Effects of cyclic heating and LN2-cooling on the physical and mechanical properties of granite

By Xiaoguang Wu, Zhongwei Huang, Zhenhua Cheng, Shikun Zhang, Hengyu Song, Xin Zhao. Applied Thermal Engineering, 2019

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Abstract This paper is aimed at studying the effect of cyclic heating and liquid nitrogen (LN2) cooling on physical and mechanical properties of granite, which is a critical concern for the engineering application of cyclic LN2 fracturing technique in HDR geothermal. In the current paper, we tested the physical and mechanical properties of granites subjected to different heating and LN2-cooling cycles and analyzed the influence of heating temperature during the cycles. Fine-grained and medium-grained granites were compared to determine the influence of grain size on rock responses to thermal cycles. Furthermore, we also developed an improved deterioration model to describe the integrity loss of granite during the cycles. The experimental results indicate the heating and LN2-cooling cycles can aggravate granite damage, making the permeability growth and mechanical deterioration more pronounced. Nevertheless, the damage of granite mainly occurs in the initial few cycles. After about 10 cycles, changes in physical and mechanical becomes less pronounced. The higher heating temperature in the cycles contributes to improving the decay rate and intensifying damage of granite. Additionally, rock particle size has a great impact on the physical and mechanical responses of granite. Granites with smaller particle size are more sensitive to the heating and LN2-cooling cycles.

Subfields: Environmental Engineering, Mechanics of Materials, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/64cb3191c552bf68550feda84ebd77a203bb5e9d