Fracture-induced Physical Phenomena and Memory Effects in Rocks: A Review.

Fracture-induced physical phenomena allow a real-time monitoring of damage evolution in rocks induced by mechanical loading. Some of these phenomena, e.g. plastic deformation, changes in permeability and electric resistivity, provide an overall estimate of damage as a function of stress. Others, such as acoustic emission or electromagnetic emission, allow an exact location of cracks in space and time. Being nondestructive, monitoring techniques based on fracture-induced physical phenomena, are a basis for prediction of earthquakes and rockbursts in underground mines. They are also crucial for a fundamental understanding of rock fracture mechanisms and for developing constitutive models of rock behaviour. Memory effects take place in rocks subjected to cyclic loading with the peak stress (strain) value increasing from cycle to cycle. The effects are represented by certain characteristic changes in rock properties and parameters that are observed when the stress (strain) reaches its previous peak value. Potential applications of memory effects range from stress measurement techniques to earthquake prediction to damage surface scanning. Essential experimental and theoretical results on fracture-induced physical phenomena and memory effects in rocks are considered in the article. Possible applications as well as not-yet-clear points are discussed. [ABSTRACT FROM AUTHOR]