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ABSTRACT: This study investigates the performance of yielding bolt in a weak rock mass tunnel with high in-situ stress conditions. The genetic algorithm and the Komamura-Huang rheological model are combined to perform an inversion analysis of the mechanical parameters of the weak surrounding rock mass before and after implementing the anchoring system. The results based on an actual tunnel project suggest that the mechanical properties all enhanced in the anchoring tunnel section The elastic modulus of the surrounding rock increased by 45.7%, the cohesive force increased by 18.1%, and the friction angle increased by 2.92%. Hence, the yielding bolt anchor can effectively prevent the squeezing deformation of the surrounding rock mass and improve the structural integrity of the tunnel lining. The performance of the anchoring system and the inversion process of the mechanical parameters can guide the design and construction of similar tunnel projects in weak rock mass configurations. 1. INTRODUCTION During the excavation progress in a rock tunnel under high in-situ stress, the problem of large squeezing deformation is often encountered in unfavoured geological conditions consisting of weak surrounding rock mass (Liu and Jiang 2021). There is no good treatment to deal with the large squeezing deformation of the tunnel during construction progress, which continuously leads to disasters in tunnel construction. In tunnel squeezing conditions, the supporting structure of the tunnel is complicated to construct, and the rework after the squeezing incident is time-consuming and labour-intensive. Many scholars tried numerical simulations to grasp the actual squeezing deformation characteristics of the surrounding rock during excavation. Nevertheless, most numerical methods cannot match the field monitoring data due to the subjectivity of the selection of rock mechanics parameters, the uncertainty of surrounding geological conditions, the variability of the construction process, and the limitation of mesh distorting in numerical calculation. Therefore, it is practically essential to capture the mechanical parameters of the surrounding rock mass in tunnel construction based on the field measurement data. |
