Size effects, process zone and tension softening behavior in fracture of geomaterials

Abstract

In this paper we review experimental and field observations of the process zone, K Ic size dependence in concrete and rock and suggest that a valid K Ic test for such materials may require impractically large specimen sizes. Direct application of linear elastic fracture mechanics (LEFM) to toughness testing of quasi-brittle geomaterials has not been consistently successful. An alternative material property the tension softening curve is better suited to characterize crack formation and growth in geomaterials, and can be determined in the laboratory with reasonable specimen sizes. An experimental technique, originally developed for concrete, can be used to determine the tension-softening curves of rocks.