| A large number of structural planes exist in the engineering rock mass,which significantly weakens the strength of the rock mass.When subjected to external forces,the potential sliding bodies in the rock mass are prone to slippage and dislocation.The anchor rod can effectively restrain the relative displacement of the structural plane in the rock mass and improve the overall stability of the fractured rock mass.Due to the complex and diverse environment in which the fractured rock mass exists,the anchor rod may exhibit various forms such as stretching,shearing,bending,and twisting.Therefore,the anchoring mechanism of the anchor rod under complex stress conditions is systematically studied to optimize the fracture rock anchoring design and improving the safety of fractured rock engineering have important engineering practical significance.The main research contents and conclusions are as follows.(1)Based on the classical beam theory,this paper assumes that the reaction force of the rock mass acting on the compression side of the shear deformation section is parabolic along the bolt direction,and a mechanical analysis model was established under the condition that the shear direction and the bolt inclination are coplanar.Comprehensively considering the axial deformation,deflection deformation,displacement variation,deformation coordination relationship,critical anchoring state and length of the shear deformation section of the anchor rod at the structural plane,the calculation formula for the shear resistance of the anchor rod was obtained.(2)Through the indoor direct shear test the actual measured value of the bolt shear force and the calculated value of the theoretical formula were compared and analyzed,and combined with the shear deformation of the bolt,the feasibility of the mechanical analysis model of structural plane with anchor and the formula of bolt shear force were verified.Based on this,the expression of the optimal installation angle of the anchor rod was derived,and the contribution of the internal force of the anchor rod to the anchoring effect was analyzed.(3)Based on the numerical model of the bolt considering the axial force and the transverse force,the shear force calculation formula is embedded into the LOCAL REINFORCEMENT element of UDEC.According to a bedding rock slope,the influence of anchor length,anchor angle,bolt spacing and layout on the slope stability was analyzed,and the optimal anchoring scheme was proposed based on orthogonal test.(4)The anchoring mechanism under the condition that the shearing direction is perpendicular to the bolt inclination were carried out,and the shear force formula and the bolt torque expression under this condition were obtained.The correctness of the formula was verified by the indoor direct shear test.(5)In order to solve the technical problem that the direct shear apparatus and other test equipment were difficult to simulate the real rock mass state more accurately,a new type of test equipment was developed,which can realize the "compression-shear-torsion" test and the "tension-shear-torsion" test. |
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