ABSTRACT:

Subjected to long-term mechanical and thermal loads, salt rocks where many Underground Gas Storages (UGS) are excavated usually demonstrate strong time-dependent creep behaviors. In this study, the micro-mechanisms of thermal effect on salt creep behavior is investigated in a discrete element method (DEM) based micro-mechanism system. A novel hybrid model is proposed to describe the thermal-mechanical-creep behavior. This model combines Burger’s model and linear parallel model at the contacts between particles. Creep behavior is described by Burger’s contact model, while thermal transfer is approached by linear parallel contact model via active thermal pipes. The validation of this DEM numerical model is verified by the laboratory creep test, and the model is capable of capturing the development of micro-fractures during creep test subjected to different temperatures. The results indicate that temperature make significant contributions to axial strain rate. The induced thermal cracks account for the higher creep strain rate with elevated temperature in micro-mechanism. Incorporation with creep experiments, the DEM modeling provides an alternative and promising method to explore the micro-mechanical response to temperature influence, can help us improve the understanding of creep behavior of salt rock in UGS during thermal loading.

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