Study On The Gas Prevention And Control Of Ping-Zi-Shang Railway Tunnel

Since more and more tunnels passing through coal-bearing strata, gas accidents are on the rise accompanying the tunnel construction in west china, which form a great threat to the safety of the tunnels and constructors. Many technology challenges need to be overcome to effectively prevent and control the disaster of the construction of gas tunnels. This paper study the drainage borehole and construction ventilation technology, the gas migration law in the process of gas tunnel excavation by using numerical analysis and field test. The main contents and results are listed as follows:(1) Based on previous literature and fluid-solid coupling, this paper summarizes the gas migration law, and propose method for predicting gas emission law. The gas pressure decreases with the emission time. The gas overflow into tunnel through new exposed working face and the tunnel wall, and gas vector distribution changes with the distance between the working face.(2) Based on the numerical simulation of gas tunnel discharge, the relationship between the effective radius and the aperture and the time of the gas borehole and analysis reasonable space setting.The discharge radius increases obviously with the increase of the radius of the discharge hole and the discharge time.Borehole depth has little influence on the effective radius.The law of gas emission is the same under the straight hole and inclined hole.In order to prevent the emergence of the blank zone of the gas emission, the distance between the gas drainage holes should be set more reasonable with the space formulas.(3) Based on the construction progress and numerical simulation, this paper studies the ventilation mode of the Pingzishang gas tunnel, and optimizes the construction ventilation parameters. According to the construction schedule,the Pingzishang gas tunnel used a variety of ventilation,using single pressure ventilation in front of fourth cross passages and using gallery ventilation after fourth cross passages.The distance of mouth wind belt of installation allocations and tunnel face have obvious influences of gas concentration in the tunnel when use single pressure ventilation.