Abstract: The aim of this research is to enhance the overall stability of tailings dam by identifying the influence range of shear zone of geogrid-reinforced tailings dam. The influence law of shear strain zone was analyzed from macro-and-microscopic perspectives via indoor direct shear tests of tailings sand with varied moisture contents under different overlying loads. Results unveiled that: the test displacement of geogrid-reinforced tailings increased approximately linearly with the peak displacement ranging between 20 mm and 25 mm; overlying load presented a positive proportional relationship with peak shear displacement, and the growth rate of shear displacement gradually attenuated. The water content of tailings sand was 3%, 7%, 11% and 15%, respectively, and the density of tailings declined by 2.2%. With the growth of water content, the apparent cohesion gradually strengthened, and the interfacial friction angle first climbed and then dropped. Furthermore, partical flow code(PFC) model was established to accurately locate the area with large displacement change in the test chamber for meso-scale non-punctuation measurement analysis. The influence distance of shear strain zone reduced with the increase of water content of tailings sand, and such reduction alleviated gradually.

Key words: geogrid, reinforced tailings dam, direct shear test, PFC discrete element, shear strain zone