Experimental study on the Crack Initial Stress and the Crack Damage Stress of Red Sandstone Under Different Strain Rate Conditions

In order to investigate the progressive failure process of brittle rock, the mechanical properties of red sandstone from southeast Shandong province were systemic studied. The stress-strain curves and failure modes of samples under different strain rates were recorded as original data. Based on these data, the axial stiffness, the volume strain, the crack volume strain, and so on were deduced for further analysis. The crack initial stress and the crack damage stress were identified by Moving Point Regression Technique and stiffness curves. The influence of strain rate on the micro-cracking process and the ultimate compression strength of red sandstone were then studied. The results show that: as the strain rate increases, the ultimate compression strength first decreases and then increases as the strain rate increases, and the ratio of crack initial stress/ultimate compression strength and crack damage stress/ultimate compression strength decreases.