Volume Change Testing
Volume Change Coefficients or Indices
The parameters required for constitutive equations relating
deformation state variables and stress state variables.
Table 1 - Volume Change
Derivation of Relationships for Volume Change
Requirements for Volume Change Theory
Representation of deformation behavior requires constitutive
equations relating a deformation state variable relate
Unsaturated Soil Shear Strength Parameters Measurements
Control of Stress States
The stresses , ua and uw can be measured or controlled so
that the stress state variables ( - ua), (1 - 3) and
(ua - u
Shear Strength of Unsaturated Soil
Shear Strength Characterization
Requirements for Shear Strength
Cannot use saturated soil parameters c' and ' and
effective stresses because effective stresses are
Unsaturated Flow
Derivation of Governing Equations
Description of Mass Balance Consideration
Derivation of governing differential equation is obtained
by considering a volumetric element.
The stateme
Measurement of Unsaturated Permeability
Water Coefficient of Permeability
Direct Permeability Methods
1) Steady State Methods
Principle:
Under steady state conditions, i.e., (ua - uw) = constant,
the
Flow in Unsaturated Soil
Requirements for Flow Laws
Requires a law relating the diffusion or flow rate with the
driving potential.
For diffusion, the driving potential is either due to a
chemical, th
Soil Suction
Total Suction
Total soil suction is defined in terms of the free energy or the
relative vapor pressure (relative humidity) of the soil
moisture.
=
RT
v
w0
ln (
v
u
u
v
)
v0
u v = partia
Stress State Variables
Definition
Stress variables are used to determine the state of stress in a
soil that is then used to model mechanical behavior.
These stress state variables cannot be dependent
Phase Relationships
Phase Properties
Density
= M / V = mass per unit volume
= s(soil), w(water) or a(air)
Specific volume
v0 = V / M
Ideal gas law (for moist and dry air)
u V = (M / ) R T
u = abso
Mechanics of Unsaturated Soils
1. Introduction
Course Text
Soil Mechanics for Unsaturated Soils by D. G. Fredlund
and H. Rahardjo
Course Description
Course emphasizes topics related to the mechanics