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 beta, radius D, number n, and aperture d), parameters beta 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 beta and then positively correlated. Increasing beta 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. The influence of fracture geometric parameters on mechanical behaviors of the soft rock analog specimens containing internal fracture network is quantitatively analyzed based on the method of relative impact and the population standard deviation.As the fracture radius increases, the initiation and propagation of secondary cracks occur earlier, and the specimens exhibit more fragmentation after the final failure.An innovative approach to calculate the concentration of energy release (P) was proposed and used to analyze the influence of fracture parameters on the intensity of energy release in different loading stages of the specimens.Increasing fracture angle and fracture radius decreases the intensity of energy release and reduces the brittleness of specimens during post-peak failure.