Centrifuge modelling and analysis of site liquefaction subjected to biaxial dynamic excitations

The paper presents a series of centrifuge tests simulating a level site consisting of granular soil deposits subjected to various biaxial and uniaxial base excitations. The tests were conducted at RPI NEES centrifuge facility to assess the dynamic response characteristics of level deposits under multidirectional shaking. Synthetic sinusoidal waves were used as base excitations to test loose models under biaxial and uniaxial shaking. Dense arrays of accelerometers were used to monitor the deposit response along with pore water pressure transducers. Two uniaxial tests and one biaxial shaking test were conducted on three similar soil models to study the impact of multidirectional shaking on the generation of soil liquefaction. The two uniaxial shaking tests consisted of: (a) a test with input energy content using an Arias intensity similar to that of the biaxial input shaking and (b) a test with 10% increase in one of the components of the biaxial shake amplitude, as commonly done in practice for uniaxial simulation of multidirectional field shaking. The observed acceleration and pore pressure are used along with non-parametric identification procedures to estimate the corresponding dynamic shear stress–strain histories. The measured results along with the stress and strain histories obtained are used for two purposes: first, to shed light on the properties of liquefaction occurring through the stratum under uniaxial shaking; second, to show the difference in soil behaviour when it is subjected to biaxial shaking. The latter purpose is evident in the strain energy generated in the biaxial test compared to that of equivalent and traditional uniaxial tests.