NP BLRI 2D17 Final Geotech Report.pdf

SOILS AND FOUNDATIONS REPORT

REPORT NO. 02-21

PROJECT: NP BLRI 2D17

LAUREL FORK BRIDGE REPLACEMENT AT MILE POST 248.85

BLUE RIDGE PARKWAY

ASHE COUNTY, NORTH CAROLINA

US DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

22001 LOUDOUN COUNTY PARKWAY

ASHBURN, VA 20147

JUNE 21

TABLE OF CONTENTS

1. INTRODUCTION

1.1. General

1.2. Project Description

2. GEOLOGY

2.1. Regional Geology

3. SUBSURFACE EXPLORATION PROGRAM

3.1. Drilling and Sampling

3.2. Data Summary

3.3. Laboratory Testing

4. SUBSURFACE CONDITIONS

4.1. Stratification

4.2. Groundwater

5. DESIGN ANALYSIS

5.1. General

5.2. Drilled Shaft Foundation Design Requirements

5.3. Mechanically Stabilized Earth Wall Design Requirements

6. RECOMMENDATIONS

6.1. Recommendations for Drilled Shaft Foundations

6.2. Recommendations for MSE Walls

7. REFERENCES

8. DISCLAIMER/LIMITATIONS CLAUSE

APPENDICES

Appendix A – Figures Appendix B – Boring Location Plan Appendix C – Subsurface Profile Appendix D – Boring Logs Appendix E – Laboratory Testing Appendix F – Bridge Plan, Elevation View and Foundation Layout Appendix G – Design Analysis Appendix H – Rock Cores and Site Photographs

Note: Design changes subsequent to publication of this report and prior to the project’s advertisement will be documented by a memo attached after the title page.

ASHE COUNTY, NORTH CAROLINA

PAGE 3 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

SOILS AND FOUNDATIONS

REPORT NO. 02-21

BLUE RIDGE PARKWAY

ASHE COUNTY, NORTH CAROLINA

1. INTRODUCTION

1.1. General

This report summarized the results of the subsurface exploration, laboratory testing, design analyses, and presents recommendations for the replacement of the Blue Ridge Parkway (BLRI) Laurel Fork Bridge. The project site is in Ashe County, North Carolina. The site location and vicinity map are in Appendix A.

1.2. Project Description

The existing Bridge is a 5-span, two-girder steel bridge with cast-in-place concrete deck. It is 546 feet long, 28 feet wide, and was built in 1939. The bridge condition assessment and concrete study of January 2017 identified severe cracking (up to ¼” wide cracks) throughout the bridge piers. Representative concrete cores were taken from the piers yielded compressive strengths of 1,900 and 2,100 PSI at Pier 3 and Pier 1 respectively (JWH & JMT, 2018).

Proposed for construction at the site is a 545 long, 3-span concrete box girder bridge. Design drawings are in Appendix F.

2. GEOLOGY

2.1. Regional Geology

The project site is located within the West Half of the Winston-Salem quadrangle and is underlain predominantly by Precambrian or Paleozoic metamorphic gneiss and schist rocks. According to the “Geologic Map of The West Half of the Winston-Salem Quadrangle”, North Carolina, Virginia, and Tennessee Geologic Survey (1972), the project site lies within a laminated mica gneiss and schist formation, a younger formation than the Ashe Formation. The gneiss rock is described as finely laminated composed of fine grained quartzo -feldsphatic layers, or amphibolite, garnet amphibolite, and hornblende interlayered with biotite-muscovite gneiss and mica schist. The geologic map of the project site is in Appendix A.

3. SUBSURFACE EXPLORATION PROGRAM

3.1. Drilling and Sampling

A subsurface exploration program consisting of drilling five (5) soil borings (BH19-01 through BH19-05) was conducted to characterize subsurface conditions. Drilling was performed by the EFLHD subsurface

ASHE COUNTY, NORTH CAROLINA

PAGE 4 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

exploration team between April and May 2019, and in December 2019. Table No. 1 contains a summary of field data. Borings Location Map is in Appendix B.

Table No. 1: Field Data

Boring No. Location Northing Easting Surface Elev. (ft) Depth (ft) BH19-01 Abutment 2 967722.29 1335083.49 2920.94 88.9 BH19-02 Pier 3 967740.45 1334911.14 2863.00 34.0 BH19-03 Pier 2 967802.75 1334687.46 2840.50 28.8 BH19-04 Abutment 1 967839.47 1334523.07 2924.00 64.1 BH19-05 East Approach 1335223.75 967700.40 2921.00 50.0

Borings were drilled using a CME 750 drill rig mounted on a rubber tired all-terrain vehicle (ATV).

Boreholes were advanced using 3-¾-inch (ID) hollow stem augers (HSA) in soil. Borings were terminated upon reaching auger refusal or the planned boring depth, whichever encountered first. The locations were laid out by EFLHD personnel in the field by referencing topographic features, measuring distances from existing surface features, or by using hand-held GPS units.

Soil samples were obtained using a standard split-barrel (split-spoon) sampler driven during Standard Penetration Tests (SPT) in general accordance with AASHTO T 206, Standard Method of Test for Penetration Test and Split Barrel Sampling of Soils. SPT was performed by driving the split-spoon sampler a distance of 24 inches into relatively undisturbed soil under the impact of a 140-pound automatic hammer free falling 30 inches. The number of blows required to advance the sampler through each 6-inch interval was recorded on field boring logs. The number of hammer blows required to advance the split-spoon sampler the middle foot of the upper 18-inch sample interval is designated as the “Standard Penetration Resistance” or N value. The relative soil density and consistency terms provided on the boring logs are based on the N values. SPT was generally performed at 2.5-foot interval in the upper 20 feet and at 5-foot intervals thereafter.

Upon completion of each SPT, the sampler was removed from the ground and sample recovery measurements were made and recorded for each sampling event. A field description by color, texture and moisture was made for each recovered sample. Representative portions of the split-spoon samples were preserved in glass jars.

Rock coring was performed in four (4) borings (BH19-01 through 04) upon encountering auger refusal.

Rock cores were retrieved using a double-walled NQ wire line core barrel. Rock samples recovered were visually examined and percent core recovery (CR) and rock quality designation (RQD) were determined for each core run to provide a quantitative basis for evaluation of the condition of the rock. Rock core samples were preserved in wooden boxes.

Soil and rock core samples were then delivered to the EFLHD Materials Testing facility in Sevierville, TN for testing and storage. Details on sampling and sample descriptions are provided in the boring logs included

ASHE COUNTY, NORTH CAROLINA

PAGE 5 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

in Appendix D. Borings were backfilled with auger cuttings and patched with cold mix asphalt, when needed.

3.2. Data Summary

Data collected during our drilling operations was recorded in the driller’s logs. These data sheets and logs contain the boring methods, samples attempted and recovered, indications of the presence of various materials such as fines, sands, and gravel, organic matter, and observations of groundwater. The logs also contain interpretations 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 represent both factual and interpretative information.

The boring logs provided in Appendix D represent a compilation of field and laboratory data and description of the soil samples by a 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.

Groundwater levels, when encountered, were measured in the boreholes at the times and under the conditions stated in the boring logs. Fluctuations in groundwater level due to seasonal variations, rainfall, temperature, and other factors not evident at the time measurements could be expected.

3.3. Laboratory Testing

Laboratory testing was performed on representative soil samples recovered during the subsurface exploration to aid in the classification, and the evaluation of engineering parameters of the subsurface materials. The following tests were performed on selected samples.

Grain Size Distribution (AASHTO T-11 and T-27) Moisture Content (MC) (AASHTO T-265) Atterberg Limits (Plastic Limit – PL, AASHTO T-90) (Liquid Limit – LL, AASHTO T-89)

Representative rock core samples were tested to evaluate the Unconfined Compressive Strength (UCS) of the underlying bedrock at the site followed ASTM D7012. Electrochemical testing was conducted on representative soil samples and included pH, Sulfate, Chloride contents following AASHTO T 289, AASHTO T 290 and AASHTO T 291 respectively.

Table No. 2 presents a summary of soils laboratory test results and Table No. 3 presents a summary of rock core UCS test results along with Recovery and Rock Quality Designation (RQD) data. Copies of laboratory test results are provided in Appendix E.

ASHE COUNTY, NORTH CAROLINA

PAGE 6 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

Table No. 2: Summary of Soil laboratory test results

Boring No.

Sample No.

Depth (ft)

Gravel

Sand

Fines

MC

PL

LL

(%) pH AASHTO

Classification USCS

BH19-01 J-9 20-22 27.0 62.4 10.6 12.7 NP NV - A-1-b SP-SM

BH19-01 J-12 35-37 16.2 73.8 10.0 9.3 NP NV 8.2 A-3 SP-SM

BH19-02 J-5 10-12 8.8 73.1 18.1 43.0 NP NV - A-1-b SM

BH19-01 J-14 45-47 1.3 81.1 17.6 14.1 NP NV - A-2-4(0) SM

BH19-04 J-7 15-17 31.1 53.5 15.4 17.0 NP NV - A-1-b SM

BH19-04 J-10 25-27 12.2 76.9 10.9 20.1 NP NV 7.2 A-2-4(0) SP-SM

BH19-04 J-12 35-37 0.4 86.70 12.9 27.6 NP NV - A-2-4(0) SM

BH19-02 J-4 8-10 10.3 74.7 15.0 25.9 NP NV 7.5 A-2-4(0) SM

BH19-01 Bucket - 28.5 46 25.5 - NP NV - A-2-4(0) SM

BH19-03 J-3 10-12 0.7 75.5 23.8 8.5 NP NV - A-2-4(0) SM

BH19-01 J-11 30-32 1.7 79.3 19.0 20.5 NP NV 7.9 A-2-4(0) SM

BH19-05 J-4 8-10 0.0 84.2 15.8 16.7 NP NV 8.0 A-2-4(0) SM

BH19-05 J-11 30-32 0.0 81.7 18.3 21.5 NP NV - A-2-4(0) SM

Table No. 3: Summary of Rock UCS results

Boring No. Sample No. Depth (ft) Recovery (%) RQD (%) UCS (psi)

BH19-02 R-1 22.0 87 58 990

BH19-02 R-2 28.0 100 100 830

BH19-02 R-3 32.2 100 100 1,720

BH19-01 R-2 54.9 73 38 660

BH19-01 R-3 59.5 100 90 470

BH19-04 R-1 45.8 69 64 1,150

BH19-04 R-2 50.2 77 45 670

BH19-03 R-1 15.3-18.3 100 41 2,360

BH19-03 R-2 18.8-23.8 100 93 680

4. SUBSURFACE CONDITIONS

4.1. Stratification

A brief description of the subsurface conditions encountered during our field exploration is presented in this section. In addition, boring logs and a subsurface profile are in Appendix C. It is important to note that stratification lines designating the interfaces between layers on the boring logs and the subsurface represent approximate boundaries while the transition between materials may be gradual. It should be noted that one or more of the units may be absent at specific locations.

ASHE COUNTY, NORTH CAROLINA

PAGE 7 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

In general, soils encountered in the borings were predominantly micaceous, very loose to very dense silty sand and poorly graded sand with silt and gravel.

The subsurface profile was classified into the following strata:

Pavement and base course

Asphalt pavement was encountered in BH19-01, BH19-04 and BH19-05. Pavement thickness varied from

5.0 to 10.0 inches and the underlying base layer varied from 3.0 to 5.0 inches.

Silty Sand and Poorly Graded Sand with Silt and Gravel

Underneath the base course layer, and in the remaining 2 borings, Silty Sand and Poorly Graded Sand with Silt and Gravel was encountered to depths of 15 ft. to 53 ft. below existing site grades. SPT N-values recorded ranged from Weight of Hammer (WOH) to greater than 50 blows per foot (bpf) indicating very loose to very dense relative densities.

Bedrock - Gneiss Rock

Underlying the Silty Sand and Poorly graded Sand with Silt and Gravel, bedrock described as dark gray, fine grained, slightly to highly weathered, very weak to weak gneiss was encountered to the Borings termination depths. Rock discontinuities ranged from closely to extremely closely spaced and in fair condition, joints and fractures ranged from 20° to 70° from horizontal. RQD values ranged from 38% to 100% and UCS ranged from 470 psi to 2,360 psi.

4.2. Groundwater

Groundwater was encountered at a depth of 43.3 ft below existing site grades in boring BH19-05. However, fluctuations in groundwater levels could be expected due to seasonal variations, precipitation, evaporation, and surface water runoff. Groundwater level readings were made at the times and under the conditions stated on the boring logs. Subsequent readings were not made in cored borings since water was introduced for rock coring.

5. DESIGN ANALYSIS

5.1. General

We performed our analysis in accordance with “AASHTO LRFD Bridge Design Specifications, 9th Edition”.

5.1.1. Foundation Type Considerations

It is our opinion that the new bridge abutments and piers can be supported on drilled shafts socketed into the bed rock. Shallow foundation option was not a cost-effective approach due to the anticipated depths to bedrock.

ASHE COUNTY, NORTH CAROLINA

PAGE 8 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

5.1.2. Retaining Wall Type Considerations

It is our opinion that an MSE, with a stone facing, retaining wall represents the most suitable alternative to accommodate the road prism in the bridge approaches. Reinforced concrete cantilever type retaining walls are likely to me more expensive and are not esthetically favorable.

5.2. Drilled Shaft Foundation Design Requirements

The Axial and Lateral resistance of Drilled Shaft foundations was conducted in general accordance with FHWA-GEC-010, “Drilled Shafts: Construction Procedures and Design Methods, (2018)”, and following “AASHTO LRFD Bridge Design Specifications, 9th Ed.” (2020) design requirements. A summary of soil and rock engineering parameters used in the analyses is presented in Table No. 4 and Table No. 5.

Table No. 4: Assumed soil parameters for bridge foundations

Substructure Material Type

Depth from surface (ft)

Unit Weight

(pcf)

Cohesion (psf)

Internal Friction Angle ϕ k (pci)

Abutment No. 1 SM / SP-SM /SM 0.0 – 45.2 115 - 120 0.0 28° - 32° 93 Pier No. 1 SP-SM / SM 0.0 – 15.3 115 - 125 0.0 30° - 38° 46 Pier No. 2 SM / SP-SM / SM 0.0 – 19.1 115 - 130 0.0 26° - 38° 116

Abutment No. 2 SM / SP-SM / SM 0.0 – 45.0 110 - 120 0.0 26° - 34° 35 - 93

Table No. 5: Assumed rock parameters for bridge foundations

Substructure Rock Type

Depth from surface (ft)

Unit Weight (pcf) RMR1 GSI2

Abutment No. 1 Gneiss 45.2 – 64.1 140 - 150 30 - 40 25 - 43 Pier No. 1 Gneiss 15.3 – 28.8 140 - 150 21 - 50 36 - 60 Pier No. 2 Gneiss 19.1 – 34.0 140 - 150 25 - 45 40 - 66

Abutment No. 1 Gneiss 45.0 – 88.9 140 - 150 21 - 45 20 - 32 1 RMR: Rock Mass Rating 2 GSI: Geologic Strength Index

The resistance factors used for the geotechnical design of the drilled shafts of bridge abutments and piers are presented in Table No. 6, following AASHTO Section 10.5.5.2.4.

Table No. 6: Drilled shaft design resistance factors.

Analysis Resistance Factor Nominal Axial Compressive Resistance of Single Drilled Shaft, Tip Resistance in Rock 0.50

Nominal Axial Compressive Resistance of Single Drilled Shaft, Side Resistance in Rock 0.50

Nominal Axial Compressive Resistance of Single Drilled Shaft, Side Resistance in Sand 0.55

ASHE COUNTY, NORTH CAROLINA

PAGE 9 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

Nominal Axial Compressive Resistance of Group Drilled Shaft, Tip and Side Resistance Rock 0.55

Uplift Resistance of Single Drilled Shaft, Side Resistance in Sand 0.45

Uplift Resistance of Single Drilled Shaft, Side Resistance in Rock 0.40

Group Uplift Resistance, Side Resistance in Sand and Clay 0.45

Horizontal Geotechnical Resistance of Single Shaft 1.00

Horizontal Geotechnical Resistance of Group Shaft 1.00

Bridge axial resistance analysis computations were performed using PTC Mathcad Prime v. 7.0 software program, the horizontal resistance analysis computations were performed using LPILE 2019, and global stability analysis using the computer program Slide2 v. 9.012 by Rocscience, Inc. Design calculations and computer output files are included in Appendix G.

The results of our subsurface exploration were used to determine the Seismic Site Class and Seismic Zones for the project site following AASHTO section 3.10. SPT N-values of soil samples were used to classify the project site. The project site can be classified as Seismic Site Class D, and a Seismic Zone 1. The Seismic Design Maps presented in AASHTO section 3.10.2.1 was used to determine the Horizontal Peak Ground Acceleration (PGA), and the short and long period spectral acceleration coefficients (SS, 0.2-seconds) and (S1, 1.0-second) respectively. The coefficients are based on a uniform risk model of seismic hazard and follow a seven percent (7%) probability of exceedance in seventy-five (75) years. Copies of Seismic Hazard analysis calculations are included in Appendix G.

5.3. Mechanically Stabilized Earth Wall Design Requirements

The external stability of the MSE walls was conducted using limit equilibrium methodology, in general accordance with the design concepts and procedures presented in FHWA Publication FHWA-GEC 011, “Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes,” (2010), and following “AASHTO LRFD Bridge Design Specifications, 9th Ed.” (2020) design requirements.

Please note that, it is the contractor’s responsibility to perform internal stability analysis of the proposed MSE wall. This analysis should include, but not limited to, the following:

Tensile resistance of reinforcement Pullout resistance of reinforcement Facing Design Facing-Reinforcement connection Compound Stability Analysis

ASHE COUNTY, NORTH CAROLINA

PAGE 10 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

A summary of soil engineering parameters assumed in the External stability analyses is presented in Table No. 7

Table No. 7: Select Granular Backfill parameters for MSE retaining walls.

Location Material Type

Unit Weight (pcf)

Cohesion (psf)

Internal Friction Angle ϕ

West and East Approach Select Granular Backfill 120 - 125 0 34°

West Approach SM / SP-SM /SM 115 - 120 0.0 28° - 32°

East Approach SM / SP-SM /SM 110 - 120 0.0 26° - 34°

A uniform distributed live surcharge load of 240 psf was applied along the travel way to account for traffic loading following Section 3.11.6.4.

The selected load factors and combinations are presented in Table No. 8. The factors follow AASHTO Section 3.4.1. The resistance factor used for design for both sites are presented in Table No. 9, following AASHTO Section 11.5.7.

Table No. 8: MSE walls design load factors and combinations for External Stability.

Load Combination EH EV ES LS DC Strength I (Max) 1.50 1.35 1.50 1.75 1.25 Strength I (Min) 0.90 1.00 0.75 1.75 0.90

Service I 1.00 1.00 1.00 1.00 1.00

Table No. 9: MSE walls design resistance factors for External Stability.

Analysis Resistance Factor Sliding Φs: 1.00 Bearing Φb: 0.65

Overall/Global ΦG: 0.75 (FSG:1.33)

External stability analysis computations were performed using PTC Mathcad Prime v. 7.0 software program, and global stability analysis using the computer program Slide2 v. 9.012 by Rocscience, Inc.

Design calculations and computer output files are included in Appendix G.

According to AASHTO 11.5.4.2, a seismic design shall not be considered mandatory for walls located in Seismic Zones 1 through 3, or for walls located in areas where the adjusted Peak Ground Acceleration (As) is less than or equal to 0.4g, unless one or more of the following is true:

Liquefaction induced lateral spreading or slope failure, or seismically induced slope failure, due to the presence of sensitive clays that lose strength during the seismic shaking, may impact the stability of the wall for the design earthquake.

ASHE COUNTY, NORTH CAROLINA

PAGE 11 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

The wall supports another structure that is required, based on the applicable design code or specification for the supported structure, to be designed for seismic loading and poor seismic performance of the wall could impact the seismic performance of that structure.

In addition, according to C11.5.4.2, a seismic analysis should be considered mandatory if the wall is located in seismic zone 2 or higher, and if either of the following is greater than 30 feet:

The exposed wall height plus the average depth over the width of the wall of any soil surcharge present.

For tiered walls, the sum of the exposed height of all the tiers plus the average soil surcharge depth.

Based on the above listed criteria, it was concluded that the retaining structures do not require an external or internal seismic evaluation, as applicable, due to an adjusted PGA less than 0.4g, and the retaining structures are in Seismic Zone 1 to 3. However, an Extreme Event I global stability analysis is required for all sites. For this analysis, it was assumed an allowable lateral deformation based on the flexible nature of the type of structure. See the evaluation calculations in Appendix G.

6. RECOMMENDATIONS

6.1. Recommendations for Drilled Shaft Foundations

The estimated lengths and geotechnical axial and uplift resistance for the drilled shafts are shown in Tables No. 10 and No. 11. The geotechnical axial and uplift resistance includes the single and group scenarios for each bridge substructure element and follows the bridge Foundation Layout shown in “Appendix F – Bridge Plan, Elevation View and Foundation Layout”.

Table No. 10: Estimated minimum drilled shaft length and rock socket requirements to develop geotechnical axial resistances

Drilled Shaft Geotechnical Axial Load Factored Resistance (kips)

Scenario Structure

Estimated Drilled Shaft Elevation (ft)

Drilled Shaft

Length (ft)

Min Rock Socket Length

(ft)

Total Number of Drilled

Shafts in Cap.

Shaft Diameter (ft)

Top Tip 4 6

Single

Abutment No. 1 2907.4 2868.9 38.5 10 2 - 2,620 Pier No. 1 2831.4 2812.2 19.2 13 6 1,960 - Pier No. 2 2847.1 2830.9 16.2 13 6 3,220 -

Abutment No. 2 2896.0 2857.0 39.0 10 2 - 2,040

Group

Abutment No. 1 2907.4 2868.9 38.5 10 2 - 5,460 Pier No. 1 2831.4 2812.2 19.2 13 6 12,180 - Pier No. 2 2847.1 2830.9 16.2 13 6 20,520 -

Abutment No. 2 2896.0 2857.0 39.0 10 2 - 4,220

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PAGE 12 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

Table No. 11: Estimated minimum drilled shaft length and rock socket requirements to develop geotechnical uplift resistance

Drilled Shaft Geotechnical Uplift Load Factored Resistance (kips)

Scenario Structure

Estimated Drilled Shaft Elevation

(ft)

Drilled Shaft

Length (ft)

Min Rock Socket Length

(ft)

Total Number of Drilled

Shafts in Cap.

Shaft Diameter (ft)

Top Tip 4 6

Single

Abutment No. 1 2907.4 2868.9 38.5 10 2 - 2,760 Pier No. 1 2831.4 2812.2 19.2 13 6 960 - Pier No. 2 2847.1 2830.9 16.2 13 6 1,060 -

Abutment No. 2 2896.0 2857.0 39.0 10 2 - 1,400

Group

Abutment No. 1 2907.4 2868.9 38.5 10 2 - 3,200 Pier No. 1 2831.4 2812.2 19.2 13 6 6,500 - Pier No. 2 2847.1 2830.9 16.2 13 6 7,160 -

Abutment No. 2 2896.0 2857.0 39.0 10 2 - 3,040

The bridge lateral loads are resisted by the soil/structure interaction of the drilled shaft. A fixed drilled shaft pile cap boundary condition was assumed at the top of all shafts. Drilled shaft reinforcement layout and spacing requirements are presented in Appendix F .

A summary of the horizontal geotechnical resistance for single and group drilled shafts is provided in Table No. 12.

Table No. 12: Results of geotechnical horizontal resistance of drilled shafts.

Drilled Shaft Geotechnical Horizontal Analysis Results

Scenario Structure Limit States Maximum Lateral Deflection (in.)

Maximum Shear (kip)

Maximum Bending Moment

(kip-ft.)

Single

Abutment No. 1 Strength 0.104 225 -2,560

Service 0.067 145 -1,650

Pier No. 1 Strength 0.008 50 -260

Service 0.006 40 -210

Pier No. 2 Strength 0.004 50 -190

Service 0.003 40 -150

Abutment No. 2 Strength 0.371 495 -5,450

Service 0.219 320 -3,660

Group Abutment No. 1 Strength 0.122 225 -2,710

Service 0.078 145 -1,750

ASHE COUNTY, NORTH CAROLINA

PAGE 13 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

Pier No. 1 Strength 0.010 50 -320

Service 0.008 40 -210

Pier No. 2 Strength 0.005 50 -240

Service 0.004 40 -150

Abutment No. 2 Strength 0.490 495 5,830

Service 0.259 320 -3,820

6.2. Recommendations for MSE Walls

As stated in Section 5.3, the recommendations presented in this section only covers the external stability of the MSE wall. It is responsibility of the contractor to finalize the design following FP-14 Section 257 and the requirements presented Section 5.3. The MSE wall system varies in height between 7.5 ft. to 25.5 ft, backfilled with select granular backfill within the reinforced soil zone.

A minimum 4 feet bench and a minimum 2 feet embedment is required in front of the wall. In top of the wall, a 1V:2H or flatter embankment fill shall be constructed to catch the roadway system. The wall shall include an underdrain system. To keep wild life out of the retaining wall drainage system a 1/4” mesh should be installed to cover the pipe outlet. The MSE Wall external stability recommendations are presented in Table No. 13.

Table No. 13: MSE Wall external stability recommendations.

NP BLRI 2D17 - MSE Walls Design Recommendations Approach Side HMax

1 (ft) LR 2 (ft) WPad-Min

3 (ft)

Abutment No. 1 MSE Wall A 16.5 12.0 6.5 MSE Wall B 18.0 14.0 6.5

Abutment No 2 MSE Wall C 24.0 18.0 6.5 MSE Wall D 25.5 20.0 6.5

1 HMax: MSE wall maximum height.

2 LR: MSE wall minimum reinforcement length to meet external stability requirements only.

3WPad-Min: MSE wall minimum facing block concrete pad width.

ASHE COUNTY, NORTH CAROLINA

PAGE 14 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

7. REFERENCES

AASHTO-LRFD. (2020). AASHTO LRFD Bridge Design Specifications (9th ed.). Washington, D.C.:

American Association of State Highway and Transportation Officials.

FHWA. (2014). Standard Specifications For Construction of Roads and Bridges on Federal Highway Projects (FP-14). US Department of Transportation. Washington D.C.: US Department of Transportation.

FHWA. (2018). Drilled Shafts: Construction Procedures and Design Methods. Washington, D.C.: U.S.

Department of Transportation.

JWH, & JMT. (2018). Replacement of Blue Ridge Parkway Laurel Fork Bridge, Value Analysis (VA) and Choosing-by-Advantage (CBA) Study. NPS & FHWA.

ASHE COUNTY, NORTH CAROLINA

PAGE 15 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

8. DISCLAIMER/LIMITATIONS CLAUSE

The subsurface explorations and tests described in this report 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 and dates indicated. Subsurface conditions between these locations may vary. In the event of design or location changes in the project after the final report is submitted, the recommendations should be reviewed and possibly modified with our participation. The Geotechnical Design Analyses and Recommendations Sections of this report 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.

Prepared by:

Jonathan Herrera-Roldán, P.E.

Geotechnical Engineer

Reviewed by:

Mounir Abouzakhm, P.E.

Division Geotechnical Engineer

ASHE COUNTY, NORTH CAROLINA

PAGE 16 OF 24 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

ASHBURN, VA

APPENDICES

Appendix A – Figures A - 17

Appendix B – Boring Location Plan A - 18

Appendix C – Subsurface Profile A - 19

Appendix D – Boring Logs A - 20

Appendix E – Laboratory Testing A - 21

Appendix F – Bridge Plan, Elevation View and Foundation Layout A - 21

Appendix G – Design Analysis A - 23

Appendix H – Rock Cores and Site Photographs A - 24

ASHE COUNTY, NORTH CAROLINA

PAGE A - 17 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

STERLING, VA

Appendix A – Figures

ASHE COUNTY, NORTH CAROLINA

DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

Figure No. 1

Figure No. 2

ASHE COUNTY, NORTH CAROLINA

DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

Figure No. 3

ASHE COUNTY, NORTH CAROLINA

DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

Figure No. 4: Geologic Map of The West Half of The Winston-Salem Quadrangle, North Carolina, Virginia, and Tennesse by D.W. Rankin, G.H. Espenshade, and R.B. Neuman (1972).

Map Legend pg, typically finely laminated gneiss composed of fine grained quartzo-feldspathic layers a few millimeters thick separated by very thin micaceous partings; “pin stripe” appearance. Thicker schist and amphibolite layers are common. Gneiss is generally more micaceous than similar units in the Ash Formation. Has some layers of massive gneiss and micaceous granule conglomerate similar to those in the Ash Formation. Magnetite is a common locally abundant, constituent. Epidote is a common constitute of the gneiss, and calc-silicate lenses are locally abundant.

ps, dominantly light gray, green gray to dark gray phyllite and muscovite schist commonly containing garnet and magnetic, both which are locally abundant. Inter-layered with biotite muscovite gneiss and in places with amphibolite.

Quartzite and slightly calcareous beds are present in a few places in the southeasternmost belt.

pa, amphibolite, garnet amphibolite, and hornblende gneiss interlayered with biotite muscovite gneiss and mica schist.

Laurel Fork Bridge Site

ASHE COUNTY, NORTH CAROLINA

PAGE A - 18 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

Appendix B – Boring Location Plan

ASHE COUNTY, NORTH CAROLINA

PAGE A - 19 DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

Appendix C – Subsurface Profile

ASHE COUNTY, NORTH CAROLINA

DEPARTMENT OF TRANSPORTATION

FEDERAL HIGHWAY ADMINISTRATION

Appendix D – Boring Logs

10/04/2018

SOIL CLASSIFICATION CHART

Criteria for Assigning Group Symbols and Group Name Using Laboratory TestsA Group

Symbol Group NameB

COARSE-GRAINED

SOILS

More than 50% retained on No. 200 Sieve

GRAVELS

More than 50% of coarse fraction retained on No. 4 Sieve

Clean GRAVELS Less than 5% fines E

Cu ≥ 4 and 1 ≤ Cc ≤ 3C GW Well-graded GRAVEL D

Cu < 4 and/or 1 > Cc > 3 C GP Poorly-graded GRAVEL D

GRAVELS with fines More than 12% fines E

Fines classify as ML or MH GM Silty GRAVEL D,F Fines classify as CL or CH GC Clayey GRAVEL D,F

SANDS

Less than 50% retained on No. 4 Sieve

Clean SANDS Less than 5% fines I

Cu ≥ 6 and 1 ≤ Cc ≤ 3 C SW Well-graded SAND H

Cu < 6 and/or 1 > Cc > 3 C SP Poorly-graded SAND H

SANDS with fines More than 12% fines I

Fines classify as ML or MH SM Silty SAND F,H Fines classify as CL or CH SC Clayey SAND F,H

FINE-GRAINED

SOILS

50% or more passes the No. 200 Sieve

SILTS and CLAYS Liquid limit less than 50

Inorganic PI > 7 and plots on or above the “A” line J CL Lean CLAY K,L,M PI < 4 or plots below “A” line J ML SILT K,L,M

Organic Liquid limit – oven dried Liquid limit – not dried < 0.75 OL Organic CLAY K,L,M,N

Organic SILT K,L,M,O

SILTY and CLAYS Liquid limit 50 or more

Inorganic PI plots on or above “A” line CH Fat CLAY K,L,M PI plots below “A” line MH Elastic SILT K,L,M

Organic Liquid limit – oven dried Liquid limit – not dried < 0.75 OH Organic CLAY K,L,M,P

Organic SILT K,L,M,Q

HIGHLY ORGANIC

SOILS Primarily organic matter, dark in color, and organic odor PT PEAT A Based on material passing the 3-inch sieve.

B If field sample contains cobbles or boulders, add “with cobbles” or “boulders” or both, to group name.

C Cu = D60/D10 Cc = (D30)2 / (D10 x D60) D If soil contains ≥15% sand, add “with sand” to group name.

E Gravels with 5 to 12% fines require dual symbols:

GW-GM well-graded GRAVEL with silt GW-GC well-graded GRAVEL with clay GP-GM poorly-graded GRAVEL with silt GP-GC poorly-graded GRAVEL with clay

F If fines classify as CL-ML, use dual symbol GC-GM or SC-SM G If fines are organic, add “with organic fines” to group name.

H If soil contains ≥15% gravel, add “with gravel” to group name.

I Sand with 5 to 12% fines require dual symbols:

SW-SM well-graded SAND with silt SW-SC well-graded SAND with clay SP-SM poorly-graded SAND with silt SP-SC poorly-graded SAND with clay J If Atterberg limits plot in hatched area, soil is a CL-ML, silty

CLAY.

K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel”, whichever is predominant.

L If soil contains ≥ 30% plus No. 200, predominantly sand, add “sandy” to beginning of group name.

M If soil contains ≥ 30% plus No. 200, predominantly gravel, add “gravelly” to beginning of group name.

N PI ≥ 4 and plots on or above “A” line.

O PI < 4 or plots below “A” line.

P PI plots on or above “A” line.

Q PI plots below “A” line.

APPARENT DENSITY OF COARSE-

GRAINED SOIL

SPT N-value (blows per foot) Apparent Density

0 to 4 Very Loose

5 to 10 Loose

11 to 30 Medium Dense

31 to 50 Dense

> 50 Very Dense

CONSISTENCY OF

FINE-GRAINED SOIL

SPT N-value (blows per foot) Consistency

0 to 1 Very Soft

2 to 4 Soft

5 to 8 Firm

9 to 15 Stiff

16 to 30 Very Stiff

> 30 Hard

SOIL STRUCTURE TERMS

Stratified Alternating layers of varying material or color with layers > 1/4 inch (6 mm), note thickness and inclination.

Laminated(1) Alternating layers of varying material or color with layers < 1/4 inch (6 mm), note thickness and inclination.

Fissured(1) Breaks along definite planes of fracture with little resistance to fracturing.

Slickensided(1) Fracture planes appear polished or glossy, sometimes striated.

Blocky(1) Cohesive soil that can be broken down into smaller angular lumps which resists further breakdown.

Disrupted Soil structure is broken and mixed. Infers that material has moved substantially -landslide debris.

Homogeneous Same color and appearance throughout.

Lensed Inclusion of small pockets of different soil, such as small lenses of sand scattered through a mass of clay; < 1/4 inch (6 mm) note thickness.

(1) Do not use laminated, fissured, slickensided, or blocky for coarse-grained soils.

Descriptive Terminology for Boring Logs

Field descriptions of borings are based on the FLH Soil and Rock Description and Identification Guidelines that generally follow the Visual-Manual Procedure (ASTM D 2488). The soil classifications shown on the boring logs are based on laboratory tests (ASTM D 2487) when the two-letter group symbol follows the group name in parenthesis.

Standard Penetration Test (SPT): the SPT consists of driving a 2 in (50 mm) O.D. split barrel sampler a depth of 18 in (450 mm) or 24 in (600 mm) using a 140 lb (63.6 kg) hammer with a 30 in (750 mm) drop. The blow count is the number of blows recorded for each 6 inch (50 mm) increment.

The N-value is the total number of blows for the second and third increments. Note that the N-values shown on the boring logs do not include any corrections for non-standard sampler size, hammers, drill rods, etc.

ANGULARITY OF

COARSE-GRAINED SOILS

Angular

Sharp edges and relatively plane sides with unpolished surfaces

Subangular

Similar to angular description, but with rounded edges

Subrounded

Nearly plane sides, but will have well-rounded corners and edges.

Rounded

Smoothly curved sides and no edges

PARTICLE SIZE OF COARSE-GRAINED SOILS

Component Grain Size Limits

Boulders > 12” (> 300 mm)

Cobbles 3 – 12” (75 – 300 mm)

Coarse Gravel 3/4 - 3" (19 - 75 mm)

Fine Gravel #4 Sieve - 3/4" (4.75 - 19 mm)

Coarse Sand #10 - #4 Sieve (2.00 - 4.75 mm)

Medium Sand #40 - #10 Sieve (0.425 - 2.00 mm)

Fine Sand #200 - #40 Sieve (0.075 - 0.425 mm)

10/04/2018

GRAIN/CRYSTAL SIZE FOR ROCKS (MODIFIED AFTER WENTWORTH, 1972)

Grain Size Description Criteria Less than 0.003 inches (<0.075 mm)

Very fine grained Cannot be distinguished by unaided eye. Few to no mineral grains are visible with a hand lens.

0.003 to 0.02 inches (0.075 to 0.425 mm) Fine grained

Few grain/crystal boundaries are visible; grains can be distinguished with difficulty by the unaided eye but can be somewhat distinguished by hand lens.

0.02 to 0.08 inches (0.425 to 2 mm) Medium grained Most grain/crystal boundaries are visible; grains distinguishable by eye and with the aid of a hand lens.

0.08 to 0.2 inches

(2 to 4.75 mm) Coarse grained Grain/crystal boundaries are visible; grains distinguishable with the naked eye and hand lens.

Greater than 0.2 inches

(>4.75 mm)

Very coarse grained

Grain/crystal boundaries are Clearly visible; grains are distinguishable with the naked eye.

GRAIN SHAPE (FOR SEDIMENTARY ROCKS)

Description Characteristic

Angular Showing very little evidence of wear. Grain edges and corners are sharp. Secondary corners are numerous and sharp.

Subangular

Showing definite effects of wear. Grain edges and corners are slightly rounded off. Secondary corners are slightly less numerous and slightly less sharp than in angular grains.

Subrounded Showing considerable wear. Grain edges and corners are rounded to smooth curves. Secondary corners are reduced greatly in number and highly rounded.

Rounded Showing extreme wear. Grain edges and corners are smoothed off the broad curves. Secondary corner are few in number and rounded.

Well-rounded Completely worn. Grain edges or corners are not present. No secondary edges or corners are present. DEGREE OF WEATHERING

Term Description Grade

Fresh No visible sign of rock material weathering; slight discoloration on major discontinuity surface is possible. I

Slightly Weathered

Discoloration indicates weathering of rock material and discontinuity surfaces. All rock material may be discolored by weathering and the external surface may be somewhat weaker than in its fresh condition.

II

Moderately Weathered

Less than half the rock material is decomposed and/or disintegrated to a soil.

Fresh or discolored rock is present either as a discontinuous framework or as corestones. A minimum 2-inch (50 mm) diameter sample cannot be broken readily by hand across the rock fabric.

III

Highly Weathered

More than half of the rock is decomposed and/or disintegrated to soil. Fresh or discolored rock is present either as a discontinuous framework or as corestones.

A minimum 2-inch (50 mm) diameter sample can be broken readily by hand across the rock fabric.

IV

Completely Weathered

All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact. Material can be granulated by hand. If rock is considered to be completely weathered, use FLH Soil Description and Identification Guidelines to describe the residual soil material.

V

Residual Soil

All rock material is converted to soil. The mass structure and material fabric are destroyed but the apparent structure remains intact. There may be a large change in volume, but the soil has not been significantly transported. Material can be easily broken-down by hand. If rock is considered to be completely weathered, use FLH Soil Description and Identification Guidelines to describe the residual soil material.

VI

RELATIVE STRENGTH OF SOIL INFILLING (ISRM, 1978 & 1981)

Grade Description Field Identification Approximate

Uniaxial Compressive

Strength

S1 Very Soft Easily penetrated several inches by fist

<3.5 psi (<25 kPa)

S2 Soft Easily penetrated severl inches by thumb

3.5 - 7 psi (25 - 50 kPa)

S3 Firm

Can be penetrated several inches by thumb with moderate effort

7 - 14.5 psi (50 - 100 kPa)

S4 Stiff

Readily indented by thumb but penetrated only with great effort

14.5 - 36 psi (100 - 250 kPa)

S5 Very Stiff Readily indented by thumbnail

36 - 72.5 psi (250 - 500 kPa)

S6 Hard Indented with difficulty by thumbnail

>72 psi (>500 kPa)

RELATIVE STRENGTH OF INTACT ROCK SPECIMENS (ISRM, 1978 &1981)

Grade Description Field Indentificaiton Approximate Uniaxial Compressive Strength

R0 Extremely Weak Rock Specimen can be indented by thumbnail 35 - 150 psi

(250 - 1,000 kPa)

R1 Very Weak Rock

Specimen crumbles under sharp blow with point of geological hammer, and can be peeled with a pocket knife.

150 - 725 psi (1,000 - 5,000 kPa)

R2 Weak Rock Shallow cuts or scrapes can be made in a specimen with a pocket knife. A firm blow with a geological hammer point creates shallow indents.

725 - 3,500 psi (5,000 - 25,000 kPa)

R3 Medium Strong Rock

Specimen cannot be scraped or cut with a pocket knife.

Specimen can be fractured with a single firm blow with a geologic hammer point.

3,500 - 7,250 psi (25,000 - 50,000 kPa)

R4 Strong Rock Specimen requires more than one firm blow of the geologic hammer point to fracture.

7,250 - 14,500 psi (50,000 - 100,000 kPa)

R5 Very Strong Rock

Specimen requires many firm blows from the hammer end of the geologic hammer to fracture.

14,500 - 36,250 psi (100,000 - 250,000 kPa)

R6 Extremely Strong Rock

Specimen can only be chipped with firm blows from the hammer end of the geologic hammer.

>36,250 psi (>250,000 kPa)

JRC RANGES (ISRM, 1978 &1981)

DISCONTINUITY CONDITION (ISRM, 1978, 1981)

Condition Description

Excellent Condition

Very rough surfaces, no separation, hard discontinuity wall (>R2).

Good Condition

Slightly rough surfaces, separation less than ~0.04 inches (1 mm), hard discontinuity wall (>R2).

Fair Condition

Slightly rough surface, separation greater than ~0.04 inches (1 mm), soft discontinuity wall (<R3).

Poor Condition

Slickensided surfaces, or soft gouge less than ~0.2 inches (5 mm) thick, or open discontinuities between ~0.4 and 0.2 inches (1 to 5 mm).

Very Poor Condition

Soft gouge greater than ~0.2 inches (5 mm), or open discontinuities greater than ~0.2 inches (5 mm).

DISCONTINUITY SPACING (INCLUDES

JOINTS/FRACTURES, BEDDING, AND FAULTS

Description Spacing of Discontinuity Extremely Widely

Spaced >20 feet (>6 m)

Very Widely Spaced

~6 to 20 feet (2 to 6 m)

Widely Spaced ~2 to 6 feet (600 mm to 2 m)

Moderately Spaced

~8 inches to 2 feet (200 to 600 mm)

Closely Spaced ~2 to 8 inches (60 to 200 mm)

Very Closely Spaced

~3/4 to 2 inches (20 to 60 mm)

Extremely Closely Spaced

<3/4 inches (<20 mm)

𝑅𝑅𝑅𝑅𝑅𝑅 (%) =

𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿ℎ 𝑜𝑜𝑜𝑜 𝑆𝑆𝑜𝑜𝑆𝑆𝐿𝐿𝑆𝑆 𝐶𝐶𝑜𝑜𝐶𝐶𝐿𝐿 𝑖𝑖𝐿𝐿 𝑝𝑝𝑖𝑖𝐿𝐿𝑝𝑝𝐿𝐿𝑝𝑝 > 4 𝑖𝑖𝐿𝐿𝑝𝑝ℎ𝐿𝐿𝑝𝑝 (100 𝑚𝑚𝑚𝑚)

𝑇𝑇𝑜𝑜𝐿𝐿𝑇𝑇𝑇𝑇 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿ℎ 𝑜𝑜𝑜𝑜 𝐶𝐶𝑜𝑜𝐶𝐶𝐿𝐿 𝑅𝑅𝑆𝑆𝐿𝐿

𝑥𝑥 100

𝐹𝐹𝐹𝐹 =

𝑁𝑁𝑆𝑆𝑚𝑚𝑁𝑁𝐿𝐿𝐶𝐶 𝑜𝑜𝑜𝑜 𝐿𝐿𝑇𝑇𝐿𝐿𝑆𝑆𝐶𝐶𝑇𝑇𝑇𝑇 𝑜𝑜𝐶𝐶𝑇𝑇𝑝𝑝𝐿𝐿𝑆𝑆𝐶𝐶𝐿𝐿𝑝𝑝

𝑇𝑇𝑜𝑜𝐿𝐿𝑇𝑇𝑇𝑇 𝑇𝑇𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿ℎ 𝑜𝑜𝑜𝑜 𝑝𝑝𝑜𝑜𝐶𝐶𝐿𝐿 𝐶𝐶𝐿𝐿𝑝𝑝𝑜𝑜𝑟𝑟𝐿𝐿𝐶𝐶𝐿𝐿𝑆𝑆 (𝑜𝑜𝐿𝐿𝐿𝐿𝐿𝐿)

𝐶𝐶𝑅𝑅 (%) = �

𝑇𝑇𝑜𝑜𝐿𝐿𝑇𝑇𝑇𝑇 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿ℎ 𝑜𝑜𝑜𝑜 𝐶𝐶𝑜𝑜𝐶𝐶𝐿𝐿 𝑅𝑅𝐿𝐿𝑝𝑝𝑜𝑜𝑟𝑟𝐿𝐿𝐶𝐶𝐿𝐿𝑆𝑆

𝑇𝑇𝑜𝑜𝐿𝐿𝑇𝑇𝑇𝑇 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿ℎ 𝑜𝑜𝑜𝑜 𝐶𝐶𝑜𝑜𝐶𝐶𝐿𝐿 𝑅𝑅𝑆𝑆𝐿𝐿 𝑅𝑅𝐶𝐶𝑖𝑖𝑇𝑇𝑇𝑇𝐿𝐿𝑆𝑆

� ∗ 100

1.2

0.3

0.8

1.3

1.7

1.3

1.1

0.8

1.0

1.7

Asphalt Pavement

Base course

Silty SAND (SM), very loose to loose, brown, moist, non plastic. A-2-4(0). Slightly micaceous

Poorly graded SAND with silt and gravel (SP-SM), very loose to dense, very loose to loose, brown, moist, non plastic. A-1-b and A-3. Slightly micaceous pH: 7.9 (30.0'-32.0' depth) pH: 8.2 (35.0'-37.0' depth)

1.0 4-3-3-2

0-1-1-1

0-1-1-1

WH-1-1-2

WH-WH-WH-1

1-1-1-1

1-1-1-WH

1-2-2-2

3-2-1-1

4-4-5-15

J-1

J-2

J-3

J-4

J-5

J-6

J-7

J-8

J-9

J-10

0.4 0.8

20.0

Project Location:

Encountered at:

After

Caved at:

Hammer Drop:

Rock Core (RQD in %)

(Blows / ft)

2920.9 ft

Undisturbed (UD)

5/15/19

Project Name:

MATERIAL DESCRIPTION

Boring No.:

Groundwater Depth:

Sample Types:

BORING LOG

5/21/19 J. Farley

D. HutchinsOperator:

T yp e

Weather:

SAMPLE

Plastic Limit

Boring was backfilled with auger cuttings and patch with cold mix asphalt.

Groundwater was not encountered during the drilling operation.

HSA was done in 5/15/2019. Rock Coring was done in 5/21/2019.

hrs

Remarks:

Auger Cuttings

G ra ph ic

L og

NP BLRI 2D17 - Replacement of Laurel Fork Bridge

Density, Color, Plasticity, Size, Proportions, Moisture

Surface Elevation:

Boring Location:

La ye r

D ep th ft)

Boring Began:

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

Liquid Limit

SPT

U. S. DEPARTMENT OF TRANSPORTATION

At Completion:

Completed:

S P

T B lo w s pe r in

D ep th S ca le ft)

N o.

Blue Ridge Parkway, MP 248, Ashe County, North Carolina

E le va tio n (f ee t)

3 3/4" Boring Method:

Rock Core Diam:

Vane Shear

30 in.

140 lbs/Automatic

Penetrometer (PP in tsf)

Water Content %

Hole Diameter:

NAD83

BH19-01

Hammer Wt. & Type:

Sunny, 45°F

BLRI MP 248

Standard Penetration Test Data

Project Datum:

Inspector:

R ec ft/

P P

R

Q D

Northing: 967722.29 Easting: 1335083.49

B O

R

IN

G L

O G

/1

4/

:2

M

:\P R

O

JE

C T

S \B

LR

I\2

D

\T E

C H

S E

R V

\G E

O T

E C

H \S

U B

S U

R F

A C

E I

N V

E S

T

IG

A T

IO

N

\B O

R

IN

G L

O G

S \G

IN

T

B O

R

IN

G L

O G

S \N

P B

LR

I 2

D

, M P

G

IN

T B

O R

IN

G

L O

G S

-D R

A F

T .G

P J

2920.6 2920.1

2900.9

Sheet: 1 of 3

1.8

1.7

1.8

1.7

1.6

100.0

73.0

Poorly graded SAND with silt and gravel (SP-SM), very loose to dense, very loose to loose, brown, moist, non plastic. A-1-b and A-3. Slightly micaceous pH: 7.9 (30.0'-32.0' depth) pH: 8.2 (35.0'-37.0' depth) (Continued)

Silty SAND (SM), medium dense to very dense, gray, moist, non plastic. A-2-4(0)

GNEISS, dark gray, fine grained, slightly to highly weathered, very weak rock (R1). Discontinuities are closely to very closely spaced and in fair condition, joints and fractures range from 30° to 60° from horizontal.

Run No. 1: CR=100%, RQD=72% Run No. 2: CR=73%, RQD=38%

2-3-6-11

23-19-15-17

6-11-12-14

16-27-31-31

5-7-11-11

J-11

J-12

J-13

J-14

J-15

R-1

R-2

R-3

45.0

53.0

58.9

Project Location:

Encountered at:

After

Caved at:

Hammer Drop:

Rock Core (RQD in %)

(Blows / ft)

2920.9 ft

Undisturbed (UD)

5/15/19

Project Name:

MATERIAL DESCRIPTION

Boring No.:

Groundwater Depth:

Sample Types:

BORING LOG

5/21/19 J. Farley

D. HutchinsOperator:

T yp e

Weather:

SAMPLE

Plastic Limit

Boring was backfilled with auger cuttings and patch with cold mix asphalt.

Groundwater was not encountered during the drilling operation.

HSA was done in 5/15/2019. Rock Coring was done in 5/21/2019.

hrs

Remarks:

Auger Cuttings

G ra ph ic

L og

NP BLRI 2D17 - Replacement of Laurel Fork Bridge

Density, Color, Plasticity, Size, Proportions, Moisture

Surface Elevation:

Boring Location:

La ye r

D ep th ft)

Boring Began:

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

Liquid Limit

SPT

U. S. DEPARTMENT OF TRANSPORTATION

At Completion:

Completed:

S P

T B lo w s pe r in

D ep th S ca le ft)

N o.

Blue Ridge Parkway, MP 248, Ashe County, North Carolina

E le va tio n (f ee t)

3 3/4" Boring Method:

Rock Core Diam:

Vane Shear

30 in.

140 lbs/Automatic

Penetrometer (PP in tsf)

Water Content %

Hole Diameter:

NAD83

BH19-01

Hammer Wt. & Type:

Sunny, 45°F

BLRI MP 248

Standard Penetration Test Data

Project Datum:

Inspector:

R ec ft/

P P

R

Q D

Northing: 967722.29 Easting: 1335083.49

B O

R

IN

G L

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2875.9

2867.9

2862.0

Sheet: 2 of 3

100.0

53.0

53.0

78.0

82.0

44.0

GNEISS, dark gray, fine grained, moderately to highly weathered, very weak rock (R1). Discontinuities are closely to very closely spaced and in fair condition, joints and fractures range from 30° to 60° from horizontal.

Run No. 3: CR=100%, RQD=90% (Continued)

GNEISS, dark gray, fine grained, moderately to highly weathered, very weak rock (R1). Discontinuities are closely to extremely closely spaced and in fair condition, joints and fractures range from 30° to 70° from horizontal.

Run No. 4: CR=53%, RQD=13%

GNEISS, dark gray, fine grained, moderately to highly weathered, very weak rock (R1). Discontinuities are very closely to extremely closely spaced and in fair condition, joints and fractures range from 30° to 60° from horizontal.

Run No. 5: CR=53%, RQD=0%

GNEISS, dark gray, fine grained, moderately weathered, very weak rock (R1). Discontinuities are closely to very closely spaced and in fair condition, joints and fractures range from 30° to 60° from horizontal.

Run No. 6: CR=78%, RQD=39%

GNEISS, dark gray, fine grained, moderately weathered, very weak rock (R1). Discontinuities are closely to very closely spaced and in fair condition, joints and fractures range from 30° to 60° from horizontal.

Run No. 7: CR=82%, RQD=32%

GNEISS, dark gray, fine grained, moderately to highly weathered, very weak rock (R1). Discontinuities are closely to very closely spaced and in fair condition, joints and fractures range from 30° to 70° from horizontal.

Run No. 8: CR=44%, RQD=0%

Boring Terminated at 88.9 ft

R-3

R-4

R-5

R-6

R-7

R-8

63.9

68.9

73.9

78.9

83.9

88.9

Project Location:

Encountered at:

After

Caved at:

Hammer Drop:

Rock Core (RQD in %)

(Blows / ft)

2920.9 ft

Undisturbed (UD)

5/15/19

Project Name:

MATERIAL DESCRIPTION

Boring No.:

Groundwater Depth:

Sample Types:

BORING LOG

5/21/19 J. Farley

D. HutchinsOperator:

T yp e

Weather:

SAMPLE

Plastic Limit

Boring was backfilled with auger cuttings and patch with cold mix asphalt.

Groundwater was not encountered during the drilling operation.

HSA was done in 5/15/2019. Rock Coring was done in 5/21/2019.

hrs

Remarks:

Auger Cuttings

G ra ph ic

L og

NP BLRI 2D17 - Replacement of Laurel Fork Bridge

Density, Color, Plasticity, Size, Proportions, Moisture

Surface Elevation:

Boring Location:

La ye r

D ep th ft)

Boring Began:

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

Liquid Limit

SPT

U. S. DEPARTMENT OF TRANSPORTATION

At Completion:

Completed:

S P

T B lo w s pe r in

D ep th S ca le ft)

N o.

Blue Ridge Parkway, MP 248, Ashe County, North Carolina

E le va tio n (f ee t)

3 3/4" Boring Method:

Rock Core Diam:

Vane Shear

30 in.

140 lbs/Automatic

Penetrometer (PP in tsf)

Water Content %

Hole Diameter:

NAD83

BH19-01

Hammer Wt. & Type:

Sunny, 45°F

BLRI MP 248

Standard Penetration Test Data

Project Datum:

Inspector:

R ec ft/

P P

R

Q D

Northing: 967722.29 Easting: 1335083.49

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2857.0

2852.0

2847.0

2842.0

2837.0

2832.0

Sheet: 3 of 3

1.4

1.3

1.4

1.7

0.9

87.0

100.0

Silty SAND (SM), very loose, tan-brown, moist, non plastic. A-1-b. Slightly micaceous

Poorly graded SAND with silt and gravel (SP-SM), very loose, tan-brown, moist, non plastic. Slightly micaceous

Si…