Shear Modulus Degradation of Liquefying Sand: Quantification and Modeling Shear Modulus Degradation of Liquefying Sand: Quantification and Modeling
This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value.
Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the “degrading shear modulus backbone curve method” reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.
School:Brigham Young University
School Location:USA - Utah
Source Type:Master's Thesis
Keywords:geotechnical engineering earthquake liquefaction liquefying sand shear modulus modeling degradation acceleration time history velocity displacement ground motions liquefiable soils backbone curve port island downhole array 1995 kobe excess pore pressure ratio response spectrum equivalent linear method nonlinear stress strain loop hysteretic nera
Date of Publication:03/10/2006