Research on anchoring effect and failure mechanism of hard interlayers in the cavern pillar of underground gas storage in bedded salt formations

Abstract

The stability and tightness of pillars are the key to ensure the safe operation of the salt cavern group for underground gas storage (UGS). Even in the case of a wide pillar, the hard interlayer in the center of the pillar may still produce plastic collapse early in the operation. In this research, referring to the mechanism of full-length grouting-bonded bolts and surrounding rock, it is speculated that there is a similar effect between hard interlayer and rock salt in the pillar. After analyzing the distribution law of shear stress at the interface and the distribution of additional radial stress in hard interlayer, it is concluded that the hard interlayer has an anchoring effect on the pillar, and the surrounding rock salt has a tensile force on the hard interlayer. The pulling effect on the hard interlayer reduces the radial stress in the center of the pillar, which is the direct cause of the plastic collapse here. Finally, through the above -mentioned research, it can be concluded that the hard interlayer in the center of the pillar can be prevented from being damaged or even penetrated by two ways: arranging the interlayer far from the center of the cavern and avoiding the interlayer being too thin.