Report No. : GEO Report No. 98

Report Title : Preliminary Quantitative Risk Assessment of Earthquake-induced Landslides at Man-made Slopes in Hong Kong (2000), 69 p.

Author : H.N. Wong & K.K.S. Ho


In this pilot study, standard quantitative risk assessment (QRA) techniques involving the use of fault trees and event trees have been used to evaluate the risk of failures of engineered man-made slopes due to earthquake loading. The risk of failure of pre-1977 slopes which had not been checked or upgraded to current standards is outside the scope of this Report.

This preliminary study consists of a global risk assessment and integrates the past work carried out on seismicity of Hong Kong, including the assessment of critical acceleration, dynamic response characteristics of soils, earthquake-induced displacements of slopes, likelihood of different degrees of soil saturation at the time of an earthquake, margin of safety due to partial saturation, etc. In the QRA, due account is taken of the different landslide hazards as well as the probability and consequence of the different types of slope failures.

The results of the preliminary QRA have been compared with the risk of rain-induced landslides of pre-1977 man-made slopes. For soil cut slopes and fill slopes that comply with current geotechnical standards, the results suggest that the risk of earthquake-induced landslide fatalities in respect of such slopes is only a relatively small proportion of that posed by rain-induced landslides at pre-1977 man-made slopes.

For slopes affecting important facilities, the quantification of the risk of earthquake-induced landslides may be made using a QRA framework similar to that presented in this Report. This may include a more rigorous allowance for the uncertainties in the key input parameters by means of tools such as reliability-based methods or Monte-Carlo simulations.

The successful application of the QRA technique in the preliminary assessment to evaluate seismic risk illustrates the feasibility and usefulness of this tool in such applications which will provide more insight to the problem than the conventional seismic hazard assessment methodology.

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