Abstract: In this paper, the excavation process of a deep excavation supporting project in the soft soils was investigated by using the strength reduction method. The influence of the embedded depth and the shear strength change of the deep excavation supporting structure on the uplift instability is also studied. The analysis results are compared with the results from Terzaghi foundation bearing capacity and Prandtl foundation bearing capacity estimation methods. The results show that: (1) with the increase of the insertion ratio D / h of the supporting structure, the factor of safety against the uplift stability in deep excavation also increases gradually, but the improvement of the factor of safety of the against the uplift failure is limited; (2) with the decrease of the shear strength of the soft soil, the uplift stability factor of safety in the deep excavation decreases nonlinearly; (3) the analytical results based on Terzaghi and Prandtl models are larger than the results from the strength reduction method, which overestimates the uplift resistance against the soft soil stability.

Key words: strength reduction method, deep excavation, soft clay, basal stability