Analysis of two-dimensional consolidation behavior of soils under cyclic loading considering exacerbated tunnel leakage

Abstract

Post-construction surface settlement can be a significant proportion of the total one, ranging from 30% to 90%. This settlement does not only affect the safety of tunnels, but also causes damage to adjacent buildings and underground infrastructures, posing a number of environmental, geological and geotechnical challenges. This study delves into the consolidation behavior of a soft soil around a circular tunnel, subjected to cyclic loading at the ground level. The Boltzmann growth function is introduced to characterize the exacerbation phenomenon in the lining permeability, while the stress–strain characteristics of the soft soil are described by a generalized Kelvin model. The governing equations for the consolidation of the soft soil around the tunnel are obtained based on the Terzaghi-Rendulic theory, and the dissipation of the excess pore water pressure (EPWP) is investigated. The results indicate that higher load frequencies accelerate the disappearance of cyclic load-induced EPWP fluctuation but, overall, cyclic loading prolongs the consolidation process. The local permeability coefficient predominantly affects the EPWP dissipation in the later consolidation stages. The viscous properties of the soil lead to an incomplete dissipation, and a higher number of Kelvin bodies in the adopted rheological model is associated to a slowdown of the consolidation process. The distribution of the EPWP in the upper part of the tunnel vault is also shown to depend on the ratio between the initial permeability coefficients of the lining and of the soil.