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Building Design and Construction Handbook - Merritt - Ventech!

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6.37<br />

TABLE 6.10 Soil Classification for Organic Soil<br />

Major<br />

divisions<br />

Organic matter<br />

Highly organic<br />

soils<br />

Organic soils<br />

Slightly<br />

organic soils<br />

Organic<br />

content<br />

75 to 100%<br />

Organics<br />

(Either<br />

visible or<br />

inferred)<br />

30 to 75%<br />

Organics<br />

(Either<br />

visible or<br />

inferred)<br />

5to30%<br />

organics<br />

(Either<br />

visible or<br />

inferred)<br />

Less than<br />

5%<br />

organics<br />

USCS<br />

symbol Typical names<br />

PT<br />

Fibrous peat<br />

(woody,<br />

mats, etc.)<br />

PT<br />

PT<br />

PT<br />

OH<br />

OL<br />

Use Table<br />

6.8<br />

Fine-grained<br />

peat<br />

(amorphous)<br />

Silty peat<br />

S<strong>and</strong>y peat<br />

Clayey organic<br />

Silt<br />

Organic s<strong>and</strong><br />

or Silt<br />

Soil with<br />

slight<br />

organic<br />

fraction<br />

Distinguishing characteristics for<br />

visual identification Typical range of laboratory test results<br />

Light weight <strong>and</strong> spongy.<br />

Shrinks considerably on air<br />

drying. Much water squeezes<br />

from sample.<br />

Light weight <strong>and</strong> spongy.<br />

Shrinks considerably on air<br />

drying. Much water squeezes<br />

from sample.<br />

Relatively light weight, spongy.<br />

Shrinks on air drying.<br />

Usually can readily squeeze<br />

water from sample.<br />

S<strong>and</strong> fraction visible. Shrinks<br />

on air drying. Often a<br />

‘‘gritty’’ texture. Usually can<br />

squeeze water from sample.<br />

Often has strong hydrogen<br />

sulfide (H2S) odor. Medium<br />

dry strength <strong>and</strong> slow<br />

dilatency.<br />

Threads weak <strong>and</strong> friable near<br />

plastic limit, or will not roll<br />

at all. Low dry strength,<br />

medium to high dilatency.<br />

Depends on the characteristics<br />

of the inorganic fraction.<br />

Source: NAVFAC DM-7.1, 1982, based on unpublished work by Ayers <strong>and</strong> Plum.<br />

Notes: w � in-situ water content, PI � plasticity index, NP � nonplastic, �t � total unit weight, G � specific<br />

gravity (soil minerals plus organic matter), Cc � compression index, eo � initial void ratio, <strong>and</strong> Cc /(1� eo) � modified<br />

compression index.<br />

w � 500 to 1200%<br />

�t � 9.4 to 11 kN/m 3 (60 to 70 pcf)<br />

G � 1.2 to 1.8<br />

Cc/(1 � eo) � 0.40<br />

w � 400 to 800% PI � 200 to 500<br />

�t � 9.4 to 11 kN/m 3 (60 to 70 pcf)<br />

G � 1.2 to 1.8<br />

Cc/(1 � eo) � 0.35<br />

w � 250 to 500% PI � 150 to 350<br />

�t � 10 to 14 kN/m 3 (65 to 90 pcf)<br />

G � 1.8 to 2.3<br />

Cc/(1 � eo) � 0.3 to 0.4<br />

w � 100 to 400% PI � 50 to 150<br />

�t � 11 to 16 kN/m 3 (70 to 100 pcf)<br />

G � 1.8 to 2.4<br />

Cc/(1 � eo) � 0.2 to 0.3<br />

w � 65 to 200% PI � 50 to 150<br />

�t � 11 to 16 kN/m 3 (70 to 100 pcf)<br />

G � 2.3 to 2.6<br />

Cc/(1 � eo) � 0.2 to 0.35<br />

w � 30 to 125% PI � NP to 40<br />

�t � 14 to 17 kN/m 3 (90 to 110 pcf)<br />

G � 2.4 to 2.6<br />

Cc/(1 � eo) � 0.1 to 0.25<br />

Depends on the characteristics of the<br />

inorganic fraction.

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