Mechanical Properties and Energy Evolution Characteristics of karst Limestone with Different Degree of Dissolution under Uniaxial Compression

Under the action of dissolution, rock masses form solution fissure leading to changes in their internal structure, which in turn affect their engineering mechanical properties and failure characteristics. Karst rock masses usually have a significant impact on the stability of tunnel surrounding rocks in karst stratum. This article utilizes digital image processing technology and particle flow discrete element method to numerically reconstruct calculation models of limestone with different degree of dissolution. A series of uniaxial compression discrete element numerical experiments were conducted on karst limestone with different degree of dissolution, analyzing the stress-strain relationship, mechanical parameters, failure modes, and energy changes of limestone with different degree of dissolution. Research results indicated the following: (1) The karst limestone model constructed based on digital image processing technology can effectively characterize the dissolution features of karst limestone, and numerical simulation experiments can effectively characterize the mechanical behavior of karst limestone. (2) As the degree of dissolution increases, the stress-strain curve of karst limestone gradually exhibits bimodal or multimodal characteristics, and the uniaxial compressive strength of karst limestone shows an exponential decrease trend, while the elastic modulus shows a linear decrease trend. (3) Under high degree of dissolution, the existence of pore structure causes the stress skeleton inside the karst limestone to be damaged, and the number of shear and tensile cracks is continuously decreasing. The distribution of internal force chains is dispersed, making the karst limestone more prone to failure. (4) During the process of karst limestone failure, most of the input total strain energy is first converted into elastic strain energy, and only a small portion is converted into dissipative strain energy. The increase in the degree of dissolution significantly reduces the total energy input and the storage limit of elastic strain energy during the uniaxial compression failure process of karst limestone, and increases the degree of strain energy dissipation.