A custom acoustic emission monitoring system for harsh environments: application to freezing-induced damage in alpine rock-walls

Abstract

We present a custom acoustic emission (AE) monitoring system designed to performlong-term measurements on high-alpine rock-walls. AE monitoring is a common tech-nique for characterizing damage evolution in solid materials. The system is based ona two-channel AE sensor node (AE-node) integrated into a Wireless Sensor Network (WSN) customized for operation in harsh environments. This wireless architecture of-fers flexibility in the deployment of AE-nodes at any position of the rock-wall that needsto be monitored, within a range of a few hundred meters from a core station connectedto the internet. The system achieves near real-time data delivery and allows the user toremotely control the AE detection threshold. In order to protect AE sensors and capture acoustic signals from specific depths of the rock-wall, a special casing was developed.The monitoring system is completed by two probes that measure rock temperatureand liquid water content, both probes being also integrated into the WSN. We report afirst deployment of the monitoring system on a rock-wall at Jungfraujoch, 3500 ma.s.l.,Switzerland. While this first deployment of the monitoring system aims to support fundamental research on processes that damage rock under cold climate, the systemcould serve a number of other applications, including rock-fall hazard surveillance orstructural monitoring of concrete structures.