Underlying mechanism behind the dynamic mechanical behavior of sandstone with varying moisture content under medium...

Due to the long-term effects of water erosion and stress disturbance, the rock characteristics and pressure distribution of underground coal mine reservoirs will change, affecting the stability of the dam body. Therefore, the mechanical properties of rock under different water content and impact load are the key factors affecting the stability of the surrounding rock. In this paper, the quantitative relationship between dynamic compressive strength, strain, and fractal dimension of coarse sandstone and fine sandstone under different water content were studied by drop weight impact tests. The water content of sandstone can affect its mechanical properties. The dynamic compressive strength of sandstone is lower than the original state after being immersed in water, and the higher the water content, the lower the dynamic compressive strength. Besides, the strain increases with the increase of the saturation degree. It shows that water has a weakening and softening effect on sandstone, and this effect will increase with the increase in saturation. By analyzing the fracture fractal dimension of sandstone, the fracture degree of sandstone first increases, and then decreases with the increase of water saturation, which indicate that under the action of dynamic load, the influence of the sandstone fracture degree can weaken the effect of water on sandstone and the Stefan effect produced by the water on sandstone cracks. However, the weakening effect is dominant in the compressive strength of sandstone. The research results can provide theoretical guidance for the study on the stability of surrounding rock of underground coal mine reservoirs.