7th Asia-Pacific Conference on Unsaturated Soils, AP-UNSAT2019
23~25 August, Nagoya Convention Center, Nagoya, Japan

Abstract of Keynote Speech(2018.07.02)

“Soil-atmosphere interaction in embankments”
Professor, Yu-Jun Cui
Ecole des Ponts ParisTech, France
Dr. Yu-Jun Cui was Panel Member of Géotechnique for three years. He is now
Associate Editor of Canadian Geotechnical Journal, Vice Chief Editor of Journalof Rock Mechanics and Geotechnical Engineering, Panel Member of
Géotechnique Letters. He is also editorial board members of several other
Journals. He was selected by TC106 and delivered the first European
Distinguished lecture on unsaturated soils in 2016.

ABSTRACT:The stability of earth constructions depends strongly on the climatic conditions. In dry seasons, excessive
water evaporation can lead to surface cracking, modifying the hydro-mechanical behaviour of soils and thus
compromising the constructions’ stability. In wet seasons, significant water infiltration leads to reduction ofsuction and thus decrease of the mechanical performance of constructions. The drying/wetting cycles that theconstructions undergo constantly can only come to enhance the detrimental effects. These points have widely
investigated in the laboratory, but rarely addressed in the field. In this lecture, two cases studies are firstly
presented, one is an experimental embankment with two compacted silty soils and another is an experimental
embankment with lime/cement treated silty/clayey soils. Emphasis is put on the atmospheric conditions
changes and the subsequent changes in suction and water content in the embankments. A numerical tool isalso developed, allowing the soil hydro-mechanical behaviour to be analysed through consideration of
atmosphere interaction. This numerical tool is based on an appropriate water evaporation model on one hand,and on a coupled thermal and hydraulic fluids flows on other hand. It is successfully applied to the analysesof the hydro-mechanical behaviour of two embankments in terms of changes of suction and water content,
showing that it is possible to analyse the earth constructions’ behaviour based on the recent knowledge
developed in unsaturated soil mechanics, provided that appropriate water evaporation model is adopted.

“Unsaturated Soil Mechanics for Disaster Prevention and Maintenanceof Traffic Infrastructure in Snowy Cold Region”
Professor, Tatsuya Ishikawa
Hokkaido University, JapanØ

1987-1989 Graduate School of Engineering, Kyoto University

Ø

1999

Ø

2002-2013 Professor in Hokkaido UniversityØ

2002-213

granted Dr. Eng. from Kyoto University
Secretary of ISSMGE TC 202 (Transportation Geotechnics)

ABSTRACT:In snowy cold regions, the 0 °C isotherm may penetrate deep into soil ground, thereby causing somegeotechnical problems specific to cold regions such as the swelling of pavement surface due to frost heave,
the cracking in asphalt-mixture layer due to freeze-thaw, and the slope failures at cut slope and embankment
in snow-melting period. Such phenomena are thought to accelerate deterioration of traffic infrastructures andlosing of the functions. The primary cause is deemed to be the increase in degree of saturation due to snowmelt
and/or ice lens melting in addition to the change in deformation-strength and water retention-permeability
characteristics of soils resulting from freeze-thawing. Hence, it is indispensable to examine the influence of
rapid increase in water content during thawing periods as well as the freeze-thawing of pore fluid on thehydro-mechanical behaviour of unsaturated soil ground for establishing a precise prediction method of natural
disasters and a rational design method of transportation infrastructures in snowy cold regions.
This keynote lecture reviews and summarizes previous researches related to the unsaturated soil mechanics
for the disaster prevention and maintenance of traffic infrastructures in snowy cold region from the viewpointsof experimental and analytical studies. To this end, this keynote lecture presents two case studies, namely“slope stability problem” and “pavement rutting problem” in thawing periods. In both problems, this keynote
lecture first discusses the mechanical behaviour of the soil slope during freezing and thawing based on the
results of the long-term field measurement of soil slope in Hokkaido and full-scale and small-scale model
tests of soil slopes and pavement subjected to freeze-thaw actions. Next, it discusses the change in the physicalproperties, the water retention-permeability characteristics, and the deformation-strength characteristics ofgeomaterials caused by freeze-thaw actions based on the results of various types of laboratory element tests
under saturated and unsaturated conditions. Last, it discusses the applicability of numerical simulations,which can consider the interactions among thermal analysis, seepage analysis, and deformation analysis, tothe failure mechanism analysis of soil slopes and the deformation analysis of pavement in snowy cold regions
from the viewpoint of the variation in water content due to snow and ice lens melt and the change in material
properties due to freeze-thaw. Finally, this keynote lecture discusses the contributions of unsaturated soil
mechanics to the disaster prevention and maintenance of traffic infrastructures in snowy cold region in termsof the mechanism of the slope failures and pavement rutting, and its influencing factors by comparing thephenomena in temperate regions with those in snowy cold regions.

“Soil-Water Characteristic Curves– Determination, Estimation and Application”
Associate Professor, Eng Choon Leong
Nanyang Technological University, Singapore
Dr. Leong Eng Choon is currently an Associate Professor at Nanyang
Technological University, Singapore. He has over 30 years of teachingexperience in geotechnical engineering and is an active researcher in unsaturated
soils and soil dynamics. He has published more than 320 journal and conference
papers. He is currently an editorial board member of several journals and is anactive reviewer for many journals. He has won several awards, notably the
Excellence in Reviewing for the Geomechanics for Energy and the Environment
journal in 2018, the Koh Boon Hwee Mentor award in 2013, and the ASTM best
paper award in 2006. He is also active in the national standardization
programmes in SPRING, Singapore. He is the lead author and co-author of thebooks entitled “Guide to Research Projects for Engineering Students - Planning,
Writing, Presenting” and “Mechanics of Residual Soils, 2nd Edition”,
respectively.
ABSTRACT:The soil-water characteristic curve (SWCC) or water retention curve is a relationship between watercontent in a soil and suction. The SWCC was first plotted by Edgar Buckingham, a soil physicist, in 1907 forsix soils ranging in texture from sand to clay. It was adopted for use in unsaturated soil mechanics by thegeotechnical engineering community. The SWCC is now almost treated as the index property of unsaturated
soils. It has been used as a proxy for permeability and shear strength of unsaturated soil. Most soils have asigmoidal SWCC, otherwise known as a unimodal SWCC as opposed to a bimodal SWCC which has beenfound for some soils. Although determining the SWCC is easier than determining permeability or shear
strength for unsaturated soil, the test is still time-consuming and it is not easy to determine the entire SWCC.
Incomplete or insufficient SWCC data may lead to an incorrect SWCC and hence inaccurate determinationof permeability and shear strength. Progress has been made to expedite the experimental determination of
SWCC as well as estimating the SWCC from basic soil properties using pedotransfer functions. In addition,
SWCC has been represented using volumetric water content, gravimetric water content or degree ofsaturation. Different representations may have dire consequences on its application. Determining the SWCC
using volumetric water content or degree of saturation presents challenges in estimating the instantaneousvolume during the experiment. In this paper, the current state-of-the-art in determining, representing andestimating SWCC and its applications are described and critically examined.

“Effect of stress and suction on resilient modulus of compacted
unbound materials”
Professor, Seong-Wan Park
Dankook University, Korea
Ø

Professor, Dankook University (2003–Present)ØMember of ISSMGE (TC106) and core member (ISSMGE TC202)

Ø

Editor-in-Chief, Journal of Korean Geotechnical Society (2015-2017)ØSenior Editor, KSCE Journal of Civil Engineering(2016-Present)

Ø Senior Researcher, Korea Institute of Construction Technology (20002003)
ABSTRACT:Over the last several decades there has been a significant shift from the use of empirical approaches towards
the use of mechanistic models and unsaturated soil mechanics to characterize and predict the behavior oftransportation infrastructure and geomaterials. Particularly, resilient modulus is an important mechanicalparameter for the study of the behavior of unbound materials under cyclic and traffic loadings. Some studies
have indicated that soil suction has an effect on resilient modulus of unbound materials and that there is a
non-linear response of this feature for geomaterials during the loading process. Nevertheless, an assessmentthat couples the dependency of resilient modulus on stress and suction is still lacking. This study addresses
this through a detailed analysis of resilient modulus under moisture conditions using suction stress concept
on unsaturated soils. Results show a non-linear variation of resilient modulus with stress and that suction
stress has a significant influence on it. The model proposed to couple the effect of moisture and stress onresilient modulus presents better prediction performance of compacted unbound materials.

“Environmental degradation of clayey rocks”
Senior Lecturer, Jubert Abdres Pineda
The University of Newcastle, Australia
Dr. Jubert Pineda received a Bachelor Degree in Civil Engineering from theSanto Tomas University (Bogotá, Colombia). He obtained a Master Degree inGeotechnical Engineering from the National University of Colombia and a PhD
Degree in Geotechnical Engineering from the Technical University of Catalonia(UPC, Barcelona) in 2012. At present he works as Senior Lecturer at the Priority
Research Centre for Geotechnical Science and Engineering (PR-CGSE) in the
University of Newcastle Australia.
Dr. Jubert Pineda has been involved in several research and consulting projects
associated with unsaturated soils, stability of dams founded on clayey rocks aswell as high-quality sampling and testing of soft soils. His current researchinterests include mechanics of soft soils, unsaturated soils, mechanics of hardsoils-soft rocks and more recently Geo-Engineering problems related to Energy
and Sustainability.
ABSTRACT:

Clayey rocks are common in many countries, and are frequently present in civil engineering projects. A
recurrent observation in these materials is their transitional nature, which emerges mainly when they are
excavated and exposed to weathering processes as those caused by cyclic variations in relative humidity (RH)or suction. Marls, shales, claystones, mudstones, siltstones and very stiff clays are examples of materials that
undergo these changes. Despite intrinsic geological differences, clayey rocks show two similar
characteristics: (i) a behaviour intermediate between rock and soil; and (ii) a high ‘degradation’ potential
ability to change their mechanical properties, transforming the clayey rock into a soil. This transition isespecially relevant when the rock is exposed to unloading and environmental effects, which may leads tostability problems or unexpected deformation of geotechnical infrastructure.
Rock degradation has commonly been related to increase in water content due to cyclic variations inrelative humidity. Such cyclic behaviour is accompanied by irreversible volume changes, reduction in rockstrength and rock stiffness as well as increase in rock permeability. Tracking of the variations in mechanicalproperties is fundamental for proper understanding of the rock degradation phenomena.
In this presentation, the mechanisms leading to the degradation of clayey rocks when exposed toenvironmental effects are evaluated. The main aspects controlling the degradation of clayey rocks are studied
in this presentation: (i) the number of applied RH cycles, N, (ii) their amplitude, ∆RH, (iii) the influence ofthe stress level (p-ua), (iv) the effect of the fluid used to induce rock saturation (liquid water or vapour) and(v) the chemistry of the pore fluid. Particular emphasis is given to the consequences of the relative humidity
cycling on rock microstructure. The development and implementation of non-conventional experimental
techniques for inducing and tracking rock degradation, at micro and ‘macro’ scales, is described. An
experimentally-based framework of behaviour is presented which may be used in practice for the evaluationof the degradation potential of clayey rocks.

“Field techniques for measuring soil hydraulic properties
in unsaturated soils”
Professor, Yuji Takeshita
Okayama University, Japan

ABSTRACT:

It is well established that filed or in-situ measurements of the soil hydraulic properties are essential topractical and accurate prediction of water movement in unsaturated soils such as natural slope, embankment,
landfill and agricultural field. The soil hydraulic properties consist of the saturated hydraulic conductivity,
the unsaturated hydraulic conductivity and the soil water characteristic curve defined as a relationshipbetween water content and matric potential (the suction of a soil).
The hydraulic conductivity of unsaturated soils should be measured in the field. Because air bubbles areusually entrapped in porous media when they are saturated by infiltrating water, the saturated hydraulicconductivity measured in unsaturated soil is lower than the truly saturated hydraulic conductivity measured
by laboratory experiments and is often referred to as a field-saturated hydraulic conductivity. Field methods
for determining the field-saturated hydraulic conductivity of unsaturated soils include constant head
infiltration and/or gravity drainage events for near-surface application. For measuring the soil water
characteristic curves, it is often difficult to interpret in-situ measurements unless carefully controlled
boundary conditions are applied. As a results, the soil water characteristic curves are most generally measured
in the laboratory experiments using well-controlled initial and boundary conditions. Whereas laboratory
experiments have the advantage of being easy, quick and precise, a major disadvantage is that they lead tosoil properties that are often non-representative of field conditions.
Since analyses of the soil hydraulic functions are ultimately directed toward field-scale processes,
determination of in-situ properties is more relevant than data obtained from laboratory analyses. This keynote
speech will review the current status of field experimental techniques of measuring the soil hydraulicproperties in the near surface of unsaturated sandy soils and illustrate their utility for determining key
parameters affecting seepage flow in the unsaturated soils. A few areas in need of further investigation will
be outlined.

“Three-phase coupled seismic analyses of unsaturated/saturated
grounds”
Professor, Ryosuke Uzuoka
Kyoto University, Japan
Ø
Ø
Ø
Ø
Ø

2017.4-present
2010.4-2017.3
2004.3-2010.3
2001.8-2004.3
1999.1-2001.8

Ø

1990.4-1998.12

Professor, Kyoto University
Professor, Tokushima University
Associate Professor, Tohoku University
Assistant Professor, Tohoku University
Researcher, Earthquake Disaster Mitigation
Research Center, RIKEN
Research Engineer, Hazama Corporation

ABSTRACT:

Some Asian countries share a similar natural environment and face the same threats from natural disasters
such as earthquake, typhoon, heavy rainfall, flood, and landslide. What makes a bad situation even worst isthat these natural disasters very often did not come alone, which is known as combined disasters. For example,
a heavy rain and an earthquake likely occur sequentially in a relatively short period. A three-phase coupledanalysis will be a promising tool to discuss dynamic behaviors of unsaturated/saturated grounds such as slopesand embankments during combined disasters. The author reviews recent developments on three-phase
coupled seismic analyses. The equations governing the dynamic deformation of unsaturated soil were derived
based on porous media theory and constitutive models. The effect of pore air pressure on cyclic behavior of
unsaturated sandy soil is discussed through the simulations with three-phase and simplified two-phaseanalyses. The validity of three-phase coupled analyses is shown through simulations of seismic behaviors ofslopes and embankments.

“Volume change behavior of highly compacted GMZ bentonite underchemo-hydro-mechanical conditions”
Professor: Weimin Ye
Tongji University, China
Dr. Weimin YE is a Professor of geological/geoenvironmental engineering in
School of Civil Engineering at Tongji University in Shanghai. He earned his PhD
in Structure Engineering from Tongji University, with specialization in
excavation and geo-environmental protection. Dr. YE’s area of expertise isgeological/geoenvironmental engineering with particular emphasis in
Unsaturated Soil Engineering. He is conducting research in compacted bentonite
for using as buffer materials in deep geological repository for disposal of highlevel radioactive waste in China. In this direction, he is exploring the engineering
properties of GMZ bentonite under Chemo-thermo-hydro-mechanical coupling
conditions. He has more than 200 publications including more than 80
international journal papers and got 5 awards from the local government forcontributions to research.
ABSTRACT:Due to its low hydraulic conductivity, high swelling capacity and good adsorption properties, theGaomiaozi (GMZ) bentonite has been selected as potential buffer/backfill materials for construction of
artificial barriers in the deep geological repository for disposal of high-level nuclear waste (HLW) in China.
During the long-term operation of a repository, the compacted bentonite will inevitably experience wetting
or drying processes with hydration or dehydration of groundwater with different concentrations. Furthermore,these processes will take place in the repository with a limited space and certain geo-stresses generated by
the upper geological formations.
In this work, compacted GMZ bentonite with an initial dry density of 1.70 g/cm3 was hydrated with distilledwater and NaCl solutions. For a given suction, the measured void ratio of specimen saturated with distilledwater is slightly larger than those of the specimens saturated with salt solutions after the drying equilibrium
is reached. The degree of saturation of compacted GMZ bentonite specimen increases as the salt concentration
increases under the same total suction. A modified soil water retention curve (SWRC) equation was proposedto account for the effect of void ratio and salt solutions on the drying behavior of the specimens. Verifications
reveal that the proposed equation can satisfactorily describe the SWRCs of compacted GMZ bentonite
saturated with different concentrations of salt solutions. In the meantime, volume change behavior of highly
compacted GMZ bentonite was studied under coupling chemo-hydro-mechanical conditions. Using amodified oedometer, cyclic wetting and drying tests were conducted on compacted GMZ bentonite with
infiltration of NaCl solutions under different constant vertical stresses. Specimens were infiltrated withdifferent concentrations of NaCl solutions during the wetting tests and a suction-control method was used in
the drying tests. Results show that the swelling strain on wetting and the shrinkage strain on drying decrease
with the increase of the vertical stresses or the concentration of NaCl solutions. Plastic deformations mainly
occurred in the first wetting and drying cycle and decreased with the increase of the vertical stresses.
However, the accumulated plastic deformation increased with increasing concentration of NaCl solutions,which could be attributed to the effects of osmotic consolidation. Based on the test results, a modified
Barcelona Expansive Model (BExM) model with consideration of the influences of NaCl solutions withdifferent concentrations was proposed in this work. The micro-/macro- coupling equations fD (suction
reduction) and fI (suction increase) were improved for the specimens saturated with different concentrationsof NaCl solutions. Simulations show that the modified BExM model can be used satisfactorily to describe
the wetting/drying behavior of compacted GMZ bentonite specimens with consideration of the influences of
NaCl solutions with different concentrations.

“A Photogrammetry-Based Method to Measure the Total and Localized
Volume Changes of Unsaturated Soil Specimens during Triaxial Testing”
Associate Professor: Xiong Zhang
Missouri University, USA
Dr. Xiong Zhang is an associate professor in the Department of Civil,
Architectural and Environmental Engineering at the Missouri University of
Science and Technology (Missouri S&T). His research focuses on developmentof 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. He
was one of the two speakers of ASCE Geo-Institute (GI) Unsaturated Soils
Committee Webinar on “Introduction to Constitutive Modeling of Unsaturated
Soils.”
Dr. Zhang is currently serving as an Editorial Board Member of Canadian
Geotechnical Journal. He also serves as a vice chair of ASCE GI Shallow
Foundation Committee and committee member of several nationwide technicalcommittees such as ASCE GI Committee on Design of Residential Structures on
Expansive Soil Standards, ASCE GI Pavement Committee, TRB AFP60
Committee on Engineering Behavior of Unsaturated Soils, and TRB AFS20
Committee on Soil and Rock Instrumentation.
ABSTRACT:

Triaxial tests have been widely used to evaluate the soil behavior. In the past few decades, many methods
have been developed to measure the volume changes of unsaturated soil specimens during triaxial testing.
Literature review indicates that until now measuring the volume changes of unsaturated soil specimens during
triaxial testing remains a major challenge for researchers.
In this study, a noncontact method is developed to measure the total and local volume changes of
unsaturated soil specimens using a conventional triaxial test apparatus for saturated soils. The method is
simple and cost-effective, requiring only a commercially available digital camera to take images of an
unsaturated soil specimen during triaxial testing from which accurate 3D model of the soil specimen isreconstructed. In this proposed method, the photogrammetric technique is utilized to determine theorientations of the camera where the images are taken to an accuracy to 3-5 microns, multiple optical ray
tracings are employed to correct the refraction at the air-acrylic cell and acrylic cell-water interfaces, and aleast–square optimization technique is applied to estimate the coordinates of any point on the specimen
surface. Validation tests indicated that the accuracy for the point measurements is less than 76 microns in thewater and less than 0.25% for total volume measurements. Methods are also developed to calculate the total
volume and localized strains based upon the 3D discrete measurement points on the specimen surface.
This method was awarded the “2016 International Innovation Award in Unsaturated Soil Mechanics” by
TC106 within the International Society for Soil Mechanics and Geotechnical Engineering.