Abstract
The load transfer control equations under bolt-surrounding rock interaction are established on the basis of classical beam theory and the trilinear shear slip model. The axial stress and transverse shear force distributions of the anchorage body are obtained by solving the equations. The equivalent forces obtained by the transverse force and axial shear stress of the bolts are applied to rock mass elements to simulate the support effect. A new dynamic algorithm for bolts is proposed in considering of the axial and transverse deformation of the anchorage body. The rationality of the algorithm is verified by comparing with laboratory pullout and shear tests of bolts. A dynamic time-history case study of underground caverns is conducted using this algorithm. Results indicate that (1) the algorithm may reflect the stress and deformation characteristics of bolts during an earthquake; (2) for the antiseismic support effect of the surrounding rock at fault, the bolt algorithm in this study is more valid than the algorithm that considered only the axial deformation of bolts; (3) in the support force of the bolt to the surrounding rock, transverse force is the key to limit fault dislocation and reduce the dynamic damage of the rock at fault.
Highlights
Southwest China is rich in water resources and has several hydropower stations
On the basis of classical beam theory and the trilinear shear slip model, a new dynamic algorithm that considers the axial and transverse deformations of bolts is proposed. e algorithm is applied to the seismic support analysis of an underground project, and the following conclusions are drawn: (1) e proposed dynamic algorithm fully considers the characteristic of slippage and yield of interface between the anchorage body and surrounding rock and the transverse deformation characteristic of bolts. e algorithm can effectively simulate the stress and deformation of bolts located at faults or joints under seismic load. e rationality and feasibility of the dynamic algorithm are verified through comparison using pullout data and a shear test of bolts
The proposed algorithm is more effective in restraining the surrounding rock in the axial direction of the bolts due to the contribution of the transverse deformation to the axial force. e bolts located at the fault have large transverse deformation, whereas the bolts located at the rock without joint or fault have no transverse deformation. is result indicates that the transverse deformation of bolts in complex rock environment conditions during an earthquake should be considered
Summary
Southwest China is rich in water resources and has several hydropower stations. Restricted by geological conditions, these hydropower stations are mainly built across underground rock. e region is located at plate boundaries with a high probability of earthquakes; the antiseismic performance of underground caverns is directly related to the operational safety of hydropower stations [1]. Several studies have presented static and dynamic calculations for bolt data using numerical methods in underground caverns [2, 21,22,23] These studies have considered only the axial effect and neglected the transverse effect of bolts on the surrounding rock. Erefore, the current study takes underground caverns as research background, considers the axial and transverse deformation of bolts, and establishes the governing equations of load transfer between bolts and the surrounding rock. E rationality of the algorithm is verified, and a 3D finite element method (FEM) model of underground caverns of a hydropower station is used to study the force and deformation regularity and support effect of bolts under seismic load A new analytical algorithm for a fully grouted bolt, which is suitable for seismic time-history analysis under complex conditions, such as joints and fault, is proposed. e rationality of the algorithm is verified, and a 3D finite element method (FEM) model of underground caverns of a hydropower station is used to study the force and deformation regularity and support effect of bolts under seismic load
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