Original paper(Vol.47 No.5 pp.489)

Study on evaluation of loosened area around rock cavern by in situ acoustic emission measurement

Hata Koji; Yoshioka Hisaya; Kinashi Hideo

Abstract:When constructing large underground caverns such as hydraulic power stations and oil storages, it is important to estimate the loosened area around rock caverns caused by excavation. If the loosened area around a rock cavern is known, the most suitable support members and quantities can be determined. The authors have carried out in situ experiment to investigate the crack growth into rock mass by acoustic emission (AE) measurement.
In this paper, parameter analysis, locational analysis and moment tensor analysis based on the observed AE signal waves were carried out to make clear the diffusing patterns, locations, orientations and crack types of AE sources. The following conclusions were obtained: (1) Many large amplitude AE signal waves diffused within about ten minutes after cavern blasting, (2) The concentrated areas of tensile cracks and shear cracks around a rock cavern were different, (3) From the distribution of observed AE signal waves, the loosened area was estimated within depth of 2m from the excavated wall.

Key Words:loosened area, rock mass, acoustic emission, moment tensor analysis, source location, amplitude distribution