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Landslides

, Volume 7, Issue 3, pp 219–236 | Cite as

An integrated model simulating the initiation and motion of earthquake and rain induced rapid landslides and its application to the 2006 Leyte landslide

  • Kyoji SassaEmail author
  • Osamu Nagai
  • Renato Solidum
  • Yoichi Yamazaki
  • Hidemasa Ohta
Original Paper

Abstract

A gigantic rapid landslide claiming over 1,000 fatalities was triggered by rainfalls and a small nearby earthquake in the Leyte Island, Philippines in 2006. The disaster presented the necessity of a new modeling technology for disaster risk preparedness which simulates initiation and motion. This paper presents a new computer simulation integrating the initiation process triggered by rainfalls and/or earthquakes and the development process to a rapid motion due to strength reduction and the entrainment of deposits in the runout path. This simulation model LS-RAPID was developed from the geotechnical model for the motion of landslides (Sassa 1988) and its improved simulation model (Sassa et al. 2004b) and new knowledge obtained from a new dynamic loading ring shear apparatus (Sassa et al. 2004a). The examination of performance of each process in a simple imaginary slope addressed that the simulation model well simulated the process of progressive failure, and development to a rapid landslide. The initiation process was compared to conventional limit equilibrium stability analyses by changing pore pressure ratio. The simulation model started to move in a smaller pore pressure ratio than the limit equilibrium stability analyses because of progressive failure. However, when a larger shear deformation is set as the threshold for the start of strength reduction, the onset of landslide motion by the simulation agrees with the cases where the factor of safety estimated by the limit equilibrium stability analyses equals to a unity. The field investigation and the undrained dynamic loading ring shear tests on the 2006 Leyte landslide suggested that this landslide was triggered by the combined effect of pore water pressure due to rains and a very small earthquake. The application of this simulation model could well reproduce the initiation and the rapid long runout motion of the Leyte landslide.

Keywords

Leyte landslides Computer simulation Rapid landslides Ring shear test 

Notes

Acknowledgement

This research is a technical development activity for the computer simulation within the project titled as “Early Warning of Landslides”, one of projects of the International Program on Landslides (IPL) jointly managed by ICL, UNESCO, WMO, FAO, UNISDR, ICSU and WFEO. The project was financially supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) in the frame work of International Joint Research Promotion Fund. The project (leader: K. Sassa) was jointly conducted by the International Consortium on Landslides (ICL) and the Disaster Prevention Research Institute (DPRI) of Kyoto University, the China Geological Survey, the Korean Institute of Geosience and Mineral Resources (KIGAM) and the National Institute for Disaster Prevention (NIDP) in Korea, University of Gadjah Mada (UGM) and the Bandung Institute of Technology (ITB) of Indonesia, Philippine Institute of Volcanology and Seismology (PHIVOLCS). The part of Leyte landslide investigation was conducted together with Assoc. Prof. Hiroshi Fukuoka, Prof. Hideaki Marui, Assoc Prof. Fawu Wang and Dr Wang Gonghui.

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Kyoji Sassa
    • 1
    Email author
  • Osamu Nagai
    • 1
  • Renato Solidum
    • 2
  • Yoichi Yamazaki
    • 3
  • Hidemasa Ohta
    • 4
  1. 1.International Consortium on LandslidesKyotoJapan
  2. 2.Philippine Institute of Volcanology and Seismology (PHIVOLCS)Quezon CityPhilippines
  3. 3.GODAI Development CorporationKanazawaJapan
  4. 4.Ohta Geo-Research Co., Ltd.NishinomiyaJapan

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