Crack Growth in Rocks with Pre-existing Flaws Subjected to Uniaxial and Biaxial Compression

Abstract

Rock mass encountered in the field is rarely free from joints or fractures. The presence of a discontinuity in rock seriously influences its strength and deformation behavior and in turn complicates the design of rock structures like rock slopes, tunnels, and caverns. As rock mass behavior and corresponding failure are directly linked with pre-existing small cracks/flaws, the corresponding study becomes of utmost importance. Cracks generally initiate at threshold stress level, propagate and coalesce with other cracks to form a macrocrack, and lead to eventual failure. Many studies were carried out to understand the behavior of crack growth due to pre-existing persistent discontinuities like a flaw and fracture where failure is mostly governed by the translational movement between the flaw surfaces. In the case of the non-persistent flaw, new cracks usually develop from the flaw tip which mostly governs the material failure and its pattern. The flaws present in rock mass generally exhibit both open and narrow flaw configurations in the field. In the present paper, the crack growth behavior of narrow flaws subjected to uniaxial and biaxial compression is investigated with laboratory and numerical experiments. The study mainly focused on numerical analysis of crack growth in rocks with pre-existing flaws using finite element software “ABAQUS”. The behavior of discontinuity is modeled by adopting a Cohesive Zone Model (CZM) using the Extended Finite Element Method (XFEM) and subsequently verified with laboratory experiments. The failure pattern and crack types and corresponding growth observed for a single and double flaw angle arrangement are investigated, and crack stress observed is discussed.KeywordsNarrow flawFlaw angleCrack growthCZMXFEM