Combined with a foundation pit in kunming, the paper use the finite-difference software flac3d to establish engineering model and carry on the numerical simulation to simulate the excavation on the initial engineering condition of the double-row piles retaining structure. Summarize the calculation results when change the distance of the pile-rows and the length of the piles to analyze the results differences and changing law. The conclusion has some practical value in engineering.

Cantilever retaining structure is often applied to shallow foundation pit supporting, but it causes large deformation in soft soil region. Reinforcement of soil can solve this problem, and a finite element model of foundation pit which based on elastic fulcrum method is founded to research the regular pattern how the depth and degree of soil reinforcement effects the deformation and the inner force of the cantilever retaining structure. The result shows that the lateral deformation reduces with the increases of the depth and degree of soil reinforcement, and critical depth and degree of reinforcement can been founded. The change of inner force caused by depth and degree of soil reinforcementis small. So it is important to reasonably decide the depth and degree of soil reinforcement.

To study the influence of active earth pressure caused by the ditch after retaining wall, we will treat the ditch as unloading, and use the resolve of uniformly distributed load on half-infinite plane boundary to get the calculation method to get the influence of active earth pressure caused by the ditch after retaining wall. At last, from an example, we will get the picture of active earth pressure caused by the ditch after retaining wall, and analysis the regular pattern and characteristics.