Table A-1 <br />Terminology Used to Describe Soil <br /> 1 of 2 <br />Soil Descriptions <br />Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based on <br />total dry weight, is the primary soil type and is capitalized in our log descriptions (SAND, GRAVEL, SILT, or CLAY). Smaller <br />percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the <br />ASTM D2488-06 Visual-Manual Procedure. <br />may have been followed. In accordance with ASTM D2488-06, group symbols (such as GP or CH) are applied on the portion of <br />soil passing the 3-inch (75mm) sieve based on visual examination. The following describes the use of soil names and modifying <br />terms used to describe fine- and coarse-grained soils. <br />Fine-Grained Soils (50% or greater fines passing 0.075 mm, No. 200 sieve) <br />The primary soil type, i.e., SILT or CLAY is designated through visual-manual procedures to evaluate soil toughness, dilatency, <br />dry strength, and plasticity. The following outlines the terminology used to describe fine-grained soils, and varies from ASTM <br />D2488 terminology in the use of some common terms. <br />Plasticity Plasticity <br />Primary soil NAME, Symbols, and Adjectives <br />Description Index (PI) <br />SILT (ML & MH) CLAY (CL & CH) ORGANIC SOIL (OL & OH) <br />SILT Organic SILT Non-plastic 0 3 <br />SILT Organic SILT Low plasticity 4 10 <br />SILT/Elastic SILT Lean CLAY Organic SILT/ Organic CLAY Medium Plasticity 10 20 <br />Elastic SILT Lean/Fat CLAY Organic CLAY High Plasticity 20 40 <br />Elastic SILT Fat CLAY Organic CLAY Very Plastic >40 <br />Modifying terms describing secondary constituents, estimated to 5 percent increments, are applied as follows: <br />Description % Composition <br /> <br />With Sand <br />15% to 25% plus No. 200 <br />% Sand < % Gravel <br />With Gravel <br /> <br />Sandy <br />30% to 50% plus No. 200 <br />Gravelly % Sand < % Gravel <br />Borderline Symbols, for example CH/MH, are used when soils are not distinctly in one category or when variable soil <br />units contain more than one soil type. Dual Symbols, for example CL-ML, are used when two symbols are required in <br />accordance with ASTM D2488. <br />Soil Consistency terms are applied to fine-grained, plastic soils (i.e., PI > 7). Descriptive terms are based on direct <br />measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84, as follows. SILT soils <br />with low to non-plastic behavior (i.e., PI < 7) may be classified using relative density. <br />Consistency Unconfined Compressive Strength <br />SPT N-value <br />Term tsf kPa <br />Very soft Less than 2 Less than 0.25 Less than 24 <br />Soft 2 4 0.25 0.5 24 48 <br />Medium stiff 5 8 0.5 1.0 48 96 <br />Stiff 9 15 1.0 2.0 96 192 <br />Very stiff 16 30 2.0 4.0 192 383 <br />Hard Over 30 Over 4.0 Over 383 <br />