Landslide disaster prevention and mitigation through works in Hong Kong

Hong Kong has a high concentration of developments on hilly terrain in close proximity to man-made slopes and natural hillsides.Because of the high seasonal rainfall,these man-made slopes and natural hillsides would pose a risk to the public as manifested by a death toll of 470 people due to landslides since the late 1940s.In 1977,the Government of the Hong Kong SAR embarked on a systematic programme,known as the Landslip Preventive Measure(LPM)Programme,to retroft substandard man-made slopes.From 1977 to 2010,about 4500 substandard government man-made slopes have been upgraded through engineering works.During the period,the Programme had evolved progressively in response to Government’s internal demand for continuous improvement and rising public expectation for slope safety.In 2010,the Government implemented the Landslip Prevention and Mitigation(LPMit)Programme to dovetail with the LPM Programme,with the focus on retroftting the remaining moderate-risk substandard man-made slopes and mitigating systematically the natural terrain landslide risk pursuant to the"react-to-known"hazard principle.This paper presents the evolution of the LPM and LPMit Programmes as well as the insight on landslide prevention and mitigation through engineering works.

Poisson's ratios and S-wave velocities of the Xishancun landslide,Sichuan,China,inferred from high-frequency receiver functions of local earthquakes

Landslides are recurrent geological phenomena on Earth that cause heavy casualties and property losses annually.In this study,we use the V_(p)-k stacking and nonlinear waveform inversion methods of high-frequency receiver functions extracted from local earthquakes,to sequentially invert Poisson’s ratios and S-wave velocities of the Quaternary Xishancun landslide,which is composed of three segments,i.e.,h1,h2,and h3 from bottom to top.Our results show that Poisson’s ratio values are generally higher than 0.33 and that the S-wave velocities vary from 0.1 to 0.9 km s^(-1).High Poisson’s ratios(>0.44)are mainly distributed in the juncture regions between different segments,as well as the western edge of h2.These zones show significant variation in landslide thickness and are potentially hazardous areas.Low velocities of 0.05–0.2 km s^(-1)with thicknesses of 10–30m are widely observed in the lower layer of the landslide.The high Poisson’s ratios and low-velocity layer may be related to water-rich materials in these areas.Our study suggests that the high-frequency receiver functions from local earthquakes can be used to delineate geotechnical structures,which is valuable for landslide stability analysis and hazard mitigation.