ASSESSMENT OF PERFORMANCE OF AN UNDERGROUND CRUDE OIL STORAGE CAVERNS SUBJECTED TO CYCLIC LOADING DUE TO STORAGE AND EXTRACTION OF CRUDE OIL IN OPERATION PHASE
The stability and containment properties of an underground crude oil storage cavern, the first underground oil storage cavern in hard rock in China, were investigated using theoretical analysis and numerical simulation. Based on the conventional kinematic hardening fatigue model, a constitutive model was proposed to describe the fatigue behavior of rocks. In the model, the influence of mean stress on the fatigue behavior of rocks was taken into consideration. The model was embedded into a finite element code as a user subroutine to assess the performance of the cavern in operation and subjected to a cyclic loading due to storage and extraction of crude oil. Two representative cases were simulated to investigate the performance of the caverns in operation. One is synchronous storage and extraction for neighboring caverns, while the other is asynchronous storage and extraction. It was found that the crown settlements of caverns for synchronous storage and extraction are higher than those for asynchronous storage and extraction, while the horizontal convergences for asynchronous storage and extraction are higher than that for synchronous storage and extraction. For asynchronous storage and extraction, the groundwater table drawdown and inflow are higher than those for synchronous storage and extraction. However, the stability and containment properties of the cavern maintain well during the operation period.