The development of underground dissolution leads to the formation of numerous cavities in limestone, thereby affecting the stability of karst mountain. Conventional compression tests were performed on rocks with different hole number and diameters to investigate the peak strength, crack damage behavior, energy characteristics and failure modes under different confining pressures (σ₃) and dissolution rates (η). The results indicate that the uniaxial compressive strength and crack damage stress (σ_cd) of hole-bearing limestone are independent of the dissolution rate (η). Under triaxial compression, the peak strength of hole-bearing limestone can be described by a linear Mohr-Coulomb criterion. The cohesion (c) and crack damage ratio (σ_cd/σ_p) increase with the increase of dissolution rate (η), with the maximum increases being 14.04% and 14.1%, respectively. The peak strength (σ_p), frictional angle (ϕ), and energy storage coefficient (K_e) decrease with the increase of dissolution rate (η), with the maximum decreases being 14.11%, 12.86%, and 9.72%, respectively. At the same dissolution rate, the pore diameter (d) exerts a more significant influence on the variations of various parameters in hole-bearing limestone than the pore number (n). σ_p, σ_cd, σ_cd/σ_p, and K_e all increase with increasing confining pressure (σ₃). The failure mode of hole-bearing limestone is not affected by hole number, and exhibits a conical shear failure without penetrating through the specimen when the hole diameter is greater than 15mm. A fractal damage constitutive model was developed for hole-bearing limestone, and the consistency between theoretical predictions and experimental results substantiates the validity of the proposed model. The concluding remarks can provide a basis for further research on the hole-bearing limestone and karst landslides.

Regarding the safety issues during the excavation process of small radius curved shield tunnels in composite formations of mudstone and backfill soil in Chongqing area, a three-dimensional numerical model was established by Midas. The influencing regularities and sensitivity of curve radius, top thrust force, and unbalanced top thrust force on surface subsidence and surrounding rock deformation were analyzed. The results indicate that: As the radius of the curve increases, the deformation gradually decreases, but the magnitude of the deformation is gentle. There is a critical value for the top thrust, which can cause instability of the palm surface if it is too low, and shear failure of the soil if it is too high. An increase in the proportion of unbalanced thrust will disrupt stress symmetry, and the synergistic effect of soil loss on the weak thrust side and compression on the strong thrust side will exacerbate asymmetric settlement. Sensitivity analysis shows that top thrust plays a dominant role in deformation control, followed by curve radius and unbalanced top thrust. The research results can provide reference for optimizing construction parameters of small radius curved tunnels under similar geological conditions.