“…Further, the constituents of materials can be treated as homogeneous at a certain length scale, but when observed at a smaller length scale, the constituents themselves may become heterogeneous; i.e., the multiscale phenomenon for heterogeneous shale rock materials (cf. Bayuk et al, 2008;Bobko and Ulm, 2008;Bobko et al, 2011;Guo et al, 2013;). For examples, according to Guo et al (2013), the components of shale rocks should contain clays, kerogen, cracks, pores, quartz, calcite and dolomite.…”