Impact of mechanical parameter correlations on reliability of stability of underground water-sealed storage caverns

Abstract

The stability of underground water-sealed oil storage (UWSOS) caverns is crucial for ensuring their long-term safe operation. In this study, a reliability analysis method for UWSOS caverns considering correlations between rock mass mechanical parameters was proposed. First, a statistical analysis was conducted on the rock mass mechanical parameters from five large UWSOS caverns projects in China, in which process the mean values, standard deviations, correlation coefficients, and distribution types were obtained. Based on the practical first-order reliability method (FORM), the impacts of parameter correlations on reliability analysis results with regard to the plastic zone and cavern convergence criteria were revealed. And the influence induced by parameter correlations was explained. The study demonstrated that correlations between rock mass mechanical parameters influence the reliability index, with the cohesion–friction angle relationship exhibiting a particularly significant impact. In the analysis based on the plastic zone criteria, a marked reduction in the reliability index is observed as the correlation coefficient between cohesion and friction angle increases. Finally, the reliability of a UWSOS facility in southern China was investigated. Comparative reliability assessments conducted with versus without considering parameter correlations reveal that neglecting such interdependencies leads to conservative reliability estimations. The study provides a valuable insight into the reliability design of UWSOS caverns and facilitates the accurate assessment of engineering risks.