Research On The Mechanism Of Clogging Of Cutterhead And The Method Of Soil Conditioning In Strongly Weathered Mixed Granite Stratum

Clogging of cutterhead is one of the main problem that obstructing the shield construction.The mud cake on the cutterhead will reduce the penetration of the cutter,increase the temperature of the excavation surface,and block the opening of the cutterhead,which seriously affects the tunneling efficiency of the shield machine and poses a great threat to the construction and equipment safety.Up to now,the clogging of cutterhead is still a worldwide problem,and there is still no suitable method to completely solve the problem.The study was achieved by literature investigation,theoretical analysis,laboratory test,and field parameter analysis.This thesis mainly studied the mechanism of mud cake formation on the cutterhead and the method of soil conditioning in strongly weathered mixed granite stratum.The mechanism and influencing factors of cutterhead mud cake,the influencing factors of excavation surface temperature and the improvement effect of different improvement methods were explored.The research results can provide reference for similar projects the main research results are as follows:(1)Through literature research and laboratory test,the mechanism and the process of the cutterhead forming mud cake were studied.The study found that the process of the cutterhead forming mud cake can be divided into two stages,one is the adhesion stage and the other is the consolidating and hardening stage.(2)The influence of soil type and consistency index,excavation surface temperature,and excavation surface pressure on the mud cake formed on the cutterhead was investigated through laboratory tests.The effects of three factors on degree of consolidation and difficulty of removal of mud cake were summarized.(3)Through literature research and theoretical analysis,three factors affecting the excavation surface temperature of shield tunneling were selected.With the help of the cutterhead temperature monitoring system,the influence of soil type and consistency index,excavation surface pressure and cutterhead speed on the excavation surface temperature was explored.(4)Relying on the shield tunnel project between Liuxiandong Station and Baimang Station of Shenzhen Metro Line 13,the improvement effects of three methods of soil improvement including moisture content improvement,foaming agent improvement and dispersant improvement were compared through laboratory tests.The advantages and disadvantages of the three improvement methods are analyzed from multiple angles,and the improvement effect of the foam agent improvement method in the strongly weathered mixed granite stratum is analyzed according to the tunneling parameters of the on-site shield machine.