| Interfaces with different kinds of macroscale scales are an important feature of geological bodies that distinguish them from other materials,such interfaces are called "structural surfaces",and the joint morphologies of rock masses are varied.Usually under the action of external force,slipping,misalignment and other phenomena often occur.In order to enhance the overall stability of the rock mass,can improve the shear strength of different rock mass joints or the structural surface is prone to landslides,moving places to use bolts to strengthen the rock mass,so as to avoid the structure cracks or mismovements,because the bolt can withstand tensile,shear,bending,torsion and other deformations,and the cost is relatively low,therefore,bolt technology is widely used in practical engineering,but also to improve the stability of joint rock mass has great engineering practical significance.In this thesis,the shear resistance and force characteristics of the unanchored structural surface and the anchored structural surface are analyzed respectively,and the specific content and conclusions are as follows:(1)For unanchored structural surfaces,since the joint roughness coefficient is the key factor in predicting the peak shear strength of rock mass joints,a new method for quantitatively calculating two-dimensional rock mass joint JRC is proposed.Firstly,two dimensionless indexes,the cumulative relative undulation degree CRRA and the weighted average gradient WAG,are defined to characterize the morphological characteristics of the joint profile.Secondly,the CRRA and WAG of each profile are calculated for the 10 standard roughness profiles proposed by Barton and Choubey,and on this basis,the multiple nonlinear fitting method is used to represent the JRC formula with CRRA and WAG.Finally,the effectiveness of the formula is confirmed by indoor and numerical simulation experiments.(2)For the anchored structural surface,when the shear direction is coplanar with the anchor tendency,this thesis makes the following research to study the anchoring mechanism of the anchor: firstly,the three-dimensional model is established by rhinoceros and Flac3 D software,and the shear test command flow of the anchored structural surface is written,and then the Flac3 D software is used to perform numerical simulation tests to reflect unknown parameters;Secondly,the numerical simulation results are post-processed to obtain the relationship between the shear force and the shear displacement of the anchored structural surface,and the distribution function relationship of the reaction force on the compressive side of the rock mass along the anchor is derived.Finally,based on the classical beam theory,a mechanical model is established according to the principle of minimum potential energy variational force,and the expressions of axial force and shear force at the structural surface are derived,so as to further obtain the calculation formula of the shear force of the bolt at the structural surface.In addition,the "guide rail action" of the bolt when the anchoring angle β≤ 90° and the reasons for the length of the structural surface protruding from the center point of the bolt when the anchoring angle β> 90° are analyzed,which provides a strong basis for the shear resistance of the structural surface in the actual project.(3)On the basis of coplanarism,considering that the force on the rock mass in the actual engineering may come from other directions,the anchoring mechanism of the anchor when the shear direction and the anchor tend to be non-coplanar.Firstly,the three-dimensional model is established by rhinoceros and Flac3 D software,and then the Flac3 D software is used for numerical simulation calculation.Secondly,the numerical simulation results are analyzed and processed.Finally,based on the classical beam theory,a mechanical model is established based on the principle of minimum potential energy variation.The following conclusions are obtained: when the anchoring angle is β≤ 90°,the shear resistance of the bolt increases with the increase of the anchoring angle,and when the anchoring angle β> 90°,the shear resistance of the bolt decreases with the increase of the anchoring angle.The axial and shear expressions of the anchored structural surface anchor at the structural surface are derived.The reasons for the torsional deformation of the bolt and the mechanical mechanism of the anchored structural surface were analyzed. |
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