单轴加载下裂隙试件主控裂纹演化规律及锚固止裂机理

Master Crack Propagation Rule and Anchoring Mechanism of Fracture Specimens Under Uniaxial Loading

为研究裂隙岩体锚固作用机理,采用水泥砂浆预制不同倾角的裂隙试件,在裂隙上下两端一定距离预埋GFRP(玻璃纤维塑料筋材)锚杆制作加锚裂隙试件进行单轴压缩试验.结果表明:主控裂纹的形成与贯通是导致试件最终破坏的直接原因.无锚裂隙试件,主控裂纹贯通路径单一、贯通速度快,且受预制裂隙影响明显,裂隙倾角越大,主控裂纹扩展方向与裂隙轴线夹角越小.裂隙试件加锚后,主控裂纹贯通路径增多,裂隙倾角对主控裂纹的引导作用减弱.锚杆对裂隙试件峰前平均强度和峰值强度作用不大,但能够有效延长试件峰后强度的持续时间.无锚试件加载过程中能量释放具有"突变性",释放的总能量较少,加锚试件能量释放具有"渐变性",释放的总能量较多.裂隙扩展过程中能量的快速释放是主控裂纹形成和扩展的标志,主控裂纹数量越多、路径越长释放的能量就越大.锚杆的主要作用在于限制主控裂纹的快速形成和扩展,在相同的外力功作用下产生更多、更大范围的损伤和微裂纹,从而改变主控裂纹扩展路径,延长主控裂纹的贯通长度,通过遏制主控裂纹快速贯通来增加裂隙岩体的峰后强度和抗变形能力.

In order to study the anchorage mechanism of fractured rock mass,a uniaxial compression test was carried out by prefabricating fracture specimens with different inclinations of cement mortar and prefabricating GFRP anchors at both sides of the fracture.The results show that the main crack is the direct cause of the final failure of the specimen.Under the anchorless condition,the main control crack propagation path is relatively single,and the crack inclination angle has a guiding effect on the main control crack.The larger the crack inclination angle,the smaller the angle between the main control crack propagation direction and the crack axis.After the fracture specimens are anchored,the main control crack propagation path increases,and the guiding effect of the crack inclination angle on the main control cracks weakens.The bolt has little effect on the pre-peak strength and peak strength of the fracture specimen,but it effectively extend the duration of the post-peak strength of the specimen and increase the post-peak equivalent equivalent-strength of the specimen.The energy release during the loading process of the anchorless specimen is‘mutagenic’,and the total energy released is less.The energy release of the anchored specimen is‘gradual’and the total energy released is more.The rapid release of energy is a sign of the formation and expansion of the main control crack.The more the number of main control cracks and the longer the path,the greater the energy released.The main role of the bolt is to limit the rapid formation and expansion of the main control crack,and to generate more and more extensive damage and micro cracks under the same external force work,thereby changing the main control crack propagation path and extending the main control crack.The length increases the post-peak strength and resistance to deformation of the fractured rock mass by suppressing the rapid penetration of the master crack.