Geomechanical investigation for abandoned salt caverns used for solid waste disposal

Using abandoned salt caverns for the disposal of solid wastes is one of the most effective and safest methods to deal with potential hazards caused both by the abandoned caverns and by the solid wastes. To investigate the geomechanical behavior of abandoned salt caverns used for solid waste disposal (alkali wastes), a discrete-continuous coupled method is proposed. In the proposed method, alkali wastes (discrete materials) are simulated using the discrete element method (DEM) while the caverns are simulated using the finite difference method (FDM). This method can overcome the shortcomings of the traditional method of treating the alkali waste as continuous materials with low strength, which cannot accurately depict the interaction between the cavern and alkali waste. Using the proposed method, a 3D geomechanical model is built to investigate the long-term mechanical behaviors of the cavern and alkali waste. The results show that the alkali wastes have significant effects on reducing the cavern convergence while the cavern convergence compacts the alkali wastes. Consequently, the surface subsidence induced by the convergence of the cavern is much smaller than that of a cavern which does not contain alkali wastes. This study provides a prerequisite to evaluate the effect of filling abandoned salt caverns filled with alkali wastes and also can serve as a reference for stability analysis of gas storage salt caverns that contain insolubles.