ABSTRACT
Soil clogging frequently happens when earth pressure balance (EPB) shield passes through clayey or clay-rich rock ground and tends to be responsible for abrasion of disk cutter, excessive thrust and torque, low advancing speed, and even blocked cutterhead. To avoid the clogging of shield, the auxiliary air pressure balance mode is widely applied in Guangzhou, China. Based a construction case in Guangzhou Metro Line 21, the soil conditioning for the auxiliary air pressure balance mode was studied in the slightly weathered conglomerate formation with an average uniaxial compressive strength of 29.7 MPa. This research shows that the effect of foam was better than that of dispersant. The ideal value of slump test for the muck was in the range of 2~6 cm to avoid muck spewing and hold the pressure in the excavation chamber. This study provides a good reference for EPB shield tunneling in conglomerate formation.
