shearing resistance which a soil can mobilize and the compressibility of
clay soils (equations (2.6) and (2.7)).
Representative physical data from samples of common soil types are
presented in Table 2.1. Water contents are expressed as percentages of the
dry mass; the void ratio, e, and degree of saturation, Sr, are defined in
accordance with standard soil mechanics terminology and expressed in
volume terms.
2.3 Engineering characteristics of soils2.3.1 Soil load responseSoil response is important in embankment dam construction with respect
to the performance of engineered compacted soils in earthfills and that of
the natural underlying foundation soils.
In earthfill construction it is necessary to consider the load-bearing
characteristics of the compacted fill and also the behaviour of the soil as
construction proceeds. It is convenient to categorize problems concerning
the response of soils to specific loading conditions as problems of stability or
of deformation. Problems of stability concern the equilibrium between
forces and moments and the mobilized soil strength. When the former,
arising from loading (or from the removal of support as in a trench excava-
tion), exceed the shearing resistance which the soil can mobilize, failure will
occur. This is generally manifested by progressive and, in the final phase,
large and relatively rapid mass displacements, e.g. of a soil slope. Stability
problems involve concepts of soil shear strength and stress–strain response.
ENGINEERING CHARACTERISTICS OF SOILS 47
Table 2.1 Representative physical characteristics of soils
Soil type Natural In situ unit Void Degree of
water weight, (kN m^3 ) ratio, saturation Sr
content, e(see note) (%)
w (%)
Dry uniform sand,
loose 0 13.5 0.95 0
Well-graded sand 5 19.5 0.45 40
Soft clay 55 17.0 1.50 95
Firm clay 20 19.5 0.70 90
Stiff glacial till 10 23.0 0.30 95
Peat and organic
soils 250 10.0 3.50 90
The specific gravity of soil mineral particles, Gs≈2.65–2.75.
ePore void volume relative to volume of matrix solids.