A Novel Approach to the Laboratory Testing of Replica Discontinuities: 3D Printing Representative Morphologies

The preparation of identical synthetic samples with the same morphological and mechanical characteristics allows for repeatable and reliable testing of discontinuities under varying conditions. Studies on the behavior of replica discontinuities to date have mostly been undertaken on laboratory shearbox apparatus, allowing for the characterization of discontinuity mechanics at low stresses. This study presents a new methodology for creating representative replica discontinuities suitable for testing under triaxial conditions, allowing for characterization at elevated stresses and temperatures. The advancement of computer aided design (CAD), three dimensional (3D) scanning and 3D printing has been used to design and create 3D printed molds in acrylonitrile butadiene styrene (ABS) plastic. Synthetic materials are then cast in to the molds creating cylindrical samples with a pre-existing discontinuity of quantifiable morphology suitable for triaxial testing. Statistical and visual analyses show the morphological characteristics of the synthetic discontinuities to be highly repeatable. In addition, the mechanical behavior of different synthetic compositions in unconfined compressive strength and triaxial is compared to the behavior of natural lower strength sedimentary lithologies. The behavior of the tested synthetic materials is found to not be representative of lower strength sedimentary lithologies, with stress-strain behavior showing failure in a quasi-brittle manner.