soil and rock classification1

7/28/2019 Soil and Rock Classification1

http://slidepdf.com/reader/full/soil-and-rock-classification1 1/18

APPENDIX C.

SOIL AND ROCK CLASSIFICATION, SIMPLE TESTS, AND CORRELATIONS

Contents

Page

1. Unified Soil Classification System ................................................................................C-2

2. Gradation Chart for Soils ...............................................................................................C-3

3. Naval Facilities Design Manuals 7.1 and 7.2 excerpts

- Visual Identification of Soil Samples ......................................................................C-4

- Relationships Between Atterberg Limits and Compressibility, Permeability,Toughness, and Dry Strength...................................................................................C-5

- Guide for Consistency of Fine-Grained (Cohesive) Soils .......................................C-6 - Correlations of Standard Penetration Resistance Blow Counts (N Values) and

Unconfined Compressive Strength of Clays............................................................C-7

- Hardness Classification of Intact Rock....................................................................C-8 - Typical Properties of Compacted Soils....................................................................C-9

- Identification and Characteristics of Special Materials .........................................C-10

- Ultimate Friction Factors and Adhesion for Dissimilar Materials.........................C-11

4. Other Correlations and Tests

- Qualitative and Quantitative Expressions for Consistency of Soils ......................C-12

- Relation of Consistency of Clay, Number of Blows N on Sampling Spoon, ........C-13 and Unconfined Compressive Strength

- Relative Density of Sands According to Results of Standard Penetration Test Blow

Counts (N Values)..................................................................................................C-14

- Field Determination of Soil Components ..............................................................C-15 - Identification of Fine-Grained Soil Fractions from Manual Tests.........................C-16

- Identification of Composite Clay Soils on an Overall Plasticity Basis .................C-17

- Representative Values of Friction Angle, φd for Sands and Silts ..........................C-18

C-1

Exit Index Search



C-2

Exit Index Search



C-3

Exit Index Search



VISUAL IDENTIFICATION OF SOIL SAMPLES (NAVFAC DM 7.1, Table2, p7.1-8)

Definitions of Soil Components and Fractions

1. Grain Size

Material Fraction Sieve SizeBoulders 12"+

Cobbles 3"-12"Gravel coarse 3/4"-3"Gravel fine No. 4 to 3/4"

Sand coarse No. 10 to No. 4

Sand medium No. 40 to No. 10Sand fine No. 200 to No. 40

Fines Passing No. 200

(Silt & Clay)

2. Coarse- and Fine-Grained Soils

Descriptive Adjective Percentage Requirements

trace 1-10%little 10-20%

some 20-35%

and 35-50%

3. Fine-Grained Soils. Identify in accordance with plasticity characteristics,

dry strength, and toughness as described in Table 3.

Descriptive

Term Thickness

alternating

thick Stratified thin

Soils with parting 0 to 1/12" thickness

seam 1/16 to 1/2" thickness

layer 1/2 to 12" thickness

stratum greater than 12" thicknessvarved clay alternating seams or layers of sand,

silt and clay

pocket small, erratic deposit, usually lessthan 1 foot

lens lenticular deposit

occasional one or less per foot of thicknessfrequent more than one per foot of thickness

C-4

Exit Index Search



C-5

Exit Index Search



GUIDE FOR CONSISTENCY OF FINE-GRAINED (COHESIVE) SOILS

(NAVFAC DM 7.1, Table 4, p7.1-17)

SPT Estimated Range of

Penetration N Value Unconfined Compressive

(blows/foot) Estimated Consistency Strength (tons/sq ft)

< 2 Very soft Less than 0.25

(extruded between fingers whensqueezed)

2 - 4 Soft 0.25 - 0.50

(molded by light finger pressure)

4 - 8 Medium 0.50 - 1.00

(molded by strong finger pressure)

8 - 15 Stiff 1.00 - 2.00

(readily indented by thumb but

penetrated with great effort)

15 - 30 Very stiff 2.00 - 4.00

(readily indented by thumbnail)

> 30 Hard > 4.00

(indented with difficulty by thumbnail)

C-6

Exit Index Search



C-7

Exit Index Search



HARDNESS CLASSIFICATION OF INTACT ROCK

(NAVFAC DM 7.1, Table 9, p 7.1-27)

Class Hardness Field Test

ApproximateRange of

Uniaxial

CompressionStrength, kg/cm

2

(tons/ft2)

I Extremely hard

Many blows with geologic hammer required

to break intact specimen. > 2000

II Very hard

Hand held specimen breaks with hammer end

of pick under more than one blow. 2000 - 1000

III Hard

Cannot be scraped or peeled with knife, handheld specimen can be broken with single

moderate blow with pick. 1000 - 500

IV Soft

Can just be scraped or peeled with knife.Indentations 1mm to 3mm show in specimen

with moderate blow with pick. 500 - 250

V Very soft

Material crumbles under moderate blow with

sharp end of pick and can be peeled withknife, but is too hard to hand-trim for triaxial

test specimen. 250 - 10

Note: 1 tsf = 1.02 x kg/cm2

1 psi = 13.88 x tsf

C-8

Exit Index Search



IDENTIFICATION AND CHARACTERISTICS

OF SPECIAL MATERIALS


Material

Geographic/Geomorphic

Features Engineering Conditions

"Quick Clay"

Marine or brackish water claycomposed of glacial rock flour that

is elevated above sea level.

Severe loss of strength when disturbed byconstruction activities or seismic ground

shaking.

Generally confined to far northareas; Eastern Canada, Alaska,

Scandinavia.

Replacement of formation water containing dissolved salt with fresh water

results in strength loss.

Produces landslide prone areas(Anchorage, Alaska).

Hydraulic

Fills

Coastal facilities, levees, dikes,

tailings dams.

High void ratio.

Uniform gradation but variable grain sizes

within same fill.

High liquefaction potential.

Lateral spreading

Easily eroded.

Collapsing

Soil

Desert arid and semi-arid

environment.

Loss of strength when wetted.

Differential settlement.

Alluvial valleys, playas, loess.

Low density.

Moisture sensitive.

Gypsum/Anhydrite often present.

C-10

Exit Index Search



ULTIMATE FRICTION FACTORS AND

ADHESION FOR DISSIMILAR MATERIALS


Interface MaterialsFriction

factor

Friction

angle,

degrees

Mass concrete on the following foundation materials:

Clean sound rock 0.70 35

Clean gravel, gravel-sand mixtures, coarse sand 0.55 to 0.60 29 to 31

Clean fine to medium sand, silty medium to coarse sand, silty or clayey gravel 0.45 to 0.55 24 to 29

Clean fine sand, silty or clayey fine to medium sand 0.35 to .045 19 to 24

Fine sandy silt, non-plastic silt 0.30 to 0.35 17 to 19

Very stiff and hard residual or pre-consolidated clay 0.40 to 0.50 22 to 26

Medium stiff and stiff clay and silty clay 0.30 to 0.35 17 to 19

(Masonry on foundation materials has same friction factors.)

Steel sheet piles against the following soils:

Clean gravel, gravel-sand mixtures, well-graded rock fill with spalls 0.40 22

Clean sand, silty sand-gravel mixture, single size hard rock fill 0.30 17

Silty sand, gravel or sand mixed with silt or clay 0.25 14

Fine sandy silt, non-plastic silt 0.20 11

Formed concrete or concrete sheet piling against the following soils:

Clean gravel, gravel-sand mixtures, well-graded rock fill with spalls 0.40 to 0.50 22 to 26

Clean sand, silty sand-gravel mixture, single size hard rock fill 0.30 to 0.40 17 to 22

Silty sand, gravel or sand mixed with silt or clay 0.30 17

Fine sandy silt, non-plastic silt 0.25 14

Various structural materials:

Masonry on masonry, igneous and metamorphic rocks:

Dressed soft rock on dressed soft rock 0.70 35

Dressed hard rock on dressed soft rock 0.65 33Dressed hard rock on dressed hard rock 0.55 29

Masonry on wood (cross grain) 0.50 26

Steel on steel at sheet pile interlocks 0.30 17

Interface Materials (Cohesion) Adhesion Ca (psf)

Very soft cohesive soil (0 - 250 psf) 0 - 250

Soft cohesive soil (250 - 500 psf) 250 - 500

Medium stiff cohesive soil (500 - 1000 psf) 500 - 750

Stiff cohesive soil (1000 - 2000 psf) 750 - 950

Very stiff cohesive soil (2000 - 4000 psf) 950 - 1,300

C-11

Exit Index Search



QUALITATIVE AND QUANTITATIVE EXPRESSIONS FOR CONSISTENCY

Unconfined Compressive

Consistency Field Identification Strength qu

(tons/sq ft)

Very Soft Easily pentrated several inches by fist Less than 0.25

Soft Easily pentrated several inches by thumb 0.25-0.5

MediumCan be penetrated several inches by thumbwith moderate effort 0.5-1.0

Stiff

Readily indented by thumb but penetrated

only with great effort 1.0-2.0

Very Stiff Readily indented by thumbnail 2.0-4.0

Hard Indented with difficulty by thumbnail Over 4.0

C-12

Exit Index Search



RELATION OF CONSISTENCY OF CLAY, NUMBER

OF BLOWS (N VALUE), AND

UNCONFINED COMPRESSIVE STRENGTH

Very Very

Consistency Soft Soft Medium Stiff Stiff Hard

N < 2 2-4 4-8 8-15 15-30 > 30

qu < 0.25 0.25-0.50 0.50-1.00 1.00-2.00 2.00-4.00 > 4.0

C-13

Exit Index Search



RELATIVE DENSITY OF SANDS ACCORDING TO

RESULTS OF STANDARD PENETRATION TEST

No. of Blows N Relative Density

0-4 Very loose

4-10 Loose

10-30 Medium

30-50 Dense

Over 50 Very dense

C-14

Exit Index Search



FIELD DETERMINATION OF SOIL COMPONENTS (SEE ALSO ASTM D2488)

Component Characteristic Determination

Gravel Dia. 5-76 mm Measurable.

Sand

Coarse Dia. 2-5 mm Visible to eye, measurable.

Medium Dia. 0.4-2.0 mm Visible to eye.

Fine Dia. 0.074-0.4 mm Barely discernible to unaided eye.

Silt coarse Dia. 0.02 - 0.074 mm Distinguishable with hand lens.

Sand-silt mixtures Apparent cohesion Measured by ball test (Burmister, 1949)

Form ball in hand by compacting moist soil to

diameter 1 1/2 in (37 mm).

Medium to fine sand forms weak ball with

difficulty; cannot be picked up between thumb

and forefinger without crushing.

Ball can be picked up with difficulty: 20% silt.

Ball readily picked up: 30 to 50% silt.

Silt vs. clay Dia. <0.074 mm

Silt Strength Low when air-dried, crumbles easily.

Dilantency test

Mixed with water to thick past consistency.

Appears wet and shiny when shaken in palm of hand, but when palm is cupped and sample

squeezed, surface immediately dulls and dries.

C-15

Exit Index Search



IDENTIFICATION OF FINE-GRAINED SOIL FRACTIONS FROM MANUAL TESTS

Dry Dilantancy Toughness of Time to Settle in

Soil Classification Strength Reaction Plastic Thread Dispersion Test

(Crush in Hand) (Wet Shake) (Ribbon Test) (Hydrometer)

Sandy silt None to very low Rapid Weak to friable 30 sec to 60 min

Silt Very low to low Rapid Weak to friable 15 to 60 min

Clayey silt Low to medium Rapid to slow Medium 15 min to several hours

Sandy clay Low to high Slow to none Medium 30 sec to several hours

Silty clay Medium to high Slow to none Medium 15 min to several hours

Clay High to very high None Tough Several hours to days

Organic silt Low to medium Slow Weak to friable 15 min to several hours

Organic clay Medium to very high None Tough Several hours to days

C-16

Exit Index Search



IDENTIFICATION OF COMPOSITE CLAY SOILS ON AN

OVERALL PLASTICITY BASIS*

Degree of Overall Identification Smallest Diameter of

Plasticity PI (Burmister system) Rolled Threads, mm

Non-plastic 0 SILT None

Slight 1-5 CLAYEY SILT 6

Low 5-10 SILT and CLAY 3

Medium 10-20 CLAY and SILT 1.5

High 20-40 SILTY CLAY 0.8

Very high > 40 CLAY 0.4

*After Burmister (1951a), Reprinted with permission from the Annual Book of ASTM

Standards, Part 19, copyright, American Society for Testing and Materials.

C-17

Exit Index Search



REPRESENTATIVE VALUES OF φd FOR SANDS AND SILTS

φd - Degrees

Material Loose Dense

N < 10 N > 30

Sand, round grains, uniform 27.5 34

Sand, angular grains, well-graded 33 45

Sandy gravel 35 50

Silty sand 27-33 30-35

Inorganic silt 27-30 30-34

C-18

Exit Index Search

soil and rock classification1

Documents