Cutter force measurement on tunnel boring machines – System design

Loading of a TBM disc cutter is usually derived by dividing the total thrust by the number of cutters which gives an approximate average loading of 250 kN for a typical 17″ cutter. However, laboratory cutting tests infer that the loading of a cutter oscillates strongly and can reach peaks that are a multiple of the average forces. Knowledge of the true forces acting on a disc cutter is of great importance to gain further insight in areas such as cutter wear, brittle fracture of cutter rings, fatigue and the mechanism of rock breakage in different geological formations.Consequently, the development of a measurement method to determine the three-dimensional loading situation of a disc cutter in real-time was conducted. An investigation of the deformation state of a typical disc cutter and its casing was performed by means of the finite element method. Subsequently, a measurement method that isn’t affected by cutter change was developed by finding suitable spots for sensor placement in the cutter saddle. Laboratory tests proved the feasibility of the developed measurement method that is now ready for implementation on a TBM.

► A new method for measuring TBM cutting forces has been developed.
► Sensors are placed inside the cutter saddle which ensures that cutter change is not affected.
► Acquisition and interpretation of cutting forces will improve the development of TBM tunneling.