Design of flexible barriers against sizeable landslides in Hong Kong

ABSTRACT

A new type of flexible debris-resisting barrier has been designed using the state-of-the-art analytical force approach for mitigation of channelised debris flow hazards in a hillside study area in Hong Kong. Unlike the conventional three-panel rectangular form, these flexible barriers were configured in a valley shape to geometrically fit in the incised drainage lines. The “design event” resulted in a calculated debris impact pressure of up to 400 kPa and over 10,000 kJ in terms of impact energy necessitating a site-specific design. The design involved advanced structural modelling of the highly non-linear behaviour of flexible barriers under debris impact giving rise to a large deformation. This paper presents the design and detailing of these valley-shaped flexible barriers, involving formulation of the design methodology, derivation of the multi-phase impact load model and optimisation of the barrier configuration. To support the design, numerical parametric studies were conducted to examine the barrier’s impact behaviour. Two design initiatives were highlighted for enhancing the design robustness, including a rigorous approach to analyse the effects of the energy-dissipating devices on barrier performance and a robustness check to cater for adverse scenarios that could conceivably happen. Some suggestions on configuring a valley-shaped flexible barrier were given.

KEYWORDS:

• Flexible barrier
• natural terrain landslides
• drainage line
• design
• force approach
• Hong Kong

Acknowledgements

This paper is published with the permission of the Head of the Geotechnical Engineering Office, the Director of Civil Engineering and Development, and Architectural Services Department, the HKSAR Government.

Additional information

Notes on contributors

Eric H Y Sze

Ir Dr Eric H Y Sze obtained his Ph.D. in Geotechnical Engineering from The University of Hong Kong. He is currently a Geotechnical Engineer in the Geotechnical Engineering Office (GEO), Civil Engineering and Development Department (CEDD) of the HKSAR Government. His research interest is on numerical modelling of impact problems, soil dynamics and liquefaction. He has been a designer for flexible debris-resisting barriers and is now responsible for the research and development work for natural terrain hazard mitigation measures in Hong Kong.

Raymond C H Koo

Ir Dr Raymond C H Koo is a Geotechnical Engineer of the GEO, CEDD of the HKSAR Government. He has a variety of working experience in geotechnical engineering projects in Hong Kong. He has particularly developed his research skills in seismic and blasting dynamic analysis and hazard assessment.

Jojo M Y Leung

Ir Jojo M Y Leung obtained her MEng degree from the University of Warwick, the UK. She is currently a Structural Engineer in the Architectural Services Department of the HKSAR Government. She has been a designer for flexible debris-resisting barriers.

Ken K S Ho

Ir Prof Ken K S Ho graduated from the Imperial College London. He is the Deputy Head of the GEO, CEDD of the HKSAR Government and an Adjunct Professor at The University of Hong Kong. Ir Prof Ho has published over 100 technical papers and presented a number of keynote papers at various international conferences. He is a core member of Joint Technical Committee (JTC1) of the Federation of International Geo-engineering Societies on Landslides. He serves on the editorial boards of the journals Landslides and Georisk. He is currently the Chairman of the Institution of Civil Engineers (Hong Kong Association) and Deputy Chairman of the Geotechnical Discipline Advisory Panel of The Hong Kong Institution of Engineers.