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Guo C.,China Communication Highway Planning and Design Institute | Guo C.,Bridge National Engineering Research Center | Fu B.-Y.,China Communication Highway Planning and Design Institute | Fu B.-Y.,Bridge National Engineering Research Center | Gong W.-M.,Nanjing Southeast University
Yantu Lixue/Rock and Soil Mechanics

To make further research on the horizontal bearing capacity of caisson-pile composite foundation, the model tests on single pile and a series of caisson-pile composite foundations, under horizontal loads and the combination of vertical and horizontal loads in silty clay, are carried out. The relation between load and displacement, bending moments of pile shaft, lateral deflections of pile shaft and efficiency coefficients of group piles are investigated based on the model tests. With the constraint of caisson, the bending moments, displacements and soil resistance of pile shaft under the horizontal loads, can be reduced than the single pile without constraint; the horizontal bearing capacity of composite foundation can be improved. Under the vertical and horizontal combination loads, friction under the caisson bottom and vertical force on the pile top is also conducive to further improve the composite foundation bearing capacity. The efficiency coefficients of caisson-pile composite foundations with different pile numbers, constraint conditions on the pile top and loads on caisson are also obtained. For the case of pile distance is 6 times of the diameter, the mutual influence between each other pile is very small. © 2016, Science Press. All right reserved. Source

Wang L.,Nanjing Southeast University | Guo C.,China Communication Highway Planning and Design Institute | Mu B.-G.,Nanjing Southeast University | Gong W.-M.,Nanjing Southeast University | Sun Z.-W.,China Shanghai Architectural Design & Research Institute
Yantu Lixue/Rock and Soil Mechanics

In this study, four groups of different types of bridge foundation model are tested to research the horizontal bearing behavior of caisson-pile composite foundation in lab based on the Qiongzhou Strait bridge project. The Q-s curve and horizontal ultimate bearing capacity of these four groups of foundations in sandy soil layer are obtained. Pile bending moment and shear force of pile shaft are analyzed in detail. At the same time, the load sharing ratio of caisson and piles is discussed. The results show that the horizontal ultimate bearing capacities of a single caisson foundation are increased by 1.2 times, 1.6 times and 2 times respectively with adding skirts, steel pipe pile, or steel pipe pile and the skirt. The maximum bending moment point is in the middle of the pile shaft, i.e. at about 0.5 m under the mud surface. The horizontal load is borne mainly by the upper caisson foundation and soil layers above the middle upper part of pile. The maximum shear force is found at the joint of pile top of steel pipe and caisson pile, where the reinforcement measures should be taken in practical engineering. The research achievements could provide a better reference for design or construction of caisson-pile composite foundation. © 2015, Academia Sinica. All right reserved. Source

Lu B.,Rizhao Planning and Urban Construction Committee | Guo C.,China Communication Highway Planning and Design Institute | Gong W.,Nanjing Southeast University | Dai G.,Nanjing Southeast University
Tumu Gongcheng Xuebao/China Civil Engineering Journal

To study the load-bearing mechanism of deep pile caps that are widely used in large-scale bridge constructions, a nine-pile double thin-wall pier cap was tested to failure, and the bearing behavior of a nine-pile double thin-wall piers cap during the construction period was inspected. The laboratory and field tests indicated that the deep pile caps did not behave like conventional flexural members, and that the load bearing mechanism under line load conformed to a strut-and-tie model. Zones of concrete with primarily unidirectional compressive stresses are modeled using compression struts and tension ties as the principal reinforcements. The line load applied to pile cap can be reduced to concentrated load using the equivalent load method, to form a uniform strut-and-tie model which can be designed using the procedure in the relevant code. Source

Zhu M.-X.,Nanjing Southeast University | Gong W.-M.,Nanjing Southeast University | He X.-Y.,Nanjing Southeast University | Xu G.-P.,China Communication Highway Planning and Design Institute
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering

In order to analyze the behaviors of the passive piles under surcharge loads, firstly, a formula for the additional horizontal stress of subsoil is deduced from the modified solutions of Boussinesq. Furthermore, the computational expressions for the soil pressure on the passive side of passive piles are gained. Then, based on the soil movement and stress transfer approach, the distribution of passive load of passive piles is drawn by means of the improved theory of partial plastic deformation. Finally, differential equations for the elastic and plastic section of passive piles are established by using the tri-parameter nonlinear elastic foundation beam model considering the P-Δ effect which is caused by lateral load. The original method of combining Matrix-transfer-method with Laplace forward transformation and Laplace inverse transformation is used to solve the deformation and internal force of passive piles influenced by the surcharge loads. The proposed approach is verified by the data from an experiment. The results indicate that the computed and test results are in good agreement. The proposed approach has reference value for studying the bearing mechanism of passive piles due to surcharge loads. Source

Gong W.,Nanjing Southeast University | Huo S.,Nanjing Southeast University | Yang C.,Nanjing Southeast University | Huang X.,Nanjing Southeast University | Guo C.,China Communication Highway Planning and Design Institute
Shuili Xuebao/Journal of Hydraulic Engineering

The in-situ tests on lateral monotonic loading are carried out for two offshore large diameter pipe piles which diameter is 1.7 m based on East Sea Bridge offshore wind farm phase Ⅱ project. Good agreement is found between the test results and the Sørensen's correction method based on size effect on p-y curves and the results of API p-y curves method is conservative. It is recommended that detailed geological exploration or testing should be carried out to determine a realistic field of engineering geological characteristics of p-y curves, or the specification recommended p-y curves should be corrected in the design of large diameter steel pipe pile of offshore wind turbine foundations. ©, 2015, Shuili Xuebao/Journal of Hydraulic Engineering. All right reserved. Source

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