Abstract:

The integrity, deformation and stability of a rock mass are of great importance for the construction of underground crude oil storage caverns with the containment of groundwater. Triaxial compression tests were  performed to determine the properties of the rock mass around a pilot underground crude oil storage cavern. The integrity, deformation and strength of the rock mass were  assessed using elastoplastic theory. According to the test results, it was found that the integrity of rock specimen is destroyed upon the occurrence of volumetric dilation. Therefore, the friction angle at this point could be used to determine the excavation induced loose zone in the construction of underground facilities. In the case of this pilot storage cavern, the extension of the excavation induced loose zone ranged from 0 to 156 m, depending on the buried depth of the caverns. According to numerical simulation results, both the crown settlement and side wall convergence ranged from 8 to 45 mm, and the displacement vectors along cavern walls aligned with the ground surface. There are tensile zones in the cavern floors, and high shear stress zones in the bottom and springline of the cavern sidewalls. The stability of pillars between different caverns is different, as a result of their different stress paths experienced in the excavation.

Key words:  underground crude oil storage caverns, elastoplasticity, excavation induced loose zone, stability, pillar