Abstract:

The modifying agent is very important in ground conditioning of different strata during EPB shield tunneling. The bentonite slurry is a common ground conditioning agent in pure sand stratum, and the polymer is still under experiment. The relationships between characteristics of 3 kinds of polymers and concentration, mixing time and setting time are studied, and then indoor experimental study of slump, permeation and direct shear of coarse sand samples by polymer. The study results show that the fluidity and cohesiveness of coarse sand can be strengthened and the permeability coefficient and friction coefficient of coarse sand can be minimized when injecting 0.3 % PAM polymer for about 20%-25% in coarse sand with water content rate of 10%.

Key words: EPB shield, pure sand stratum, ground conditioning, polymer, experimental investigations