堆石料宏细观力学特性离散元分析

Discrete element analysis on macro-microscopic mechanical properties of rockfill material

堆石料的力学特性直接影响堆石坝工程的设计、施工和运行,对坝体变形及安全有重要影响。基于大石峡混凝土面板堆石坝工程,采用离散单元法(DEM)建立了接近于3BA区堆石料真实颗粒形状的椭球颗粒试样,开展了一系列常规三轴数值试验,研究了3BA区堆石料的宏、细观力学特性。通过不同围压下的宏观应力应变演化曲线,获得堆石料的宏观应力、变形指标。采用平均接触力将接触网络划分为强、弱2个子网络,分析强、弱接触网络的配位数分布与拓扑演化规律。结果表明:割线模量、泊松比、峰值内摩擦角与围压呈线性变化,剪胀角与围压呈非线性变化;颗粒体系内接触的拓扑演化主要发生在弱接触网络,进而影响堆石料的宏观体积变化,强接触网络内的接触保持不变,为堆石料提供稳定的传力通道。研究结果可用于指导实际工程中不同围压下宏观力学指标的选取。

Mechanical properties of rockfill directly affect the design,construction and operation of the rockfill dam,and have an important influence on the deformation and safety of the dam.In this study,based on the Dashixia concrete face rockfill dam project,ellipsoidal particle samples close to the real particle shape of the rockfill in 3BA zone were established by discrete element method(DEM).A series of conventional triaxial numerical tests were carried out to study the macro-microscopic mechanical properties of the rockfill in 3BA zone.The macro stress and deformation indexes of rockfill were obtained by the evolution curves of macro stress and strain under different confining pressures.The average contact force was used to divide the contact network into strong and weak subnetworks,and the coordination number distribution and topological evolution of the strong and weak contact networks were analyzed.The results showed that the secant modulus,Poisson′s ratio,peak internal friction angle change linearly with confining pressures,while the dilatancy angle changes nonlinearly with confining pressures.The topological evolution of the contact behaviors in the particle system mainly occurs in the weak contact network,which affects the macroscopic volume change of the rockfill,while the contacts in the strong contact network remains unchanged,providing a stable force transfer way for the rockfill.The research results can be used to guide the selection of macroscopic mechanical indexes under different confining pressures in practical engineering.