Gob-side Entry Retaining By Downward Y-tipe Ventilation And Gangue&sandbag Filling Technique In Gently Inclined And Thin Seam

In the traditional roadway maintenance, the common way was setting up coal pillarand it would be resulted in vast loss of coal resources. In order to raise the efficiency ofthe coal mining, enhance the coal resources recovery, more and more coal minesenforce maintain roadway by the way of gob-side entry retaining. The superiority of thismethod is obvious: reducing the amount of roadway excavation, improving recoverypercentage of coal, higher economic benefit and so on. The most important part of thismethod is selecting reasonable roadside support and entry-in support. So it’s veryessential to research the support ways firstly.The U-tipe ventilation system usually used in the past fails to deal with theproblem of gas overrunning in the roadway, especially the upper corner. However, theY-type ventilation system with two inlets and one return can solve the problem if the airvolume of main and secondary inlets distributed reasonably, because the lowest energypoint is located at the end of the gob-side entry retaining. In addition, it obviouslyreduces the air volume of working face and dust concentration. It greatly improves theworking environment.Based on the site condition in gently inclined and thin coal seam of2443face ofNo.1mine of Sanhui, compare three supporting ways of gob-side entry retaining byusing research of theoretical analysis, numerical analysis and field experiment. Theresults are as below:(1) Analyze the moving rule of surrounding rock and established gob-side entryretaining mechanics calculation model as the basis for supporting design.(2) After analyzing the activity rhythm of surrounding rock and common way ofroadside support and roadway support, three supporting ways were put forward. Methodone: gangue and sandbag support in roadside and joist steel support in roadway；Methodtwo: masonry support in roadside and joist steel support in roadway；Method three: pinepillar support in roadside and joist steel support in roadway.(3) The numerical analysis software UDEC was adopted and analyzed thedeformation of surrounding rock of the three supporting ways. Method one wasdetermined to use for field tests by comparison analysis.(4) According to the computing principle of air volume at working face, the airvolume should be calculated in accordance with gas emission, temperature and number of workers of the working face. Then take its maximum and check whether the air speedmeets the safety rule of0.25～4m/s. At last, the air volume is confirmed to be840m~3/min, and the ratio of the air volume of main and secondary inlets debugs to be3:1.In this way the effect of gas control and dust exhaust is outstanding.(5) After field experiment, underground pressure monitoring, ventilationmonitoring and economic analysis, the result showed the downward Y-type ventilationand gangue&sandbag filling technique was reasonable and economical and the directeconomic benefits amounted to RMB￥4.659million.