Research On Stability And Destabilization Control Of Rock Salt Cavern

In this paper a systematic research on stability of rock salt cavern in solution mining has been done. The effect on cavern stability by in-situ stress has been analyzed with FEM. The development of cavern destabilization and the stress distribution in surrounding rock are approached by model test on equivalent materials. The large deformation of cavern is studied by FLAC, and meantime, a catastrophic theory is applied to cavern stability analysis, and the cusps model is established.The in-situ stress distribution in surrounding rock of cavern with single and double cavern is analyzed using 3D-Sigma in different depth of mining. The effect of the span of cavern, and the water pressure in cavern on stress in surrounding rock is also studied.The tests on equivalent materials show the developing progress of destabilization in cavern. With the increase of depth and span of cavern, while the peak of stress in surrounding rock and the distance from boundary of cavern increase, the maximum span of cavern declines. When the roof of cavern collapse, there are collapse zone, fracturing zone and bending zone in the upper strata of cavern.The surrounding rock of cavern shows a typical characteristic of large deformation. This characteristic is difficult to be analyzed by the normal method. However with FLAC this problem can be solved. In addition, mechanical reaction on water pressure, large deformation and the dynamical cutting progress can also be analyzed.The stability of single cavern roof is studied by cusp catastrophe model of large deformation circular plate. Thus the necessary condition of destabilization is obtained. The cusp catastrophe of connected well roof is analyzed by beam model considering the level stress contributed by the weight of strata and geological construction. The stability and the mutation mechanism of pillar between two wells are discussed by beam-pillar cusp catastrophe model. The direction and magnitude of in-situ stress greatly affect the stability of cavern. In the double well excavation, especially in hydraulic fracturing connected double well excavation, the line between two well had better be run parallel with the direction of maximum stress. Which is good both for hydraulic fracturing connect and for the stability of caverns.The water pressure in cavern makes the surrounding rock in three-dimensional pressure state, and it is also a good supporter of cavern roof. The higher the pressure in the cavern is, the more stable the cavern. Besides, the water permeated from roof will great affect the strength and stability of cavern. Therefore, keeping a layer of salt to the roof is a good way to prevent water permeation.