Landslide ALERT

Site plan showing the location of the ALERT station, ERT monitoring arrays (red lines), major geomorphologic features (white-dashed lines) and bedrock geology (black dashed lines). (© UKP/Getmapping Licence No. UKP2008/01).

BGS is currently researching the use of geoelectrical methods for landslide investigation. The overarching objective of the work is to develop a 4D landslide monitoring system that can characterise the subsurface structure of the landslide, and reveal the hydrogeological precursors to movement, thereby providing a means of predicting failure events.

A research site on an active landslide in North Yorkshire, UK (Figure 1) is being used for initial trials of this monitoring approach. The site is located in Lias Group bedrock, which is highly prone to landsliding.

An ALERT system was installed at the site during the spring of 2008. The system uses wireless telemetry to communicate with an office based PC, which runs control software and a database management system.

Modifications to the ALERT system at this site have included the addition of environmental and geotechnical sensors to monitor rainfall, ground movement and pore pressure changes within the landslide.

The system is housed in a weatherproof enclosure and is powered by batteries charged by a wind turbine and solar panels. ERT electrode arrays were permanently installed within a grid with dimensions of x = 38 m and y = 147.25 m.

Preliminary results and ongoing monitoring

Baseline 3D ERT model of the landslide generated from ALERT data

Strong resistivity contrasts between the slipped material and sandstone bedrock have provided a good basis for the use of ERT models to define the structure of the landslide (see Figure 2).

Self-potential (SP) signatures consistent with the movement of groundwater through the landslide are observed at the site, and have been used to identify seepage patterns across the study area.

Ongoing research is now focusing on the use time-lapse ERT and SP for monitoring hydrogeological changes in the body of the landslide, and the link between these changes and failure events.

Acknowledgements

We would like extend our sincerest gratitude to Steve and Josie Gibson (the landowners) for their involvement and cooperation in the research.

For further information please contact:

Dr Jonathan Chambers
Project leader
British Geological Survey
Tel: +44 (0)115 936 3428

class="bodyLink">Dr Jonathan Chambers