Cutterhead and Cutting Tools Configurations in Coarse Grain Soils

Many subway/metro tunnels were constructed using close face shield machines in coarse grain soils in last decades. Configurations of the shield cutterhead and cutting tools are critical in terms of cost and project duration. There are currently no recognized methodologies available for the configurations due to the various geological and technical influencing factors. Several aspects have been considered in many single case studies.

To aid a better understanding for the involved design and operational aspects in a system way, main physical and mechanical characteristics of the coarse grain soils encountered in China are briefly summarized; advantages and disadvantages of the spoke type and plate type cutterhead equipped with corresponding cutting tools are outlined; performances of the different shield cutterheads used in the typical subway construction cases are introduced.

Based on the jobsite experiences, discussed are the options with respect to design of the cutterhead and cutting tools in the coarse grain soils, including opening ratio of the cutterhead, configuration of the cutting tools, use of the single disc cutters with inserts, reasonable movement of shield machine, robust shield machines against wears and interventions for changing tools.

According to the discussions, the rule-of-thumb suggestions are presented to provide references for later similar projects.