冻结黏土三轴试验微观变形机理的离散元分析

基于三维颗粒离散单元法,赋予颗粒相应的细观参数,并采用黏结发生在接触颗粒间有限范围内的模型来考虑冻土颗粒中冰的胶结作用,建立了冻结黏土三维离散元数值模型.在相同围压、不同温度和相同温度、不同围压下对冻结黏土的室内三轴试验进行数值模拟,对比了数值试验与室内测试的应力-应变曲线,两者吻合较好.数值模拟结果表明:围压增大会使得接触黏结逐渐失效,在剪切带中胶结冰的破坏区域将增大,而温度的降低则会产生相反结果,这些微观变化都将对冻结黏土的宏观力学变形产生较大影响,同时,细观参数对温度的依赖性也很明显.冻结黏土三轴试验微观变形离散元模拟思路及方法可为今后运用离散单元法研究冻土力学行为提供一定的参考.

Microscopic deformation mechanisms of triaxial test of frozen clay analyzed by discrete element method

Based on three dimensional discrete element method (DEM) of particle flow,all particles are assigned to corresponding microscopic parameters and the cementation of ice between two contacting particles is simulated by a bonding model,which is effective in a limited radius,a three dimensional numerical model of frozen clay is established.A series of triaxial experiments on frozen clay are simulated under different tempera-tures and confining pressures,which shows that the simulated stress-strain relation agrees with experimental data very well.Numerical simulation results show that the adhesive contact will gradually fail with increase of confi-ning pressure,together with expanding destruction area of the cement ice in shear zone.But an opposite phenom-enon will appear with decreasing temperature.All these microscopic changes will have a great impact on macro-scopic mechanical deformation of frozen clay.It is also found that the microscopic parameters of particles heavily depend on temperature.The idea and method of this paper may help to simulate mechanical behaviors of frozen clay by discrete element method (DEM).