Seismic liquefaction of heterogeneous soil: mechanism and effects on structural response (original) (raw)

2008

In the current practice of liquefaction prediction analysis, horizontally layered soil (with uniform properties within distinct soil layers) is usually assumed to estimate the liquefaction susceptibility of a soil deposit. However most of the soil properties of a natural deposit not only vary in the vertical direction but they could also vary in the horizontal direction, even within the so-called 'uniform' soil layers. This soil variability can be broadly classified into two main groups. They are the lithological heterogeneity (variability due to geological layers) and the small scale spatial variability. The first source of variability (variability due to layers) is considered properly in the current practice. But the second source of soil variability (small scale spatial variability), which is the subject of this research, is not properly addressed in general. -- From recent numerical research it was observed in the case of seismically induced excess pore water pressure (E...

Effects of Soil Spatial Variability on Liquefaction Resistance: Experimental and Theoretical Investigations

Theoretical research on the effects of random variability of soil properties demonstrated that, in addition to inducing uncertainty in the computed response, natural spatial variability of soil properties affects the mechanical behavior of geotechnical structures. For phenomena involving the presence of a failure surface this behavior can ultimately yield lower failure loads and factors of safety than those resulting from classical reliability analyses based on the assumption of an "average" failure mechanism and small variations about it. For the case of seismically induced soil liquefaction, it has been found that a larger amount of excess pore water pressure is generated in a heterogeneous soil than in the corresponding uniform soil having geomechanical properties equal to the average properties of the variable soil. An explanation for this important phenomenon is provided in this paper based on centrifuge experiments and numerical simulations of heterogeneous and homog...

Elucidation of Seismic Soil Liquefaction Significant Factors

Earthquakes - From Tectonics to Buildings, 2021

The paper develops a framework to analyze the interactions among seismic soil liquefaction significant factors using the interpretive structural model (ISM) approach based on cone penetration test. To identify the contextual relationships among the significant factors, systematic literature review approach was used bearing in mind the selection principle. Since multiple factors influence seismic soil liquefaction, determining all factors in soil liquefaction would be extremely difficult, as even a few seismic soil liquefaction factors are not easy to deal with. This study highlighted two main characteristics of seismic soil liquefaction factors. First, the seismic soil liquefaction factors–peak ground acceleration F2 (amax), equivalent clean sand penetration resistance F5 (qc1Ncs), and thickness of soil layer F11 (Ts) influenced soil liquefaction directly and were located at level 2 (top level) in the ISM model, meaning they require additional seismic soil liquefaction factors excep...

Effect of the Spatial Variation of the Shear Modulus on Soil Liquefaction Potential

Soil liquefaction is at the origin of major damage caused by an earthquake, both human lives lost as well as material losses. Several authors have studied soil liquefaction using deterministic and probabilistic methods. In this paper we study the effect of variation of the shear modulus on soil response defined by the excess pore pressure ratio (r u). Shear modulus is modeled by a log-normal random field, while discretization of the field is done using Karhunen Loève method. Finn deterministic model of liquefaction is modeled using the finite difference software Flac 3D. The results show that the spatial variation of soil properties has a significant impact on the excess pore pressure ratio.

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