Evaluation and Analysis of Seepage Stability in the Surrounding Strata of a Dewatering Foundation Pit Based on Differences in Particle Initiation Conditions

As an intuitive manifestation of the seepage deformation of potentially unstable strata, the seepage failure caused by particle movement is one of the main reasons affecting the safety of foundation pit engineering. Considering the irrationality of the calculation of critical hydraulic conditions in the current study, it is impossible to accurately evaluate the seepage stability of unstable strata in the process of foundation pit dewatering, the research based on a variable cross-section capillary tube model formed by skeletal pores, introduced the effects of relative exposure degree, relative hidden degree and seepage direction. Through the mechanical analysis of particle motion, a theoretical calculation method for the hydraulic conditions of particle initiation along pore channels was proposed, which fully considered the differences in particle initiation conditions. Subsequently, taking the actual project of Mudan Bridge Station foundation pit as an example, the research combined the seepage field distribution during pit dewatering, and the range of moving particle groups in the stratum was divided by calculating the critical hydraulic conditions of particle initiation. Based on this, a new method was developed for quantitatively evaluating and analyzing the seepage stability characteristics of unstable strata, grounded in the theory of particle movement. In the evaluation of the seepage stability of the Mudan Bridge Station foundation pit, it is considered that the station required a dewatering design with a pensile curtain insertion depth greater than 11.0 m, and the subsequent engineering phenomena prove the rationality of the design and the effectiveness of the evaluation method.