Study On Ground Settlement Control Technology For TBM Driven Tunnel Construction In Sand And Gravel Ground With Abundant Water Of Lanzhou MRT

During the TBM excavation process in sand and gravel ground with abundant water,lag settlement always occur and lead to ground collapse accompanied by a series of secondary disaster,such as underground pipelines burst.The burst of water pipes and gas pipes comes with serious safety risks and bring inconvenience to the public life.Besides,surface subsidence might result in traffic paralysis,especially in cities like Lanzhou,may cause severe impact and property damages to the society eventually.The ground passed through by most of the TBM driven tunnels of Lanzhou Metro line 1 is such kind of formation,which comprises abundant water and ranges from incompact to dense.Therefore,combined with surrounding conditions of the metro line construction site,TBM tunneling status and stratum feature,it is essential to implement ground settlement control technology research during the shield construction process in sand and gravel ground with abundant water.In combination with the shield tunneling construction experience of Lanzhou Metro in sand and gravel ground with abundant water and ground settlement control during the process,this thesis made comparative analysis and summary in model selection,monitoring program and specific technological measures.First,explicit the type selection basis from the operating environment of the TBMs and select self-balanced closed type TBM and its excavation parameters.Second,in line with the actual condition of construction site,designed and carried out ground settlement volume monitoring scheme.Third,systematically expounded the specific technological measures for controlling ground settlement,which provide a certain reference significance for the TBM tunneling construction in sand and gravel formation with abundant water in the future.In the end,this thesis summarized the basis and principle for TBM selection and construction parameter regulation in sand and gravel formation with abudant water.To test the effectiveness of technical measures for ground settlement,the monitoring scheme has been designed and implemented.Mainly discuss the grouting process,mortar configuration,and muck conditioning method.To provide reference for the TBM tunneling construction in similar geological conditions.According to actual conditions of the project,the below TBM tunneling parameters has been summarized: soil chamber pressure: 0.1~0.2Mpa,excavation speed: 30~50mm/min,thrust force: 14000 kN,torque: 4500 kNm,simultaneous grouting pressure: 0.2~0.3Mpa.Finally,the below conclusion has been made: through comprehensive measures,the ground settlement volume can be controlled with an average of 10 mm.Earth Pressure Balanced TBM has good adaptability in sand and gravel ground with abundant water.Secondary grouting measures in the tunnel can improve the excavation speed of the TBM in sand and gravel ground with abundant water.