Evaluation of 3D Printing in Obtaining Replicates of Discontinuity Roughness

Obtaining discontinuity roughness profiles is essential for investigating and understanding of the shear behavior. Recent advancements in 3D printing lead to the development of new methods for replicating discontinuity surfaces in which 3D printer outputs are used as molds and replicates are cast with a material that shows rock type behavior. Objective of this study is to investigate the efficiency of this methodology in terms of the change in the roughness degree through the steps of the discontinuity sample replication procedure. For this purpose, 3D models of two natural discontinuity samples with different roughness levels are created with close-range digital photogrammetry. The 3D models are used for obtaining 3D printer outputs of the discontinuity surfaces. These outputs are used as molds to cast concrete discontinuity replicates. The roughness levels of the molds and the replicates are also determined by creating the 3D models with close-range digital photogrammetry. Then, the roughness values of the 3D models, the molds and the replicates are compared, so that the change in the roughness degree through the steps of discontinuity sample replication procedure can be evaluated. The results indicated that the use of the 3D printers for discontinuity sample replication succeeded to accurately reflect roughness levels, especially in planar and small surfaces. Applicability of the methodology is also investigated by conducting direct shear tests on the produced replicates. The 3D printers offer a low-cost and practical way to produce discontinuity samples with the same surface morphology and thereby decreasing the uncertainties associated with shear testing of rock discontinuities. They also allow conduct of repeated shear tests in various scales for better insight in investigating the discontinuity shear behavior.