This study investigated the dynamic strength and failure mode of rock-like materials considering the effect of microscopic composition and loading rate. A series of uniaxial compressive tests and SHPB tests were conducted on specimens, which contained 40% and 60% grain contents by volume and two types of cementation material (gypsum and weak gypsum). The results indicate a lower grain content and, correspondingly, a higher matrix volume, yields a higher quasi-static strength. The dynamic strength is related to not only the grain content but also the degree of grain breakage. Moreover, inter-granular fractures mainly occur under quasi-static compressive conditions, and the failure mode becomes trans-granular when the strain rate is high. Specimens with lower grain content exhibited fewer fractures and larger fragments than those with higher grain content. Considering the influence of matrix property, the weak-gypsum-cemented specimens exhibited higher dynamic increase factor and lower strength than the gypsum-cemented specimens.
When rock-like materials are subjected to different types of external loadings, such as blasting, impact, earthquakes, and landslides, their strength and failure patterns are strongly influenced by loading rates (Zhao et al., 2014; Wisetsaen et al., 2015). Split Hopkinson Pressure Bar (SHPB) tests were commonly conducted to obtain the strain and stress of rock-like materials at high loading rates (Li and Shi, 2016; Yin et al., 2016). Many studies demonstrated that the rock strength increases with the strain rate, especially above 101 s−1 (Yao et al., 2017). Jeng et al. (2004) and Weng & Li (2012) investigate the influence of microscopic parameters on the mechanical properties of 13 types of sandstone in Taiwan. The results reveal that a lower porosity n and a lower grain area ratio GAR result in greater strength. GAR also affects fracture patterns. When GAR is low and the matrix is softer than the grains, inter-granular fractures are observed. Zhang & Zhao (2013) pointed out that inter-granular fracture is the main failure mode of marble under quasi-static compressive conditions. As the strain rate increases, the failure mode becomes trans-granular or intra-granular failure.
