Exploring the influence of fabric anisotropy on the active failure of shield tunnel through DEM

Abstract

Fabric anisotropy significantly influences the mechanical behavior of sandy soils, potentially resulting in diverse failure patterns during shield tunneling owing to insufficient support pressure. In this paper, a set of specimens with bedding angles (\(\alpha\)) and an isotropic specimen are well generated to simulate active failure at the tunnel face using DEM. The evolving failure of the soil in distinct \(\alpha\) are scrutinized, and ground settlement is further explored. Furthermore, microscopic information is juxtaposed to systematically elucidate the influence of \(\alpha\) on failure patterns at a microscopic level. Macroscopic findings reveal that, aside from specimens with \(\alpha\) = 0° and 90°, particle displacement experiences deflection as it extends toward the ground surface in other specimens. However, this deflection behavior is only noticeable under conditions of large deformation. Additionally, across all specimens, the maximum displacement of the ground surface is observed in those with \(\alpha\) = 90°, while the minimum value is noted in specimens with \(\alpha\) = 45°. Notably, considerable particle rotation occurs within the shear face. However, the deflection behavior has not been found in specimens with \(\alpha\) = 0° and 90°. Similarly, in specimens with these two specimens, there is no noteworthy deflection observed in the principal direction of contact normal.