 0.40 times the surcharge be added to the lateral soil and rock pressure distribution. The structural engineer should determine the magnitude of the surcharge loads (i.e., live loads).

9. Groundwater was sporadically encountered within the boreholes; however, this information is not considered reliable due to the complex nature of water flowing through the rock mass. In addition, groundwater was observed flowing down the existing hill in the vicinity of the proposed building. Since it is difficult to estimate the path groundwater within the rock mass will follow subsequent to rock excavation, and the fact that the excavation work may create new fractures or open up existing ones, it is recommended that the building design include provisions for an under slab drainage system. Recommendations for such a system are provided in this report

Building Excavation and Excavation Stability

1. Evaluation of rock slope stability in terms of prevention of overall rock mass failure was performed for the proposed rock slope in both the northern and eastern facing directions. Analyses were performed considering the stability of rock wedges that could be created as a consequence of the excavation with respect to joint orientations within the rock mass. Strike and dip data recorded during the subsurface investigation program from geophysical testing were entered into the Dips computer program, version 5.1 developed by RocScience. Analyses were performed to determine the most probable failure mode of the rock mass (i.e. planar sliding, wedge sliding, or toppling). Depending on the results of this analysis, the strike and dip data was then input into either the

RocPlane computer program (for two-dimensional planar failure modes) or the Swedge computer program (for three-dimensional wedge failure modes) both developed by

RocScience.

2. Examining geophysical data and failure envelopes in the Dips computer program, it was identified that the most likely rock mass failure mode for eastern facing slopes is planar sliding. The most likely failure mode for the northern facing slopes is wedge sliding.

However, based on the number of fractures falling within the wedge sliding failure envelope, this failure mode is less likely to occur.

3. The results of the RocPlane analysis of the eastern facing rock slopes indicate that 15 to

18 tons of rock bolt force per linear foot of rock slope per bench is required to stabilize the rock mass with a factor of safety of 2. Base on this, it is recommended that a rock bolt spacing of approximately 6 ft horizontally and vertically be used with rock bolts varying in length from 15 ft to 30 ft.

4. Considering the number of unstable wedges likely to be encountered on the northern facing slopes as determined using the Swedge computer program and the percentage of joints falling within the failure envelope as determined using Dips, it is recommended that a rock bolt spacing of approximately 10 ft horizontal and vertically be used with rock bolt lengths varying from 20 ft to 30 ft.

5. Based on the maximum required rock bolt capacity and cost per rock bolt, it is recommended that the rock bolts consist of 1 inch nominal diameter, Grade 150, galvanized, all-thread bar. The size of the bolt bearing plate should be a minimum of 6 inch by 6 inch by 1 ¼ inch thick.

Long Term Rock Slope Stability

1. Analyses were performed to evaluate the preferred slope geometry in the case of relatively small rock blocks falling subsequent to the final construction. For this purpose, various slope configurations were modeled using the Colorado Rockfall Simulation

Program, version 4.0 (CRSP). This computer program can be used for locating and designing rockfall mitigation. It simulates rocks tumbling down a slope, and predicts the statistical distribution of speed and bounce height of these blocks. Numerous geometries were evaluated varying the slope angle, bench width, number of benches, height of rockfall fencing, and distance of the rockfall capture fencing from the toe of the slope. This process was carried out until a rock slope configuration meeting the constraints posed by the site and the preferred geometry was determined.

2. Based on the results of the CRSP analysis, the recommended slope geometry includes three 5 ft wide benches along the height of the slope with a 4 ft wide catchment along the toe of the slope. The maximum height between benches is limited to 22 ft, and the minimum height of rock fences on each bench and at the toe of the slope is 10 ft.

3. It is recommended that a rock fence with an ultimate capacity, in terms of kinetic energy dissipation, of 370 kip-feet (500 KJ) is installed on each bench and at the toe of the slope. The rock fence design was based on the kinetic energy produced by the design rock block falling from the top of the slope as calculated using CRSP. A safety factor of 2 was used for the design energy.

4. Based on the anchor loads for the Geobrugg, GBE 500A rock fence with a 20 ft post spacing, the following anchor lengths are required:

Anchor Type Number of Anchors

Required

Anchor Hole

Diameter (inch)

Anchor Length

(feet)

Foundation anchor

1 inch 75 ksi bar

2 per post 3 3

Tie back anchor

5/8 inch wire rope

2 per post 4 3

Lateral Anchors

3/4 inch wire rope

2 per 300 ft of fence length

4 15

Foundation and wire rope anchor design assumes an ultimate grout/rock bond stress of

100 psi. A safety factor of 2 is used for anchor design.

Geotechnical Considerations for Other Construction

1. The rock excavation along the Brewerton Road Extension adjacent to Grant Hall will require extensive rock support due to the loads of the proposed building acting on the rock mass. Based on the results of a planar sliding analysis using RocPlane, which included the building loads provided, it is recommended that 1-3/8 inch diameter, 150 ksi rock bolts be installed with an approximately 4 ft spacing. The required length of the rock bolts is approximately 40 ft.

2. Rock excavation for the widening of De Russy Road will require rock bolting for overall slope stability and installation of a rock fence for long term stability. Requirements for bolting and rock fence are the same as the excavation for the building. It is recommended that rock fence be installed for stations greater than 2+50, and that rock bolts be installed for stations greater than 3+50.

3. Excavation of rock for the storm water detention tank on the south side of the new building will not require additional rock support. If unstable rock wedges are encountered during construction, it is recommended that they be removed to eliminate potential hazards during construction, and replaced with compacted structural fill or lean concrete.

4. A cooling tower is to be sited at the top of the excavation near the existing water tank.

An analysis of potential loading on the excavation slope from the cooling tower, and rock excavation for the landscaped area west of the Formation Area have not yet been performed as the loading and final configuration of these areas has not yet been determined. Geotechnical recommendations, if required, will be provided in the 100% submission.

SECTIONSECTIONSECTIONSECTIONTWO Introduction

2.1 GENERAL

This report presents the results of geotechnical engineering analyses performed in support of the design of a proposed New Cadet Barracks at The United States Military Academy in West

Point, New York. Specifically, this report provides the basis of design of excavations required for siting of the new building, stabilization of the resultant excavation side slopes, geotechnical recommendations for design of foundations for support of the new building, and geotechnical considerations for other construction.

Our understanding of the requirements of the project is primarily based on the scope of work approved by the U.S. Army Corps of Engineers (New York District). At the time of preparation of this report, the design was completed to a 90% level.

2.2 PROJECT LOCATION AND DESCRIPTION

The project site is located at the USMA, West Point, in New York. The site currently consists of some parking areas and the adjoining hillside, overlooking the parking areas. The north side of the site is largely occupied by an existing parking lot at about El. 197 that is accessible from De

Russy Road, and a steep rock slope below the lot down to Brewerton Road at about El. 160.

The hillside above the parking lot and De Russy Road is steep and generally wooded. It has a shallow soil cover with rock outcrops observed in a number of locations. The top of the hillside within the project area varies from about El. 270 to 287. The Cadet Chapel (Building 722 and

60) is situated at the top of the hillside near the western end of the project site, while a large water tank is situated about 400 feet further to the east. Sherman Barracks (Building 756A) is located to the north, while Grant Barracks (Building 602) and Sherman Barracks (Building 738) are located along the east side of the site.

The proposed new barracks will include five floors of cadet rooms for a total of 650 beds and one floor of support/mechanical spaces. The first floor will be at about El. 200. It is currently estimated that over 120,000 cubic yards of rock will need to be excavated and removed from the site to provide room for the new building. The excavation will create an exposed rock face behind the building which will require stabilization to ensure rock slope integrity and to minimize the risk of rock falls down the slope.

In order to provide access to the site during construction De Russy Road will be widened towards the hillside thus requiring additional rock excavation and stabilization. Since the road will be subject to heavy truck traffic during construction, stabilization of the steep rock slope below De Russy Road will also be required to ensure the safety of pedestrians and traffic from potential rock falls during the construction period.

All elevations referred to in this report are in feet and are referenced to the NAVD 88 Vertical Datum.

SECTIONSECTIONSECTIONSECTIONTWO Introduction

2.3 SCOPE OF WORK TASKS

The scope of tasks associated with this engineering design report included the following major work items:

1. Review of the results of the site-specific subsurface investigation carried out by the

STV/URS Joint Venture between April and June of 2012.

2. Evaluation of rock discontinuity strike and dip data obtained from the geophysical bore hole surveys to determine statistically relevant orientations of potential planes of weakness in the rock slopes.

3. Evaluation of factors of safety against instability of rock masses for various excavation cut geometries.

4. Determination of the requirements for stabilization of cut slopes by rock bolting to ensure adequate protection against rock mass instability.

5. Evaluation of the needs for protection against rock falls following excavation and rock bolting of cut slopes.

6. Determination of suitable foundation schemes for support of the new building and associated structures, including recommendations for allowable bearing capacity, seismic site classification, design lateral earth/rock pressures for retaining walls, and other geotechnical design parameters.

2.4 REPORT ORGANIZATION

Following this introductory section, SECTION THREE provides a summary of the results of the site-specific subsurface investigation performed for this project. Recommendations for design of structure foundations and retaining walls are provided in SECTION FOUR. SECTION FIVE includes a description of the engineering analyses performed to evaluate the rock mass stability of cut slopes, along with the requirements for installation of rock bolts to provide safety against rock mass failures. Following this section, SECTION SIX provides a description of the analyses performed and results therefrom to determine the requirements for long-term protection against rock falls from the surface of the cut slopes. SECTION SEVEN includes discussion of additional geotechnical considerations for other portions of the project, including the widening of De Russy Road, the rock slopes along the eastern side of the site, excavation for a storm water retention tank behind the new building. Finally, SECTION EIGHT describes the limitations of the study described in this report.

Tables, Figures and Appendices are provided following the text portion of this report.

SECTIONSECTIONSECTIONSECTIONTHREE Subsurface Conditions

3.1. GENERAL

This section of the report provides a brief description of the subsurface investigation performed for this project, along with a generalized description of the subsurface conditions.

3.2. SUBSURFACE INVESTIGATIONS

A brief description of subsurface investigations performed to-date at or in near proximity of the site are presented below. More detailed information is provided in a separate subsurface investigation report prepared by STV/URS dated August 2012

3.2.1. 2006 Investigation

In 2006, a subsurface investigation program was conducted by Parrett Wolff Inc. of Syracuse

New York. The investigation consisted of three test borings denoted B-1 through B-3 along a portion of the north side of the Student Chapel (see Figure 1 for the approximate locations of these borings). Following completion of these borings, geophysical logging was performed in the open boreholes by Hager-Richter Geoscience Inc., of Fords, New Jersey to determine the depth and orientations of fractures intersected by the boreholes. Specifically, the geophysical investigation consisted of acoustic televiewer (ATV) logging and optical televiewer (OTV) logging in two of the boreholes denoted B-1 and B-3.

3.2.2. 2012 Investigation

The 2012 URS\STV field investigation program consisting of the performance of a total of 26 test borings (denoted as B-1 through B-26 in Figure 1) including detailed rock core logging, borehole geophysical surveys (see Section 3.2.3 for details), rock outcrop surveys and performance of laboratory tests on recovered samples of fill soils and rock core.

3.2.2.1. Rock Outcrop Survey

Mapping of rock outcrops in the project area was performed in early April 2012. The mapping was conducted using surveyed base maps and aerial photographs for location, and a Brunton compass to measure rock features. Digital photographs of rock exposures were taken during site visits and catalogued for the mapping locations. A site bedrock structure map was created based on the results of the field investigation.

From the stereonet analysis of the field rock outcrop mapping, the average strike of rock foliation in outcrop (n=23) is about 015 (N15E) with an average dip of 47 degrees to the east.

Minor and outcrop-scale tight to isoclinal folds were noted in areas, which accounts for some of the variability in the strike and dip data set. A well-developed joint set (n=7) has an average strike of 146 (S34E) and an average dip of 80 degrees to the west. A weak to strong lineation

(n=4) has an average trend of 030 (N30E) and an average plunge of 13 degrees.

Considerably more detailed data was obtained from the borehole geophysical surveys (see

Section 3.2.3). This data was utilized for the evaluation of mass rock stability during and subsequent to excavation for the new building as described in Section 5.

3.2.2.2. Test Borings

The test borings were subsequently performed between April 10 and June 7, 2012 by Jersey

Boring and Drilling, Inc. of Newark, New Jersey. Inspection of the test borings was performed on a continuous basis by URS geotechnical engineers. Standard split spoon samples of the overburden soils were obtained at maximum intervals of five feet. Upon encountering bedrock, rock coring was performed using a NX-size (2-1/8 in. O.D.) core barrel. Coring was performed in order to verify the presence of bedrock (instead of intercepting a boulder), and to assess relative quality of the bedrock as indicated by the Rock Core Recovery (REC) and the Rock

Quality Designation (RQD) . The amount of rock cored in each boring varied from 10 feet to as much as 85 feet.

The rock core brought to the surface was classified visually by the field geotechnical engineer and measurements of the lengths of core pieces were made to estimate rock quality and competency through calculation of the Rock Core Recovery and Rock Quality Designation

(RQDs). This information was recorded on field logs to provide a preliminary estimate of rock characteristics. A summary of the borings indicting depth to top of rock and genera nature of the overburden materials is provided in Table 1.

3.2.2.3. Detailed Logging of Rock Core

The recovered rock core was subsequently transported to the West Point Department of Public

Works Building and stored in a controlled and secured location. A URS geologist then performed detailed examinations of the rock core to expand the rock descriptions noted on the field logs.

3.2.2.4. Laboratory Testing

Representative soil samples and sections of rock core were selected for laboratory testing. The laboratory testing program performed on selected rock core samples included twelve (12) rebound hardness (Schmidt hammer) tests and five (5) unconfined compression strength tests.

Grain size distribution (sieve) tests were performed on a total of four samples of soil fill material encountered above bedrock.

The Core Recovery is defined as the ratio (expressed as a percent) of the total length of recovered core to the length cored.

The Rock Quality Designation (RQD) is defined as the ratio (expressed as a percentage) of the total length of recovered core samples having a length of at least twice the core diameter (e.g., about 4 in for NX2core) to the total length of core.

3.2.3. Borehole Geophysical Surveys

Borehole geophysical logging was conducted in eight (8) of the test borings by Hager-Richter

Geoscience, Inc. (Hager-Richter) of Fords, New Jersey. Specifically, both an optical televiewer

(OTV) and an acoustic televiewer (ATV) was used to determine the depth and orientation of bedrock structures such as fractures, foliation and veins intersected by the borehole. The ATV tool was utilized in the borehole above a stable water level (bore holes were filled with water prior to the logging) to acquire a 360 degree image of the borehole wall using reflections of sound waves in the ultrasonic frequency range. Wherever the water level in the bore hole could not be maintained, the OTV tool was used to obtain a high resolution oriented image of the borehole wall.

The geophysical logging data was then processed and the orientation of bedrock structures

(I.e., dip direction and dip angle) were determined with depth. Based on the interpretation of the OTV image, the ATV amplitude image, and the ATV travel time image, bedrock structures were categorized. The bedrock structures detected were grouped into five categories: foliation or vein, and four fracture classes (Fracture Rank 1 through Fracture Rank 4) dependent on the continuity and aperture of the fracture. As discussed in Section 5 of this report, this data was used for analyses of the stability of the rock mass in relation to the excavation for the new building.

3.3. GENERALIZED SUBSURFACE CONDITIONS

Based on the results of the test borings, and as summarized in Table 1, the site generally consists of up to 0 feet to 9 feet of soil overlying bedrock. Specifically, the test borings that were completed in the parking lot encountered 3 feet to 9 feet of granular fill which typically consisted of brown c-f sand with varying amounts of silt and gravel. The three test borings completed in and near De Russy Road and De Russy Loop encountered between 4 feet and 9 feet of gray medium to fine gravel with some sand with cobbles and boulders. The remaining borings were all completed on the hillside adjoining the two parking lots. Of the thirteen borings performed in this area, eight of them had less than 5 feet of overlying topsoil that generally consisted of brown sand and silt mixtures with varying amounts of gravel. In six of the borings, bedrock was encountered at or within about one foot beneath the surface.

At the project site, the bedrock generally consists of slightly to highly weathered, slightly to closely fractured, gneiss and granite gneiss bedrock. The rock core recoveries range from 60 to

100% and the RQD values range from 0 to 100%, but were typically between 36 and 78%. The rock is classified as Hard Sound Rock to Soft Rock. The top of rock is estimated to be at depths ranging from approximately 0 to 9 feet below the ground surface, corresponding to approximately El. +280 to +185 feet.

3.4. GROUNDWATER CONDITIONS

Although no groundwater observation wells were installed in any of the completed test borings, information was collected about the groundwater level in the boreholes based on observations made during the geophysical logging.

SECTIONSECTIONSECTIONSECTIONFOUR Evaluations and Recommendations for Foundation Design

4.1. GENERAL

This section of the report presents results of geotechnical evaluations and provides recommendations for the design of foundations for the proposed new barracks building and associated facilities. The evaluations and recommendations are based on the results of the field investigation performed for this project and current understanding of the proposed project requirements.

4.2. FOUNDATION DESIGN

4.2.1. Foundation Type and Subgrade Conditions

Nine subsurface profiles (denoted as A-A’ through H-H’ on Figure 1) were prepared to provide an understanding of the likely foundation subgrade conditions to be revealed following excavation work for the new barracks building. These profiles are shown in Figures 2 through 9.

Shown on each profile are the present elevations of 200 feet and 195 feet corresponding to the building first floor top of slab and top of formation area, respectively.

An examination of these profiles indicates that rock excavation will be required over much of the site to establish foundation subgrades for the building. Therefore, the building column and wall loads can be supported on spread footings bearing on bedrock. However, on the east side of the proposed building, along the northern face, as much as 9 feet of fill soils were encountered in the borings above top of rock. Since these soils are not considered suitable for support of the proposed building, soil excavation will be required to establish suitable subgrades for lowered footings bearing on competent rock. This foundation scheme is recommended as backfilling these areas with structural fill and founding footings higher up on the compacted fill would likely result in unacceptable and damaging differential settlements between those footings bearing on rock and those bearing on the compacted fill soil.

4.2.2. Allowable Bearing Pressures for Footing Design

The maximum allowable design bearing capacity for most of the building site is recommended to be 20 tons per square foot (tsf). As a rough guide, such a capacity would be assumed for rock subgrades where the Rock Quality Designation (RQD) determined for rock cores obtained below the design subgrade level is in the range of about 35% to 50%. However, weaker rock conditions where RQD values were less that 35% were generally encountered in the borings where fill soils were placed on the east side of the site. Consequently, in this area, the recommended maximum allowable design bearing capacity is reduced 8 tsf. The approximate extents of the areas where 8 tsf and 20 tsf bearing values may be found following excavation are shown in Figure 1.

As shown in Figure 1, there is be a transitional area where it is currently unknown if 8 tsf or 20 tsf rock will be encountered during construction. Consequently, it is recommended that two foundation schedules, one for rock with 8 tsf bearing capacity and one for rock with 20 tsf bearing capacity, be prepared for footings falling within this area. During excavation, the appropriate foundation schedule can then be selected based on the results of the rock subgrade inspection by a qualified geotechnical engineer.

4.3. SEISMIC CONSIDERATIONS

4.3.1. Seismic Site Classification

As indicated in the previous section, the building will be supported on rock. Considering this and the provisions in the Code, the recommended seismic site classification is Site Class B.

Therefore, if the Seismic Use Group is I or II, the Seismic Design Category is “B”. The appropriate Seismic Use Group should be determined by the Architect or Structural Engineer.

The United Facilities Criteria (UFC) 3-310-04 Section 3-20.3 “Soils and Foundations” States that the International Building Code (IBC) Chapter 18 shall apply. The New York State IBC Section

1804.2d allows a 1/3 increase in allowable foundation pressure when using the alternate load combinations in Section 1605.3.2 that include wind or seismic loads. Therefore, when using the applicable load combinations, a 1/3 increase in the allowable foundation pressure present is Section 4.2.2 is permitted for seismic load cases.

4.3.2. Soil Liquefaction Potential

Seismic induced soil liquefaction is not a concern for the project because the proposed building will be founded on bedrock.

4.4. LATERAL PRESSURES ON BELOW GRADE WALLS

The design lateral pressures for permanent below grade walls consist of static and seismic pressures that are influenced by the thickness and type of the overburden material. It is recommended that below grade walls retaining soils be designed using the following unit weight and earth pressure coefficients:

Soil Unit Weight 120 pounds per cubic foot (pcf)

Coefficient of Active Earth Pressure, Ka 0.3

Coefficient of Passive Earth Pressure, Kp 3.2

Coefficient of At Rest Earth Pressure, K0 0.5

In addition, a seismic lateral soil force of 6H

(lb/ft of wall), where H is the total vertical height of the wall, in feet, should be included. This force should be applied at a distance of H/3 from the top of the wall (i.e., wall pressure is an inverted triangle).

The rock pressures on below grade walls will ultimately be dependent on the condition and dip of the rock. If the rock dips into the excavation this could result in relatively large pressures.

Since this is generally the case at the retaining wall to be located at the east wall of the proposed building, it is recommended that permanent rock anchors be installed to retain the rock mass and therefore eliminate rock pressures acting on the wall. The design of the rock anchors should take into consideration any external loads acting on the rock mass which may be from the transfer of building loads at foundation level.

The recommended lateral pressures do not include any surcharge loads adjacent to the walls or at the ground surface. It is recommended that a uniform (i.e., rectangular) lateral pressure distribution of 0.40 times the surcharge be added to the lateral soil and rock pressure distribution. The structural engineer should determine the magnitude of the surcharge loads

(i.e., live loads).

4.5. PERMANENT GROUNDWATER CONTROL

Groundwater was sporadically encountered within the boreholes; however, this information is not considered reliable due to the complex nature of water flowing through the rock mass. In addition, groundwater was observed flowing down the existing hill in the vicinity of the proposed building. Since it is difficult to estimate the path groundwater within the rock mass will follow subsequent to rock excavation, and the fact that the excavation work may create new fractures or open up existing ones, it is recommended that the building design include an under slab drainage system (i.e., underdrain).

The underdrain system should include crushed stone (minimum 12 inch thick) and a network of drainage pipes. The crushed stone should conform to the gradation requirements of commercially known ¾ inch crushed stone and should be placed over the entire first floor area.

A 6-in. diameter corrugated perforated plastic pipe (Advanced Drainage System N-12, or approved equal) is recommended under the slab on 30 ft maximum centers and along the base of the exterior walls. The pipes should be encased with a minimum 6-in. thick envelope of ¾ in.

crushed stone. The pipes should be placed with a positive slope of about 1/32 in. to 1/16 in.

per foot of pipe and connected to the sump pits. In order to separate the crushed stone from the subgrade soil, to prevent possible clogging of the perforated pipes, the subgrade should be covered with a non-woven filter fabric (Mirafi 140N, or approved equal).

SECTIONSECTIONSECTIONSECTIONFIVE Excavation for Building and Stability of Hillside Slopes

5.1. GENERAL

Based on the site survey and the floor elevation (El. 200 ft +/-) of the proposed building, the maximum height of the rock slope created by the necessary excavation will be approximately

90 ft. The maximum slope height occurs where the slope is located closest to the Cadet

Chapel. Considering the location of the proposed building in plan, the required width of the service road running between the building and the rock slope (approximately 35 ft including the sidewalk), and the close proximity of the Cadet Chapel, only approximately 30 ft of horizontal distance is available for the rock slope and required safety measures to occupy.

Based on discussions between STV/URS, the USACE, and West Point, the preferred rock slope geometry is to include a series of benches cut into the rock slope, with rock fall retention fences installed along each bench and along the toe of slope. An example of this type of configuration is shown in Figure 10. The purpose of the analysis described in this section of the report is to evaluate the global stability of the rock slope (i.e. large rock mass failure) created by the excavation for the building. The analyses to determine the requirements for long-term protection against rock falls, and associated design recommendations are described in Section

6.

5.2. ANALYSIS APPROACH

Evaluation of rock slope stability in terms of prevention of overall rock mass failure was performed for the proposed rock slope in both the northern and eastern facing directions.

Analyses were performed considering the stability of rock wedges that could be created as a consequence of the excavation with respect to joint orientations within the rock mass. Strike and dip data recorded during the subsurface investigation program from geophysical testing were entered into the Dips computer program, version 5.1 developed by RocScience. This program statistically analyzes the strike and dip data to provide the user with most probable joint orientations within the rock mass. Another analysis was then performed with Dips to compare the angle of the proposed rock cut to the strike and dip data. This analysis was performed to determine the most probable failure mode of the rock mass (i.e. planar sliding, wedge sliding, or toppling). Depending on the results of this analysis, the strike and dip data was then input into either the RocPlane computer program or the Swedge computer program both developed by RocScience.

RocPlane was used to perform 2-dimensional analyses for assessing the stability of rock slopes where it was determined that the predominant failure mode is planar sliding. The program is used to evaluate the possibility of planar sliding that can occur when the predominant dip angle and the angle of the rock face are orientated in the same direction. Driving forces (forces promoting rock failure such as rock mass and water pressure) are compared to the resisting forces (forces preventing movement of the rock mass such as friction). Based on results of this comparison, the required stabilizing force (i.e., rock bolt force) can be calculated, and the approximate spacing of rock bolts required to provide the desired factor of safety against planar sliding can be estimated.

Swedge was used to perform 3-dimensial analyses for rock slopes were it was determined that the predominant failure mode is wedge sliding. This program statistically analyzes the joint set data imported from Dips and determines the probable number of unstable wedges which may be created by these joint sets. Based on this, the approximate spacing of rock bolts required to support the unstable wedges and provide the desired factor of safety against wedge sliding failure can be estimated.

5.3. INPUT PARAMETERS FOR ANALYSIS AND DESIGN

5.3.1 Dips Analysis

The Dips analysis used the strike and dip data recorded in the boreholes during the geophysical testing. This information is provided in a separate subsurface investigation report prepared by

STV/URS dated August 2012. Only fractures of Rank 3 and 4 were included in the analysis.

These represent the most critical discontinuities whereby the fractures are distinct and have some to continuous aperture. Additional input parameter values included the following:

• Joint Friction Angle: 35 degrees

• Slope Dip Angle: 85 degrees

• Eastern and Northern Facing Slopes

5.3.2 RocPlane Analysis

The RocPlane analysis used the Dips output as well as the following parameter values:

• Rock Density: 165 pcf

• Joint Friction Angle: 35 degrees.

• Full hydrostatic pressure in the joints.

• Slope Dip Angle: 85 degrees

• Eastern Facing Slopes

• Slope Height: 90 ft

• Slope Length: 100 ft

5.3.3 Swedge Analysis

The Swedge analysis used the Dips output as well as the following parameter values:

• Rock Density: 165 pcf

• Joint Friction Angle: 35 degrees.

• Full hydrostatic pressure in the joints.

• Slope Dip Angle: 85 degrees

• Northern Facing Slopes

• Slope Height: 90 ft

• Slope Length: 100 ft

• Joint Persistence: 20 to 25 ft

• Min. Wedge Wt.: 2 tons

5.3.4 Rock Bolt Design

The lengths of rock bolts and the required rock bolt spacing for active slope reinforcement was estimated based on the results of the RocPlane analysis for eastern facing slopes, and on the results of the Swedge analysis for the northern facing slopes. Rock bolts were designed assuming an ultimate grout/rock bond stress of 100 psi along with a minimum drill hole size of

4 inches. A safety factor of 2 against bolt failure was used for the design.

5.4 ANALYSIS RESULTS

5.4.1 Dips Analysis

The Dips analysis was used to determine the orientations of joint planes within the rock mass from the data provided in the geophysical report. The results of the analyses for eastern and northern facing rock slopes are provided in Appendix A and B, respectively. Generally, only one principal joint orientation was encountered. The average dip angle and dip azimuth of this orientation are as follows:

Dip Angle Dip Azimuth

35 098

Examining the planar sliding, wedge sliding, and toppling failure envelopes in Dips, it was identified that the most likely failure mode for eastern facing slopes is planar sliding. A majority of the fractures encountered during the geophysical testing program fall within this failure envelope. The most likely failure mode for the northern facing slopes is wedge sliding.

However, based on the number of fractures falling within the wedge sliding failure envelope, it is considered that this failure mode is less likely to occur.

5.4.2 Eastern Facing Rock Slopes

Since the predominant strike and dip angles of most of the fractures encountered during the geophysical testing program are generally in the same orientation as the rock face, analysis of the eastern facing rock slopes was performed assuming planar sliding as the failure mode. The

RockPlane computer program was used to perform this analysis. The principal joint orientation from the Dips output and the slope angle of 85 degrees were used to determine the rock bolt force required to retain a wedge formed by the intersection of these planes. It was assumed that wedges larger then approximately 24 ft in height are unlikely to form and that wedges will generally be continuously encountered along the length of slope.

The results of this analysis indicate that 15 to 18 tons of rock bolt force per foot of rock slope per bench is required to stabilize the rock mass with a factor of safety of 2. Based on this, it is recommended that a rock bolt spacing of approximately 6 ft horizontally and vertically be used with rock bolts varying in length from 15 ft to 30 ft.

The recommend rock bolt configuration for eastern facing slopes is shown in Figure 11. The results of the analyses for eastern facing slopes are included in Appendix A.

5.4.3 Northern Facing Rock Slopes

The Dips analysis of the northern facing slopes generally indicates that the overall stability of these slopes will be greater than those facing east. However, some amount of unstable rock wedges are likely to be encountered upon excavation. In order to estimate the required number of rock bolts, the Dips output was input into the Swedge computer program for a slope angle of 85 degrees. Based on the combinations of joints likely to occur, the program produced 414 probable unstable wedges. Rock bolts having a design capacity of 33 tons were sufficient to stabilize all wedges, resulting in a minimum factor of safety of 2. Considering the number of unstable wedges likely to be encountered on the northern facing slopes as determined using Swedge, and the percentage of joints falling within the failure envelope as determined using Dips, it is recommended that a rock bolt spacing of approximately 10 ft horizontal and vertical be used with rock bolt lengths varying from 20 ft to 30 ft.

The recommended rock bolt configuration for northern facing slopes is shown in Figure 11.

The results of the analyses for northern facing slopes are included in Appendix B.

5.4.4 Rock Bolt Structural Design

Based on the maximum required rock bolt capacity and cost per rock bolt, it is recommended that the rock bolts consist of 1 inch nominal diameter, Grade 150, galvanized, all-thread bar.

The size of the bearing plate should be a minimum of 6 inch by 6 inch by 1 ¼ inch thick.

SECTIONSECTIONSECTIONSECTIONSIX Protection Protection Protection Protection Against Long(Term Rock Falls

6.1 GENERAL

As discussed in Section 5.1, the preferred rock slope geometry is to include a series of benches cut into the rock slope, with rock fall retention fences installed along each bench and along the toe of slope. The purpose of the analysis described in this section of the report is to evaluate the long-term stability of the rock slope in terms of containment of small post-construction rock falls.

6.2 ANALYSIS APPROACH

Analyses were performed to evaluate the preferred slope geometry in the case of relatively small rock blocks falling subsequent to the final construction. For this purpose, various slope configurations were modeled using the Colorado Rockfall Simulation Program, version 4.0

(CRSP), which was developed by the Colorado Department of Transportation, the Colorado

School of Mines, and the Colorado Geological Survey. This computer program can be used for locating and designing rockfall mitigation. It simulates rocks tumbling down a slope, and predicts the statistical distribution of speed and bounce height of these blocks. The model takes into account slope profile, rebound and friction characteristics of the slope and rotational energy of the rocks. Spherical, cylindrical and disk shaped rocks can be simulated. At each impact, the slope angle is randomly varied from the nominal value input by the user within the limit set by the maximum probable variation in the slope.

Numerous geometries were evaluated varying the slope angle, bench width, number of benches, height of rockfall fencing, and distance of the rockfall fencing from the toe of the slope.