Evaluation Method Of Water Inrush Risk From Coal Seam Floor In Fangezhuang Mine

The Fangezhuang mine belongs to the North China coal field and mainly mines the No.12 coal seam.Its floor is threatened by the Ordovician water pressure of 5-9MPa.Because the water inrush coefficient method is simple and convenient,and its parameters are easy to obtain,the Fangezhuang mine mainly uses this method to evaluate the water inrush risk of Ordovician limestone in the floor,but whether the water inrush coefficient method is applicable is a key issue.Therefore,Based on the current situation of the mine and related policy documents,this thesis is based on the study of geological,hydrogeological conditions and water inrush characteristics,supplemented by the analysis of the fracture characteristics of the mining floor,and a variety of methods to compare and analyze the floor water inrush risk from is the core,summarize the applicable evaluation method,comprehensive analysis study the risk of water inrush in the area,and put forward targeted water prevention and control suggestions.It is of reference significance to realize safe coal mining in similar mines.The thesis obtained the following research results:1.The thesis analyzes the geological and hydrogeological data of the mine,divides the Ordovician limestone water inrush into"sudden"and"lagging"water inrush from the aspects of the water filling source,channel,intensity and time.And proposes a method based on the rich water coefficient method to calculate the new water inflow and stabilize the remaining water inflow to predict the mine's water inflow in the next three years.2.The thesis analyzes the fracture characteristics of the mining floor,and derives the expression of the stress distribution of the floor rock in the transverse and longitudinal sections.Based on the Flac^3D numerical simulation software,the thesis constructs the No.12 coal seam mining model in the study area,and obtains the mining fracture characteristics in three aspects:stress,rock displacement,and plastic zone fracture in the study area.And compared with the empirical formula,it is concluded that the maximum fracture depth of the floor in the study area is 21m.3.In view of the limitations of the water inrush coefficient method,through statistical analysis of multiple water inrush and safe mining data in 7 mining areas,the critical water inrush coefficient equation under the condition of different aquifuge thicknesses is obtained:0<M?30m,T_L=(1/7500)M+0.02;30<M?80m,T_L=0.0027M-0.057;M>80m,T_L=0.06.When there is a water-conducting structure,the distance between the coal seam floor and the highest point of the water-conducting structure should be used as the thickness of floor aquifuge,and the corresponding critical value should be selected for analysis.According to the thickness of floor aquifuge,floor fracture depth,intrusion height of Ordovician limestone,and critical water inrush coefficient equation,five types of floor aquifuge during mining under pressure are divided,and proposed corresponding water prevention and control measures under different aquifuge types.4.The thesis uses the water inrush coefficient method with improved critical water inrush coefficient value,five figures and double coefficients method and vulnerable index method to compare and study the water inrush risk of the floor,and distinguishes the similarities and differences,analyzes the advantages and disadvantages.According to comprehensive analysis,when evaluating the water inrush risk of Ordovician limestone in Fangezhuang mine,the water inrush coefficient method with improved critical water inrush coefficient value should be used for pre-judgment,and the five figures and double coefficients and vulnerable index method should be used for comparative analysis.At the same time,it is also necessary to conduct a comprehensive evaluation based on the exploration of hydrogeological conditions,the study of the water conductivity of large structures,and the water quantity during actual mining.In this way,the study area is divided into four areas:safety area,relative safety area,transition area,and relative danger area of water inrush risk.According to different zones,targeted water prevention and control suggestions are put forward to ensure safe production.and proposes corresponding water prevention and control suggestions for different areas to ensure safe production.This thesis consists of 62 figures,29 tables and 94 references.