Degradation Law of Tunnel Surrounding Rock Performance and Engineering Management Measures Based on Dynamic Displacement Back Analysis

Abstract

Tunnel construction is accompanied by higher risks, and the mechanical properties of the tunnel Surrounding Rock (SR) will change with the excavation of the tunnel. To better understand the performance degradation law of the surrounding rock during tunnel construction, this study selects a domestic mountain tunnel project as the research object and uses a 30m long tunnel to construct a finite element model. It proposes a dynamic displacement back-analysis method for the elastic modulus, a parameter of the surrounding rock, based on the theory of the loose zone. The dynamic displacement back analysis is carried out on the finite element model. The calculation results showed that the root mean square errors of the tunnel finite element model vault settlement data and the real data were 0.17mm, 0.10mm and 0.75mm, respectively, when the deterioration function was selected as a linear function, a sine function, and no deterioration was considered. The dynamic displacement back-analysis results based on the sine deterioration function achieved the highest accuracy. The sine function was the most suitable choice for the degradation function of the surrounding rock's elastic modulus. Based on this condition, an analysis of the timing of secondary lining construction was carried out. The results showed that, under conditions that meet the requirements of relevant construction specifications, selecting the working condition with the minimum maximum stress in the surrounding rock was the most suitable time for constructing the secondary lining. This research result also provides a reference for improving the quality level of tunnel engineering management in China.