A new numerical method for constructing the three-dimensional microstructure of S-RM using digital image processing technology

Soil-rock mixture (S-RM) is widely distributed in some accumulation slopes and commonly used as a backfill material in the field of geotechnical engineering. The mechanical properties of S-RM play a pivotal role in ensuring the stability of geotechnical engineering projects. The discrete element method (DEM), which can construct S-RM’s microstructure model, is an effective tool for studying its mechanical properties. Currently, the most realistic and precise approach for constructing a three-dimensional (3D) microstructure model of S-RM is digital image processing (DIP) technology using computed tomography (CT) scanning device or 3D laser scanning device. However, these devices are very expensive. This study aims to develop an economical and accurate DEM for constructing the 3D microstructure of S-RM using DIP technology with a conventional digital camera. Firstly, a digital camera was used to capture three sets of 2D images on real rock blocks around four circles at different angles. DIP technology was then applied to process the 2D images and construct the refined 3D rock block grid models. Subsequently, the geometric parameters of the grid models were compared with those of the corresponding real rock blocks to validate the accuracy and applicability of this method. The microstructure model of S-RM in the large-scale direct shear test was then established and verified for DEM simulations. Finally, the mechanical properties of S-RM were analyzed based on the evolution of the shear band, the rotation of rock blocks, and the change of contact force chain. Graphic abstract