Abstract:

The geological condition in Chengdu is famous for rich water and high gravel content. Therefore, the topic that what kind of shield is suitable for Chengdu’s geological condition has been the focus of controversy. During the construction of the 4 shieldbored tunnel contract sections on Phase 1 project of Line 1 of Chengdu Metro, problems such as high cutterhead consumption cost, being difficult to replace the cutting tools, the ground surface being subject to collapse and serious attrition of the cutterhead and the screw conveyor. Analysis is made on the advantages and disadvantages of the shield equipment and countermeasures, such as increasing the cutter head’s opening ratio, shifting the screw conveyor from shafttype screw conveyer to belttype one and treating the gravel from breaking primarily to discharging primarily, are proposed so as to minimize the cutting tool cost. Furthermore, proper modification is made on the cutter head and on the front shield so as to facilitate the cutting tool replacement and to avoid ground surface settlement. The modified shields are more suitable for the construction of Chengdu Metro.