Damage Self-Healing Property of Dissolved Salt Columns in Solid Potash Mine

The objective of this work was to investigate the self-healing properties and mechanical damage characteristics of dissolved salt columns under different humidity and time conditions. Based on the results of electron microscope scanning and uniaxial mechanical tests, the microscopic element distribution of the ore and the microscopic morphology of the minerals were investigated, and the healing, mechanical, and damage properties of the specimens were analyzed, which revealed the microscopic reinforcement mechanism of the damage healing of the dissolved salt columns. The results showed that the healing reinforcement, compressive strength, and modulus of elasticity of dissolved salt columns under uniaxial compression show a tendency to increase, then decrease with the increase of humidity, and gradually increase with the increase of the maintenance time and reach the maximum value at 10% humidity and 30 days of maintenance time, which are 3.48, 8.07, and 650 MPa, respectively. The damage type of the healed specimen as a whole gradually transitioned from tensile damage to shear-slip type, indicating that the brittle damage characteristics of the specimen under loading became more and more significant. Based on the principle of strain equivalence, the damage evolution equation under uniaxial compression of solid potash dissolved salt columns describes the damage evolution law and destruction process of the specimen, and the results of the damage characterization of the dissolved salt columns are consistent with the change rule of the healing properties and mechanical properties with humidity and conservation time. Based on the fine morphological features of the dissolved salt column specimens after self-healing, three different self-healing microscopic mechanisms for damage recovery of solid potash dissolved salt columns are summarized, namely, healing of damaged microcracks based on diffusion, recrystallization healing of brine-filled microfractures, and healing adhesion of crystal particles in dissolved zones. These microstructures effectively transform cracks into isolated sections and play a key role in improving mechanical properties. In addition, the higher the humidity, the thicker adsorbed water film is produced on the fissure surface, which accelerates the transportation of materials on the fissure surface, and the healing rate of the dissolved salt columns increases. However, when the humidity is too high, it causes the evaporation of the liquid film to be less than the recharge of water vapor, which reduces the healing rate of the dissolved salt columns. Thus, suitable humidity produces a more pronounced healing effect than an environment maintained at a constant high humidity level. The research results can provide theoretical guidance for the filling mining of solid potassium salt.