Research On Reasonable Width Of Coal Pillars In Thick Coal Seam's Fully Mechanized Caving Face

The application of 20 m wide section coal pillars for roadway protection in coal mines causes a great waste of coal resources.A reasonable width of section coal pillars can not only increase the recovery rate of coal resources,but also optimize the stress environment of the mining roadway and reduce the difficulty of maintenance of the mining roadway.Compared with pillar-free mining technologies such as retaining roadways along the goaf,the technical conditions of mine production technology and geological conditions are not high,the initial investment is less,and the technology is relatively simple.The application conditions of the reasonable width section coal pillar protection technology are more widely used.At present,the theoretical calculation methods of coal pillar width such as empirical estimation method,load estimation method,elastic core theoretical calculation,internal stress field theoretical calculation method,and limit equilibrium theoretical calculation method have their own advantages and disadvantages.This paper takes Heilongguan Coal Industry 11602 fully mechanized caving face as the research background,sums up and absorbs previous research results,combines the section coal pillar overlying rock structure and movement characteristics,and creatively analyzes the upper coal seam to the surface during the mining process of the face The coordinated force of overlying strata and section coal pillars is analyzed,and it is considered that the transfer concentrated force generated by the weight of the rock pillars above the section coal pillars and the incompletely collapsed rock layers at the low position of the mined-out area,and the high overburden of the bending subsidence zone The concentrated force generated by rock flexural deformation is deformed under the action of two parts of stress.In this paper,the large-scale solid coal area and its overlying strata that have not yet been mined are regarded as rigid bodies,the coal pillars are simplified as elastic bodies,and the high overlying strata in the curved subsidence zone in the overburden of the working face are regarded as simply supported at both ends in the rigid body.For the rock beam on the rock mass,a mechanical model of the overlying rock-coal pillar cooperative force is established to clarify the stress source of the section coal pillar's deformation under load,and the expression of the concentrated force F on the coal pillar in the mechanical model is derived.Through the analysis of the mechanism of the supporting system on both sides of the coal pillar on the coal pillar and coal body,it is believed that the restraining force of the supporting system on both sides of the coal pillar on the coal pillar can prevent the expansion of the weak surface of the coal pillar under the influence of mining,and reduce The tensile stress of the coal pillar can improve the shear strength of the coal pillar and the overall strength of the section coal pillar.Based on this,the theoretical calculation formula for the ultimate support strength of the section coal pillar under different supporting strengths on both sides of the coal pillar is proposed.The system analysis established the overburden-coal pillar cooperative force mechanical model,combined with the specific parameters of the Heilongguan Coal Industry 11# coal seam,and calculated that the reasonable width of the coal pillar in the section along the goaf roadway at the Heilongguan Coal Industry 11603 working face is 8m.And combined with FLAC3 D numerical simulation software to study the stress distribution characteristics,surrounding rock displacement and plastic zone development of the mining roadways and coal pillars along the goaf during the whole process of excavation and mining in the upper and lower sections when the 8m-wide coal pillars are left.The results show that the 8m wide section coal pillar can ensure the safe mining of the lower section working face.Through the analysis of the deformation and failure characteristics of the surrounding rock of the mining roadway along the gob in the fully mechanized caving face and the surrounding rock control principle of the mining roadway along the gob in the fully mechanized caving face,combined with the specific situation of the Heilongguan Coal Industry,a control plan for the surrounding rock of the roadway along the gob is proposed.,In order to ensure the stability of the section coal pillars and reduce the deformation of the surrounding rock along the goaf roadway under repeated dynamic loads.An 8m-wide section of coal pillars are left on site to carry out the 11603 working face return air tunnel excavation operation.The mining roadways along the goaf can ensure the stability and stability of the coal pillars under the influence of mining on the upper section working face and the driving along the goaf roadway.The normal use of mining roadways and on-site industrial tests have verified the rationality of the method for calculating the section coal pillar width by the overlying rock-coal pillar collaborative force model,It can provide a reference for coal pillar retention in other mine sections.