Geotechnical Engineering Group
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  Research in Computational Geomechanics  

Three-dimensional Basin Response
Y. M. A. Hashash,* E. Kausel* (MIT)
NSF Mid-America Earthquake Center

Ground motion simulations well constrained by geological and seismic data are an important resource for assessing hazard and designing earthquake-resistant structures, especially in urban areas in the central U.S. where damaging earthquakes are largely unknown and where many buildings have poor seismic resistance. This project will assess the basin effects in the Memphis, Tenn., area and carry out analyses with simple analytical methods, including one- and two-dimensional models. The results of this study will provide valuable information for developing seismic risk maps and designing codes appropriate for the region.

Visualization for Constitutive Relations in Engineering
Y. M. A. Hashash*
NCSA/U of I Faculty Fellowship Program

Material constitutive relations or models are mathematical representations of the mechanical response of material and relate stress and strain states of the material in a three-dimensional space. The relations in addition include descriptions of geometric shapes to represent yield and failure surfaces. This research explores the use of advanced computer visualization techniques and graphics to represent these relations. The visual representation will facilitate the interpretation of three-dimensional states of stress and stress and the influence of a constitutive relation on their evolution due to specified loading conditions.

Stability of Tunnels and Rock Ridges Adjacent to Quarries
E. J. Cording,* Y. Hashash,* M. Ajlouni, S. J. Lee, J. M. Oh, J. S. Moon
URS Corporation

Investigation of the stability of haul tunnels beneath an interstate highway as part of the TARP system of the MWSD of Greater Chicago provided an opportunity to investigate the 2-D and 3-D behavior of tunnels and overall stability of the rock ridge beneath the highway. Distinct element analyses, both 2-D and 3-D, were conducted using UDEC and 3-DEC. Two-dimensional evaluations were made of tunnel cross sections and tunnel and ridge cross-sections. Three-dimensional analyses were made of the larger ridge and quarry behavior. The analyses distinguished between conditions where stability problems had developed and where problems were not expected. Correlations with field measurements are being conducted

Direct Field Calibration for Model Simulations of Deep Excavations
Y. M. A. Hashash,* J. Ghaboussi
National Science Foundation

Numerical modeling of geotechnical problems is used routinely in major construction projects. These models and simulations involve nonlinear analysis of staged construction for open-cut excavations, tunnels, slopes, and similar engineered structures. The most important and difficult part of these computer simulations is the representation of the constitutive behavior of the soil strata. In this project, researchers will explore a novel, powerful, and systematic method to calibrate the constitutive model of the soil behavior directly from field measurements. This will be accomplished through the use of autoprogressive method, a neural network based methodology, in the modeling of staged construction for a deep braced excavation.

Non-Linear Seismic Site Response of Deep Soil Deposits
Y. M. A. Hashash*
National Science Foundation, Mid-America Earthquake Center

Ground motion simulations well constrained by geological and seismic data are an important resource for assessing hazard and designing earthquake-resistant structures, especially in urban areas of the central United States, where damaging earthquakes are largely unknown and where many buildings have poor seismic resistance. This project includes the development of new, simplified 1-D site response analysis techniques to examine the influence of very deep soil deposits in the Mississippi Embayment on ground motion propagation. The results of this study will provide valuable information for developing seismic risk maps and designing codes appropriate for the region.

Geotechnical Engineering Group
  Soil Mechanics-Behavior and
Foundation Engineering
Rock Mechanics and Tunneling Computational Geomechanics  
 
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