基于随机散粒体模型的堆石体真三轴数值试验研究

Numerical simulation of true triaxial tests on mechanical behaviors of rockfill based on stochastic granule model

基于三维变形体离散单元法,模拟堆石体的真三轴试验,研究堆石体在三向不等应力状态下的强度和变形特性。真三轴数值试验装置采用六刚性板加荷方式,等中主应力比路径加载。数值试验结果表明:真三轴数值试验能较好反映堆石体在三向不等应力状态下的应力和变形规律,数值模拟得到宏观应力变形特性与试验规律相似;等中主应力比参数(2 3 1 3b=(σσ)(σσ))的大小对堆石在三向应力状态下应力和强度特性有显著的影响,堆石体在3个加载方向的变形也随该参数的变化而变化,应力比参数b从0到1变化过程中中主应变方向先压缩后膨胀,小主应变方向一直处于压缩状态;堆石体的内摩擦角随着b值的增加而增大,基本符合Lade-Duncan破坏准则;在细观层面上,围压越高,b值越大,颗粒配位数越大;加载过程中,颗粒接触法向和法向接触力各向异性程度加强,各向异性主方向角由水平向转向大主应变方向,试样各向异性系数的演化规律和试样的宏观应力变形曲线相对应,试样的宏观力学特性与细观组构存在内在的关联。

The three-dimensional deformable discrete element method is employed to study the strength and deformation characteristics ofrockfill under three-dimensional unequal stress states by means of true triaxial numerical tests. In addition, the six-rigid-plate loading and the constant value of the intermediate principal stress ratio loading paths are adopted. The simulated results show that the true triaxial numerical tests can preferably reflect the stress and deformation of rockfill under the three-dimensional unequal stress states, and the numerical results are the same as the test ones. The stress ratio parameters significantly affect the stress intensity of rockfill under the three-dimensional stress state and the three-dimensional strain also changes with the increase of the ratio parameters. To be more specifical, when the intermediate principal stress ratio parameter b increases from 0 to 1, the second principal strain direction changes from compression to expansion while the third principal strain direction has always been in the state of compression, and the the internal friction angle of rockfill increases with the increase of b, which basically conforms to the Lade-Duncan failure criterion. In the mesoscopic level, the higher the confining pressure is, the larger the value of b and coordination number of particles are. In the loading process, the anisotropy degree of contact normal orientation and contact normal force are strengthened, the main direction of contact force turns to the loading direction, the anisotropic coefficient evolution curve is similar to the stength curve, in other words, the strength of the rockfill samlpes has some relationship with the normal contact.