Influence of advanced engineering measures on displacement and stress field of surrounding rock in tunnels crossing active strike-slip faults

Based on significant improvements in engineering materials,three advanced engineering measures have been proposed-super anchor cables,high-strength concrete anti-fault caverns,and grouting modification using high-strength concrete-to resist fault dislocation in the surrounding rock near tunnels crossing active strike-slip faults.Moreover,single-or multiple-joint advanced engineering measures form the local rock mass-anti-fault(LRAF)method.A numerical method was used to investigate the influence of LRAF methods on the stress and displacement fields of the surrounding rock,and the anti-fault effect was evaluated.Finally,the mechanism of action of the anchor cable was verified using a three-dimensional numerical model.The numerical results indicated that the anchor cable and grouting modification reduced the displacement gradient of the local surrounding rock near the tunnels crossing fault.Furthermore,anchor cable and grouting modifications changed the stress field of the rock mass in the modified area.The tensile stress field of the rock mass in the modified anchor cable area was converted into a compressive stress field.The stress field in the modified grouting area changed from shear stress in the fault slip direction to tensile stress in the axial tunnel direction.The anti-fault cavern resisted the dislocation displacement and reduced the maximum dislocation magnitude,displacement gradient,and shear stress.Among the three advanced engineering measures,the anchor cable was the core of the three advanced engineering measures.An anchor cable,combined with other LRAF measures,can form an artificial safety island at the cross-fault position of the rock mass to protect the tunnel.The research results provide a new supporting idea for the surrounding rock of tunnels crossing active strike-slip faults.

Elasto-plastic analysis of the surrounding rock mass in circular tunnel based on the generalized nonlinear unified strength theory

The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the rock properties on its deformation and failure of rock mass, the generalized nonlinear unified strength theory and elasto-plastic mechanics are used to deduce analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of tunnel under uniform ground stress field. The results show that: intermediate principal stress coefficient b has significant effect on the plastic range,the magnitude of stress and surrounding rock pressure. Then, the results are compared with the unified strength criterion solution and Mohr–Coulomb criterion solution, and concluded that the generalized nonlinear unified strength criterion is more applicable to elasto-plastic analysis of underground tunnel surrounding rock.