3种胶结岩土材料本构模型中破损规律的离散元验证

Numerical evaluation of degradation evolutions in three constitutive models for bonded geomaterials by distinct element method

采用离散元法(DEM)对胶结岩土材料本构模型中的破损规律进行验证。首先,根据胶结颗粒间胶结特性,建立适用于胶结颗粒的微观理论;其次,基于该微观理论,给出3种经典胶结岩土材料本构模型破损参数的微观解释;最后,对数值试样进行等向压缩、等应力比压缩及双轴压缩试验的离散元数值模拟,并对比验证数值试样破损规律的模拟结果与本构模型的预测结果。结果表明:采用DEM对胶结岩土材料本构模型的破损规律进行验证是可行的。3种加载条件下,扰动状态模型假定的破损规律同模拟结果均较为一致;Nova模型在双轴压缩试验条件下的预测结果同模拟结果存在很大差异;而上负荷面剑桥模型假设的破损参数则不能很好描述上述加载条件下数值试样的破损规律。

An evaluation of the degradation evolutions in three constitutive models for bonded geomaterials is presented by means of the distinct element method （DEM）. The models examined are the disturbed state constitutive model （DSC）, superloading yield surface model and Nova＇s model. First, the micromechanics theory for bonded granulates is established according to the bonding behavior at contacts between bonded granulates. Then, a microscopic interpretation of the degradation parameter which is used to describe the degradation evolution in these models is provided based on the micromechanics theory. Finally, a series of isotropic, constant stress ratio and biaxial compression tests on the bonded geomaterials are carried out by a two-dimensional DEM code, and then the degradation evolution observed in the DEM tests is compared with the results predicted by the constitutive models. It is shown that it is available to evaluate the degradation evolution in constitutive models for bonded geomaterials by DEM. The degradation evolution assumed in the DSC model agrees well with the simulated results; as for the Nova model, the predicted results differ significantly from the simulated ones in the biaxial compression tests; while the degradation parameter in the superloading yield surface model can not well describe the degradation evolution observed under three loading conditions.