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.