Influence Of Atmospheric Precipitation On Coal Inflow In Southwest Mountainous Areas And Its Prediction

Coal mine water inflow is the amount of water influxed into coal mine in a unit time,and it is an important index to evaluate the severity of a coal mine water disaster.Before or during coal mining,we should forecast the water inflow and monitor it dynamically so that measures can be taken to adjust the drainage capacity in time before or after the occurrence of water hazards so as to ensure mine safety.In this paper,Xiaotun Mine is taken as the research object.On the basis of collecting and summarizing hydrogeological data,mining data and measured data of atmospheric precipitation-water inflow,the influence of atmospheric precipitation on mine water filling is analyzed.Then the time series analysis and lag analysis of precipitation-water inflow are carried out by using time series analysis method.On this basis,a transfer function model for forecasting the inflow of water in flood season is attempted to be established.Finally,in order to better predict the water inflow of coal mines in southwest mountainous areas under the influence of atmospheric precipitation,further attempts are made to predict the water inflow at different stages in Xiaotun Mine by combining the infiltration coefficient method of atmospheric precipitation with the analytical method and the three-dimensional geological model method of Feflow.The characteristics and accuracy of each method are analyzed.The main research results and conclusions are summarized as follows:1)On the basis of detailed analysis and summary of mining area data,it is recognized that mine water inflow is closely related to atmospheric precipitation,which is the main source of water inrush in Xiaotun mining area.Atmospheric precipitation recharges underground aquifers and enters mines with good runoff channels,which are mainly karst channels,mining fissures and large-scale faults.The upper karst landform of Yulongshan section is relatively developed.Where the upper Jiujitan relative water-proof layer lacks,especially in low-lying areas,atmospheric precipitation enters the limestone aquifer of Yulongshan through karst monomer,and the water pressure of Yulongshan increases in rainy season.The mining fissures can pass through Changxing aquifer and destroy the water resistance of Shabaowan relative aquifer.Under the cross-influence of the two,meteoric water affects and controls the water inflow of Xiaotun Mine.2)The correlation and hysteresis of different time scales in Xiaotun Mine are analyzed by statistical means.First is the situation in 2008-2017,there is a significant correlation between rainfall and water inrush drawn from the whole.Then the time series is analyzed in normal season and rainy season.Although there is some correlation between the two time series in normal season,the synchronization is very poor.The correlation between the two time series in rainy season is obviously enhanced.The peak values of water inflow and rainfall occur in rainy season.Although the peak values of water inflow are slightly delayed compared with rainfall,they are almost synchronized,and both of them fluctuate greatly in rainy season.It is found that the inflow of water in flood season is greatly affected by atmospheric precipitation,and because most of the heavy rainfall in this area is concentrated in the flood season,the time of maximum fluctuation and maximum value of inflow mostly occurs in the flood season.Therefore,the time scale is drawn to the day,and the variation rule of water inflow after each rainfall in flood season is observed in detail.It is concluded that the lag period of the two is 0-4 days.3)On the basis of lag analysis,a transfer function prediction model suitable for the current mining situation of a mining area is established by using the measured data,and the residual analysis of the model is carried out.After that,the model is used to validate and predict the 2017 flood season water inflow in a mining area.It is found that the average accuracy can reach 5.59% and the maximum error is only about 14%.It provides a feasible idea for precise prediction of mine rainfall in flood season.4)The method of combining precipitation infiltration coefficient with analytical method is used to predict the water inflow in Xiaotun Mine.The water inflow in the first mining area is forecasted in four cases: no rainfall,normal rainy season,flood season and rainstorm season.Among them,the water inflow without precipitation is predicted by the big well method,while the other three cases are predicted by the sum of the predicted values of the big well method and the precipitation infiltration coefficient method.It is found that the prediction error of this method is stable at about 12%.After that,the method is applied to the fifth mining areas,and the mine water inflow is predicted in four cases,a realistic prediction result is obtained.5)The three-dimensional hydrogeological model of the study area of the first and the fifth mining areas is established by using Feflow.Then the model is adjusted,partitioned and initial conditions are set.The model is also identified by the actual mining situation of the first mining area.It is found that the error between the predicted value and the actual value of 2017 flood season in the first mining area can be stabilized at about 10%.After that,the model is applied in the fifth mining area,and the prediction is divided into four cases in the same way as the former method.The prediction results are close to the combined prediction results.6)In view of the relationship between water inflow and precipitation in Xiaotun Mine obtained from the above analysis,we should strengthen the measures of “drainage,drainage and interception”.This paper has 45 figures,18 tables,95 references.