The use of steel flexible barriers to mitigate landslide risk on natural hillsides is becoming common in the last decade in Hong Kong. The current design approach for this kind of barrier structure involves the adoption of the hydrodynamic load model to predict dynamic impact forces, followed by non-linear structural analyses of flexible barriers using numerical programs based on the pseudo-static method. From local guidelines, the dynamic pressure coefficient is taken as 2.0. This empirically considers the effect of impacts from boulders up to 2.0m in diameter. With a view to rationalising the design approach, a series of physical impact tests and numerical analyses was conducted to investigate the dynamic impact on flexible barriers and the resulting barrier response. The tests involved up to 9m³ of debris resisted by a 1.5m high steel barrier, conducted at the 28m long flume facility at the Kadoorie Centre, Hong Kong. Numerical modelling using computer programs LS-DYNA and NIDA-MNN was conducted to analyse the dynamic response. The study aims to evaluate the dynamic pressure coefficient and to verify the current design approach. Results indicate that a coefficient of 1.0 is in general appropriate for design purposes for debris comprising primarily water and fine-grained particles.

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It is common practice to assess the deformation of structures due to tunnelling-induced effects by assuming that foundation movements coincide with greenfield tunnelling movements. This often overestimates the resulting movements and stresses on the structures and may fail to give the correct deformed shape for detailed damage assessment. This paper proposes a novel approach to study the interaction between tunnels and framed structures, based on the translational and rotational stiffness of foundations from the field of seismic engineering. This approach can readily be deployed in routine civil engineering design and tunnelling impact assessment.

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