Effects of Water Immersion on the Long-Term Bearing Characteristics of Crushed Gangue in Goaf

Abstract

To study the long-term bearing characteristics of crushed gangue in goaf under water immersion conditions, the creep test of the crushed gangue in the water immersion state was performed by using the self-developed large-scale deformation-seepage test system of crushed rock. The effects of the rock lithology, axial stress, and grain composition on the long-term bearing deformation characteristics and fractal characteristics of crushed gangue under water immersion were analysed. The results show that under certain conditions of axial stress and grain composition of the gangue, a greater uniaxial compressive strength of water-saturated rock corresponds to a greater deformation resistance of the rock, smaller strain and crushing expansion in the corresponding creep stage, and greater fractal dimension increments of the crushed gangue after compression, and the gangue will have more serious crushing. With identical grain compositions and with the increase in the axial stress in the creep stage, the strain increases, the crushing expansion decreases, the fractal dimension increments of the crushed gangue after compression increase, and the gangue will have more serious crushing. Under identical axial stress conditions, when the Talbol power index n is 0.5, the differentials of the strain and crushing expansion for the crushed sandstone sample in the creep stage are minimal. When n is 0.3 or 0.7, these quantities are basically equal. With the increase in the Talbol power index, the fractal dimension increments of the crushed sandstone sample during compression gradually increase, and the crushed sandstone sample will have more serious crushing.

Study on Movement Law of High-Position Thick and Hard Roof and Mine Earthquake Control by Ground Fracturing Technology

“…In order to ensure the safe and efficient production of coal mining, it is proposed to conduct ground fracturing experiment before mining to cut off the high-level hard and thick roof to reduce the roof breaking span and weaken the rock strength, as shown in Figure 5, so as to avoid the occurrence of large-energy mine earthquake events caused by the hard roof fracture. When the vertical fracture occurs in the fractured layer, the stress state of the rock stratum changes [43][44][45]. The two ends of the stratum are in the state of fixed support stress, and the stratum is cut into blocks A and B by the fracture plane, which is similar to the hinged structure.…”

Case Studies of Comprehensive Gas Control Method during Fully Mechanized Caving of Low-Permeability Ultrathick Coal Seams

“…Gas emitted from pressure relief in the coal seam floor was an essential gas source in the mining panel. After the working face mining, the overlying strata underwent fracturing and formed the bent subsidence zone, the fracture zone, and the caving zone [32][33][34][35]. Meanwhile, many layered and vertical fractures were produced [36,37], and gas was accumulated in these regions.…”

A Study on the Impact of Longwall‐Mining Operation on the Stability of a Slope‐Pillar Structure

“…e static load of the protective pillar in the slope area demonstrates a nonuniform trend. Based on previous studies [7,8,13,23], assuming that the structure of the slope is single and the slope angle remains unchanged, following the relationship identified between the protective pillar and the slope projection position, two types of side slope-pillar mechanical models have been established, as shown in Figure 7. In Figure 7, F 1 refers to the supporting force of the external side of the pillar to the overlying strata, F 2 refers to the supporting force of the internal side of the slop pillar to the overlying strata, and F 3 refers to the supporting force for broken block.…”