Experimental Investigation into the Mechanical Behavior of Jointed Soft Rock Using Sand Powder 3D Printing

The presence of joints and other types of discontinuities has a significant effect on the mechanical behavior of rock, thereby fundamentally influencing the stability of rock excavations. The main challenge associated with the experimental research on jointed rock lies in the difficulty of sample preparation to represent the influence of discontinuities on the mechanical behavior of the rock material. In this study, 3D printing is used as a tool to examine the mechanical behavior of rock with discontinuities. Synthetic specimens are prepared from sand powder and tested in the laboratory to examine the validity of sand powder for simulating soft rock. Further 3D printed specimens with different joint geometries (dip angle, aperture, and trace length) are tested, and the effects of joint parameters on the specimens' mechanical behaviors and failure patterns are investigated and quantitatively analyzed with a relative importance analysis. As expected, the results show that the dip angle has the strongest effect on the uniaxial compressive strength and failure patterns, and the dominant failure mechanism tends to switch from tensile to shear failure with increasing dip angle. The influence of aperture and trace length on the mechanical behavior is also determined and linked to the dip angle. The test results are validated and further analyzed with numerical simulation and analytical methods. The results of this study demonstrate the applicability of sand powder 3D printing as a suitable method for the simulation of soft rock mechanical behavior. The methodology presented in this study could be further extended to other applications in rock mechanics.