A new type of rockbolt model in 3D FDEM and its application to tunnel excavation

Abstract

Rockbolt is a common support method in underground tunnel engineering, used to enhance the strength of rock mass and improve the stability of surrounding rock. In this paper, the three-dimensional (3D) FDEM method is employed to study the influence of rockbolts on the deformation and crack evolution of surrounding rock in tunnel engineering. Firstly, the CUDA-based GPU parallel 3D FDEM algorithm is briefly described, and its calculation process is summarized. At the same time, the contact search grid partitioning algorithm is optimized to address the problem of program crashes caused by grid memory overflow. Subsequently, a new rockbolt characterization method suitable for 3D FDEM algorithm is proposed, and the calculation process and constitutive equation of the new rockbolt algorithm are described in detail. The accuracy and feasibility of the new rockbolt algorithm are successfully verified by the pull-out test model and the three-point test model. Next, the numerical simulation of TBM tunnel project is carried out to study the deformation behavior and crack evolution path of surrounding rock after tunnel excavation. The results show that the vertical displacement of surrounding rock at the top of rockbolt tunnel model is greatly reduced, the crack development process is slowed down and the number of cracks is reduced. Finally, the influence of rockbolt row spacing and length on the deformation and crack propagation of surrounding rock is discussed. It is found that as the spacing decreases or the rockbolt length increases, the number of cracks in the surrounding rock gradually decreases, and the vertical displacement at the top of the surrounding rock gradually reduces. This study is helpful to understand the influence of rockbolts on the stability of surrounding rock, especially in tunnel engineering, it is of great significance for adjusting the rockbolt scheme under adverse geological conditions.