Geotechnical analysis of a landslide in Nakorn Si Thammarat province, Southern Thailand

For decades, landslides have occurred in Nakorn Si Thammarat province, southern Thailand. The landslides have caused damage to properties and claimed human lives. The most recent and well-documented landslide took place in March 2011, where 4-days continuous heavy rainfall triggered the landslide. A finite element model was developed for landslide analysis. Seepage simulation and slope stability analysis were conducted to assess the failure mechanism of the landslide. Transient simulation results show that the soil converts from dry to wet as its pore water pressure increases due to the seeping water resulting in reduction of soil shear strength. Computed factor of safety decreases from 2.1 to 0.95 and landslide is triggered within 108 hours of rainfall with a cumulative rainfall exceeding 597.5 mm. Time of the landslide computed is practically similar to the time of landslide evidenced by local people.