An experimental evaluation of helical piles as a liquefaction-induced building settlement mitigation measure

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

doi:10.1016/j.soildyn.2021.106994

Cited by 12 publications

(6 citation statements)

References 47 publications

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“…Recent large-scale shake table test at the UCSD outdoor shake table facility [ElSawy et al 2019a]) and scaled 1g shake table test at UNR [Jahed Orang et al 2019b] shed light on the adequate performance of helical piles in dry sand. ElSawy et al [2019a, b] conducted a series of full-scale 1g shake table experiments using UCSD's large high-performance outdoor shake table (LHPOST) to evaluate the dynamic behavior of different helical piles with different shaft shape, length and size with variable top weights, and number of helices.…”

Section: Helical Pilesmentioning

confidence: 99%

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: Helical Pilesmentioning

confidence: 99%

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

Orang¹,

Motamed²

2021

PEER Reports

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“…Tunneling‐induced vertical and lateral movements of liquefiable sand are higher compared with the pure solid state of the soil. In addition, liquefaction phenomena of different ground conditions, including (a) soil with pile, (b) soil with a tunnel, (c) soil with a tunnel and pile, and (d) saturated soil with a tunnel of the sea bed, have been described by several authors based on various research methods such as numerical and analytical analyses, the centrifuge test, and the shaking table test (Finn & Fujita, 2002; Liyanapathirana & Poulos, 2002; Liyanathirana & Poulos, 2002; Orang et al, 2021; Taylor & Madabhushi, 2020; Wang et al, 2022; Yue et al, 2020; Zhao et al, 2021). Normally, liquefaction occurs due to seismic shaking, which impacts surface and underground structures.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear anisotropic finite element analysis of liquefiable tunnel–sand–pile interaction under seismic excitation

Haque

2023

Deep Underground Science and Engineering

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Nonlinear time‐history analysis can be used to determine the liquefiable behaviors of the tunnel–sand–pile interaction (TSPI) model with the consideration of sand anisotropy. This study presents the nonlinear response of the TSPI model with the existence of liquefaction under seismic excitation. The analysis reveals that tunnel and pile behave as isotropic elements, while sand shows isotropic, orthotropic, and anisotropic characteristics. Three constitutive models including UBC3D‐PLM (two yield surfaces associated with the hardening rule), NGI‐ADP (yielding with associated plastic potential function), and a user‐specified constitutive model are adopted to evaluate the isotropic, orthotropic, and anisotropic behaviors of sand. On this basis, two finite element‐based codes (ETABS 18.1.1 and Plaxis 3D) are used to evaluate sand behaviors and responses. Responses of the tunnel, sand, pile, and excess pore pressure ratio are recorded in the interaction zone by varying the pile diameter, tunnel diameter, and tunnel–pile clearance. Compared with the orthotropic and isotropic conditions, lower variations of results are found in the anisotropic condition, except for the case of generation of excess pore pressure. In addition, the present reanalysis results are in agreement with previous analytical and case study results, which further indicates the effectiveness of the finite element‐based numerical codes.

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“…Considerable studies have been performed to investigate the effect of different parameters on the behavior of piles/micropiles based on numerical approaches and experimental studies [ 23 , 26 , 27 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ]. The FOREVER (2003) [ 24 ] program also showed better performance of battered micropile-reinforced soil against liquefaction.…”

Section: Introductionmentioning

confidence: 99%

“…During the experiments, the generation of the pore water pressures is measured by pore pressure transducers installed at two different depths of soil and under horizontal base excitations. Relying on the obtained test results, also, comparing with the available cyclic tests [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ,…”

Section: Introductionmentioning

confidence: 99%

Liquefaction Potential of Saturated Sand Reinforced by Cement-Grouted Micropiles: An Evolutionary Approach Based on Shaking Table Tests

et al. 2023

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Cement-grouted injections are increasingly employed as a countermeasure material against liquefaction in active seismic areas; however, there is no methodology to thoroughly and directly evaluate the liquefaction potential of saturated sand materials reinforced by the cement grout-injected micropiles. To this end, first, a series of 1 g shaking table model tests are conducted. Time histories of pore water pressures, excess pore water pressure ratios (ru), and the number of required cycles (Npeak) to liquefy the soil are obtained and modified lower and upper boundaries are suggested for the potential of liquefaction of both pure and grout-reinforced sand. Next, adopting genetic programming and the least square method in the framework of the evolutionary polynomial regression technique, high-accuracy predictive equations are developed for the estimation of rumax. Based on the results of a three-dimensional, graphical, multiple-variable parametric (MVP) analysis, and introducing the concept of the critical, boundary inclination angle, the inclination of micropiles is shown to be more effective in view of liquefaction resistivity for loose sands. Due to a lower critical boundary inclination angle, the applicability range for inclining micropiles is narrower for the medium-dense sands. MVP analyses show that the effects of a decreasing spacing ratio on decreasing rumax are amplified while micropiles are inclined.

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An experimental evaluation of helical piles as a liquefaction-induced building settlement mitigation measure

Cited by 12 publications

References 47 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

Nonlinear anisotropic finite element analysis of liquefiable tunnel–sand–pile interaction under seismic excitation

Liquefaction Potential of Saturated Sand Reinforced by Cement-Grouted Micropiles: An Evolutionary Approach Based on Shaking Table Tests

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