To accurately predict the collapse step distance of mudstone interlayers during cavern leaching and ensure the stability of salt cavern gas storage facilities, this study conducts an in-depth analysis of the structural characteristics and mechanical properties of mudstone interlayers, establishing a predictive model for interlayer fracture. Macroscopic analysis and point load tests on mudstone interlayer samples from Submember 3b of Member 3 of the Buxin Formation in the Sanshui District salt mine revealed the following: (1) the structural characteristics of the mudstone interlayer vary significantly from top to bottom, with the lower section developing multi-angle fractures (partially filled with salt rock), while the upper part remains dense; (2) consequently, the interlayer is categorized into an upper high-strength mudstone and a lower low-strength mudstone, with point load tests confirming that the uniaxial compressive strength of the high-strength mudstone is approximately 5.5 times that of the low-strength mudstone; (3) under brine soaking, the high-strength mudstone exhibits significant softening effects within the initial 14 days, after which its strength tends to stabilize; the long-term strength is primarily influenced by intrinsic interlayer characteristics, such as the proportion of high-strength mudstone and interlayer thickness. Based on these properties, the progressive fracture mechanism of the mudstone interlayer is revealed, which can be divided into three stages: low-strength mudstone fracture, high-strength mudstone fracture, and operational-stage fracture. Ultimately, a fracture distance prediction formula is established that comprehensively considers soaking time and interlayer characteristics (high-strength mudstone proportion and thickness). The study clarifies that: (1) buckling failure occurs in the interlayer when the high-strength mudstone proportion exceeds a critical value (approximately 0.2); (2) when the high-strength mudstone proportion is relatively low, non-buckling failure is more likely to occur. These research findings provide a theoretical basis for predicting and controlling interlayer collapse during the leaching of salt cavern gas storage facilities.
Meng et al. (Thu,) studied this question.