| According to incomplete statistics,from the founding of the People’s Republic of China to2017,my country has built no less than 205 gas tunnels.Gas disaster is a serious geological disaster during the construction of a tunnel.There is a huge risk in the construction of a gas tunnel.How to effectively control the gas concentration within the prescribed limits is an important task for the safe construction of a gas tunnel.This paper takes the Niutongshan gas tunnel as the research background and analyzes the influence of the air duct layout parameters on the gas distribution law based on Fluent software;the effect of the tunnel’s sprayed concrete wall roughness on the friction resistance coefficient is studied;combining the wind flow field and gas Based on the study of the concentration field law,a detection and monitoring plan for the construction ventilation of Niutongshan Gas Tunnel is proposed.The main research results of this article are as follows:1.Combined with the reality of the Niudongshan Gas Tunnel Project on the Pumei Railway,a transient numerical model was established for the tunnel based on the Fluent software finite volume method.The laws of jet wind flow field and gas diffusion in a limited space are analyzed,and the ventilation effect of Niutongshan gas tunnel is evaluated.Based on the air flow and gas distribution rules of Niutong Mountain Tunnel,gas detection and ventilation monitoring suggestions are proposed for the construction of similar gas tunnels.2.The numerical method of Fluent software was used to establish the gas migration model in the tunnel,and the different duct diameters,the distances of different duct openings from the palm face,the different duct suspension positions and the different duct ducting degrees were studied in detail.The influence of the parameters of each duct arrangement on the wind flow field and gas distribution law of the tunnel determines the optimal duct diameter,the distance of the duct opening from the palm face,the duct suspension position and the duct attachment under four parameters under a single variable Wall level.And orthogonal test was used to analyze the influence of various factors on the gas emission effect,and on this basis,the best air duct layout was determined.It is proved whether there are interactions among the four factors.3.After the tunnel is constructed by drilling and blasting,its excavation profile inevitably forms irregular geometric features,which simplifies the tunnel wall.Taking into account the shape,spacing and height of the rough elements,the effect of the tunnel wall roughness on the coefficient of frictional resistance was studied.The orthogonal test was used to analyze the influence of various factors on the friction coefficient.From the perspective of construction ventilation,suggestions were made for the conditions of the sprayed concrete wall surface,and the reference value of the sprayed concrete wall friction coefficient was proposed.4.Proposed the detection and monitoring plan of wind speed,air volume and gas concentration for Niutong Mountain Tunnel.The corresponding emergency plan measures in the event of an accident in the gas tunnel are explained. |
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