Nonlinear Finite Element Simulation Method for Contact Face of Rock-anchored Beam and Surrounding Rock in Underground House

The contact face of rock-anchored beam in underground powerhouse is the weak part of the overall structure; it is thus an important content for finite element analysis of rock-anchored beam to establish reasonable contact face simulation method. For the contact problem of rock-anchored beam and surrounding rock of underground powerhouse, the mathematical and mechanical models were established to simulate the nonlinear characteristics of the contact surface of rock-anchored beam and surrounding rock. Based on the Desai thin-layer element, a mathematical form of contact element, which is simple and convenient for finite element calculation, was derived. By combining nonlinear elastic theory with elastic plasticity theory, a three-dimensional nonlinear mechanical model, which could simulate the nonlinear phenomena on elastic stage and damage softening phenomena on plastic stage of contact element, was proposed. In view of the deformation characteristics of contact elements such as closing, opening and shearing slip, a segmented safety factor, with considering the bonding, cracking and slip phenomena of contact face, was proposed. The finite element iteration method of the model was discussed in detail, and the finite element program was implemented accordingly. The proposed model was applied to the calculation of rock-anchored beam in an underground powerhouse. Compared with equivalent continuum model, the calculation results of the proposed model show that the stresses in rock-anchored beam are smaller, and the loads are mainly borne bylong bolts. The overall deformation of the rock-anchored beam is increased by 2~3 mm, which means that the contact face decreases the overall stability of rock-anchored beam. The safety factor at the contact face is also slightly smaller and localized tensile damage occurs, which is consistent with the cracking of the contact face of rock-anchored beam in actual engineering. Therefore, the proposed model can reasonably reflect the nonlinear contact characteristics of the contact face, and it provides an effective finite element analysis method for the stability analysis of rock-anchored beam in Underground Powerhouse. © 2017, Editorial Department of Advanced Engineering Sciences. All right reserved.