[Geotechnical Engineering]

Zhang, Z. Y., Jin, X. G., Luo, W. Numerical study on the collapse behaviors of shallow tunnel faces under open-face excavation condition using mesh-free method[J]. Journal of Engineering Mechanics-ASCE, 2019, 145(11): 04019085.

Keywords: Face stability, Shallow tunnels, Open-face excavation, Softening effect,

Numerical simulation

Abstract:

The stability and deformation of shallow tunnel faces are hard to predict, and the associated failure mechanism is also indistinct to date. In this work, we incorporate softening function and strain-dependent dilation model into Smoothed Particles Hydrodynamics (SPH) framework to simulate the collapse behaviors of shallow tunnel faces in cohesive-frictional soils under open-face excavation condition. To this end, the stratum is modeled as a cohesive-frictional soil described by elasto-plastic constitutive model in combination with the Drucker-Prager yield criterion. Softening and strain-dependent dilation behaviors of soils are described by the softening function and the dilation model, which are incorporated into the constitutive model in the framework of SPH method. For the deformation analysis, the effects of the cover depth variation on face extrusion and ground surface subsidence are investigated. For the face stability analysis, the impacts of the cohesion and the internal frictional angle of surrounding soils on the safety factor of shallow tunnel faces are highlighted. Then, comparison is made between the results obtained from present SPH method and those given by the Finite Element Method (FEM) and existing centrifuge model tests, to verify the proposed SPH procedure. Ultimately, the main outcomes of current work, including deformation feature and safety factors of shallow tunnel faces, are presented.