Abstract: Two soil constitutive models with different hypothesis are selected:H-S model and M-C model, and the stability analysis of deep foundation pits in loess area is performed by means of finite element software PLAXIS, and compared with the calculation results of the slicing method. The following conclusions are summarized: since the H-S model exhibits harder than M-C model in the case of unloading, so that it will better reflect its better uprightability and higher strength of the loess, the resulting safety factor is higher, which will be more suitable for the stability analysis of foundation pits in loess areas; the construction of prestressed anchor will change the displacement field and stress field of the soil, making the potential slip facing the depth of soil and significantly increasing the stability coefficient of the foundation pit, and greatly contributing to the stability of the foundation pit; the strength reduction method will have a strong advantage over the conventional strip method. It will not need to divide the soil strip and assume the force and moment among the strips. The direct reduction of soil parameters will be more in line with the actual situation, and the resulting safety factor will be more accurate and can better reflect the formation process of the soil slip surface.

Key words: deep foundation pit, pile anchor support, constitutive model, strength reduction method