Abstract: To reduce stratum disturbance and settlement during shield tunneling in silty sand layer, a new construction technique of slurry-EPB shield was proposed for the silty sand layer with large permeability and high internal friction angle. 3 groups of slurry permeability test were carried out on mixed soils with different slurry additions using the self-made soil chamber penetrating test device. The variation of pore water pressure in mixed soil and stratum, and the distribution rule of pore water pressure were analyzed. Based on the laboratory testing results, in situ pore water pressure was monitored to study the effect of slurry addition on the pore water pressure in the stratum. The effect of filter cake appears on the excavation surface when the amount of slurry added is more than 25%. The larger the amount of slurry added during the tunneling process, the smaller the change rate of pore water pressure in the stratum. The change rate of pore pressure is only 25%-45% when the addition amount reaches 8 cubic meters per ring. Only the type of infiltration cake occurs in case of slurry-EPB shield, and undergoes slurry particles lost before the film formation. The research results have important significance for the application of slurry-EPB shield in practical engineering and extension to sandy gravel stratum.

Key words: shield tunneling, slurry-EPB shield, infiltration, effect of filter cake, silty sand layer, pore water pressure