Numerical Simulation and Field Monitoring of Deformation Characteristics of TRD Composite Supporting Structure for Deep Foundation Pit in Quaternary Stratum: A Case Study in Qingdao

Trench cutting re-mixing deep wall method (TRD) is an increasingly common method for building waterproof curtains in deep foundation pits. By combining numerical simulations and field monitoring, this study investigated the deformation characteristics of the TRD cement soil mixing wall and soil surrounding the foundation pit. By considering the effect of the discreteness of the TRD cement soil mixing wall’s mechanical properties on the excavation stability under different stratigraphic conditions, the mechanical model of the TRD composite supporting structure was established using FLAC^3D to simulate the foundation pit excavation process. In addition, field excavation monitoring was performed and compared with simulation results. The results revealed that the lateral deformation of the TRD cement soil mixing wall obtained by simulation was accurate, although the peripheral ground settlement was slightly smaller than the measured value. The maximum lateral deformation of the TRD cement soil mixing wall is positively correlated to the excavation depth. The maximum settlement value of the surface gradually increased as the construction stages progressed. As the distance from the enclosure grew, the settlement value first increased and then decreased. In the same construction stage, the TRD cement soil mixing wall shear stress increased with the depth and was maximum close to the excavation face of each step. Therefore, the design should fully consider the influence of a sudden force change caused by soil excavation on the TRD cement soil mixing wall.