Macro and micro behaviour of soil fracturing

Abstract

Soil fracturing due to fluid injection involves various macro- and micro-mechanisms. Soil fracturing tests were performed on clay and sand. Different fluids (water, epoxy and cement-bentonite) were injected in both normally consolidated and overconsolidated kaolin clay specimens, which all showed fractures. A distinct single fracture was observed for all overconsolidated clay specimens due to tensile fracture. For normally consolidated clay specimens, the fracture pattern is further dependent on the rheology of injection fluid. Multiple fractures resulted when high viscous epoxy and low water-cement ratio grouts were injected. When low viscous liquids and high water-cement ratio grouts were injected, a distinct single fracture was observed. Micro-behaviour related to plastic instability around the injection point has been suggested as a possible mechanism of fracturing in normally consolidated plastic clays. Results from injections tests of cement-bentonite grout into sand indicated that the magnitude of confining pressure and grout rheology have profound effects on the development of fingering-like fractures in sand. © 2006 Taylor & Francis Group.