Mechanism and full-time-space prevention and control technology of water inrush from Ordovician and thin limestone in deep mines

The rock structure model of Ordovician limestone +thin limestone placed in between thick aquifuges+coal seam is the typical existence form of Permo-Carboniferous coalfields mining under pressure in China. Although the aquifuge is extremely thick,it is frequently affected by water inrush in deep mining because of the thin limestone aqui- fer. Due to the limitation of the water inrush coefficient,based on the thickness of the aquifuge,the height of the floor damage zone as well as the height of fracturing belt of the Ordovician Limestone,and the water inrush coefficient,this paper classifies the floor aquifuge into five categories:extremely thin,thin,medium,thick and extremely thick,and re- duces the application role of water inrush coefficient in extremely thin,thick and extremely thick aquifuge. This paper describes the unique role of thin Limestone in the formation of water disaster in series between Ordovician Limestone and coal seams,defines the concept of water disaster and water inrush pattern of deep floor Ordovician Limestone and thin Limestone. The characteristics of its five dimensions are also summarized as the total source progression of the wa- ter filling source,the planar dispersion of the water filling channel,the step increase of the water filling intensity,the hysteretic effluent of the water filling time,and the exchange and adsorption of the water quality of the water filling source. The water inrush mechanism is clarified that the permeability, dilatancy, fracturing, and rise of Ordovician Limestone water form a planar and divergent flow by the transfer,storage and transportation of thin Limestone,and the corresponding water inrush risk evaluation formula P0 >3σ3 -σ1 -Pp +Rm is also proposed. The water inrush cannot be completely controlled by the traditional underground floor reinforcement or even the regional treatment under extremely thick aquifuge,the “whole time-space” comprehensive prevention and control concept of the four-dimensional Ordovi- cian Limestone and thin Limestone water disaster in whole time and space domain is innovated,and in the space,a full-space multi-layer three-dimensional network prevention and control layout is formed,which combines the top and bottom of the mine,the combination of multi-level regional treatment of Ordovician Limestone and thin Limestone,and the exploration,treatment and verification of underground thin Limestone drilling,creating the " whole space" tridimen- sional prevention and control model of whole space three-dimensional crossover network exploration,treatment,verifi- cation,and supplement,forming a whole time domain “ Four-in-One” technology quality control process of condition assessment,and exploration,treatment,verification as well as supplement,and inspection evaluation,and monitoring and guarantee,and establishing a deep floor Ordovician Limestone and thin Limestone water disaster prevention meth- od with “Four-in-One” whole time-space tridimensional network. Taking the 2603 working face of Wutongzhuang mine field in the Hanxing mine area as an engineering case,the paper determined that 40-60 m and 20-30 m below the top surface of the Ordovician Limestone,and the Daqing thin Limestone and Shanfuqing Limestone were the targets to car- ry out the advanced regional treatment and supplementary treatment of the multi-layer section,and formed a three-di- mensional network treatment with Yeqing and Shanfuqing Limestone as the target of underground supplementary treat- ment and verification. The Ordovician Limestone and thin Limestone hydrogeological condition assessment is used to determine the treatment goal in the paper,and the surface area exploration and treatment,supplementary exploration and treatment,as well as traditional underground inspection are used to verify the preliminary treatment effect,and the comprehensive evaluation of whether the working face can be mined with the verification of treatment effect,the evalu- ation of the integrity of the floor,the evaluation of water inrush risk,the prediction of water inflow,and the evaluation of the drainage capacity. In the process of coal mining,the hydrologic monitoring,micro seismic system,mine pressure monitoring system and other comprehensive means are adopted to pay close attention to the key stratum of the thin Limestone,so as to realize the safe mining of the working face.