Hydrodynamic Characteristics Of Long-distance Directional Hole Drainage Engineering Under The Weathering Zone And Dewatering Feasibility

Water gushing from roof and sand/mud bursting are typical safety problems for mining under thin bedrock areas of Jurassic and Permian coal fields in Shanxi,Shaanxi,Mongolia,Henan,Shandong and Anhui provinces.Due to the alternation of deposition and weathering erosion,some mines have special soil-rock contact section structure,the depth and permeability of ancient weathering zone vary greatly,and the fluctuation of ancient topography is difficult to predict,it is often the special place of overburden failure and the easy area of water and sand bursting.It is an effective means to reduce water inflow and sand break by pre-mining geophysical prospecting and drilling,to drain static reserves and to reduce water level.Among them,the upward directional short drill is a common method of exploration and release in advance,and the technology of long-distance directional hole exploration and release developed in recent years is advanced and efficient,but the trajectory design,construction technology,exploration effect and drill hole layout law still need to be studied and tested.The main coal seam of Liangshuijing coal mine in Yulin,Shanbei is 4^-2 coal seam.The aquifer in the weathering zone of bedrock on the top of the seam is a major control factor that restricts the safe mining of the working face,therefore,it is necessary to detect and depressurize the roof aquifer before coal mining.In this thesis,the42207,42208 working face in 422 panel area of the mine is taken as the key research area,by analyzing the coupling relationship between the borehole layout and the hydrodynamic characteristics of groundwater in the process of near-horizontal and long-distance directional hole advanced drainage,the feasibility of the drainage based on the long-distance directional hole and the optimization of the drainage scheme are studied.The main achievements of this thesis are as follows:（1）Based on the background of uneven weathering degree and depth,and uneven aquifer thickness of the direct water-filled aquifer-bedrock weathering zone of 4^-2 coal mining,Based on GIS and AHP,the water-rich zonation of aquifer in weathering zone of bedrock in 422 panel area is evaluated,it provides a basis for the selection of advanced dewatering target for long-distance directional holes.（2）Based on the generalized geological model,the drainage simulation experiment was carried out with the single hole dip angle,length variation and the number of boreholes as the main control factors.By analyzing the change of water inflow and flow field of single hole with different dip angle and length,the influence of dip angle and length of single hole on drainage is discussed,and the optimal drainage parameters are obtained Three sets of multi-hole drainage experiments were carried out based on the optimal parameters of single hole,and the drainage effect was evaluated by the increasing rate of the number of boreholes,the increasing rate of drainage flow and the decreasing rate of drainage time,the results show that excessive drilling can not improve the drainage efficiency,and there is an optimal parameter solution for multi-hole drainage.The simulation test provides a basis for the design of drainage engineering.（3）Combined with the actual situation of the study area,a numerical model of groundwater system is established by using FEFLOW numerical simulation software.The drainage effect of TQ1 long-distance directional borehole is evaluated,and the long-distance directional borehole TQ1 is combined with 3-d groundwater numerical model in the study area,the prediction and analysis model of groundwater flow field of"Pore flow-pipe flow"is established,and the model accords with the actual situation of the study area through the fitting and verification of the discharge data of TQ1 drainage hole,it can be used as an analysis tool for the advanced drainage design of long-distance directional holes.（4）Based on the water-rich zoning,Geophysical prospecting results and laboratory test results,three groups of long-distance directional holes drainage simulation for42207 and 42208 working faces were carried out by using the"Pore flow-pipe flow"calculation model,the variation characteristics of borehole discharge and groundwater flow field during drainage are simulated,and the interaction between borehole layout parameters and groundwater hydrodynamic characteristics is analyzed,it is concluded that the second scheme is the optimal drill hole layout scheme,which can drain the static reserves of the overlying aquifer in the expected time.This thesis has 93 figures,13 tables and 85 references.