基于离散元法的不同形状土体颗粒力学性能细观分析

Meso-analysis of mechanical properties of soil particles with different shapes based on discrete element method

岩土体由大量不规则颗粒组成,单个颗粒的形状对于土体的宏观物理力学性质有直接的影响。基于离散元理论,建立了5种不同形状颗粒的三轴试验数值模型,从细观角度计算分析了土颗粒几何形状对介质剪切强度、配位数、孔隙率、颗粒旋转以及阻尼耗散能量的变化规律。结果表明,不规则形状颗粒的抗剪强度比球形颗粒的抗剪强度高,圆柱形颗粒比椭球形颗粒抗剪强度大;球形颗粒模型在加载过程中颗粒旋转角度较大,试样剪胀现象明显;不规则形状颗粒由于颗粒间咬合作用较强,颗粒旋转较小,试样没有发生明显剪胀现象。试验模拟发现,颗粒形状越不规则,阻尼耗散的能量越大,表明试样储存的动能越少,颗粒越不易发生移动,试样也越稳定。

Soil are composed of a large number of irregular particles.The shape of particles has a direct impact on the macro physical and mechanical properties of soil.On the basis of the discrete element theory,PFC3D was used to generate five particle models of different shapes.The impacts of particle shape on the shear strength,coordination number,porosity,particle rotation and damping dissipation energy of soil mass were analyzed through the numerical simulation of triaxial test as well as from a microscopic point of view.The results show that the shear strength of irregularly shaped particles is higher than that of spherical particles,and that among the irregularly shaped particles,the shear strength of cylindrical particles is higher than that of ellipsoidal particles.Since spherical particles are associated with relatively large rotation angles during loading,samples have obvious dilatancy.However,among the irregularly shaped particles,since the inter-particular interlocking is strong and the rotation angles are relatively small,samples does not display significant dilatancy.The more irregular is the particle shape,the greater the energy will be dissipated by damping,indicating that the lesser is the kinetic energy stored in samples,the less likely the particles will move,and the more stable the sample will be.