| Summary: | [Objective] In water-rich rock stratum regions, preventing confined aquifer inrush accidents is a key focus and challenge in the design and construction of deep foundation pit projects. Accurately and effectively determining the critical thickness of foundation pit bottom plate is crucial in preventing confined aquifer inrush accidents. Therefore, it is necessary to conduct stability study on foundation pit bottom plate inrush damage problem in confined aquifer. [Method] Based on the nonlinear Mohr-Coulomb failure criterion and considering the influence of various strength parameters and the heterogeneity characteristics of soil layers, a mechanical analysis model for foundation pit bottom plate inrush damage is established. Using the limit equilibrium method, a safety factor calculation formula for bottom plate inrush stability considering the inherent strength of soil layers is proposed. The calculation method for inrush damage in the current technical specifications for foundation pit support is modified. Taking the foundation pit of a utility tunnel project in soft soil layers in Jinan as example, the effectiveness of the proposed modified calculation formula for pit bottom plate inrush stability is validated. Additionally, variations in the safety factor of bottom plate inrush stability under the influence of different soil strength parameters, impermeable layer thickness, and confined water pressure are analyzed. [Result & Conclusion] With the increase in soil cohesion, heterogeneity constant, density, and impermeable layer thickness, the safety factor of pit bottom plate inrush stability continuously increases. Conversely, as the soil nonlinear coefficient, confined water pressure, and foundation pit width increase, the safety factor of pit bottom plate inrush stability continuously decreases. The calculated values of the inrush safety factors considering the influence of soil inherent strength parameters, are generally greater than the values obtained using the current calculation method in the technical specifications for foundation support. The verification using the proposed modified inrush stability calculation formula is more economical.
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