The influences of temperature on the mechanical behavior of saturated clays are discussed first. Based on the concept of true strength and the revised calculation method of the potential failure stress ratio,the equation of the critical state stress ratio for saturated clays under different temperatures is deduced. Temperature is introduced as a variable into the UH model (3-dimensional elastoplastic model for overconsolidated clays adopting unified hardening parameter) proposed by Yao et al. and then the UH model considering temperature effects is proposed. By means of the transformed stress method proposed by Yao et al.,the proposed model can be applied conveniently to 3-dimensional stress states. The strain-hardening,softening and dilatancy behavior of overconsolidated clays at a given temperature can be described using the proposed model,and the volume change behavior caused by heating can also be predicted. Compared with the modified Cam-clay model,the proposed model requires only one additional parameter to consider the behavior of the decrease of preconsolidation pressure with an increase of temperature. At room temperature,the proposed model can be changed into the original UH model and the modified Cam-clay model for overconsolidated clays and normally consolidated clays,respectively. The considered temperature range here is from the melting point to the boiling point of the pore water (e.g. the experimental temperatures (20°C–95°C) mentioned in this paper are within this range). Comparison with existing test results shows that the model can reasonably describe the basic mechanical behavior of overconsolidated clays under various temperature paths.
A biaxial shearing test on granular materials is numerically simulated by distinct element method (DEM). The evolution of the microstructures of granular materials during isotropic compression and shearing is investigated, on which a yield function is derived. The new yield function has a similar form as the one used in the modified Cam-clay model and explains the yield characteristics of granular materials under the isotropic compression and shear process through the change of the contact distribution N(θ) defining the contacts at particle contact angle θ.
LIU SiHongYAO YangPingSUN QiChengLI TieJunLIU MinZhi
