Acoustic Emission Associated with the Formation of Sets of Fractures in a Sandstone

A laboratory ployaxial loading system has been employed to study acoustic emission (AE) associated with the failure of a sandstone specimen. The minor principal stress is maintained at a low level, while the two other principal stresses are raised until failure takes place. The AE events associated with the formation of micro-cracks, and resulting through-going fractures, are located precisely by an array of AE sensors in each of the loading platens. The mechanisms indicate tensile failure during initial fracture failure, but shear failure as the fractures approache the platens.