18 - Stability of Underground Openings in the Storage of Low and High Temperature Materials

Abstract

This chapter discusses the stability of underground openings in the storage of low- and high-temperature materials and presents the results of an investigation of the physical properties of ice at low temperatures by experiment and simulation, using large-scale calculations. As the temperature distribution changes with time, the stress distribution also changes with time. Before storage of low temperature materials, thermal stress does not occur and only the dead weight of the mountain operates. For an analysis that incorporates the effect of large temperature changes on rock stress, the strength, elastic constants, and thermal properties of rocks at high temperature must be known. Because of storage of heated water, the temperature gradient is high at first; however, it becomes smaller with time, reaching a semisteady state after one year. Permeability is affected greatly by surrounding pressure, seepage pressure and temperature, and only slightly by axial pressure. Rock mass expands toward the circumferential direction, so there can be a decrease of leakage of heated water; however, the deformation reaches a limit with an increase in the number of cracks.