A model of crack growth in microcracked rock

This paper considers microcrack-governed crack propagation and proposes a model for large-scale crack growth. The consecutive fracturing of volume elements at the crack front enables the crack to propagate and makes it effectively thick. The volume element size is determined from the competition between two effects: (a) reduction of the stress concentration at the crack front due to increase of the crack thickness, and (b) reduction of the volume element strength due to increase of its size or, in other words, the internal scale effect governed by distribution of the microcracks within the volume element. It is shown that the large-scale (macroscopic) fracture toughness may be assessed from laboratory measurements of the tensile strength scale effect. (A) This paper was presented at the 34th U.S. Symposium on rock mechanics, 27-30 June 1993, University of Wisconsin-Madison. For the covering abstract see IRRD 863389.

[1]  J. D. Embury,et al.  A Treatment of Inelastic Deformation Around a Crack Tip due to Microcracking , 1980 .

[2]  H. Horii,et al.  Analytical modeling of microcracking and bridging in the fracture of quasi-brittle materials , 1992 .

[3]  A. Evans,et al.  Some effects of microcracks on the mechanical properties of brittle solids—II. Microcrack toughening , 1985 .

[4]  G. Sih,et al.  Mathematical theories of brittle fracture. , 1968 .

[5]  J. Shlyapobersky,et al.  Energy Analysis Of Hydraulic Fracturing , 1985 .

[6]  Bhushan Lal Karihaloo,et al.  Modelling of tension softening in quasi-brittle materials by an array of circular holes with edge cracks , 1991 .

[7]  Michael Ortiz,et al.  Microcrack coalescence and macroscopic crack growth initiation in brittle solids , 1988 .

[8]  Joseph F Labuz,et al.  The fracture process zone in granite: evidence and effect , 1987 .

[9]  V. P. Tamuzh,et al.  Propagation of a main crack in a body with distributed microcracks , 1984 .

[10]  V. V. Novozhilov,et al.  On a necessary and sufficient criterion for brittle strength: PMM vol. 33, n≗2, 1969, pp. 212–222 , 1969 .

[11]  D. S. Dugdale.  Yielding of steel sheets containing slits , 1960 .

[12]  A. Chudnovsky,et al.  Evaluation of energy release rate in the crack-microcrack interaction problem , 1992 .

[13]  M. Ortiz,et al.  Mixed mode crack-tip fields in monolithic ceramics , 1990 .

[14]  K. Trustrum,et al.  Statistical approach to brittle fracture , 1977 .

[15]  Z. Bažant.  Mechanics of Distributed Cracking , 1986 .

[16]  Gao Huajian.  Fracture analysis of nonhomogeneous materials via a moduli-perturbation approach , 1991 .

[17]  M. Kachanov,et al.  Mechanics of crack—microcrack interactions , 1990 .

[18]  G. I. Barenblatt.  THE MATHEMATICAL THEORY OF EQUILIBRIUM CRACKS IN BRITTLE FRACTURE , 1962 .

[19]  H. Rossmanith.  Modelling of fracture process zones and singularity dominated zones , 1983 .

[20]  John W. Hutchinson,et al.  Crack tip shielding by micro-cracking in brittle solids , 1987 .