Abstract:

The present study aims to effectively control the muck discharging volume of screw conveyor during earth pressure balance(EPB) shield tunneling. In addition, the effects of the structural characteristics of screw conveyor and soil properties are analyzed. The improved soil in a flow plastic state is assumed to be a Bingham fluid and is expanded into a long rectangular parallel piped discharging soil model based on the screw conveyor structure along its discharging direction. Accordingly, the formula for calculating the theoretical muck discharging volume of the screw conveyor is deduced. The analytical results of the influencing factors of the muck discharge volume are as follows: (1) The muck discharging volume is significantly affected by the support pressure on the excavation face and the initial shear yield stress of the soil. However, it is less affected by the plastic viscosity of the soil. (2) The fluidity of the conditioned soil reduces with an increase in tunnel buried depth and the support pressure of the excavation face. These theoretical results are implemented in guiding soil conditioning during EPB shield tunneling in the shallow overlying fullface sandy soil layer of Guangzhou metro line 21, resulting in a stable supporting pressure of the excavation face and a small surface settlement within 5 mm.

Key words:

earth pressure balance shield, Bingham fluid, flow plasticity, screw conveyor, muck discharge volume