Study on the mechanism of roof collapse and leakage of horizontal cavern in thinly bedded salt rocks

In the thinly bedded salt formations, due to the limited thickness of the salt strata along with the fast upward dissolution, the collapse of the non-salt roof of the cavern often occurs, leading to the leakage of brine and instability of the cavern as well as other undesirable geological consequences. To investigate the gypsum-salt interbedded roof collapse, the failure mechanism and the control methods of Dainan siltstone, which is the indirect roof of the horizontal salt caverns in Zhaoji Salt Mine, were thoroughly investigated. Through the drilled cores from this mine, a series of contrast tests such as SEM, EDS, XRD, soaking, and nuclear magnetic properties were carried out to study the physical properties of the salt layer and non-salt layer of the cavern roof and to determine the cavern roof collapse and leakage mechanism. Using the Comsol software, the model of a horizontal cavern roof leakage was established, and the leakage range and leakage of brine at different time were analyzed, as well as the safety problems caused by it. Finally, some suggestions have been provided for the leakage control of the cavern roof in bedded salt cavern.