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.

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.

Dynamic analysis of laterally loaded pile groups in sand and clay

2002 ◽  
Vol 39 (6) ◽  
pp. 1358-1383 ◽  
Author(s):  
Yasser E Mostafa ◽  
M Hesham El Naggar
Keyword(s):  
Dynamic Loading ◽  
Dynamic Load ◽  
Load Transfer ◽  
Pile Group ◽  
Nonlinear Behaviour ◽  
Single Pile ◽  
Offshore Platforms ◽  
Group Effect ◽  
Pile Groups ◽  
Pile Head

Pile foundations supporting bridge piers, offshore platforms, and marine structures are required to resist not only static loading but also lateral dynamic loading. The static p–y curves are widely used to relate pile deflections to nonlinear soil reactions. The p-multiplier concept is used to account for the group effect by relating the load transfer curves of a pile in a group to the load transfer curves of a single pile. Some studies have examined the validity of the p-multiplier concept for the static and cyclic loading cases. However, the concept of the p-multiplier has not yet been considered for the dynamic loading case, and hence it is undertaken in the current study. An analysis of the dynamic lateral response of pile groups is described. The proposed analysis incorporates the static p–y curve approach and the plane strain assumptions to represent the soil reactions within the framework of a Winkler model. The model accounts for the nonlinear behaviour of the soil, the energy dissipation through the soil, and the pile group effect. The model was validated by analyzing the response of pile groups subjected to lateral Statnamic loading and comparing the results with field measured values. An intensive parametric study was performed employing the proposed analysis, and the results were used to establish dynamic soil reactions for single piles and pile groups for different types of sand and clay under harmonic loading with varying frequencies applied at the pile head. "Dynamic" p-multipliers were established to relate the dynamic load transfer curves of a pile in a group to the dynamic load transfer curves for a single pile. The dynamic p-multipliers were found to vary with the spacing between piles, soil type, peak amplitude of loading, and the angle between the line connecting any two piles and the direction of loading. The study indicated the effect of pile material and geometry, pile installation method, and pile head conditions on the p-multipliers. The calculated p-multipliers compared well with p-multipliers back-calculated from full scale field tests.Key words: lateral, transient loading, nonlinear, pile–soil–pile interaction, p–y curves, Statnamic.

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.

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.

scholarly journals The Group Effect on Negative Skin Friction on Piles

2015 ◽  
Vol 116 ◽  
pp. 802-808 ◽  
Author(s):  
Ting Huang ◽  
Jinhai Zheng ◽  
Weiming Gong
Keyword(s):  
Skin Friction ◽  
Group Effect ◽  
Negative Skin Friction

scholarly journals Experimental testing of a full-scale of group efficiency in multiple soil layers

2019 ◽  
Vol 13 (3) ◽  
pp. 135-142
Author(s):  
Le Thiet Trung ◽  
Duong Diep Thuy ◽  
Pham Viet Anh
Keyword(s):  
Load Transfer ◽  
Experimental Testing ◽  
Pile Group ◽  
Load Testing ◽  
Group Effect ◽  
Pile Groups ◽  
In Situ Tests ◽  
Group Efficiency ◽  
Pile Group Effect

Results of in-situ tests showed that the performance of single isolated piles and individual piles within a group is largely different. When piles are arranged in a group, the interaction between piles and the foundation depends on the pile arrangement and the pile group effect. To date, studies on the pile group effect in Vietnam have been limited to reduced-scale laboratory testing or static load testing where piles are installed into homogeneous sandy or clayey foundation. This paper presents in situ tests which were performed on both single piles and pile groups, loaded to failure, with the aim of studying the pile group effect of piles embedded in multi-layered foundation. Strain gauges were installed along the shaft of 10 m long steel pipe piles, with a diameter of 143 mm. The influence of loose sand layers on the group effect in case of friction piles was evaluated. The experimental results indicated that the influence of sand layers was evident, and the group factor was calculated to be 1.237. Keywords: group efficiency; pile groups; axial capacity; load transfer.

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