Abstract: The constitutive behavior of soils such as strength, stiffness, and localization of deformations are to a large extent derived from inter-particle friction transmitted between solid particles and particle groups.  Inter-particle forces are highly dependent on gravitational body forces.  At very low effective confining pressures, the true nature of the Mohr-Coulomb strength envelope, which is the criterion most frequently used, is unclear both with respect to inter-particle friction and cohesion.  Because of the impossibility of eliminating gravitational body forces on earth, the weight of soil grains develops inter-particle compressive stresses which mask true soil constitutive behavior even in the smallest samples of models.  Therefore, the microgravity environment induced by near-earth orbits of spacecraft (NASA Space Shuttle) provides unique experimental opportunities for testing theories related to the mechanical behavior of soils.  Such materials may include cohesionless soils, silt, clay, industrial powders, crushed coal, etc.  This presentation discusses the importance of testing sand under very low confining stresses, effects of gravity on the stress-strain behavior of sand, and examples of potential future exploration missions to the moon and to Mars.

Khalid A. Alshibli, Ph.D., PE.

Professor Khalid Alshibli is a visiting professor at Ali Al-Naimi Petroleum Engineering Research Center. He is the Associate Department Head, Professor, and coordinator of Geotechnical and Materials Group,  Department of Civil and Environmental Engineering, University of Tennessee-Knoxville (UTK), USA. He served as a faculty member at Louisiana State University (LSU) for almost 11 years before joining UTK in 2011. Professor Alshibli earned his Ph.D in Geotechnical Engineering from University of Colorado at Boulder in 1995. More information about professor Alshibli research can be found here.

Light refreshments will be served at 3:45.