Influence of structure type of underground gas storage cavern on stability of surrounding rocks

Abstract

Underground gas storage is an important guarantee for the national energy strategic reserve, and its construction is being accelerated. The stability of surrounding rock during the construction of Underground Gas Storage (UGS) cavern is the key factor determining the feasibility of gas storage. As a case study, research was performed to a single UGS cavern. Specifically, the influence law of different surrounding rock conditions, different depth-span ratios and different buried depths on the stability of surrounding rocks during excavation of UGS cavern with large section was studied by establishing a three-dimensional finite element model based on the rock yield process and plastic flow rule. The results indicate that the deformation of surrounding rocks of cavern increases exponentially with the reduction of surrounding rock grade after excavation, and the plastic zone also increases gradually. Besides, the deformation of surrounding rocks of the cavern increases with the increasing of the buried depth, and the surrounding rock deformation at the waist of cavern increases exponentially. The maximum vertical deformation of surrounding rocks decreases generally with the increasing of depth-span ratio, while its maximum horizontal deformation increases with the increasing of depth-span ratio. Moreover, the gas storage cavern should be constructed in the area with good conditions such as grade Ⅱ and grade Ⅲ surrounding rocks within the buried depth of 200 m, and the surrounding rock is more stable when the depth-span ratio of the cavern is 2.5 to 3.0. In general, the research results could provide reference for the structural design of UGS cavern with large section.

Keywords

• underground gas storage
• large cross section
• stability of surrounding rock
• structure type
• finite element simulation