Post on 11-Apr-2022
3rd JSPS-DOST International Symposium on Environmental Engineering
Geotechnical Hazards and Geotechnical Hazards and Disaster Mitigation TechnologiesDisaster Mitigation Technologies
J. Kuwano, M. Warakorn, M. Zarco and M. Adajar
Natural hazard is unexpected or uncontrollable natural event of unusual magnitude that threatens the activities of people or people themselves (Orense, 2003)
Geotechnical hazards are natural events which directly affect the ground or caused ground movements.
- Earthquakes and earthquake related hazards like soil liquifaction, lateralspreading and tsunami
- Landslides or slope failuresOrense, RP (2003) “Geotechnical Hazards-nature, assessment and mitigation”
Human activities can increase the occurrence and severity of geotechnical hazard
- building on top of unstable slope will increase the possibility of slope collapsing.
- steepened slopes due to cutting into a hillside or embankment may initiate landslides
- too much logging operations
EM-DAT Emergency Disasters Database www.em-dat.net
Earthquake related hazards
The 1983 Nihon-kai chubu Earthquake
Roads in Wakami town in Akita Prefecture was totally destroyed
The 1983 Nihon-kai chubu Earthquake
Sand volcano appeared as evidence of soil liquefaction
1995 Hyogo-ken Nanbu (Kobe) Earthquake
Damage on the building is concentrated at a particular story due to building’s vertical irregularities
1995 Hyogo-ken Nanbu (Kobe) Earthquake
The 18-span bridge of Kobe Line in the Hanshin Metropolitan Expressway
The 2004 Chuetsu Earthquake
Derailed Japanese bullet train (Shinkansen)
The 2004 Chuetsu Earthquake
Lifted manhole at Nagaoka City as a result of soil liquefaction
The 1990 Luzon Earthquake
Before the earthquake
After the earthquake
The 12-storey section of Hyatt Hotel collapsed over the lobby
The 1990 Luzon Earthquake
Building in Dagupan City sink by as much as 1 meter
The 2004 Indian Ocean Earthquake (Asian Tsunami)
The aftermath of tsunami disaster in Thailand
Landslides related hazards in the Philippines
The Cherry Hills Landslides
The Cherry Hills Subdivision in Antipolo City. Photo by Punongbayan (1999).
The Panaon Island Landslides
The landslides on the left buried the village in Punta, San Franscisco, Panaon Island, Southern Leyte killing hundreds of people Photo by the Philippine Star (2003)
The Quezon Landslides
Numerous landslides on forested areas and flooded areas along Gumian River, Quezon Province
The Mayana, Jagna Lanslide
The source area of the Mayana landslide in Bohol Island
The Guinsaugon Landslide
The catastrophic rock-slide avalanche buried the entire village of Guinsaugon in St. Bernard Southern Leyte
Mitigation Techniques
Mitigation measures that can be adopted to reduce risk :
• Risk evaluation and risk communication
- preparation of zoning map
• Risk monitoring to provide timely warnings through media such as TV and radio broadcasting
Liquefaction hazard mitigation techniques :
• Soil improvement and densification -sand compaction pile, vibroflotation, dynamic compaction, compaction grouting
• Increase the drainage ability of the soil
• Ground deformation control - sheet pile wall, soil cement column wall
Studies on mitigation techniques on soil liquefaction:
• Dungca, J.R. (2006) Effects of laterally spreading liquefied ground on single and double piles.
• Honda, T. et.al (2005) Mitigation techniques of damages of quay wall due seismic liquefaction
Slope protection and stabilization techniques
CONTROL WORKS:
• Soil removal or unloading - removing materials from the upper part of the slope, removing loose and unstable materials to reduce the driving force on the slope and to balance the failure.
• Benching - is the practice of transforming one high slope into a series of lower slopes with horizontal surfaces in between slopes.
Benching of slopes in Tongonan, Leyte
• Installing proper drainage
Slope stabilization using sub-horizontal drains
• Slope protection – use of grouted riprap, gabion walls, mortar spraying, and vegetation
Rounded, cobble and boulder-sized rocks are used as rip-rap wall for slope protection of roads.
Application of gabion walls in the Philippines
Mature vetiver grass in road projects
The Vetiver grass and its excavated roots
PREVENTION WORKS :
• Soil nailing and rock anchoring
Soil nailing and rock bolting used in construction of the buildings
• Rockfall barriers and rockslide shelters
Rockslide shelter and barrier along the highway leading to Baguio City, Philippines
Thank you !