高应变条件下的离散单元虚土桩模型

doi:10.13722/j.cnki.jrme.2020.1062

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摘要基桩高应变条件下的动力响应问题是承载力预测、打桩分析等研究的基础工作，同时包含了土体应变历史变化、弹塑性、非线性特点和桩土界面滑移等复杂课题。为了更好地模拟高应变动力条件下的桩底土作用，本文构建离散单元虚土桩模型，并给出计算桩身响应的离散差分数值解法。首先将桩底土看作具有一定扩散角的虚土桩，再将实桩和虚土桩离散为一系列单元；实桩单元之间和虚土桩单元之间分别采用线性黏弹性模型和非线性弹簧–黏滞阻尼器–滑移键模型模拟相互作用，并以流变模型模拟桩侧土作用；以半正弦脉冲模拟桩顶动荷载，结合差分解法计算不同脉冲宽度和幅值作用下的桩顶速度和位移响应；结合ABAQUS三维有限元模型，验证高应变虚土桩模型动力响应计算结果，最后针对虚土桩相关参数进行敏感性分析。结果表明：(1) 离散虚土桩模型能够考虑桩底土振动及应力波在桩底土中的竖向波动，并能同时适应基桩低、高应变条件下的动力计算；(2) 虚土桩模型能够较好地预测不同激振条件下的桩顶位移和速度响应。其中，桩顶位移峰值随脉冲宽度和脉冲幅值增加近似线性增大，而桩顶速度峰值对脉冲宽度的变化并不敏感，有限元模型与虚土桩模型的计算结果一致；(3) 增加虚土桩桩长、减小扩散角、增大桩底土非线性程度、减小桩底土弹性模量及土层模量比均会提高桩顶峰值速度、峰值位移以及残余位移。虚土桩模型使得研究桩底土层分布的影响成为可能，对于高应变条件下的桩底土模拟、完善桩基高应变动力计算理论等具有一定参考价值。

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	涂园
	王奎华
	邱欣晨
	项驰轩

关键词 ：桩基础, 高应变动载试验, 虚土桩, 离散单元法, 非线性刚度, 动力响应

Abstract：The pile dynamic response under high-strain condition(HSC) is the basis work of pile capacity prediction and pile driving analysis，which involves the soil strain history，elastoplastic characteristics，nonlinearity and slippage of the pile-soil interface. In order to simulate pile base soil under HSC，a discrete-element fictitious soil pile model was proposed in this paper，and a numerical differentiation solution was given. Firstly，the pile base soil was regarded as a fictitious soil pile with a certain diffusion angle，and the real pile and the fictitious soil pile were then discretized into a series of elements. The interactions between the pile elements and the soil elements were simulated by the linear viscoelastic model and the nonlinear spring-viscous damper-slippery parallel model，respectively，and the pile shaft resistance was calculated with a rheological model. The semi-sinusoidal impulse was applied for simulating the dynamic load acting at the pile top，and the velocity and displacement responses under different impulse widths and amplitudes were calculated combined with 3-dimensional finite element model(FEM) and the proposed model. Finally，the sensitivity analysis of related parameters was carried out. The results show that the fictitious soil pile model can consider the base soil vibration and the vertical propagation of the stress wave and is applicable for both low-strain and high-strain conditions. The proposed model can accurately predict the displacement and velocity response of the pile head under various impact conditions. The displacement amplitude increases approximately linearly with the increment of the impulse width and amplitude，whereas the velocity amplitude is not sensitive to the impulse width. The calculation results by FEM and the virtual pile model are consistent. Increasing the length of the fictitious soil pile and the soil nonlinearity degree or reducing the diffusion angle，the elastic modulus and the modulus ratio of the pile base soil would increase the peak velocity，the peak displacement and the residue displacement of the pile head. The fictitious soil pile model makes it possible to study the effect of soil distribution under the pile toe and has special value for simulating pile base soil and improving the dynamic calculation theory of pile foundation under HSC.

Key words： pile foundation')" href="#">

pile foundation high strain dynamic test fictitious soil piles discrete element method nonlinear stiffness ')" href="#">dynamic response

引用本文:

涂园，王奎华，邱欣晨，项驰轩. 高应变条件下的离散单元虚土桩模型[J]. 岩石力学与工程学报, 2021, 40(8): 1687-1701.
TU Yuan，WANG Kuihua，QIU Xinchen，XIANG Chixuan. Discrete-element fictitious soil pile model under high-strain dynamic condition. , 2021, 40(8): 1687-1701.

链接本文:

http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2020.1062 或 http://rockmech.whrsm.ac.cn/CN/Y2021/V40/I8/1687

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