Research On Key Parameters And Ventilation Optimization Of Haicang Subsea Tunnel In Construction Period

In recent years,my country’s marine engineering has developed rapidly.As one of the preferred types of cross-sea transportation,the importance of submarine tunnels is self-evident.During the construction of the subsea tunnel,in order to ensure the safety and health of the construction workers and ensure the normal operation of construction machinery and equipment,it is necessary to optimize the design of the ventilation method of the subsea tunnel.Reasonable ventilation types not only send fresh air to the inside of the tunnel,but also remove dust and harmful gases from the tunnel.Based on the Xiamen Haicang Subsea Tunnel,combined with my country’s existing tunnel construction ventilation specifications,according to the construction requirements and engineering characteristics of the Xiamen Haicang Subsea Tunnel,the construction ventilation technology of the Xiamen Haicang Subsea Tunnel is studied,and the Xiamen Haicang Subsea Tunnel is optimized.First of all,this paper conducts a theoretical analysis on the construction ventilation of the subsea tunnel,which mainly includes the basic laws,equations,flow resistance and energy loss of the air flow in the pipeline.Summarized common construction ventilation types,as well as the selection and suggestions of subsea tunnel construction ventilation types,and proposed the calculation of subsea tunnel construction ventilation parameters and the selection of ventilation equipment.Then,relying on the detection and analysis of relevant parameters in the A1 contract section of Xiamen Haicang Subsea Tunnel,the construction ventilation scheme design of the main tunnel,shaft and connecting air duct in the contract section was carried out.This tunnel construction uses two-stage ventilation,namely the first-stage press-in ventilation and the second-stage tunnel ventilation.During construction,it is based on factors such as the maximum number of people in the well,the maximum amount of explosives blasted,the dilution of internal combustion engine emissions,and the minimum allowable wind speed in the well.Comprehensive consideration to determine the required air volume and guide the selection of fan equipment.Based on the interface conditions of the construction site and the original ventilation equipment materials,the program was optimized and designed,and the staged joint series ventilation program was finally determined.Finally,in order to protect the health of the workers and construction safety at the Xiamen Haicang Subsea Tunnel,verify the feasibility and rationality of the optimization of construction ventilation design,and test the air quality at the construction site.Through on-site testing of wind speed,temperature,dust and harmful substances at different mileages and locations in the tunnel,the rationality of the construction ventilation design plan was verified.The test results show that the dust concentration is inversely proportional to the distance from the tunnel excavation face.Under the continuous ventilation of the ventilator,the farther the dust is from the face,the concentration gradually decreases.The concentration of harmful gases is inversely proportional to time.The longer the time,the lower the concentration.In the test range,the wind speed gradually decreases with the increase of the mileage from the tunnel face,but it is still higher than the design requirement.After blasting,the dust and harmful gas will exceed the standard in a short time.With the operation of the ventilation system,the concentration of pollutants will be effectively reduced.By analyzing the test data,feedback and revise the optimization plan of the ventilation design according to the results,so that the ventilation style can achieve the best ventilation effect.