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

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.

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STUDY ON THE USE OF SWELLING PAINT AS A MEASURE TO REDUCE NEGATIVE SKIN FRICTION : Part 1 Material characteristics

Journal of Structural and Construction Engineering (Transactions of AIJ) ◽

10.3130/aijsx.443.0_87 ◽

1993 ◽

Vol 443 (0) ◽

pp. 87-94

Author(s):

Kazuhiro KAWABE ◽

Akira ENAMI

Keyword(s):

Skin Friction ◽

Negative Skin Friction ◽

Material Characteristics

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

Canadian Geotechnical Journal ◽

10.1139/t72-014 ◽

1972 ◽

Vol 9 (2) ◽

pp. 127-136 ◽

Cited By ~ 28

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.

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