Abstract:

The cutting tool replacement of earth pressure balance (EPB) shield used in Xi’an Metro has many difficulties, i.e. difficult pressure maintaining of earth chamber, difficult pressure control of earth chamber and high risk. As a result, technologies for shield cutting toll replacement under hyperbaric condition are studied. Key operation points are summarized as follows: 1）The pressure of earth chamber becomes stable by carrying out tunnel face closing and pressure maintaining test. 2) Increasing the air pressure with rate of 10 kPa/min after the working personnel entering the chamber, and reducing the air pressure gradually in four phases with rate of 10 kPa/min before the working personnel leaving the chamber. 3) A detailed construction plan should be made before replacing the cutting tools; and then the cutterhead needs to roll by 3 times to complete cutting tool replacement. The results show that it can meet the construction requirements of shield cutting tool replacement under hyperbaric condition in waterrich and compact sandy stratum of Xi’an Metro by adopting the abovementioned technologies.

Key words: Xi’an Metro, waterrich, compact sand, cutting tool replacement under hyperbaric condition, bentonite, filter membrane