Development of shield model test system for studying the bias load of shield in soil-rock compound strata

Abstract

The deviation mechanism and control of shield attitude are crucial, especially in soil-rock compound strata. To address this issue, a model test apparatus was established to conduct shield bias-load testing during tunneling. A model test was performed on shield tunneling in upper-soft lower-hard strata to verify the functionality of the developed test system. Subsequently, numerical simulations were conducted to investigate the shield bias moment in such strata and its influencing factors. The results demonstrated that the developed shield bias-load model test apparatus effectively controlled tunneling parameters and monitored the shield's bias moment in real-time. In the upper-soft lower-hard strata, the shield's bias moment increased as the proportion of rock layers in the tunnel face increased in the head-up direction, with the highest increase occurring when the soil and rock ratio in the tunnel face was 1:1. Interaction decoupling analysis in the numerical models revealed that the interaction between the shield shell and the strata was the primary cause of the shield's attitude change in soil-rock compound strata. Additionally, the shield's bias moment increased as the soil-rock modulus ratio decreased, with the bias moment range of the soil modulus being 4.66 times that of the rock modulus. This study provides valuable insights for shield operation in soil-rock compound strata.