Abstract: When EPB shield bores in loess strata, the muck conveying is difficult, the pressure in the excavation chamber is difficult to be established and the temperature of the cutting tools is very high. In this case, ground conditioning by grounding conditioning agents, such as bentonite, is needed so as to ensure successful shield boring. Bentonite slurry optimization test and foam optimization test are made by means of orthogonal test. The optimum concentration of the bentonite conditioning agent and bentonite slurry suitable for loess strata is obtained by means of bentonite slurry optimization test; the relationship between the foam performance and the optimum concentration of the foaming solution is obtained by means of foam optimization test. The paper can provide reference for similar projects in the future.

Key words: shieldbored tunnel, loess, bentonite, ground conditioning, foaming agent, slurry mixing ratio