Owing to the complexity of current reinforcement mechanisms, test results from existing models alone cannot provide a basis for the design of new tailings dam reinforcement projects. On-site reinforced tailings accumulation dam testing is thus required to further understand the reinforcement mechanism. In this study, the influence of reinforcement on tailings dams and the variation law of pore water pressure (PWP) and internal pressure (IP) in the dam body after slurry discharge were analysed, and a comparative analysis was performed. The results showed that during the field test, the PWP and internal earth pressure of the accumulation dam after grouting gradually increased over time. Reinforcement can greatly reduce the PWP and IP of the reinforced dam; compared with geotextiles, the reinforcement effect of geogrids is slightly greater. Based on these results, we conclude that geosynthetics are a good choice for strengthening tailings accumulation dams.

Currently, the influence of geogrid mesh size on interface characteristics are disregarded in various codes and standards. To explore the reasonable mesh size of geogrid used for reinforced tailings, the direct shear test and pull-out test of geogrid reinforced tailings with different mesh sizes were done. The results show that the shear surface of geogrid reinforced tailings is characterized by the combined action of geogrid-tailings interface and tailings-tailings interface; the geogrid-tailings interface friction was separated from the comprehensive interface friction to analyze the influence of area ratio on it under different test conditions; and the mesh size of geogrid reinforced tailings, that is, the area ratio of the geogrid-tailings interface to the shear surface (α), has a greater influence on the pseudo-cohesion and less on the pseudo-friction angle. The friction strength of the geogrid-tailings interface increases slightly with increasing mesh size, then decreases sharply, and the reinforcement effect of geogrid quickly disappears. Considering the direct shear test and pull-out test, the reasonable mesh size of geogrid reinforced tailings should be the mesh size corresponding to α 0.47–0.55. With the increase α, the effect of the geogrid reinforced tailings can be divided into four stages where the third stage ( $$0.4 \le \alpha < 0.6$$0.4 ≤ α < 0.6 ) is the stage with the best reinforcement effect.

The aim of this study was to explore the correlation between mesoparameters (normal stiffness , tangential stiffness , and friction coefficient fric) and macromechanical parameters (cohesion, internal friction angle, and peak principal stress as well as its corresponding stress variables) of the particle flow code in 3-dimension (PFC3D) built-in linear contact model, which is suitable for simulating cohesionless materials that are similar to tailing sand. A triaxial test model was established using PFC3D, and nonspherical particles were developed by the clump command. Several numerical triaxial tests were performed under different confining pressures and mesoparameters. The results showed that the linear contact model is effective in simulating sandy soil, and the corresponding gradation of particles should be given. No one-to-one correspondence was found between the macromechanical parameters and the mesoparameters. Each macromechanical parameter was most affected by a certain mesoparameter, and the degree of influence was much greater than that of the other mesoparameters. The macro- and mesoparameters were strongly correlated. The stiffness ratio ( ) mainly affected the cohesion value, the friction coefficient of fillers (pebble-fric) mainly affected the internal friction angle and the peak principal stress, the normal stiffness () of particles mainly affected the strain corresponding to the peak principal stress, and the influence of the side wall friction coefficient (wall-fric) was not the strongest but was non-negligible. The microparameter calibration of the contact model can follow the order of parameter adjustment proposed in this study, which can facilitate and enhance the accuracy of the parameter calibration process of the linear contact model.