Experimental study on anchoring mechanism of double persistent jointed rock

Bolt support plays an important role in the mining of the cracked surrounding rock. The exploration of the anchorage control mechanism with joint rock would help to optimize the design of the parameters. In this study,the acoustic emission signals and the deformation fields of the double-joint rock with a 45° dip were monitored by employing the acoustic emission and digital speckle correlation method (DSCM) in the course of the uniaxial compression test. The corresponding relationship between stress-strain curves and acoustic emission signals was established to study the change characteristics of the curves and the distribution rules of the acoustic emission signals. Meanwhile, the effects of anchorage strength and deformation behavior of double-joint rock masses were analyzed. Based on the distribution characteristics and evolution process of the speckle displacement field of double-joint rock surface,the influences of bolt on the failure modes and morphologies of jointed rock were summarized. By analyzing the corresponding relationship between the deformation evolution characteristics of the double-joint rock and the position of the active signals of the acoustic emission,the failure process of the specimen was divided. Combined with the deformation morphologies of the bolt,the mechanics model of the anchored double-joint rock under the compression-shear condition was established,and the force analysis was carried out under different loading stages. The failure mode and the mechanism of anti-compression shear and restraining slip of bolt were well explored. The results show that:① By comparing with the non-anchored specimen,the cracking strength,elastic modulus,and peak strain of the anchored double-joint rock was increased by 30. 7% ,45% ,and 109. 9% ,respectively,while its passion ration was decreased by 50% ,which indicates the axial deformation capability without instable failure was enhanced;② Unstable fracture is the major failure mode of the anchored double-joint rock,which includes five stages: joint filler slip,joint surface dislocation cracking,bottom rock cracking,upper rock crack propagation,and crack penetration;③ The bolt could be not only used to improve the compression-shear strength of the anchorage by combining the bolt's shearing ability with the intact rock's synergistic collaboration,but also enhance the deformation ability of the joint rock through sharing the deformation produced by the external force and inhibiting the sliding of the rock matrix.