Study on the mechanical and damage properties of laminated limestone under acid mine drainage dissolution

To explore the chemical and mechanical effects of acid mine drainage on water and rock, acid mine drainage (AMD) dissolution tests, triaxial compression tests, and acoustic emission tests were performed on limestone rock samples with different bedding dip angles. Combined with scanning electron microscopy and nuclear magnetic resonance analyses, the changes in the internal pores and surface morphologies of the rock samples before and after dissolution were analyzed. The results were as follows. (1) AMD dissolution mainly occurred in the shallow surfaces and bedding planes of the limestone samples. During dissolution, the shape of the matrix crystal disappeared to form small pores, and residual substances appeared during the dissolution of the bedding plane. These small pores were prone to the creation of large honeycomb-like dissolved pores. (2) With increasing bedding plane angle, the compressive strengths and elastic moduli of the limestone samples exhibited V-shaped distributions. Additional branch cracks were derived from the limestone samples after dissolution, and dissolution reduced the mechanical strength of the limestone by decreasing the crack initiation stress and damage stress. (3) With increasing bedding dip angle, the uniaxial failure modes of the rock samples changed from matrix tensile failure and shear failure along the bedding plane to plane tensile failure. After dissolution, the limestone matrix was prone to cracking and spalling along the surface of the sample. (4) There were differences in the triaxial compression failure modes between the dissolved limestone and the undissolved limestone. When α = 0° or 90°, the limestone samples formed additional branch fissures after dissolution. When α = 45°, the formation of penetrating cracks along the bedding plane was obviously controlled by the bedding plane. (5) A chemical–mechanical damage model was established and modified by the compression coefficient K, which could effectively reflect the deformation of the dissolved rock sample during loading.