Abstract
There are many operating and closed quarries of tuff in Ooya region Utsunomiya City, Japan. In March 1990, a rock-ceiling of the underground quarry suddenly sank and collapsed. It was confirmed that the field acoustic emission increased in number before the sinking, just like the pre-seismic activity of natural earthquakes.
Our definitions of the field acoustic emission include the acoustic emission by progressive cracks in rock mass, the concussion by rock splinter that is separated from ceiling or wall, and the vibration that is caused by buckling of the rock pillar.
We predicted the area and the time of the sinking by the results of observation and data analysis of the field acoustic emission.
The basic features of data analysis are as follows;
(1) To use the activity factor (amplitude multiplied by vibration duration time) which is effective to represent the microseismic activity more than the frequency.
(2) To construct database system including the each observed field acoustic emission data, the location data of observation point, and the topographical map of this region.
(3) To draw the microzonation map of sinking potential to estimate the sinking area by the calculated center and the scale of each observed field acoustic emission.
(4) To introduce the hyperbolic function to estimate the probability of sinking.
