GeotechMemo_WV ERFO FS 2016-1(5) FINAL.pdf

Form FHWA-201

(Rev. 11-67)

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

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P a g e | 1 cc: TS Reading, Highway, Bridge.

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SUBJECT: Project WV ERFO FS 2016-1(5) –Geotechnical Findings for ERFO projects in the Monongahela National Forest, WV

TO MESSAGE/COMMENT FROM/DATE

R. Kotadia Project Manager

Through:

S.

Whittemore Project Management Branch Chief

INTRODUCTION

This Geotechnical Memorandum summarizes the results of the subsurface exploration and laboratory testing, for the projects along Forest Service Road (FSRD) 86, Mile Posts (MP) 5.9 and 6.7 in the Monongahela National Forest, in Pocahontas County, West Virginia as shown in Figure No. 1.

GENERAL PROJECT INFORMATION

Background

Monongahela National Forest Service was devastated by a 1000-year storm between June 23 and June 26, 2016 causing widespread road damage that included slope slides, loss of pavement surfacing, shoulder and embankment washouts, heavy rutting, and structural damage.

Project Description

Mile Post 5.9

Replacement of two existing double 54-inch pipe culverts with a reinforced concrete box culvert.

Mile Post 6.6

Replacement of the damage timber bridge with a reinforced concrete one.

Regional Geology

The Geologic Map of West Virginia (1968) indicated that the project sites are located within the Bluestone and Princeton (Mbp), and Hinton (Mh) formations.

These geologic formations are briefly described below:

Mbp, Bluestone formation is mostly red, green, and medium-gray shale and sandstone, and Princeton formation is underneath bluestone formation.

Mh, Hinton formation is red, green and medium-gray shale and sandstone, with a few thin limestone beds, including the Avis.

The geologic map of the area is provided in Appendix A.

J.

Herrera, PE, Geotechnical Engineer

M.

Abouzakhm, PE

Division Geotechnical Engineer

Through:

L.

O’ Brien Technical Services Engineer

3/5/2019 DRAFT

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

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PROCEDURES AND RESULTS

General

A subsurface exploration program was conducted on July 30th and 31st, 2017 by EFLHD Subsurface Exploration Team. The program consisted of drilling one

(1) boring or one (1) rock core in the proximity of each structure. The borings were advanced to their termination depth using CME 750 ATV-mounted rotary drill rig. The boring locations were selected by EFLHD geotechnical engineer based on the location of existing structures, presence of underground utilities, and accessibility of the drilling equipment.

Sampling

Due to the anticipated presence of cobbles and boulders at the boring locations, the borings were advanced using rotary drilling techniques and samples were retrieved using a double-walled NQ wireline core barrel.

Boring locations were determined in the field by measuring distances from features present on-site and by a hand-held GPS. Boring elevation was determined from plan topography. The approximate boring locations are provided in the Boring Location Map in Appendix B.

Core samples were preserved in a wooden box and transported to EFLHD’s Materials Testing Laboratory in Sevierville, TN for testing and storage. The sampling sequence and associated samples for the boring are presented in the boring logs in Appendix C.

Data Summary

The results of the field tests and measurements were recorded on the driller’s logs and appropriate data sheets in the field. These data sheets and logs contain information concerning the boring methods, samples attempted and recovered, indications of materials encountered. They also contain interpretations by the exploration foreman of the subsurface conditions based on the performance of the equipment and cuttings brought to the surface by the drilling tools.

Therefore, the field data represents both factual and interpretative information.

The boring logs in Appendix C represent a compilation of field and laboratory data and description of the soil and rock samples by the geotechnical engineer.

These records occasionally do not include all data recorded on driller’s logs and field data sheets, but do include all information considered relevant to the design and preparation of this report.

LABORATORY TESTING

An Unconfined Compressive Strength (UCS) test, following ASTM 7012 standards, was conducted on a representative rock sample to evaluate the strength of the bedrock. The laboratory testing result is presented in Appendix D and is listed in Table No. 1

DRAFT

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P a g e | 3 Table No. 1 Summary of UCS Laboratory Test Result.

Boring No.

Run No.

Depth (ft) Depth of Sample (ft)

Rock Type

RQD

UCS

(psi)

CH17-05 R-4 13.8 to 18.8 17.5 to 18.1 Sandstone 38 6,040

RQD: Rock Quality Designation

UCS: Unconfined compressive strength.

FINDINGS

A brief description of the soil and rock conditions encountered during the subsurface exploration conducted at the project is presented below. The stratification lines designating the interfaces between soil types on the boring logs represent approximate boundaries. See Appendix C for more detail information.

Boring CH17-06 (FSRD 86, MP 5.9)

Fill

Fill material consisting primarily of conglomerate was encountered to a depth

18.8 feet below the existing site grade. RQD values within this layer ranged from 0% to 62%.

Bed Rock

Underneath the conglomerate stratum hard, red, sound, shale was encountered to the termination depth of the boring (i.e., to a depth of 23.8 feet below existing site grades). RQD values for the shale rock layer was 100%, indicating excellent rock quality.

Boring CH17-05 (FSRD 86, MP 6.7)

Fill

Fill material consisting primarily of conglomerate was encountered to a depth of

13.9 feet below the existing site grade. RQD values of 0% was recorded in this layer.

Bed Rock

Underneath the conglomerate strata, light gray, weathered to slightly weathered, very poor to excellent quality, sandstone rock was encountered to the termination depth of the boring. RQD values ranging from 20% to 90% were recorded within this stratum. A rock sample yielded an Unconfined Compressive Strength of 6,040 psi. This indicates a medium strong (R3) strength rock according to (FLH, 2017).

Groundwater

Reliable groundwater level readings were not obtained during drilling since water was used for coring.

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GEOTEHNICAL EVALUATION AND DESIGN ATERNATIVES

Based on the results of our subsurface exploration program and anticipated design loads, we concluded that the proposed bridge at MP 6.7 can be supported on a system of footings.

The proposed bridge shall be supported on spread footings with a base elevation of 2829 feet. The factored bearing resistance (qR) of the conglomerate material is shown in Table No. 2. The factored bearing resistance is dependent of the effective foundation width, in which is defined as B = B − 2e. See Appendix E for bearing resistance computations.

Table No. 2

Factored Bearing Resistance (qR)

B' (ft) qR (psf) B' (ft) qR (psf)

5.0 6,400 7.6 9,700

5.2 6,600 7.8 10,000

5.4 6,900 8.0 10,300

5.6 7,200 8.2 10,500

5.8 7,400 8.4 10,800

6.0 7,700 8.6 11,000

6.2 7,900 8.8 11,300

6.4 8,200 9.0 11,500

6.6 8,500 9.2 11,800

6.8 8,700 9.4 12,100

7.0 9,000 9.6 12,300

7.2 9,200 9.8 12,600

7.4 9,500 10.0 12,800

CONSTRUCTION CONSIDERATIONS

Excavation and Foundation Preparation

All excavations are to be performed according to Subsection 208.03 of FP-14, OSHA, County, and local regulations. Backfill and compact irregular foundation surface with foundation fill according to Subsection 208.08(d). Foundation fill material shall meet Subsection 704.01 specifications.

Backfill Material and Compaction

Backfilling behind bridge abutments shall follow Subsection 258.06 of FP-14.

Backfill material should be structural backfill meeting requirements of subsection 704.04. It should be placed and compacted in accordance with subsection 209.10, except use an approved lightweight mechanical or vibratory compactor within 36 inches of the abutment wall.

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P a g e | 5 Ground and Surface Water Management

Control of storm or seepage water flowing into open excavations and through soil strata will be necessary to maintain dry conditions during construction. The contractor should control the flow of surface and seepage water into excavations at all times.

DISCLAIMER/LIMITATIONS CLAUSE

The subsurface explorations and test described in the section Procedures and Results of this memorandum have been conducted in accordance with standard practices and procedures (except as specifically noted). The results of these exploration and test represent conditions at the specific locations indicated.

Subsurface conditions beyond these locations may vary. The Analyses Recommendations sections of this memorandum include interpretations and recommendations developed by the Government in the process of preparing the design. These interpretations are not intended as a substitute for the personal investigation, independent interpretation, and judgment of the Contractor.

REFERENCES

AASHTO, 2017. AASHTO LRFD Bridge Design Specification. 8th ed.

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

Cardwell, D. H., Erwin, R. & Woodward, H. P., 1968. Geologic Map of West Virginia, Map 1, Scale 1:125,000, s.l.: West Virginia Geological and Economic Survey.

FHWA, 2014. Standard Specifications For Construction of Roads and Bridges on Federal Highway Projects, Washington D.C.: US Department of Transportation.

FLH, 2017. Rock Characterization Guidelines, Washington D.C.: US Department of Transportation - FHWA.

FLH, 2017. Soil Description and Identification Guidelines, Washington D.C.:

US Department of Transportation - FHWA.

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APPENDIX:

Appendix A – Figures

Appendix B – Boring Location Maps

Appendix C – Boring Logs

Appendix D – Laboratory Test Results

Appendix E – Design Computations

Appendix F – Preliminary Construction Plans

Appendix A-1

APPENDIX A – FIGURES

Appendix A-2

FEDERAL LANDS HIGHWAY DIVISION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

STERLING, VIRGNIA

FIGURE NO. 1

Site Location and Vicinity

Map

REG STATE PROJECT

SHEET

NO.

TOTAL

SHEETS

9 WV WV ERFO FS 2016-1(5) 1 2

Appendix A-3

Geologic Map of West Virginia

West Virginia Geological and Economical Survey

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL LANDS HIGHWAY DIVISION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

STERLING, VIRGNIA

FIGURE NO. 2

Geologic Map

REG STATE PROJECT

SHEET

NO.

TOTAL

SHEETS

9 WV WV ERFO FS 2016-1(5) 2 2

MP 5.9 – Box Culvert Construction MP 6.7 – Bridge Construction

Appendix A-4

APPENDIX B – BORING LOCATION MAPS

Appendix A-5

Appendix A-6

Appendix A-7

APPENDIX C – BORING LOGS

Appendix A-8

Appendix A-9

Appendix A-10

Appendix A-11

APPENDIX D – LABORATORY TEST RESULTS

Appendix A-12

Table No. 3: Unconfined Compressive Strength (UCS) Laboratory Test Results accordance to ASTM D7012.

Road Mile Post

Boring No.

Sample No.

Depth (ft.)

Maximum Load (lbs.)

UCS

(psi)

FSRD 86 6.7 CH17-05 R-4 17.5 to 18.1 16,610 6,040

Appendix A-13

APPENDIX E – DESIGN COMPUTATIONS

Appendix A-14

Appendix A-15

Appendix A-16

Appendix A-17

Appendix A-18

APPENDIX F – PRELIMINARY CONSTRUCTION PLANS

Appendix A-19

Appendix A-20

Appendix A-21

APPENDIX G – SELECTED PHOTOGRAPHS

Appendix A-22

Figure 1: Double culvert crossing site (Mile Post 5.9).

Appendix A-23

Figure 2: Double culvert crossing site (Mile Post 5.9).

Figure 3: Single span bridge replacement (Mile Post 6.7).

Appendix A-24

Figure 4: Single span bridge replacement (Mile Post 6.7).