3D-Printed Rock: Combining Binder Jetting with Natural Materials to Create Rock Analogues for Unprecedented Experimentation

K.J. Hodder, S. Ishutov, R.J. Chalaturnyk
University of Alberta,
Canada

Keywords: 3D printing, binder jetting, rock, sand, mechanical properties

Summary:

As additive manufacturing (AM) continues to build foundations in various engineering sectors, geological and geotechnical engineering is emerging as an area of increased demand for repeatable, controlled analysis of rock properties. In order to determine the mechanical properties of rocks for drilling, exploration and sustainable recovery of natural resources, routine laboratory experiments are conducted on rock samples to determine their geomechanical and fluid flow characteristics. Due to the inherent heterogeneity of natural rocks, variation and sample scarcity have been a critical problem for decades. With no prior solution to relate rock properties at different scales of analysis, broad assumptions must be made that remain suspect. Variables such as grain size and shape, mineralogy, cementation history, bedding orientation, pore network diagenesis and number of grains in contact with each other can change drastically between rock types and location. The repeatability of experimental work is therefore challenging in in geomechanical engineering and highly contested [1]. Computer modelling may be used to simulate rock behavior on larger scales (from a few centimeters to tens of meters), but material parameters are still required as boundary conditions. With limited data caused through sample variance and scarcity, the results of rock modelling and testing cannot always be scaled with ease. To combat this issue, AM can be combined with natural material to create rock analogues. More specifically, binder jetting is used to place binder at discrete locations using a print head on a bed of sand. We established a workflow to fabricate 3D-printed rocks that have properties resembling natural sandstone, where a brittle fracture response is observed during loading [2,3]. The 3D-printed rock provides a repeatable measure of compressive strength that is unmatched by natural material [3], with no limit to the amount of samples that may be fabricated. The material response of the 3D-printed rock can also be tuned to mimic the natural sample under study by changing the printing parameters. Thus, the variability and scarcity in geomechanical testing is removed for the first time. Other features include the addition of discrete fractures or bedding planes that can be assembled by printing samples in multiple parts [4]. For flow experiments, the rock analogues can be tuned to behave in a hydrophilic or hydrophilic manner via surface treatments [5]. Current work includes taking computer tomography data of a natural rock and 3D printing a rock analogue that has a similar internal structure and changing the wettability by surface coating. 3D-printed rocks have the potential to disrupt the geotechnical and geological engineering sectors by providing a tangible route for fabrication of experimental samples. Included herein is an overview of the development, various uses and studies that have been conducted on rock analogues, along with the applications that are relevant to industry and engineers.