粗粒料强度及变形特性的细观模拟

Mesoscopic simulation of strength and deformation characteristics of coarse grained materials

粗粒料是一定级配的岩石颗粒集合体,具有独特的物理力学特性。以粗粒料室内三轴固结排水试验成果为基础,基于离散元颗粒流理论,从细观角度出发,以PFC3D为工具,通过自编程及二次开发,得到按级配生成的粗粒料三轴试验数值模型。引入clump颗粒考虑颗粒形状对粗粒料强度及变形的影响,分析剪胀、颗粒形状、颗粒重排的关系。结果表明:颗粒形状是影响粗粒料强度与变形的主要因素,在其他细观参数一定的情况下,改变颗粒形状,可以显著影响粗粒料的力学行为;BPM模型的应力-应变关系只在低围压下与试验值吻合,随着围压的增大,偏差越来越大;而引入clump颗粒的PFC3D数值模型能很好地模拟粗粒料室内三轴固结排水试验的应力-应变特性,但由于BPM及clump都是刚性颗粒,没有考虑颗粒变形及破碎,造成应变剪胀偏大。

Coarse grained material is the aggregation of rock particles with certain gradation,which has special physical and mechanical properties.Based on the results of consolidated-drained triaxial tests and three-dimensional particle flow code theory,the numerical model of triaxial test for coarse grained materials is obtained by programming and redevelopment of PFC3D（particle flow code of three-dimension） from the view of mesoscopic scale.The influence of particle shape on strength and deformation of coarse grained materials is considered by introducing clump particles.The relations among dilation,particle breakage and rearrangement are analyzed.The numerical results show that particle shape is the main factor affecting the strength and deformation of coarse grained materials.Changing the particle shape can significantly affect the mechanical behavior of coarse grained materials in the case of other mesoscopic parameters unchanged.The stress-strain relationship of bonded-particle model（BPM） is agreed with experimental result only under low confining pressure;the deviation is growing larger with the increase of confining pressure.The stress-strain characteristics of coarse grained materials in consolidated-drained triaxial tests are simulated by PFC3D model using clump particles accurately.The BPM and clump particles are both rigid particles.The shear dilatancy is too large because the particle deformation and breakage are not considered.