共查询到20条相似文献，搜索用时 859 毫秒
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采用弹塑性有限元法,结合岩土体结构特征,应用接触单元模拟桩土之间的不连续面,分别对单桩传统静载加载方式和自平衡加载方式进行数值模拟。自平衡加载方式的数值模拟结果与实际自平衡测试结果吻合较好,说明选取的模型和参数比较合理。进而采用此模型和参数,对传统静载加载方式进行数值模拟,得出桩上部荷载传递过程中桩及桩周岩土体应力及位移,求出各单元的应力应变,确定出桩侧法向应力,结合桩土之间摩擦试验的参数,根据莫尔-库仑理论求出桩侧摩阻力。最后将有限元数值模拟和自平衡实测侧摩阻力值进行对比,验证了在选用合理的模型和物理力学参数的基础上,有限元计算的侧摩阻力值和实测值较吻合,通过有限元方法计算获得的单桩侧摩阻力值具有一定的可借鉴性和实用性。 相似文献
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首先,介绍了基于OpenSees独立开发的一套用于挡土墙-土地震反应相互作用有限元分析计算软件RW_2DPS.据此建立了俯斜式混凝土重力挡土墙-土强震相互作用有限元模型.模型中,引入非线性有限元计算方法,选用多屈服面弹塑性本构模型模拟砂土的动力属性,应用零长度接触单元模拟墙与土体之间的接触特性,且采用一致耗能阻尼边界与速度边界条件.最后,输入随机地震动,进行挡土墙-土强震反应分析,并重点探讨墙背地震土压力和水平地震惯性力沿挡土墙高度分布规律.结果表明,墙背动土压力峰值出现在距挡土墙底约1/3墙高处;挡土墙背加速度具有放大效应,加速度峰值出现在挡土墙顶部;不同地震动作用下,加速度放大系数沿墙高分布规律不同,动土压力沿墙高变化规律基本一致. 相似文献
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横向荷载下桩-土相互作用的无网格分析 总被引：5，自引：3，他引：2
基于新型的岩土工程数值分析方法--无网格Galerkin法,利用移动最小二乘法所具备的局部化技术,引入不同材料介质之间材料不连续问题的无网格求解方法,对横向荷载作用下桩-土相互作用特性进行了无单元数值模拟分析,并采用MATLAB语言编制出相应的计算程序,由此对不同荷载作用大小、桩周土性质及桩-土刚度比等因素对桩身受力变形特性的影响进行了对比分析,获得了一些定性的结论。工程实例应用结果表明,这一方法在精度和后处理方面比传统的有限元等数值方法更具优势,且计算结果与通用有限元软件ANSYS计算结果吻合良好。 相似文献
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深基坑降水中不同的地质模型有限元应用研究 总被引：2，自引：0，他引：2
分析水-土耦合场相互作用时,将岩土视作弹塑性材料。在非线性本构关系下,考虑渗透作用,得出岩土体有限元方程,建立了基坑降水的三维水-土耦合的数学模型。对基坑降水中不同的地质模型潜水、承压水及有越流补给和实际工程条件井管、过滤管、止水帷幕分别进行了计算处理,并以武汉国际证券大厦降水工程为实例,对其降水过程进行了三维有限元计算。应用三维数值模拟方法,能很好地模拟基坑防渗帷幕、非均质和各向异性、承压-无压等一些解析法难以处理的实际工程条件和地质模型。 相似文献
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针对重力式挡土墙墙后分层填土对墙身受力影响的问题,深入研究分析墙背土压力动态变化值及规律性,利用大型通用有限元分析软件ADINA,建立了平面应变单元及墙、土接触单元的有限元计算模型,并且综合考虑墙后回填土Mo-hr-Coulomb材料本构模型,初始地应力场平衡、墙后回填土分层碾压填筑,设置墙、土之间的接触受力进行有限元... 相似文献
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采用各向异性强化-软化的有厚度薄层单元模拟了坝基软弱夹层的力学变形特性,采用无厚度接触摩擦单元模拟坝基岩体节理裂隙,对高混凝土重力坝复杂坝基抗滑稳定采用三维非线性有限元分析,利用强度储备系数法模拟坝体坝基系统的渐进破坏过程、可能失稳模式,提出了塑性屈服区贯通的强度分析方法、典型特征点位移突变的变形体分析方法以及能量法联合判定坝体坝基系统极限承载力的研究方案,得出了坝体坝基系统的极限承载力。最后针对建设中的向家坝水电站高重力坝的深层抗滑问题进行了三维非线性有限元分析,计算结果表明,系统的极限承载能力由夹泥层的强度控制,极限状态的强度储备系数为2.7。 相似文献
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自然单元法(NEM)是较近出现的一种无网格方法,其形函数兼有无网格的特点和传统有限元的优点,是一种理想的适合岩土工程问题计算的新型数值方法。介绍了自然单元法的基本原理和特性,并讨论了其在岩土工程中的具体应用。将Goodman单元引入自然单元法以实现对不连续面的模拟,研究表明,在NEM中加入节理单元的总体原则和具体的实施细节与FEM中完全相同;而在一般的无网格方法中,则稍微复杂一点。为了实现对岩土工程中常见的无限域或半无限域问题的模拟,引入了无界单元;由于自然单元法的特性,自然单元法和无界元可实现无缝“耦合”。具体的数值算例验证了上述思路。 相似文献
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《岩土力学》2017,(1):277-283
土层锚固技术在岩土工程中已得到越来越广泛应用。简单介绍了已有土层锚固界面单元形式的研究现状,分析了土层锚固界面层的特点,提出一种新的复合界面单元,该复合界面单元由接触单元和实体单元构成,其中接触单元作为锚固体与土体之间的滑动摩擦单元,实体单元体现锚杆拉拔时对周围土体的体胀特性。利用ANSYS数值模拟软件,将新的复合单元应用于锚固体与土体之间的界面层,模拟并分析锚杆拉拔时界面层的破坏特征,得到随荷载增大时界面层剪应力分布的变化过程,并将界面层的破坏分为3个阶段,即线性阶段、滑移扩展阶段、滑移阶段。通过土层锚杆原位拉拔试验,得到土层锚杆拉拔的荷载-位移曲线,分析曲线变化特征,并对数值模拟结果进行了验证。 相似文献
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刚性块体极限分析上限法常应用于岩土工程稳定性研究,然而应用时需假定刚性块体破坏模式并递推繁琐的几何关系。为此,提出一种适应性更广的基于非线性规划模型的刚体平动运动单元上限有限元法,并解决了其优化模型初始值的确定问题。通过引入有限单元思想,将计算区域离散成刚体单元,同时以单元速度和节点坐标作为决策变量,由上限定理建立非线性规划模型获得上限解。利用编制的上限有限元程序进行边坡和浅埋隧道稳定性算例验证,表明运动单元上限有限元法能调整速度间断线至较优方位,所得破坏模式特征鲜明,上限解精度高,可广泛应用于边坡、隧道等稳定性分析研究。 相似文献
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接触问题是一种常见的非线性问题,如何能够很好地模拟接触面的变形及受力特性,以及实现对变形体间的接触问题的真实模拟是该领域研究的难点问题。基于二维接触问题的实际物理意义,分别在法向和切向建立等价的互补模型。用非线性互补函数（NCP）中的Fischer-Burmeister（FB）函数将互补函数模型转化为非光滑方程组表达,用常规的Newton法求解。同时,基于高斯积分法可以用较少的积分点达到较高的精度,为了进一步提高求解精度,改善不连续的通病,对面-面接触模型在高斯点上对接触面进行处理,可通过调节积分点数目对求解精度进行控制,方法易于理解,实现方便。在此基础上建立二维接触有限元模型,通过一系列工程算例验证该方法的可行性与有效性。结果表明,与ABAQUS有限元的计算结果相比,该方法有着较高的精度,更真实地反映问题的实际。 相似文献
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提出了利用Lagrangian乘子网格来模拟顺层边坡层间结构面接触行为的方法,并推导了考虑接触约束的Lagrangian控制方程的弱形式及其有限元离散方程。Lagrangian乘子网格容许界面出现较大的切向滑移,较好地解决了接触问题中的高度非线性和响应不平滑性。应用以上方法对沪－蓉－西高速公路某顺层岩质高边坡进行了数值模拟分析,得到了临滑状态下的位移场、应力应变场、结构面上的接触状态、层间滑移距离以及接触摩擦力的分布规律。数值模拟结果表明,顺层岩质边坡的破坏是一个渐进的过程,由最初的层间错动,发展为顺层蠕滑,最后在坡底剪出而破坏;其破坏型式由最初的顺层滑动逐步向溃曲破坏转化。 相似文献
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三维边坡稳定分析的有限元弹塑性迭代解法 总被引：1，自引：0，他引：1
针对已知滑动面的三维边坡稳定分析问题,在塑性力学上限定理的基础上,提出了求解安全系数的三维有限元弹塑性迭代解法。对于滑动面的非线性特性,采用常规的矩形（平面）或立方体（空间）单元来描述,应力则符合相关联流动法则的Mohr-Coulomb强度准则。通过对弹塑性增量理论中流动法则的分析,证明了当结构达到极限状态时,滑动面内切向应力的方向与滑体的主滑方向一致,说明最终以滑动面内的切向应力作为滑体滑动力的有效性。通过迭代的方式,逐步降低滑动面材料的抗剪参数,使边坡达到极限状态,不仅快速求得了滑动面的安全系数,且能够得到边坡在接近临界失稳状态时滑动面内切向应力的分布情况和边坡的变形规律,为边坡采取加固措施提供了参考依据。最后,以椭球面滑动和楔形滑动2个经典算例和工程实例,验证了该方法的有效性和正确性。 相似文献
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Traditional approaches in contact mechanics demand complicated search algorithms at the interface between the contacting bodies. Recently, a new contact method based on the concept of a third medium has been developed, which overcomes the drawbacks of conventional contact mechanics techniques. This new scheme is based on a space filling mesh, in which the contacting bodies can move and interact. The ability and accuracy of this method in predicting displacements, as well as the contact forces, is validated by solving selected numerical examples. The potential merits of this method for analysing geotechnical problems by the finite element method are addressed. 相似文献
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Geotechnical boundary value problems involving large deformations are often difficult to solve using the classical finite element method. Large mesh distortions and contact problems can occur due to the large deformations such that a convergent solution cannot be achieved. Since Abaqus, Version 6.8, a new Coupled Eulerian–Lagrangian (CEL) approach has been developed to overcome the difficulties with regard to finite element method and large deformation analyses. This new method is investigated regarding its capabilities. First, a benchmark test, a strip footing problem is investigated and compared to analytical solutions and results of comparable finite element analyses. This benchmark test shows that CEL is well suited to deal with problems which cannot be fully solved using FEM. In further applications the CEL approach is applied to more complex geotechnical boundary value problems. First, the installation of a pile into subsoil is simulated. The pile is jacked into the ground and the results received from these analyses are compared to results of classical finite element simulations. A second case study is the simulation of a ship running aground at an embankment. The results of the CEL simulation are compared to in situ measurement data. Finally, the capabilities of the new CEL approach are evaluated regarding its robustness and efficiency. 相似文献
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Frictionless contact formulation for dynamic analysis of nonlinear saturated porous media based on the mortar method 
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下载免费PDF全文 A finite element algorithm for frictionless contact problems in a two‐phase saturated porous medium, considering finite deformation and inertia effects, has been formulated and implemented in a finite element programme. The mechanical behaviour of the saturated porous medium is predicted using mixture theory, which models the dynamic advection of fluids through a fully saturated porous solid matrix. The resulting mixed formulation predicts all field variables including the solid displacement, pore fluid pressure and Darcy velocity of the pore fluid. The contact constraints arising from the requirement for continuity of the contact traction, as well as the fluid flow across the contact interface, are enforced using a penalty approach that is regularised with an augmented Lagrangian method. The contact formulation is based on a mortar segment‐to‐segment scheme that allows the interpolation functions of the contact elements to be of order N. The main thrust of this paper is therefore how to deal with contact interfaces in problems that involve both dynamics and consolidation and possibly large deformations of porous media. The numerical algorithm is first verified using several illustrative examples. This algorithm is then employed to solve a pipe‐seabed interaction problem, involving large deformations and dynamic effects, and the results of the analysis are also compared with those obtained using a node‐to‐segment contact algorithm. The results of this study indicate that the proposed method is able to solve the highly nonlinear problem of dynamic soil–structure interaction when coupled with pore water pressures and Darcy velocity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
17.
Jianqiang Mao 《国际地质力学数值与分析法杂志》2005,29(5):525-550
This paper presents a finite element approach to solve geotechnical problems with interfaces. The behaviours of interfaces obey the Mohr–Coulomb law. The FEM formulae are constructed by means of the principle of virtual displacement with contact boundary. To meet displacement compatibility conditions on contact boundary, independent degrees of freedom are taken as unknowns in FEM equations, instead of conventional nodal displacements. Examples on pressure distribution beneath a rigid strip footing, lateral earth pressure on retaining walls, behaviours of axially loaded bored piles, a shield‐driven metro tunnel, and interaction of a sliding slope with the tunnels going through it are solved with this method. The results show good agreement with analytical solutions or with in situ test results. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Michael G. Katona 《国际地质力学数值与分析法杂志》1983,7(3):371-384
A simple friction–contact interface element is introduced which simulates frictional slippage, separation, and re-bonding of two bodies initially mating at a common interface and subsequently deforming with an arbitrary static loading schedule. Constraint equations between initially mating node pairs and the general principle of virtual work are used to formulate the interface element for a finite element solution procedure. Some advantages of the interface element include; easy implementation intostandard finite element programs, direct determination of interface forces without round-off problems, and the generality afforded by the virtual work formulation to include other non-conservative models in the system. The application of the interface element to an idealized buried culvert problem illustrates that the model behaves properly. A second application, for a long-span culvert installation with incremental soil loading, demonstrates the importance of modelling slippage at the culvert–soil interface in order to conform with experimental observations. 相似文献
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In modeling of many geomechanics problems such as underground openings, soil-foundation structure interaction problems, and in wave propagation problems through semi-infinite soil medium the soil is represented as a region of either infinite or semi-infinite extent. Numerical modeling of such problems using conventional finite elements involves a truncation of the far field in which the infinite boundary is terminated at a finite distance. In these problems, appropriate boundary conditions are introduced to approximate the solution of the infinite or semi-infinite boundaries as closely as possible. However, the task of positioning the finite boundary in conventional finite element discretization and the definition of the boundary and its conditions is very delicate and depends on the modeller's skill and intuition. Moreover, such a choice is influenced by the size of the domain to be discretized. Consequently, the dimensions of the global matrices and the time required for solution of the problem will increase considerably and also selection of the arbitrary location of truncated boundary may lead to erroneous result. In order to over come these problems, mapped infinite elements have been developed by earlier researchers (Simoni and Schrefier, 1987). In the present work the applicability of infinite element technique is examined for different geomechanics problems. A computer program INFEMEP is developed based on the conventional finite element and mapped infinite element technique. It is then validated using selected problems such as strip footing and circular footing. CPU time taken to obtain solutions using finite element approach and infinite element approach was estimated and presented to show the capability of coupled modeling in improving the computational efficiency. Mesh configurations of different sizes were used to explore the enhancement of both computational economy and solution accuracy achieved by incorporation of infinite elements to solve elastic and elasto-plastic problems in semi-infinite/finite domain as applied to geotechnical engineering. © Rapid Science Ltd. 1998 相似文献
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在地震荷载作用过程中,由于桩身材料性能与周围土体性质差异较大,土体在桩-土接触面上发生张开或滑移,该强非线性接触行为直接影响接触面附近土体与桩体应力状态,从而影响上部结构地震响应水平。真实桩-土接触面由于桩身表面混凝土约束关系,具有一定厚度且存在相关体变规律的接触带。通过有限元软件ABAQUS用户自定义单元UEL程序编写改进Desai薄层接触单元,在Desai薄层接触单元中加入Rayleigh阻尼项以模拟地震作用时桩-土强非线性接触行为能量耗散过程。接触面法向与两切向本构关系采用双曲线模型。规定了Desai薄层接触单元在桩-土接触面上的行为模式以模拟土体在接触面黏结、滑动、张开、再闭合等接触状态。建立精细三维桩-土-结构体系动力相互作用模型以研究改进Desai单元对上部结构峰值动力响应水平影响,为工程结构抗震设计时程分析提供参考依据。 相似文献