The Effects of Fines on the Response of Granular Soil during Earth Pressure Balance (EPB) Shield Tunneling

Abstract

Studying the behavior of surrounding soil in in situ environments during earth pressure balance (EPB) shield tunneling is deemed of great importance, and the discrete element method (DEM) has been commonly adopted for replicating the granular soil and capturing the qualitative behavior of ground response during tunnel advancement. The presence of fines has been proven to affect the soils’ skeleton structures and may dominate their shear strength. However, a significant body of research in tunneling engineering does not often consider sand-fine mixtures, although the natural soil consists of some portions of fines. This numerical study focused on simulating the EPB shield tunneling in granular material containing different fines contents, and the advancement of EPB shield tunneling in the longitudinal direction was reproduced using two-dimensional DEM models. The macroscopic behavior, such as horizontal stress at the tunnel face, and the surface displacement after excavation were investigated. In addition, the micro-mechanical aspect of soil behavior (i.e., contact density) was computed and examined. Finally, the effect of muck discharge rate, which was simulated by deleting the particles within the inlet area, was analyzed.