Abstract

The failure of a slope could either be an unacceptable serviceability condition or in the extreme, collapse. When complete collapse occurs the result may be damage to property, injury or death and adverse effects on a variety of resources. Transport infrastructure is at risk when it is constructed on slopes that are potentially unstable. For example, roadways can be affected after a landslide event.

Many of the engineering design solutions to restrict movements, or in extreme cases prevent complete collapse, reflect geotechnical uncertainties and hence monitoring is essential. The information obtained from monitoring slopes provides a means of understanding potential slope movements, both in relation to the mechanism involved and the effectiveness of any slope stabilisation measures. Although a wide range of techniques exist for monitoring slopes, the task is sometimes complicated by the scale of potentially unstable ground, the location and the unpredictability of when movements may occur.

This research aims to examine the applicability of a Brillouin optical time-domain reflectometry (BOTDR) sensor monitoring system in monitoring ground movements along highway slopes. A unique advantage of this technology is the ability to measure the strain along the full length of an optical fibre cable, up to 10 km, i.e. to give distributed readings. From measurements of this form (i.e. continuous movement profiles) possible precursors of movements can be identified.

The challenge of this research was to investigate the best way of installing the optical fibre to the slope so that effective monitoring can be achieved.