刚性与柔性边界下砂离散元三轴试验力学特性对比分析OA

To better explore the deformation and failure law of sand from a mesoscopic perspective,this paper compares the effectiveness of discrete element triaxial test models under different confining pressure loading modes.Particle flow software(PFC)was used to establish discrete element triaxial tests for HST95 sand samples in different relative densities considering rigid and flexible confining pressure loading modes.Combined with the relevant laboratory triaxial test results,the mechanical characteristics,deformation characteristics and shear failure process of sand samples under two confining pressure loading methods are discussed.The results show that the simulation effect is better under the condition of flexible confining pressure loading mode.The higher the relative density of the sample,the better the flexible confining pressure loading mode than the rigid confining pressure loading mode:compared with the laboratory test results,the errors of stress-strain results under flexible and rigid confining pressure loading modes are within 10%and within the range of 7%～53%,respectively.For the sand in 30%and 70%relative density,the volumetric strain at 20%axial strain is about 0.6 times and 1.1 times of the laboratory test results for the samples under the rigid confining pressure loading mode,and the reduction of the volume under large shear strain is inconsistent with the actual situation.While the errors of the volumetric strain of the two samples under flexible confining pressure loading mode are within 1%.Further,the samples under the flexible confining pressure loading mode can better reproduce the shear failure characteristics of lateral bulging deformation and reveal the formation and development of the shear band.