Effect on the thermal conductivity inhomogeneity of clay-bearing sandstone subjected to drying-wetting process

Thermal conductivity of rock is one of the important parameters to understand the heat conduction process in interior of the earth. The study of the effect on the thermal conductivity of clay-bearing sandstone subjected to drying-wetting process is of great significance to many geological and underground engineering issues. In this study, the transient hot wire method is used to measure the thermal conductivity of clay-bearing sandstone after drying-wetting treatment, and the thermal inhomogeneity is analyzed. The results indicate that the drying-wetting process leads to the decrease of the average thermal conductivity of clay-bearing sandstone, while the increase of thermal heterogeneity factor. Base on the results of 3D scanning and SEM, it is found that the development of pores and microcracks during the drying-wetting process is the main reason for the average thermal conductivity decreased and the thermal inhomogeneity increased. Further analysis shows that the interaction between clay minerals and water leads to the destruction of rock matrix structure, resulting in the increase of primary pores, the formation of new pores and secondary microcracks in clay-bearing sandstone. In addition, the numerical results show that the pore leads to the significant weakening of rock heat transfer effect, and the temperature field tends to be heterogeneous distribution. The research results can provide reference for the evaluation of thermal conductivity of rock mass in deep engineering.