Microstructure and mechanical characteristics of sandstone under long-term water immersion

ObjectiveIn the process of reservoir storage, some rock mass on the reservoir bank is in a state of long-term water immersion. In addition, the rock mass in this area is also subjected to frequent blasting dynamic loads, thereby inducing landslide instability. Based on this, this study aims to reveal the effects of dynamic loading and long-term water immersion on the microstructure and mechanical behavior of sandstone. MethodsThis study first immersed sandstone in water for 0, 4, 40, 80, and 150 days, and then carried out microscopic and impact tests on sandstone using nuclear magnetic resonance (NMR), scanning electron microscope, and an improved Hopkinson pressure bar test system. The microscopic changes of sandstone under dynamic loading and long-term water immersion were investigated, and the strength degradation mechanism of sandstone under long-term water immersion was explored. ResultsThe results showed that the pore distribution ratio of micropores decreased with the increase of soaking time, while the pore distribution ratio of mesopores and macropores increased gradually, and the total signal amplitude of the samples decreased first and then increased. The soaking time was proportional to the total dissolved solid content in the soaking solution, which indicated that the minerals in the sandstone continued to dissolve and a series of physical and chemical reactions occurred during the soaking process. With the extension of soaking time, the pH value of the soaking solution increased first and then decreased. The greater the dynamic load, the greater the peak stress of sandstone, whereas the longer the soaking time, the smaller the peak stress of sandstone. The dynamic load is positively correlated with the incident energy and absorbed energy of sandstone, whereas the soaking time had little effect on the incident energy of sandstone. ConclusionThis study can provide a theoretical basis for the stability rating of reservoir landslides and the construction of underground reservoirs.