(1. State Key Laboratory of Hydraulic Engineering Simulation and Safety，Tianjin University，Tianjin 300350，China；
2. Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization，
Shenzhen University，Shenzhen，Guangdong 518060，China；3. Institute of Rock Instability and Seismicity Research，
Dalian University of Technology，Dalian，Liaoning 116081，China；4. China Railway 25th Bureau Group Fifth
Engineering Corporation Ltd.，Qingdao，Shandong 266000，China；5. Guiyang Investigation，Design and
Research Institute，State Power Corporation of China，Guiyang，Guizhou 550081，China)
Abstract：In the process of reservoir construction and management，the rock would be under an alternating state of drying-wetting owing to the seasonal rainfall and storage and drainage of the reservoir. In addition，the rock is commonly subjected to dynamic loadings such as earthquake，blasting，and tunneling，which have significant influences on the stability of the reservoir. To investigate the effect of drying-wetting cycles and dynamic compression on the mechanical behaviors of rocks，the dynamic test of sandstone undergoing different drying-wetting cycles was carried out using the split Hopkinson pressure bar system. The influences of wetting and drying cycle conditions on the rock dynamic characteristics，energy dissipation law，and fractal dimension of fragmentation were systematically analyzed. The microstructure of sandstone was observed using the scanning electron microscope to reveal the physical deterioration mechanism. The results show that drying-wetting cycles would weaken the ultrasonic characteristics，static and dynamic mechanical characteristics of sandstone. With the increase of drying-wetting cycles，the static uniaxial compressive strength，elastic modulus，P-wave velocity，dynamic compressive strength，dynamic elastic modulus，and dissipative energy of sandstone decrease，while the fractal dimension of rock fragmentation increases. In addition，with increasing strain rate，the dynamic compressive strength，elastic modulus，peak strain，dissipative energy，and fragmentation fractal dimension of sandstone show an increasing trend. The macroscopic analysis results illustrate that the deterioration of sandstone under drying-wetting cycles is caused by the significant change in microstructures，i.e.，pores increasing，particle breakage，cementation weakening，and crack spacing expanding. The research findings in this study could provide a theoretical basis for the design and construction of reservoir de-risking and reinforcement under drying-wetting cycles.
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2023, Vol. 42 
