Study On Overlying Strata Movement Laws Of Underlying Coal Seam Mining In Proximity Under The Influence Of Residual Coal Pillars

The abnormal mining pressure and the damage of overlying stratas caused by the mining in proximity under influence of residual coal pillars will affect the production of the working face seriously.Under the action of mining,the roof pressure caused by the instability of the coal pillars and the connection of the adjacent goaf are the major threats to coal mining.Therefore,the paper studies the failure mechanism of coal pillar and the laws of overlying strata movement beneath the goaf through the field investigation and numerical calculation,which provides important basis for the mining design of Yuanbaowan coal mine.This paper carries on the spot survey to the goaf of the coal seam in Yuanbaowan coal mine to undersand the damage conditions of roofs and coal pillars in the goaf currently.Then geometric and distribution characteristics of coal pillars are described,and the main failure forms of coal pillars are also analyzed.By monitoring the crack development of coal pillars in goaf under the influence of No.6 coal seam mining via using FISH language in UDEC,the failure mechanism of coal pillar is obtained in detail by analyzing the failure forms and stress distribution characteristics of coal pillar comprehensively.In addition,the abutment pressure distribution and failure characteristics of overlying strata caused by concentrated stress of coal pillars during the process of advancing face are summarized.It is found that the concentrated stress of coal pillar in goaf is the main reason that result in the support accident.The mining height has little influence on the abutment pressure distribution,but it is the main factor that control the height of the caving zone in the 6104 working face.The measures that feasibility and technical are put forward for No.4 and No.6 coal seam respectively,it is considered that reducing the mining height of No.6 coal seam is the effective way to control the hidden dangers of roof.According to the theoretical and numerical calculation results,the maximum mining height is caculated to ensure the safe mining for the 6104 working face,and the maximum working resistance of the hydraulic support on the working face is also determined according to the roof conditions.