Wilson Tang Lecture

Wilson Tang Lecture Geological Uncertainty: A Missing Element in Geotechnical Reliability Analysis
Date / Time 12 December 2019, Thursday / 09:00 - 09:40 hrs
Venue Room IB-101
Lecture C. Hsein Juang
National Central University, Taiwan


C. Hsein Juang has been Glenn Professor Emeritus of the Glenn Department of Civil Engineering at Clemson University since 2018. He is currently a Yushan Scholar and chair professor at National Central University. Dr. Juang earned his BS and MS degree from National Cheng Kung University and PhD degree from Purdue University (1981). He has authored more than 270 technical papers, including over 160 journal papers. Google Scholar lists his h-index at 42 with over 6,800citations. Dr. Juang has received many best paper awards from multiple civil engineering societies andinternational journals. He has received many honors and awards, including the GEOSNet Award 2015 by Geotechnical Safety Network (GEOSNet), the TK Hsieh Award from the Institution of Civil Engineers(ICE), UK, and the Geotechnical Lecturer Award from the Taiwan Geotechnical Society (TGS). Among his achievements, Dr. Juang is most pleased with being selected by his students as the Chi-Epsilon Outstanding Teacher and serving the academic advisor to 22 PhD graduates at Clemson. Dr. Juang hasserved the geotechnical profession in various capacities, including the chair of ASCE technical committee on Risk Assessment and Management (2009-2012), Geo risk 2011 conference chair, and editorial board member of many international journals. He is currently serving as the Editor in Chief for Engineering Geology (Elsevier; impact factor 3.10). Dr. Juang has made many original contributions on the development and applications of reliability-based methods in liquefaction, supported excavations, and landslides/slope stability. His recent work focuses on the development of Robust Geotechnical Design asa new geotechnical design tool that complements both deterministic and probabilistic design approaches, and on the characterization of geological uncertainties for geotechnical reliability-based design.


While the presence of geological uncertainty is often recognized by the engineer, it is seldom considered explicitly in current geotechnical reliability analyses. Indeed, it is largely a missing element in a geotechnical reliability analysis and its effect is generally not known or examined. In this paper, we present a case study to illustrate the characterization and consideration of the geological uncertainty in a geotechnical analysis. We illustrate that when combined with the random field theory, the soil behavior type index (Ic) derived from the cone penetration test (CPT) may be used to determine the composition of the ground at any given point, which forms a basis for characterization of the geological uncertainty at a site. Once the uncertainty associated with Ic is quantified, it may be used to assess the uncertainty associated with the soil stratigraphy and the impact of the geological uncertainty on the predicted geotechnical performance. Further, in the random field modeling the scale of fluctuation is an important parameter that defines the distance within which the information gathered through CPT sounding at a given location can affect the neighboring area. When the number of CPT soundings at a site is relatively small, the estimated scale of fluctuation may not be robust. The results obtained through the random field modeling can help guide decision on how to conduct additional site investigation work. Suggestions are also made for future studies regarding the identification and characterization of the geological uncertainty for use in the geotechnical analysis.

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