Performance of landslide debris-resisting baffles

Abstract

Arrays of landslide debris baffles are commonly installed upstream of rigid barriers in Hong Kong to dissipate flow energy impacting a rigid barrier. Currently, baffles are installed using prescriptive and empirical approaches in Hong Kong without design recommendations. Given the engineering value of baffles, an improved understanding of their interaction mechanisms is warranted. Flume modelling and numerical back analysis using the discrete element method (DEM) were adopted to study the influence of landslide debris baffles on impact on a downstream terminal rigid barrier. Froude scaling was used to dynamically characterise the flow. The optimum geometrical configuration was examined. The results revealed that an array of baffles is effective in reducing the peak dynamic impact induced by debris on a rigid barrier and that overflow processes need to be controlled. Baffle heights exceeding 1.5 times the approach flow depth (h) exhibited little incremental influence on reducing the peak dynamic impact forces induced on the rigid barrier. At least two staggered rows are required to effectively intercept discharge from the first row and reduce the frontal debris impact force. The optimum spacing between successive rows (L) and transverse blockage is L/D = 3 (D is the slit opening) and 30%, respectively.

Keywords:

• landslide debris
• baffles
• impact
• physical modelling
• discrete element method

Acknowledgements

This paper is published with the permission of the Head of the Geotechnical Engineering Office (GEO) and the Director of Civil Engineering and Development, the HKSAR Government, People's Republic of China. The authors would like to gratefully acknowledge the support of the GEO of the Civil Engineering and Development Department (CEDD) of the HKSAR Government for commissioning an investigation pertaining to landslide debris-resisting baffles. The authors would also like to thank Ir Prof Charles W W Ng and the HKUST Jockey Club Institute for Advanced Study for their support. Finally, the authors would like to express their thanks to Ir Herman Y K Shiu and Ir Dr S W Lee for their comments.

Additional information

Funding

This work was supported by a grant from the Research Grants Council of the HKSAR, People's Republic of China (T22-603/15N).

Notes on contributors

Clarence E Choi

Notes on contributors

Prof Clarence E Choi is a faculty member in the Department of Civil and Environmental Engineering at The Hong Kong University of Science and Technology and previously practised geotechnical engineering with Golder Associates (HK) Limited. His research focuses on understanding and mitigating landslides and natural terrain hazards. He is currently a Fellow (Junior) of the HKUST Jockey Club Institute for Advanced Study.

Raymond P H Law

Ir Raymond P H Law is a Geotechnical Engineer working in the GEO of the CEDD. He completed his Ph.D. degree at the Hong Kong University of Science and Technology and has over 10 years of experience of focused research in debris flow mechanics and the interactions of debris with structures, using numerical tools such as the discrete element method as well as flume model tests. He also has good experience in the design of natural terrain mitigation measures in Hong Kong.