The Investigation And Research On Construction Wastewater In Railway Tunnel

With the rapid development of railway construction projects,the proportion of tunnel engineering in mountainous or heavy hilly areas is increasing day by day,and the environmental pollution and ecological damage caused by tunnel construction has increasingly attracted people's attention.And railway tunnel construction wastewater is considered as one of the most severe pollution source.If the wastewater from tunnel construction is discharged directly without proper disposal,it will definitely pollute the environment.Therefore,it is very important to study on tunnel wastewater treatment technology.On the basis of summarizing and refining the experience of tunnel construction wastewater treatment at home and abroad,combined with the demand of tunnel construction wastewater treatment in construction and planning such as Sichuan Tibet railway,through collecting 278 typical railway tunnels related data of 13 railway projects in southwest,northwest,south China,northeast and other regions of our country,17 of which were selected to carry out a large number of investigations,monitoring,tests and analysis on the construction site.Great progress has been made in the determination of pollutant factors,water quantity calculation,process design and other issues,and a number of valuable scientific research results have been obtained,which have made positive contributions to the treatment of wastewater during tunnel construction and promoted the progress of environmental protection technology in railway construction projects.Through this article,the main conclusions are as follows:(1)The amount of tunnel construction wastewater can be divided into construction wastewater and construction water gushing,of which construction water gushing accounts for the vast majority.Under the current production mode of "combination of clean water and sewage",the scale of wastewater treatment volume in construction tunnel should be calculated after considering the design principles of tunnel drainage and corresponding drainage measures,predicting the normal water inflow in combination with the tunnel and considering the corresponding reduction of water volume(grouting waterproof or drilling drainage holes,etc.).(2)The water inflow of typical railway tunnels fluctuates greatly;Water inflow is closely related to tunnel hydrogeology and engineering geology conditions,aquifer structural characteristics,climate,precipitation conditions,etc.(3)For the first time,the main pollutant factors in the wastewater were determined to be SS and pH,with SS concentration ranging from 73 mg/L to 6250 mg/L and pH ranging from 7 to 13.Among them,SS concentration in construction waste water is related to rock property of excavation section,type of opening(downstream/reverse slope),water volume(flow rate),etc.The pH in waste water is weakly alkaline or alkaline,and the problem of effluent pH exceeding the standard(pH > 9.0)is more prominent.(4)Combined with field test research and process optimization verification,the "air flotation" unit has a low contribution rate to the removal of pollutants from construction wastewater.It is suggested to cancel the "air flotation" unit and supplement the "sand settling" and "pH condition" units.Through this article,it is hoped that railway environmental protection designers can find a more reasonable and perfect design scheme,thus further studying the feasibility of the " Clear water and sewage diversion " scheme to reduce water from the source in engineering application.