关键词: 含孔灰岩, 分形维数, 裂纹贯通应力, 能量特征, 本构模型

Abstract:

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 numbers and diameters to investigate the peak strength, crack damage behavior, energy characteristics and failure modes under different confining pressures (s₃) and dissolution rates (h). The results indicate that the uniaxial compressive strength and crack damage stress (s_cd) of holed limestone are independent of the dissolution rate (h). Under triaxial compression, the peak strength of holed limestone can be described by a linear Mohr-Coulomb criterion. The cohesion (c) and crack damage ratio (s_cd/s_p) increase with the increase of dissolution rate (h), with the maximum increases being 14.04% and 14.1%, respectively. The peak strength (s_p), frictional angle (f), and energy storage coefficient (K_e) decrease with the increase of dissolution rate (h), 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 holed limestone than the pore number (n). s_p, s_cd, s_cd/s_p, and K_e all increase with increasing confining pressure (s₃). The failure mode of holed 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 holed 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 holed limestone and karst landslides.

Key words: holed limestone, fractal dimension, crack damage stress, energy characteristic, constitutive model