The
dilatancy of specimens was caused by the particles in the upper and lower parts of the model moving to the middle and the particles in the middle of the model moving outward, and the numerical triaxial test can better reproduce the triaxial compression process.
When coal-rock mass experiences
dilatancy due to its strength or stiffness degradation as damage evolves, its hydraulic property would also change.
[19] measured such
dilatancy peak on plastisols at intermediate shear rates.
During compression in different confining pressure, the volume strain is always characterizes negative and positive
dilatancy. The responding experimental results are revealed in Fig.
Therefore some researchers use an intangible parameters as for example the effective friction coefficient without
dilatancy between jointed surfaces (Gerrard, 1986).
In addition, there are two parameters, which define the failure criteria (the friction angle, [phi], and cohesion, c) and a
dilatancy angle, [psi], which to describe the flow rule.
where [xi] is the parameter which controls the potential function to approach the asymptote, [[alpha].sub.p] is the
dilatancy parameter, and [f.sub.t0] is the maximum uniaxial tensile strength of the material.