Development of negative skin friction on driven piles in soft Bangkok clay

1992 ◽  
Vol 29 (3) ◽  
pp. 393-404 ◽  
Author(s):  
B. Indraratna ◽  
A. S. Balasubramaniam ◽  
P. Phamvan ◽  
Y. K. Wong
Keyword(s):  
Skin Friction ◽  
Prestressed Concrete ◽  
Load Transfer ◽  
Soft Clay ◽  
Driven Piles ◽  
Short Term ◽  
Negative Skin Friction ◽  
Pullout Tests ◽  
Pore Pressures

This paper describes the results of short-term pullout tests and long-term full-scale measurements of negative skin friction on driven piles in Bangkok subsoils. Two instrumented cylindrical (hollow) prestressed concrete piles were fully equipped with two independent load-measurement systems, load cells, and telltale rods. Pore pressures and ground movements in the vicinity of the piles were monitored throughout the period of investigation. The effect of bitumen coating on negative skin friction was also studied. The long-term behaviour of driven piles was compared with the estimated values obtained from short-term pullout tests and soil strength data. It was found that the negative skin friction can be predicted well by the effective stress approach using values of β between 0.1 and 0.2. The load–settlement and load–transfer behaviour were numerically modelled to acquire a more comprehensive understanding of negative skin friction developed on driven piles. A settlement-controlled concept is also introduced for piles subjected to negative skin friction, on the basis of these findings. Key words : consolidation, downdrag, driven pile, embankment, finite elements, pore pressures, pullout, settlements, soft clay.

scholarly journals Downdrag Measurements on a 160-Ft Floating Pipe Test Pile in Marine Clay

1972 ◽  
Vol 9 (2) ◽  
pp. 127-136 ◽  
Author(s):  
M. Bozozuk
Keyword(s):  
Skin Friction ◽  
Compressive Load ◽  
Marine Clay ◽  
Positive Skin ◽  
Negative Skin Friction ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Test Pile ◽  
Excess Pore

Large negative skin friction loads were observed on a 160 ft (49 m) steel pipe test pile floating in marine clay. The test pile was driven, open-ended, on the centerline of a 30 ft (9 m) high granular approach fill on the Quebec Autoroute near Berthierville. Since the installation was made in 1966 the fill has settled 21 in. (53 cm), dragging the pile down with it. Negative skin friction acting along the upper surface of the pile was resisted by positive skin friction acting along the lower end as it penetrated the underlying clay. Under these conditions the pile compressed about [Formula: see text] (2 cm). Analysis of the axial strains indicated that a peak compressive load of 140 t developed at the inflection point between negative and positive skin friction 73 ft (22 m) below the top of the pile. Negative and positive skin friction acting on the upper surface of the pile exceeded the in situ shear strength and approached the drained strength of the soil where excess pore water pressures had dissipated. At the lower end where the positive excess pore pressures were high and relative movement between the pile and the soil was large, the positive skin friction approached the remoulded strength as measured with the field vane. Skin friction was increasing, however, as positive escess pore pressures dissipated.This paper shows that skin friction loads are related to the combination of (a) in situ horizontal effective stresses, (b) horizontal stresses due to embankment loads, and (c) horizontal stresses due to differential settlement of the fill.

Development of negative skin friction on driven piles in soft Bangkok clay: Reply

1993 ◽  
Vol 30 (5) ◽  
pp. 887-888 ◽  
Author(s):  
B. Indraratna
Keyword(s):  
Skin Friction ◽  
Driven Piles ◽  
Negative Skin Friction

Development of negative skin friction on single piles: uncoupled analysis based on nonlinear consolidation theory with finite strain and the load-transfer method

2011 ◽  
Vol 48 (6) ◽  
pp. 905-914 ◽  
Author(s):  
Hyeong-Joo Kim ◽  
Jose Leo C. Mission
Keyword(s):  
Skin Friction ◽  
Effective Stress ◽  
Finite Strain ◽  
Load Transfer ◽  
Negative Skin Friction ◽  
Consolidation Theory ◽  
Single Piles ◽  
Transfer Method ◽  
Load Transfer Method ◽  
Nonlinear Consolidation

The development of negative skin friction (NSF) on single piles is investigated based on an uncoupled method of analysis with the Mikasa (1963) generalized nonlinear consolidation theory in terms of finite strain and the nonlinear load-transfer method. Predicted results are compared with results based on the conventional linear consolidation theory with infinitesimal strains. It is found that predicted development of dragload using the conventional consolidation theory is slightly greater and conservative compared to that using the nonlinear consolidation theory based on effective stress (β method). Effective stress predictions using the conventional theory are larger due to the faster dissipation of excess pore pressures, with the assumption of constant coefficient of consolidation and permeability. However, since the relative displacements required to mobilize the ultimate skin friction are small, and piles are usually installed near the final stages of soil consolidation, the differences in the predictions for the development of dragload on piles between the two consolidation theories are overshadowed. Using the uncoupled model for pile NSF, it is therefore found that the most significant factor for the estimation of dragload and downdrag is the proper selection of the β value rather than the consolidation theory used.

Drag load on end-bearing piles in collapsible soil due to inundation

2016 ◽  
Vol 53 (12) ◽  
pp. 2030-2038 ◽  
Author(s):  
Ibrahim Mashhour ◽  
Adel Hanna
Keyword(s):  
Experimental Investigation ◽  
Skin Friction ◽  
Soft Clay ◽  
Soil Layer ◽  
Design Procedure ◽  
Collapsible Soil ◽  
Negative Skin Friction ◽  
Collapsible Soils ◽  
Surrounding Soil ◽  
End Bearing Pile

Collapsible soils may experience sudden and excessive settlement when inundated. The use of pile foundations that penetrate the collapsible soil layer to reach a firm stratum is widely used in practice. However, when the ground is inundated, large and sudden settlement of the surrounding soil may take place, causing negative skin friction on the pile’s shaft, which may lead to catastrophic failure. In the literature, research dealing with negative skin friction for piles in collapsible soil is lagging due to the complexity of modeling collapsible soil analytically. Alternatively, results of sophisticated experimental investigation may produce valuable information to predict the negative skin friction and accordingly the drag load on these piles. This paper presents the results of an experimental investigation on a single end-bearing pile in collapsible soil. The investigation is tailored to measure the soil collapse before and during inundation and the associated drag load on the pile. The theory proposed by Hanna and Sharif in 2006 for predicting negative skin friction on piles due to consolidation of the surrounding soft clay was extended to predict the negative skin friction for these piles in collapsible soils. A proposed design procedure is presented.

Effect of Skirt-Tip Geometry on Set-Up Outside Suction Anchors in Soft Clay

2004 ◽  
Author(s):  
Knut H. Andersen ◽  
Lars Andresen ◽  
Hans Petter Jostad ◽  
Edward C. Clukey
Keyword(s):  
Shear Strength ◽  
Skin Friction ◽  
Soft Clay ◽  
Wall Roughness ◽  
Driven Piles ◽  
The Mean ◽  
Set Up ◽  
Anchor Design ◽  
The Impact

An important part of suction anchor design is the determination of the shear strength along the outside skirt wall. Previous work has suggested that when a suction anchor in clay is installed by applying underpressure inside the anchor, the external skin friction may be reduced compared to the skin friction expected for driven piles. The primary reason for this reduction is that the movement of soil at and beneath the caisson tip during installation will be influenced by whether the anchor is penetrated by weight or by underpressure. To further investigate the impact of installation by underpressure, additional finite element analyses have been performed where the skirt installation process has been better followed than in the previous analyses. The movement of soil around the caisson wall was studied for both a flat caisson tip and a tip with a tapered edge of 45° towards the outside of the anchor. The tapering was made to see if it would cause more of the displaced soil to move outside the anchor and thereby increase the mean total stresses and the shear strength along the outside anchor wall. The analyses were made with two separate wall roughness factors for a typical anchor in soft clay.

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