Monitoring a landslide recovery operation
Author: David Fernandez Bruna & Michelle Zeller
The benefit of combining technologies; the detection speed of radar and the reliability of interpretation of movements via measurements from total stations.
On 6 February 2020 at a landfill in Zaldibar, northern Spain, thousands of cubic metres of waste collapsed. Tragically, the collapse killed two employees of the refuse company responsible for the site. The landslide spread beyond the landfill and onto a highway, the busy AP-8 which runs from east to west across Basque Country. Interbiak, the public company in charge of managing the highway, immediately instructed engineering partner InfoTOP to set up a system to monitor the collapsed material. InfoTOP installed a Leica Geosystems automated monitoring system configured to alert the engineers – and via them, the rescue team and emergency services – of any further movement or instability.
Increasing safety for those stabilising the landslide
The landslide dragged thousands of cubic meters of material – some toxic and flammable - from the landfill which occupied an area 30 metres wide and about four metres high. Emergency services needed to quickly control the stability of the slopes in order to begin rescue operations. Working in a precarious and unstable situation, they needed an alert system to warn them should the waste material move again.
It was a challenging installation. Because of the site's hazards, InfoTOP's monitoring system needed to be entirely remote, without any manual measurement. It could only be installed within 400 – 800 metres of the landslide, and more crucially, had to run 24/7 without any operators. In terms of speed, the data collected by the system needed to be processed automatically, with reports generated and sent to InfoTOP's geology partner Ingek for interpretation. For coordination with the distributed team, data had to be accessible from anywhere. Finally, the monitoring system needed to be configured to send alerts to the technicians in real-time by SMS and email.
Two monitoring systems for a complete picture
Faced with these conditions, InfoTOP set up an automated monitoring solution combining total stations with radar. They installed two Leica Nova TS60 total stations with mobile communications provided by a Leica ComGate10 router with 4G technology via a virtual private network (VPN). The total stations performed measurements using a series of more than 100 prisms installed in the area. Installed on concrete pillars, one total station was positioned next to the radar and the second one in an area near the landfill – to measure the prisms that were not visible from the first station. Measurements were then managed by Leica GeoMoS software installed on a virtual cloud infrastructure.
In addition, an IDS HYDRA-G – remote sensing monitoring system based on radar technology – was installed to give a continuous measurement sweep. With 120 degrees of coverage horizontally and 30 degrees vertically, this covered most of the danger zone, except for areas hidden by vegetation. Designed for early warning and real-time measurements of sub-millimetric displacements in cut-slopes, the HYDRA-G provided real-time data of movements, transmitted to the IDS Guardian software for interpretation and alarm management.
Why were both systems combined? Speed, reliability and depth of data
The radar system allowed movements to be identified across hectares in seconds by comparing consecutive measurements through interferometry (the interference of waves) over a large distance range, detecting movements of ±0.1mm at up to 800m. While highly sensitive, it can only monitor within its line of sight. Not all areas of the landslide allowed radar measurement due to its inclination and parts being hidden by vegetation. Therefore, multiple total stations covered any blind spots and measured prisms in both the radar coverage and shadowed areas. The prism data helped the engineers and geologists understand each area's true movement, building an exact picture of the 3D movements taking place. These highly complementary technologies provided a combination of speed from radar detection with reliable spatial information on the movements via total station measurements. Leica Geosystems and IDS GeoRadar technology and software form Hexagon Geosystems’ monitoring solution.
Connectivity and instant alerts
The Leica GeoMoS and IDS Guardian data processing software allowed InfoTOP to automate the system so that the data could be instantly and remotely shared with specialists at Ingek for interpretation. GeoMoS Now! is an easy to use web interface that made it possible for the geologists to analyse the situation from any location, 24/7. The system was also configured with a series of real-time alerts that sent warnings immediately if the configured thresholds were exceeded.
Safety in the immediate aftermath and throughout the phased disaster recovery process
Talking about the monitoring system, Oskar Moral from InfoTOP said, "It allows us to have an early warning if any movement happens, to ensure the safety of the staff as well as to have control of the stability. A great advantage is that everything is automated without the need for operator intervention to control the equipment day-to-day; this has allowed us to obtain immediate results without further processing. We have not found another solution that matches the advantages offered by the Hexagon Geosystems’ monitoring system."
"Furthermore, it is a scalable system that allows us to manage the sensors as this difficult project evolves continually."
Interested in monitoring? Please feel free to read further case studies, showing how our customers use our solution to improve their monitoring workflow: