Shield Tunneling-Induced Disturbance in Soft Soil

Abstract

The various forces applied to soil during shield tunneling will inevitably disturb the adjacent soft soil, inducing increased soil settlement after tunneling and endangering the service performance of the tunnel. However, the disturbance degree and distribution of the soil under the tunnel have not previously been measured in situ. The contributions of different tunneling parameters to disturbance are also not well understood. In this paper, cone penetration tests were carried out before and after shield tunneling to evaluate the disturbance degree and distribution of soil under the tunnel. The shear strain of soil was also obtained via back-analysis of tunneling with the finite element method. It was found that the shear strain was linearly related to soil disturbance degree. Furthermore, face pressure, contraction, and grouting pressure were parametrically studied to determine their relative contributions to soil disturbance. The results revealed that face pressure contributed the most to the soil disturbance. This study will be useful for evaluations of soil disturbance induced by shield tunneling and for controlling soil disturbance and post-construction tunnel settlement during tunnel construction.

Keywords: Soil disturbance, cone penetration test, back analysis, shield tunneling, Soft soil