On October 26, 2022, the International Society of Environmental Geotechnology (ISEG) Webinars Series No.3 was successfully held. The speaker of this webinar is Dr. Clarence Choi from the Department of Civil Engineering at the University of Hong Kong, China. More than 2000 people attended the meeting through online meeting room and live broadcast platforms.
First, Dr. Zhengtao Shen, the secretary of ISEG welcomed the guests and delegates on behalf of ISEG president Prof. Bin Shi and Secretary General Prof. Chao-Sheng Tang, and briefly introduced the ISEG Webinar Series (Figure 1). This is a new brand event, in which distinguished experts and scholars in environmental geotechnology in and out the society will be invited to report on the cutting-edge scientific and technological innovations in the field, aiming to widely promote exchanges and cooperation in the frontier fields of environmental geotechnology. Then, Dr. Zhengtao Shen introduced the biography of the speaker. Dr. Clarence Choi is an assistant Professor of Civil Engineering at the University of Hong Kong. His research interests are on the prediction and mitigation of landslide hazards, and ground improvement. His research has been awarded various awards, including the 3rd Hutchinson Lecture, ISSMGE Bright Spark Award, R.M. Quigley Prize from the Canadian Geotechnical Society, and Telford Premium Prize from ICE, UK. He serves on editorial panels, including Landslides and Engineering Geology. He chairs the debris flow and steep creek hazards committee of the Association of Geohazard Professionals, is a chair-nominated member of TC208 of the ISSMGE on slope stability, and one of 26 international JTC1 members on natural hillsides and slopes.
Figure 1 Welcome speech by Dr. Zhengtao Shen
Subsequently, Dr. Choi started his report entitled “Engineered and Nature-based Solutions against Flow-type Landslides” (Figure 2). He focused on the flow-type landslides and presented his research from the engineered and nature-based solutions. He presented the state-of-the-art in physical and numerical modelling of mitigation strategies against debris flows. In the engineered-based solution, he introduced the existing arts to prevent the landslides, such as rigid barrier, flexible barrier, and baffles. He explained the principle of designing the impact force and put it into practice. For some extreme soil structure interaction problems, he proposed a revised baffle design to measure impact response. In the nature-based solution, Dr. Choi started with the simple single stem + dry sand model, then expanded it to dry sand + dual stems scale. He proposed the stem-scale measurements of flow density, depth, and velocity are necessary to simulate forest-scale dynamics. Considering the constitutive behavior, he came up with a novel, parallelized, GPU-empowered MPM framework, using a constitutive model that can capture phase transition including elastic regime and plastic regime. He concluded that most of geophysical flows are supersonic, which means that the bow shocks would be generated during flow-forest interactions. Through momentum concentration, interactions among bow shocks can change the flow behaviors. This indicates the momentum concentration can promote flow runout. As a result, a forest may not always have protective effects against geophysical flows. Dr. Clarence Choi also showed that even most of the existing plantation forests are square, staggered forests normally have better protective abilities against geophysical flows than square forests. After the presentation, several participants had a lively discussion with Dr. Choi on issues of interest.
Figure 2 Dr. Clarence Choi in presentation
In the end, Dr. Shen gave a brief summary of the event. He thanked Dr. Choi for his wonderful presentation, and thanked all the guests for their participation. He said that that the report of Dr. Clarence Choi is very exciting, and it has a good learning and reference significance for young scholars in terms of model calculation and practical application. This report has brought many new progress and new ideas, and inspired young scholars in many aspects. In the future, this event will be held periodically. He welcomes everyone to continue to participate in this event and work together to promote the development of environmental geotechnology.
The video record of the whole event can be found on ISEG official Youtube Channel and ISEG official Bilibili Channel.
