为促进学科发展与学术交流，岩土工程研究所邀请美国密苏里科技大学教授张雄博士来我院做学术报告并交流非饱和土领域的研究成果，我所高级工程师尹鹏海博士将参会交流并做题为“非饱和土抗拉强度及蓄水期库岸风积粉土边坡失稳机理”的报告，欢迎各位同事和研究生参加交流！
报告题目：Difficulties associated with use of effective stress for unsaturated soils
报告人：美国密苏里科技大学教授 张雄博士
报告时间：2023年8月14日上午10:00 ~ 12：00
报告地点：岩土工程研究所3楼会议室301室
联 系人：张紫涛
联系电话：010-68786611
电子邮箱：zhangzt@iwhr.com
报告人简介：Dr. Xiong Zhang is the James A. Heidman Professor in the Department of Civil, Architectural, and Environmental Engineering at the Missouri University of Science and Technology (Missouri S&T). He received his Ph.D. degree in Civil Engineering from Texas A&M University. Before he joined in the Missouri S&T, he worked at the University of Alaska Fairbanks and University of Cincinnati for 10 years. Dr. Zhang has been teaching and conducting research in the field of geotechnical engineering since 1992. His studies focus on development of advanced laboratory techniques to rapidly characterize geomaterials, constitutive modeling coupled hydro-mechanical behavior of unsaturated soils, numerical modeling of climate-soil-structure interaction, slope stability analysis, soil stabilization and ground improvement, and frozen ground engineering. Dr. Zhang is currently the Chair of ASCE GI Shallow Foundation Committee, an editorial board member of Canadian Geotechnical Journal, Associate Editor for ASCE Journal of Cold Region Engineering. He is also a committee member of several nationwide technical committees such as ASCE GI Committee on Design of Residential Structures on Expansive Soil Standards, ASCE GI Pavement Committee, and TRB AKG30 Committee on Geo-Environmental and Climatic Impacts on Geomaterials. He received the 2016 International Innovation Award in Unsaturated Soil Mechanics from TC106 Committee on Unsaturated Soils within the International Society for Soil Mechanics and Geotechnical Engineering.
报告内容简介：Some researchers worked on the renewal of the Bishop's effective stress (Khalili et al. 2004; Nuth and Laloui 2008) using elastoplastic theory for unsaturated soils. For example, Khalili et al. (2004) and Nuth and Laloui (2008) argued that the Bishop's effective stress in fact can be used to explain collapsible soil behavior if elastoplastic behavior are recognized. Subsequently, failure to properly consider elastoplastic response of unsaturated soil has often erroneously been cited as the reason for challenges faced in finding an “effective stress” for unsaturated soils (e.g., Lu and Likos, 2006). This paper focuses on elasto-plastic evaluation of stress state variables for constitutive modelling of unsaturated soils. The same experimental data (Wheeler and Sivakumar 1995), which has been used in recent studies to justify the use of effective stress, is re-analyzed by using the Modified State Surface Approach of Zhang and Lytton (2009). The two independent (uncombined) stress state variable approach and Bishop’s effective stress approach are compared to demonstrate the difficulties associated with use of effective stress for constitutive modelling of unsaturated soils. Different options, and associated limitations, are discussed. It is found that it is impossible to define an effective stress for unsaturated soils that functions analogously to that used in saturated soils. Bishop’s effective stress approach for constitutive modelling, is at most a mathematical transformation which may provide simplifications for some limited applications.
