Stability Evaluation And Engineering Construction Suitability Analysis Of Coal Mine Goaf In Subway Engineering

Mined-out area,also known as goaf,is derived from human underground activities or natural geological movement,comprising hosts of geohazards like residual deformation,water inrush,and gas explosion.Especially the residual deformation is secluded,complicated,often abruptly occurs after long period,facing the safe production in mining industry.Moreover,with the urban sprawl,mine-out area poses great challenge to constructions like building houses,roads,tunnels,bridges,etc.The existing management and evaluation of stability proves insufficient,because most of time we choose to avoid mined-out area,giving rise to high cost and land waste.To optimize the utilization of above surface,it is imminent to put forward efficient strategies to evaluation of stability of mined-out area and construction suitability.This paper starts with the investigation on coal seam hosting and mining in research area,delineate the actual mined-out area in three stages,e.i.preliminary targeting,modification by geophysical prospecting,drilling verification,and eventually determine three research areas,namely 21 historic coal mine,shaft station,and right K16+200~right K16+300.According to Code for investigation of geotechnical engineering in the coal mine goaf,this paper confirms evaluation indicators of stability of mined-out area based on engineering geological conditions,e.i.geography and geomorphy,formation lithology,geological structure,hydrogeology,natural building material.Based on principal component analysis and factor analysis,the stability of the goaf was evaluated by considering the primary and secondary factors.A 3D geological model based on Surpac software is established to reflect the relationship between aboveground and underground,and determine goaves’ shape,spatial distribution and further calculate their impact distance on the surface,at last support the analysis of construction suitability.The stability of the goaf and the suitability of the project construction are analyzed.The influence distance of the 21 coal goaf is 29 m,and the track 2 is about 11 m.The impact of the K16+200~Right K16+300 goaf needs to be considered.The influence distance of the bottom yard is 11.5m,and some areas overlap with the subway construction area,which has a great impact.Finally,it is proposed to avoid the wellhead and bottom hole yard of the Yanzhang Mine,and use the grouting filling method and the short column support method for the roadway in the right K16+200~right K16+300 of Yaowen section.