Study On Reasonable Retention Of Coal Pillar In Large Mining Height,Thick And Hard Roof Section Of Chahaisu Mine

The layout of double roadways in working face has the advantages of fast excavation speed and relieving the tension of mining continuity.It has been widely used in western mining areas.After double tunneling,the coal pillar between the two roadways is the section coal pillar.During the period of protecting roadway,the pillars in the section are affected by mining for many times.If the size of the pillars is too small,the pillars will be fractured and destroyed,which will lead to the spontaneous combustion of coal left behind when air enters the goaf.If the size of the pillars is too large,not only the waste of coal resources,but also the dynamic disasters such as roof accident and rock burst may be induced.Under the condition of large mining with high and thick hard roof,the law of rock pressure in working face and roadway is obviously different from that in general working face,especially the lateral rock pressure is obvious,the pressure is fast and the intensity is large,which leads to the complex stress environment of coal pillar in the section,and the determination of its reasonable size is more difficult.Based on this,this paper adopts the method of on-site monitoring,theoretical analysis and numerical simulation to carry out in-depth research on the law of mine pressure manifestation in working face,the movement characteristics of overburden strata in goaf,the mechanism of lateral strong mine pressure manifestation in working face and the determination of reasonable size of coal pillar in section.The main work and research results are as follows:(1)Based on the engineering conditions of large mining height and thick hard roof in Chahasu Coal Mine.The monitoring scheme of working resistance,abutment pressure distribution and surrounding rock deformation of hydraulic support in working face is formulated.The working resistance characteristics and resistance increasing characteristics of hydraulic support are obtained.The law of rock pressure appearing in working face is analyzed.The periodic weighting step and the influence range of abutment pressure in 31301 working face are determined.(2)The law of overburden movement in goaf is studied by means of flushing fluid leakage method and borehole television detection method.The development heights of caving zone and fissure zone in goaf of 31301 and 31303 working faces in Chahasu Coal Mine are determined.The relationship between the height of cavingzone and the basic roof thickness is obtained,and the influencing factors of lateral strong rock pressure in working face are analyzed.(3)Based on the characteristics of strata pressure in working face,the position and form of lateral roof breakage in working face are analyzed,the lateral influence range of coal pillar and the size of loosening circle are determined,the mechanical model of lateral arc triangular plate is established,the roof breakage characteristics of Chahasu Coal Mine are studied considering the influence of hard roof,and the rationality of the size of coal pillar in current section is discussed.(4)Taking Chahasu Coal Mine as the engineering background,the FLAC3 D numerical calculation model was established,and the distribution law of vertical stress,displacement and plasticity of coal pillars in different width sections was obtained.Based on the comparative analysis of simulation results and the basic conditions for the stability of coal pillars in the section,the reasonable size of coal pillars in the section under the condition of large mining height and thick hard roof mining was determined.This paper has98 Figs,3 tables and 69 references.