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本文用轴对称有限元法分析了桩基的蠕变效应。用广义开尔文模型和宾汉姆模型来分别模拟土的粘弹和粘塑性状。推导了轴对称条件下桩土接触面及桩周土体的粘弹、粘塑性应变增量公式。在此基础上编制了轴对称弹-粘弹-粘塑性有限元程序,分析了桩基的沉降、承台的荷载分担作用,以及桩体的侧阻力分布等受蠕变的影响,比较系统地研究了桩基的蠕变效应。此外,还进行了桩土接触面的摩擦试验研究。 相似文献
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Zero-thickness interface elements are applied to solve plasticity problems involving singular points where stresses and displacements are non-unique. Singular points occur in soil–structure interaction, e.g. at the ridges of footings, buried structures and foundation piles. Here the introduction of potential displacement discontinuities appears to give quite accurate finite element solutions. This is demonstrated for indentation problems both for plane strain and axisymmetric situations. In all problems the soil behaviour is modelled by the elastic–plastic Mohr–Coulomb model. 相似文献
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The plugging mechanism of infinitely-long open-ended piles is examined using numerical simulation of the wave propagation inside the soil plug and pile. It is shown that the key parameters for the plugging mechanism are the pile radius, the shape of the impact load, the shear wave velocity of the soil inside the pile, and the friction at the pile–soil interface. Consequently, the tendency of the pile to plug during driving can be assessed prior to the driving process by consideration of these key parameters. Existing one-dimensional models for the shaft response of open-ended piles are discussed and an improved model is presented. The differences between using one-dimensional models and finite element models to simulate the plugging process are examined. The differences are found to vary with the key parameters. Pile-in-pile and lumped-mass one-dimensional models are found to give satisfactory performance for some parameter combinations, while for others an axisymmetric finite element model must be used. © 1998 John Wiley & Sons, Ltd. 相似文献
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This paper presents an embedded beam formulation for discretization independent finite element (FE) analyses of interactions between pile foundations or rock anchors and the surrounding soil in geotechnical and tunneling engineering. Piles are represented by means of finite beam elements embedded within FEs for the soil represented by 3D solid elements. The proposed formulation allows consideration of piles and pile groups with arbitrary orientation independently from the FE discretization of the surrounding soil. The interface behavior between piles and the surrounding soil is represented numerically by means of a contact formulation considering skin friction as well as pile tip resistance. The pile–soil interaction along the pile skin is considered by means of a 3D frictional point‐to‐point contact formulation using the integration points of the beam elements and reference points arbitrarily located within the solid elements as control points. The ability of the proposed embedded pile model to represent groups of piles objected to combined axial and shear loading and their interactions with the surrounding soil is demonstrated by selected benchmark examples. The pile model is applied to the numerical simulation of shield driven tunnel construction in the vicinity of an existing building resting upon pile foundation to demonstrate the performance of the proposed model in complex simulation environments. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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对桩及承台采用线弹性有限元模型,对承台下桩周土采用弹塑性有限元模型,对群桩以外的土体采用线弹性无限元模型,在桩土接触面上设置接触面单元,利用三维弹塑性有限元对桩%D土%D承台相互作用进行了分析。得出了如下结论 :承台下桩顶反力总体表现出角桩最大,边桩次之,中桩最小的分布规律,随着作用在承台上的荷载增大,桩顶反力趋于均匀分布,承台下桩侧摩阻力是由桩端向桩顶逐渐发展的,承台对桩上部侧摩擦阻力存在削弱作用。为了验证本文方法的可行性,对承台下有九桩的情况进行了静载试验,将试验结果与本文计算结果进行了比较。 相似文献
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门架式双排抗滑桩的弹塑性模型与计算分析 总被引：3，自引：0，他引：3
门架式双排抗滑桩的计算模型大部分将桩排间岩土体视为弹性材料,而岩土体为弹塑性材料,使得抗滑桩内力、位移计算结果与实际情况相差较大。假设桩排间岩土体为弹塑性材料,提出一种弹塑性计算模型,该模型将桩排间岩土体看作线弹性单元和塑性单元的组合,根据结构力学知识、土的本构关系和数值分析方法建立一种计算前后排抗滑桩内力的计算方法。首先,由已知的桩顶位移,并结合结构力学位移法求出桩间土总应力。根据Lade-Duncan模型导出这两个单元的基本参数,然后,结合数值分析方法计算出抗滑桩的内力,最后,结合工程实例,运用ANSYS有限元软件进行计算分析,得出门架式双排抗滑桩的内力图。对比监测数据和弹性模型计算结果表明,弹塑性模型的计算结果比弹性模型更加接近监测值。 相似文献
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软土中已打入桩对土体位移的遮帘作用研究 总被引：1，自引：0，他引：1
采用侧向移动土中桩的理论分析结果以及有限元数值模拟,较为系统地分析了沉桩工程中已打入桩对土体侧向位移及地表隆起的遮帘作用,结果表明已打入桩对土体侧向位移的总体遮帘作用并不显著。采用不同切向劲度系数的接触面单元以模拟已打入桩间隔时间长短对地表隆起的遮帘效应,结果表明：打入桩间隔期较短时,已打入桩对地表隆起的遮拦作用主要体现在对土体位移的“水平阻隔”上,土体沿桩土界面发生流动向上隆起;而间隔期较长时,桩土间存在有较大的摩阻力而限制了土体的位移,此时已打入桩对地表隆起的遮拦作用体现在竖向摩阻力对土体隆起的“抑制”上。 相似文献
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Tapered piles represent a more equitable distribution of the pile material in several respects. In order to study their efficiency over piles of uniform section with the same material input, a three-dimensional finite element analysis is developed. The numerical procedure accounts for the non-linear elastic behaviour of both the soil and the pile-soil interface. In order to include the latter, which involves relative slip and debonding, zero/non-zero thickness interface elements are used. Three shapes of cross-section, viz. circular, square and triangular, have been attempted for the piles. The load-settlement behaviour under axial load predicted by the analysis is compared with laboratory test results obtained on instrumented model piles, installed as ‘replacement’ piles, and the fit obtained is found to be reasonably good. Also examined are interface shear and axial force in the pile, displacement and stress fields in the medium and the progression of failure in the latter. 相似文献
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Finite element simulations of the behavior of a piled raft foundation have been carried out using a multiphase model conceived as an improved homogenization approach. According to this model, the ground reinforced by a group of piles is treated as a homogeneous continuous medium. In this approach, no specific interface elements are necessary to account for the mechanical interaction between the piles and the ground: this interaction is described by means of two scalar parameters, one stiffness parameter and one which can easily be derived from the maximum ground‐pile friction. The implementation of the model into a finite element code provides an efficient tool for the analysis of the influence of the pile number or length on the settlement and bearing capacity of a square piled raft foundation and of the way the total applied load is shared between the raft and the piles. Results are compared with a standard 3D finite element analysis. The comparison highlights the fact that the proposed approach remains to be improved to account for tip resistance. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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In geotechnical engineering, numerical analysis of pile capacity is often performed in such a way that piles are modeled using only the geometry of their final position in the ground and simply loaded to failure. In these analyses, the stress changes caused by the pile installation are neglected, irrespective of the installation method. For displacement piles, which are either pushed or hammered into the ground, such an approach is a very crude simplification. To model the entire installation process of displacement piles a number of additional nonlinear effects need to be considered. As the soil adjacent to the pile is displaced significantly, small deformation theory is no longer applicable and a large deformation finite element formulation is required. In addition, the continuously changing interface between the pile and the soil has to be considered. Recently, large deformation frictional contact has been used to model the pile installation and cone penetration processes. However, one significant limitation of the analysis was the use of linear elements, which have proven to be less accurate than higher order elements for nonlinear materials such as soils.
This paper presents a large deformation frictional contact formulation which can be coupled consistently with quadratic solid elements. The formulation uses the so-called mortar-type discretisation of the contact surfaces. The performance of this contact discretisation technique is demonstrated by accurately predicting the stress transfer between the pile and the soil surfaces. 相似文献
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Y. K. Chow 《国际地质力学数值与分析法杂志》1987,11(6):621-638
A numerical method of analysis based on elasticity theory is presented for the analysis of axially and laterally loaded pile groups embedded in nonhomogeneous soils. The problem is decomposed into two systems, namely the group piles acted upon by external applied loads and pile–soil interaction forces, and a layered soil continuum acted upon by a system of pile–soil interaction forces at the imaginary positions of the piles. The group piles are discretized into discrete elements while the nonhomogeneous soil behaviour is determined from an economically viable finite element procedure. The load–deformation relationship of the pile group system is then determined by considering the equilibrium of the pile–soil interaction forces, and the compatibility of the pile and soil displacements. The influence of soil nonlinearity can be studied by limiting the soil forces at the pile–soil interface, and redistributing the ‘excess forces’ by an ‘initial stress’ process popular in elasto-plastic finite element analysis. The solutions from this approach are compared with some available published solutions for single piles and pile groups in homogeneous and nonhomogeneous soils. A limited number of field tests on pile groups are studied, and show that, in general, the computed response compares favourably with the field measurements. 相似文献
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A hybrid boundary element formulation for the steady state analysis of piles and pile groups embedded in a soil stratum in which the modulus increases linearly with depth is presented. The piles are represented by compressible columns or flexible beams and the soil as a hysteretic, layered medium. The explicit Green's function corresponding to dynamic loads in the interior of a layered stratum, developed earlier by Kausel is used in the study. The governing differential equations for the pile domain are solved for a distributed periodic loading intensity and those for the soil domain by a system of boundary elements at the pile-soil interface. These are then assembled into a system of algebraic equations by satisfying interface equilibrium and compatibility. The results of the analysis have been compared against those from alternative formulations, e.g. finite elements, and confirm the accuracy of the proposed formulation. Representative results for single piles and pile groups are presented. 相似文献
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Influence of a point sink on a pile group in saturated multilayered soils with anisotropic permeability 
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下载免费PDF全文 The behavior of a pile group is solved using the finite element method, and the fundamental solution of saturated multilayered soils with anisotropic permeability is obtained by the analytical layer element method. Based on the supposition of no slip occurring at the pile‐soil interface, the governing equations of the interaction between the pile group and the soils due to a point sink are established in the Laplace‐Hankel transformed domain by considering the pile‐soil compatibility condition. Numerical results are presented to study the effect of point sink pumping, the properties of soils, and the geometries of piles on the behavior of the pile group. 相似文献
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轴对称均匀黏弹性地基中现浇薄壁管桩竖向动力响应简化解析方法 总被引：3，自引：0，他引：3
考虑土体材料的黏性阻尼和桩-土纵向耦合振动,建立了轴对称均匀黏弹性地基中现浇薄壁管桩管桩纵向振动的定解问题,采用Laplace变换的方法求得了解析解。对一算例进行了分析,将计算结果与实测波形和有限元进行了对比,三者吻合较好。进一步分析了桩周土和桩芯土黏性阻尼系数对桩顶速度导纳和复动刚度的影响以及桩底土阻尼系数对桩顶速度导纳的影响,得到了各参数对桩纵向振动特性影响的规律 相似文献
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对土体采用Mohr-Coulomb弹塑性本构模型,用接触面单元模拟桩-土相互作用,利用ABAQUS建立桩筏基础--地基--基坑开挖三维有限元分析模型。对基坑开挖影响下的群桩基础竖向承载性状进行了分析,讨论了桩顶反力分布、桩身轴力、桩侧摩阻力以及开挖引起的桩身水平位移及其弯矩的变化规律,并进行了考虑基坑开挖与不考虑基坑开挖的群桩基础竖向承载性状的对比分析。通过研究,取得了基坑开挖对高层建筑桩筏基础影响的基本认识,这些认识对于改进桩筏基础设计理论有一定的参考意义。 相似文献
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In a field, piles are likely installed in a multi-layered soil. Analysis of axially loaded piles in a multi-layered soil is complicated and deserves more attention. A boundary element method is used in this study to analyze an axially loaded single pile in a multi-layered soil using the solution for vertical and horizontal axisymmetric ring loads in a multi-layered elastic medium. Good and reasonable agreement is obtained between the proposed and published solutions for a single pile in a homogenous soil, a finite soil, and a Gibson soil. The proposed solution is also used to evaluate an axially loaded single pile in a multi-layered (8 layers) soil. 相似文献