Abstract
Pore water pressure fluctuations are observed in two landslide areas of pre-Tertiary or Paleogene rocks and one landslide area of Neogene rocks.
When the pore water pressure of various depth increases rapidly at the time of heavy rainfall, the landslide movement becomes active in the former two landslides. The pore water pressure fluctuation in the latter one has no relation to the landslide movement, because the measurement of pore water pressure is carried out in impermeable layers where the pore water pressure is not thought to fluctuate frequently. Pore water pressure fluctuation is proved to be an important cause of landslide movement.
The hydraulic water levels of various depth are often measured to be different. According to the groundwater prospecting test or the groundwater level measurement during a period of borehole excavation, impermeable layers make the hydraulic water levels of various depth different to each other. In case that impermeable layers exist in a landslide mass, based on hydro-geological surveys, pore water pressure on the slip surface should be measured for monitoring a landslide slope or designing prevention works.
