复杂应力条件下裂隙网络扩展机制试验研究

Experimental study on mechanism for fracture network initiation under complex stress conditions

裂隙岩体是工程最普遍的施工对象之一,工程扰动下裂隙的萌生、扩展和贯通均对岩体变形及强度特性产生显著影响。利用RMT–150C试验机及侧向加压设备,对含不同形式预制裂隙类岩石试样开展单轴及双轴压缩试验。结合不同加载条件下岩体裂隙扩展路径、破坏模式及声发射能量特征分析,并根据声发射定位事件特征,研究岩体裂隙网络在复杂应力条件下的扩展机制。分析结果表明:(1)侧向压力作用下,应力–应变曲线延性逐渐增强;(2)新生裂隙均自初始裂隙尖端产生并扩展,且侧压使得裂隙扩展路径会发生明显偏转;(3)声发射事件空间定位与宏观裂隙扩展过程具有较好的对应关系;(4)典型试样裂隙扩展前声发射定位事件占总定位事件比值均在80%以上,表明宏观裂隙扩展源自微裂隙的损伤累积。研究成果对于更加真实地分析模拟工程岩体失稳过程具有重要指导意义。

As one of the most common object in rock engineering,the fractures in the rock mass may appear initiation and propagation under the engineering disturbances. Fracture initiation and propagation will change the deformation and strength characteristics of rock mass obviously. Therefore,a series of uniaxial and biaxial compression tests are carried out for the fractured specimens through RMT–150C and lateral pressure-adding equipment. Combined with the characters analysis of fracture propagation path,failure modes,acoustic emission（AE） energy and the positions of AE events under different loading conditions,the mechanism of fracture propagation is researched. With the increase of lateral pressure,the ductility of stress-strain curves increases. The newly formed cracks propagate from the initial fracture tips under the whole conditions,while the propagation path changed hugely under the biaxial compression condition. The positions of AE events during the loading process match well with the macroscopical fracture propagation path. The ratios of AE events before fracture initiation and the whole loading process for the typical specimens are all above 80%,which proves that the fracture initiation and propagation is the result of microcracks development and damage accumulation in the specimen. The results are significant for simulating unstable process of engineering rock mass more effectively.