Seismic Lateral Response of Piles in Liquefying Soil (original) (raw)
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Soil Liquefaction Effects on R.C.C. Piles
The behavior of foundations during earthquakes is often dictated by the response of its supporting soil due to the ground shaking. In general, there are two types of ground response that are damaging to structures. In one, the soil fails typically by liquefaction, such as in the 1995 Kobe earthquake. In the other, the soil amplifies the ground motion (as in 1989 Loma Prieta earthquake in California).Pile foundations are often used to transfer axial loads through soft soils to stronger bearing strata at depth. The objective of this research is to gain an insight into the failure mechanism of end-bearing piles in liquefiable soils during earthquakes. Thus, it is necessary to develop an analytical model that predicts the fundamental characteristics of R.C.C. Piles within a range of loading that is appropriate for the structural system. Case history of pile foundation during earthquake has been discussed and the centrifuge modeling has been done. A pile model has been developed, tested and compared with equivalent concrete pile. It is concluded that the codes of practice need to include a criterion to prevent buckling of slender piles in liquefiable soils. It is necessary to select a pile section having a margin of factor of safety against buckling under the worst credible loads.
A parametric study on seismic performance of piles embedded in two-layered liquefiable ground
2011
In this paper, fully coupled three-dimensional dynamic analysis is carried out to investigate the dynamic behaviour of pile foundations in liquefied ground. The critical state bounding surface elastic-plastic constitutive model, Dafalias and Manzari (2004) is used, while a fully coupled (u-P) formulation is employed to analyze soil displacements and pore water pressures. Furthermore, variation of permeability coefficient during liquefaction is taken into account. Seismic response of a single pile in liquefiable soil layers is compared with the results of a centrifuge test, and it is found that there is a good agreement between the test results and the computed data. Then, the verified model is used for a parametric study by varying pile length, thickness of liquefying soil layer, relative density of liquefying soil layer and frequency of input motion. The parametric study is carried out for a single pile embedded in a two-layered ground: the upper layer is liquefiable while the lowe...
Effect of lateral load on the pile’s buckling instability in liquefied soil
2017
Even with modern design guidelines, the collapse of pile-supported structures in liquefiable deposits is still observed after strong earthquakes, and buckling instability of piles has been cited as a possible mechanism of failure in liquefiable soils. However, the effect of lateral load on buckling instability of the pile in liquefied soils has not been adequately investigated. This paper presents a shake-table test, which is conducted to study the failure mechanism of an end-bearing pile partly embedded in a saturated sand layer. It is found that pile with a large mass at the top failed in buckling after the soil fully liquefied. Then, a pseudo-static analysis method is proposed to evaluate the buckling instability of the pile under the combination of lateral and axial load. The buckling load of the pile was found to decrease with the increase in lateral inertial load. It is hence important for the designers to consider the level of lateral loading during buckling analysis of pile ...
Designing piles in soils with liquefaction capability
Piles in fact are like thin and resistant columns that are laterally supported by surrounding soil and there found interaction between piles and soil. Piles that passes from different layers of liquefaction soil due to the liquefaction resulted from earthquake force lose their lateral support. In these conditions the pile could be like a non-resistant column be ready for axial and shear instability. This instability and wasting the interaction between soil and pile could lead to lateral buckling of pile in weaker direction and plastic hinge. In the last years many cases of pile foundation rupture at bridges and buildings due to the liquefaction of soil layers after earthquake have been reported that caused the collapse of the structures, while these piles were designed according to valid regulations such as Japan Road Association and National Earthquake Hazards Reduction Program. Then it seems that the behavior of these piles and their analysis method is not fully known. Therefore in this research we study the buckling capacity of piles in layered liquefaction soils.
Earthquakes - From Tectonics to Buildings, 2021
This chapter presents a concise overview of the mechanics of failure, analysis and requalification procedures of pile foundations in liquefiable soils during earthquakes. The aim is to build a strong conceptual and technical interpretation in order to gain insight into the mechanisms governing the failure of structures in liquefaction and specify effective requalification techniques. In this regard, several most common failure mechanisms of piles during seismic liquefaction such as bending (flexural), buckling instability and dynamic failure of the pile are introduced. Furthermore, the dynamic response commentary is provided by critically reviewing experimental investigations carried out using a shaking table and centrifuge modelling procedures. The emphasis is placed on delineating the concept of seismic design loads and important aspects of the dynamic behaviour of piles in liquefiable soils. In this context, using Winkler foundation approach with the proposed p–y curves and finit...