Based on the actual project, a three-dimensional simulation model is constructed to study the deformation and stress characteristics of the special-shaped soil-rock foundation pit excavation of the suspended pile. By adopting bar demolition method, a strength redundancy expression method based on the ultimate bearing capacity of the inner support is proposed, and two inner support importance evaluation indexes of the associated bar and the correlation coefficient are proposed. The findings indicate: (1) Deformation of special-shaped soil-rock foundation pit with the suspended pile mainly concentrates in the upper soil layers, the position of the positive angle and the middle of the longest side of the foundation pit., achieving a peak value of 17.02 mm. This deformation is linked to the geometric composition and stiffness distribution of the support system itself. Notably, the upper deformation of the supporting structure at the positive corner of the foundation pit is larger, and the influence range is about 2 times that at the negative corner; (2) The strength redundancy based on ultimate bearing capacity can comprehensively and quantitatively evaluate the redundancy of deep foundation pits, where the associated bar can pinpoint which component would be most affected after damage occurs, while the correlation coefficient can, to some extent, reflect critical components within support structures; (3) The redundancy of the inner support based on the ultimate bearing capacity is related to its own load and the arrangement of adjacent support bars. The minimum is 4.18. The associated bar are mainly concentrated in the adjacent bars. In the design of the correlation coefficient, should be optimized to decrease the correlation coefficient of the bar and improve the overall reliability of the support structure.

Hazardous gas migration in rock strata primarily occurs through fractured media, with the stress state of the rock mass significantly influencing its permeability. Generally, natural rock masses are in a triaxial state of unequal principal stresses. Studying rock mass deformation and seepage under various stress states is crucial for accurately predicting gas migration in rock strata. The deformation and permeability of rock mass under fluid-solid coupling were studied by triaxial test system considering different fracture angles and confining pressures. The results show that: (1) The precast fracture strain of rock mass initially decreases and then increases with the increase of axial stress. At confining pressures below 25 MPa, axial stress primarily causes volumetric expansion of the fracture, whereas at pressures above 25 MPa, it primarily leads to volumetric shrinkage. (2) Volumetric expansion of rock masses is primarily due to precast fractures at low confining pressures, and to newly formed fractures at high pressures. The change of rock permeability during compression of precast fractured rock mass is mainly determined by the deformation of precast fracture. (3) When the fracture angle is 90º, 80º, and 70º, the rock mass permeability at peak stress increases by 4% to −0.7%, 0.5% to −6.3%, and −0.2% to −15% compared with the initial stress, respectively, with the increase of confining pressure. The influence of the fracture angle on the permeability of rock mass under axial load is slightly higher than that confining pressure. (4) Considering the influence of different stress levels on fracture deformation, a calculation model for fracture permeability under triaxial state was established. It was found that the sensitivity of the lateral stress influence coefficient on normal deformation χ decreased with the increase of confining pressure and fracture angle.

During the excavation of tunnels in mountainous areas, groundwater may be lost, which affects the surface plants and ecology. In this article, taking Hengwu Tunnel in China as an example, based on the soil–plant–atmosphere continuum (SPAC) model, the relevant parameters were obtained by field test first, and then from the perspective of soil water matrix potential (SWMP) and soil water migration (SWM), the effect of groundwater level decline induced by mountain tunnel excavation on plant growth was studied, and the calculation method of ecological water level was put forward. The results show the following: (1) The wilting of plant roots is a dynamic process of gradual expansion from the middle of the root to both ends, and the response of SWMP in the root region to changes in atmosphere and groundwater level is lagging and non-uniform; (2) SWMP can be used to predict the degree of wilting of plant roots, while the final distribution and value of SWMP are only related to the position of the groundwater level, but not related to the decline rate of the groundwater level; (3) groundwater level and rainfall (P) will affect the value and proportion of each flux in the SPAC model, in which the relative transpiration ratio can be used to evaluate the growth of the plant and calculate the ecological water level of the plant.