Numerical Study of the Long-Term Settlement of Deep Drainage Tunnels in Soft Stratum

The deep tunnel drainage system has been used to solve urban flooding issues recently. However, inadequate research was conducted on the long-term settlement of deep drainage tunnels in soft soils. In this paper, a quasi-static finite element simulation was conducted based on a pipeline model in submerged soft soils. The pipeline suffered from long-term water filling-discharge cycles, which led to the settlement of the underlying soils below the pipeline. Settlements induced by cumulative plastic strain and pore pressure dissipation are isolated. The results reveal that the dissipation-induced settlement is negligible, and a recently proposed cumulative deformation formulation can reasonably predict the settlement. During the whole cycle stages, soil settlements mainly occurred within a certain depth below the pipeline. These findings can provide useful references for designing and safely operating deep tunnel drainage systems in soft soil areas.