The Research Of Waste Mud Separation Technology That During The Subway Retaining Structure Construction

During the construction of the subway station,the palisade structure construction plan with underground continuous wall,and this method is to use slurry-supported into a trough and placing of concrete under the mud,inevitably there will be in the construction process of deterioration of nature can’t reuse of metamorphic mud produced,also can produce a large number of surplus mud after completion.It may pollute the ground environment and affect the progress if not handled in time;It may cause secondary pollution if not handled properly.Subway construction is often the most prosperous commercial center in the city and traffic zones,space narrow,general construction machinery to reasonable decorate,less likely to set several big mud pit at the same time,so how to solve the problem of waste mud treatment is very important.This study of shenzhen metro line 7 as the research object,through the shenzhen metro line no.7 construction of underground continuous wall mud mud separation test,research and practical application,summed up the quality is reliable,high efficiency,low cost of mud separation technology,for similar urban rail transit construction to provide a meaningful reference and application example.The main conclusions of this study are:1.Combined with methods of waste mud treatment at home and abroad and the development trend,the proposed short processing cycle,covers an area of less,low cost,wide prospect of application of chemical flocculation and mechanical dehydration process.Using mud chemical flocculation separation and centrifugal separation technology for solid-liquid separation of mud,formed a "screening + flocculation dewatering" secondary processing system.2.To the physical and chemical properties of shenzhen metro line 7 mud determination and flocculating test analysis.The test results show that the inorganic flocculant for sludge treatment effect is weak,and organic polymer flocculant treatment effect is obvious.For mud bentonite mud,anionic polyacrylamide treatment effect is better,and field test result is good;For clay mud,nonionic polyacrylamide treatment effect is good.Adopt direct solid dosing.3.For bentonite mud,the best flocculant dosing quantity is 0.27 g/100 mL;Best stirring strength of 450 r/min,the best mixing time for 3 min.For clay slurry,the best flocculant dosing quantity is 0.15 g/100 mL;Best stirring strength of 450 r/min,the best mixing time is 4 min.4.The flocculation supernatant of each index were measured before and after.Each site mud all the indexes reach the sewage discharged into urban sewage water quality standard（CJ₃43-2010）level of emission standards,and flocculating agent under the condition of appropriate dosage,the index is still within the standard.5.Based on shenzhen metro line no.7 construction the existing treatment technology research investigation,to determine the "mud to desander,mud pools dosing stir-dewatering equipment spate separation" of the process,choose LW type horizontal screw centrifuge dewatering equipment,and according to the requirements and the energy consumption rate of the specific site in the comprehensive consideration to choose different types of centrifuge.6.To estimate of processing costs,it is concluded that for bentonite mud,processing cost about 25.4 yuan/m3,the clay slurry,dosing cost about 19.2 yuan/m3（mud outward processing fees according to different regions of about 55-120 yuan/m3,such as nanjing ning and inter-city rail transit mud outbound processing cost is 110.8 yuan/m3）.After dosing process,supernatant can be directly discharging standard,the sediment landfill,compared with the mud overall outbound processing,cost reduction,and had a higher environmental protection significance.