With the objective of reinforcing safety when working on slopes, First Balfour Sr. Geotechnical Engineer Dr. Erwin T. Calo, in cooperation with the Energy Development Corporation (EDC), established the first sensor-based landslide warning system in engineering practice in the Philippines.
First Balfour started to implement the system in all identified geohazard sites at the EDC Leyte Geothermal Business Unit (LGBU) last year. This was done by installing Geohazard Early Detection Instruments (GEDI) along the slopes prior to the commencement of any investigation or construction work. The current GEDI set-up is composed of rain gauges, moisture sensors, and tiltmeters.
Landslides that happen in geothermal sites are mostly induced by rainfall. As rainwater infiltrates the soil and slowly drains away from the soil mass, the saturation of soil reduces the stability of the slope thus leading to a landslide. To have a good understanding of the behavior of the soil along a slope during various rainfall occurrences, a rain gauge and moisture sensors are installed. A rain gauge measures the rainfall amount while a moisture sensor, embedded at various depths which range from 0.5 to 2.50 meters, determines the water content of the soil. The reading from the rain gauge gives a clear picture of the site-specific rainfall while the reading from the moisture sensor gives an indicative change in the degree of saturation of the soil mass. Such instruments can give a good measure if any work needs to be stopped when there is an indication of a full saturation of the slope. As landslides most likely happen during heavy rainfall, tiltmeters are installed to monitor any slope movement. A tilting threshold value is set and the alarm system is programmed to activate when the tilt value is more than the threshold limit.
GEDI sensors are connected to a data logger that collects information from the instruments every ten minutes. The slope monitoring engineer gathers the data at pre-set times within the day and the GEDI output is processed and forwarded to Dr. Calo for further analyses. GEDI sensors are continuously monitored from the investigation until the completion of construction work on a specific slope.
This scientific advancement in engineering practice attests to both First Balfour and EDC’s aim towards improving its safety protocols. The landslide early warning system is a solid affirmation the companies’ commitment towards safety and the protection of human life and property.