Download files
Abstract
A thermo-elastic-plastic model for unsaturated soils has been presented based on the
effective stress principle considering the thermo-mechanical and suction coupling
effects. The thermo-elastic-plastic constitutive equations for stress-strain relations of the
solid skeleton and changes in fluid content and entropy for unsaturated soils have been
established. A plasticity model is derived from energy considerations. The model
derived covers both associative and non-associative flow behaviours and the modified
Cam-Clay is considered as a special case. All model coefficients are identified in terms
of measurable parameters.
To verify the proposed model, an experimental program has been developed. A series of
controlled laboratory tests were carried out on a compacted silt sample using a triaxial
equipment modified for testing unsaturated soils at elevated temperatures. Imageprocessing
technique was used for measuring the volume change of the samples
subjected to mechanical, thermal and hydric loading.
It is shown that the effective critical state parameters M, κ and λ are independent of
temperature and matric suction. Nevertheless, the shape of loading collapse (LC) curve
was affected by temperature and suction. Furthermore, the temperature change affected
the soil water characteristic curve and an increase in temperature caused a decrease in
the air entry suction.
The simulations from the proposed model are compared with the experimental results.
The model calibration was performed to extract the model parameters from the
experimental results. Good agreement between the results predicted using the proposed
model and the experimental results was obtained in all cases.