A combined support method of isolation pile and diaphragm wall for protection of buildings adjacent to deep foundation pit

The protection of adjacent buildings is an important part of the safety control of the construction of a deep foundation pit in a subway station, and a reasonable supporting method is the key to safety control. Based on the deep foundation pit project of the Nanning Metro Line 5 station in Guangxi, this paper proposes a method of combined support of the isolation pile and the diaphragm wall for the protection of buildings adjacent to the foundation pit. The three-dimensional finite element method is used to simulate the deformation law of the foundation pit adjacent to the building under the combined support during the entire excavation process, and the deformation characteristics of the isolation pile-diaphragm wall are also analyzed. The results show that compared to the diaphragm wall support method, the combined support method effectively limits the soil settlement. The maximum value of soil settlement behind the diaphragm wall is only 0.044%He (He is the excavation depth), and the position of the maximum settlement has moved to the place which far away from adjacent buildings. The maximum deformation value of the combined support method is 59.1% less than that of the diaphragm wall method, and the additional deformation of the building is controlled within 9 mm. The combined support method of isolation pile and underground diaphragm wall proposed in this paper is applied to practical engineering, and the results of field monitoring agree well with the numerical results. Therefore, it is feasible to adopt this support method for the protection of buildings adjacent to the foundation pit.