Abstract:

 To address theoretical challenges in designing and constructing highwater pressure support systems for deep underground projects, a mechanical model for circular tunnels in highwater pressure environments, mainly supported by preanchoring and pregrouting, is proposed. To achieve this, the "fluidrock coupling" principle of geomechanics is applied to analyze the mechanical model of excavation unloading under anchorgrouting support. Furthermore, analytical solutions for stress, displacement, and seepage fields, which are subsequently validated against finite element solutions, is derived. Next, the effect of radial reinforcement support parameters on the stress field in the primarilysupported surrounding rock area is visually illustrated. Moreover, the principles behind presupport through reinforcement grouting are elucidated employing the HoekBrown criterion for rock mass failure and calculations of the maximum effective shear stress circle. Additionally, the influence of radial reinforcement parameters and tunnel diameter on excavation safety is explained. The results are as follows. (1) The analytical solution aligns with the numerical solution, confirming its accuracy. (2) Preanchoring and pregrouting support enhances excavation safety by increasing radial stress in the surrounding rock, thereby reducing maximum effective shear stress. Additionally, it improves the integrity of the rock mass, increasing the yield surface of the surrounding rock. (3) The significance of radial reinforcement parameters for safety follows this order: rockbolt diameter > number of rockbolts > rockbolt length. (4) Thus, the safety coefficient achieved through radial reinforcement anchoring grouting support gradually decreases as the tunnel diameter increases.〖JP〗