(1. State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;2. School of Mechanics and Civil Engineering,China University of Mining
and Technology,Xuzhou,Jiangsu 221116,China)
Abstract: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.
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