Abstract: In slurry shield construction, forming a filter cake in time is important for working face stability; the slurry pressure could be transferred into effective stress with filter cake then acting on the working face. The filter cake on the working face is dynamic, thus the forming time of filter cake is the main factor which could affect the supporting for working face. An apparatus is designed which could measure the excess pore pressure in the stratum. Infiltration tests are done in three kinds of high permeability strata with five kinds of slurry to study the forming time of filter cake, its supporting ability and the influencing factors. The results indicate that the forming time of filter cake is 10 seconds in only filter cake infiltration styles. The slurry property and the grain size of stratum have important effects on the forming time of filter cake. The filter cake forming time in part of large slurry shields at home and abroad is also discussed; and the results indicate that the time from destruction to re-destruction of filter cake is ranged from 5 seconds to 20 seconds; thus the property of slurry should be suitable to ensure that the forming time of filter is less than the time from destruction to re-destruction of filter cake.

Key words: slurry shield, filter cake, forming time, influencing factors