A numerical analysis has been conducted to evaluate the effect of confining pressure on the damage evolution and the fracture process of brittle rock materials by using the rock failure process analysis code (RFPA2D). A fractal dimension D associated with material damage and a damage variable v are defined to describe the damage process of the specimen subjected to tensile or compressive load. We find that the spatial distribution of microfractures is fractal and has very good statistical self-similarity in the specimen under different confined conditions. The fractal dimension D increases progressively with loading. Meanwhile, the damage variable v develops from 0 to 1, and the specimen failure is characterized by the critical damage variable vc with 0.4<vc<0.8. The initial damage is delayed by the confining pressure. The confining pressure plays an important role in the mode of rock failure in numerical simulations. The tensile microfractures dominate near the brittle splitting of the specimens under no and low confining pressure. Conversely, a few tensile microfractures appear in the ductile shear failures of the specimens under immediate or high confining pressures. The tensile microfractures run through all failure processes in the specimen under uniaxial tensile loading. The stress-strain curves are also obtained in numerical simulation. The results show that the specimen is strengthed by the confinement and fails according to Mohr-Coulomb failure criterion.

Based on the phenomenon that acoustic emissions (AE) generated by rock mass increase suddenly because of underground excavation, time sequence of AE rate in rock failure has been discussed by using statistical damage theory. It has been demonstrated that how the influence of confining pressure on the deformation behavior and AE characteristics in rocks can be inferred from a simple mechanics model. The results show that loading confining pressure sharply brings out increasing of AE. On the other hand, few AE emits when confining pressure is loaded sharply, and AE occurs again when axial pressure keeps on increasing. These results have been well simulated with computer and show close correspondence with directly measured curves in experiments.

基于岩石变形过程中损伤局域化现象，根据岩石材料随机性的特点，通过二维网络系统损伤演化的有限元数值模拟发现：岩石微破裂在损伤演化过程中显示出从均匀随机的无序逐渐向局域化的有序转化特征，不论微破裂如何演化，最终都诱致岩石网络系统产生突变破裂现象。用岩石微破裂与声发射具有一致性的假设，模拟出岩石破裂过程中声发射空间分布的规律。

利用RFPA2D对岩石在不同围压下损伤破坏演化过程进行了数值模拟，基于岩石损伤定义分形维数以描述试样在各种加载条件下微破裂的演化过程。计算结果表明：分形维数和损伤变量随着荷载的增加逐渐增大，岩石的起始损伤随着围压增加而被延迟，试样强度随着围压的增加而增加，其宏观破坏符合Mohr-oulomb破坏准则。

针对脆性岩石细观强度非均匀、离散性特征，利用重正化群理论建立了岩石临界破坏重正化模型，系统研究了岩石宏观临界强度和细观强度的定量关系，采用条件概率方法处理模型中细观单元间的应力转移，从而求得岩石临界破裂时的临界概率P*，着重研究了岩石均质度与岩石峰值强度的理论关系。此外，利用岩石破裂过程分析程序（RFPA）模拟了岩石单轴压缩下细观破裂演化至宏观破裂的全过程。研究结果表明，数值模拟和重正化群得到的岩石峰值强度十分吻合。