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 degrees, 45 degrees and 90 degrees to investigate the influence of foliation angle on the rolling forces (F-R,F-scaled) of a mini disc cutter (scale 1:8). Results show that F-R,F-scaled increased by a factor of about 2 at an alpha angle of 0 degrees compared to 90 degrees 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 (F(N)0 degrees /F(N)90 degrees) is in the range of 1.33-1.80 which is in good agreement with previously published TBM field data by Bilchi (1984) and Thuro (2002).