Critical Depth: How It Came Into Being and Why It Does Not Exist.

Fellenius, Bengt H.; Altaee, Ameir

doi:10.1680/igeng.1995.27590

Cited by 34 publications

(15 citation statements)

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“…Perhaps more important, the CFEM ranges are derived from piles usually much longer than 6 m, for which the shallow-depth influence of apparent overconsolidation (explained by principles of steady-state soil mechanics) is small. Therefore, it would be expected that the β coefficient would be larger near the ground surface rather than at a deeper depth (Fellenius and Atlaee 1995). Of course, in the case of a driven pile, one must consider that the driving may have created an annulus between the pile and the soil near the ground surface.…”

Section: Analysis Using Effective Stress-shaft Resistancementioning

confidence: 99%

Analysis of piles in a residual soil—The ISC'2 prediction

Fellenius¹,

Santos²,

Fonseca³

2007

Can. Geotech. J.

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The 2nd International Conference on Site Characterization (ISC'2), held in 2004, included a seminar for prediction of pile capacity involving three 6 m embedment length test piles, one 350 mm square driven concrete pile, and two 600 mm diameter, strain-gage instrumented, bored piles. Invited predictors were provided with results of in situ, laboratory tests and dynamic tests. Test layout, soil information, and pile data are presented with calculations of pile capacity and load distribution, submitted predictions, and results of the static loading tests. The CPT-calculated capacities show considerable scatter-total values ranged from 500 to 1400 kN for the driven pile and from 1000 to 1900 kN for the bored piles. The static loading test on the driven pile showed an offset limit load of 1200 kN and a plunging capacity of 1500 kN. Despite pile movements of 100 mm for 1200 kN of applied load, neither of the bored piles showed signs of having reached an ultimate resistance value. Effective stress analysis of strain measurements for the bored piles showed the data to correlate to a β coefficient of 1.0 and a toe coefficient of 16. Most submitted predictions underestimated the capacity of the driven pile and overestimated the capacities of the bored piles.

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Section: Analysis Using Effective Stress-shaft Resistancementioning

confidence: 99%

Analysis of piles in a residual soil—The ISC'2 prediction

Fellenius¹,

Santos²,

Fonseca³

2007

Can. Geotech. J.

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“…At the end of each jacking stroke, in particular, after the last jacking stroke, the pile-soil interaction reached a static equilibrium with the recovery of elastic compression caused by compression/tension pulses during jacking. There are still some residual forces locked in the piles and these are always compressive at the pile toe [37]. The magnitude and distribution of locked residual forces in the piles after installation have significant effects on the interpretation of loading transfer, and then end and shaft resistances [38,39].…”

Section: Test Resultis and Discussionmentioning

confidence: 99%

Field Performance of Open-Ended Prestressed High-Strength Concrete Pipe Piles Jacked into Clay

Kou

Diao

Liu

et al. 2018

Sensors

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The behavior of open-ended pipe piles is different from that of closed-ended pipe piles due to the soil plugging effect. In this study, a series of field tests were conducted to investigate the behavior of open-ended prestressed high-strength concrete (PHC) pipe piles installed into clay. Two open-ended PHC pipe piles were instrumented with Fiber Bragg Grating (FBG) sensors and jacked into clay for subsequent static loading tests. Soil plug length of the test piles was continuously measured during installation, allowing for calculation of the incremental filling ratio. The recorded data in static loading test were reported and analyzed. The distribution of residual forces after installation and the effect on the bearing capacity were also discussed in detail. The test piles were observed to be in partially plugged condition during installation. The measured ultimate shaft resistance and total resistance of the test piles were 639 and 1180 kN, respectively. The residual forces locked in the test piles after installation significantly affected the evaluation of the axial forces, and thus the shaft and end resistances. It tended to underestimate the end resistances and overestimate the shaft resistances if the residual forces were not considered in the loading test. However, the residual forces did not affect the total bearing capacity of open-ended PHC pipe piles in this study.

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“…11B shows the "true distribution" curve, which combines the residual load and test applied loads, and the "false distribution", which appears when the residual load is neglected. Published case histories on results of loading tests on instrumented piles have frequently neglected to include residual load, which has given rise to fallacies such as the "critical depth" (Fellenius and Altaee 1995).…”

Section: Pile Capacity and Residual Loadmentioning

confidence: 99%

Unified Design of Piled Foundations with Emphasis on Settlement Analysis

Fellenius¹

2004

Current Practices and Future Trends in Deep Foundations

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Design of a piled foundation rarely includes a settlement analysis and is usually limited to determining that the factor of safety on pile capacity is equal to an at least value. This approach is uneconomical and, sometimes, unsafe. Every design of a piled foundation should establish the resistance distribution along the pile, determine the location of the force equilibrium (the neutral plane), estimate the magnitude of dragload from accumulated negative skin friction at the neutral plane, evaluate the length of the zone where the shear forces change from negative to positive direction, establish the load-movement relation for the pile toe and the load distribution in the pile at the time that settlement becomes an issue for the design, and, finally, perform a settlement analysis. The settlement analysis of a piled foundation must distinguish between settlement due to movements caused by external load on the piles and settlement due to causes other than the load on the piles. A fundamental realization of such design approach is that pile toe capacity is a misconception. Each of the mentioned points is addressed in the paper, and a design approach for the design of piled foundations and piled rafts is presented. Examples and case histories are included showing the distribution of measured and calculated resistance distribution along the piles and settlement of soil and piles.

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Critical Depth: How It Came Into Being and Why It Does Not Exist.

Cited by 34 publications

References 0 publications

Analysis of piles in a residual soil—The ISC'2 prediction

Analysis of piles in a residual soil—The ISC'2 prediction

Field Performance of Open-Ended Prestressed High-Strength Concrete Pipe Piles Jacked into Clay

Unified Design of Piled Foundations with Emphasis on Settlement Analysis

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