Experimental Investigation on Mechanical Behaviors and Damage Evolution of Soft Rock Analog Containing Internal Fracture Network

The widely and randomly distributed presence of fractures and other types of discontinuities significantly affects the rock’s mechanical behavior. However, few physical experiments have been employed for the systematic study of rocks containing internal fracture network (IFN) due to limitations in specimen preparation. In this study, soft rock analog specimens containing IFN are prepared by sand powder 3D printing to quantitatively analyze the influence of fracture geometry parameters on the mechanical behaviors. Furthermore, the acoustic emission (AE) characteristics and principal strain field of the IFN specimens are analyzed, and an innovative approach to calculate the concentration of energy release (P) is proposed and used to analyze the intensity of the energy release and damage evolution of IFN specimens. The results show that among the four investigated fracture parameters (angle β, radius D, number n, and aperture d), parameters β and D both significantly influence uniaxial compressive strength (UCS) and elastic modulus (E). Specifically, UCS and E are negatively correlated with D, while they are initially negatively correlated with β and then positively correlated. Increasing β and D decrease the P and reduce the brittleness of specimens during post-peak failure, the initiation of secondary cracks occurs earlier and more fragmentation after the final failure as D increases. The variation patterns of mechanical behaviors and damage evolution of IFN specimens are discussed in depth and are expected to be more widely used in rock engineering.