Abstract
Serious floor heave in gob-side entry retaining (GER) with fully-mechanized gangue backfilling mining affects the transportation and ventilation safety of the mine. A theoretical mechanical model for the floor of gob-backfilled GER was established. The effects of the mechanical properties of floor strata, the granular compaction of backfilling area (BFA), the vertical support of roadside support body (RSB), and the stress concentration of the solid coal on the floor heave of the gob-backfilled GER were studied. The results show that the floor heave increases with the increase of the coal seam buried depth, and decreases with the increase of the floor rock elastic modulus. The development depth of the plastic zone decreases with the increase of the c and φ value of the floor rock, and increases with the increase of the stress concentration factor of the solid coal. The development depth of the plastic zone in the test mine reached 2.68 m. The field test and monitoring results indicate that the comprehensive control scheme of adjusting backfilling pressure, deep grouting reinforcement, shallow opening stress relief slots, and surface pouring can effectively control the floor heave. The roof-floor displacement is reduced by 73.8% compared to that with the original support scheme. The roadway section meets the design and application requirements when the deformation stabilizes, demonstrating the rationality of the mechanical model. The research results overcome the technical bottleneck of floor heave control of fully-mechanized backfilling GER, providing a reliable basis for the design of a floor heave control scheme.
Highlights
In gob-side entry retaining (GER) of underground coal seam mining, the headgate of the current mining panel is retained by constructing the roadside support body (RSB) and serves as the tailgate to the subsequent adjacent panel [1,2] (Figure 1)
This technology has the following advantages: (1) Backfilling mining can consume a large amount of waste gangues piled up on the ground, control the surface subsidence, turn waste into usable materials, and alleviate environmental stress; (2) The compacted gangues in the backfilling area (BFA) can limit the roof deformation, reducing the load during roof weighting and avoiding rock burst accidents of the working face [3,4,5,6,7]; (3) Owing to the support of gangues in the BFA, the support pressure of the RSB is reduced, which is favorable for stabilizing the RSB, improving the success rate of entry retaining
The influence of the mechanical properties of affecting the GER floor heave were analyzed from a theoretical point of view, and the principles of floor strata, the granular compaction of BFA, the vertical support of RSB, and the stress concentration controlling the heave against each influencing factor were necessary of solid coalfloor on floor heave in the gob-backfilled
Summary
In gob-side entry retaining (GER) of underground coal seam mining, the headgate (entry 2 front of the active panel #1) of the current mining panel (panel #1) is retained by constructing the roadside support body (RSB) and serves as the tailgate (entry 2 behind of the active panel #1) to the subsequent adjacent panel (panel #2) [1,2] (Figure 1). For the gob-backfilled GER technology, a roadside artificial wall was built to maintain the roadway based on the backfilled gangue supporting the roof. GERtechnology technologywith withfully‐mechanized fully‐mechanizedbackfilling backfilling isis adaptable adaptable to to complex complex geological geological conditions conditions such such as as deep deep roadways, roadways, high high stress, stress, large large mining mining expanding application rangerock, of GER technology It of is in the engineering height, and weak surrounding expanding the application range. GER technology technology practice of the gob-backfilled that the floor heave in the retained entry is larger than that inthe the it is found in the engineering practice of the gob‐backfilled that the floor heave. 2b), asinrush well as seriously affecting the safety of the roadway andas the normal aquifer, in accident of floor.
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