Analyzing Creep Behavior of Storage Caverns in Weak Rocks.

Understanding the time-dependent behavior of the rock mass is crucial to improve the reliability of underground structure design, particularly for projects with longer lifespans, such as nuclear waste repositories and hydrocarbon storage tanks. Creep is a time-dependent mechanism that plays a significant role in such designs but is often overlooked. Hence, a comprehensive study of the non-linear viscoelastic response of caverns over extended periods is needed to assess cavern closure under various scenarios. Therefore, this study investigates the time-dependent behavior of caverns constructed in rock-salt and shale rock using a finite element (FE) approach. The analysis was performed by the ABAQUS CAE tool, focusing on an axisymmetric approach. The time-dependent deformation behavior of the rocks was simulated using the Power-Law creep model. Furthermore, a parametric study was carried out to evaluate the influence of overburden depth, shape, volume, and time on the long-term behavior of caverns. The analysis revealed that the excavation of caverns in rock salt resulted in minimal displacements compared to that of shale rock. The results suggested inward displacement at the crown and wall of the cavern, with uplift found at the heel. Furthermore, the augmentation in the volume of the cavern and the depth of the overburden resulted in an enhanced displacement at the wall, crown, and heel of the cavern. Further, the examination of several cavern shapes revealed that spherical caverns show the least displacement compared to cylindrical and horseshoe-shaped caverns. Additionally, the normalized graphs were developed using normalized displacement, rock mass density, overburden depth, and Young's modulus as the basis. Engineers and designers can use these graphs as a useful tool to evaluate the long-term behavior of caverns and make well-informed judgments during the planning stage. Overall, this study contributes to safer and more reliable engineering practices in cavern construction and maintenance by offering insightful information about the time-dependent behavior of rock mass and useful suggestions for enhancing the stability and design of underground structures. [ABSTRACT FROM AUTHOR]