helical pile shaft | ScienceGate

This work examined a new method of bi-directional static load testing for piles, referencing the Osterberg test. Measurements were taken, on a laboratory scale, using six models of piles driven into a box filled with sand. This method allowed for separate measurements of pile base and pile shaft bearing capacities. Based on the results, the total pile bearing capacity and equivalent Q–s diagrams were estimated. The results obtained show that the structure of the equivalent curve according to Osterberg is a good approximation of the standard Q–s curve obtained from load tests, except for loads close to the limit of bearing capacity (those estimates are also complicated by the inapplicability and ambiguity of a definition of the notion of limit bearing capacity); the equivalent pile capacity in the Osterberg method represents, on average, about 80% of the capacity from standard tests.

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Evolution of local friction along a model pile shaft in a calibration chamber for a large number of loading cycles

Comptes Rendus Mécanique ◽

10.1016/j.crme.2012.11.012 ◽

2013 ◽

Vol 341 (6) ◽

pp. 499-507 ◽

Cited By ~ 14

Author(s):

Hadj Bekki ◽

Jean Canou ◽

Brahim Tali ◽

Jean-Claude Dupla ◽

Ali Bouafia

Keyword(s):

Pile Shaft ◽

Model Pile ◽

Calibration Chamber

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Dynamic soil parameters and Case damping for high-capacity long H-piles

Canadian Geotechnical Journal ◽

10.1139/t11-064 ◽

2011 ◽

Vol 48 (11) ◽

pp. 1616-1629

Author(s):

Arthur K.O. So ◽

Charles W.W. Ng

Keyword(s):

Load Transfer ◽

High Capacity ◽

Transfer Mechanism ◽

Damping Factor ◽

Viscous Damping ◽

Soil Response ◽

Pile Shaft ◽

Load Transfer Mechanism ◽

Set Up ◽

Matching Techniques

Uncertainty exists in signal-matching techniques. The quake and damping obtained may not be the actual response of the soil. In this paper, the final sets, strain gauge readings, pile driving analyzer, and Case pile wave analysis program of 12 high-capacity long H-piles at the end of initial driving as well as two of them at restrike are studied. Measured and deduced data show that the soil response underneath the pile toes has limited movement and yielding despite the piles being set using very heavy hammer rams and large ram drops. The quake and damping decrease with increased shearing strain and shearing stress, but are influenced by pile whipping, rebounded stress wave, and load-transfer mechanism. The lumped Case damping factor decreases with increased side resistance to total resistance ratio. This factor can decrease or increase with time due to changes in the load-transfer mechanism after set-up, thus affecting the proportion of viscous damping of soil along the pile shaft and at the pile toe. A Case damping model is proposed that approximates the lumped Case damping factor as the sum of hysteretic damping of the pile and viscous damping of the surrounding soil. The effects of variation in load distribution and set-up along the pile shaft in layered soils and incomplete mobilization of soil at the pile toe on the Case damping factors are explained.

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Estimating Inelastic Displacements for Design: Extended Pile-Shaft-Supported Bridge Structures

Earthquake Spectra ◽

10.1193/1.1811613 ◽

2004 ◽

Vol 20 (4) ◽

pp. 1081-1094 ◽

Cited By ~ 4

Author(s):

T. C. Hutchinson ◽

Y. H. Chai ◽

R. W. Boulanger ◽

I. M. Idriss

Keyword(s):

Numerical Study ◽

Accurate Estimation ◽

Displacement Estimation ◽

Displacement Ductility ◽

Inelastic Displacement ◽

Pile Shaft ◽

Alternative Approach ◽

Bridge Structures ◽

The Mean ◽

Extended Pile Shaft

Accurate estimation of inelastic displacements is important for the evaluation of the seismic performance of structures with desired ductile response. In this paper, nonlinear dynamic analyses results from a companion numerical study investigating the response of ductile-designed bridge structures, were compared with a commonly applied inelastic displacement estimation approach and an alternative approach. The extended pile-shaft-supported bridge structures considered are susceptible to amplified response under long-period velocity pulses, and hence an evaluation of design methods for estimating inelastic displacement demands is warranted. In this case, force-reduction–displacement-ductility–period (R−μΔ−T) relations and a mean spectral displacement approach are investigated. The alternative approach estimates inelastic displacement demand using the mean elastic spectral displacement between two spectral periods that are important for the structure's response. Results support the conceptual merits of using the mean spectral displacement method, indicating that the approach is capable of reducing the uncertainty in predicting inelastic displacement demands for the types of structures considered when subjected to near-fault ground motions.

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The Influence of Anchor Inclination on Pull-out Resistance of Clays

Canadian Geotechnical Journal ◽

10.1139/t73-063 ◽

1973 ◽

Vol 10 (4) ◽

pp. 664-669 ◽

Cited By ~ 2

Author(s):

T. H. Hanna

Keyword(s):

Shear Stress ◽

Theoretical Model ◽

Stress State ◽

In Situ Stress ◽

Stiff Clays ◽

Pile Shaft ◽

Pull Out

A theoretical model is described that was used to examine the influence of anchor inclination on pull-out capacity. Use was made of previous general findings for pile shaft adhesion prediction in stiff clays. It is shown that the adhesion available at the anchor shaft – clay interface depends on: (1) the in situ stress state in the ground; (2) anchor inclination; and (3) the initial shear stress existing in the ground in the direction of the anchor shaft. The possible importance of the reported trends is considered.

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Grain-scale DEM study of open-ended pipe pile penetration in granular soils

EPJ Web of Conferences ◽

10.1051/epjconf/202124911007 ◽

2021 ◽

Vol 249 ◽

pp. 11007

Author(s):

Michail Komodromos ◽

Gaël Combe ◽

Gioacchino Viggiani

Keyword(s):

Distinct Element ◽

Horizontal Stress ◽

Granular Soils ◽

Pipe Pile ◽

Pile Shaft ◽

Offshore Engineering ◽

Pile Penetration ◽

Penetration Tests ◽

Shed Light ◽

Number Of Particles

Open-Ended Pipe Piles (OEPP) are particularly popular in oﬀshore engineering. An important feature of the installation of these piles is the rate with which soil enters the pile from the bottom, and its interaction with the internal pile shaft. The response of OEPP crucially depends on the occurrence of soil plugging, which can make the behavior of an OEPP similar to a pile of solid cross section. Plugging is generally attributed to arching eﬀects in the soil; therefore, understanding this phenomenon requires an investigation at the grain scale. This is precisely the objective of this study, where the Distinct Element Method (DEM) is used to study the installation of an Open-Ended Pipe Pile in a Virtual Calibration Chamber comprising 128000 grains, under constant horizontal stress. Despite the relatively small number of particles, this numerical model is found to be able to reproduce several aspects of the mechanisms actually observed in thefield. The results are compared to those obtained from actual experiments of miniature pile penetration tests. Stress and strainfields that develop in the soil inside and outside the pile provide interesting data and shed light on the mechanisms at play during OEPP installation, especially as for the influence of grains interlocking.

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