Roof Movement and Failure Behavior When Mining Extra-Thick Coal Seams Using Upward Slicing Longwall-Roadway Cemented Backfill Technology

Abstract

A novel and environmental-friendly backfill mining method known as upward slicing longwall-roadway cemented backfill (USLCB) technology has recently been proposed and successfully applied in mines extracting extra-thick coal seams located under sensitive areas. This paper studies the effects USLCB had on roof movement and failure behavior using the mechanical analysis approach. The application of USLCB in the Gonggeyingzi Mine is taken as a case study with roof movement behavior being monitored over a single mining cycle, as well as over multiple mining cycles of different coal slices. In addition, backfill performance requirements to prevent roof failures where USLCB is implemented are studied. The results show that the deflection curves of the roof at the end of each mining cycle during mining the first and the six slices are symmetrical, but they change from asymmetrical to symmetrical during the mining progresses of the second slice to the fifth slice. The final state of roof movement after the first slice, and through to the fifth slice, displays an obvious “flat bottom” pattern in the middle of the deflection curve. The roof movement during the removal of the top slice is noticeably different from other slices. The results also show that the requirements of the elastic modulus, as well as the strength of the backfill, increase as the number of mined slices increases from 1 to 5, but the requirements drop sharply for mining the top slice.

Study on deformation control of overlying strata in short-wall coordinated filling mining of thick coal seam under aquifer

“…In response to the serious water gushing at the working face during the production of this coal mine, which brings problems to the mine's safety production and water resources protection, the method of SCFM of thick coal seams under strong waterbearing seams is proposed. Ordinary fully mechanized working face length according to the different coal thickness is usually 100-200 m, SCFM than the general fully mechanized mining face length is shorter, usually less than 100 m, for the control of Frontiers in Earth Science frontiersin.org overburden deformation has a certain effect, with high water material filling can be more effective limit overburden deformation space (Wang et al, 2016;Li et al, 2017;Deng et al, 2020). As shown in Figure 2, the SCFM takes a certain number of working faces as a mining cycle (five working faces are taken as an example in the figure).…”

Research of the Backfill Body Compaction Ratio Based on Upward Backfill Safety Mining of the Close-Distance Coal Seam Group

“…Combined with the key layer theory, Zhang et al [17] investigated the relationship between the maximum deflection and strength of the key layer, the elastic foundation coefficient of the lower stratum and the lithologic parameters, and proposed the backfill mining surface subsidence control principle to limit the subsidence of the key layer. Deng et al [18] studied the whole process dynamic subsidence curve of the upper coal seam roof with the progress of lower coal seam backfill mining and expounded the influence of elastic model and strength variation of the filler on the upper coal seam roof subsidence. Zhou et al [19] evaluated the filling effect of solid backfill mining goaf with BBCR as the measurement index and studied the key factors affecting BBCR, and the BBCR monitoring system was established according to the engineering practice in order to optimize the backfill mining technique.…”

Permeability of Sand-Based Cemented Backfill under Different Stress Conditions: Effects of Confining and Axial Pressures

“…SBCB has high compactness and good control against overlying strata deformation. This method has been extensively applied to the "three-under" coal resources in recent years [15][16][17]. Figure 1(b) shows the mine water's occurrence state via the SBCB method.…”