Rapid Identification of Hazardous Loose Coarse Landslide Soil Deposits on Steep Terrain (RGC GRF, PI: Zhang, L.M.; Co-I: Prof. Prof. Del G. Fredlund; Research students: Miss HF Zhao)

The primary objectives of the proposed research are to investigate the mechanisms of rain-induced failures of loose, coarse-grained soil deposits in the Wenchuan earthquake zone and to develop a strategy to rapidly identify numerous hazardous soil deposits on the hilly terrains. Preliminary field investigations indicate that the soil deposits are generally loose, coarse granular materials containing various coarse contents. Boulders larger than 200 mm are also frequently observed in the soil deposits. It is not fully understood how rainwater infiltrates into such coarse soils and how the shear strength of these soils decreases during rainfall infiltration. Also it is not clear how boulders affect water infiltration and groundwater flows into the soil deposits. To answer these questions, several challenging scientific issues need to be addressed on the soil-water characteristic curves, hydraulic conductivity, and shear strength of these coarse soils. These issues need to be addressed through extensive laboratory tests and numerical analyses. Based on the results obtained, a practical tool will be developed to rapidly identify hazardous soil deposits. Possible methods to improve the stability of such soil deposits will be explored. The outcome of the research will advance our engineering understanding of the fundamental behaviour of loose coarse soils. The results will also facilitate landslide hazards mitigation in Hong Kong, mainland China, and other places facing similar problems.