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

Abstract

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.

Impact of bidirectional seismic shearing on the volumetric response of sand deposits

“…By using sinusoidal-type waveforms as input, they observed an increase of excess pore water pressure and postshaking settlement of 20% and 10%, respectively. More recently, El Shafee et al [13,14] and Cerna-Diaz et al [15] conducted similar tests on Nevada 120 and Ottawa 40/70 sand deposits, respectively. While El Shafee et al [13,14] used synthesized motions to simulate the phasetime history of real earthquakes, Cerna-Diaz et al [15] employed actual ground motion recordings with different levels of intensity.…”

“…More recently, El Shafee et al [13,14] and Cerna-Diaz et al [15] conducted similar tests on Nevada 120 and Ottawa 40/70 sand deposits, respectively. While El Shafee et al [13,14] used synthesized motions to simulate the phasetime history of real earthquakes, Cerna-Diaz et al [15] employed actual ground motion recordings with different levels of intensity. These studies showed that the increase in excess pore water pressure response during BD shearing may depend on the D r of the sand deposit, and that it can be as much as 100% higher than during UD shearing for the case of dense sands.…”

“…Most of the above research has made possible to foster our understanding on the behavior of saturated sands under BD shearing. However, while some of them highlight its importance on the shearinduced volumetric response of sand deposits [e.g., 13], others suggest that its effects are not significant [e.g. , 12].…”

Evaluation of Liquefaction Potential in Saturated Sand under Different Drainage Boundary Conditions—An Energy Approach

“…In addition, there is another assumption in this research: only one plane of the drainage boundary is taken into consideration as shown in Figure 1. The influence of other planes remains to be explored by applying biaxial dynamic loading [21,22]. By controlling k i , the permeability of the drainage path can be simulated.…”

Energy Evaluation of Triggering Soil Liquefaction Based on the Response Surface Method

“…This method can be divided into three groups based on case histories during earthquakes that occurred in the past [14][15][16], the Arias intensity (I h ) [17,18], and laboratory test results [19,20]. Shafee et al [21] performed some uniaxial shaking tests and demonstrated that the difference between strain energy generated in the soil caused by biaxial and uniaxial shaking tests is negligible. Zheghal et al [22] studied the effect of non-proportionality and the phase angle of the induced shear stresses on rising pore water pressure.…”