UT.FLAP.70131(1).Strawberry_Sheep_Creek.Geotech_FINAL.2019.pdf

STRAWBERRY-SHEEP CREEK CONNECTOR

UNICORN RIDGE – INDIAN CREEK ROAD

(FOREST ROAD 70042)

UINTA-WASATCH-CACHE

NATIONAL FOREST, UT

UT FLAP 70131 (1)

FINAL Geotechnical Report

Report No. UT-FX-70131-19-01

Prepared by:

Federal Highway Administration

Central Federal Lands Highway Division

Geotechnical Services Branch

May 2019 ii

SIGNATURE SHEET

Report prepared by: ____________________________________________________________ Devin T. Dixon, P.E., Geotechnical Engineer

Report reviewed by: ____________________________________________________________ James M. Arthurs, P.E., Ph.D., Geotechnical Engineer

Approved for distribution by: ____________________________________________________

Marilyn D. Dodson, P.E., Lead Geotechnical Engineer

Date: _____________________________________

Electronic Distribution N:\UT\ut70131(1)\Geotech\7_FinalDocs K:\TechServices\Geotech\1. Geotech Project Reports Project Management Project Development, Lead Designer

May 2, 2019 i

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page i

Table of Contents

SECTION ONE --INTRODUCTION

1.1. BACKGROUND AND LOCATION

1.2. SCOPE AND PURPOSE

SECTION TWO --GEOLOGY AND SEISMICITY

2.1. REGIONAL GEOLOGY

2.2. SEISMIC DESIGN PARAMETERS

2.3. GEOLOGIC HAZARDS

SECTION THREE --FIELD EXPLORATION

3.1. SUBSURFACE EXPLORATION PROGRAM

3.2. LABORATORY TESTING PROGRAM

3.3. CUT AND FILL SLOPES

SECTION FOUR --ANALYSIS AND RECOMMENDATIONS

4.1. CUTSLOPE EVALUATION

4.2. ROCKFALL CATCHMENT DITCH

4.3. REINFORCED SOIL SLOPES (RSS) DESIGN

4.4. ROCKERY DESIGN

4.5. EMBANKMENT CONSTRUCTION

4.6. SHRINK/SWELL RECOMMENDATIONS

4.7. GEOSYNTHETICS

4.8. CONSTRUCTION CONSIDERATIONS

SECTION FIVE --LIMITATIONS

SECTION SIX --REFERENCES

ii

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page ii

TABLES

Table 2.1: Summary of Nearby Active Faults

Table 2.2: Summary of Seismic Parameters for Site Class C

Table 3.1: Summary of the Field Exploration Program

Table 3.2: Summaries of Laboratory Index Test Results

Table 3.3: Soil Type Categories within the Cutslopes

Table 4.1: Summary of Cut and Fill Slope Recommendations

Table 4.2: RSS Design Parameters

Table 4.3: Summary of RSS Global Stability Analyses

Table 4.4: Recommended Safety Factors for Static and Seismic Design

Table 4.5: Material Properties used in the Analysis for Both Rockeries

Table 4.6: Rockery Geometry

Table 4.7: A Summary of Calculated Factors of Safeties

FIGURES

Figure 1: Typical Roadway Conditions

Figure 2: Applicable Ditch Widths for Varying Slope Heights

Figure 3: Illustration of the Rockery Parameters Used in Design

PLATES

Plate 1: Location Map

Plate 2: Geology Map

Plate 3: Geotechnical Boring Locations

APPENDICES

Appendix A: Field Exploration Program

Appendix B: Laboratory Test Results

Appendix C: Reinforced Soil Slope & Rockery Analysis

Appendix D: Photos

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 1

SECTION ONE--INTRODUCTION

1.1. BACKGROUND AND LOCATION

This report presents the results of the geotechnical engineering study and provides recommendations for the reconstruction of the 12.3-mile long section of the Strawberry-Sheep Creek Connector UT FLAP 70131(1) project. The project involves improvements to the Unicorn Ridge-Indian Creek Road, also known as Forest Road 70042. The project corridor is in the Wasatch Range, within the Uinta-Wasatch-Cache National Forest, Wasatch and Utah Counties, Utah. The project begins at the intersection of Sheep Creek-Rays Valley Road (FR 70051) at Sta.

400+19.72 at an approximate elevation of 8,490 feet. The road climbs to a high point of approximately 8,600 feet near the intersection with Bald Mountain Road (FR 70043) and then descends in a northerly direction, ending at an approximate elevation of 7,630 feet at the junction with West Side Strawberry Road (FR 70131) at Sta. 1047+54.24. In addition, minor pavement rehabilitation is proposed along the West Side Strawberry Road, north of the intersection with Unicorn Ridge-Indian Creek Road. The project is located in undeveloped forested terrain between the aforementioned elevations with varying seasonal precipitation. Due to the high elevations along the route, construction on this route will be limited to spring, summer, and autumn months (April through October) depending on winter precipitation and temperatures. A site map is presented on Plate 1.

Figure 1: Typical Roadway Conditions

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 2

The Unicorn Ridge-Indian Creek Road serves as a portion of the connection between U.S.

Highway 6 to the south and U.S. Highway 40 to the north, and provides access to Strawberry Reservoir and recreational areas, including fishing, boating, biking/hiking trails, hunting, and camping. The overall goal of the Strawberry-Sheep Creek improvement project is to balance transportation requirements and roadway maintenance within an environmentally sensitive setting.

The Unicorn Ridge-Indian Creek Road currently exists as a 22-foot-wide gravel surfaced road. The first 6.2 miles of the route is winding with some switchbacks and relatively steep grades. The remaining 6.1 miles is relatively straight and descends gently to the north. The route passes through scrub land and forest in hilly to mountainous terrain. Cuts are typically excavated into colluvium and residual soils with side cast embankments to provide the existing roadway width. The current average daily traffic is estimated by National Forest personnel to be between 500 and 1,000 vehicles per day.

This project proposes to pave the existing road to provide two 11-foot lanes and 1-foot paved shoulders (24-foot total width) with minor realignment. Pavement will significantly reduce the roadway maintenance costs, improve surface drainage significantly, and reduce safety hazards such as washboards in the road surface. To complete the proposed widening and realignment, cuts and fills are expected. Culvert replacements are also proposed. Areas with noted seepage or soft subgrade will be overexcavated and stabilized using geotextile fabric.

1.2. SCOPE AND PURPOSE

The scope of work included geotechnical investigation, analysis, and recommendations for cuts and fills within the project limits for use in design and construction. This involved several tasks including field reconnaissance, subsurface sampling, laboratory testing, interpretation and correlation of data, and geotechnical engineering analysis. Specifically, this investigation is to determine the soil profiles at each cut and fill location and develop recommendations concerning embankments, cut slopes, surface/subsurface drainage, corrosion potential, geological hazards, material shrink/swell, and construction considerations for the design and construction of slopes and retaining structures within the alignment. The stationing in this report is based on the preliminary 70 percent project plans, dated September 10, 2018.

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SECTION TWO--GEOLOGY AND SEISMICITY

2.1. REGIONAL GEOLOGY

The project is located within the Wasatch Range, a north-south oriented mountain range that stretches from the Utah-Idaho border to central Utah. The Wasatch Range is located within the Middle Rocky Mountains Province of the Rocky Mountain System, and forms the western boundary of these physiographic regions. The range is composed primarily of sedimentary rocks with ages ranging from Pennsylvanian (approximately 323 million years old) to Tertiary (approximately 28.5 million years old). The principle mapped deposits in the project area consist of sandstone, siltstone, conglomerate, and claystone of the Duchesne River Formation, and sandstone, siltstone, shale, and limestone of the Green River Formation (Bryant, 1992). A geology map of the area can be found on Plate 2.

Several known Quaternary faults are mapped within approximately 40 miles of the roadway alignment. These faults are considered inactive and are summarized on Table 2.1 below. These structures are on the east flank of the Sawatch Range and the western boundary of the upper Arkansas Valley graben, the northernmost expression of the Rio Grande Rift. Movement on the Sawatch Fault has occurred within the last 15,000 years. The timing of most recent movement on the other faults is less clear, but is estimated to have occurred within the last 1.6 million years. No known active faults underlie or are closely associated with the project site (U.S. Geological Survey, (2018).

The soil units for the general area consist mainly of colluvium and marine deposits. These sediments range from silt to rock fragments of assorted sizes.

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 4

Table 2.1: Summary of Nearby Active Faults

FAULT OR FAULT ZONE

DISTANCE

FROM

CENTER OF

PROJECT

FAULT

PARALLEL

SLIP RATE

FAULT

LENGTH AGE

(miles) (inch/year) (miles) (years)

Wasatch fault zone, Provo section 18.49 0.04 - 0.2 37 <1,600,000

Wasatch fault zone, Nephi section 27.1 0.04 - 0.2 27 <1,600,000

2.2. SEISMIC DESIGN PARAMETERS

The American Association of State Highway and Transportation Officials (AASHTO) criteria for recommended seismic response parameters are based on the (AASHTO) LRFD Bridge Design Specifications, 7th Edition, 2014, and represents horizontal peak ground acceleration (PGA) with 7 percent probability of exceedance in 75 years (approximate 1000-year return period). The 1000-year return period uniform hazard spectrum for Strawberry Sheep Creek Road (40.0749º N latitude and -111.2116º W longitudes) was obtained in accordance with the AASHTO ground motion maps.

The site was classified as “Class C” according to site class definitions specified in Table 3.10.3.1-1 of AASHTO. The recommended spectral acceleration coefficient values for probabilistic design are summarized in the following table.

Table 2.2: Summary of Seismic Parameters for Site Class C

Peak Seismic Ground Acceleration Coefficient, (As) 0.203

Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SDS) 0.470

Horizontal Response Spectral Acceleration at Period of 1.0 sec (SD1) 0.230

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 1.2

Site Factor at Short-Period of Acceleration Spectrum, (Fa) 1.2

Site Factor at Long-Period Range of Acceleration Spectrum, (Fv) 1.662

Based on the long acceleration coefficient SD1 value of 0.230, the site is assigned to seismic hazard Zone 2 in accordance with Table 3.10.6-1 of AASHTO.

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2.3. GEOLOGIC HAZARDS

The Unicorn Ridge-Indian Creek Road is a high elevation road with rugged topography and adverse climatic conditions. Due to the steep terrain, rock fall and landslides could potentially occur within the project area. Some fine-grained soils in the project area are highly erodible, presenting concerns for performance of the roadway prism. Shallow groundwater in limited areas of the project may affect performance of the subgrade materials. Sandstone, siltstone, claystone, and limestone rock units are frequently susceptible to slaking and deterioration when exposed to alternating wetting and drying cycles in rock cuts. Differential erosion of cuts in sedimentary rocks is a common cause of rockfall. These hazards can generally be mitigated by constructing slopes at appropriate angles, as discussed in Section 4 of this report.

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SECTION THREE--FIELD EXPLORATION

3.1. SUBSURFACE EXPLORATION PROGRAM

Central Federal Lands Highway Division (CFLHD) of the Federal Highway Administration (FHWA) geotechnical personnel conducted a subsurface investigation during October 1 to 2, 2018, to characterize the subsurface materials at potential cut and fill areas where retaining structures are proposed. The geotechnical subsurface exploration program consisted of drilling a total of four (4) borings. The purpose of the geotechnical borings was to investigate the proposed retaining structure locations. Boring locations are shown on Figure A-3, Geotechnical Boring Locations, in Appendix A. Subsurface conditions were logged and representative samples were collected and transported to the CFLHD Materials Laboratory in Lakewood, CO, for physical property testing. Logs of the explorations and laboratory test results are presented in Appendix A and B, respectively. A summary of the field exploration is provided in Table 3.1.

Table 3.1: Summary of the Field Exploration Program

EXPLORATION

DESIGNATION STATION OFFSET GROUND

ELEVATION

TERMINATION

ELEVATION

EXPLORATION

DEPTH

BH18-01 450+00 10-ft RT 7,540 ft 7,521 ft 19 ft

BH18-02 507+00 10-ft RT 7,780 ft 7,762 ft 18 ft

BH18-03 547+00 10-ft RT 7,840 ft 7,811 ft 29 ft

BH18-04 600+50 10-ft RT 8,370 ft 8,355.5 ft 14.5 ft

Note: The exploration locations and elevations were estimated relative to features shown on the 70 percent project plans. Elevations were estimated from Google Earth.

Additionally, twenty-five (25) pavements borings, each approximately 5 feet deep, were also completed along the Unicorn Ridge-Indian Creek Road and West Side Strawberry Road alignments.

The purpose of the pavements borings was to evaluate the existing subgrade conditions of the unpaved Unicorn Ridge-Indian Creek Road and distressed portions of the West Side Strawberry Road. The shallow pavement borings are discussed under separate cover in the Pavement Report.

EXPLORATORY BORINGS:

DA Smith Drilling Company of Loma, Colorado, provided the drilling services using a 2002 Simco Drill Rig Model 9100 truck-mounted drill rig. Both the geotechnical and pavement borings were advanced using 6-inch outside diameter hollow stem augers. Upon completion of drilling activities, field personnel backfilled the borings with cuttings generated during the drilling.

Drilling was completed in one mobilization. The geotechnical borings were completed on October 1st, 2018 along with a small number of the pavement borings. The remainder of the pavement borings were completed on October 2nd, 2018.

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Disturbed samples were obtained from the borings using the Standard Penetration Test (SPT), in accordance with AASHTO T-206. The SPT involves driving a 2-inch outside diameter, 1.375-inch inside diameter split spoon sampler 18 inches with a 140-pound hammer falling 30 inches and recording the blow counts per 6-inch of driving. An automatic-trip hammer was used to drive the samplers. The SPT N-value is the sum of the blow counts required to drive the sampler over the second and third 6-inch increments. The N-value provides a means for evaluating the relative density of cohesionless soils and consistency or stiffness of cohesive soils.

The four geotechnical borings were originally intended to be advanced to 40-feet; however due to the presence of gravel, cobbles, boulders, and rock layers, they were terminated earlier. In addition to the SPT samples mentioned above, grab samples were also collected when layer changes were noted that did not correspond with the SPT sampling frequency. Soil from the SPT split-spoon sampler and from grab samples were placed and sealed in plastic bags and were transported to the CFLHD Materials Laboratory for testing.

Photos of drilling equipment and field exploration activities are included in Appendix D.

3.2. LABORATORY TESTING PROGRAM

Soil samples recovered from the borings were tested in the laboratory to support the field classifications and to provide an estimate of the engineering characteristics and mechanical properties of the soil. Laboratory tests included gradation (AASHTO T88), classification (AASHTO M145) and Atterberg limits (AASHTO T89 and T90). When the necessary tests were completed, samples were classified using the Unified Soil Classification System (USCS) and AASHTO soil classification system. A summary of the soil test results is shown in Table 3.2.

Table 3.2: Summaries of Laboratory Index Test Results

BORING

NUMBER

SAMPLE

DEPTH, ft

PERCENT

SAND

PERCENT

PASSING 200 LL PI USCS AASHTO

BH18-01 2.5 50 43 49 22 SC A-7-6(5)

BH18-01 6 53 44 50 23 SC A-7-6(6)

BH18-02 1.5 38 48 33 4 SM A-4(0)

BH18-02 11.5 54 16 - - SM* A-1-b* BH18-03 2.5 24 15 - - GM* A-1-a*

BH18-03 12.5 30 69 - - - -

BH18-03 17.5 43 52 42 24 CL A-7-6(9)

BH18-04 7.5 and 12.5 27 29 35 29 GC A-2-4(0)

* Classifications based on field descriptions and incomplete lab testing.

- Tests not completed.

Soil test results indicated a range of material types including silty to clayey sand and gravel to sandy clay materials, classifying as A-1-a to A-7-6 by AASHTO and GC, SM, SC and CL by USCS. A pH test was conducted on a sample from boring BH18-03 at a depth of 12.5 feet, and resulted in a value of 8.4.

The results of the laboratory tests are presented in Appendix B.

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3.3. CUT AND FILL SLOPES

Cut and fill slope conditions were evaluated along the roadway alignment. Cut and fill slopes were observed to be of variable slope ratios and heights. The evaluation was conducted to assess the stability of existing slopes and to determine the safe slope cut ratios for various slopes along the route. Existing cut slopes extend to a height of approximately 50 feet in isolated areas and show evidence of continuous raveling and erosion. Cut slopes in soil within the roadway alignment generally vary between 20 to 35 degrees from horizontal and cut slopes in weathered bedrock range from 29 to 35 degrees, while naturally occurring slopes are typically found between 8 and 33 degrees. Fill slopes are typically less than 45 feet in height and banked at angles of about 15 to 45 degrees.

Careful visual inspection of slopes, along with geological knowledge provided a good indication as to whether a particular slope is stable. In general, slopes with smooth contours indicated that the slopes have been formed by surface erosion processes without slip movement. On the other hand, irregular surfaces with stair stepping contours, scarp lines, slopping trees, or changes of vegetation indicated slope slumping. Although the majority of the existing soil cut slopes along the roadway appeared to meet a stable factor of safety for low volume roads, erosion and revegetation of slopes appeared to be a concern for many slopes. For cutslope design purpose, materials encountered were categorized into three different types as shown in Table 3.3.

Table 3.3: Soil Type Categories within the Cutslopes

GENERALIZED SLOPE MATERIAL DESCRIPTION

Soil Type ① - SM Silty sand with gravel. Minor limestone and cobbles.

Soil Type ② - SM/SC Silty to clayey sand with gravel and cobbles. Frequent sandstone blocks and ledges

Rock Type ③ - HWBDR Weathered limestone/shale

In the lower segments, small size rock fragments typically fallout of the rock cut face onto the roadway creating a maintenance issue. Poor excavation techniques during initial roadway construction likely contributed to fracturing nature of the cutslope.

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SECTION FOUR--ANALYSIS AND RECOMMENDATIONS

This section provides analysis and recommendations for the cut slope evaluations, rockfall catchment ditch, reinforced soil slopes (RSS), rockery construction, embankment construction, and construction considerations.

4.1. CUTSLOPE EVALUATION

Expansion of the existing cutslopes is proposed to accommodate roadway design concepts. Table

4.1 summarizes existing cutslope materials and geometry and provides new cutslope ratios for design. Recommended slope ratios are based on observed conditions at the existing cut face, investigation data, and anticipated slope height. In general, non-saturated coarse-grained granular soil slopes can be constructed at a safe slope ratio of 1V:1.5H or flatter; non-saturated slopes composed of fine-grained, cohesive soils can be constructed at a safe slope ratio of 1V:2H;

weathered bedrock slopes can be constructed at a slope ratio of 2V:1H or flatter depending on fracturing and degree of weathering; and combination soil and rock slopes can be cut at 1V:1H.

Cutslopes should not exceed slope ratios presented in Table 4.1. Areas of observed springs and seeps encountered during construction may require flattening or additional support and should be evaluated by the CFLHD geotechnical engineer on a case by case basis. Steeper slopes decrease the likelihood of re-vegetation and increase the likelihood and frequency of slumping, raveling, and rock fall events; flatter slopes should be utilized where possible. Critical cutslope location photos are included in Appendix D.

On-site soils encountered within the anticipated excavation and construction limits generally consist of colluvial and residual silty to clayey sands with varying amounts of gravels and silt and clay/silt soils.

Table 4.1: Summary of Cut and Fill Slope Recommendations

BEGIN

STA.

END

STA. OFFSET

EXISTING

SLOPE

HEIGHT

(FT)

CUT/FILL

CUT SLOPE

MATERIAL

TYPE

Described in

(TABLE

3.3)

MAX

RECM.

SLOPE

RATIO

(V:H)

MAXIMUM

RECM.

SLOPE

HEIGHT

(FT)

NOTES AND

RECOMMEND.

400+84 421+00 RT 5-8 FILL * 1:2 15

419+00 422+40 LT 12 CUT SM 1:2 15

423+00 437+00 LT 8 FILL * 1:2 15

424+00 438+00 RT 4 FILL * 1:2 10

437+10 439+40 LT 6 CUT SM/SC 1:2 10

440+00 443+00 RT 24 FILL SM 1:2 30

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 10

BEGIN

STA.

END

STA. OFFSET

EXISTING

SLOPE

HEIGHT

(FT)

CUT/FILL

CUT SLOPE

MATERIAL

TYPE

Described in

(TABLE

3.3)

MAX

RECM.

SLOPE

RATIO

(V:H)

MAXIMUM

RECM.

SLOPE

HEIGHT

(FT)

NOTES AND

RECOMMEND.

444+00 460+00 LT 11 CUT SM 1:2 15

Construct paved ditch with curb and rockery from STA

444+00 to STA 460+00. Limit slope above rockery to 1:3. Maximum total wall height, including embedment, is 14 feet.

460+50 467+50 RT/LT 3 FILL * 1:2 10

467+00 468+50 LT 6 CUT SM 1:2 10

468+50 472+00 RT 18 FILL * 1:2 20

472+60 473+00 RT 20 CUT HWBDR 1:2 30

473+50 480+50 RT 5 FILL SM 1:2 10

478+50 480+00 LT 6 FILL * 1:2 10

481+40 496+30 RT 28 CUT SM/SC 1:2 35

Construct underdrain from

Sta. 480+00 to Sta.

490+00.

499+00 501+50 LT 6 FILL * 1:2 30

RSS at 1:1.5 or 1:2 conventional fill slope to catch.

502+00 506+00 RT 33 CUT SM 1:2 40

505+50 510+50 LT 19 FILL * 1:1.5 25 RSS at 1:1.5

510+50 526+00 RT 44 CUT HWBDR 1:1.5 50

526+00 536+00 LT 22 FILL * 1:2 30

RSS from Sta.

526+00 to Sta.

531+00 at 1:1.5, rock embankment from Sta. 532+50 to 536+00.

544+30 550+00 RT 43 FILL SM 1:1.5 50 RSS at 1:1.5 to 1:2

566+00 570+50 LT 10 FILL * 1:2 20

573+50 575+00 LT 19 FILL * 1:2 25

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

580+00 598+50 LT 8 FILL * 1:2 15

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 11

BEGIN

STA.

END

STA. OFFSET

EXISTING

SLOPE

HEIGHT

(FT)

CUT/FILL

CUT SLOPE

MATERIAL

TYPE

Described in

(TABLE

3.3)

MAX

RECM.

SLOPE

RATIO

(V:H)

MAXIMUM

RECM.

SLOPE

HEIGHT

(FT)

NOTES AND

RECOMMEND.

596+50 600+00 RT 10 CUT SM 1:2 15

599+50 603+00 LT 18 FILL * 1:2 25

606+00 609+50 LT 60 FILL * 1:2 40

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

609+00 615+50 RT 19 CUT HWBDR 1:1.5 25

623+75 630+00 LT-RT

6 (LT)

2 (RT)

FILL * 1:2 10

630+90 636+50 LT 42 FILL * 1:2 50

636+50 639+00 LT 42 FILL * 1:2 50

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

633+50 637+50 RT 11-17 CUT SM/SC 1:2 20

642+00 643+50 LT 16 FILL * 1:2 20

650+90 654+50 RT 13 CUT * 1:2 15

660+00 661+30 LT 21 CUT SM/SC 1:2 25

668+20 669+00 LT 52 CUT SM/SC 1:2 55

686+00 688+50 LT 30 FILL * 1:2 30

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

694+00 695+00 LT 30 FILL * 1:2 30

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

699+00 702+00 RT 10 FILL * 1:2 10

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

724+00 726+00 RT 13 FILL * 1:2 15

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 12

BEGIN

STA.

END

STA. OFFSET

EXISTING

SLOPE

HEIGHT

(FT)

CUT/FILL

CUT SLOPE

MATERIAL

TYPE

Described in

(TABLE

3.3)

MAX

RECM.

SLOPE

RATIO

(V:H)

MAXIMUM

RECM.

SLOPE

HEIGHT

(FT)

NOTES AND

RECOMMEND.

728+50 732+00 LT 15 FILL * 1:2 15

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

734+75 739+00 LT 4 FILL * 1:2 10

741+00 743+00 LT 10 FILL * 1:2 15

746+60 748+50 LT 4 FILL * 1:2 10

748+50 750+50 RT 17 CUT SM/SC 1:2 20

753+20 756+10 LT 15 FILL * 1:2 20

Rock embankment 8-foot max. height to catch on existing bench, or fill at 1:2 to catch.

759+90 763+90 RT 13 CUT SM/SC 1:2 15

760+80 763+00 LT 12 CUT * 1:2 15

766+50 768+60 RT 12 CUT * 1:2 15

Wet slope. Possible seepage. Consider adding roughly 100 feet of underdrain in this area.

769+60 778+50 RT 21 CUT SM/SC 1:2 25

779+50 780+00 LT 5 FILL * 1:2 5

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

783+80 793+00 RT 23 CUT * 1:2 25

808+00 810+60 RT 34 CUT HWBDR 1:2 40

Slope is creeping and saturated.

Consider laying back.

812+25 815+00 RT 15 CUT SM/SC 1:2 20

818+50 820+00 RT 30 CUT HWBDR 1:2 35

827+80 828+00 LT 47 FILL * 1:2 50

828+30 831+50 RT 47 CUT HWBDR 1:2 50

Standing water on LT side. Possible subexcavation area (roughly 300 feet)

833+50 841+50 RT 20 CUT HWBDR 1:2 25

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 13

BEGIN

STA.

END

STA. OFFSET

EXISTING

SLOPE

HEIGHT

(FT)

CUT/FILL

CUT SLOPE

MATERIAL

TYPE

Described in

(TABLE

3.3)

MAX

RECM.

SLOPE

RATIO

(V:H)

MAXIMUM

RECM.

SLOPE

HEIGHT

(FT)

NOTES AND

RECOMMEND.

844+50 847+50 RT 9 CUT HWBDR 1:2 10

854+50 866+00 LT 15 FILL * 1:2 20

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

869+10 876+00 LT 34 CUT SM 1:2 35

Construct paved ditch with curb and rockery. Limit slope above rockery to 1:3. Maximum total rockery height, including embedment, is 14 feet.

888+00 890+00 LT 52 CUT HWBDR 2:1 55

Add rock catchment ditch, see Section 4.2.

891+50 893+00 RT 15 FILL * 1:2 15

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

901+00 911+00 RT 10 FILL * 1:2 10

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

934+00 938+50 LT 8 CUT SM 1:2 10

941+00 942+00 RT 10 FILL * 1:2 10

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

960+75 961+00 RT 5 FILL * 1:2 5

980+00 984+50 LT 5 FILL * 1:2 5

993+75 995+00 RT 5 FILL * 1:2 6

997+00 998+00 LT 5 CUT * 1:2 5

1010+00 1011+50 RT 4 FILL * 1:2 10

1018+50 1020+00 RT 5 FILL * 1:2 5

1028+50 1029+00 LT 5 FILL * 1:2 5

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 14

BEGIN

STA.

END

STA. OFFSET

EXISTING

SLOPE

HEIGHT

(FT)

CUT/FILL

CUT SLOPE

MATERIAL

TYPE

Described in

(TABLE

3.3)

MAX

RECM.

SLOPE

RATIO

(V:H)

MAXIMUM

RECM.

SLOPE

HEIGHT

(FT)

NOTES AND

RECOMMEND.

1035+50 1045+00 RT 10 FILL * 1:2 10

Rock embankment 8-foot max. height to catch on existing bench, or 1:2 fill slope to catch.

* Geology not apparent due to vegetation or snow on slope.

4.2. ROCKFALL CATCHMENT DITCH

One location along the proposed alignment of Strawberry Sheep Creek Road was determined to have the potential for rockfall. This location was between STA 888+00 to STA 890+00. Two rockfall mitigation methods were evaluated for this area: laying back the cut slope to a lower slope face angle and ditch widening to reduce the risk associated with the rockfall hazards. Laying back the cut slope was determined to not be a viable option due to environmental constraints on the slope above the existing cut slope that should not be disturbed. Therefore, catchment ditch construction was determined to be the preferred mitigation method for this project site.

A rockfall catchment area is defined as the area between the roadway edge of shoulder and the base of a cut slope used to restrict a high percentage of rockfalls from reaching the roadway. The use of catchment areas to contain and restrict rockfall from reaching the roadway is one of the best and most effective rockfall protective measures. Rockfall Catchment Area Design (RCAD) Version 1.1 was used to analyze the ditch catchment effectiveness of various slope heights. The intent of the study was to determine what ditch width would yield 80 percent catchment for different slope heights. The chart below summarizes the corresponding ditch widths to slope heights assuming 80 percent catchment for a slope cut at 2V:1H and a 1V:4H ditch slope. Based on this study, a maximum 10-foot ditch and a minimum 7-foot wide ditch is recommended for the proposed cut slope (see Figure 2 below).

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 15

Figure 2: Applicable Ditch Widths for Varying Slope Heights

4.3. REINFORCED SOIL SLOPES (RSS) DESIGN

Limited bench width along some portions of the project alignment necessitates the construction of either additional cut or fill slopes. At spot locations, the construction of conventional embankments would have a significant impact on the local environment. To reduce impacts, RSS are proposed for the following locations: STA 499+00, STA 507+00, STA 526+50, and STA 548+50. A wall alternative was considered, however, due to right-of-way, environmental constraints, and cost reinforced soil slopes were determined to be the optimal technical solution.

The RSS design will consist of compacted select fill and geosynthetic reinforcement vertically spaced at 2-foot intervals for maximum total heights of 22.5 feet to 45 feet. It is possible that on-site material could be used as fill material with proper processing. The analyses and recommendations for the RSS are in general accordance with the design methodologies and guidelines in FHWA Publication NHI-10-024 and NHI-10-025, Volumes 1 and 2, respectively, entitled Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes, dated November 2009.

Soil and rock strength properties used in RSS analysis were selected based on the results of the subsurface investigation and laboratory testing program and are summarized in Table 4.2. These properties were based on correlated values related to both soil classification and density. No direct shear tests were performed.

40 60 80

D itc h W id th

(f t)

Slope Height (ft)

Slope Height vs. Ditch Width (based on RCAD data and assuming 80% catchment)

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 16

Table 4.2: RSS Design Parameters

Material Unit Weight γ, (pcf)

Friction Angle ϕ, (deg)

Cohesion Intercept c, (psf)

RSS Fill 125 30 25

On-Site Soil/Fill 120 30 100

Bedrock 130 34 100

The reinforcement analyses were performed using ReSSA, Version 3.0, and SLIDE, Version 7.0.

Analysis methods are detailed in Appendix C. Critical cross sections at each identified location were checked for stability using the conservative Bishop modified method to compute the slope stability safety factor. Three scenarios were evaluated for each critical section. These scenarios included evaluation of existing conditions, proposed fill with geosynthetic reinforcement (RSS) at static conditions, and proposed fill with geosynthetic reinforcement (RSS) at seismic conditions.

The results are summarized in Table 4.3 below and are presented in Appendix C.

Table 4.3: Summary of RSS Global Stability Analyses

Stationing

Proposed Maximum Slope Face

Ratio (V:H)

Proposed Maximum

Slope Height (feet)

Length of Reinforcement Analyzed (feet)

Percentage of Reinforcement

Length to Height

Existing Factor of Safety

Static Factor of Safety

Seismic Factor of Safety

499+00-STA 1:1.5 22.5 11 50% 1.89 1.64 1.29

507+00-STA 1:1.5 32 16 50% 1.45 1.45 1.18

526+50-STA 1:1.5 32 16 50% 1.38 1.47 1.19

548+50-STA 1:1.5* 36* 20 ≈ 56% 1.44 1.47 1.19

* Maximum height of 45 feet with slope face of 1:2 is less critical than 36-foot design height with 1:1.5 slope face.

The results indicated that the existing ground condition exceeded the desired minimum static factor of safety of 1.3 and that construction of the RSS at these locations will maintain or improve the factors of safety.

The embankment side slopes should be constructed as an RSS and keyed into the general embankment fill. Construct the slopes with maximum heights and slope ratios, and minimum reinforcement lengths as summarized on Table 4.3. The geogrid reinforcement should meet requirements of uniaxial Type II reinforcement geosynthetic (FP-14 and SCR section 714.04) and maximum vertical spacing of no more than 2 feet. Intermediate geosynthetic with a minimum length of 4 feet should be included evenly spaced between the primary reinforcement. Extend the

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 17 top two layers of geogrid from the face of slope to the far edge of the traveled way of the roadway.

Place a rolled erosion control mat over the face of the RSS to aid in revegetation. Incorporate a back-drain system to alleviate subsurface water and control surface water drainage to prevent water running directly over the RSS.

4.4. ROCKERY DESIGN

Rockeries are earth retaining structures constructed of large interlocking, dry-stacked rocks typically placed without mortar or reinforcement. These structures rely on the weight, size, shape, and interface friction of the individual rocks to resist earth pressures and provide overall stability.

Rockeries have been recently utilized on many projects as context sensitive solutions preserving scenic, aesthetic, historic and environmental resources, while maintaining safety and mobility.

Figure 3: Illustration of the Cut-Side Rockery Parameters Used in Design

Rockeries were designed in accordance with the guidelines provided in the Central Federal Lands 2006 publication, “Rockery Design and Construction Guidelines.” Limited geotechnical investigations were conducted at the wall sites; therefore, a conservative design approach was followed. In lieu of soil testing, presumptive soil strength properties for retained and foundation soils were assumed for observed on-site soils. The rockeries were designed as gravity retaining walls and no surcharge load was applied since the walls were located on the cut side of the roadway. Static and seismic lateral earth pressures were applied to the back of the rockery;

however passive earth pressure was neglected at the toe of the wall.

The design was checked for adequate factors of safety against sliding, overturning, and bearing capacity. The recommended factors of safety for static and seismic rockery design are presented in the table below:

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 18

Table 4.4: Recommended Safety Factors for Static and Seismic Design

Mode of Failure Static Factor of Safety Seismic Factor of Safety

Sliding 1.5 1.1 Overturning 2.0 1.5

Bearing 3.0 2.0

Assumed material properties used in the design of the rockeries are presented in Table 4.5. Rockery geometries and the calculated rockery design factors of safety for each wall analysis will be discussed in the following paragraphs.

Table 4.5: Material Properties used in the Analysis for Both Rockeries

Assumed Location

Φ Retained

Soil Friction Angle ɣs Retained Soil Unit Weight

C Soil

Cohesion μ Sliding Friction Factor ɣr

Rockery Face Unit Weight

Kh

(½ PGA)

Horizontal Seismic

Coefficient

Kv Vertical Seismic

Coefficient

Qs Vertical

Surcharge

STA 443+50

to STA 460+00

STA 869+00

to STA 876+00

30° 120 pcf 0 psf 0.577 150 pcf 0.102 0 0 psf

It is recommended that rockeries be constructed between STA 443+50 to STA 460+00. Rockeries were also proposed between STA 869+00 to STA 876+00 based on the 70% design drawings.

Subsequent revisions including the addition of paved ditches and concrete curb have alleviated the need for rockeries at this location. These two locations present steep slope conditions and loose, unconsolidated soils that warrant the need for a retaining-type structure that blends into the natural aesthetics of the environment. At their maximum, these rockeries area estimated to be 14 feet high and it is recommended that the base width be a minimum of 2.5 feet. The base rock should also be embedded a minimum of 1 foot. The base rock width will be determined by the height of the proposed wall at each location. The backslope angle, β, should also be equal to approximately 18.4 degrees and the face batter and back cut inclination should be constructed at 4:1 and 8:1 (V:H) ratios, respectively. Table 4.6 displays the required base rock widths with a given wall height and Table 4.7 shows the related factors of safety.

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 19

Table 4.6: Rockery Geometry

H Maximum

Height

B Minimum Base

Width 4 ft 2.5 ft 6 ft 4.0 ft 8 ft 5.0 ft

10 ft 6.0 ft 12 ft 7.5 ft 14 ft 8.5 ft

Table 4.7: A Summary of Calculated Factors of Safeties

Factors of Safety Maximum Height

Sliding Factor of Safety

Overturning Factor of Safety

Bearing Capacity Factor of Safety Static 4 ft 2.6 4.9 4.5

Seismic 1.5 2.3 2.4 Static 6 ft 2.7 5.5 5.5

Seismic 1.6 2.6 3.0 Static 8 ft 2.5 4.8 5.1

Seismic 1.5 2.3 2.6 Static 10 ft 2.4 4.4 4.9

Seismic 1.4 2.2 2.4 Static 12 ft 2.5 4.8 5.4

Seismic 1.5 2.3 2.7 Static 14 ft 2.4 4.5 5.1

Seismic 1.4 2.2 2.6

The rockery should be backfilled with free-draining, 6 inch minus granular material. This granular material will also serve as the drainage system for the wall and reduce the buildup of pore water pressures behind the wall. A 4-inch-diameter perforated PVC collector pipe should be installed within the drainage layer near the base of the wall. Class 1, Type C separation geotextile should be placed along the backslope prior to placement of the drainage layer.

4.5. EMBANKMENT CONSTRUCTION

The embankment areas should be constructed with traditional embankment construction methods.

Construct traditional embankments with a maximum slope ratio of 1V:2H to maintain slope stability and promote revegetation of the slope. An erosion control mat or other erosion mitigation devices should be placed on the completed slopes to assist with revegetation requirements.

Construct embankments in accordance with Section 204 of FP-14 and the project special contract requirements (SCR).

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 20

4.6. SHRINK/SWELL RECOMMENDATIONS

It is estimated that these soils will have a 5-10% shrink percentage, corresponding to a shrink/swell factor of 0.95-0.90. The recommended shrink/swell factor is based on a combination of standard tabled values for common materials in the FLH Technical Guidance Manual (2006) and experience with other CFLHD projects in similar materials.

4.7. GEOSYNTHETICS

The geosynthetic recommended for the RSS sections is geogrid reinforcement that should meet the requirements of uniaxial Type II reinforcement geosynthetic (FP-14 and SCR section 714.04). For the rockery a Class 1, Type C separation geotextile should be utilized along the backslope as discussed in Section 4.4. If geosynthetics are needed for other activities during construction such as additional subexcavation, the placement of riprap, or for the use with drains then further recommendations will be made in the future.

4.8. CONSTRUCTION CONSIDERATIONS

Specifications: All geotechnical recommendations stated above are incorporated into the SCRs to amend or are already incorporated within the FHWA Standard Specification for Construction of Roads and Bridges on Federal Highway Projects; known as FP-14.

Roadway Excavation: Excavate using equipment capable of removing the material while preventing material from escaping outside the construction limits.

If bedrock is encountered laterally within the proposed reinforcement lengths for the RSS during construction, a member of the CFLHD geotechnical team should be contacted for evaluation.

Based on the subsurface investigation and surface geologic mapping, the bedrock is expected to be rippable near the surface; however, final determination of bedrock rippability is the responsibility of the contractor. If groundwater is encountered, dewatering and stabilization may be required to construct the RSS.

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 21

SECTION FIVE--LIMITATIONS

The recommendations in this report are based on the data obtained from exploratory borings, field review, and laboratory test results. The results of these explorations and tests represent conditions at the specific locations indicated. Subsurface variations across the site are likely and may not become evident until excavation is performed. The Analysis and Recommendations sections in 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.

Strawberry Sheep Creek, UT FLAP 70131 (1) May 2019 Page 22

SECTION SIX--REFERENCES

ADAMA Engineering Inc, Computer Program, ReSSA, Version 3.0, Copyright 2013.

American Association of State Highway and Transportation Officials (AASHTO), 2014, “AASHTO LFRD Bridge Design Specifications”, 7th Edition.

Berg, Ryan R. et al (2009). “Design of Mechanically Stabilized Earth Walls and Reinforced Soils Slopes – Volumes 1 and 2.” Report No. NHI-10-024 & NHI-10-025, dated November.

Bryant, B. (1992). “Geologic and Structure Maps of the Salt Lake City 1° x 2° Quadrangle, Utah and Wyoming”. 1:125,000. Miscellaneous Investigations Series, Map I-1997. Reston, VA:

U.S. Geologic Survey.

Federal Highway Administration (FHWA), 2007, Geotechnical Technical Guidance Manual, dated May.

Federal Highway Administration (FHWA), 2008, Federal Lands Highway Project Development and Design Manual (PDDM), dated March.

Federal Highway Administration (FHWA), 2017, Soil Description and Identification Guidelines, dated December.

Federal Highway Administration (FHWA), 2017, Rock Characterization Guidelines, dated December.

Mack, Darren A. et al (2006). “Rockery Design and Construction Guidelines.” Report No.

FHWA-CFL/TD-06-006, dated November.

“National Seismic Hazard Map”, United States Geological Survey (USGS), 2008, website:

http://earthquake.usgs.gov/research/hazmap

Portland State University, Computer Program, RCAD-RS VISUAL, Version 1.1, Copyright 2004.

Pierson, L.A., C.F. Gullixson, and R.G. Chassie, 2001, Rockfall Catchment Area Design Guide – Final Report, Oregon Dept. of Transportation Research Group pub. No. SPR-3(032), November 2001.

RocScience Inc, Computer Program, Slide Version 7.0.

U.S. Geological Survey (2018). “Quaternary Fault and Fold Database of the United States.” USGS Earthquake Hazards Program, <http://earthquake.usgs.gov/hazards/qfaults/> http://earthquake.usgs.gov/research/hazmap

PLATES

APPENDIX A

FIELD EXPLORATION PROGRAM

UT FLAP 70131 (1) A-1

APPENDIX A

FIELD EXPLORATION PROGRAM

A.1 INTRODUCTION

The Central Federal Lands Highway Division (CFLHD) Geotechnical Section completed a field exploration program for UT FLAP 70131(1), Strawberry Sheep Creek, from October 1 to 2, 2018. The scope of work for the geotechnical field exploration program included four (4) borings for the proposed RSS locations and twenty-five (25) pavement borings at Strawberry Sheep Creek Road. The pavement borings are discussed under separate cover in the Pavement Report.

The drilling component of the field exploration program was coordinated and observed by CFLHD Geotechnical personnel. Field exploration locations are illustrated on the “Geotechnical Boring Locations” sheet in Plate 3. Individual boring logs are attached. These logs represent a compilation of field and laboratory data and description of the soil and rock by CFLHD Geotechnical personnel. The methods used to conduct the field exploration program are described below. Photos of drilling equipment and field exploration activities are included in Appendix D. All rock and soil samples collected during the field exploration program were transported to the CFLHD Materials Laboratory in Lakewood, Colorado for testing. A summary of the laboratory testing program is provided in Appendix B.

A.2 SOIL AND ROCK CLASSIFICATION SYSTEMS

During the completion of borings, CFLHD Geotechnical personnel collected bulk soil and rock samples and prepared field logs of the borings. Soil identification and descriptions, as shown on the field logs, are based on ASTM D2488, a systematic process for identifying and describing individual soil samples by visual and manual means. When sufficient laboratory testing was completed, select samples from borings were classified using the Unified Soil Classification System (USCS) and American Association of State Highway and Transportation Officials (AASHTO) soil classification system. Both the visual soil identification system and the referenced soil classification systems are summarized in the attached Soil Classification Field Reference. Rock samples were classified based on the stratigraphic structure, rock strength, degree of weathering, and other properties. The rock classification system is summarized in the attached Rock Classification Field Reference.

G rfc

Te xt

!S O

IL

C

A

LS

S

IF

IC

A

TI

O

N C

H A

R T

L

E G

E N

D

3/

/2

3:

:5

P

M

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

Unified Soil Classification System

SOIL CLASSIFICATION CHART & LEGEND

SILTY GRAVELS WITH OR WITHOUT SAND

HIGHLY ORGANIC SOILS

POORLY-GRADED SANDS WITH OR WITHOUT

GRAVEL

CLEAN SANDS

WITH LESS THAN

15% FINES

GRAVELS WITH

15% OR MORE

FINES

GRAVELS

MORE THAN HALF

COARSE

FRACTION IS

LARGER THAN NO.

4 SIEVE

MAJOR DIVISIONS TYPICAL NAMES

WELL-GRADED GRAVELS WITH OR WITHOUT

SAND

POORLY-GRADED GRAVELS WITH OR

WITHOUT SAND

ORGANIC SILTS OR CLAYS OF HIGH

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

PEAT AND OTHER HIGHLY ORGANIC SOILS

CLAYEY SANDS WITH OR WITHOUT GRAVEL

C O

A R

S E

-G R

A

IN

E D

S O

IL

S

M O

R E

T H

A N

H A

LF

IS

C O

A R

S E

R T

H A

N N

O . 2

S

IE

V

E

NOTE: Coarse-grained soils with between 5% and 12% passing the No.200 sieve and fine-grained soils with limits plotting in the gray zone on the plasticity chart have dual classifications.

SILTS AND CLAYS

LIQUID LIMIT 50% OR LESS

Unconfined Compression No Recovery

SILTS AND CLAYS

LIQUID LIMIT GREATER THAN 50%

UC

NR

FI

N

E -G

R A

IN

E

D S

O

IL

S M

O R

E T

H A

N H

A

LF

IS

F

IN

E

R T

H A

N N

O . 2

S

IE

V

E

SANDS WITH 15%

OR MORE FINES

SANDS

MORE THAN HALF

COARSE

FRACTION IS

FINER THAN NO. 4

SIEVE SIZE

INORGANIC CLAYS OF HIGH PLASTICITY

WITH OR WITHOUT SAND OR GRAVEL

Liquid Limit Plastic Index Moisture Content Dry Density Non Plastic No Valve

Water Level at Time of Drilling

Stabilized Water Level

CLEAN GRAVELS

WITH LESS THAN

15% FINES

Abbreviations

WELL-GRADED SANDS WITH OR WITHOUT

GRAVEL

CLAYEY GRAVELS WITH OR WITHOUT SAND

INORGANIC SILTS OF LOW TO MEDIUM

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

INORGANIC CLAYS OF LOW TO MEDIUM

PLASTICITY WITH OR WITHOUT SAND OR

GRAVEL

LL

PI

W

DD

NP

NV

SILTY SANDS WITH OR WITHOUT GRAVEL

ORGANIC SILTS OR CLAYS OF LOW TO

MEDIUM PLASTICITY WITH OR WITHOUT

SAND OR GRAVEL

INORGANIC SILTS OF HIGH PLASTICITY WITH

OR WITHOUT SAND OR GRAVEL

Use primary colors or hyphenated compound primary colors. Use "mottled" or "streaked" if necessary.

4. Color Dry Dry to touch, dusty Moist Damp but no visible water Wet Visible free water

5. Moisture Content

Flat Width/Thickness >3 Elongated Length/Width >3

Flat & Elongated Meets both of the above

Applies to sand, gravel, cobbles and boulders.

Length, width and thickness refer to the greatest, intermediate and least dimensions, respectively.

6c. Particle Shape

N Density N Consistency

Unconfined Compressive Strength qu

(tsf)

Undrained Compressive Strength su

(tsf)

Behavior

0-4 Very Loose 0-1 Very Soft <0.25 <0.125 Extrudes between fingers when squeezed

5-10 Loose 2-4 Soft 0.25-0.50 0.125-0.25 Remolded by light finger pressure

11-30 Medium Dense 5-8 Firm 0.50-1.00 0.25-0.50

Imprinted easily with fingers, remolded by strong finger pressure

31-50 Dense 9-15 Stiff 1.00-2.00 0.50-1.00 Imprinted with considerable finger pressure, indented by finger nail

>50 Very Dense 16-30 Very Stiff 2.00-4.00 1.00-2.00 Barely imprinted by fingers or indented by finger nail

>30 Hard >4.00 >2.00 Not imprinted by fingers or difficult to indent with finger nail

SAND & GRAVEL SILT AND CLAY

3. Consistency and Density:

Angular Sharp edges and relatively plane sides.

Subangular Same as angular with rounded edges.

Subrounded Nearly plane sides but well-rounded corners and edges.

Rounded Smooth curved sides and no edges.

Well-

Rounded Very Smooth surfaces, spherical or ovular, no edges.

6b. Particle Angularity Applies to coarse sand, gravel, cobbles and boulders.

Sieve < #200 Flour or smaller

Fine > #200 to #40 Flour to sugar Medium #40 to #10 Sugar to rock salt Course #10 to #4 Rock salt to pea-sized

Fine #4 to 3/4 in. Pea-sized to thumb Coarse 3/4 in. to 3 in. Tumb to fist Cobble 3 in. to 12 in. Fist to basketball

Boulders > 12 in. Larger than Basketball

Material

Gravel

6a. Particle Size

Silt or Clay

Sand

Particle Size Approximate Scale

Example, fine-grained soil: Lean CLAY with Sand (CL)- stiff, brown, moist, medium plasticity, laminated Example, coarse-grained soil: Silty SAND with Gravel (SM)-medium dense, gray, wet, fine to coarse grained, angular to subangular gravel, weakly cemented Example, fine-grained soil (Long Form):

Clayey GRAVEL with SAND (CL-ML)- loose to soft, dark brownish green to pale brownish gray, wet; fine to medium grained, angular, flat sand; coarse grained, rounded elongated gravel, some chert, trace coarse gravel, and cobbles, medium plasticity, dessicated, weak cementation, low dry strength, rapid dilatancy, moderate HCL reaction, hydrocarbon odor, iron oxide staining, alluvium fill, (Quaternary Alluvium), Additional Description.

1. Group Name (Pg. 3) 9.

2. Group Symbol (Pg. 3) 10.

3. Consistency / Relative Density (Pg. 1) 11.

4. Color (Pg. 1) 12.

5. Moisture (Pg. 1) 13.

6. Particle Size / Shape / Angularity (Pg. 1) 14.

7. Plasticity (Pg. 2) 15.

8. Structure (Pg. 2)

Odor (Pg. 2)

Staining (Pg. 2)

Cementation (Pg. 2) Organics Dry Strength (Pg. 2) Dilatancy (Pg. 2) HCL Rxn (Pg. 2)

Weak Crumbles with little finger pressure Moderate Crumbles with considerable finger pressure Strong Will not crumble with finger pressure

Intact coarse-grained soil

9. Cementation

Nonplastic Thread cannot be rolled at any water content.

Low The thread can barely be rolled and the lump cannot be formed when drier than the plastic limit.

Medium The thread is easy to roll and not much time is required to reach the plastic limit. The thread cannot be rerolled after reaching the plastic limit. The lump crumbles when drier than the plastic limit.

High It takes considerable time kneading and rolling to reach the plastic limit. The thread can be rerolled several times after reaching the plastic limit. The lump can be formed without crumbling when drier than the plastic limit.

Toughness test: Shape the specimen into an elongated pat and rolled on a smooth surface or between…