Technology of Slurry Shield Crossing High Infilt...
The stratum in the middle section of the river crossing by slurry shield is generally complex.Therefore，according to different geological conditions，the corresponding construction technology is adopted to ensure the safe and efficient tunneling of shield.Due to its high permeability coefficient and low clay content，the high permeability gravel composite stratum is prone to serious mud filtration in construction，and the excavation face is difficult to form a mud film and lose stability.For example，during the construction of the middle section of the Yangtze River Tunnel in Nanjing，the mixed stratum of fine sand and gravel layer，and the round gravel layer with a length of about 370 m and a thickness of 0-3.9 m and the strongly weathered calcareous mudstone layer are encountered.Due to the soft and hard lithology of the stratum，the nature of the stratum is obviously different，and the pebble stratum is easy to cause the blockage of the excavation chamber and the damage of the cutter.The formation permeability coefficient is as high as 10-2 cm/s，and the coarse particles larger than 2 mm account for about 40％of the whole formation content，and the clay content is very small.This situation is not conducive to the formation of mud film on the excavation surface of slurry shield，and it is prone to the problem that the pressure balance on the excavation surface cannot be established due to the large amount of mud filtration.At the same time，the maximum working pressure of about 0.65 MPa of Nanjing Yangtze River Tunnel shield also increases the risk of crossing the river，which is also a test for the shield itself and the construction processed the risk of crossing the river，which is also a test for the shield itself and the construction process.
This chapter introduces the technology of slurry shield crossing the middle Yangtze River composite stratum from three aspects：high permeability and waterrich gravel composite stratum tunneling，slurry preparation and film forming technology，slurry circulation and slag carrying capacity calculation and analysis，which provides reference for future shield tunnel crossing high permeability composite stratum.
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J.Chen et al.，Construction Technology of Large Diameter Underwater Shield Tunnel，Key Technologies for Tunnel Construction under Complex Geological and Environmental Conditions，https://doi.org/10.1007/978-981-16-5896-9_5