Mechanical consequences of internal soil erosion

Abstract

Internal erosion sometimes occurs in dams and slopes. Under seepage, fine particles in soil may migrate through the pores formed by the coarse matrix. The mechanical properties of the soil may then change due to the loss of fine particles. Extensive laboratory tests are conducted in this research to study the shear strength of a dense, internally unstable soil subjected to the loss of fine particles. The soil exhibited strain-softening behaviour prior to internal erosion. Once a significant amount of fine particles was lost, the strain-softening behaviour of the soil would turn into strain hardening. The peak shear strength of the soil decreased slightly, but the shear strength at the critical state increased slightly in response to the loss of fine particles. The peak friction angle decreased by 1.1–5.9° after a loss of 2.5–6.8% of fine particles. Finally, based on the findings of the study, a probable mechanism of the formation of sinkholes and cavities in slopes and slope failures associated with internal erosion problems is presented.

Keywords:

• constitutive relations
• dams
• erosion
• seepage
• shear strength
• slopes

Additional information

Dr Dongsheng Chang obtained his Ph.D. degree from the Hong Kong University of Science and Technology in 2012. He has extensive experience in research and practice in soil erosion-related geotechnical problems and post-earthquake disasters. He is an Associate Member of American Society of Civil Engineers and a Graduate Member of the Hong Kong Institution of Engineers (HKIE). Currently, as an Assistant Engineer in AECOM Asia Company Ltd, he is participating in several infrastructure projects, including the MTR Shatin-Central Link and the Kai Tak Development. He has published 17 technical papers and a book chapter.

Dr Limin Zhang is a Professor of Geotechnical Engineering and an Associate Director of Geotechnical Centrifuge Facility at the Hong Kong University of Science and Technology. His research focuses on slopes and dams, geotechnical risk assessment and pile foundations. He is the Chair of the Geotechnical Safety Network, the Vice Chair of the International Press-In Association, the Past President of the ASCE Hong Kong Section, the Editor-in-Chief of international journal Georisk, an Associate Editor of ASCE's Journal of Geotechnical and Geoenvironmental Engineering, and editorial board member of Soils and Foundations, Computers and Geotechnics and several other journals. He has authored or co-authored over 150 international journal papers.

Ir Dr Johnny Cheuk is an Associate Director of AECOM Asia Company Ltd. He obtained his Ph.D. degree from the Cambridge University. He has extensive experience in research and practice in offshore engineering, deep excavation and slope engineering. He is a member of the HKIE Geotechnical Division Committee and the Secretary-General of the Hong Kong Geotechnical Society. He is also an Adjunct Associate Professor at The University of Hong Kong.