Dynamic response of pile group model in sandy soil to lateral excitation

The vertical bearing capacity of a special pile group of platform in an offshore gas field has been studied. Large diameter d (2.134 m), deep penetration l (96 m), small spacing sa (3.507 m), and only one row piles are the usual characteristics of the pile group foundation in offshore engineering. According to the requirements of the related design code, the super pile group effect has to be considered. However, with the usual design code, when sa/d, the ratio of spacing to diameter, is less than 2.0, there is no way to consider the pile group effect. In this paper, considering the occlusion effect of soil plug of pipe pile, several methods have been introduced to study the super pile group effect of the vertical bearing capacity. These methods include linear elastic theory method, the method recommended by the Code of Pile Foundation in Port Engineering (JTJ254-98), and the method with virtue of the existing pile group model test results. Meanwhile, the plugged and unplugged conditions have been considered, respectively. Through the analysis, the factors of safety in extreme and normal operation states are obtained, and the results satisfy the design specifications.

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Study of Dynamic Response of the Sandy Soil by Cone Penetration Testing

Procedia Engineering ◽

10.1016/j.proeng.2011.11.2662 ◽

2011 ◽

Vol 24 ◽

pp. 385-389

Author(s):

Cui Bo ◽

Gao Yong-tao ◽

Wang Yan-hui

Keyword(s):

Dynamic Response ◽

Sandy Soil ◽

Cone Penetration ◽

Penetration Testing ◽

Cone Penetration Testing

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Nonlinear vibration of pile groups under lateral loading

Canadian Geotechnical Journal ◽

10.1139/t92-077 ◽

1992 ◽

Vol 29 (4) ◽

pp. 702-710 ◽

Cited By ~ 6

Author(s):

Hans H. Vaziri ◽

Yingcai Han

Keyword(s):

Dynamic Response ◽

Nonlinear Vibration ◽

Damping Ratio ◽

Pile Group ◽

Harmonic Excitation ◽

Pile Groups ◽

Plane Normal ◽

Interaction Factors ◽

Full Scale Tests ◽

Measured Response

Dynamic response of a pile group, comprising six full-size cast-in-place reinforced concrete piles, is investigated under varying levels of lateral harmonic excitation in two directions: along a plane composed of three piles (X-direction) and along a plane normal to it composed of two piles (Y-direction). The measured response is compared with the theoretical predictions using the dynamic interaction factors approach. To account for the nonlinear response of the pile group using the theoretical model, provisions are made for yielding of soil around the piles by introducing the boundary-zone concept. It is shown that the proposed theory adequately captures the measured response of the pile group under both linear (weak excitation) and nonlinear (strong excitation) conditions. The study performed indicates that although the rocking stiffness of the pile group is strongly influenced by the number of piles along the direction of excitation, the horizontal stiffness remains virtually unaffected. The results obtained show that the stiffness and damping ratio of the pile group reduce as the excitation intensity increases. It is also found that the pile–soil–pile interaction plays a major role in the overall dynamic response of the pile group; this effect is manifested by a reduction in the stiffness and an increase in the damping of the pile group. Key words : dynamics, vibration, piles, pile group, nonlinear vibration, full-scale tests, modelling, resonance, soil separation, soil yielding.

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