Mechanical and volumetric fracturing behaviour of three-dimensional printing rock-like samples under dynamic loading

Abstract

Heterogeneous rock contains numerous pre-existing three-dimensional (3D) cracks, which control its mechanical and fracturing properties. Considerable effort has been devoted to studying the volumetric fracturing behaviour of rock under static loading conditions. Although rock masses are often subject to dynamic impacts such as earthquakes and blasting, the mechanical and volumetric fracturing behaviour of rock under dynamic loading is still poorly understood. In this paper, dynamic laboratory tests were performed on 3D-printed artificial rock samples with 3D embedded flaws created during three-dimensional printing (3DP), with the aim of studying the volumetric fracturing and mechanical properties of these samples under impact with high strain rate. The results show that the dynamic compressive strength and the tangent modulus decrease with an increasing number of flaws, but have very limited effects on the ratio of the fracture initiation stress of the first crack to the peak stress of the sample, the maximum axial strain of the sample and the volumetric fracturing behaviour of the sample. The tensile failure of a sample is caused by the continuous extension of wing cracks from the outer flaw tips. The mechanical and volumetric fracturing behaviour of samples with 3D embedded flaws are strain rate dependent. The tangential modulus and the ratio of the fracture initiation stress of the crack to the peak stress increase significantly when the loading type changes from static compression to dynamic compression. Under dynamic compression, wing cracks can continuously extend to the sample ends, whereas under static compression, wing cracks can intermittently extend only a limited distance. Moreover, the fracturing behaviour of 3D flaw differs from that of 2D flaws under dynamic loading. Under high strain rate loading, wing cracks generated at 3D flaw tips lead to splitting failure of the sample, while shear cracks formed at 2D flaw tips result predominant shear failure of the sample. The findings in this paper could facilitate a better understanding of rock failure subjected to dynamic loading conditions.