Study on the Rock Fall Detection System using Steel Wire Cable Sensor and Satellite Phone-Experimental Results on the Applicability for a Cropped Slope-

Abstract

Results of geo-engineering monitoring by Monma et al. at Amatori-hashi, West Area, Wakayama, Japan, have shown that the frequency of various scale rock falls tends to increase just before a big rock fall or a slope failure. This phenomenon has been also observed just before 2nd slope failure following the 1st failure in 1997 at No.2 Shiraito Tunnel, Hokkaido, Japan. The authors propose the frequency monitoring of small rock falls as a useful way to predict large-scale rock falls or slope failures. In this study, practical applicability of rock fall detection system using steel wire cable sensor and satellite phone was carried out. From this field study the following points were made clear:1) the proposed system is able to transmit the measured rock fall signals to a remote office. The rock fall frequency and the rock fall source could be evaluated, even when the steel wire cable sensor was stretched on the cropped slope having no net, which made easy the propagation of the rock fall impact. 2) It was confirmed that rock fall characteristics, such as the falling velocity, could be evaluated through analysis of the data registered by the field side personal computer. 3) As a result of composition study of measured waveforms, it was concluded that stretching interval of steel wire cable sensors could be increased up to 10m without deterioration of the system rock fall detection abilities.