Design of a measurement assembly to study in situ rock damage driven by freezing

Abstract

We describe the design of an acoustic emission (AE) measurement assembly for reliable acquisition of a multi-year time- series in steep alpine rock-walls. The motivation for collection of these data is to enhance understanding of freezing- induced rock damage. Because measurements in natural rock slopes are challenging, this study investigates technical options suitable to capture AE signals from differing depths while incurring minimal signal loss between the rock and the sensor. We first outline the requirements for the measurement assembly and present two generic solutions to be evaluated and refined. We then present candidate materials for building components of the assembly and experimentally estimate their attenuation coefficients and signal loss at the rock-sensor contacts. Based on these results, we present the final design chosen for the measurement assembly and briefly report initial experiences from a field deployment site at 3500 m a.s.l. at Jungfraujoch, Switzerland.