EXPERIMENTAL ANALYSIS OF CRACK PROPAGATION IN GRANITE

An experimental approach is used to demonstrate the concept of an effective crack length with double-edge-notched specimens of charcoal and rockville granite. Crack propagation in rock is characterized by microcracking around the crack tip and interlocking along a portion of the crack; this region is called the fracture process zone, and together with the traction free length defines the effective crack length. Twenty closed-loop, strain-controlled fracture tests were conducted on charcoal and rockville granite. Crack growth was monitored with a travelling optical microscope (100 x magnification). By comparing the post-peak behaviour of both granites, it is suggested that the process zone is larger for the larger grain-sized rock (rockville). Conventional linear elastic fracture mechanics techniques are used to calculate the apparent fracture toughness of charcoal granite at various crack lengths. In addition, a j-integral expression is derived for the double-edged-notched geometry in terms of the area under the load-displacement record. The shortcomings of both analyses are discussed. An attempt is made to explain the inadequacies by including the process zone in the calculations of the fracture toughness. (Author/TRRL)

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  • Corporate Authors:

    Pergamon Press, Incorporated

    Headington Hill Hall
    Oxford OX30BW,    
  • Authors:
    • Labuz, J F
    • Shah, S P
    • Dowding, C H
  • Publication Date: 1985-4

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  • Accession Number: 00396932
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Aug 25 2004 2:39AM