Research On Technologies Of Gas Drainage With Horizontal Long Borehole In Lower Slices Of Extremely Thick Coal Seam In Tingnan Coal Mine

The slice mining of high-gas thick seam cause bottom slicing relief gas flows into the goaf,gas transfinite happen rather often at upper corner.The main mining seam 4#coal bed of Tingnan mine belongs to the kind of high-gas special thick seam,in the light of the upper corner gas overrun,the gas extraction technology of long horizontal hole is studied.The gas extraction technology of long horizontal hole has a great influence on the gas control of high gas thick coal seam.It has important theoretical significance and practical application value.The following factors should be considered in the layout of the bottom slicing borehole,the stability of the borehole,the flow rule of the relief gas,the influence range of the borehole extraction and the effect of the extraction.In order to obtain the parameters of hole distribution,the paper uses research method of the theoretical analysis,the value simulation,the laboratory experiment,the scene commercial test,the selection basis of the parameters of the hole is studied deeply,caring out 205 working surface coal bed’s gas parameter test,analyzing the regulation of gas emission for neighboring working surface,studying in the lamination mining process the working surface gas to gush out the origin constitution,and the feasibility of gas drainage by horizontal long borehole.In the process of the upper layer mining,abutment pressure acting on drilling located in the lower layer,the borehole stability under loading and unloading is studied.A model for calculating the shear stress around the borehole is established,the stress rate of loading and unloading is taken into account in the model.The relationship between loading-unloading function and the damage range of drilling perimeter is analyzed.The range of borehole stability in the 205 working face is given.According to the numerical results,the stress variation law of different layers in the lower layer is obtained,according to the stress variation law the coal sample permeability experiment was carried out.The permeability evolution law of mining process is obtained,and the relationship between permeability and stress is established.The numerical calculation model of pressure relief gas flow in slicing coal is established.The model is used to analyze the influence of different layers and different spacing on the influence range and quantity of extraction.According to the requirement of gas drainage quantity and the gas drainage capacity of different layers determines hole distribution layer.Finally,considering the two factors of borehole stability and gas drainage requirements,the drilling hole is determined.Based on that,studied the other parameters of the hole and equipment further.At the same time,the field test is carried out,and hole arrangement parameters of the horizontal long hole drainage are determined.The technology of horizontal long drilling extracting for the next lamination of pavilion south mining thick coal seam can solve the problem of missive gas gushing out of the working surface for the lower slicing of the thick coal seam.It provides new ideas of gas control when slicing mining for other high-gas thick seam mine pit.