This study aims to fully explore the influence of rock joint roughness in the slope stability analysis of an open mine. Therefore, based on the least squares parameter estimation method, a generalized shear strength parameter coupling roughness, which is used to evaluate a slope design, was established by a matching formula reflecting the relationship between the roughness coefficient and the shear strength parameter. Firstly, to verify and calibrate the model, physical direct shear tests were conducted on serrated rock joints, and the effect of roughness was analyzed qualitatively. The results show that an increase in tooth height increases the internal friction angle but decreases cohesion. Therefore, the rock joint direct shear test numerical model by PFC-2D was established and compared with the physical test curve, effectively verifying its correctness. The relationship between cohesion c and internal friction angle φ with roughness coefficient JRC was further quantified, and the new model was then fitted to characterize the relationship between roughness and shear strength parameters. This method is applied to the design optimization of an open pit mine slope. The new parameters are input to GeoSMA-3D, which is used to search for the key block of a bedding slope on an open-pit mine, to optimize the design of the slope.

During coal mining the mechanical behavior of weakly cemented sandstone in roof or interbedded layers is crucial for mine safety. In this study the physical and mechanical properties of 3D printed specimens made from furan resin bonded quartz sand were systematically evaluated. The aim was to achieve high fidelity simulation of natural weakly cemented sandstone from mineral composition to macroscopic mechanical behavior using a saleable, low-cost and post-processing-free manufacturing approach. Multi scale analyses at microscopic mesoscopic and macroscopic levels showed that the mineral composition and XRD diffraction patterns of the specimens closely matched those of natural sandstone. SEM and EDS characterization confirmed that the grain packing and cementation structures were highly similar to those of natural samples. The particle size distribution exhibited the typical log normal pattern seen in sedimentary rocks with both transgranular and intergranular fracture modes present. Mechanical tests including uniaxial compression Brazilian splitting and three-point bending indicated brittle failure characteristics with strengths and elastic moduli approaching those of natural weakly cemented sandstone and higher flexural tensile strength in the three point bending tests than in Brazilian split tests. Tests on specimens with joints successfully reproduced the U shaped variation of peak stress and elastic modulus with joint inclination as well as typical brittle fracture modes. High consistency in mechanical properties across batches further validated the stability and reliability of the 3D printing process. This method provides a precise controllable and low-cost new approach for the physical simulation and modeling of weakly cemented sandstone in mining engineering.