Attachment_05_-_Geotechnical_Report.pdf

February 21, 2014

Geotechnical Engineering Investigation Report Duchesne Bunkhouse Ashley National Forest

To Whom It May Concern:

This report presents the geotechnical findings for the proposed Duchesne Bunkhouse at the southwest corner of 200 West and 400 South in Duchesne, Utah. The objectives of this study were to define subsurface soil and groundwater conditions, then prepare recommendations regarding site grading and foundations. A summary of our findings include:

The allowable bearing pressure for conventional spread footings placed on native undisturbed soil is 1,800 psf.

The soil types across the site varied, it is anticipated that at footing grade, silty sands and silty clays will be encountered. The silty clays are very soft and will be easily disturbed. Any clays beneath footings that become disturbed during construction will have to be removed. To facilitate construction, a 6-inch minimum layer of gravel can be placed over clay, then place footing forms.

Groundwater was encountered at 5 to 8-feet below grade during investigation. It is anticipated that groundwater will be higher during spring and summer months.

Remove all root-balls and roots larger than 1-inch within 3-feet of surface of pavement and below foundations.

All soils supporting foundations or pavements are to be inspected by a Forest Service representative before the placement of footings/slabs. If soil conditions are different from what was observed in this report, our office is to be notified for site specific recommendations.

If you have questions regarding this report or desire additional information please contact us.

Sincerely, Todd Touchard, P.E.

Regional Geotechnical Engineer

USFS Intermountain Region

(801) 625-5224 ttouchard@fs.fed.us

INTRODUCTION 1

Figure 1. Vicinity Map 1

2.0 PROPOSED CONSTRUCTION 1

3.0 FIELD AND LABORATORY INVESTIGATION 2

3.1 Field Investigation 2

Figure 2. Aerial view showing Testpit Locations. 2

3.2 Laboratory Investigation 2

4.0 SITE CONDITIONS 3

Picture 1. Looking Southwest Across Site. 3

4.1 Surficial & Subsurface Soils 3

Picture 2. Testpit 1. 4 Picture 3. Testpit 2. 4

4.2 Groundwater 5

5.0 DESIGN RECOMMENDATIONS 5

5.1 Foundations 5

5.2 Estimated Settlement 6

5.3 Soil Class 6

5.4 Lateral Soil Pressures & Resistance 6

5.5 Liquefaction & Faults 6

5.6 Concrete Slabs & Cement Types 6

5.7 Pavement 7

Flexible Pavements (Asphalt Concrete): Parking Areas/ Access Roads 7

5.8 Drainage Recommendations 7

6.0 GENERAL CONSTRUCTION PROCEDURES AND RECOMMENDATIONS 7

6.1 Foundation Excavations 7

6.2 Subgrade Stabilization 8

6.3 Fill Installation & Compaction 8

6.4 Soil Special Inspection & Testing 8

Table 2. Minimum Frequency of Soil Inspection & Testing. 9

6.5 Aggregate Base Course 9

6.6 Granular Fill 9

7.0 LIMITATIONS 10

Geotechnical Investigation Duchesne Bunk House February 22, 2014

INTRODUCTION

This report presents the geotechnical findings for the proposed building and pavements at the proposed Duchesne Bunkhouse. The location of the site and proposed building location is shown on Figures 1 and 2, respectively. The objectives of this study were to define subsurface soil and groundwater conditions, then prepare recommendations regarding site grading and foundations.

To accomplish the objectives, a field investigation program and laboratory analysis of soil encountered at the site were conducted. The locations of the testpits are presented in Figure 2. The testpit logs are shown in Figures 3. A legend to log symbols and additional soil information is provided in Figure 4.

If the proposed type of structures, location of structures, or use of pavements change, our office shall be notified to review and potentially change recommendations contained in this report. This report should not be used for any other lots, buildings, or structures without prior approval.

Figure 1. Vicinity Map

2.0 PROPOSED CONSTRUCTION

The proposed construction is pre-manufactured bunk house, parking, trailer spurs. Wall load are expected to be less than 1 kips/lf.

SITE

3.0 FIELD AND LABORATORY INVESTIGATION

3.1 Field Investigation

To define the subsurface soil and groundwater conditions, we conducted four testpits using a rubber tired backhoe. Testpits were completed to a required maximum depth of 9.5 feet below grade. Groundwater was encountered in all of the testpits.

Figure 2. Aerial view showing Testpit Locations.

3.2 Laboratory Investigation

For soil classification and engineering properties, the samples obtained from exploratory borings were laboratory tested. Typical laboratory tests include:

Moisture Content Soil Density Sieve Analysis

Fine Particle Size Analysis Atterberg Limits Consolidation Tests

4.0 SITE CONDITIONS

The project site relatively flat and is being used for pasture. The site is covered with grasses and weeds, small trees, and a large tree.

Picture 1. Looking Southwest Across Site.

4.1 Surficial & Subsurface Soils

The surface soils consists of a light brown silty clay topsoil, which overlays layers of silty sands, silty clays and sandy gravels. The soil types and layer thicknesses varied considerably between testpit locations. Individual testpit logs are attached. The sands and gravels were generally loose and we experienced a lot of sidewall caving and sloughing as we excavated near and below the groundwater. The maximum depth we were able to excavate was 9.5-feet.

Picture 2. Testpit 1.

Picture 3. Testpit 2.

4.2 Groundwater

Groundwater was encountered in Testpits. It is anticipated that surface water from spring rain will be the concern for this site. Depending on site grading and time of construction, surface runoff water and soft soils may be encountered at pavement and footing subgrades. Subgrade stabilization is discussed in Section 6.2.

5.0 DESIGN RECOMMENDATIONS

The following recommendations have been developed on the basis of the previously described project characteristics and subsurface conditions. A technical design review should be made by this office if actual loads are greater than anticipated or if there is any change in project criteria, including building location on the site.

Under no circumstances should the footings be installed upon potentially collapsible, non-engineered fills, loose or disturbed soils, sod, rubbish, construction debris, frozen soil, or other deleterious materials. If unsuitable soils are encountered, they must be removed and replaced with compacted granular fill. If granular soils become loose or disturbed, they must be recompacted prior to pouring the concrete.

Prior to the placement of footings, granular site grading fill, or floor slabs, the exposed natural subgrade must be proofrolled by passing moderate-weight rubber tire-mounted construction equipment over the surface at least twice. If any loose, soft, or disturbed zones are encountered, they must be completely removed in footing and floor slab areas and replaced with granular structural fill.

5.1 Foundations

Foundations should not be designed for more than the maximum allowable soil bearing pressures and other soil strength properties below. The allowable bearing pressure may be increased by 1/3 for temporary loads such as wind or seismic forces.

Recommended design parameters:

Minimum Depth of Exterior 30 inches Footings and Unheated Areas

Minimum Depth of Interior Footings 14-16 inches

Recommended Minimum Width for 20 inches Continuous Wall Footing

Recommended Minimum Width for 24 inches Isolated Spread Footing

Recommended Allowable Bearing Pressure* 1,800 psf

*The provided bearing capacity is based on footings placed on native undisturbed soils.

5.2 Estimated Settlement

The anticipated maximum total or differential settlement of foundations designed using the previously mentioned structural loads is not expected to exceed 1/2-inch.

5.3 Soil Class

For dynamic structural analysis, the Site Class D – Stiff Soil Profile as defined in Table 1613.5.2, Site Class Definitions, of the IBC 2012 can be utilized.

5.4 Lateral Soil Pressures & Resistance

Lateral soil pressures are dependent on the type of soil present. The pressures are based on a granular fill being used as backfill. The values below assume that the surface of the soils slope behind the wall is horizontal, and that the granular fill has been placed and lightly compacted, not as a structural fill. The following equivalent fluid lateral soil pressures shall be used for design:

1. Use 55 pcf for the static at-rest case. That is when the wall is not allowed to yield.

2. Use 35 pcf for active static case. Full active pressures only develop when the wall is allowed to move a sufficient distance. For granular soil, the typical movement range is 0.001 to 0.004H, and a cohesive soil is 0.01 to 0.04H, where H is the height of the wall.

3. Use 300 pcf for the static passive case. That is when the wall exerts pressure on the soil.

For the determination of lateral resistance for continuous and spread footings placed on granular structural fill, a friction value of 0.45 may be used for ultimate lateral resistance.

5.5 Liquefaction & Faults

Liquefaction is the result of saturated soils being shaken causing soil particles to easily move, resulting in loss of soil strength and stiffness. A liquefaction study was not conducted on this site.

No active faults or potentially active faults were mapped near the site. The USGS (http://earthquakes.usgs.gov) provide information regarding this fault.

5.6 Concrete Slabs & Cement Types

All concrete slabs on grade should be placed over 4-inch minimum, of ½” to 1” diameter, poorly graded, clean, free-draining gravel. Below the 4-inch gravel layer shall be properly site grading fill extending to native undisturbed granular soil. All fill supporting slabs should be placed in 8-inch loose lifts and compacted to 95% of modified proctor.

The laboratory tests indicate that the native soils contain a low amount of water soluble sulfates and a pH of 8.4. Therefore, no special requirements are needed for cement type.

5.7 Pavement

The pavement section for this development is based upon typical low traffic patterns, AASHTO and Forest Service design information. The recommended binder is PG 58-28 using a ½” mix with a target air void content of 3%.

The following flexible pavement sections, based on projected traffic conditions, are recommended:

Flexible Pavements (Asphalt Concrete): Parking Areas/ Access Roads

Moderate Volume of Automobiles and Light Trucks with Occasional Medium-Weight Trucks;

No Heavy-Weight Trucks

[1 equivalent 18-kip axle load per day]

3.0 inches Asphalt concrete

6.0 inches Aggregate base course

Over Native Sandy Silts

5.8 Drainage Recommendations

Adequate surface drainage should be provided at the site to minimize any increase in moisture content of the foundation and pavement supporting soils and prevent water from migrating under the structure. All areas around the structure should be generously sloped to provide drainage away from these areas. We recommend a minimum slope of 6 inches in the first 10 feet away from the structure. This should minimize the potential problems that could occur if soils below the structure or pavements become wet. We also recommend that the pavement areas be generously sloped to insure that no ponding occur on the surfaces.

6.0 GENERAL CONSTRUCTION PROCEDURES AND RECOMMENDATIONS

The guidelines outlined below address the geotechnically related construction concerns for this project.

6.1 Foundation Excavations

Prior to placement of the foundations and floor sections, all areas that will support foundation loads or pavements should be inspected to insure that all loose, soft or otherwise undesirable material is removed and that the structures will bear on satisfactory material. All topsoil, fill and other deleterious materials underneath the proposed structure and pavement should be removed. Remove all stumps and roots greater that 1-inch in diameter below foundations. Replace with compacted structural fill.

All foundation excavations should be protected against any detrimental change in condition such as disturbance, rain and freezing. Surface runoff should be directed away from the excavation and not allowed to pond. If possible, all footing concrete should be poured the same day as the excavation is made. If this is not practical, the foundation excavation should be adequately protected and foundation placement should take place as soon as possible.

6.2 Subgrade Stabilization

If construction practices or weather conditions during the placement of the fill caused the native soils become soft in paved or footings areas one of the following should be done:

Remove areas where clays or silts are disturbed and place an additional 18-inches of granular fill (crushed or pit-run gravel), gradation requirements are shown in Section 6.7.

Or place Geotextile grid between the undisturbed native soil and fill material to achieve proper compaction of the fill layers. Follow manufacture’s recommendations for lap length and installation. Manufacturer, type, and properties of geotextile grid used shall submitted to geotechnical engineer for approval prior to construction.

6.3 Fill Installation & Compaction

All fills supporting structural loads, pavements, or slabs should be compacted to at least 95 percent of the Modified Proctor maximum density (ASTM D 1557). The compaction should be accomplished by placing the fill in 8-inch loose lifts and mechanically compacting each lift to the specified minimum density. Fill shall be moisture conditioned within two percent of optimum moisture. Field density tests should be performed on each lift as necessary to insure that compaction is being achieved.

All utility trench backfill below structurally loaded facilities (flatwork, floor slabs, roads, etc.) must be placed at the same density requirements established for structural fill. In these areas, backfill material shall consist of granular fill.

If the surface of the backfill becomes disturbed during the course of construction, the backfill should be proofrolled and/or properly compacted prior to the construction of any exterior flatwork over a backfilled trench. Proofrolling may be performed by passing moderately loaded rubber tire-mounted construction equipment uniformly over the surface at least twice. If excessively loose or soft areas are encountered during proofrolling, they should be removed to a maximum depth of two feet below design finish grade and replaced with structural fill.

6.4 Soil Special Inspection & Testing

As required by 2012 International Building Code, special inspections and testing shall be performed by an agency independent of the Contractor. During fill placement, the special inspector shall determine that proper materials and procedures are used in accordance with this report. Furnish all inspection and testing reports to Engineer.

Table 2. Minimum Frequency of Soil Inspection & Testing.

Inspection/Test Method Frequency Verify materials below shallow foundation are adequate to achieve bearing capacity.

Periodic

Verify excavations are extended to proper depth and have reached proper material.

Periodic

Verify use of proper materials, densities and lift thickness during placement and compaction of fill. (ASTM D 1557, D 422, D 2922)

Perform proctor test (ASTM D 1557) at start of project for each type of soil being compacting or when material appears to change.

Submit particle size analysis (ASTM D 422) data for approval before any import fill material is delivered or when fill material appears to change.

Test compaction using nuclear density methods (ASTM D 2922) a minimum of: per 100 lf of backfill and each lift for trenches, every 800 sf and each lift for pavements base and subbase, and as directed by Engineer.

Prior to placement of compacted fill, observe subgrade and verify site has been properly compacted.

Periodic

6.5 Aggregate Base Course

For the base material directly below pavement, we recommend a granular soil free of organic or other deleterious material. We recommend a graded sand and fractured gravel material having between 5 and 11 percent passing the #200 sieve and no particles greater than approximately 1-1/2 -inches in maximum dimension. The minimum CBR value (ASTM D 1883) of 80% is required.

6.6 Granular Fill

Granular soils free of organics, debris, or other deleterious materials are recommended for use as granular fill at this site. Granular fill is defined as a well graded sand and gravel material (pitrun or crushed gravel), with less than 15 percent passing the #200 sieve and no particles greater than 4 inches in maximum dimension. Granular fill should not exhibit plasticity characteristics. Approved soil types as defined using the Unified Soil Classification are considered to be GW, GP, or GM or combinations thereof. Submit proposed fill material samples and sieve analysis to Engineer prior to placement. See Figure 4 for soil type definitions.

7.0 LIMITATIONS

The recommendations provided herein were developed by evaluating the information obtained from the testpits. The testpit data reflects the subsurface conditions only at the specific location at the particular time designated on the testpit log. Soil and ground water conditions may differ from conditions encountered at the actual testpit locations. The nature and extent of any variation in the testpit may not become evident until during the course of construction. If variations do appear, it may become necessary to re-evaluate the recommendations of this report after we have observed the variation.

Our professional services have been performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. This warranty is in lieu of all other warranties, either expressed or implied.

Enclosures: Appendix :

Figure 3 : Logs of Testpits Figure 4 : Soil Classification Chart

Project:

Type: Total Depth:

Surface Elevation:

Figure:Remarks:

3AField Engineer: Todd Touchard

7.0

10.0

9.0

6' to 8': Silty Clay (CL) with frequent Silty Sand layers

1" to 2" thick. Layers get thicker with depth, saturated medium stiff, grey

8.0

6.0

5.0

3.0

4.0

8" to 4': Silty Clay (CL) with occasional silty sand layers, layers are seams to 1/2" thick , moist, soft ‐ medium stiff, brown

W A

TE

R L

EV

EL

S

TA

B

LE

Li q u id L im it

D

EP

TH

ft

1.0

2.0

0‐8": Topsoil w/ silty clay and sands, organics, roots, loose

Date:

Test Pit Log

Soil Description

P as si n g #2 S ie ve

B lo w s/ ft

9.5'

N/A Water Elevation Initial: 6'

Grab Sample

G R A P H

IC

L O G

W A

TE

R L

EV

EL

IN

IT

IA

L

SA

M P

LE

Shear Strength, TSF

6'

Unconfined Comp (UU)

Miniature Vane

4' to 6': Sand with Trace Silt (SP), saturated, medium dense, brown

8' to 9.5': Sandy Gravel (GP), 8‐inch minus gravel, saturated, loose, grey

End at 9.5' stopped excavating due to sidewall caving

Pocket Pentrometer

Residual Mini Vane

29‐Jan‐14

TP-1Duchesne Bunkhouse

P la st ic L im it

M o is tu re

0.1" 0.2"

Water Depth Final:

CBR

1.0 2.0 Field Vane

Surface Elevation:

3.5' to 7.5': Sandy Gravel with Trace Silt (GP), 4‐inch minus gravel, saturated, loose, brown

Figure:

3BField Engineer: Todd Touchard

Remarks:

9.0

10.0

End at 7.5' stopped excavating due to sidewall caving and gravel sloughing

7.0

8.0

6.0

5.0

4.0

3.0

2.0

0‐8": Topsoil w/ silty clay and sands, organics, roots, loose

1.0 8" to 3.5': Silty Sand with occasional silty clay layers, layers are 1/2" to 2" thick , moist, soft ‐ medium stiff, brown

Pocket Pentrometer

0.1" 0.2" Unconfined Comp (UU)

Field Vane

1.0 2.0B lo w s/ ft

Li q u id L im it

P la st ic L im it

M o is tu re

Shear Strength, TSF

CBR

Miniature Vane

Residual Mini Vane

D

EP

TH

ft

G R A P H

IC

L O G

W A

TE

R L

EV

EL

IN

IT

IA

L

W A

TE

R L

EV

EL

S

TA

B

LE

SA

M P

LE

Soil Description

P as si n g #2 S ie ve

Water Elevation Initial: 5'

Water Depth Final: 5'

Date: 29‐Jan‐14

TP-2Duchesne Bunkhouse

Test Pit Log Grab Sample 7.5'

N/A

Surface Elevation:

0‐6": Topsoil w/ silty clay and sands, organics, roots, loose

3' to 4': Silty Clay (CL), saturated, soft, brown

Figure:

3CField Engineer: Todd Touchard

Remarks:

9.0

10.0

End at 7' stopped excavating due to sidewall caving

7.0

8.0

6.0 5.5' to 7': Silty Sand (SM) , fine to medium sand, saturated loose, grey

5.0

4.0

4' to 5.5': Sand (SP), medium to coarse sand, saturated, medium dense, brown, rust mottling changes to grey at 5'

3.0

2.0

1.0 6" to 3': Silty Sand (SM), fine to medium sand, moist, medium dense, brown

Pocket Pentrometer

0.1" 0.2" Unconfined Comp (UU)

Field Vane

1.0 2.0B lo w s/ ft

Li q u id L im it

P la st ic L im it

M o is tu re

Shear Strength, TSF

CBR

Miniature Vane

Residual Mini Vane

D

EP

TH

ft

G R A P H

IC

L O G

W A

TE

R L

EV

EL

IN

IT

IA

L

W A

TE

R L

EV

EL

S

TA

B

LE

SA

M P

LE

Soil Description

P as si n g #2 S ie ve

Water Elevation Initial: 5'

Water Depth Final: 5'

Date: 29‐Jan‐14

TP-3Duchesne Bunkhouse

Test Pit Log Grab Sample 7'

Surface Elevation:

2' to 3': Silty Clay (CL), saturated, soft, brown

5' to 7': Silty Clay (CL) with frequent layers of silty sand, 1/2" to 2" thick, saturated, soft, grey, rust

7' to 9.5': Sandy Gravel with Trace Silt (GP), 4‐inch minus gravel, saturated, loose, grey

Remarks: Figure:

3DField Engineer: Todd Touchard

9.0

10.0 End at 9.5' stopped excavating due to sidewall

caving

8.0

7.0

5.0

6.0

4.0

3.0

3' to 5': Silty Sand (SM), fine to medium sand, saturated, medium dense, brown

2.0

0‐6": Topsoil w/ silty clay and sands, organics, roots, loose

1.0 6" to 2': Silty Sand (SM), fine to medium sand, moist, medium dense, brown

Pocket Pentrometer

0.1" 0.2" Unconfined Comp (UU)

Field Vane

1.0 2.0B lo w s/ ft

Li q u id L im it

P la st ic L im it

M o is tu re

Shear Strength, TSF

CBR

Miniature Vane

Residual Mini Vane

D

EP

TH

ft

G R A P H

IC

L O G

W A

TE

R L

EV

EL

IN

IT

IA

L

W A

TE

R L

EV

EL

S

TA

B

LE

SA

M P

LE

Soil Description

P as si n g #2 S ie ve

Water Elevation Initial: 8'

Water Depth Final: 8'

Date: 29‐Jan‐14

TP-4Duchesne Bunkhouse

Test Pit Log Grab Sample 9.5'

Pocket Penetrometer

0.25 ‐ 0.5

1.0 ‐ 2.0

2.0 ‐ 4.0

Layer 1/2 ‐ 12" foot of thickness

Hard

Very Stiff

8 ‐ 15

4 ‐ 8

15 ‐ 30

Firm

Stiff

Indented with difficulty by thumbnail

Easily penetrated 1" by thumb. Molded by light finger pressure

Penetrated over 1/2" by thumb with slight effort. Molded by strong finger pressure

0.125 ‐ 0.25

0.5 ‐ 1.0

Soft

>2.0

Frequent

Occasional one or less per foot of thickness

2 ‐ 4

Thin Wall Tube

Rock Core

No Recovery

Torvane

Undrained shear strength (tsf)

Field Test

Indented about 1/2" by thumb but penetrated only with great effort

Readily indented by thumbnail

0.25 ‐ 0.5

0.5 ‐ 1.0

1.0 ‐ 2.0

>4.0>30

Easily penetrated several inches by thumb. Squeezes through fingers

Unconfined compressive strength (tsf)

<2

Fi gu re 4

Thickness

Will not crumble or break with finger pressure

Log Key Symbols Water level

(after completion)

2" Ø Penetration

Split Spoon Sampler

(where first encountered)

Stratification

Standard

Penetration Split

Spoon Sampler

Strongly

Bulk/ Bag Sample

Water level

Description

1/16 ‐ 1/2"Seam

Coarse Grained Soils

<4

4.) No warranty is provided as to the continuity of soil conditions between individual sample locations.

Very Loose

>30 Use Modifier

Fine Grained Soils

Very Soft <0.125

30 ‐ 50

0 ‐ 15

Dense

Loose

Consistency SPT (blows/ft)

<0.25

Difficult to penetrate a foot with 1/2" reinforcing rod driven by a 5 lb. hammer65 ‐ 85

35 ‐ 65

85 ‐ 100Very Dense

Easily penetrated a foot with 1/2" reinforcing rod driven by a 5 lb. hammer10 ‐ 30

Penetrated only a few inches with 1/2" reinforcing rod driven by a 5 lb. hammer

Medium Dense

>50

15 ‐ 35

Apparent Density SPT (blows/ft) Relative Density

Difficult to penetrate with 1/2" reinforcing rod pushed by hand4 ‐ 10

Field Test

Easily penetrated with 1/2" reinforcing rod pushed by hand

Crumbles or breaks with considerable finger pressureModerately

Inorganic silts and very fine sands, rock flour, silty or clayey fine sand with slight plasticity

SP

Slight to Medium

ML

CL

OL

None

Medium

Weakly>12 Description:

Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays

Crumbles or breaks with handling of slight finger pressure

Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts

Trace

2.) All sieve sizes on this chart are U.S. standard.

General Notes

Coarse‐Grained soils with 5 to 12 % fines require dual symbols

Predominantly one size of a range of sizes with some intermediate sizes missing.

(The No. 200 sieve size is about the smallest particle visible to the naked eye)

None to Very Slow

Slight to Medium

Slight to Medium

Silty sands, poorly graded sand‐silt mixtures

SC(appreciable amount of fines)

GM

Clayey gravels, poorly graded gravel‐sand‐ clay mixtures

Clayey sands, poorly graded sand‐clay mixtures

Organic clays of medium to high plasticity

Inorganic clays of high plasticity, fat clays

Organic silts and organic silt‐class of low plasticity

MH

High

(little or no fines)

Liquid limit greater than 50

Silts and Clays

Silts and Clays

(for visual classifications the

1/4" size may be used as equivalent to the No. 4 sieve size

SM

None to very slow

Liquid limit less than 50

Quick to slow

Slow to none

None to Slight

Slight to Medium

Medium to High

UNIFIED SOIL CLASSIFICATION SYSTEM

FIELD IDENTIFICATION PROEDURES

Graphic

Symbol

Letter

Symbol Typical Descriptions

Gravels

Coarse

Grained Soils

Well graded gravels, gravel‐sand mixtures, little or no fines

Poorly graded gravels, gravel‐sand mixtures, little or no fines

Predominantly one size of a range of sizes with some intermediate sizes missing.

More than half of coarse fraction is larger than a No.

4 sieve size

Non‐plastic fines (for identification procedures see ML below)

Slight

Poorly graded sands, gravelly sands, little or no fines

IDENTIFICATION PROCEDURES ON FRACTION SMALLER THAN NO. 4 SIEVE SIZE

GW

GP

Non‐plastic fines (for identification procedures see ML below)

Plastic fines (for identification procedures see CL below).

Plastic fines (for identification procedures see CL below).

More than half of material is larger than No. 200 sieve size

3.) Logs represent general soil conditions observed at the point of exploration on the date indicated

1.) Boundary Classifications: Soils possessing characteristics of two groups are designated by combinations of group symbols. For example GW‐GC, well graded gravel‐sand mixture with clay binder

Fine Grained

Soils

Slow

High to Very High

Dry strength (Crushing

Characteristics)

Less than half of material is larger than No. 200 sieve size

(The No. 200 sieve size is about the smallest particle visible to the naked eye)

2.) Lines separating strata on the logs represent approximate boundaries only actual transitions may be gradual

Coarse‐Grained Soils

Wet Above optimum moisture content

Description

Fine‐Grained Soils Granular Portion

Very Moist

1.)In general, Unified Soil Classification Designation presented on the logs were evaluated by visual methods only. Therefore, actual designations (based on laboratory testing) may differ. Damp, no visible water; at or near optimum moisture

With

Description %

5 ‐1215 ‐ 30

Toughness (Consistency near plastic limit)

(for visual classifications the

1/4" size may be used as equivalent to the No. 4 sieve size

Sands

(little or no fines)

SW

Well graded sands, gravelly sands, little or no fines

Clean Gravels

Silty Gravels, poorly graded gravel‐sand‐silt mixtures.

Wide range of grain size and substantial amounts of all intermediate particle sizes.

Clean Sands

More than half of coarse fraction is smaller than a

No. 4 sieve size

Sands with Fines

GC

Gravel with Fines

(appreciable amount of fines)

Dilatancy (Reaction to shaking)

Wide range of grain size and substantial amounts of all intermediate particle sizes.

High Organic Soils

Criteria

Description: Criteria Dry Absence of moisture, dusty, dry to the touch

Cementation

Slightly Moist Moist

>15

5 ‐ 15 0 ‐ 5

%% Description oratory testing) may differ.

Use Modifier

5 ‐ 15

With With

TraceTrace

Apparent Moisture, but below optimum moisture content

None

Granular Portion Fine Grained Portion

Moisture Content

Peat and other highly organic soilsPT

Modifiers

OH

CH

Medium to High