Large-Scale Shake Table Tests on a Shallow Foundation in Liquefiable Soils

Orang, Milad Jahed; Motamed, Ramin; Prabhakaran, Athul; Elgamal, Ahmed

doi:10.1061/(asce)gt.1943-5606.0002427

Cited by 22 publications

(10 citation statements)

References 48 publications

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“…The input motions for both Shake 1 and Shake 2 were applied at a constant frequency of 2 Hz, with the peak acceleration ranging from 0.53g to 0.66g. Details about ground-motion selection and soil-box specifications can be found in Jahed Orang et al [2021a]. Figure 2.10 presents the isometric view of Helical Pile test before Shake 1.…”

Section: Shake Table Experimental Programmentioning

confidence: 99%

“…More details about ground-model preparation and instrumentation, helical-pile specification, protection and instrumentation, and further groundmodel identification were provided in the following sections. Note: the details of Baseline test series and discussions on the controlling mechanisms of shallow foundation response on top of a liquefiable soil layer is presented in Jahed Orang et al [2021a]; this paper presents the Helical Pile test series mainly focusing on the response of helical piles and their performance in liquefied soils.…”

Section: Shake Table Experimental Programmentioning

confidence: 99%

“…The achieved relative densities for dense, loose, and crust layers were in the range of 85-90%, 40-45%, and 50-55%, respectively. Details regarding the construction method and achieved relative densities for each layer can be found in Jahed Orang et al [2021a]. The model ground for both Baseline and Helical Pile test series was constructed in similar conditions.…”

Section: Model Ground Preparation and Instrumentationmentioning

confidence: 99%

“…Note: although there are no specific seismic design guidelines for using side brackets in the International Building Code (IBC), the designated side brackets performed reasonably well under specific ground motion applied in these shake table tests. In the Baseline test series, the allowable static bearing capacity of the shallow foundation was calculated, yielding a FS greater than three; however, the foundation underwent excessive settlement (during and after first shake), constituting an unsatisfactory performance [Jahed Orang et al 2021a]. Underpinning the shallow foundation with four helical piles was expected to increase the bearing capacity and decrease the settlement, achieving an acceptable foundation performance under static and dynamic loading.…”

Section: Helical Piles Specifications and Instrumentationmentioning

confidence: 99%

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Shake Table Tests on a Shallow Foundation on Liquefiable Soils Supported on Helical Piles

Orang¹,

Motamed²

2021

PEER Reports

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Extensive damage to buildings and infrastructure observed during past earthquakes resulting from the liquefaction of shallow saturated soil deposits underneath structures has demonstrated the necessity for further research in the area of liquefaction-induced ground movement effects. This study explores utilizing helical piles as a countermeasure to reduce liquefaction-induced foundation settlement and investigates their seismic performance in liquefiable grounds. Two large-scale shake table test series, one without any mitigation measures and one using helical piles, were conducted using the shake table facility at the University of California, San Diego. During each test series, the soil and superstructure models were extensively instrumented and subjected to two consistently applied shaking sequences. The model ground included a shallow liquefiable layer aimed at replicating the subsurface ground conditions observed in the past earthquakes in New Zealand, Japan, and Turkey. Liquefaction-induced foundation settlement mechanisms are broadly categorized as follows: (1) shear-induced, (2) volumetric-induced, and (3) ejecta-induced. In the first test series (referred to as the Baseline test hereafter), all these three components were realistically reproduced, while in the second test series (referred to as the Helical Pile test hereafter) the volumetric and ejecta-induced mechanisms were mainly mitigated, resulting in significant reductions in the foundation settlement. Results from the first test series (i.e., Baseline test) indicated that the flow velocity due to the hydraulic transient gradient displayed an upward flow in the loose layer, which explains the observed sand ejecta. This series of shake table tests resulted in an average total foundation settlement of 28 cm and 42.7 cm during two shaking sequences. The measured foundation settlements were compared to the estimated foundation settlement obtained from Liu and Dobry [1997] and Bray and Macedo’s [2017] simplified procedures. The observed foundation settlements generally were higher than the estimated values. In the second large-scale test series, an identical test setup to the first test series was used except for a group of four helical piles were attached to the shallow foundation to mitigate liquefaction-induced settlements. In this series of tests, a reduced excess pore-water pressure generation around the group of helical piles was observed and is mainly attributed to the increased relative density around their zone of influence as a result of installation. The foundation supported on helical piles underwent almost no differential settlement and tilt. A significant reduction in the total foundation settlement was achieved during the Helical Pile test series compared to the Baseline test series. This shake table project is the first experimental study that reproduced all the key mechanisms mentioned above including the effects of sediment ejecta, which have not been captured in prior experimental studies. In addition, this series of large-scale shake table tests provides a unique benchmark for the calibration of numerical models and simplified procedures to reliably estimate liquefaction-induced building settlements. Although this study introduced helical piles as a reliable and highly efficient measure to mitigate liquefaction-induced foundation tilt and settlement, the proper design nd application of helical piles in seismic areas still need thorough investigation due to possible amplified superstructure response.

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Section: Shake Table Experimental Programmentioning

confidence: 99%

Section: Shake Table Experimental Programmentioning

confidence: 99%

Section: Model Ground Preparation and Instrumentationmentioning

confidence: 99%

Section: Helical Piles Specifications and Instrumentationmentioning

confidence: 99%

See 2 more Smart Citations

Shake Table Tests on a Shallow Foundation on Liquefiable Soils Supported on Helical Piles

Orang¹,

Motamed²

2021

PEER Reports

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“…The soil models can be tested in ‘1 g’ conditions and constructed at small or medium scales (e.g. Iai, 1989; Jahed Orang et al, 2021; Nakashima et al, 2018; Yamazoe et al, 2018) or tested in a geotechnical centrifuge at ‘N × g’ where the stresses within reduced scale models are increased by the centrifugal acceleration to accurately capture the stress–strain behaviour of the full scale case at homologous points in the model (Garnier et al, 2007; Schofield, 1980). Such testing has revealed the significant change to soil stiffness due to densification and locked-in stresses of the soil skeleton (e.g.…”

Section: Introductionmentioning

confidence: 99%

Experimentally investigating the influence of changing payload stiffness on outer loop iterative learning control strategies with shaking table tests

Madabhushi

Hruby

Wham

2023

Journal of Vibration and Control

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Shaking tables are widely used across numerous engineering research and industrial sectors, including mechanical (e.g. automotive and aerospace testing), electrical (e.g. instrumentation testing) and civil (e.g. structural and geotechnical testing) engineering. It is commonly required to replicate the shake table motions accurately and precisely. Iterative learning control algorithms can be used to complement traditional proportional–integral–differential feedback control algorithms to optimize drive signals using a test payload prior to the real experiment. Historically, the design of these test payloads has focused on matching the mass of the actual payload and neglected its dynamic response. In this study, experimental results from shake table tests using multiple geotechnical containers with dry and saturated beds that exhibit a range of stiffnesses and material damping when shaken are presented. Errors between the demanded and achieved motions are explored and compared to the changing secant stiffness abstracted from the dynamic shear stress–strain loops of the payload. A clear trend emerges that demonstrates increased errors as the payload stiffness deviates from the constant stiffness test payload originally used with the open loop iterative learning control, and further the errors are not necessarily bounded by test payloads significantly softer or stiffer than the actual specimen. The findings support that in cases where repeatable, accurate and precise shake table motions are required for payloads that exhibit a complex material response that is not readily modelled mathematically, it may be necessary to reproduce the specimen’s overall dynamic response during the iterative learning control process.

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Evaluation and Opportunities for Soil Liquefaction Vulnerability Research: Lesson Learned from Japan for Indonesia - A Bibliometric Analysis

Fitri,

Sawada

2024

Springer Series in Geomechanics and Geoengineering

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Large-Scale Shake Table Tests on a Shallow Foundation in Liquefiable Soils

Cited by 22 publications

References 48 publications

Shake Table Tests on a Shallow Foundation on Liquefiable Soils Supported on Helical Piles

Shake Table Tests on a Shallow Foundation on Liquefiable Soils Supported on Helical Piles

Experimentally investigating the influence of changing payload stiffness on outer loop iterative learning control strategies with shaking table tests

Evaluation and Opportunities for Soil Liquefaction Vulnerability Research: Lesson Learned from Japan for Indonesia - A Bibliometric Analysis

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