This study investigated the dynamic response and liquefaction of level saturated-sand deposits subjected to biaxial shaking using a number of centrifuge tests. Dense and loose sandy soil deposits were built in a 2D laminar container and subjected to a series of biaxial base excitations that approximate in somewhat realistic fashion the conditions of a site subjected to earthquake shaking. A dense array of accelerometers and pore pressure sensors was used to monitor the deposit response. The recorded accelerations and pore pressures were employed along with a non-parametric identification procedure to estimate the corresponding dynamic shear stress strain histories. In turn, these histories were employed to assess the effects of non-proportional loading on soil contraction and dilation mechanisms. Pore water pressure buildup was found to be affected by load non-proportionality and a direct function of the phase angle of the induced shear stresses. The loose and dense soil deposits had contrasting as well as similar response patterns.
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