CHARACTERISTICS OF SOILS - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 31

OCR , ageing, chemical processes, and the distinction between unloading and
reloading. These parameters are used in so-called constitutive models, which are
invented to describe soil behaviour, when loaded, in terms of deformation and
failure. A wide variety of constitutive models exists for one-dimensional
swell/compaction or settlement. Generally accepted constitutive and/or rheological
models for multi-dimensional behaviour are Hooke's model (linear elasticity),
Mohr-Coulomb model, CamClay model, Soft-Soil model, Hardening-Soil model,
and Hypoelastic model (see Chapter 9).

application 2.1
What is SMW?
SMW: silty sand well-graded
Estimate I p from Fig 2.2 for soil type CML.
CML: low plasticity silty clay, I p around 7 - 10.

application 2.2
Prove that e ) /v represents the unit weight of saturated soil (see Table 2.1).

Consider a volume V of saturated soil, i.e. V = V s

w ( G s

V p . The pore volume V p is
saturated with water, thus V w = V p . The weight of solids is W s =

s V s = w G s V s and

the weight of pore water is W w = w V p . Together, the total weight is W = W s W w =

e) = v -1 and V p /V = e/ (1 w (G s V s V p ) . With V s /V = 1/(1 e) = e/v , the unit weight

of the saturated soil becomes

= W/V = ( W s W w )/ V = W s (1 w )/ V =

= w ( G s V s V p )/ V = w ( G s V s / V V p / V) = w ( G s e )/ v

By weighing the saturated soil W of a soil sample and determining its total
volume V , and next drying the soil sample in an oven and weighing the solids and
determining their volume by means of a pycnometer, i.e. W s and V s , water content
w , specific gravity G s and specific volume v = 1 e are determined. It is a standard

laboratory test.
The unit weight of semi-saturated soils is se)/v , with s the saturation

degree. Is the standard test sufficient to also calculate the saturation degree, in the
case of semi-saturated soil?

w ( G s

application 2.3
A specific volume of dry sand and water are measured separately and together
after pouring the soil in the water (otherwise trapped air causes a saturation of
about 75%). Data is given in Fig 2.6. The purpose is to determine various soil
properties. Adopt g = 10 m/s 2 and w = 10 kN/m 3 . The particle size distribution

curve gives D 50 = 160 m (fine sand), and U = 1.5 (uniform sand).