Abstract:

In order to solve problems of earth pressure balance(EPB) shield tunneling in waterrich silty sand stratum, i.e. overlarge torque of cutterhead, difficult control of tunnel face stability and difficult mucking, and improve the safety and stability of EPB shield construction, ground conditioning by thick slurry is proposed by taking the shield section of Wuxi Metro Line No.3 in waterrich silty sand stratum for example. The field test is carried out, and the variation rules of pore water pressure, shield tunneling parameters and ground settlement are studied. The study results show that: (1) By injecting thick slurry of 4 m3 per ring into tunnel face, the slump of soil is improved from 7.5 cm to 14.5 cm, the risks of shield soil chamber closing and soil and water gushing can be decreased, and the fluctuation of earth pressure, shield thrust and torque can be reduced effectively. (2) The slurry film on tunnel face can be formed by thick slurry, which can effectively reduce the pore water pressure to a maximum of 20 kPa. The final ground settlement of section injected with thick slurry is reduced by 26.7% comparing to that without thick slurry.

Key words: waterrich silty sand stratum, EPB shield, ground conditioning by thick slurry, pore water pressure, shield tunneling parameters, ground settlement