Backfilling And Coal Pillar Coordination Support Mechanism Of Super-high-water Filling Working Face With Deep Mining Depth

Coal pressing problem under the building,railway,water body is the key constraint factor for the mining and sustainable development of the mine.Backfilling mining plays an important role in reducing the settlement range and protecting the surface ecological environment.In the backfilling mining,the backfilling and the coal pillar form a new backfilling-coal pillar coordinated supporting structure,which maintain the stability of the overlying strata together.This paper takes the deep backfilling working face of Yi Neng Coal Mine as the engineering background.On the basis of literature search,field investigation and coalrock mechanics experiments,the paper analyzes the interaction between backfill and surrounding rock with deep mining depth,the mechanical action process of the backfilling-coal pillar supporting structure,and establishes the supporting structure model of the backfilling-coal pillar.In this paper,the load-supporting characteristics of the backfilling-coal pillars with different filling rates and different filling strengths are studied by using the PFC particle flow program,and the stress distribution and failure law are explored.The FLAC3 D finite difference program was used to study the stress distribution and plastic zone development range of coal pillars with different widths under filling conditions.The following research results were obtained:1)When the strength of the backfilling is greater than the pressure relief value of the overburden,the overburden layer can be separately supported;when the strength is less than the pressure relief value of the overburden,the backfilling and the coal pillar cooperate to support the overlying rock stratum,and the backfilling plays a lateral supporting role on the coal pillar,and at the same time supports the overlying rock stratum.2)The model of the backfill-coal pillar cooperative load-supporting structure is constructed.The load-supporting process of the structure goes through three stages: the overburden pressure acts on the coal pillar,the backfilling begins to exert the supporting capacity,and the backfilling-coal pillar synergistic supporting function.The research shows that when the filling rate exceeds 90%,the stress concentration in the vertical direction of the coal pillar is low,and the horizontal stress generated at the junction between the backfilling and the coal pillar is small.When the water-cement ratio of the super-high-water filling filler is less than 95%,There is a plastic zone at the edge of the coal pillar,no cracking occurs,and the basic top produces a small extent of breakage,while the key layer does not break.3)Investigate the factors affecting the stability of section coal pillars under filling conditions,which are the coal pillar's own nature,geological conditions and mining technology.By analyzing the stress distribution,plastic zone range and roof subsidence of different width coal pillars in the backfilling working face,when the coal pillar width exceeds 30 m,the coal pillar supporting pressure and plastic zone development range tend to be stable,taking into account the mining rate and surface subsidence.Control requirements,the section of the reasonable coal pillar width is designed to be 30 m.4)A flexible filling bag with skeleton and up and down telescopic type is designed,and the specific secondary filling implementation method is improved.Based on the secondary filling technology,the conventional ultra-high water bag filling technology is optimized.