Discussion of cutter-head opening design for earth pressure balance machines (EPBMs)

Abstract

Among the various parts of earth pressure balance (EPB) cutter-heads, the opening distribution on the cutter-head face plays a crucial role in the success of tunnelling projects in soft ground. The amount of published literature on this subject is very limited, however; as a result, tunnel-boring machine (TBM) manufacturers have developed different cutter-heads for soft ground, with varied opening distribution based on their experience. In this paper, as a first step, the results of field studies on cutter-heads’ opening design for soft ground are expressed. The paper then mainly focuses on numerical studies using the discrete-element method (DEM) to evaluate the adaptability of the EPB system and cohesive and non-cohesive soils’ fluidity by changing the opening distribution on the cutter-head. Finally, the optimum opening ratio and its distribution for different soils – by considering the important parameters of the value of the thrust force, cutter-head torque and soil fluidity condition – are proposed based on the analysis results from DEM. Furthermore, the flow characteristics of soil particles inside the EPB chamber are obtained through examination of the velocity field. In addition, practical aspects for further application in the TBM industry are discussed through the consideration of field studies and a real example.