Dewatering Test Of Ordovician Limestone And Prediction Of Drainage Water Inflow In Deep Mines

Yanzhou mining area is one of the coal industry bases in Shandong province.The lower coal group reserves are relatively abundant.However,the mining of the lower coal group is seriously threatened by the Ordovician limestone aquifer.Water inrush coefficients in most areas of mining areas exceed the critical water inrush coefficients in the Detailed Rules for Coal Mine Water Prevention and Control,which severely restricts the production and development of the lower coal group.Therefore,hydrogeological conditions of the lower coal group are found out,distribution rule of Ordovician limestone karst water in the lower coal group is analyzed,the risk of floor water inrush of the lower coal group is evaluated and water inflow from the Ordovician limestone aquifer is predicted which is of great significance to ensure the safety of exploitation of the lower coal group.In this paper,Xinglongzhuang coal mine was selected as the study area.On the basis of supplementary exploration drilling data,the experimental design of dewatering test from Ordovician limestone was carried out,the dewatering test was participated,the variation characteristics of water quantity,water quality and observation hole water level during dewatering test were analyzed and the important hydrogeological parameters of the Ordovician limestone aquifer were solved by the type curve method,straight line method and recovery of water level method which provided important reference for hydrogeological parameter zoning of groundwater numerical model.Water abundance of middle Ordovician limestone aquifer was studied.We chose five factors(unit inflow of drill,permeability coefficient,leakage volume of drilling fluid,fault density and coring rate)as water abundance factors.The weight values of these factors were calculated,using entropy method.Then a water abundance zoning map in study area was thus obtained.Finally,the areas were classified as: weak,medium and strong water abundance,using weighted fuzzy C-means clustering algorithm.Based on the traditional water inrush coefficient method,considering three factors,which were water inrush coefficient,water abundance index and mudstone thickness in Ordovician limestone filling zone.Then the risk zoning of water inrush from Ordovician limestone aquifer in the lower coal group floor was established,using EM-WFCM clustering algorithm.The areas were classified as: relatively safe,relatively dangerous,and dangerous.The groundwater numerical model of Ordovician limestone aquifer in the study area was established,using FEFLOW groundwater numerical simulation software.Combining with the risk evaluation results of water inrush from Ordovician limestone of lower coal group floor based on EM-WFCM clustering algorithm,the water inflow from Ordovician limestone of lower coal group floor(No.17 coal)in the study area was predicted.