Experimental and numerical study on the influence of gravitational stress gradient on the mechanical behavior of 3D printing sandstone models

The vertical stress gradient induced by gravity is an important factor affecting the mechanical behavior of the surrounding rock masses in underground engineering. However, it is usually not considered in scale-down physical modeling experiments since this stress gradient is hard to reproduce. In this paper, centrifugal hyper -gravity modeling is proposed to investigate the effect of the stress gradient on the mechanical behavior of an underground cavern model. 3D printing sandstone specimens with a void cavern inside are used, and uniaxial experiments are conducted both under 1 g (normal gravity) and under 100 g (hypergravity). Results show that the failure of the rock model is more likely to occur at the bottom under 100 g compared with that under 1 g. In addition, the splitting characteristics of the rock model are more pronounced under hypergravity. Related numerical simulations have been performed based on the three-dimensional realistic failure process analysis (RFPA3D) code to gain further understanding of this phenomenon. Under hypergravity, high stress concentration zones transfer to a lower location of the rock model, resulting in more microcrack clustering at this position. It is indicated that the stress gradient induced by hypergravity contributes to the failure mode of the un-derground cavern model. The results indicate the principal possibility to conduct more convincing scaled physical modeling of rock engineering problems using centrifuge to reproduce the prototype stress with gravitational stress gradient.