The Research Of Tubes Push-Construction Ventilation Based On Highway Tunnel

In the process of municipal and subway’s tunnel construction, blasting、machine operation and excavation strata are interested in cave air pollution.in order to improve the working environment and protect the health of construction workers, appropriate ventilation measures must be taken. Forced ventilation is the most commonly used ventilation in the tunnel construction. In order to improve ineffective tunnel ventilation and optimize the ventilation of the design, as the background of the engineering to Huaying-Mountain Tunnel for Nanchong-Dazhu-Liangping highway (Sichuan-Chongqing Border), some key issues are analysed for press-in ventilation ventilation system relying on the use of scientific theoretical analysis, numerical calculation and on-site testing. Main super long highway tunnel construction ventilation one-dimensional numerical model (The toxic and harmful gas), full-face pressed into the local construction ventilation, head-gas emission law, step method of local construction ventilation, gas emission and jet fan arranged study on tunnel toxic and harmful gas diffusion after blasting the law of the field test.The main conclusions are:(1)One-dimensional transient numerical model is established based on the finite volume method for super long highway tunnel construction ventilation.(2) In full face pressed type construction ventilation, the distance of the wind pipe for duct mouth to working face laying pipe should be shortened,and the duct and the tunnel wall affixed to the degree is improved, but to avoid a short distance or high degree of mural the larger the pressure loss.So the distance is maintained fromlOm to20m, and the wind pipe is installed in the tunnel wall and vault.(3)It keeps at high concentrations for the gas concentration gradient within recirculation zone close the gas head-on gush1.0m,simultaneously the gas concentration in the recirculation zone is higher compared with the jet area; Gas emission greater the amount of gas along the roof countercurrent greater the distance, the vault more prone to gas accumulation; Gas emission in the size of the original flow field has a certain influence, the smaller gas emission, the smaller impact of airflow stream; The problem of gas emission accumulation can be solved by means of increasing the amount of ventilation.(4)InThe bench method steps of pressure into the construction ventilation, as top step length from5m to20m or so, It not only takes into account the impact of the working face of the jet on the stage, but also control down the steps before the vortex size and jet the amount of air entrainment; It achieves the best ventilation effect by the side wall of the duct along the nozzle to the working face about from the5m to10m. (5)It is shown that by field test:as the main product of the blasting operations for CO and H2S,which is judged by the condition of the tunnel pollutants and studied the control indicators of the law for toxic and harmful gas diffusion. After the tunnel face blasting, concentration of CO and H2S have the more obvious changes with time, meanwhile diffusion exhibits a consistent continuity and similarity. The peak of CO and H2S diffusion is getting smaller and smaller from the tunnel face to the direction of the hole, moreover more and more time exceeds the allow able concentration range and a more wide range. The diffusion distribution takes on:" high in the middle on both sides," comes to too slow". Ventilation diffusion is the main driving force of the migration of contaminants to the outside the cave.The pollutant dispersion speed large part determined by the cave wind, so ventilation should be strengthened for highway that contains toxic and harmful gases tunnel, and increase the the cave ventilation rate or wind appropriate.