- 1. 北京科技大学土木与资源工程学院
- 2. 北京科技大学
摘要: 裂隙岩体广泛存在于地下工程中，对循环扰动荷载十分敏感，研究其裂隙的产生和扩展是岩体稳定性分析的重要基础。从微观角度，采用颗粒离散元法开展预制裂隙花岗岩循环加卸载试验，首先以MATLAB图像处理技术识别花岗岩细观组分，结合室内单轴压缩试验结果对细观力学参数进行标定。通过编制颗粒流代码追踪裂隙的类型和扩展过程，分析岩石破坏过程中裂隙发展的阶段性特征。研究结果表明：不同倾角裂隙岩石的新生裂隙走向与预制裂隙贯通方向基本一致；根据新生裂隙的优势倾向分组得到裂隙起裂角与预制裂隙倾角的关系：倾角β ≤45°时剪切和张拉裂隙的起裂角单调递减，倾角β ≥60°时剪切和张拉裂隙的起裂角单调递增；循环扰动荷载增加了裂隙岩体的轴向变形，轴向累积残余应变曲线呈反S形，随应力上限的提高更快进入加速阶段；模型试件的峰值强度随裂隙倾角的增大表现出先减小后增大的趋势，峰值强度为实验室完整岩石单轴抗压强度的63%~89%，反映出明显的岩石劣化现象；在循环荷载作用下，剪切裂隙和张拉裂隙增长曲线表现出明显的变化特点，对合理界定岩石变形破坏阶段具有一定的参考意义。
Particle flow simulation of crack propagation characteristics of granite under cyclic disturbance load
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Abstract: Micro cracks in natural rock mass have a significant impact on the stability of underground engineering structures. The mechanical properties of cracked rock mass determine the strength of rock mass and the mechanism of its compression failure. The instability and failure of surrounding rock are often induced by the expansion and penetration of these internal cracks. In practical engineering, rock mass excavation is a process of dynamic disturbance. The mechanical properties of rock under cyclic load are significantly different from those under static load. Its own characteristics and the development of microcracks are the main factors of rock fatigue failure. From the microscopic point of view, the particle discrete element method is used to carry out cyclic loading and unloading tests of pre-existing cracked granite. Firstly, the micro-component of granite is determined by MATLAB image processing technology, and the micro-mechanical parameters are calibrated based on the indoor uniaxial compression test results. By compiling particle flow code to track the type and expansion process of cracks, the stage characteristics of crack development in rock failure process are analyzed. The research results show that the orientation of new cracks in fractured rocks with different dip angles is basically the same as that of prefabricated cracks. According to the dominant tendency of new cracks, the relationship between the crack initiation angle and the inclination angle of prefabricated cracks is obtained: when the inclination angle β ≤ 45°, the crack initiation angle of shear and tension cracks decreases monotonically, while when the inclination angle β ≥ 60°, the crack initiation angle of shear and tension cracks increases monotonically; Cyclic disturbance load increases the axial deformation of fractured rock mass, and the axial cumulative residual strain curve presents an inverse S-shape, which enters the acceleration stage faster with the increase of the upper stress limit. The peak strength of the model specimen shows a trend of decreasing first and then increasing with the increase of fracture inclination. The peak strength is 63 %~89 % of the uniaxial compressive strength of intact rock in the laboratory, reflecting obvious rock deterioration phenomenon. Under cyclic load, the growth curves of shear crack and tension crack show obvious variation characteristics, which has certain reference significance for reasonably defining the deformation and failure stage of rock.