A Generalised Plastic Model for Gravelly Soils Considering Evolution of Void Ratio and Particle Breakage

Gravelly soils exhibit complicated mechanical behaviours closely related to particle breakage and relative density state. To better capture the mechanical responses of gravelly soils, a generalised plastic model considering evolution of void ratio and particle breakage was developed within the framework of critical state soil mechanics. In the model, particle breakage effect was described by incorporating breakage index to deviate the critical state line off the ideal position. A differential equation relating increment of void ratio to variation of volumetric strain was used to depict the evolution of current void ratio. It indirectly reflected the relative density state of gravelly soils. The model was applied to conducting numerical simulations for a series of triaxial tests on four types of gravelly soils. Comparisons between the test data and the modelling results indicated that considerations of void ratio evolution and particle breakage could better simulate the stress-dependent dilatation/contraction behaviours of gravelly soils.

Internal erosion of gravelly mudstone due to drying/wetting and hydraulic pressure cycles in oedometer test.

When disintegrated mudstone due to the slaking, subjected to hydraulic pressure, could lead to internal erosion. To examine the combined effects of slaking and internal erosion of gravelly mudstone in 1D deformation under a constant vertical load, a series of modified oedometer tests and laboratory penetration tests were conducted with drying/wetting and hydraulic pressure cycles. Some loading conditions showed the sever erosion in progressing of the cycle, susceptibility of the internal erosion was evaluated in terms of non-filter and fitter factors coefficient Keywords: Vertical strain, Slaking, Internal-erosion, Particle-breakage.