Report No. : GEO Report No. 107
Report Title : Review of 1997 and 1998 Landslides (2000), 53 p.
Author : H.N. Wong & K.K.S. Ho
This review aimed to audit the performance of Government's slope safety system and identify improvement to current slope engineering practice. It was carried out by the Geotechnical Engineering Office (GEO) of the Civil Engineering Department, as part of the landslide investigation initiative introduced following the 1994 Kwun Lung Lau landslide.
Nearly 800 landslides occurred in 1997 and 1998, all of which were reviewed. A total of 72 landslide incidents were selected for further study. These studies provided information and insight on the types and mechanisms of landslides in Hong Kong and permit diagnosis of areas requiring attention.
Based on the landslide data in 1997 and 1998, the average annual defect rate in terms of major failures (i.e. failure volume of 50 m3 or above) at slopes that were processed by the slope safety system as being up to the required geotechnical standards is about 0.03%. These include slopes that were previously assessed, designed or upgraded to meet the required geotechnical standards. The corresponding average annual defect rate, based on the landslide data in 1997 and 1998, for slopes dealt with by the Landslip Preventive Measures (LPM) Programme is about 0.075%.
The average annual success rate against major failures on slopes processed by the slope safety system is greater than 99.9% for landslides in 1997 and 1998. Given that 1997 and 1998 were wetter than normal, the actual long-term annual success rate of the slope safety system will be greater than that assessed for 1997 and 1998.
Further improvement in the performance of the slope safety system can be achieved through measures to reduce non-compliances with the stipulated procedures and standards, adoption of more robust and reliable slope works, and enhancement of current slope engineering practice.
Recommendations for improving the performance of the slope safety system are given in the report.
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