Exploring the elliptic fissure cracking mechanisms from the perspective of sand 3D printing technology and Meshfree numerical strategy

Abstract

The existences of cracks affect the strength and fracture morphologies of rock masses. However, there are few discussions on factors such as fissure apertures and quantities. Based on this background, sand 3D printing is used to prepare rock-like samples. Crack propagation experiments are carried out on fissured samples with different fissure apertures and fissure numbers. DIC technology is utilized to obtain the full-field strain distributions on specimen surfaces. Meanwhile, a meshless numerical method is developed to simulate rock damage evolutions. Results show that: Three crack types can be seen, wing cracks, shear cracks as well as main cracks. Wing crack extensions on two prefabricated fissures outer sides are along the loading direction, while inner side wing cracks overlap with two prefabricated fissures to form a “fusiformis-shaped part”. The propagation of shear cracks after wing cracks indicates final specimen failure. Main cracks exist in the circumstances with large fissure apertures. As fissure apertures increase, wing cracks initiating points deviate from tips, and the appearance of inner wing cracks in double fissure specimens precedes outer wing cracks. Stress–strain curves of the specimen experience five stages: 1) compressive stage; 2) elastic stage; 3) stress drop stage; 4) crack propagation stage and 5) failure stage. Finally, formation mechanisms of wing cracks, shear cracks, “fusiformis-shaped parts” as well as the mechanical influences of fissure apertures on the specimens are discussed.