SHIELD MACHINE

PROBLEM TO BE SOLVED: To provide an earth pressure balancing device of a shield machine capable of coping with the sudden change of earth pressure in a chamber, in a case when a tunnel is excavated by the shield machine at a place of shallow earth covering or a place where the sediment load is easily generated. SOLUTION: The earth pressure in the chamber is detected by plural earth pressure sensors, and operating parts of plural earth pressure balancing devices mounted on an upper part of the chamber are controlled on the basis of detection values of the earth ground sensors to cope with the change of the earth pressure in the chamber. Further the injection of additives is controlled on the basis of the detection values of the sensors.