Discussion of the modification plan of the EPB TBM applied in a water-rich cobblestone stratum in Chengdu

The shield construction technique was successfully used in the Chengdu metro lines 1 and 2. Because of the geological conditions of water-rich cobblestone, this project suffered from a high cost of cutter consumption, difficult cutter changing, surface subsidence, and serious wear to the cutter head and screw conveyor. By analyzing the geological features and advantages and disadvantages of the devices currently used on shield machines, a modification plan for the shield is suggested, including changing from a breasting plate to a spoke for the cutter head, from a shaft to belt for the conveyor, and from main breaking to total discharging, which resulted in greatly reduced construction costs.