Effects of installation disturbance on behavior of multi-helix piles in structured clays

Bagheri, Farnoosh; Naggar, M. Hesham El

doi:10.1179/1937525515y.0000000008

Cited by 42 publications

(8 citation statements)

References 21 publications

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“…Direct installation consequences, such as soil disturbance caused by the plates being cut and moved by the shaft, were not taken into consideration in this study. Such impacts are especially significant in sensitive soils, according to research by Weech and Howie [37] and Bagheri and El Naggar [38], which also demonstrated that decreasing the undrained shear strength to its residual value is reasonable. Consequently, if the undrained shear strength is assumed to be residual, installation effects will be taken into consideration in some way.…”

Section: Modeling Limitationsmentioning

confidence: 99%

Behavior of Mono Helical Pile Foundation in Clays under Combined Uplift and Lateral Loading Conditions

Vignesh

Muthukumar

2022

Applied Sciences

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Offshore wind energy development is driven by ongoing research and development to determine technological issues connected with offshore wind turbines. A fundamental design difficulty is the offshore wind turbine foundations. By far, one of the most commonly practiced foundation systems is mono helical pile foundations because of their simplicity and resilience. Most of the studies on mono helical piles were focused on granular soils and few studies were on clayey soils. However, mono helical piles in clayey soils under combined loading remain to be examined. Hence, a series of three-dimensional finite element analyses were carried out to predict the uplift and lateral capacity of the helical pile embedded in soft clay. The numerical model is verified using the results from the analytical results and a small-scale laboratory test. The verified model is used to simulate the helical pile behavior under the combined uplift and lateral loading condition considering the pile with a different number of helical plates. The results of the combined loading analyses reveal that the lateral capacity decreased when the pile was subjected to uplift load, and a maximum reduction of 12% is observed in mono helical piles provided with a single plate for an applied 50% of the ultimate uplift load. The influence of uplift load also increased the bending moment of the helical pile. Finally, it is suggested that the helical piles should be designed considering the aspects for combined loading conditions.

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Section: Modeling Limitationsmentioning

confidence: 99%

Behavior of Mono Helical Pile Foundation in Clays under Combined Uplift and Lateral Loading Conditions

Vignesh

Muthukumar

2022

Applied Sciences

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“…Cyclic degradation of saturated soil, such as soft clays, sensitive clays, silts, and loose sands, may substantially affect the seismic response of earth or ground‐structure systems 1–5 . Strength and stiffness degradation can be attributed to pore pressure build‐up 6–11 or changes in microstructural stability, for instance, quick/sensitive clays, 12–15 among other factors. As such, stiffness and strength degradation effects need to be adequately accounted for when evaluating the seismic performance of earth or ground‐structure systems.…”

Section: Introductionmentioning

confidence: 99%

A practical three‐dimensional plasticity model for cyclic degradation of soil in earthquake loading applications

Qiu

Prabhakaran

Zhou

et al. 2023

Earthq Engng Struct Dyn

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A practical yet realistic three‐dimensional (3D) constitutive model is presented for modeling the cyclic degradation behavior of soil. Such response can be attributed to pore pressure build‐up and loss of cementation, among other stiffness and strength degradation mechanisms. Extending an existing multi‐yield surface (MYS) plasticity formulation, the cyclic degradation model (CDM) is developed by incorporating a novel degradation logic in terms of accumulated plastic strain or as prescribed by the user. Thereafter, the CDM is implemented into a computational framework (OpenSees), and Finite Element (FE) calibrations are undertaken to match the available experimental data at the element and system levels. A generally good agreement between the FE simulations and centrifuge test data demonstrates the CDM's capabilities to simulate the seismic response of sloping sites. Using the calibrated model properties, full 3D FE simulations of a large‐scale multi‐span bridge configuration, motivated by details of an actual bridge system in sloping ground, are conducted to highlight the underlying response mechanisms. In addition, computed results including and precluding the effects of cyclic degradation are directly compared and discussed. It is shown that loss of soil strength and stiffness play a noticeable role in the resulting ground and bridge response. Overall, the newly developed constitutive model and findings are of importance for a wide range of soil formations where cyclic degradation occurs under earthquake loading.

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“…Moreover, the pile rotation may weaken the sand within the zone circumscribed by its helix creating a cylindrical failure surface around the pile (Vesic 1971). This effect is more pronounced for multi-helix and large diameter anchors (Bagheri and El Naggar 2013). Other drawbacks of helical piles include the potential for large displacement to fully mobilize the endbearing contributions of their plates, low buckling and lateral resistances of helical piles with slender shafts, and reduced rigidity at coupling joints for segmented helical piles (Vickars and Clemence 2000).…”

Section: Introductionmentioning

confidence: 99%

Optimization of grouting method and axial performance of pressure-grouted helical piles

Mansour

Naggar

2022

Can. Geotech. J.

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Pressure grouted helical pile (PGHP) is an innovative piling system that allows a significant increase in helical pile capacity with relatively low additional cost. The pile is constructed by applying pressurized grout during the installation of conventional helical piles. The grout is injected into the ground through two nozzles welded to the hollow pile shaft. This paper presents a comprehensive laboratory study to investigate the effect of three different nozzles configurations on the shape and axial performance of PGHP. The results reveal a significant increase in the PGHP shaft resistance over that of the un-grouted helical pile due to the formation of a continuous grout column with a larger diameter, higher friction angle at the pile/soil interface, and higher lateral earth pressure around the pile. The shape and diameter of the created grout column depend on the nozzles configuration used for grout injection. An increase in the end-bearing resistance is observed due to grout dissipation into the supporting soil voids. The study also shows that PGHPs installed with the third nozzles configuration have the fastest installation rate and the highest compression and pullout resistances. Thus, the third nozzles configuration is recommended for PGHP construction.

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Effects of installation disturbance on behavior of multi-helix piles in structured clays

Cited by 42 publications

References 21 publications

Behavior of Mono Helical Pile Foundation in Clays under Combined Uplift and Lateral Loading Conditions

Behavior of Mono Helical Pile Foundation in Clays under Combined Uplift and Lateral Loading Conditions

A practical three‐dimensional plasticity model for cyclic degradation of soil in earthquake loading applications

Optimization of grouting method and axial performance of pressure-grouted helical piles

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