不同围压下岩石抗压强度与变形参数尺寸效应的数值模拟

岩石抗压强度和变形参数是岩石工程设计的重要指标。由于岩石是典型的非均质材料，其强度和变形特性随样品尺 寸的变化而不同。本文采用PFC2D程序模拟了不同围压下不同尺寸岩样的压缩试验。结果表明（1） 岩样具有明显的尺寸效 应。同一围压下，尺寸越大，岩石强度、峰值应变和压缩模量越小，尺寸的变化对岩样的破坏模式影响较小；（2） 岩样具 有明显的围压效应。同一尺寸的岩样，随着围压的增大，岩石强度、峰值应变和压缩模量均增加，其中强度和峰值应变随 围压的增加呈线性增加。同时，随着围压的增大，岩石破裂模式由轴向劈裂破坏向剪切破坏变化；（3） 围压的存在会影响 岩样的尺寸效应。不同尺寸岩样的强度和峰值应变在相同围压区间内的增量基本相同，同时随着围压的增大，其强度和峰 值应变增加，进而使岩石强度和峰值应变的尺寸效应弱化；而不同尺寸岩样的压缩模量在相同围压区间内的增长率大致相 同，因而造成围压对压缩模量尺寸效应的影响较小

Numerical Simulation on the Size Effect of Compressive Strength and Deformation Parameters of Rock Materials Under Different Confining Pressures

The compressive strength and deformation parameters of rock materials are important indices of rock engineering. Because a rock is a typical heterogeneous material, its strength and deformation parameters vary with sample sizes. In this paper, the size effects of rock materials under different confining pressures were numerically studied using PFC2D code. The simulation results indicate that (1) rock strength, peak strain and compressive modulus decrease with increasing specimen sizes, whereas the change of specimen size has little effect on the failure mode of these rock specimens. (2) rock strength, peak strain and compressive modulus increase with the confining pressures. Among them, the rock strength and peak strain have linear relations with the confining pressures. In addition, the failure of rock specimens gradually changes from the splitting mode into shear failure mode with the increase in confining pressures. (3) the increments of rock strength and peak strain for different size specimens at the same confining pressure range are approximately the same. Meanwhile, these two parameters increase with confining pressures. Therefore, the size effect of the rock strength and peak strain at high confining pressure becomes weak. In addition, the increasing ratios of compressive modulus for the corresponding scenarios are similar, which causes the confining pressure to have little impact on the size effect of compressive modulus.