颗粒体材料在压缩位移控制加载条件下的力学行为及界面参数对它的影响

Study on Mechanical Behavior of Granular Materials in Compressive Displacement-controlled Loading Condition and Effects of Parameters of Interfaces

采用连续介质快速拉格朗日分析程序(FLAC),模拟了颗粒体材料在压缩位移控制加载条件下的力学行为及破坏过程。颗粒及它们之间的界面被离散为尺寸相同的单元。颗粒被视为各向同性的弹性材料,而界面被视为弹性-应变软化-理想塑性材料。界面完全破坏之后,其内聚力为零而内摩擦角不为零,因而适于模拟颗粒之间的摩擦行为。在双轴压缩条件下的计算结果表明,压应力通过颗粒之间的接触,以应力线的方式在试样的垂直方向上传递,最终形成了清晰、有序的图案,而剪切应变增量的高值区主要位于一些界面上。从剪切应变增量的高值区中能发现试样中的最薄弱环节。此外,还研究了试样两侧的压应力、界面的初始内聚力及内摩擦角对试样的应力—时步曲线的影响。

Fast Lagrangian Analysis of Continua（FLAC） is used to model the mechanical behavior and failure process of granular materials under the condition of the compressive displacement-controlled loading.Circular granulae and interfaces between them are divided into squared elements with the same size.Granular elements are seen as isotropic and elastic materials,while interface elements obey a strain-softening and ideal plastic relation beyond the occurrence of failure.After an interface element is completely failed,its cohesion is assigned to be zero and the internal frictional angle is not zero.These assumptions are applicable for simulation of pure friction behavior between granulae.Numerical simulations are conducted in biaxial plane strain compression.Numerical results show that the compressive stresses propagate in the direction of the displacement-controlled loading within the specimen in the form of the compressive stress lines passing through the contact points between granulae.Eventually,clear and ordered compressive stress lines are formed.In some interface elements,shear strain increments are high.It is easy to find the weakest parts of the specimen from the regions with higher shear strain increments.Besides,effects of confining pressure acting on the lateral sides of the specimen,initial cohesion and internal frictional angle of interface elements on the stress-timestep curve are studied.