Study on the Effect of Interlayer Tailings Content on the Shear Properties of Geotextile Interface

To investigate the influence of tailings content between geotextile layers in tailings dams built with geotextile bags on interfacial shear behavior and dam stability, direct shear tests were conducted to examine the shear mechanical properties of the geotextile interfaces under different tailings water contents (20%, 30%) and different tailings contents per unit area between geotextile layers (0, 0.0125, 0.0250, 0.0500 g/cm²). Based on the distribution patterns of tailings particles at the shear plane, the interface shear mechanism was elucidated, and the influence of interlayer tailings content on the stability of the tailings dam built with geotextile bags was analyzed using the discontinuous-continuous coupling method. The results show that, under the tested material properties and experimental conditions, both the peak shear stress and the interfacial friction angle first increased and then decreased with increasing tailings content between geotextile layers, reaching their maximum values when the tailings content was 0.0250 g/cm², while the cohesion exhibited the opposite trend. An appropriate amount of tailings particles embedded in the pores of the geotextile enhances the mechanical interlock between the particles and the geotextile, thereby improving the shear resistance at the interface. When the tailings content was excessively high, a loose tailings layer formed at the interface, shifting the shear plane into the tailings and, consequently, reducing the interface shear strength. Under the tested conditions, the safety factor of the dam first increased and then decreased as the tailings content between geotextile layers increased, reaching its highest value at a tailings content of 0.0250 g/cm², which was approximately 14.3% higher than under conditions without tailings. When the tailings content increased to 0.0500 g/cm², the safety factor of the dam decreased. This research provides a theoretical basis for quality control in the construction of tailings dams built with geotextile bags and the design of geotextile interfaces under conditions comparable to those investigated in this study.