Experimental Study of the Mechanical Properties of a Flexible Grid Filling Body

The fill mining method has become more widely used due to its advantages of a high resource recovery rate, reliability and safety, and reduced surface tailings storage. However, the mechanical properties of the cemented fillings in fill mining are similar to those of ultra-low strength plain concrete, and there are problems such as high brittleness, low bending and tensile strength, and sudden failure. Using a flexible grid as reinforcement material, uniaxial compression, tensile, and shear tests of a flexible grid filling body were carried out, and the results were compared with the mechanical properties of the filling body without the flexible grid. We drew the following main conclusions: the uniaxial compressive strength of the flexible grid filling body gradually increased with the decrease in the grid spacing (the increase in the grid density); the grid dimension had little effect on the uniaxial compressive strength of the flexible grid filling body. The uniaxial tensile strength and shear strength of the flexible grid filling body increased with the increase in the grid dimension; and they first increased and then decreased with the increase in the grid spacing, and there was an optimal grid spacing. From the perspective of the macroscopic failure mode, the flexible grid filling body specimen after the uniaxial compression test had a conjugate shear failure, forming a dumbbell shape with two large ends and a small middle. After the uniaxial tensile test, the macroscopic failure mode of the specimen was tensile failure. After the shear test, the macroscopic failure mode of the specimen was shear slip failure. It is proposed that the tensile strength, shear strength, cohesion, and internal friction angle strengthening coefficients of the flexible grid filling body with different dimensions and spacing are higher than the elastic modulus strengthening coefficients. The experimental results can provide a certain reference and guidance for mine filling.

Automated summary

The fill mining method is popular due to its advantages of high resource recovery rate, reliability and safety, and reduced surface tailings storage. However, the cemented fillings in fill mining exhibit similar properties to ultra-low strength plain concrete, resulting in issues such as high brittleness, low bending and tensile strength, and sudden failure. In this study, flexible grid reinforcement material was used and tests were carried out to compare the mechanical properties with and without the flexible grid. The results showed that the compressive strength of the flexible grid filling body increased with decreasing grid spacing, while the grid dimension had little effect on the compressive strength. The tensile and shear strength increased with increasing grid dimension and showed an optimal grid spacing. The macroscopic failure modes varied based on the test conducted, with shear failure observed in the compression test, tensile failure in the tensile test, and shear slip failure in the shear test. The experimental results provide guidance for mine filling by considering the strengthening coefficients of tensile strength, shear strength, cohesion, and internal friction angle.