Soil Behavior in the Earth Pressure Balance (EPB) Shield Tunnelling—A DEM Study

Abstract

The significant shortage of land due to rapid urbanization and population growth has been triggering the development and utilisation of underground space. The shield tunnelling is an increasingly popular alternative to open-cut excavation for underground space development due to its highly efficient and minimal ground disturbance. Conventionally, the performance of tunnelling was evaluated based on laboratory experiments, which are not cost-effective, time demanding, and involving many uncertain variables. Further, this leads to difficulties to measure the earth pressure acting on the cutting face and reproduce the real tunnelling process. Therefore, researchers have been using the discrete element method (DEM) as an alternative tool that can capture the discrete nature of the soil and the soil fabric (affecting the stresses in soil) and simulate their impacts on the tunnelling process. Most DEM studies in the literature have used spheres as representative granular material to reduce computational demands. However, most granular materials, such as sands, are not rounded but possess angularity features; and most DEM studies in tunnelling often ignore the effect of particle angularity. In this study, both the spheres and clustered particles are, therefore, adopted to evaluate the effect of particle shape on the stresses in the soil during the shield tunnelling process. This will provide a better understanding of the evolution of the stress at the interface between the cutterwheel and angular soils.