30-08-2014, 04:43 PM
Introduction: disc cutter wear is defined as microscopic or macroscopic removal or fracture of material from the working surface of a tool or wearflat by mechanical means; in general any degradation that reduces cutter service life. Wear rate is measured as tool weight, volume or height loss per cut or rolled distance. Cutter service life is measured in cut or rolled distance. However, tool service life in cutting hours per tool is a more practical unit of measure. Classification of wear: Wear may be classified as • Normal wear • clogging bearing • fissures or breakage in the cutting ring • chipping • mushrooming • defective roller casing • lost or worn out clip • leaky disc cutter Operating limits of a TBM: As the demands by contractors and clients rise, the dimensions and power of tunnel boring machines increase rapidly. When optimising the rock fragmentation and increasing the performance of a TBM, some limits have to be considered. Figure shows an operating diagram where the penetration rate is plotted against the utilized thrust for different