Down-drag on Piles in Clay due to Negative Skin Friction

1972 ◽  
Vol 9 (4) ◽  
pp. 323-337 ◽  
Author(s):  
Bengt H. Fellenius
Keyword(s):  
Skin Friction ◽  
Soft Clay ◽  
Clay Layer ◽  
Bending Moments ◽  
Pile Head ◽  
Design Rules ◽  
Negative Skin Friction ◽  
Negative Friction ◽  
One Year ◽  
Regional Settlement

In Part I of this report the results are given from 43 months of measurements of forces and bending moments on two instrumented precast piles driven through 40 m (130 ft) of soft clay and 15 m (50 ft) into underlying silt and sand. The force in the piles increased due to negative skin friction. After the first 5 months a force of nearly 40 tons was observed at the bottom of the clay layer. During this time the reconsolidation of the clay after the driving took place. The force due to the reconsolidation effect amounted to about 30 tons, while the rest was due mainly to negative skin friction caused by a small regional settlement. The latter force increased linearly with time by about 15 tons per year. Seventeen months after the driving the pile heads were loaded with 44 tons and one year later another 36 tons were added. The load on the pile head eliminated the negative skin friction, which however started to return with the continued regional settlements.In Part II of the report general design formulae for piles considering negative skin friction are given. The formulae should be used to check that the permanent and transient working loads, which have been chosen according to ordinary design rules, are not too large when negative skin friction develops.When settlements due to negative skin friction are not acceptable, the negative friction can be reduced by applying a thin coat of bitumen to the piles. References are made to investigations concerning reduction of skin friction, and practical difficulties are pointed out.

Negative skin friction from surface settlement measurements in model group tests

1995 ◽  
Vol 32 (6) ◽  
pp. 1075-1079 ◽  
Author(s):  
Mehmet Ufuk Ergun ◽  
Devrim Sönmez
Keyword(s):  
Soft Clay ◽  
Soil Surface ◽  
Pile Group ◽  
Friction Model ◽  
Model Group ◽  
Pile Groups ◽  
Negative Skin Friction ◽  
Dense Sand ◽  
Model Study ◽  
Negative Friction

Groups of model wood piles driven to end bearing through dense sand over soft clay were used to determine the relative settlement of the soil surface inside and outside the groups as the soil was compressed by air pressure. Square 30 mm piles at spacings of 2 to 6 times the pile width were used in groups of 3 × 3, 4 × 4, and 5 × 5. The results indicate that pile group effects were negligible at pile spacings at 5 to 6 pile widths. Key words : negative friction, model study, pile groups, sand.

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.

Field Tests and Numerical Simulation of Pile Head Load Influences on Negative Skin Friction Behaviors of Piles

2011 ◽  
Vol 261-263 ◽  
pp. 1099-1103
Author(s):  
Li Nong Xia ◽  
Yun Dong Miao ◽  
Xin Tong ◽  
Shun Li
Keyword(s):  
Numerical Simulation ◽  
Skin Friction ◽  
Field Test ◽  
Axial Force ◽  
Field Tests ◽  
Neutral Position ◽  
Test Results ◽  
Pile Head ◽  
Negative Skin Friction ◽  
Load Increase

In order to study influences of different load at pile top on the behaviors of negative skin friction piles, field tests of negative skin friction behaviors of three identical piles with different loads at pile top are made in the same site. According to the field test condition, the corresponding numerical simulations are accomplished. The comparison shows that numerical simulation results and field test results in accordance well. The additional settlement induced by negative skin friction is bigger and the neutral position is higher, the additional axial force induced by negative skin friction reduces obviously in piles with pile head load compared with that in piles without pile head load induced by negative skin friction. Along with load increase, the additional settlement increases, the neutral point position becomes higher; the additional axial force reduces obviously. The result indicates there is regularity about the influences of pile head load on negative skin friction. It may be useful to the research for negative skin friction behaviors of pile.

scholarly journals Model test study of bending moment and negative skin friction for batter rock-socketed piles under surface load

2021 ◽  
Vol 283 ◽  
pp. 01039
Author(s):  
Guo Wei ◽  
Zhuang Daokun ◽  
Ren Yuxiao ◽  
Cui Wenxi ◽  
Yue Changxi ◽  
...  
Keyword(s):  
Skin Friction ◽  
Axial Force ◽  
Soil Depth ◽  
Bending Moment ◽  
Surface Load ◽  
Negative Skin Friction ◽  
Friction Resistance ◽  
Negative Friction ◽  
Inclined Angle ◽  
Consolidation Time

Batter rock-socketed piles (BRSP) foundation is one of common foundations, such as port engineering or cross-sea bridge, while there are few studies on negative skin friction for BRSP. A series of model tests are conducted to explore negative skin friction of BRSP which are embedded in thick soft clay. The effects of the inclined angle of piles and soil consolidation time to negative friction resistance and the bending moment of BRSP are analyzed. The test results show that: the development of negative friction and bending moment BRSP have pronounced time effect; the longer the consolidation time is, the slower the axial force and bending moment intensify. The ultimate pile shaft axial force and bending moment increases nonlinearly concerning the inclined angle of piles. And the “neutral point” position and peak point of bending moment is always located at 0.9~1.0 times soil depth.

scholarly journals Numerical analysis of negative skin friction on piles in soft clay

HBRC Journal ◽  
2013 ◽  
Vol 9 (1) ◽  
pp. 68-76 ◽  
Author(s):  
Yasser M. El-Mossallamy ◽  
Ashraf M. Hefny ◽  
Magdy A. Demerdash ◽  
Mohamed S. Morsy
Keyword(s):  
Numerical Analysis ◽  
Skin Friction ◽  
Soft Clay ◽  
Negative Skin Friction

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.

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