The validation of numerical models of geomechanical processes relies on physical testing of these processes in a laboratory setting. However, due to their heterogeneous nature, test specimens of natural materials often show a wide range of geomechanical properties. In the last decade, major advances have been made in the quality and commercial availability of 3D printers. At present, 3D printing has been used in the fabrication of medical implants and prosthetics, prototyping of mechanical designs and even in the construction of complete buildings. This paper presents 3D printing as an opportunity to control many of the variables that are inherent to the study of geo-materials. By using a 3D sand printer to fabricate test specimens, we were able to produce multiple, exact replicas of specimens with a high level of control on the nature of the heterogeneities and the properties of the matrix. Preliminary test results are presented from uniaxial compression tests and optical microscopy evaluation of introduced flaws. By knowing and controlling inter-sample variability in terms of porosity, fracture networks, grain size distribution, density distribution, etcetera, 3D printing of geomaterials provides a valuable tool to validate numerical models, develop scaling laws and constitutive relationships, quantify the degree of influence from pore geometry, fracture network characteristics and structural heterogeneity on macroscopic properties such as bulk modulus and effective permeability
In the last several decades, numerical models of geomechanical processes have become a highly sophisticated and powerful tool to study the behavior of rock from a micro-scale to a basin-scale [1, 2]. These numerical models are heavily reliant on physical testing of natural rock samples for calibration and validation purposes. However, due to their heterogeneous nature, test specimens of natural materials often show a wide range of geomechanical properties . This poses a significant obstacle for both calibration and validation of the numerical models.
The rapid development of the additive manufacturing (3D printing) industry in recent years has resulted in the commercial availability of a wide range of 3D printer models [4, 5, 6, 7]. Although the vast majority of 3D printers produce plastic parts [4, 5, 6], there are 3D printing techniques that allow the printing of metals , ceramics  and sand .
Although the possibilities of 3D printing have been recognized in the rock mechanics world [10, 11, 12], plastic has been the prevalent material of choice. To the authors’ knowledge, the ability to print granular materials such as sand has not yet been utilized in the rock mechanics scientific community.