Poroelastic properties play an essential role in interaction between deformation and fluid pressure change in porous materials. These properties are inherently related to microstructural evolutions such as porosity change and micro-cracks growth. In this study, the evolutions of poroelastic properties of a hard rock (granite) are investigated in terms of thermal micro-cracking process. Granite samples are first subjected to a heating-cooling treatment with different values of temperature. The evolutions of poroelastic properties (bulk modulus of porous skeleton, compressibility modulus of solid matrix, Biot’s coefficient) of treated samples are analyzed in terms of micro-cracks induced by the heating-cooling treatment. It is found that both connected and occluded micro-cracks are generated in granite samples. The bulk modulus of porous skeleton is affected by the connected micro-cracks while the compressibility modulus of solid matrix is influenced by the occluded micro-cracks. Biot’s coefficient is affected by the connectivity of micro-cracks.

Clogging caused by grain migration during groundwater recharge is a critical problem for long-term operation period of Ground water-source heat pump (GWHP), especially for uncemented sandstone reservoir. Thus, the permeability tests of three groups of uncemented sandstone samples with different grain compositions are carried out respectively, under in-situ stress. The clogging caused by coupling effect of in-situ stress and grain-migration during groundwater recharge for uncemented sandstone. Firstly, the original grains are crushed even broken into fine grain under in-situ stress. Then, the fine grains originally filled or secondary crushed migrate along the space between skeleton structure and gradually deposit at the bottom of samples, resulting in the increase in pore pressure and the decrease in apparent permeability, which is in good agreement with the observations in the field. Apparent permeability exhibits different variation duo to the differences in grain composition, whilst the absolute permeability decreases with the increased grain size due to the compaction effect or/and the grain migration. Furthermore, the pore pressure increases with flow rate and tends to 1/2 of applied hydrostatic stress till the failure of samples. This indicates in-situ stress and pore pressure are key factors controlling the failure of uncemented sandstone, but excluding grain composition. The testing results in this context could facilitate our understanding of the clogging caused by coupling effect of in-situ stress and grain-migration during groundwater recharge for uncemented sandstone, and some suggestions could be provided for the utilization of hydrothermal geothermal energy especially for the uncemented sandstone reservoir.