FLAC(3D) software is used to establish numerical simulation model of soil nailing wall based on the basic parameters and dimensions of the model obtained from the physical model of soil nailing wall destructive test. The excavation and supporting process of the foundation pit are simulated by the numerical model, the horizontal displacement along the depth direction of the wall and the axial force of each layer soil nailing as well as the relationships between them are monitored. After the supporting process, vertical loading are exerted on the coping until large deformation of the wall appears in order to study the working conditions and the damage process of the soil nailing wall under the overload conditions, then compared with the results from the destructive test of the physical model for soil nailing wall. The study results show that the bottom horizontal displacement of the wall during the excavation stage is larger than at top, and in a spoon-shaped distribution; soil nailing axial force in the vicinity of maximum horizontal displacement of the wall is also the largest. If deformation of silty sand soil nailing wall is more than 4 % of excavation depth, the stability of the wall would reduce greatly. When there is no soft substratum under the silty sand soil nailing wall, under the overload on the ground, the destruction form is the damage in the wall, and shows that a part of the soil slids down along the slip face.
