Design of cutterhead layout pattern for rock head micro-TBMs

This paper presents the details of the cutterhead lace design for the rock head micro-TBMs considering structural elements’ geometric constraints. These constraints include the dimensions of the cutter boxes in various areas of the cutterhead (center, face, and gage regions) and the buckets and pedestal arms attached to the backside of the cutterhead. The very limited available space in micro-TBMs prevents the designer to produce an optimal design with no boundary conflicts among the structural elements. In this regard, the formulas to calculate the overlap between cutter boxes and the pedestal arms/bucket areas are developed. In addition, the process of setting an optimized layout design with random or random-paired patterns is explained when a permissible overlap is accepted in the design. The results show that the method explained in this paper can be very easily coded with computer programs to produce many alternative design patterns with uniformly and symmetrically distributed cutters and buckets. These alternatives are produced with the use of random sampling, and the results have no boundary overlap for the cutter boxes and minimum overlap between the cutter boxes and the pedestal arms’ areas (below a permissible overlap area defined by the user). While the geometric constraints limit the lace design to be so restricted and unoptimized, the introduction of the permissible overlap concept allows the project engineers to produce several alternative designs for the subsequent comparison and analysis.