Environmental Engineering Reference
In-Depth Information
TABLE 5.37
Identification of Fine-Grained Soil Fractions from Manual Test
a
Material
Dry Strength
Dilatency
Toughness of Plastic
Plasticity
Reaction
Thread
Description
Sandy silt
None-very low
Rapid
Weak, soft
None-low
Silt
Very low-low
Rapid
Weak, soft
None-low
Clayey slit
Low-medium
Rapid-slow
Medium stiff
Slight-medium
Sandy clay
Low-high
Slow-none
Medium stiff
Slight-medium
Silty clay
Medium-high
Slow-none
Medium stiff
Slight-medium
Clay
High-very high
None
Very stiff
High
Organic silt
Low-medium
Slow
Weak, soft
Slight
Organic day
Medium-very high
None
Medium stiff
Medium-high
a
From ASTM D2488. Reprinted with permission. Copyright ASTM.
TABLE 5.38
Soil Identification: Elements of Field Descriptions
Elements
Importance
Description
Gradation
Components
See
Table 5.36
Grain shape
Strength
Rounded, subrounded, subangular, angular
Mineral constituents
Strength
From Table 0.5
Color
Provides information
Tone: Function of soil moisture; the wetter the deeper
on soil minerals
the color
and environment
Red, yellow, brown: Good drainage and aerations
Deep reds: Indicate iron oxides
Pale yellow, yellow browns: Hydrated iron oxides
Bluish gray: Reduced bivalent iron compound, poor
drainage and aerobic conditions
Light grays: Due to leaching
Mottled colors: Restricted permeability, or poor drainage
and aeration
Black, dark brown, or gray: Organic soils: or caused by
dark minerals
(manganese, titanium, magnetite)
Green: Glauconite (hydrous silicate, K and Fe)
White: Silica, lime, gypsum, kaolin clay
Compactness
in situ
Compressibility
From SPT (see
Table 3.23)
or visual estimate
of granular soils
Consistency
in situ
Strength of clay soils
From hand test or SPT (
see
Table
3.27)
Field moisture
Estimate GWL depth
From sample appearance: Dry, moist, wet (saturated)
Homogeneity
Permeability
Fabric or structure: Terms not universally defined
estimates
Homogeneous: Without stratification: uniform fabric
(
k
h
vs.
k
v
)
Stratified: Partings — very fine, barely visible, form
weakness planes
Lenses—from very fine to 5 mm
Seams—5 mm to 2 cm
Layers—
2 cm
Varves—interbedded seams
Pockets: Foreign irregularly shaped mass in matrix
Heterogeneous: very irregular, without definite form
Cementation
Strength
Reaction with dilute HCl: None, weak, strong
Note:
Example: “Medium compact, tan, silly coarse to fine sand (subrounded, quartz, with some shell frag-
ments) with lenses and seams of dark gray silt: moist.”
