Angular dependence of rock cutting forces due to foliation

A series of rock cutting tests was conducted with three different metamorphic rock types. Samples were prepared with alpha angles of 0°, 45° and 90° to investigate the influence of foliation angle on the rolling forces (FR,scaled) of a mini disc cutter (scale 1:8). Results show that FR,scaled increased by a factor of about 2 at an alpha angle of 0° compared to 90° for all three rock types. In a subsequent step, a way to implement the results into a TBM performance prediction model to derive a correction factor for angular dependence of TBM performance was shown. The resulting correction factor for overall TBM performance (FN0°/FN90°) is in the range of 1.33-1.80 which is in good agreement with previously published TBM field data by Büchi (1984) and Thuro (2002).