A Novel Modeling Approach for Soil and Rock Mixture and Applications in Tunnel Engineering

Abstract

Soil and rock mixtures are complicated geomaterials that are characterized by both continuity and discontinuity. A homogeneous model cannot take into consideration the interactions between rocks and soil, which could lead to misjudgments of the mechanical properties. To simulate the mechanical responses of soil and rock mixtures accurately, a stochastic generation approach to soil and rock mixtures was developed systematically in this study. The proposed approach includes the following three major steps: (1) a combined image filtering technique and multi-threshold binarization method were developed to extract rock block files from raw images. (2) The shapes and sizes of block profiles were controlled and reconstructed randomly using Fourier analysis. (3) A fast-overlapping detection strategy was proposed to allocate the rock blocks efficiently. Finally, models of soil and rock mixtures with a specific rock proportion can be generated. To validate the proposed approach, numerical models were established in tunnel engineering using the conventional homogeneous method and the proposed numerical method, respectively. In addition, a series of field tests on tunnel deformation and stress were conducted. The results showed that the proposed heterogeneous numerical model can model the mechanical response of the soil and rock mixtures well and is much more effective and accurate than the conventional homogeneous approach. Using the proposed numerical approach, the failure mechanism of a tunnel in a soil and rock mixture is discussed, and a reinforcement strategy for the surrounding rocks is proposed. The field tests results indicate that tunnel lining stress can be well controlled within the strength criterion by the proposed reinforcement strategy.