Study on the control effect of tunnel large deformation considering surrounding rock unloading expansion effect and support structure characteristics

Abstract

As engineering construction advances, the issue of large tunnel deformations remains one of the most common and challenging hazards to control during construction. Control measures for such deformations are often limited to a single factor—either the surrounding rock or the support structure—without comprehensively accounting for the effects of excavation unloading and the specific characteristics of the support structure. To address this gap, this paper proposes a numerical simulation method that considers both the expansion effect due to surrounding rock unloading and the properties of the support structure (UE-SCM). Through a combination of laboratory testing and numerical simulation, this study evaluates the control effectiveness of three support structure systems under large deformation conditions, analyzing the interaction between the surrounding rock and the support structure to interpret the results. Key findings are as follows: 1) Conventional numerical simulations often overlook the weakening of the surrounding rock and changes in the mechanical properties of support materials induced by excavation unloading, leading to designs with limited effectiveness in controlling large deformation; 2) The proposed simulation method, focused on large tunnel deformations, emphasizes the effects of changes in the elastic modulus of the rock mass and the support structure. 3) For higher levels of large deformations, a support structure system with yielding properties is recommended, as it improves control over large deformations.