Development of Testing Method for Performance of TBM Disc Cutters in Circular Rock Cutting

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TBM disc cutters can be clustered into two groups depending on their locations mounted on the cutter head of a TBM ; ones are face cutters and others are gauge cutters. A rock cutting rig which has been installed in the present investigation allows us to test the performance of both types of disc cutters. In addition, the rig facilitates rock cutting along circular tracks as well as conventional linear cutting. Laboratory experiments using a circular rock cutting rig are promising for predicting the performance of TBMs and raise bore machines since these machines work in circular cutting mode. A dynamometer which is dedicated to the test rig allows us to detect not only the three perpendicular components of tool force, but the twist around the thrust.The experiment using a TBM gauge cutter provided newly empitical formulae by which we can predict thrust and torque needed to a given penetration of a gauge cutter. The formulae suggest that a gauge cutter with a plunge angle of alpha from the machine thrust should be equivalent to a face cutter with an additional edge angle of 2alpha, as far as tool force is concerned. Accordingly the formulae give a rational explanation for gauge cutters being subject to more harmful resistance than face cutters. Further investigations were carried out to explore the counter measures to reduce the resistance exerted on gauge cutters and to prolong their life-spans. The experimental results showed that the tool force for a gauge cutter could remain as low as for a face cutter whenever the normal of excanvated rock surface has an inclination being close to the plunge angle alpha of a guage cutter.