Affected by dip angle and thickness of strata and the tunneling method, soft rock tunnel has obvious characteristics of large deformation, long deformation time and difficult support. Based on a case study of Gelong the deformation and failure mechanism of surrounding rock, stress characteristics of supporting structural and control method of large section highway tunnel passing through strong-medium weathered carbonaceous slate stratum are studied. This paper proposed construction method based on strengthening the longitudinal stiffness of supporting structure and increasing the integrity of surrounding rock, The results showed that the deformation of surrounding rock and the stress of supporting structure increased rapidly in the early stage of construction. The cumulative deformation of vault settlement and horizontal convergence reached 116.9 mm and 97.9 mm, respectively, accounting for 73.53% and 76.62% of the total deformation. The proportion of surrounding rock pressure shared by the primary support and the secondary lining was about 8.9:1.1. This shows that the initial support after comprehensive reinforcement has a strong supporting capacity, and effectively reduces the secondary lining pressure of the tunnel, which plays a vital role in the long-term service of the secondary lining.

The coupled seepage–stress action has a significant deterioration effect on the structural face of the hydraulic tunnel enclosure, which intensifies the shear rupture tendency of the deteriorated structural face of the rock mass. The plastic deformation of a typical I–II composite fissure was taken as the research object, the characteristics of the tip plastic zone of the composite fissure seepage rock were explored, and the influence law of osmotic pressure and fissure rock parameters (fissure dip angle, Poisson’s ratio, and fissure length) on the radius of the tip plastic zone was analyzed. Based on the Drucker–Prager yield criterion and the stress intensity factor of the composite fracture, the theoretical analytical formula of the fracture plastic zone radius under the action of high and low osmotic pressure was established, and the fracture rock plastic zone radius was significantly correlated with the fracture parameters. The radius of the plastic zone of fracture under low osmotic pressure evolves in a trend of decreasing–increasing–decreasing with the increase in fracture dip angle, and the peak radius of the plastic zone appears at 45°. Poisson’s ratio and fracture length have less influence on the radius of the plastic zone. The radius of the plastic zone of fracture under high osmotic pressure grows in an incremental nonlinear curve, and the peak radius of the plastic zone appears at 90°, being positively correlated with the length of fracture. This study can provide theoretical reference for the analysis of the stability of the surrounding rock in hydraulic tunnels.

Reliable prediction of tunnelling-induced ground deformation is essential for assessing differential settlement of surface buildings and deformation of subsurface structures in densely built urban areas. This study establishes a multi-source engineering-evidence framework for parameter selection in the modified Peck model. An interval database containing 39 published correction-coefficient records is compiled to investigate the maximum-settlement correction coefficient α and settlement-trough-width correction coefficient β, while an independent dataset comprising 24 international shield-tunnelling cases and 84 surface and subsurface observations is used to evaluate depth-dependent settlement characteristics. Descriptive statistics, the Mann–Whitney U test, Cliff’s δ, bootstrap resampling, interval Monte Carlo simulation, and case-level trend analysis are employed. The median values α are 0.650 for soft soil and 0.550 for composite strata. Although the difference is not statistically significant (p=0.150,δ=0.302), interval Monte Carlo analysis gives a probability of 0.907 that the median α is higher in soft soil, indicating a directional ground-condition dependence. In contrast, β shows substantial between-group overlap and no robust ground-condition dependence. With increasing normalized observation depth z/T, i(z)/i(0) decreases strongly (ρ=-0.898), whereas S_max(z)/S_max(0) generally increases, with consistent within-case trends in 17/17 and 20/22 cases, respectively. The results support treating α as a ground-conditioned prior and β as an updateable project-specific parameter rather than prescribing either as a fixed constant. The proposed framework provides a transparent basis for settlement assessment of the built environment and highlights the need for depth-dependent corrections when subsurface structures are involved.