Abstract
Aiming at the large deformation problem of gob-side entry in solid filling mining, the roof subsidence of gob-side entry retaining (GER) was studied under the influence of gangue filling, by taking a deep filling working face in Shandong Province as the engineering background and using theoretical derivation as well as FLAC3D numerical simulation. Research shows that the stiffness of the gangue filling body in the gob and the stiffness and width of the entry protection coal and rock mass (EPCARM) are positively correlated with the GER roof subsidence, which is much less affected by the EPCARM parameters than by the GER stiffness. The GER failure to meet the application requirements is mainly attributed to the insufficient stiffness of the gangue filling body and excessive advance subsidence, which inhibit the roof stress transfer. The GER replacement by the gob-side entry driving (GED) scheme, which implies replacing the entry protection gangue bag wall with the coal pillar with a width of 5 m, will reduce the roof subsidence to 0.114 m, according to the proposed equation. The results obtained are considered quite instrumental in deformation control of the gob-side entry filled with gangue, as well as substantiation of GED and GER applicability options.
Highlights
With increasing coal mining intensity and gradual exhaustion of shallow resources, deep mining became a global trend [1, 2]
Gangue solid filling is one of the main technologies used to solve the deep mining problems: it plays a significant role in the control of rock strata and effective utilization of the gangue, effectively controls the surface deformation and stratum fracture, reduces the ground damage, consumes the gangue on the ground and underground, and abates the gangue occupation and pollution [7,8,9,10,11]
Huang et al [23] considered that reasonable selection of mining, filling, and retaining technology, reliable support form, and reasonable combined support scheme are the key to the successful gob-side entry retaining (GER) implementation
Summary
With increasing coal mining intensity and gradual exhaustion of shallow resources, deep mining became a global trend [1, 2]. Many scholars have analyzed the GER with gangue filling from the aspects of strength and width of the roadside filling mass, entry support measures, and filling rate of the gob. Deng et al [22] studied the deviatoric stress evolution characteristics of surrounding rock of the gob-side entry and optimized the GER parameters under different values of buried depth, gob filling ratio, width, and strength of the roadside filling mass. A field investigation of the GER in 2305S-2# and 1302N-2# working faces of a particular coal mine in the Shandong Province of China revealed several sections with serious deformation, despite the application of such preventive measures as support strengthening and increased EPCARM width. E gob of the filling face was filled with solid gangue, the upper entry was retained along the gob, the entry was driven along the roof of the coal seam, and the mudstone floor was broken. Noteworthy is that the large depth and rotary subsidence of the mine made it quite problematic to improve the filling rate in front of the gob. is paper mainly analyzes the roof subsidence and the deformation of entry protection coal and rock mass based on the above field investigation
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