Multi-scale modeling and simulation of tunnel excavation in sand-gravel strata

Abstract

In sand-gravel strata, the deformation and mechanical behavior of soil mass as well as tunnel structure are mainly controlled by excavation disturbance degree and mesoscopic distribution of soil-rock-mixture in excavation disturbance area. Considering the mesoscopic structure of soil-rock-mixture, a multi-scale analysis approach for tunnel excavation in sand-gravel strata is proposed. Then, three key issues of the method, mainly about the determination of core region and non-core region, the determination of rock size that can be homogenized, equivalent method of soil-rock-mixture, are discussed. The basic thought of the multi-scale analysis approach can be expressed as follows. Firstly, the tunnel excavation model in sand-gravel strata is divided into core region and non-core region. In core region, the soil-rock-mixture is treated as the two-phase composite composed by rock block and soil, while in non-core region, the soil-rock-mixture is viewed as macroscopic homogeneous material. On this basis, the simulation and analysis of tunnel excavation are carried out. From the view of surrounding rock deformation and pressure, the results are compared with meso-analysis model and macro-analysis model of tunnel excavation, and the analysis showed that the simulation results of multi-scale analysis approach are coincidence with meso-analysis model. More importantly, the proposed method greatly reduces the computational work and modeling work, improved the computation efficiency observably.