Set-up of pile shaft friction in laboratory chamber tests

2014 ◽  
Vol 14 (2) ◽  
pp. 21-30 ◽  
Author(s):  
Jit Kheng Lim ◽  
Barry M. Lehane
Keyword(s):  
Pile Shaft ◽  
Set Up ◽  
Shaft Friction

scholarly journals Evaluation of installation effects on set-up of field displacement piles in sand

2019 ◽  
Vol 56 (4) ◽  
pp. 461-472 ◽  
Author(s):  
Ivana Anusic ◽  
Barry M. Lehane ◽  
Gudmund R. Eiksund ◽  
Morten A. Liingaard
Keyword(s):  
Test Data ◽  
Impact Frequency ◽  
Short Term ◽  
Factors Affecting ◽  
Installation Effects ◽  
Field Displacement ◽  
Small Influence ◽  
Set Up ◽  
Shaft Friction

The paper presents results from a new series of tests on displacement piles in sand, involving different installation modes, and combines these with results from previous tests at the same site as well as with test data at two other well-investigated sand sites to provide fresh insights into factors affecting “short-term” capacity and set-up of shaft friction. It is shown that the shaft capacity measured shortly after installation reduces systematically with the logarithm of the number of impact blows or jacking increments per unit shaft area imparted during installation. However, the degree of set-up of shaft friction for piles increases with an increase in the number of blows, and piles installed using a large number of blows can attain highest “long-term” shaft capacities, despite having the lowest short-term capacity. The tests indicated that the driving impact frequency had a relatively small influence on shaft friction, while piles installed by vibration attain short-term capacities comparable to driven impact piles, but showed negative set-up.

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

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.

An Analysis of Pile-Soil Interaction under Embankment Load

2014 ◽  
Vol 488-489 ◽  
pp. 458-461 ◽  
Author(s):  
Min Zhao ◽  
Wei Ping Cao
Keyword(s):  
Skin Friction ◽  
Axial Force ◽  
Complex Interaction ◽  
Neutral Plane ◽  
Consolidation Process ◽  
Pile Shaft ◽  
3D Numerical Model ◽  
Set Up ◽  
Embankment Load ◽  
Surrounding Soil

The complex interaction between the pile and surrounding soil significantly affects the behavior of the piled reinforced embankment. In this paper, a 3D numerical model of piled reinforced embankment was set up to explore the development of the settlement of the pile and the surrounding soft soils during the embankment filling as well as the subsequent consolidation of the soil. The evolution of the pile axial force, the skin friction and the neutral plane depth was also studied. The results show that the settlement of the pile and surrounding soil, the pile axial force, the skin friction along the pile shaft and the neutral plane depth during the embankment filling and the consolidation process experienced a complicated evolution.

Lateral stress changes and shaft friction for model displacement piles in sand

2005 ◽  
Vol 42 (4) ◽  
pp. 1039-1052 ◽  
Author(s):  
Barry M Lehane ◽  
David J White
Keyword(s):  
Shear Band ◽  
Effective Stress ◽  
Static Load ◽  
Lateral Stress ◽  
Interface Shear ◽  
Pile Installation ◽  
Pile Shaft ◽  
Centrifuge Tests ◽  
Stress Changes ◽  
Shaft Friction

The paper describes a series of tests performed in a drum centrifuge on instrumented model displacement piles in normally consolidated sand. These tests examined the influence of the pile installation method, the stress level, and the pile aspect ratio on the increase in lateral effective stress on the pile shaft during static load testing to failure. A parallel series of constant normal load and constant normal stiffness (CNS) laboratory interface shear experiments was performed to assist interpretation of the centrifuge tests. It is shown that although the cycling associated with pile installation results in a progressive reduction in the stationary horizontal effective stress acting on a pile shaft and densification of the sand in a shear band close to the pile shaft, this sand dilates strongly during subsequent shearing to failure in a static load test. The dilation (the amount of which depends on the cyclic history) is constrained by the surrounding soil and therefore leads to large increases in lateral effective stresses and hence to large increases in mobilized shaft friction. The increase in lateral stress is shown to be related to the radial stiffness of the soil mass constraining dilation of the shear band and to be consistent with measurements made in appropriate CNS interface shear tests. The paper's findings assist in the extrapolation of model-scale pile test results to full-scale conditions.Key words: sand, displacement pile, centrifuge tests, shaft friction.

Time effects on shaft capacity of jacked piles in sand

2015 ◽  
Vol 52 (11) ◽  
pp. 1830-1838 ◽  
Author(s):  
Jit Kheng Lim ◽  
Barry Lehane
Keyword(s):  
Effective Stress ◽  
Western Australia ◽  
Case History ◽  
Radial Stress ◽  
Experimental Program ◽  
Driven Piles ◽  
Time Effects ◽  
Set Up ◽  
Shaft Friction ◽  
Shaft Capacity

This paper examines the effects of time on the shaft capacity of jacked piles in sand through an experimental program performed at three separate test sites in Western Australia. A total of 18 instrumented pile tests were conducted to track the changes of radial stress on the pile shafts, as well as shaft friction, up to a maximum of 72 days after installation. The results confirm that the gains in shaft capacity of jacked piles are small after a period of about 1 day. This observation is in keeping with limited available case history data, but is in stark contrast to the significant capacity gains reported for driven piles. Further examination reveals that set-up effects for jacked piles in sand are relatively significant within one day of installation, and that the increased friction is associated primarily with larger increases in radial effective stress during shearing.

The Effects of Drying Techniques on Clay-Rich Soil Texture

1974 ◽  
Vol 32 ◽  
pp. 466-467
Author(s):  
T. G. Naymik
Keyword(s):  
Critical Point ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Drying Methods ◽  
Air Drying ◽  
Freeze Dried ◽  
Critical Point Drying ◽  
Set Up ◽  
The Relationship ◽  
Quartz Grains

Three techniques were incorporated for drying clay-rich specimens: air-drying, freeze-drying and critical point drying. In air-drying, the specimens were set out for several days to dry or were placed in an oven (80°F) for several hours. The freeze-dried specimens were frozen by immersion in liquid nitrogen or in isopentane at near liquid nitrogen temperature and then were immediately placed in the freeze-dry vacuum chamber. The critical point specimens were molded in agar immediately after sampling. When the agar had set up the dehydration series, water-alcohol-amyl acetate-CO2 was carried out. The objectives were to compare the fabric plasmas (clays and precipitates), fabricskeletons (quartz grains) and the relationship between them for each drying technique. The three drying methods are not only applicable to the study of treated soils, but can be incorporated into all SEM clay soil studies.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

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