Coupled Elasto-Plasto-Damage Mechanism And Its Influence On Dissolving Property Of Rock Salt

The stability of the wall rock, depositing energy sources in the rock salt, is the principle problem during the construction of salt cavern. The main factors affecting the stability of the wall rock are: the mechanical property, permeability and dissolving property of rock salt . The factors mentioned above always couple with each other. Former researchers have done much work on the problem, but many aspects are still unsolved. The deformation and failure character of rock salt is very different from other rocks. The basic feature of rock salt is the coupled phenomenon of damage with plastic mechanism and the feature is very important when analyzing the stability of salt cavern. However, the present research on the coupled phenomenon is not sufficient and a mechanical model is needed to describe the phenomenon. As for the dissolving property of rock salt, from the result of experiments, we can see that the character changes under different stress conditions. The former work is done mainly under the condition without stress or uniaxial compression stress, but those conditions are quite different from the actual situation, which can't reflect the effct of deformation and failure for the dissolving property of rock salt under complex stress state. Aiming at above problems, based on a lot of conventional uniaxial and triaxial compression testes and meso-mechanical experiments of rock salt, the coupled elasto-plasto-damage mechanism is studied and a coupled elasto-plasto-damage is established. The dissolving property of rock salt under different stress conditions is studied through the comparison of the result of dissolving experiments with stress and without stress. The mechanism of the effect of stress on the dissolving is analyzed. Together with the coupled mechanical model, a dissolving model of rock salt is established.The main conclusions of this thesis are:1: The mechanical property of rock salt is analyzed based on the conventional triaxial compression testes and meso-mechanical experiments. We find that the elastic-plastic is coupling with damage. Through the phenomenon in the experiments and by taking the coupled character of elastic-plastic and damage into consideration, the failure mechanism of rock salt is studied and an elastic-plastic-damage coupled mechanical model is proposed to capture the deformation of rock salt. The model is verified by comparing the simulating result with the experiment result.2: Based on the analysis on dissolving mechanism of rock salt without stress, a quantitative relation of the dissolving quality with the solution concentration and dissolving time is proposed. Then, a dissolving model of rock salt without stress is established and the diffusion coefficient is calculated by using the dissolving experiment result under the condition without stress.3: Through many dissolving experiments under different stress conditions, we find that the dissolving character of rock salt is influenced by stress.The relation of dissolving quality with confining stress, plastic volume strain and dissolving time is put forwarded. The dissolving character under different stress conditions is studied and found that the dissolving rate is related to the cracks on the surface caused by stress. Then, by study the initiation and propagation of cracks, we can get the dissolving rate under different stress.4: Based on the dissolving model which takes no account of the influence of stress and combined with the elastic-plastic-damage coupled mechanical model, a modified dissolving model is proposed by using the equivalent diffusive coefficient. A program is used to calculate the equivalent diffusive coefficient D^*, and the relation of D^* /D with confining stressσ₃, plastic volume strainε_v^p and dissolving time t isproposed, where D is the actual diffusive coefficient.