Seismic Bearing Capacity of Piles in Liquefiable Soils

Knappett, Jonathan; Madabhushi, Spg

doi:10.3208/sandf.49.525

Cited by 25 publications

(9 citation statements)

References 20 publications

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“…Equations ( 13) and ( 15) have been widely used in bridge engineering design in China, considering the influence of factors such as velocity and sediment movement at the bottom of the river bed on the erosion depth, and have the advantage of high stability of the calculation results [27]. However, the left and right dimensions are not uniform, the calculation is more complicated, and there are many related parameters that need engineering experience to evaluate.…”

Section: Local Scour Calculationmentioning

confidence: 99%

Study on the Influence of Water Erosion on the Bearing Capacity and Function of the High Pile Foundation of the Wharf

Yang,

Zhang,

et al. 2024

Water

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High-pile foundation is a common form of deep foundation commonly used in ocean environments, such as docks and bridge sites. Aiming at the problem of bearing capacity of high pile foundations, this paper proposes the calculation of bearing capacity and the analysis of scour depth of high pile foundations under the action of scour based on the modified p-y curve. In this paper, three kinds of scour mechanisms—natural evolution scour, general scour, and local scour—are described; and the calculation methods of scour widely used at present are compared and analyzed. The solution of the vertical stress of soil around the pile under local scour is solved and applied to the β method to solve the lateral resistance of the pile under local scour. The local erosion is equivalent to the whole erosion, and the expression of the ultimate soil resistance before and after the equivalent is calculated, respectively, according to the principle that the ultimate soil resistance at a certain point above the equivalent pile end remains unchanged. The distance from the equivalent soil surface to the pile end can be obtained simultaneously, and then the equivalent erosion depth, p-y curve of sand at different depths, and high pile bearing capacity can be obtained. Finally, it is found that the bending moment of a single pile body varies along the pile body in the form of a parabola, and the maximum bending moment of the pile body is below the mud surface and increases with the increase in horizontal load. When the scouring depth is 30 m, the horizontal load is 25 KN, and the maximum bending moment of the pile body is about 150 N·m. The data with a relative error greater than 10% accounted for only 16.6% of the total data, and the error between the calculated value and the measured value was small. The formula can predict the erosion depth more accurately.

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Section: Local Scour Calculationmentioning

confidence: 99%

Study on the Influence of Water Erosion on the Bearing Capacity and Function of the High Pile Foundation of the Wharf

Yang,

Zhang,

et al. 2024

Water

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“…During reconsolidation, any settlement at the tip affects the development of drag load. Knappett and Madabhushi (2009) used load measurements from a series of centrifuge tests on piles in liquefiable soils and proposed an empirical model [Eq. ( 2)] to estimate the ultimate pile tip capacity in liquefying soil (q r u t;ult ) as a nonlinear function of the free-field excess pore pressure ratio (r u ) at a depth of the pile's tip…”

Section: Qzliq Materials Propertiesmentioning

confidence: 99%

“…where q o t;ult = ultimate tip capacity when r u ¼ 0; and the α t = material constant, which, according to the empirical model of Knappett and Madabhushi (2009), only depends on the effective friction angle (ϕ 0 ) of the soil at the tip. Sinha (2022) performed several centrifuge tests on axially loaded piles in liquefiable soils and found a very good agreement with the previously proposed model [as defined in Eq.…”

Section: Qzliq Materials Propertiesmentioning

confidence: 99%

Numerical Modeling of Liquefaction-Induced Downdrag: Validation against Centrifuge Model Tests

Sinha

Ziotopoulou

Kutter

2022

J. Geotech. Geoenviron. Eng.

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Earthquake-induced soil liquefaction can cause soil settlement around piles, resulting in drag load and pile settlement after shaking stops. Estimating the axial load distribution and pile settlement is important for designing and evaluating the performance of axially loaded piles in liquefiable soils. Commonly used neutral plane solution methods model the liquefiable layer as an equivalent consolidating clay layer without considering the sequencing and pattern of excess pore pressure dissipation and soil settlement. Moreover, changes in the pile shaft and the tip resistance due to excess pore pressures are ignored. A TzQzLiq numerical model was developed using the existing TzLiq material and the new QzLiq material for modeling liquefaction-induced downdrag on piles. The model accounts for the change in the pile's shaft and tip capacity as free-field excess pore pressures develop or dissipate in soil. The developed numerical model was validated against data from a series of large centrifuge model tests, and the procedure for obtaining the necessary information and data from those is described. Additionally, a sensitivity study on TzLiq and QzLiq material properties was performed to study their effect on the developed drag load and pile settlement. Analysis results show that the proposed numerical model can reasonably predict the time histories of axial load distribution and settlement of axially loaded piles in liquefiable soils both during and postshaking.

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“…Coelho et al (2004) performed dynamic centrifuge tests on uniform deposits of saturated sands and showed that the mechanisms of excess pore pressure generation and liquefaction are similar in dense and loose sand, with the rate of excess pore pressure generation being slower in dense sand. Centrifuge tests of pile groups by Knappett and Madabhushi (2009) and Madabhushi (2010, 2013) observed substantial settlements of piles during shaking when the excess pore pressures were high around the shaft and near the tip. After shaking, as soil reconsolidated and drag load developed, the resulting settlement in the piles was much smaller.…”

Section: Introductionmentioning

confidence: 99%

Centrifuge Model Tests of Liquefaction-Induced Downdrag on Piles in Uniform Liquefiable Deposits

Sinha

Ziotopoulou

Kutter

2022

J. Geotech. Geoenviron. Eng.

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Earthquake-induced soil liquefaction can cause settlement around piles, which can translate to negative skin friction and the development of drag load and settlement of the piles. A series of centrifuge model tests were performed to assess liquefaction-induced downdrag and understand the interplay and effects of (1) pile embedment and pile-head load, (2) excess pore pressure generation and dissipation, and (3) reconsolidation and ground settlement on pile response during and postshaking. The model included a layered soil profile (clay, liquefiable sand, and dense sand) with two 635-mm-diameter instrumented piles. One pile was placed with its tip at the bottom of the liquefiable deposit; the other pile was embedded five diameters into the dense sand layer. The model was shaken with multiple earthquake motions with their peak horizontal accelerations ranging from 0.025 to 0.4 g. For each shaking event, the drag load on the piles first decreased during shaking and then increased during reconsolidation, exceeding its preshaking value. With multiple shaking events, the net drag load on the piles increased. The maximum observed drag load was found equal to the drained interface shear strength calculated from the interface friction angle of δ ¼ 30°and a lateral stress coefficient of K ¼ 1. Larger drag loads and smaller settlements were observed for the pile embedded deep in the dense sand layer. Most of the pile settlements occurred during shaking; postshaking pile settlement was less than 2% of the pile's diameter. The mechanisms behind the development of liquefaction-induced drag load on piles and settlements are described. Select ramifications concerning the design of piles in liquefiable soils are also described.

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Seismic Bearing Capacity of Piles in Liquefiable Soils

Cited by 25 publications

References 20 publications

Study on the Influence of Water Erosion on the Bearing Capacity and Function of the High Pile Foundation of the Wharf

Study on the Influence of Water Erosion on the Bearing Capacity and Function of the High Pile Foundation of the Wharf

Numerical Modeling of Liquefaction-Induced Downdrag: Validation against Centrifuge Model Tests

Centrifuge Model Tests of Liquefaction-Induced Downdrag on Piles in Uniform Liquefiable Deposits

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