It is evident that the design of deep foundation pits for underground structure groups in central cities and the safety control of surrounding environments present new development challenges. This study proposes a method for categorizing the critical depth of "deep" and "shallow" foundation pits, clarifies the concept of deep foundation pit engineering systems, emphasizes the scope of environmental safety control, and demonstrates a method for determining the extent of deep foundation pit engineering systems. The overall design approach to deep foundation pits is defined, with constitutive relationships, parameter selection, and scientific verification of soil identified as key technologies for numerical simulation. A comprehensive method and scientific validation approach for parameter selection in numerical models are proposed based on Jinan demonstration city’s parameter system. The integrated design method for deep foundation pits is applied to engineering cases to assess the mechanical properties of existing structures within the (group) system at different excavation stages and actively control their deformation, demonstrating its effectiveness in addressing complex environmental challenges. The overall design approach to deep foundation pits addresses the pressing needs related to “complex environment” and “depth”, utilizing numerical analysis to integrate various media influences such as rock, soil, and underground structures while emphasizing an active principle of “deformation control”, thereby advancing improvements in theory and design methods for deep foundation pits.

To investigate the non-destructive critical slope rate and stability assessment method for strongly weathered rock slopes with soil and highly weathered rock, based on Jinan’s strata, suitable soil layer parameters for numerical simulation are determined. The strength reduction method is then applied to calculate the critical slope rate of the slope, providing reference for construction. The analytical solution for the slope’s safety factor is obtained using the improved Swedish slice method and the slip line field method. These analytical solutions provide essential prerequisties for safety factor applications. Results show that strongly weathered rock experiences failure when the rock strata thickness exceeds half of the slope height or the slope ratio surpasses 1: 0.5. The obtained safety factor from the analytical solution tends to be conservative, contributing to enhanced engineering safety. For soil and strongly weathered rock slope, the research findings help identify the failure area, facilitating the design of support schemes.