破裂围岩锚固体变形破坏特征试验研究

为了进一步揭示破裂围岩锚固体的承载机制，在自主研制的真三轴物理模拟试验系统的基础上，采用反复加卸载围压的方法预制破裂岩体，加锚后进行继续加载试验，研究破裂围岩锚固体以及锚杆的变形破坏特征。研究发现，随着锚杆预紧力的增加，锚固体变形模量随之增加，全应力–应变曲线呈现双峰特征。在锚杆预紧力较小的情况下，破裂围岩内部滑移块体主要沿原有裂隙面滑移，二次破坏较少发生且裂隙发育位置比较集中。在锚杆预紧力较大的情况下，滑移块体会发生二次破坏，破裂围岩锚固体新生裂隙倾角高、数量多且分布均匀。锚固体变形过程中锚杆控制角在空间以及时间上不断发展变化：锚杆压缩区在空间上为向围岩深部开口的喇叭形，其深度为1～1.5倍托盘直径；随着锚固体压缩变形，锚杆压缩区会发生二次甚至多次破裂。锚杆控制角在压缩区初次破裂时为50°～64°，在压缩区多次破裂后最终稳定为34°～56°。锚杆在破裂面附近受到两侧滑移块体剪切错动作用下处于压、张、剪复杂应力状态，弯曲变形严重，这反过来使破裂面两侧滑移块体出现一定程度的错动分离。

EXPRIMENTAL STUDY OF DEFORMATION AND FAILURE CHARACTERISTICS OF ANCHORAGE UNIT IN FRACTURED SURROUNDING ROCKS

In order to further reveal bearing mechanism of anchorage unit in fractured surrounding rock，fractured rock mass prepared in advance by way of repeatedly loading and unloading confining pressures was anchored and loaded subsequently on independently developed true triaxial physical simulation test system，from which the deformation and failure characteristics of fractured surrounding rock and anchor were studied. The results show that the elastic modulus of anchorage unit increases with increasing prestress of anchor bolt；and complete stress-stain curve possesses the characteristics of double peak. When the prestress of anchor bolt was weak，the slipping blocks in fracture surrounding rock would skid again along former fissure plane；second damage happened rarely；and the new fractures spread intensively while when the prestress of anchor bolt was strong；the slipping blocks would broken for the second time；and new fractures with high dip angle developed heavily and evenly. Controlling angle of anchor bolt was continuously developing and changing both in space and time. The profile of compression zone was an inward opening horn form whose depth was 1 to 1.5 times of anchor tray diameter. Along with the deformation of anchorage unit，the damage of compression zone would happened for the second and even more times while controlling angle of anchor bolt was 50°–64° at the first time and got stable around 34°–56° finally. Because of shear displacement influence of slipping blocks beside the fracture，anchor bolt was crooked severely due to complex stress condition including compression，tension and shear stress，which enabled blocks beside the fracture to separate from each other to a certain extent in reverse.