Abstract: The deformation control is a priority in foundation pit support design to effectively avoid safety risk of adjacent metro tunnel caused by excessive deformation of deep foundation pit. The deep foundation pit slope on the side of the metro tunnel near Chongqing Wuyue Square is taken as an example, a scheme of grouting reinforcement combined with multipile stepbystep support is proposed, in which the structural stress is rational and the deformation control capacity is strong. The test data of the onsite grouting test area show that the shear strength and deformation modulus of the soil after reinforcement have been greatly improved. The displacement and internal force values of multistage retaining piles and tunnels under two working conditions with and without grouting reinforcement are calculated by finite element model. It is concluded that the soil filling grouting reinforcement can effectively improve the mechanical properties of the soil before and after the retaining pile,  increase the shear strength parameters and the proportional coefficient of the horizontal resistance coefficient of the soil, and reduce the internal force of the retaining pile, the length and crosssection size of the pile body. The multistage platform is set in combination with the building retreat scheme, which increases the horizontal distance between the slope foot and the slope top, and reduces the soil pressure value of each step slope. The grouting and multistage platform play a positive role in controlling the support pile and tunnel deformation, effectively avoid the safety risks caused by excessive deformation of the foundation pit slope on the metro tunnel and the surrounding environment.

Key words:  soil filled foundation pit slope, metro tunnel, grouting reinforcement, stepped support, numerical analysis