Soil and Foundation Report - AR PFH 65-3(5).pdf

SOILS AND FOUNDATION

REPORT NO. 10-05

PROJECT AR PFH 65-3(5)

RECONSTRUCTION OF ARKANSAS FOREST HIGHWAY 65

OZARK NATIONAL FOREST

JOHNSON COUNTY, ARKANSAS

U.S. Department of Transportation Federal Highway Administration

Eastern Federal Lands Highway Division 21400 Ridgetop Circle

Sterling, VA 20166

July 2006

PROJECT AR PFH 65-3(5)

RECONSTRUCTION OF ARKANSAS FOREST HIGHWAY 65

OZARK NATIONAL FOREST

JOHNSON COUNTY, ARKANSAS

FEDERAL HIGHWAY ADMINISTRATION

Eastern Federal Lands Highway Division

Sterling, Virginia July 2006

TABLE OF CONTENTS

REPORT PAGE

INTRODUCTION

General Project Description Regional Geology

PROCEDURES AND RESULTS

Soil Borings Sampling Data Summary Laboratory Testing Findings

Roadway Borings Bridge Borings

DESIGN ANALYSIS AND CONCLUSIONS

Scour Data Bridge Foundations Retaining Walls Embankments

RECOMMENDATIONS

Bridge Foundations Retaining Walls Embankments

CONSTRUCTION CONSIDERATIONS

Bridge Foundations Retaining Walls Embankments Additional Considerations

DISCLAIMER/LIMITATIONS CLAUSE

APPENDICES

APPENDIX A - Figures APPENDIX B - Boring Location Plans APPENDIX C - Boring Logs APPENDIX D - Laboratory Data APPENDIX E - Bridge Analysis Data APPENDIX F - Retaining Wall Analysis Data APPENDIX G - Embankment Analysis Data APPENDIX H - Scour Analysis Data APPENDIX I - Typical Bridge Details APPENDIX J - Typical Retaining Wall Details

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

APPENDIX K - Special Contract Requirements

TABLE OF TABLES

REPORT PAGE

Table 1. Results of Laboratory Testing

Table 2. Results of Laboratory Testing on Core Samples

Table 3. Results of Scour Analyses

Table 4. Bridge Foundations

Table 5. Retaining Wall Location

Table 6. Design Stability Criteria

Table 7. Design Parameters for Retaining Wall Analysis

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

Table 8. Reinforced Foundation Areas

INTRODUCTION

General

This report presents the results of field and laboratory investigations, and presents geotechnical recommendations for reconstruction and repairs for Project AR PFH 65-3(5).

The project is located along Arkansas Forest Highway 65 in the Pleasant Hill Ranger District of the Ozark National Forest in Johnson County, Arkansas. The Arkansas State Highway Department (AHTD) authorized the Eastern Federal Lands Highway Division (EFLHD) of the Federal Highway Administration (FHWA), through a Memorandum of Agreement executed June 4, 1996 to perform this study in cooperation with the U.S. Forest Service. The general site location is shown on Figure 1, “Site Location and Vicinity Map,” in Appendix A.

Project Description

This project is the sixth and final in a series of projects located along Arkansas Forest Highway 65. The AHTD designed and constructed the first two projects; EFLHD designed and AHTD constructed the third project; and EFLHD designed and constructed the fourth and fifth projects. This phase of the reconstruction of Arkansas Forest Highway 65, consists of upgrading the existing gravel road to 3.0-meter paved travel lanes with 0.6-meter shoulders, mill and overlay of the paved portion of the road, construction of retaining walls, and replacing three bridges (Little Mulberry Creek Bridge, Bowen Creek Bridge, and Wolfpen Creek Bridge). Other work includes drainage improvements, curb and gutter, minor realignments, etc.

The Little Mulberry Creek Bridge design was completed under Project AR PFH 65-3(4) and so will not be discussed in this report. The design of the Little Mulberry Creek Bridge may be referenced in EFLHD’s Geotechnical Report Number 32-99.

Forest Highway 65 is generally located adjacent to bluffs and overlooks the Mulberry River, which has been designated a Recreational River in the National Wild and Scenic Rivers System. Because of this designation, preservation of the views from both the roadway and the river are a major concern to the U.S. Forest Service (FS). Consequently, retaining walls and curb and gutter sections will be used to minimize the construction limits in areas where the topography and location of the Mulberry River and bluffs govern.

DEPARTMENT OF TRANSPORTATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

STERLING, VIRGINIA

Regional Geology

The project site is located in a geologic region between the Boston Mountains and Arkansas River Valley Physiographic provinces; and is predominantly underlain by the Atoka Formation. The Atoka Formation is the surface rock of the Boston Mountains and dominates the exposures in the Arkansas River Valley and the frontal Ouachita Mountains. This unit is comprised of alternating layers of marine, mostly tan to gray silty sandstones and grayish-black shale. Refer to Figure 2 in Appendix A for a Geologic Map of the area.

According to the United States Department of Agricultures “Soil Survey of Johnson County, Arkansas, (1977)” several types of alluvium, and colluvium formations dominate the near surface geology within the project limits. These include the Nella-Enders-Mountainburg Association, the Linker-Mountainburg Association and the Pickwick-Spadra Association.

These soil associations typically consist of well-drained, nearly level to very steep, loamy and stony soils derived from the in-place chemical weathering of the sandstone and shale bedrock. The Nella-Enders-Mountainburg and Linker-Mountainburg Associations are generally present on hills, mountains and ridges. The Pickwick-Spadra Association is generally present on stream terraces. Refer to Figure 3 in Appendix A for a “Soil Survey Map” of the project area.

PROCEDURES AND RESULTS

Soil Borings

The EFLHD Subsurface Exploration Team conducted a subsurface investigation program at the project site between June 9 and June 23, 2004. The subsurface investigation program consisted of drilling a total of 31 borings within the project limits. Twenty-three(23) of the 31 borings were drilled within the roadway and at proposed retaining wall and bridge locations.

The remaining eight(8) borings were drilled at proposed bridge locations. All borings were advanced to depth with hollow-stem augers and NQ wireline core barrels using a CME 850 rotary, track-mounted drill rig. The location of each boring may be reference on “Plan and Profile” sheets in Appendix B.

Sampling

Sampling of material beneath the tip of hollow stem augers was performed in each boring, through the auger stem, as borings were advanced. The test borings were drilled to depths ranging from 1.5 to 12.0 meters below the existing ground surface. Soil samples were typically continuously recovered to a depth of 1.5 meters. Thereafter, samples were collected at 1.5-meter intervals to the boring termination depth or auger refusal. Soil samples were recovered with a 56-mm (O.D.) split-spoon sampler in accordance with AASHTO T200-87.

Representative portions of recovered samples were preserved in glass jars for laboratory testing. The sampling sequence and associated jar samples for each boring are presented on its appropriate Boring Log in Appendix C.

Rock coring was conducted, upon encountering auger refusal in select borings. Rock cores were retrieved using NQ wireline core barrels. A field description by color and texture was made for each recovered sample. 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. The sampling sequence and associated core samples for each core run are presented on its appropriate Boring Log in Appendix C.

Water levels, if present, were measured in the borings at the time and under the conditions stated on the boring logs. Fluctuations in the groundwater level due to seasonal and climatic effects should be expected.

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 the presence of various materials such as gravel, pebbles, organic matter, etc. They also contain interpretations by the exploration foreman of the conditions between samples 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.

Groundwater level readings were made in the boreholes at the times and under the conditions stated on the boring logs. However, fluctuations in the ground water level due to seasonal and climatic effects should be expected.

The Boring Logs in Appendix C of this report 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 construction of this report.

Laboratory Testing

At the conclusion of the fieldwork, laboratory testing was conducted on representative soil samples. Laboratory tests on the samples included gradation (AASHTO T-27), Atterberg limits (AASHTO T-89, T-90), moisture content (AASHTO T-265), classification (AASHTO T-317), and California Bearing Ratio (AASHTO 193-99). Additionally, five (5) unconfined compressive strength tests (ASTM D-2938) were performed on representative rock core samples from Borings RB-9, RB-20, S-1, and S-2. Unconfined compressive strength tests were ordered on samples recovered from Borings S-3 and S-4, but could not be completed due to weak jointing of thin bedding planes. As a mass, the rock appears to be strong and competent. Laboratory test results are summarized in Tables 1 and 2 below and presented in Appendix D.

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Table 1. Results of Laboratory Testing Sample Depth Fines

Water Content Boring Sample

(m) (%)

LL(2) PI(2)

Classification

RB-3 J-2 3.0 – 3.6 18.7 18 NP 8.8 A-2-4(0)

RB-4 J-2 1.5 – 2.1 38.5 20 NP 14.1 A-4(0)

RB-7 J-2 0.9 – 1.5 23.6 21 NP 7.9 A-1-b

RB-8 (3) Bag 0.3 – 1.5 24.4 23 NP N/A A-1-b

RB-8 J-3 3.0 – 3.6 82.7 39 16 17.6 A-6(13)

RB-10 J-1 0.3 – 0.9 9.1 20 NP 10.5 A-1-b RB-11 J-4 4.6 – 5.2 15.4 ND NP 29.9 A-1-b

RB-14 J-1 0.3 – 0.9 45.7 27 13 13.4 A-6(2)

RB-17 J-3 3.0 – 3.6 29.2 23 6 12.0 A-2-4(0)

RB-18 (4) Bag 0.3 – 1.5 23.2 18 NP N/A A-1-b

RB-21 J-3 2.4 – 3.0 45.6 ND NP 15.3 A-4(0)

RB-22 J-1 0 – 0.6 13.4 ND NP 12.8 A-1-a RB-23 J-2 1.5 – 2.1 12.9 ND NP 9.1 A-1-a

(1) N.D. = Not Determined (2) N.P. = Non-Plastic (3) CBR=58 @ 6.3% Moisture (4) CBR=54 @ 7.1% Moisture

Table 2. Results of Laboratory Testing on Core Samples

Boring No. Core Run No.

Sample Depth

(m) Rock Type

Unconfined Compressive Strength

(MPa) RB-9 2 4.4 – 4.6 Sandstone 21.3 RB-20 1 5.0 – 5.1 Shale/Sandstone 110.1 RB-20 3 6.3 – 6.7 Shale/Sandstone 65.0

S-1 1 6.1 – 6.4 Shale 29.4 S-2 3 3.1 – 3.3 Sandstone 29.8

Findings

Descriptions of the pavement and soil conditions encountered during the subsurface explorations conducted at the site are provided below. Generally, they are listed in order of increasing depth below the ground surface.

Roadway Borings (Borings RB-1 thru RB-2A)

PAVEMENT – Paved portions of the route generally consist of a 30 to 105-millimeter thickness of asphalt concrete underlain by a variable thickness of aggregate base

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ranging from 90-millimeter to 1.4 meters. Unpaved portions of the route consist of a 60-millimeter thickness of aggregate surfacing material.

SILT, SILTY SAND & SAND – The structural section of the roadway was generally underlain by a layer of brown silt, silty sand and sand [A-2-4(0), A-4(0), A-1-b]. This stratum ranged in thickness from 0.6 to 8.7 meters and contained trace amounts of fine gravel and trace amounts of clay in select borings. Standard penetration tests values (N-values) recorded within this stratum ranged from 2 to greater than 30 blows per 300-millimeter increment, indicating very loose to very dense conditions.

CLAY – A layer of red to red-brown clay with trace amounts of sand and fine gravel [A-6(2), (13)] was encountered in several borings. This stratum was generally encountered below the silt, silty sand, and sand stratum described above, and ranged in thickness between 0.2 and 4.9 meters. The relative depth at which the clay layer was encountered ranged from the ground surface to a depth of 5.9 meters. N-values recorded in this stratum ranged from 4 to greater than 50 blows per 300-millimeter increment, indicative of soft to hard consistencies.

WEATHERED ROCK – Weathered rock consisting of mottled brown to yellow-brown, decomposed to slightly weathered sandstone and shale [A-1-a] was encountered in select borings underlying the above listed strata. This stratum ranged in thickness from 1.5 to 10.6 meters. N-values recorded within the weathered rock ranged from 30 to greater than 50 blows per 300-millimeter increment, indicating medium dense to very dense conditions. Borings were generally terminated within this stratum or it was penetrated until auger refusal was encountered.

BEDROCK – Underlying the natural soil and/or weathered rock strata, bedrock was encountered. The bedrock is comprised of gray to brown, moderately weathered to unweathered, jointed to sound interbedded sandstone and shale. Bedrock was encountered in three(3) of the 23 roadway borings (RB-7, 8, and 20) at depths ranging from 2.9 to 10.8 meters below ground surface. Rock core recoveries ranged from 93 to 100 percent, and rock quality designations (RQD) values ranged from 47 to 100 percent, an indication of fair to excellent rock quality. Borings were typically terminated within this stratum. Unconfined compressive strength testing was performed on select samples of bedrock and indicated strengths ranging between 21.3 and 110.1 Megapascals (MPa). The results of strength tests are presented in Table 2 above and on laboratory data sheets in Appendix D.

Large diameter sandstone and shale boulders were encountered in six(6) of the 23 roadway borings (RB-7, 10, 18, 19, 22, and 23) at depths ranging between ground surface and 9.5 meters bgs.

Groundwater was measured in three(3) of the 23 roadway borings (RB-3, 11 and 13).

The groundwater level, where observed, varied between 4.6 and 6.1 meters bgs.

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Bridge Borings (Borings S-1 thru S-4A)

Wolfpen Creek Bridge A total of four boreholes (S-1, S-1A, S-2 and S-2A) were drilled at the proposed Bowen Creek Bridge site; located between Sta. 15+245 and Sta. 15+257. Fill, consisting of sand, gravel and boulders was encountered at ground surface in all borings and ranged in thickness from 1.7 to 3.0 meters.

Relatively sound to sound shale bedrock was encountered underlying the fill strata in borings S-1 and S-2, at depths ranging from 1.7 to 3.0 meters bgs, corresponding to EL. 287.1 to 285.5. Rock core recoveries ranged from 95 to 100 percent, and RQD values ranged from 88 to 100 percent, indicating good to excellent rock quality.

Unconfined compressive strength testing was performed on select samples of bedrock and yielded and average strength of 29.6 Megapascals (MPa).

Two probe holes (S-1A and S-2A) were also drilled at this location to confirm the findings of Borings S-1 and S-2. A field description by color and texture was made for the auger cuttings and observed changes in the performance of the drill rig were recorded on boring logs. The two probeholes were terminated at relatively shallow depths upon encountering auger refusal on bedrock at depths varying between 4.2 and 5.9 meters bgs, corresponding to EL. 287.1 and 283.5.

Bowen Creek Bridge A total of four boreholes (S-3, S-3A, S-4 and S-4A) were drilled at the proposed Wolfpen Hollow Bridge site; located between Sta. 16+147 and Sta. 14+169. Fill, consisting of sand, gravel and boulders was encountered at ground surface in all borings and ranged in thickness from 2.3 to 4.0 meters.

Jointed to sound, interbedded shale and sandstone bedrock was encountered beneath the fill strata in borings S-3 and S-4. Rock core recoveries ranged from 48 to 100 percent, and RQD values ranged from 30 to 100 percent an indication of highly jointed to sound rock. Excellent quality rock was generally encountered at an average depth of 3.0 meters bgs, corresponding approximately to EL. 291.5.

Two probe holes (S-3A and S-4A) were also drilled at this location to confirm the findings of Borings S-1 and S-2. The two probeholes were terminated upon encountering auger refusal on bedrock at an average depth of 2.2 meters bgs, corresponding approximately to EL. 292.

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DESIGN ANALYSIS AND CONCLUSIONS

Scour Data

EFLHD’s Hydraulics Section performed scour analyses for both a 100-year and a 500-year storm event. A long-term channel degradation of 300-millimeters was used in the design analysis. Depths and resultant elevations for long-term channel degradation, contractive and local scour are shown below in Table 3.

Table 3. Results of Scour Analyses East Abutment West Abutment Recurrence

Intervals Scour Depth

Scour Elevation

Scour Depth

Scour Elevation Bridge

(yrs) (m) (m) (m) (m) 100 1.31 288.37 3.33 285.99 Wolfpen

Hollow 500 2.66 287.02 5.46 283.86 100 4.41 290.35 2.72 292.04 Bowen

Creek 500 6.46 288.3 4.63 290.13

The calculated scour depths are based on the assumption that the streambed material is silt;

however, the actual streambed materials at the two bridge sites consist of fill and natural soil, consisting of sand, gravel and boulders, underlain by interbedded sandstone and shale bedrock. We recommend that bridge foundations be designed to bear on competent rock at elevations shown below in Table 4.

Bridge Foundations

The foundation design analyses consisted of analyzing a foundation system comprised of spread footings bearing on competent rock, where for purposes of our analyses, competent rock is defined as weathered to sound bedrock. Based on the results of our subsurface field investigation program, competent bedrock is generally located at depths ranging between 0.5 and 1.2 meters below the planned footing bearing grades. Consequently, our design analyses were performed to account for the likelihood of footings bearing on seal concrete fill. The seal concrete would be placed at locations where the elevation of competent bedrock fell below the planned bottom of footing elevation. Analysis procedures and results are expounded as follows.

Allowable bearing capacity calculations were performed in accordance with procedures set forth in “AASHTO, Standard Specification for Highway Bridges, 16th Edition, (1996), Subsection 4.4.8.1.1.” Ultimate bearing capacity calculations were performed assuming that bridge foundations will consist of spread footings bearing directly on bedrock. A minimum RQD value of 30 percent was encountered within a depth of 0.5B (where B is the width of the footing) below the base of bridge footings and so was used in our analysis.

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Table 4. Bridge Foundations

Structure Location

Design Scour Elev.

(m)

Top of Rock

Elevation (m)

Bottom of Footing

Elevation (m)

Anticipated Foundation

Bearing Material

Allowable Bearing Capacity

(MPa) East

Abutment 286.3 287.1 287.3 Seal concrete Wolfpen Creek Bridge West

Abutment 287.6 285.5 287.1 Seal concrete

North Abutment 293.4 292.0 293.2 Seal concrete Bowen

Creek Bridge South

Abutment 292.4 292.0 292.5 Seal concrete

3.5

Settlement analyses were not performed for the individual bridges. According to AASHTO (1996), elastic settlement for footings bearing on competent rock will generally be less than 13 millimeters. Bridge foundation design calculations may be referenced in Appendix E.

Retaining Walls

In an effort to increase the width of the existing roadway, while minimizing construction limits and maintaining views along the Mulberry River, it is proposed to construct approximately 1.13 km of retaining walls along the roadway alignment. Retaining walls of varying height are to be constructed along the following locations:

Table 5. Retaining Wall Location Roadway Station (m)

Start End Length (m)

8+905 8+925 20 10+620 10+670 50 10+740 11+980 240 14+120 14+220 100 14+340 14+380 40 14+480 15+160 680

Three alternative retaining wall configurations were analyzed for use. The three alternatives, listed below, were evaluated on the basis of cost, constructability, construction quality control and aesthetics.

1. Stone-filled Cellular Confinement System (CCS) with stacked rock facing and concrete filled CCS foundation.

2. Geogrid-reinforced Earth Wall with Gabion wire basket facing and concrete filled CCS foundation.

3. Geogrid-reinforced Earth Wall with stacked rock facing and concrete filled

CCS foundation.

The geogrid-reinforced earth wall with stacked rock facing and concrete-filled CCS foundation (Alternative No. 3) was ultimately selected on the basis of constructability, cost-effectiveness and aesthetics.

Stability Analyses

Design of the geogrid-reinforced earth wall with stacked rock facing was conducted in general accordance with the design procedures presented in FHWA Publication No, FHWA- SA-96-071, “Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction,” (1999). The height of retaining walls varies along the alignment to a maximum height of 3.0 meters, with a wall face batter of 1H:6V. Design analyses were performed for the most critical section of the roadway and the maximum wall height.

Additionally, the wall was analyzed for with a uniform surcharge load of 12.0 kPa at the crest of the slope and along the full width of the roadway. Effective stress conditions were analyzed as they represent the critical case for stability at this site.

The wall was analyzed to satisfy the following failure criteria:

Table 6. Design Stability Criteria Failure Mode Min. FS Overturning 2.0

Sliding 1.5 Global Stability 1.3

Bearing Capacity 3.0

The soil properties presented in Table 7 below were used in the design analyses. These soil strength parameters were established based on empirical correlations to field and laboratory test data.

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Table 7. Design Parameters for Retaining Wall Analysis

Material Type Unit Weight, �

(KN/m3) Friction Angle, �

(deg.)

Cohesion, c

(kPa) Reinforced Fill 19.6 32 - Gravel Drain 21.4 34 - Stacked Rock 18.9 40 -

Concrete Footing 22.6 40 143.6 Type I 13.8 28 12 Foundation

Soil Type II 15.7 32 7.2

Stability of the retaining wall was checked using the computer programs ReSSA(2.0) and SlopeW(5.0). The results of design analyses indicated that the proposed wall configuration satisfies all stability requirements.

Bearing Capacity Analyses

Subsurface field investigations encountered loose, granular materials or soft to stiff fine-grained soils at several locations along the proposed retaining walls. These soft soils, were generally encountered at the approximate toe of the proposed retaining walls. Bearing capacity analyses were performed to determine the capacity of foundation soils to support the proposed retaining wall at these locations. Bearing Capacity analyses were performed in accordance with principles established in NCHRP 24-4, “Engineering Manual for Shallow Foundations,” (1991). A minimum bearing capacity factor of safety of 3.0 was used in the analyses.

The results of design analyses indicated that foundation soils at select locations do not satisfy bearing capacity requirements. Based on design analysis results we recommended that retaining walls, at the locations listed in Table 8 below, be constructed to bear on a Geosynthetic Reinforced Soil (GRS) foundation. The primary function of the GRS foundation is to transfer the wall loads over a wider area, whereby reducing the applied load on subgrade soils.

Table 8. Reinforced Foundation Areas Station (m)

Start End Length of Repair

(m) 11+905 11+915 14+120 14+130 14+692 14+702

Refer to Appendix F for examples of retaining wall design calculations.

Embankments

Fill embankments varying in height from 0.5 to 4.0 meters are proposed for construction along sections of the roadway. Embankment fill material is to be placed at the locations listed below in Table 9.

Table 9. Location of Embankments Station (m)

Start End Length

(m) Max Height

(m) 9+380 9+840 460 4.0 12+00 12+740 740 2.0

Generally, loose to medium dense silty sand and sand, and soft to medium stiff clay was encountered along the proposed embankment footprints.

Settlement analyses were conducted for embankments overlying the clay material encountered in boring RB-4 (Sta. 9+760) and for an embankment with a maximum height of

1.75 meters and 3H:1V side slopes. The magnitude of primary settlement and time-rate of settlement computations were performed using the computer program FoSSA(2.0) and were checked with hand computations performed in accordance with Terzaghi’s theory of consolidation. The settlement computations indicate that the approximate 3.0-meter thick clay layer will experience a total settlement of approximately 40 millimeters under the proposed embankment loading. However, time-rate of settlement calculations indicate that the majority of settlement will take place during embankment construction and shortly after fill placement. It is expected that the majority of settlement for embankments overlying silty sand and sand material will take place during and immediately following embankment construction.

The stability of embankments constructed over loose/soft soil was evaluated using the computer program SlopeW(5.0). A generalized subsurface profile developed in accordance with the findings of boring RB-3 (Sta. 9+495) was used to analyze a 4.0-meter high slope with 2H:1V side slopes. A minimum factor of safety of 1.6 was computed for the proposed embankment. The computed factor of safety exceeds the minimum required factor of safety of 1.3.

Refer to Appendix G for examples of embankment design analyses.

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RECOMMENDATIONS

Bridge Foundations

Based on the results of our analyses, it is recommended that the proposed bridges be supported on reinforced concrete spread footings bearing directly on competent bedrock or tremie seal concrete. Design footings for a maximum allowable bearing capacity of 3.5 MPa.

Design footings with maximum bottom of footing elevations as listed in Table 4.

Where seal concrete is required beneath foundations, it should be placed beneath the footings down to the scour elevations or top of competent rock, whichever is lower, and within a zone extending a minimum of 300 millimeters laterally beyond the edge of footings. Place seal concrete by using a tremie tube to introduce the concrete at the bottom of the excavations.

Retaining Walls

Based on stability analysis results we recommend that retaining walls along the alignment be comprised of a composite wall system consisting of a geogrid reinforced earth wall with a stacked rock facing. The stacked rock facing section of the wall is to bear on a concrete footing. For added stability of the stacked rock facing, we recommend that the bottom course of stacked rocks be doweled into the underlying concrete footing. Dowels are to consist of No. 4 (130 millimeters diameter) rebar spaced a maximum of 500 millimeters on-center.

Install dowels in accordance with Section 502 of the AHTD Specifications.

Based on bearing capacity analysis results we recommended that retaining walls, at the locations listed in Table 8, be constructed to bear on a Geosynthetic Reinforced Soil (GRS) foundation. The GRS foundation is to consist of alternating layers of Type 10 geotextile conforming to Section 625 of the AHTD Specifications, and structural backfill extending to a minimum depth of 1.5 meters. Reinforcement layers are to be embedded a minimum depth of

3.0 meters and placed at a maximum vertical spacing of 500 millimeters. The required long-term design strength (allowable tensile strength) of the geosynthetic reinforcement is to be a minimum of 100 kN/m.

The CO shall make determinations of the need for the concrete footing and/or GRS foundation improvement below retaining walls less than 1.0-meter high. This determination is to be made in accordance with Geotechnical foundation recommendations, applicable soil boring logs, and consultation with EFLHD's Geotechnical Section.

Refer to Sheet Nos. K1 thru K2 of Appendix J for typical retaining wall details.

Embankments

Settlement analyses indicate proposed embankments will undergo maximum settlements of 40 millimeters. The majority of settlement is anticipated to take place during embankment

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construction. Stability analyses indicate that the proposed embankments satisfy all stability requirements.

CONSTRUCTION CONSIDERATIONS

Bridge Foundations

Excavation and Sub-Excavation for Footings: Foundation preparation should be performed in accordance with Subsection 801.04 of the AHTD Specifications. Sub-excavation of loose boulders and rock may be required below neat line at the bottom of the proposed footing elevations. Bedrock and boulders should be excavated with appropriate equipment to achieve a neat line. Appropriate equipment for breaking rocks and boulders should be on-site during structural excavation. Any unsuitable materials below proposed footing elevations should be removed. Sub-excavated areas should be filled with seal concrete backfill as per Section 206 of the AHTD Specifications.

Excavation Protection: Temporary construction excavations above the water table and not exceeding 1.5 meters in depth may be constructed with a ½H:1V side slopes in fill material.

Localized instabilities in such excavations may occur due to heterogeneity of the near surface soils. In such areas, the excavation sides should be flattened to a stable slope. The side slopes should be protected from excessive disturbance due to surface water runoff. In addition, regardless of the above recommendations, all excavations should be performed in accordance with local, state and federal regulations, including current OSHA excavation safety standards.

Structural Backfill: The granular portions of on-site soils may be used as a backfill material behind the proposed abutments and wingwalls; however, due to presence of large boulders in structural excavation, on-site soils may not be suitable to achieve backfilling requirements.

Sufficient quantity of imported structural fill soils may be required for all three bridges.

Excavated large boulders should be used to backfill in front of proposed footings and wingwalls below the existing channel elevation to prevent erosion. The backfill material behind walls should be in accordance with Section 801 of the AHTD Specifications.

Backfill Drainage: Weepholes with 6-inch diameter through abutment walls and wingwalls should be installed at a maximum spacing of 10 feet. Weepholes should be installed sufficiently above normal water flow elevation of the Mulberry River at each bridge based on hydraulic analysis to prevent river water intrusion into backfill. All weepholes should be approved non-perforated PVC pipes as per Section 611 of the AHTD Specifications.

Approved geocomposite drains as per Section 625 of the AHTD Specifications should be placed against the back face of all walls. The geocomposite drains should extend from the top of the footings to the bottom of the proposed aggregate base course at approaches.

Retaining Walls

Excavation and Sub-Excavation: Foundation preparation should be done in accordance with Subsection 801.04 of the AHTD Specifications. Temporary excavation in the fill and natural material should be achievable using conventional heavy earth-moving equipment in proper

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working condition. Excavation will be required for retaining wall construction and removal of unsuitable and unstable soils encountered within the limits of proposed retaining wall construction

The excavation subgrade will likely consist of fine-grained soils. Depending on moisture conditions during construction activities, these soils may provide only a marginal travel surface for heavy equipment. During excavation, care should be taken not to disturb the exposed soils at the excavation subgrade level. In addition, the exposed subgrade soils should be examined for presence of loose/soft or otherwise unsuitable soils. If unsuitable soils are encountered, they should be removed and replaced as discussed below.

Sub-excavation of loose and/or soft soils and boulders may be required below neat line at the bottom of the proposed footing elevations. Any soft/loose zones observed should be over-excavated no deeper than 600 millimeters and replaced with suitable material. Prior to placement of backfill, place a layer of Type 10 geotextile conforming to Section 625 of the AHTD Specifications at the bottom of the excavation.

Reinforced Foundation Areas: The results of design analyses indicated that foundation soils at select locations do not satisfy bearing capacity requirements. Consequently, it is recommended that the foundation of the retaining walls be stabilized by constructing a GRS foundation. The GRS foundation is to consist of alternating layers of Type 10 geotextile conforming to Section 625of the AHTD and structural backfill extending to a minimum depth of 1.0 to 1.5 meters. Structural backfill is to conform to Section 801 of the AHTD Specifications.

Reinforcement layers are to be embedded a minimum depth of 3.0 meters and placed at a maximum vertical spacing of 500 millimeters. The required long-term design strength (allowable tensile strength) of the geosynthetic reinforcement is to be a minimum of 100 kN/m.

The CO shall make determinations of the need for the concrete footing and/or GRS foundation improvement below retaining walls less than 1.0-meter high. This determination is to be made in accordance with Geotechnical foundation recommendations, applicable soil boring logs, and consultation with EFLHD's Geotechnical Section.

Concrete footing: The stacked rock facing section of proposed retaining walls is to be constructed on a welded wire fabric reinforced concrete footing. Construct the concrete footing in accordance with Section 502 of the AHTD Specifications.

Detail drawings of the proposed retaining wall system and the reinforced fill are provided in Appendix J.

FEDERAL HIGHWAY ADMINISTRATION

Embankments

Sub-Base Construction: All existing AC pavement within the proposed limits of new pavement should be removed. The existing AC pavement and gravel roadway below the proposed limits of pavement should be scarified or pulverized as per Section 214 and should be recompacted as per Section 212 of the AHTD Specifications. Imported fill material for embankments should be in accordance with Section 210, and compacted as per Subsection

210.11 of the AHTD Specification. Unsuitable materials within proposed roadways should be sub-excavated. Leaving the existing fill in place does entail some risk of pavement settlement, especially if stumps or other organic matter was buried at the site; however, such conditions were not discovered in explorations.

Prior to placing any fill or base material within pavement areas, the exposed fill or natural soil subgrade should be confirmed to be firm and stable in accordance with Sections 212 and 214 of the AHTD Specifications.

The CO shall make determinations of the need and/or extent of sub-excavation to a maximum depth of 600 millimeters, in accordance with Geotechnical foundation recommendations, applicable soil boring logs, and consultation with EFLHD’s Geotechnical Engineering Section.

Additional Considerations

Temporary Sheeting and Shoring: Utilization of temporary sheeting and shoring is anticipated for structural excavation. Temporary sheeting and shoring supporting the existing structures, new structures and traveling roadway embankments should have a minimal lateral deflection to prevent damages on supporting structures and embankments.

Ground and Surface Water Management: Cofferdams, designed and constructed in accordance with Section 801 of the AHTD Specification, should be employed at all structural excavation and removal locations to keep water from the river out of the working areas and to keep construction debris out of the river. All footings will be founded near or below the observed ground water level. Excavations for footings will encounter groundwater seepage;

and, temporary dewatering techniques, such as sumps and pumps will be required to maintain dry conditions during construction. Seal concrete backfill (where required) at the base of excavation will fill voids between boulders and crevices in the bedrock, limit water infiltration, provide working platform, and add lateral support to the temporary sheeting system where applied.

Groundwater levels are sufficiently below the deepest planned roadway excavation that significant groundwater inflow is not anticipated, and construction in the dry should be possible. However, the possibility of seasonal perched water inflow, as well as the need to remove accumulated surface water inflow and rainwater water may make some dewatering necessary.

All dewatering must be conducted in a manner that avoids undermining foundation subgrades and which limits the pumping of fines.

FEDERAL HIGHWAY ADMINISTRATION

APPENDIX A

Figures

Geologic Map of Arkansas, 1976 United States Geological Survey

The Atoka Formation is comprised of alternating layers of marine, mostly tan to gray silty sandstones and grayish-black shale.

STERLING, VIRGINIA

STATEREG

AR PFH 65-3(5)AR

FIGURE 2

GEOLOGIC MAP

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL LANDS HIGHWAY DIVISION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

SHEET

NO.PROJECT

ARKANSAS VALLEY AND OUACHITA MOUNTAINS REGIONS

Source:

TOTAL

SHEETS

Project: AR PFH 65-3(5)

Soil Survey, Johnson County, Arkansas, 1977 United States Department Agriculture

SHEET

NO.PROJECT

Source:

TOTAL

SHEETS

3STERLING, VIRGINIA

STATEREG

AR PFH 65-3(5)AR

FIGURE 3

GEOLOGIC MAP

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL LANDS HIGHWAY DIVISION

Project: AR PFH 65-3(5)

APPENDIX B

Boring Location Plan and Subsurface Profile

FEDERAL HIGHWAY ADMINISTRATION

APPENDIX C

Boring Logs

FEDERAL HIGHWAY ADMINISTRATION

M:\Projects\fs\nc\981(1)\techserv\geotech\Report\Appendix\Boring Log_Soil Description Standard.doc

SOIL BORING GENERAL NOTES

Drilling and Sampling Symbols

SS: Split Spoon - 1 3/8” I.D., 2” O.D., except where noted ST: Shelby Tube - 2” O.D., except where noted PA: Power Auger Sample

Water levels indicated on the boring logs are the levels measured in the boring at the times indicated. In pervious soils, the indicated elevations are considered reliable ground water levels. In impervious soils, the accurate determination of ground water elevations is not possible, even after several days, and additional evidence on ground water elevations must be sought.

VISUAL METHODS FOR SOILS CLASSIFICATION

Component Distinguishing Features

Boulders Larger than 12” (300 mm)

Cobbles 3” to 12” (75 mm to 12 mm)

Gravel Larger than No. 4 sieve and smaller than a 3” sieve, described with any of the following terms (or any combination):

Coarse 3” to 3/4” (75 mm to 19 mm) sieve Medium 3/4” to 3/8” (19 mm to 9.5 mm) sieve Fine 3/8” to No. 4 (9.5 mm to 4.75 mm) sieve

Sand The finest sand grains are just visible to the naked eye, while the largest would pass a No. 4 (4.75mm) sieve (pinhead size). Described with any of the following terms (or any combination):

Coarse No. 4 to No. 10 (4.75 mm to 2.0 mm) sieve Medium No. 10 to No. 40 (2.0 mm to 0.42 mm) sieve Fine No. 40 to No. 200 (0.42 mm to 0.075 mm) sieve

Silt 1. Lumps are easily crumbled when are-dried.

2. Feels gritty between the teeth.

3. A moist pat when shaken in the palm of the hand will appear shiny and wet. When squeezed it will appear dry and dull.

Clay 1. Lumps are comparatively hard when air-dried.

2. Threads (1/8” diameter) of considerable length will support their own weight when held by one end.

3. A moist pat will appear the same whether shaken in the palm of the hand or squeezed.

Order of Description

1. Soil Density (or consistency) – see table below

2. Color

3. Major Grain Size – Composes more than 50% of the sample

4. Modifying Term – “and” : 40% to 50% of the minor grain size

“some” : 30% to 40% “little” : 10% to 30%

“trace” : 10% or less

5. Minor Grain Size(s)

6. Other (plasticity, etc.)

M:\Projects\fs\nc\981(1)\techserv\geotech\Report\Appendix\Boring Log_Soil Description Standard.doc

7. Moisture Content (by field test) – “dry” : Absence of moisture, dusty, dry to the touch “moist” : Damp but no visible water

“wet” : Visible free water, usually soil is below water table

8. General Classification – Fill, Residual Soil, Weathered Rock

SOIL DENSITY (OR CONSISTENCY) TABLE

Coarse-Grained Soil (Gravel, Sand) Fine-Grained Soil (Clay, Silt)

Apparent Density SPT (# blows / ft) Consistency SPT (# blows / ft) Very loose 0-4 Very soft 0-2

Loose 5-10 Soft 3-4 Medium dense 11-30 Medium stiff 5-8

Dense 31-50 Stiff 9-15 Very dense >50 Very stiff 16-30

Hard >30

Examples:

1. Loose, brown to light brown SILT and SAND, trace clay (moist)

-FILL-

Criteria for Describing Soil Structure

Description Criteria

Bed A sedimentary layer bounded by depositional surfaces.

Blocky A characteristic in which cohesive soil can be broken down into small angular lumps which resist further breakdown.

Bonded Attached or adhering.

Fissured Broken along definite planes of fracture.

Foliated Planar arrangement of textural or structural features.

Frequent More than one per foot of thickness.

Homogeneous Same color and appearance throughout.

Interbedded Alternating soil layers of different composition.

Laminae A very thin cohesive layer.

Layer A general term for material lying essentially parallel to the surfaces against which it was formed.

Lens A lenticular deposit, larger than a pocket.

Occasional One or less per foot of thickness.

Parting A very thin granular layer.

Pocket Small erratic deposits less than 12” in thickness.

Seam A thin layer separating two distinctive layers of different composition or greater magnitude.

Stratified Alternating layers of varying material or color.

Stratum A stratigraphic unit.

Varve A cyclic sedimentary couplet consisting of a coarser and a finer layer representing the variation in depositional energy resulting from the annual freeze-thaw cycle typically found in glaciolacustrine environments.

H:\SOILS\Anderson\Misc. Project Material\Coring Log_Rock Core Description Standard.doc

ROCK CORING GENERAL NOTES

Depth and Elevation: Use large marks as 1’ (300mm) increments. Record proper elevations.

Core: Draw sketch of core breaks as it is oriented in the core box (align all core breaks so they fit together properly before drawing sketch). Starting at the top of core measure each piece of core down its centerline to 1/100 of a foot. Record this measurement along the left side of the core sketch at the break.

VISUAL METHODS FOR ROCK IDENTIFICATION

Description: 1. Draw a heavy line through description at depth to which core run penetrated.

2. Describe the rock type.

3. Note the condition of the core break on the right side of the core sketch

Mud seam (MS); Sand seam (SS); Weathered surface (WS); Fresh break (FB)

4. Record coring time in minutes.

5. Record to nearest 1/100 foot the core recovered (after alignment in core box). Discard any debris at top of core, which obviously fill into the core hole.

6. Calculate per cent core recovery and record: CR = feet of core recovered feet cored

Color: Wet the rock with water and describe the color including the color of any unusual or reoccurring markings on the core (i.e. light green with dark green bands, foliation lines).

Foliation: Foliation planes are parallel planes of different minerals forming a banded appearance on the rock.

The foliation planes are usually of a different color than the surrounding rock. Also the rock shears along the foliation planes if struck with a hammer. Record the following:

Close spaced (CS) – 1/8” (3mm) or closer; Medium spaced (MS) – 1/8” to 1/4” (3mm to 6mm);

Open spaced (OS) – 1/4” (6mm) or larger

The angle to the horizontal should be measured (with a protractor) and recorded for the rock core.

(Several different angles can be found in each 5’ to 10’ core.)

Hardness: Very Soft (VS) – Can be deformed or crumbled by hand; Soft (S) – Can be scratched with a fingernail Moderately Hard (MH) – Can be scratched easily with a knife; Hard (H) – Can be scratched with difficulty with a knife; Very hard (VH) – Cannot be scratched with a knife

Weathering: Use the proper number 1 through 5.

1. Unweathered: No evidence of any mechanical or chemical alteration along discoloration evidenced.

2. Slightly weathered: Discoloration is evident, on surface, slight alteration no discontinuities, less than 10% of the volume is altered, strength is substantially unaffected.

3. Moderately weathered: Discoloring is evident, surface is pitted and altered with alteration penetrating will below rock surfaces, weathering "halos” evident, 10% to 50% of the rock is altered, strength is noticeably less than fresh rock.

4. Highly weathered: Entire mass is discolored; alteration pervades nearly all of the rock with some pockets of slightly weathered rock noticeable, some minerals leached away, retains only a fraction of original strength (with wet strength usually lower than dry strength).

5. Decomposed: Rock is reduced to a soil with relict rock structure (saprolite), can be generally molded and crumbled by hand.

Rock Quality Designation (RQD) = �[Lengths of all pieces of the core � 4” (100mm)] x 100 Total length of core run

H:\SOILS\Anderson\Misc. Project Material\Coring Log_Rock Core Description Standard.doc

Soundness: Use the proper number 1 through 5

1. Weathered RQD = 0% to 25%

2. Highly jointed to Jointed RQD = 25% to 50%

3. Jointed to Relatively sound RQD = 50% to 75%

4. Relatively sound to Sound RQD = 75% to 100%

Rock Quality: Use the proper number 1 through 5

1. Very Poor RQD = 0% to 25%

2. Poor RQD = 25% to 50%

3. Fair RQD = 50% to 75%

4. Good RQD = 75% to 90%

5. Excellent RQD = 90% to 100%

Order of Description

1. Hardness

2. Color

3. Soundness (a.k.a. Weathering and Rock Quality)

4. Main Rock Formation – Composes more than 50% of the core run

5. Texture – Very Fine (VF), Fine (F), Medium (M), and Coarse (C)

6. Modifying Term – “and” : 40% to 50% of the core run “some” : 30% to 40% “little” : 10% to 30%

“trace” : 10% or less

7. Minor Rock Type(s)

8. Other (Foliation angle, etc.)

Examples:

1. Moderately hard, blue-gray to gray, weathered BIOTITE GNEISS BOULDER, medium texture

Recovery = 24%

RQD = 17%

2. Very hard, gray and white, relatively sound to sound BIOTITE GNEISS, medium to fine texture, some quartz veins, foliation angle = 20 degrees

Recovery = 100%

RQD = 100%

-Fresh break @ approximately 47’

U. S. DEPARTMENT OF TRANSPORTATION

Sheet: 1 of 1

Station 09+040

Plastic Limit

63.5 kg/Auto 203 mm

G ra ph ic

Lo g

Remarks:

Water Content %

B O

R

IN

G L

O G

5-

3( 5)

.G P

J F

H W

A _V

A .G

D T

/2

6/

3-3-10-50

76.2 cm

Project Location:

After

Caved at:

297.48 m

Borehole Termination Depth 1.5 m

J-1

Medium dense, brown SILT, trace of fine sand and clay (Dry)

GRAVEL

0.42672

1.5

0.1

HSA

E le va tio n (m et er s)

Project Name:

Light Rain R.Kingsley/W.Hughes

K.Thornton

(Blows / 0.3m)

N/A

6/9/04

6040B lo w s pe r m m hrs

6/9/04

Standard Penetration Test Data Liquid Limit

MATERIAL DESCRIPTION

Penetrometer Rock Core

Weather:

Encountered at:

Sample Types:

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

SPT

AR PFH 65-3(5)

UDAuger Cuttings

Ozark National Forest, Johnson County, Arkansas

RB-1

SAMPLE

R ec

Inspector:

Operator:

Hammer Wt. & Type:

BORING LOG

N o.

Surface Elevation:Groundwater Depth:

At Completion:

Hammer Drop:

D ep th S ca le

(m

La ye r D ep th

(m

1. No groundwater was encountered during or after drilling.

Vane Shear

Boring No.:

Boring Location:

Ty peDensity, Color, Plasticity, Size, Proportions, Moisture

Boring Began:

Rock Core Diam:

Boring Method:

Hole Diameter:

Completed:

297.4

296.0

E le va tio n (m et er s)

G ra ph ic

Lo g

Remarks:

Water Content %

Project Name:

Light Rain R.Kingsley/W.Hughes

K.Thornton 6/9/04

N/A

HSA

63.5 kg/Auto

Project Location:

After

B O

R

IN

G L

O G

5-

3( 5)

.G P

J F

H W

A _V

A .G

D T

/2

6/

9-18-20-20

203 mm

76.2 cm

Sheet: 1 of 1

Station 09+300

Plastic Limit

276.48 m

0.48768

Borehole Termination Depth 2.8 m

Very dense, brown to tan, highly weathered SHALE (Dry)

Dense, brown to tan, highly weathered SHALE (Dry)

GRAVEL

(Dry)

6/9/04

0.57912

2.8

0.9

0.1

6-34-50

5-16-44-44

0.36576

B lo w s pe r m m hrs

(Blows / 0.3m)

J-3

J-2

J-1

Sample Types:

Liquid Limit

MATERIAL DESCRIPTION

Penetrometer Rock CoreSPT

Boring No.:

Encountered at: Caved at:

UDAuger Cuttings

Standard Penetration Test Data

AR PFH 65-3(5)

SAMPLE

R ec

Inspector:

Operator:

Weather:

RB-2

Ozark National Forest, Johnson County, Arkansas

Groundwater Depth:

At Completion:

FEDERAL HIGHWAY ADMINISTRATION

EASTERN FEDERAL LANDS HIGHWAY DIVISION

BORING LOG

Boring Location:

1. No groundwater was encountered during or after drilling.

N o.

Surface Elevation:

Hammer Wt. & Type:

Hammer Drop:

D ep th S ca le

(m

La ye r D ep th

(m

Boring Began: Completed:

Ty peDensity, Color, Plasticity, Size, Proportions, Moisture

Vane Shear

Rock Core Diam:

Boring Method:

U. S. DEPARTMENT OF TRANSPORTATION

Hole Diameter:

275.6 1

276.4

273.7

N/A le va tio n (m et er s)

Project Name:

Clear R.Kingsley/W.Hughes

After

6/9/04

HSA

6/9/04

6040B lo w s pe r m m hrs

K.ThorntonCaved at:

269.99 m

203 mm63.5 kg/Auto

76.2 cm

Sheet: 1 of 1

B O

R

IN

G L

O G

5-

3( 5)

.G P

J F

H W

A _V

A .G

D T

/2

6/

2-2-3-3

Water Content %

G ra ph ic

Lo g

Remarks:

Plastic Limit

Borehole Termination Depth 6.7 m

Medium dense, brown SILTY SAND and ROCK

FRAGMENTS

(Wet)

Very dense, tan and brown SAND (Wet)

Loose, brown SILTY SAND, little of weathered rock fragments (Moist) [A-2-4(0)]

FILL

0.39624

0.3048

0.36576

6.7

6.1

4.6

1.5

6-8-12-26

32-38-14-5

2-3-4-8

0.27432

Station 09+495

J-4

J-3

J-2

J-1

(Blows / 0.3m)

Ozark National Forest, Johnson County, Arkansas

N o.

Auger Cuttings

UD

Sample Types:

Project Location:

Boring No.:

Boring Location:

Weather:

Standard Penetration Test Data Liquid Limit

MATERIAL DESCRIPTION

Penetrometer Rock CoreSPT

AR PFH 65-3(5)

Operator:

Encountered at: Inspector:

R ec

SAMPLE

Ty pe

RB-3

At Completion:

Groundwater Depth:

1. No groundwater was encountered during or after drilling.

BORING LOG FEDERAL…