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Response of a pile group behind quay wall to liquefaction-induced lateral spreading:a shake-table investigation

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Earthquake Engineering and Engineering Vibration 2014年第4期13卷 741-749页

作者： Tang Liang Zhang Xiaoyu Ling Xianzhang Su Lei Liu Chunhui School of Civil Engineering Harbin Institute of Technology Key lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology

The response of pile foundations near a quay wall under liquefaction-induced lateral spreading remains a complex problem. This study presents the results of a shake-table test on a 2×2 pile group behind a sheet-pile quay wall that was subjected to lateral spreading. The quay wall was employed to trigger liquefaction-induced large lateral ground deformation. The discussions focus on the behavior of the pile and the soil and on the bending moment distributions within the group pile and the restoring force characteristics at the superstructure. Overall, the piles exhibited apparent pinning effects that reduced soil deformation. In addition, the rear-row piles near the quay wall experienced larger bending moments than did the front-row piles, indicating significant pile group effects. The tests showed that lateral spreading could be a primary cause of larger monotonic deformations and bending moments. It can also be concluded that the monotonic bending moments were significantly decreased due to the presence of slow soil flow. The stiffness at the superstructure was reduced because of accumulated excess pore pressure before liquefaction, and it was recovered during lateral spreading. The present study further enhances current understanding of the behavior of low-cap pile foundations under lateral spreading.

关键词： lateral spreading liquefaction pile group behavior shake-table experiment

Numerical and test study on vertical vibration characteristics of pile group in slope soil topography

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Earthquake Engineering and Engineering Vibration 2021年第2期20卷 377-390页

作者： Qu Liming Ding Xuanming Zheng Changjie Wu Chongrong Cao Guangwei College of Civil Engineering Chongqing UniversityChongqing 400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China School of Civil Engineering Fujian University of TechnologyFuzhou 350118China Fujian Provincial Key Laboratory of Advanced Technology and Informatization in Civil Engineering Fuzhou 350118China

Topography effects on the vertical vibration responses of pile group are revealed though numerical analysis and model ***,a series of model tests with different topography of ground and bedrock are *** results indicate that displacement amplitude of the pile head in sloping ground topography is larger than in horizontal *** displacement at various positions of the pile cap is observed in non-horizontal ***,a numerical algorithm is employed to further explore the essential response characteristics in group piles of different topography configurations,which has been verified by the test *** lengths of the exposed and frictional segment,together with the thickness of the subsoil layer,are the dominant factors which cause non-axisymmetric vibration at the pile cap.

关键词： topography effects pile group vibration response model test numerical method

Behavior of pile group with Elevated Cap Subjected to Cyclic Lateral Loads

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China Ocean Engineering 2015年第4期29卷 565-578页

作者：陈云敏顾明陈仁朋孔令刚张浙杭边学成 MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Department of Civil EngineeringZhejiang University Zhejiang Electric Power Design Institute

The pile group with elevated cap is widely used as foundation of offshore structures such as turbines, power transmission towers and bridge piers, and understanding its behavior under cyclic lateral loads induced by waves, tide water and winds, is of great importance to designing. A large-scale model test on 3×3 pile group with elevated cap subjected to cyclic lateral loads was performed in saturated silts. The preparation and implementation of the test is presented. Steel pipes with the outer diameter of 114 mm, thickness of 4.5 mm, and length of 6 m were employed as model piles. The pile group was cyclic loaded in a multi-stage sequence with the lateral displacement controlled. In addition, a single pile test was also conducted at the same site for comparison. The displacement of the pile cap, the internal forces of individual piles, and the horizontal stiffness of the pile group are presented and discussed in detail. The results indicate that the lateral cyclic loads have a greater impact on pile group than that on a single pile, and give rise to the significant plastic strain in the soil around piles. The lateral loads carried by each row of piles within the group would be redistributed with loading cycles. The lateral stiffness of the pile group decreases gradually with cycles and broadly presents three different degradation patterns in the test. Significant axial forces were measured out in some piles within the group, owing to the strong restraint provided by the cap, and finally lead to a large settlement of the pile group. These findings can be referred for foundation designing of offshore structures.

关键词： pile group large-scale model test cyclic lateral loads stiffness degradation settlement

Simplified Calculation Method and 3D Numerical Analysis for pile group Under Uplift Loading

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China Ocean Engineering 2009年第4期23卷 709-718页

作者：孔纲强杨庆刘汉龙栾茂田 State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Geotechnical Research Institute Hohai University

pile foundations of ports, mooring systems for ocean surface or submerged platforms are subjected to amount of uplift loading, and prediction of the uplift capacity is one of the most important subjects in structure designs. The paper pertains to the development of a simplified theoretical method on prediction of the uplift capacity of pile group embedded in clay assuming a composite failure surface （inverted and tnmcated circular pyramidal and cylindrical sttrface）. Various pile and soil parameters such as the arrangement of pile group, pile spacing, length, diameter of the pile and the soil properties such as unit weight, angle of internal friction and the pile-soil interface friction angle, which have direct influence on the uplift capacity of the pile group, are incorporated in the analysis. A 3D numerical model is built by FLAC3D to analyze the pile group under uplift loading for comparison, and various effect factors, such as length to diameter ratio, pile spacing and pile numbers are considered. The predicted values of uplift capacity and failure surface of pile group with different length to diameter ratio, pile spacing and soil properties are then compared with numerical analysis results and tleld test results. The predictions are found to be in good agreement with numerical analysis and measured values, which validate the correctness of the developed method. It is also found that the uplift capacity is significantly influenced by the pile-soil friction coefficient, soil shear strength, etc.

关键词： uplift capacity composite failure surface pile group limiting equilibrium 3 Drumerical analysis

Dragload and Downdrag Performances of Inclined pile group Embedded in Consolidating Soil

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Transactions of Tianjin University 2011年第3期17卷 175-180页

作者：孔纲强杨庆 Key Laboratory for Geomechanics and Embankment Engineering of Ministry of Education Geotechnical Research Institute Hohai University State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

The performance of inclined pile group embedded in consolidating soil under surcharge load was investigated by experiment in comparison with vertical pile group and single pile under the same conditions; dragload, downdrag, and layered soil settlement were measured. A three-dimensional numerical model was built via FLAC3D software, and verified by the experimental results. Influence factors, such as consolidation time, pile spacing, and pile tilt angle were analyzed. The results show that dragload of inclined pile group increases with the increase of consolidation time and pile spacing or the decrease of pile tilt angle. Downdrag of inclined pile group increases with the increase of consolidation time, pile spacing and pile tilt angle.

关键词： pile group negative skin friction consolidating soil downdrag dragload neutral plane

Shielding Effects on Dragload and Downdrag in a pile group

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Shielding Effects on Dragload and Downdrag in a Pile Group

Effect of pile-cap connection on behavior of torsionally loaded pile groups

中国土木工程学会第九届土力学及岩土工程学术会议

作者： C.J.Lee C.W.W.Ng Hong Kong University of sicence and Technology Hong Kong Hong Kong University of sicence and Technology Hong Kong

＜正＞ Shielding effects on dragload and downdrag in a pile group consisting of 5×5 piles at 2 . 5 D spacing were studied by carrying out a series of three-dimensional numerical parametric analyses, in which plastic soil slip at the pile - soil interface was considered. The investigation included the influence of location of piles in the group , surface loading, and interface friction coefficient on shielding effects . Insights into the reduction in dragload and downdrag due to the shielding effects are reported and discussed .

关键词： downdrag dragload pile group numerical analysis shielding effects soil slip soil/structure interaction

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第3期9卷 303-312页

作者： Ling-gang KONG Li-min ZHANG Key Laboratory of Soft Soils and Geoenvironmental Engineering Ministry of Education Zhejiang University Hangzhou 310027 China Department of Civil Engineering The Hong Kong University of Science and Technology Hong Kong China

To evaluate the responses of fixed and pinned pile groups under torsion, a method is presented to analyze the nonlinear behavior of free-standing pile groups with rigid pile caps. The method is capable of simulating the nonlinear soil response in the near field usingp-y and r-θ curves, the far-field interactions through Mindlin＇s and Randolph＇s elastic solutions, and the coupling effect of lateral resistance on torsional resistance of the individual piles using an empirical factor. Based on comparisons of the solutions for fixed- and pinned-head, 1×2, 2×2, and 3×3 pile groups subjected to torsion, it was found that pile-cap connection significantly influences the torsional capacity of pile groups and the assignment of applied torques in the pile groups. In this study, the applied torques for the pinned-head pile groups are only 44%-64% of those for the corresponding fixed-head pile groups at a twist angle of 2^o. Such a difference is mainly due to the change of the lateral resistances of individual piles in the groups.

关键词： pile group pile foundations Torsional response pile-cap connection Nonlinear analysis

Influence of axial load on the lateral pile groups response in cohesionless and cohesive soil

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Frontiers of Structural and Civil Engineering 2015年第2期9卷 176-193页

作者： Jasim M. ABBASA Zamri CHIK Mohd Raihan TAHA Department of Civil Engineering Diyala University Diyala Baqhuba 32001 Iraq Department of Civil and Structural Engineering Universiti Kebangsaan Malaysia Bangi Selangor 43600 UKM Malaysia

The lateral response of single and group of piles under simultaneous vertical and lateral loads has been analyzed using a 3D finite element approach. The response in this assessment considered lateral pile displacement and lateral soil resistance and corresponding - curve. As a result, modified - curves for lateral single pile response were improved with respect to the influence of increasing axial load intensities. The improved plots can be used for lateral loaded pile design and to produce the group action design -multiplier curves and equations. The effect of load combination on the lateral pile group response was performed on three pile group configurations (i.e., 2×1, 2×2 and 3×2) with four pile spacings (i.e., = 2 , 4 , 6 and 8 ). As a result, design curves were developed and applied on the actual case studies and similar expected cases for assessment of pile group behavior using improved p-multiplier. A design equation was derived from predicted design curves to be used in the evaluation of the lateral pile group action taking into account the effect of axial load intensities. It was found that the group interaction effect led to reduced lateral resistance for the pile in the group relative to that for the single pile in case of pure lateral load. While, in case of simultaneous combined loads, large axial load intensities (i.e., more than 6 , where is lateral load values) will have an increase in -multiplier by approximately 100% and will consequently contribute to greater group piles capacities.

关键词： piles pile group spacing configuration combined load

Effects of non-liquefiable crust layer and superstructure mass on the response of 2×2 pile groups to liquefaction-induced lateral spreading

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第10期15卷 2701-2719页

作者： S.Mohsen Haeri Morteza Rajabigol Saman Salaripour Hiwa Sayaf Milad Zangeneh Department of Civil Engineering Sharif University of TechnologyTehranIran

In this research,two shake table experiments were conducted to study the effects of non-liquefiable crust layer and superstructure mass on the responses of two sets of 22 pile groups to liquefactioninduced lateral *** this regard,an inclined base layer overlain by a very loose liquefiable layer was constructed in both models;while only in one model,a non-liquefiable crust layer was built.A lumped mass,being representative of a superstructure,was attached to the cap of one pile group in both *** models were fully instrumented with various sensors,including acceleration,displacement,and pore water pressure ***,the piles were instrumented with pair strain gauges to measure pure bending moments induced by cyclic and monotonic loadings associated with ground shaking and lateral spreading,*** results showed that the existence of the non-liquefiable crust layer increases both the maximum and residual soil displacements at the free field and also the maximum bending moments in the *** results of the experiments indicated that the crust layer induces a high kinematic lateral soil pressure and force on the piles which are not present in the crustless *** crust layer increases the pile cap displacement before liquefaction,albeit decreases it after liquefaction,due to the elastic rebound of the piles in the liquefiable *** crust layer postpones both liquefaction triggering and dissipation of excess pore water *** existence of the superstructure mass on the pile caps decreases the acceleration amplitude of the pile caps,while increases their maximum displacement.

关键词： Soil liquefaction Lateral spreading 1g shake table test pile group Crust layer Superstructure