Study on Negative Skin Friction of Pile Groups Considering Coupled Effect of Surface Load and Soil Consolidation

2009 ◽  
Author(s):  
Gang-qiang Kong ◽  
Qing Yang ◽  
Mao-tian Luan
Keyword(s):  
Skin Friction ◽  
Influence Factors ◽  
Pile Group ◽  
Engineering Practice ◽  
Surface Load ◽  
Soil Consolidation ◽  
Test Results ◽  
Pile Groups ◽  
Negative Skin Friction ◽  
Group Effects

The study was performed based on an analysis of model test results of 3×3 pile group and confirmed the reliability and accuracy of determining negative skin friction (NSF) using numerical modeling of fluid-soild interaction. A 3D numerical model with surface load and soil consolidation was established using FLAC3D, which focused on the mechanism of NSF and its influence factors such as friction of pile-soil interface, spacing of pile and time of consolidation. The results obtained under different cases in an engineering practice were finally compared with measured and empirical data, showing that it is necessary to consider surface load and soil consolidation when dealing with NSF. The results also indicated the analysis with surface load and soil consolidation could simulate the developing process of NSF and produce a more accurate outcome — closer to measured data. The NSF increases rapidly at beginning and then slowly down, finally stabilized at a constant as soil consolidation progresses. Due to pile group effects, the piles at the centre had a smaller downdrag and settlement than those at corner or at edges; pile group effects became more obvious when pile spacing decreased.

scholarly journals Mathematical Model and Analysis of Negative Skin Friction of Pile Group in Consolidating Soil

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Gangqiang Kong ◽  
Hanlong Liu ◽  
Qing Yang ◽  
Robert Y. Liang ◽  
Hang Zhou
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
Skin Friction ◽  
Load Transfer ◽  
Pile Group ◽  
Soil Consolidation ◽  
Group Effect ◽  
Negative Skin Friction ◽  
Compressibility Coefficient ◽  
Consolidating Soil

In order to calculate negative skin friction (NSF) of pile group embedded in a consolidating soil, the dragload calculating formulas of single pile were established by considering Davis one-dimensional nonlinear consolidation soils settlement and hyperbolic load-transfer of pile-soil interface. Based on effective influence area theory, a simple semiempirical mathematical model of analysis for predicting the group effect of pile group under dragload was described. The accuracy and reliability of mathematical models built in this paper were verified by practical engineering comparative analysis. Case studies were studied, and the prediction values were found to be in good agreement with those of measured values. Then, the influences factors, such as, soil consolidation degree, the initial volume compressibility coefficient, and the stiffness of bearing soil, were analyzed and discussed. The results show that the mathematical models considering nonlinear soil consolidation and group effect can reflect the practical NSF of pile group effectively and accurately. The results of this paper can provide reference for practical pile group embedded in consolidating soil under NSF design and calculation.

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.

Experimental Program of Indoor Model Research about Single Pile Negative Friction

2014 ◽  
Vol 501-504 ◽  
pp. 160-165
Author(s):  
Chang Liu Chen ◽  
Song Qi Wei ◽  
Shuai Hua Ye ◽  
Yan Liu
Keyword(s):  
Skin Friction ◽  
Pile Foundation ◽  
Scale Model ◽  
Experimental Program ◽  
Engineering Practice ◽  
Negative Skin Friction ◽  
Friction Resistance ◽  
Model Research ◽  
Reduced Scale ◽  
Selection Of

This article aims to study the influence of negative skin friction resistance of waterishlogged pile foundation, through indoor scale model test of pile foundation in the loess areas. The program involved in the model similar than design, the model groove design, the selection of test materials, the design of the ground soil, the layout of measuring points and the research of load method in the test. Through the experimental study on the reduced scale model, we can deepen the understanding of the action mechanism of negative skin friction resistance of the pile, which could guide the engineering practice and design.

Experimental study of interaction and coupling effects in pile groups subjected to torsion

2008 ◽  
Vol 45 (7) ◽  
pp. 1006-1017 ◽  
Author(s):  
L. G. Kong ◽  
L. M. Zhang
Keyword(s):  
Coupling Effect ◽  
Pile Group ◽  
Test Results ◽  
Pile Groups ◽  
Coupling Effects ◽  
Lateral Resistance ◽  
Torsional Resistance ◽  
Pile Interaction ◽  
Group Configuration ◽  
Centrifuge Model Tests

Piles in a pile group subjected to torsion simultaneously mobilize lateral and torsional resistances. Hence, complicated pile–soil–pile interaction effects and load deformation coupling effects occur in the pile group. In this study, a series of centrifuge model tests were carried out to investigate these effects in three-diameter spaced 1 × 2, 2 × 2, and 3 × 3 pile groups subjected to torsion in both loose and dense sands. The test results showed that the effect of horizontal movement of a pile on lateral behaviors of its adjacent piles is significant in 3 × 3 pile groups and such effect varies with group configuration and pile position. The p-multiplier concept can be used to quantify the effect and values for the p-multiplier are suggested. The effect of lateral movement of a pile on the torsional resistances of its adjacent piles and the effect of torsional movement of a pile on the lateral resistances of its adjacent piles were found to be minor in these tests. For an individual pile in a pile group subjected to torsion, the mobilized lateral resistance was found to substantially increase the torsional resistance of the pile. Such a coupling effect is quantified by a coupling coefficient, β, which describes the contribution of subgrade reaction to the increase of torsional shear resistance.

scholarly journals Experimental Study on the Negative Skin Friction of the Pile Group Induced by Rising and Lowering the Groundwater Level

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yu Zhang ◽  
Li-Pei Zhou ◽  
Ming-Yuan Wang ◽  
Xuanming Ding ◽  
Chenglong Wang
Keyword(s):  
Water Level ◽  
Skin Friction ◽  
Axial Force ◽  
Groundwater Level ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pile Group ◽  
Negative Skin Friction ◽  
Influence Of Water ◽  
Bearing Characteristic

Negative skin friction (NSF) has been one of the important factors in the design of pile foundation; especially, the influence of water level on the pile negative skin friction should be paid attention. In this paper, a series of model tests were carried out to analyze the bearing characteristic of the pile group influenced by groundwater level. The pile axial force and negative skin friction, settlement, and soil pore pressure were investigated. The results showed that both the water level rising and lowering cycle could increase the axial force of the pile along the upper part of the pile, yet reducing it along the lower part of the pile; both the axial force and the negative skin friction of the pile presented a feature of time effect; the value of negative skin friction was positively correlated with that of the pile head load, and the neutral plane ranged from 0.57 L to 0.64 L as the water level changed; the soil featured settling in layers, and the change of pore water pressure was accordant with the water level changing regulation.

Field Investigation of Influences of Load on Pile Top on Negative Skin Friction Behaviors

2011 ◽  
Vol 243-249 ◽  
pp. 2138-2142
Author(s):  
Li Nong Xia ◽  
Yun Dong Miao ◽  
Shun Li ◽  
Xin Tong
Keyword(s):  
Skin Friction ◽  
Applied Load ◽  
Field Investigation ◽  
Neutral Point ◽  
Test Results ◽  
Negative Skin Friction ◽  
Field Investigations ◽  
Site Test ◽  
Made In

In order to study influences of applied load on pile top on the negative skin friction behaviors of piles, field investigations of negative skin friction behaviors of three identical piles with different loads on pile top are made in the same site. Test results show that applied load on pile top affects negative skin friction behaviors evidently. Additional settlement of pile induced by negative skin friction becomes larger, negative skin friction induced by the settlement of soil surrounding the pile becomes smaller with the increase of load on pile top. Dragload induced by negative skin friction decreases and position of neutral point in pile moves up while applied load on pile top increases. While there is no applied load on pile top, additional settlement induced by negative skin friction is minimum, dragload induced by negative skin friction is maximum and the neutral point is the farthest from the top of piles. The field investigation results may be useful to the further research for negative skin friction behaviors of pile.

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