Study on Multi-Layer Filling Treatment of Extra-Large Goaf and Its Underground Application

Abstract

At present, the many domestic, large mined-out areas caused by single filling ability of the slurry flow state, thin layer flow and hardening after filling in multilayer structure generally need to finish filling for many times, because after a filling experience shows that filling body in the last solidification of flow, this leads to a lower one side of the roof, and far distance part of the filling body cannot pick up top. The determination of backfill strength is the key problem of the cemented backfill method, and it is affected by many factors. Therefore, through theoretical calculation, laboratory testing and numerical simulation methods, combined with the field filling process, this paper has verified the flow accumulation and stratification characteristics of stope layered filling slurry. When the slurry concentration is 60–73%, the slope increases exponentially from 2.5° to 8°. It is revealed that the delamination and meshing state are the key factors to determine the overall strength of large-scale stope filling through the testing of particle size distribution in interlayer and flow direction. The reduction effect of the number and Angle of structural weak surface formed by layering and filling on strength is revealed: cement–sand ratio 1:12, concentration 68%, standard curing R28 > 1.81 MPa. The strength reduction coefficient is 61.31% and 92.96% when the number of layers is 1–4. The higher the number of layers, the greater is the reduction coefficient, and when the stratification angle increases by 2, the strength of backfill decreases by 20–30%. The verification of stope filling coring shows that the in situ strength reaches 2.42 MPa, which is 0.61 MPa higher than the standard curing strength, with an increase of 33.7%. When the depth is from 1 m to 5 m, the strength increases from 2.26 MPa to 2.69 MPa, with an increase rate of 18.2%. Finally, through the research and application of the comprehensive technology of mining and filling coordination under the complex goaf group, the residual ore resources of Xianglushan tungsten mine are effectively recovered, the volume of goaf is significantly reduced, and the safety of goaf is improved.

Strength and Crack Propagation Analysis of Layered Backfill Based on Energy Theory

“…in the formula (11), W a represents the strain energy density when a crack is present, H yi represents a physical quantity related to the thickness of the test piece, and i represents the i th interface.…”

“…A numerical model of lCgb was built using simulation software (PFC2D) to demonstrate the dynamic crack evolution of lCgb during loading. ; Jiao et al [11] and Wang et al [12] proved the reduction effect of the number and Angle of the structural weak surface formed by layering and filling on strength revealed; Wang et al [13] established the damage evolution and constitutive model of backfill body by using damage mechanics theory considering delamination effect, and established the strength criterion of backfill body considering delamination effect; liu et al [14] use a new damage constitutive model based on energy dissipation was developed to describe the behaviour of rocks under cyclic loading, a study of the damage variable based on energy dissipation was introduced, and the damage evolution equations of two typical rock types were calculated from the results of uniaxial cyclic loading tests; Tan et al [15] study the uniaxial compression tests of mortar specimens with different sand ratios and loading rates were carried out. The energy stored and dissipated was calculated, and the damage constitutive model based on energy was established and verified.…”

Distribution Law of Mine Ground Pressure via a Microseismic Sensor System

“…Xianglushan Tungsten Mine is located in the northwest of Jiangxi Province, China (as shown in Figure 1a), and the surface morphology presented in Figure 1b shows that it has rich scheelite resource reserves (discovered in 1958 and put into production in 1991)-the second largest scheelite discovered in China [38]. The anticline structure of the mining area is gentle (as shown in Figure 1c), and the deposit is concealed [39,40] (as shown in Figure 1d). In addition, its shape is variable, and the rock strata are widely metamorphosed, resulting in large differences in the distribution of mine ground pressure [41][42][43][44][45].…”

An experimental and numerical study of the strength development of layered cemented tailings backfill

“…For large stopes, it is difficult to fill the stope at one time. Therefore, a subsequent backfilling of the stope layer by layering is adopted 8 , 12 – 14 . Due to the structural differences between the complete CTB structure and the layered structure, the mechanical properties of both structures also differ.…”