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VERSION:2.0
PRODID:-//Memento EPFL//
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SUMMARY:A Unified Effective Stress Concept for Variably-Saturated Soil
DTSTART:20101209T121500
DTSTAMP:20260510T031951Z
UID:d8626160435c4aacc0ffb223d9b330904aafb04d0128895d0dd7e34b
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Ning Lu\, Colorado School of Mines\nA unified effective 
 stress concept based on the suction stress characteristic curve (SSCC) for
  variably-saturated soil is discussed. Particle-scale equilibrium analyses
  are employed to distinguish three types of soil interparticle forces: (1)
  active forces transmitted through the soil grains (Terzaghi's)\; (2) acti
 ve forces at or near interparticle contacts (physicochemical)\; and (3) pa
 ssive\, or counterbalancing\, forces at or near interparticle contacts (Bo
 rn's and steric). It is proposed that the second type of forces\, which in
 cludes physicochemical forces\, cementation forces\, surface tension\, and
  the force arising from negative pore-water pressure\, can be conceptually
  combined into a macroscopic stress called suction stress. Suction stress 
 characteristically depends on degree of saturation\, or soil suction\, thu
 s paralleling well-established concept of the soil-water characteristic cu
 rve in soil physics. The existence and behavior of the SSCC are experiment
 ally validated by considering unsaturated shear strength and volumetric be
 havior data for a variety of soil types in the literature. The characteris
 tics and practical determination of the SSCC are demonstrated. A closed fo
 rm equation for predicting the suction stress for all soils is found. A ca
 se study of shallow landslide initiation\ninduced by heavy rainfalls illus
 trates that variation in suction stress can well reconcile the spatial and
  temporal characteristics of the event. Suction stress provides a potentia
 lly simple and practical means to describe the state of stress in unsatura
 ted soil.\n\nNing Lu is professor of engineering at Colorado School of Min
 es and the director of the joint CSM/USGS Geotechnical Research Laboratory
 . He obtained a PhD degree in engineering science from the Johns Hopkins U
 niversity in 1991. Prior to joining Colorado School of Mines in 1997\, he 
 worked at Disposal Safety Inc.\, at the US Geological Survey\, and as an a
 ssistant professor at Louisiana State University. His primary research int
 erests are to seek common threads among soil physical phenomena including 
 fluid flow\, chemical flow\, heat transfer\, stress\, and deformation\, an
 d to build bridges from atomic-scale potentials to particle-scale forces a
 nd engineering-scale stresses in soil. He is the senior author of the text
  book "Unsaturated Soil Mechanics" (John Wiley and Sons)\, recipient ASCE'
 s Normal Medal (2007) and J. James Croes Medal (2010). He will be the Shim
 izu Visiting Professor at Stanford University in 2011.
LOCATION:GC A331
STATUS:CONFIRMED
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