Abstract of the proposal

Landslides in slopes of weathered igneous rock in Hong Kong are usually triggered by pore pressure increase induced by heavy rainfall. Understanding the characteristics of pressure response to rainfall is essential for slope stability study. Observations of piezometric response to rainfall in slopes very often show somewhat abnormal features. Piezometers installed in different locations of a slope may indicate distinctly different response to rainfall: some shows quick and sharp response to rainfall, but some show sluggish and delay response. Sometimes a piezometer in the deep rock shows a quicker response than that in the shallow soil. Very often the piezometers do not indicate a unified hydraulic head distribution in a slope. Such puzzling pore pressure features are difficult to understand based on the conventional conceptual model widely used by local engineers that assumes that the saprolite is an aquifer while the bedrock is considered as an impermeable boundary.

The Principal Investigator has demonstrated that there may be a relatively more permeable zone around the rockhead due to well-developed fracture network. Groundwater in this zone may become significantly confined after heavy rainfall. Such a high permeability zone can result in complicated unsaturated and saturated flow in the slopes in response to rainfall. The aim of this project is to investigate various abnormal piezometric responses to rainfall by considering complicated unsaturated and saturated flow in igneous slopes with a high permeability zone at the rockhead. The proposed study will provide a better understanding about the piezometric behavior of pore pressure in slopes and insights on slope stability evaluation.

Related Publications (not yet available):