Seismic behaviour of soft clay and its influence on the response of friction pile foundations

Garala, Thejesh Kumar; Madabhushi, Spg

doi:10.1007/s10518-018-0508-4

Cited by 38 publications

(15 citation statements)

References 18 publications

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“…In this case, the surrounding soil may undergo large shear strains during earthquake shaking beyond the linear range which makes the accuracy of linear or equivalent linear models at least questionable. In support to the above, recent findings from centrifuge tests on the seismic behavior of soft clays under large intensity levels of input motions ( [15], [16], [17]) revealed attenuation of base acceleration as it propagates through the soil due to the inability of the soft clay to transmit shear stresses close to its limited shear strength. Stiffness degradation with the number of loading cycles has also been observed having a direct impact on the free-field loading imposed on piles [17].…”

Section: Introductionmentioning

confidence: 61%

“…In support to the above, recent findings from centrifuge tests on the seismic behavior of soft clays under large intensity levels of input motions ( [15], [16], [17]) revealed attenuation of base acceleration as it propagates through the soil due to the inability of the soft clay to transmit shear stresses close to its limited shear strength. Stiffness degradation with the number of loading cycles has also been observed having a direct impact on the free-field loading imposed on piles [17]. Such non-linear behavior of soft clays under seismic action and the associated implication on the selection of a proper constitutive law was examined in [18] for a very soft marine clay which exists at the subsoil of Maliakos Gulf in central Greece.…”

Section: Introductionmentioning

confidence: 61%

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A Numerical Study on the Filtering Action of Piles in the Soft Clay of Maliakos Gulf, Central Greece

Rovithis¹,

Laora²,

Iovino³

et al. 2019

Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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The potential of piles to reduce the seismic motion transmitted to the superstructure with respect to the free field motion, due to the kinematic interplay between soil and pile, is explored by considering a single pile embedded in the soft marine clay of Maliakos Gulf subsoil in central Greece. The soil profile consists of a very soft normally consolidated clay layer with nearly-zero stiffness at ground surface, increasing proportionally with depth, underlain by a stiffer layer of sandy clay. The problem is tackled numerically by means of Equivalent linear (EL) and strength-controlled non-linear (NL) constitutive laws to model the behavior of the soil under seismic excitation. The latter is chosen on a magnitude-epicentral distance (M-R) basis from the European Strong-motion Database (ESD), taking into account the seismotectonic regime of the broader area under study. Seven (7) motions recorded at soil type A, according to EC8, were chosen to define an average code-compatible spectrum. The average mobilized stiffness of the free field soil obtained from EL and NL analyses is then introduced into a finite-element model of the soil-pile system to investigate the kinematicinduced filtering action of the pile as affected by pile cap embedment depth and pile diameter. The above is quantified in terms of ratios of spectral accelerations at the pile head and free field at ground surface. Results highlight the importance of considering NL response for such type of soils and conclude on the beneficial role of piles as reflected in a large reduction of the free field spectral acceleration, even for piles with relatively small diameter.

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Section: Introductionmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 61%

A Numerical Study on the Filtering Action of Piles in the Soft Clay of Maliakos Gulf, Central Greece

Rovithis¹,

Laora²,

Iovino³

et al. 2019

Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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“…has shown that the shear modulus values determined during different base excitations for the soil strata in Test-FPC agrees well with the Darendeli ( 2001) modulus reduction curves, especially for the soft clay layer. In addition, Garala and Madabhushi (2019) highlighted the importance of performing nonlinear seismic ground response analysis by accounting cu in the analysis for the sites with soft clays.…”

Section: Ts < Vsmin/(8×fmax)mentioning

confidence: 99%

Role of Pile Spacing on Dynamic Behavior of Pile Groups in Layered Soils

Garala

Madabhushi

2021

J. Geotech. Geoenviron. Eng.

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This research investigates the influence of pile spacing on the dynamic behaviour of pile groups by performing a series of specifically designed dynamic centrifuge experiments on pile foundations embedded in a two-layered soil profile. A single pile and two 3 × 1 row pile groups with different pile spacing were used as model pile foundations, and the soil models consisted of a soft clay underlain by a dense sand. The influence of earthquake frequency on the dynamic behaviour of two-layered soils is discussed using the centrifuge data and 1D site response analysis from DEEPSOIL. Further, the results of these centrifuge tests agreed with the conviction that the group effects will be diminished with the increase in pile-to-pile spacing in a pile group due to reduced pile-soil-pile interaction. However, this reduced pile group effects can lead to larger kinematic pile bending moments in the widely spaced pile group compared to a closely spaced pile group. Moreover, the single pile always has larger bending moments than both the tested pile groups. An exception to this is when there is a significant phase difference between the kinematic and inertial loads for a single pile but not for the widely spaced pile group. The influence of pile spacing on the shadowing effects and location of peak bending moments in the piles of a group are also discussed. Lastly, an attempt is made to evaluate the individual contribution of inertial and kinematic loads for the seismic design of pile foundations considering soilpile-structure interaction effects.

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“…From the perspective of the interaction between homogeneous clay and a pile, Wang and Zhang (2014) conducted centrifuge model tests to study the seismic strengthening mechanism of stabilising piles by assessing the deformation profiles of slopes reinforced by stabilising piles under seismic load. Garala and Madabhushi (2019) studied the interaction between friction piles and soft clay under seismic load in centrifuge model tests. The aforementioned dynamic model tests of slope stabilising piles, and their mechanism of action, are mainly based on the dynamic response characteristics of sand, clay, and other homogeneous slopes; however, there are few studies on the dynamic response of a deposit slope with underlying bedrock and the working mechanism of the coarse-grained rock and soil mixture deposits, thus making it difficult to meet the needs of engineering practice.…”

Section: Introductionmentioning

confidence: 99%

Seismic Performance of Deposit Slopes With Underlying Bedrock Before and After Reinforcement by Stabilising Piles

Sun

Kong

Bai

et al. 2021

Preprint

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The seismic performance of stabilising piles used to reinforce underlying bedrock in a deposit slope is a complex soil-structure interaction problem, on which there is limited design guidance on the optimum use of a single row of rock-socketed piles to reinforce such slopes. Two centrifuge shaking-table model tests at a geometric scale of 1:50 were conducted to ascertain the dynamic responses of the underlying bedrock deposit slopes without and with the use of stabilising piles during an earthquake. Multi-stage seismic waves with various peak accelerations were applied from the bottom of each model. Under seismic excitation, the differences in the response accelerations between the deposit and bedrock increase significantly with the increase in amplitude of the input seismic waves. The two are prone to uncoordinated movement, which leads to slope instability. Setting stabilising piles reduces the crest settlement and angular deformation and changes the natural frequency of the slope crest. The presence of the rock-socketed stabilising piles can bridge the uncoordinated movement of the bedrock and the overlying deposit to some extent. According to the mobilised pile bending moment, shear force, lateral pile-soil load distribution, and pile displacement, the dynamic response characteristics of stabilising piles under continuous multi-level seismic excitation were analysed. The resultant force arising from a distributed load increment on the piles caused by an earthquake is mainly concentrated in the upper part (the point of action of the resultant force is 1.54m below the slope surface). With increases in the peak ground acceleration (PGA) of the input motion, the resistance of the bedrock in front of the stabilising piles increases; moreover, with the increase of PGA, the peak resistance under the bedrock surface of the stabilising piles gradually moves downwards. This finding indicates that the strong seismic motion significantly changes the embedded working state of the stabilising pile.

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Seismic behaviour of soft clay and its influence on the response of friction pile foundations

Cited by 38 publications

References 18 publications

A Numerical Study on the Filtering Action of Piles in the Soft Clay of Maliakos Gulf, Central Greece

A Numerical Study on the Filtering Action of Piles in the Soft Clay of Maliakos Gulf, Central Greece

Role of Pile Spacing on Dynamic Behavior of Pile Groups in Layered Soils

Seismic Performance of Deposit Slopes With Underlying Bedrock Before and After Reinforcement by Stabilising Piles

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