ABSTRACT
Unsaturated soils are ubiquitous on the surface of the Earth and play an important role in construction engineering and vegetation growth. Their properties are governed not only by the stress state but also by the moisture content (i.e., suction), and are influenced by many factors such as engineering activities, climate change and vegetation. Seepage, deformation and instability in unsaturated soils have led to many disasters (e.g., slope failures, excessive embankment settlement and ecological degradation) and pose a threat to sustainable development, especially under climate change. The classical theory of unsaturated soil mechanics is inadequate to accurately analyse seepage–deformation–stability coupled problems under the effects of climate change and engineering activities. It also does not consider the hydromechanical interaction between unsaturated soil and vegetation. To redress these lacunae in the applicability of the classical theory, the research team led by the speaker conducted extensive research on unsaturated soil mechanics and its applications. The team revealed the state-dependent hydromechanical coupling behaviour of unsaturated soils and developed a novel state-dependent elasto-plastic constitutive framework. The new framework was used to formulate design guidelines to improve the design of slopes and pavements. It was also adopted to establish a state-dependent method for the analysis and design of deep excavations. The research team also developed a theoretical method for calculating the seepage and stability of vegetated unsaturated soils, establishing a solid scientific basis for investigations of unsaturated bioengineered slopes. The team also developed a novel sustainable earthen cover system that eliminates the need for a geomembrane. This new system has now been adopted by China’s national standard “Technical Code for Geotechnical Engineering of Municipal Solid Waste Sanitary Landfill”. Furthermore, the research team developed a novel cover system by using “’waste’ to cover ‘waste’”, achieving the recycling of construction waste resources.
ABOUT THE SPEAKER
Professor Charles W. W. Ng is Chair Professor and CLP Holdings Professor of Sustainability in the Department of Civil and Environmental Engineering at the Hong Kong University of Science and Technology (HKUST). He is also the Dean of HKUST Fok Ying Tung Graduate School, and the Vice-President of HKUST (Guangzhou). He is Fellow of the Hong Kong Academy of Engineering Sciences and Fellow of the Royal Academy of Engineering (International Fellow). He is immediate Past President of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE) (2017–2022) and also the first Chinese president elected since the establishment of the society in 1936. Currently, he is the vice-chair of the Committee of Rock and Soil Mechanics of the Chinese Society of Mechanics and co-Editor-in-Chief of the Canadian Geotechnical Journal. Professor Ng has conducted extensive research in the area of advanced unsaturated soil mechanics and its applications. He is also the Principal Investigator (PI) of several key research grants including Area of Excellence (AoE) project and Theme-based Research project funded by University Grants Committee of Hong Kong. He has published over 400 SCI journal articles and is the main author of three reference books in English. Professor Ng has received many prestigious awards, including the State Natural Science Award (1/5), the State Scientific Technological Advancement Award (4/20), the Ho Leung Ho Lee Foundation Prize for Scientific and Technological Progress, the Varnes Medal from the UNESCO-International Consortium on Landslides, etc.