Dynamic Response and Damage Regularity of Sandstone with Different Moisture States under Cyclic Loading

In the process of geotechnical engineering excavation, wet and water-filled rock masses are inevitable. To obtain mechanical properties these rocks, indoor tests required, most dry or nearly dry. They cannot really reflect true nature rock, let alone its under a dynamic load. The was repeatedly impacted during blasting excavation process. determine response characteristics damage evolution rocks with different moisture states cyclic loads, samples three saturation levels were prepared. experiment, Hopkinson pressure bar equipment utilized to perform five cycles impact same incident energy, times recorded. Nuclear magnetic resonance technology employed change law pores specimens after impact, cumulative rules combined fractal theory. From experiments, it can be observed that stress-strain curves all similar, in they have stress addition unloading stages. peak is proportional time content, whereas opposite for strain. After small large closed increased, respectively. porosity rate increased an increase time. With this trend more obvious. It via imaging internal fractures water-bearing obvious multiple impacts. particular, saturated exhibited severe damage. Fractal analysis NMR figures revealed times, dimension not This phenomenon indicated macro gap appeared. dimensions continued increase, less