研究岩体细观裂纹演化有利于揭示其宏观破裂机理。利用块体离散元颗粒模型(Grain Based Model,GBM),通过一系列的数值模拟试验,在分析单轴压缩及直拉试验下晶粒粒间接触细观参数对岩体宏观参数影响规律的基础上,提出了块体离散元GBM岩体试样的细观参数标定方法。同时以该标定方法为基准,研究了单轴压缩下花岗岩不同矿物之间的穿晶裂纹以及晶界裂纹演化规律,并与室内试验结果对比。研究表明:粒间接触刚度可以用来标定岩体的泊松比以及弹性模量,粒间抗拉强度、黏聚力以及摩擦角可以用来校准岩体的峰值强度,岩体的抗拉强度受粒间抗拉强度影响最为显著;单轴压缩下花岗岩的数值模拟结果与室内试验结果较为吻合,即穿晶裂纹数明显小于晶界裂纹数,同时石英－黑云母晶界裂纹大于长石－黑云母晶界裂纹;改进标定方法的块体离散元颗粒模型(GBM)因考虑了承载板接触影响及岩体峰值强度的标定,能较好地模拟岩体内部晶界裂纹、穿晶裂纹的行为特点。
Abstract
Studying the meso-cracking evolution of rocks is of help to reveal the macro-cracking mechanism. Based on numerical simulations using block discrete element GBM (Grain Based Model), we proposed a method of calibrating mesoscopic parameters of the GBM rock specimens through analyzing the influence of inter-granular contact parameters on the rock macro-parameters under uniaxial compression tests and straight-pull tests. Using the present method, we further investigated into the evolution of transgranular cracks and grain-boundary cracks between different minerals of granite under uniaxial compression, and compared the numerical results with laboratory test results. Our findings revealed that the Poisson's ratio and elastic modulus of rock can be calibrated by using inter-granular contact stiffness, and the peak strength of rock can be calibrated by inter-granular tensile strength, cohesion and friction angle. The tensile strength of rock is affected most remarkably by the inter-granular contact tensile strength. The numerical simulation results of granite under uniaxial compression are consistent with laboratory tests: the number of transgranular cracks is significantly smaller than the number of grain-boundary cracks, and the quartz-biotite grain-boundary cracks are larger than feldspar-biotite grain-boundary cracks. In conclusion, the block discrete element GBM with improved calibration method can well simulate the behavior characteristics of grain-boundary cracks and transgranular cracks in rockmass as it considers the contact effect of bearing plate and the calibration of rock's peak strength.
关键词
岩体 /
GBM /
细观参数 /
标定方法 /
晶界裂纹 /
穿晶裂纹
Key words
rock mass /
GBM /
meso-parameters /
calibration method /
grain-boundary cracks /
transgranular cracks
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