Taking Ping Dingshan Coal Mine Group 12 as an example, this paper explains the system layout, key equipment and backfilling technology in detail. It probes into the characteristic of rock strata movement behavior and surface deformation above the gob area through in-site measurement method. The results show that as the overburden strata are effectively supported by the backfill body in mined out areas, there were no evident phenomena as first weighting or periodic weighting during mining process. Besides, influencing scope of advanced support pressure and the strata behavior degree were much smaller than that of the traditional methods of caving mining. Since overburden strata had been well supported by backfill body, it shows the posture of sinking slowly, only resulting in bending zone and minor fracture zone.

Abstract:As thick rock partings delay the efficient mining of coal seams and constrain the sustainable development of coal mines, an innovative extraction method for a coal seam with thick rock parting was proposed. The coal seams were divided into different sub-zones according to the thickness of rock parting and then the sub-zones were mined by separately using three mining schemes involving full-seam mining, combined mining using backfill and caving (CMBC), and reducing height mining. Afterwards, the study introduced the basic mechanism and key devices for the CMBC and analysed the working state of the backfill support in detail. Moreover, the method for calculating the length of the backfill zone was proposed to design the length of backfill zone and the influences of four factors (including bulking coefficient) of rock parting on the length of the backfill zone were also explored. By taking the No. 22203 panel, Buertai mine, Inner Mongolia, China as an example, the mined coal resource by using the CMBC extraction method will increase by 1.83 × 10 6 tons and the recovery ratio will rise from 56.2% to 92.4% compared with mining of the 2-2 upper coal seam alone. Moreover, by applying CMBC, a series of environmental and ecological problems caused by rock parting is reduced, which can improve the environment in mined areas. The research can provide technological guidance for mining panels of a coal seam with a thick rock parting and the disposal thereof under similar conditions.

This paper introduces a longwall mining attempt at Jining No. 3 Coal Mine. A solid backfill coal mining method was first applied to exploit the coal resources buried under the Nanyang Lake embankment. A numerical model was established based on analysis of geological conditions in the area and the structural characteristics of the embankment. This model was used to study the two key factors that influence the embankment deformation: the backfill body's compression ratio and the working face advancing distance. The measured results from Nanyang Lake embankment show that the maximum value of the surface subsidence was only 68 mm, and the maximum values of the horizontal strain and incline strain were 0.16 and 0.18 mm/m, respectively. The measured backfill body's compression ratio was approximately 89.1%. Field demonstrations have shown that solid backfill mining is effective in controlling strata movement and surface deformation.

Over the past few decades, the low recovery of resource coupled with the strong strata behavior has plagued the development of mines in Western China. To address these issues, an emerging and innovative technology-roadway backfill mining method was proposed in this paper on the basis of the compressive properties of backfill materials. A rational composition for backfill materials is obtained and the roadway layout and the backfill mining technology of this method are presented. Once placed, the backfill materials together with the barrier pillar have to satisfy certain mechanical stability requirement to ensure a safe underground working environment. In this respect, a mechanical model of roadway backfill mining method was developed using statics analysis. Formulas for predicting roof subsidence above mined out area and the stress distribution in barrier pillar are obtained. Furthermore, an instability criterion of coal pillars is proposed. Combined with the specific geological and mining conditions of 3101 working face in Changxing Coal Mine, the current study showed that the width of backfill mining roadway to be 7.0 m, the width of unexploited coal pillar to be not less than 3.0 m, and the elastic foundation coefficient of backfill body to be not less than 1.5 × 107 N/m 3 .