Environmental Engineering Reference
In-Depth Information
Characteristics
Granular soils: gradation, relative density, grain shape, and mineral composition
●
Clay soils: mineral type, chemistry, plasticity, and stress history
●
Organic materials: percentage of organic matter vs. soil particles, and stress history
●
Mixtures: combine the characteristics, but relative density quickly becomes
insignificant
●
A general summary of the engineering properties of the various soil groups is given in
Table 5.31.
Gravels and Sands
Hydraulic Properties
Permeability
: Gravels and sands are free-draining materials with large storage capacity,
acting as aquifers or natural reservoirs, providing the sources of water flowing into exca-
vations, or through, around, and beneath dams.
TABLE 5.31
Engineering Properties of Soils Summarized
Property
Gravel and Sand
Silt
Clay
Organics
Hydraulic Properties
Permeability
Very high to high
Low
Very low to
Very high to very low
impermeable
Capillarity
Negligible
High
Very high
Low to high
Frost-heaving
Nil to low
High
High
Low to high
susceptibility
Liquefaction
Nil to high in fine
High
None
High in organic silts
susceptibility
sands
Rupture Strength
Derivation
Intergranular friction
φ
Friction
φ
,
Drained:
φ
and
c
;
Organic silts and clay,
apparent
undrained:
s
u
φ
and
c
cohesion
Relative strength
High to moderate
Moderate to low High to very low
Very low
Sensitivity
None
None
Low to very high
As for clay
Collapsing formations
Lightly cemented sands Loess
Porous clays
Not applicable
Deformability
Magnitude (moderate
Low to moderate
Moderate
Moderate to high
Very high
loads)
Time delay
None
Slight
Long
None to long
Compactability
Excellent
Very difficult
Moderate difficulty Not applicable
requires careful
moisture control
Expansion by wetting
None
None
Moderate to very
Slight
high
Shrinkage upon drying
None
Slight
Moderate to very
High to very high
high
Corrosivity
Occasional:
Occasional
Low to high
High to very high
calcareous sands
troublesome to concrete
