Study On The Disaster Mechanism Induced By Far-field Key Strata And The Prevention Technology In Buertai Coal Mine

To support the high-speed economic development,high production and considerable efficiency are required in coal mines.In recent years,the deeper resource was excavated because the current shallow-buried resource is unequal to meet the large need.The strata pressure mechanism of strata movement becomes more complicated,as the damage scope of overburden is more higher due to the high accumulated mining height while mine the deep resource.Undoubtedly,it is difficult to make clear ground pressure mechanism and work out original prevention measures,if only focus on the key strata around coal seam.Consequently,there is a inevitable trend to study the breaking characteristic of far-field key strata.Aiming at the periodical strong ground pressure behavior during mining process in Buertai Coal Mine,some methods were adopted to study the disaster mechanism of far-field key strata and stope surrounding rock control technology,including site measurement,theoretical analysis,physical model,numerical simulation,even a case study.The results indicated that the intensity of ground pressure behavior varies with a changing interval.There are several thick and hard strata in far-field overburden,which were distinguished as ones of key strata.The initial weighting interval of far-field key strata is roughly equivalent to the periodical,breaking into trapezoid plates and arc triangle plates.Based on this,the root reason for strong ground pressure behavior is the instability of breaking blocks in a large space.Compared with near-field key strata,the weighting intervals of far-field key strata are longer,the loading heavier,and the influence scope wider.Far-field breaking will lead to advanced breaking of the nearfield key strata and synchronous subsidence of whole overburden,which causes strong ground pressure in working face.It works out in this paper through numerical simulation that weaking the mechanic characteristics of key strata can control strong pressure problem effectively.Discussed in more detail,the control effect seems to be the best when weak far-field and near-field key strata simultaneously,ranks second when only weak the far-field,and appears the last when only weak the near-field.However,all of the three methods can reduce the bearing stress in coal body and pillars to some extent.Besides,a case study about weaking measure was conducted in nearfield key strata.After that,the average support resistance reduced from 22,333 kN to 19,616 kN,the periodical weigthing interval decreased from 20.9 m to 16.7 m,and the continuous length reduced from 7.4 m to 4.8 m.This practice shows that weaking the mechanic characteristics of thick and hard strata can control strong ground pressure effectively,which provide engineering experience and reference value for safe mining in the similar situation.There are 43 figures,12 tables,and 103 reference papers in the thesis.