The acoustic emission (AE) technique has found wide application in rock
engineering. Generally, acoustic emission, which is produced by a rapid
microcrack growth, is an ubiquitous phenomenon associated with brittle
fractures and can provide information on the failure process in rocks. The
sudden release of stored energy in the form of an elastic stress wave that
travels from the point of origin within the material to a boundary is called
an AE signal or a discrete AE event. Based on a number of experiments and analysis, the correlations
among the rock type, the complete stress-strain behaviour, mode of failure
and AE properties are investigated and the AE pattern has been classified
as four types: single-peak AE, double-peak AE, continuous AE and absent
AE. Each type of AE pattern corresponds to a certain type of rock and is
largely related to the internal structure and imperfection of a rock.
Applications of the AE technique in stability monitoring, in situ stress
assessment and seismic source location are also discussed.