Understanding Failure Mechanism of Non-Persistent Discontinuities Using 3D-Printed Synthetic Rock Mass

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The mechanical and hydraulic characteristics and failure mechanism of intact rocks and rock joints are commonly determined by carrying out laboratory testing on small scale samples. The results from laboratory tests are fundamental for estimating the strength parameters and evaluating the failure behavior of a rock mass, that consists of a complex interplay of two components: intact rock and spatially distributed joints of various orientation and persistence. Although the individual geomechanical properties of these fundamental components can be properly determined in the laboratory, estimates of geomechanical properties at the rock mass scale and its failure behavior remain highly uncertain.These major uncertainties are mainly related to the often limited persistence of joints and the spatial distribution of intact rock bridges in the plane or between individual joints. Thus, the behaviour of non-persistent joints and rock mass containing non-persistent joints are dominated by complex interactions. The interpretation of laboratory tests on rock samples that contain non-persistent joints suffer from two major difficulties: 1) it is very difficult to adequately characterize the persistence of natural joints or spatial distribution of rock bridges, and 2) the natural variability in geomechanical properties of intact rock is very high. As a consequence, it is extremely difficult to adequately quantify the effect of spatially distributed non-persistent discontinuities on the rock mass strength and failure behaviour.In this project we focus on understanding the strength, deformational characteristics and failure mechanism of non-persistent joints and rock mass containing non-persistent joints. In order to overcome the two above mentioned limitations, we use 3D-printed “synthetic” sandstone samples which behave similar to brittle rocks. Both, the rock strength and the spatial distribution of joints can be precisely designed and printed in 3D using 3D printer. The approach requires to demonstrate that 1) the printed synthetic intact rock behaves similar a natural brittle rock, 2) fully persistent joints can show similar strength compared to natural joints and 3) various configuration of pre-defined rock bridge distributions need to be systematically tested. The key advantage of the proposed method is to allow for carrying out “repeatable” laboratory testing on samples with the same physical conditions, reducing the level of uncertainties. The primary outcome of proposed approach is to improve the current understanding of the strength and failure mechanism of the rock mass with non-persistent joints.