A method to obtain artificial sandstone joint specimens for the description of permeability anisotropy-based joint shear deformation

Shear-related joint deformation is critical in the study of the anisotropic characteristics of a single rough joint in the ground stress field, such as aperture development within rock mass joints under the disturbance of mining construction, hydraulic transmissivity and permeability of gas in fractures in georesource research. However, natural rock specimens are too heterogeneous for laboratory tests, and many scholars prefer using a uniform material to replicate natural rock specimens in their investigation. This paper proposed a method to replicate natural sandstone with artificial materials composed of cement, microsilica and quartz sand. Orthogonal tests were designed, and the basic physical and mechanical parameter trends at different mass ratio levels of water-binder, sand-binder and microsilica-cement in binder materials were analyzed by range analysis. Finally, multivariate polynomial regression was applied to describe the relationship among parameters such as σ c , σ t , E , and formula factors of the orthogonally designed specimens as regression equations. Based on the equations obtained from multivariate polynomial regression, a method to determine the formula for artificial sandstone was proposed. The artificial sandstone with the formula determined by this method was tested to be within the allowable error margin compared with the prototype, which proves that the proposed method is effective. Artificial specimens with a well-matched single rough joint were cast, and then direct shear tests were performed on the joint specimens to study the description of permeability anisotropy-based joint shear deformation. Article Highlights Cement, sand and microsilica that were used to make reactive powder concrete were introduced to replicate specific sandstone. An orthogonal design-based method was proposed to investigate the effects of the formula factors of the material on its physical and mechanical parameters. The physical and mechanical characteristics of the described material and sandstone were compared to certify the accuracy of the replication process. A multivariate polynomial regression process was proposed to determine the exact formula of the artificial material in the replication of specific sandstone. To further extend the application of the method in artificially making joint specimens, specimens were cast and direct shear tests were performed to study the description of permeability anisotropy-based joint shear deformation.