Numerical studies of anchored sheet pile wall behavior constructed in cut and fill conditions

The construction of sheet pile walls may involve either excavation of soils in front or backfilling of soils behind the wall. These construction procedures generate different loading conditions in the soil and therefore different wall behavior should also be expected. The conventional methods, which are based on limit equilibrium approach, commonly used in the design of anchored sheet pile walls do not consider the method of construction. However, continuum mechanics numerical methods, such as finite element method, make it possible to incorporate the construction method during the analyses and design of sheet pile walls. The effect of wall construction type for varying soil conditions and wall heights were investigated using finite element modeling and analysis. The influence of construction method on soil behavior, wall deformations, wall bending moments, and anchor forces were investigated. The study results indicate that walls constructed by backfill method yield significantly higher bending moments and wall deformations. This paper presents the results of the numerical parametric study performed and comparative analyses of the anchored sheet pile walls constructed by different construction methods.     

格型钢板桩结构有限元数值分析

以有限元软件ABAQUS作为分析平台,建立波浪荷载作用下格型钢板桩结构稳定性及应力分析的三维弹塑性有限元分析模型。格型钢板桩采用壳体单元模拟,在相邻板桩之间设置铰接连接器模拟板桩之间的相对转动;土体采用Mohr-Coulomb本构模型模拟,在格型钢板桩与其内、外土体之间设置接触面单元模拟它们之间的滑移、张裂和闭合。结合某实际工程,研究结构的破坏模式、失稳特性和应力分布特性,分析参数变化对结构稳定性和环向拉力的影响,并对格内土体的剪切变形进行分析,建议格型钢板桩锁口拉力的验算断面。结果表明,铰接连接器的设置对于结构稳定性影响不大,但对环向拉力有一定影响;格内土体的剪切变形主要发生在格体中轴处,符合太沙基法结论。     

Dynamic interaction between the soil and an anchored sheet pile during seismic excitation

A subdomain approach for dynamic soil–structure interaction is proposed for the linear elastic seismic analysis of an anchored sheet pile, retaining a horizontally layered soil on rigid bedrock. A hybrid solution technique is used, employing a finite element formulation for the generalized sheet pile, a thin layer formulation for the soil and a direct stiffness formulation for the tieback; the displacement vectors of the sheet pile and the soil are decomposed, using the eigenmodes of the sheet pile and the propagating or decaying modes in the soil. The discretization can be limited to the interface(s), where pointwise continuity of the displacements is enforced, whereas a weak variational formulation is used for the stress equilibrium. The solution technique is illustrated by means of a numerical example, where the harmonic response of a flexible anchored sheet pile is considered and compared to the case where no tieback is present. Copyright © 2002 John Wiley & Sons, Ltd.     

钢板桩挡墙主动土压力分布的形状效应

采用有限元数值试验,研究帽型钢板桩的截面形状对墙后主动土压力分布规律的影响。首先,对室内缩尺模型试验进行数值模拟,对比实测数据验证数值模型的有效性;然后,建立钢板桩挡墙数值模型,模拟该挡墙在不同位移模式下土压力变化和分布的规律,与平板挡墙计算结果进行对比,分析钢板桩截面形状对土压力分布的影响,进一步探讨形状效应的可能影响因素及机制。分析结果表明,钢板桩的截面形状影响墙后主动土压力的分布形式,影响程度与位移模式有关;墙体平动和绕墙底转动情况下,钢板桩挡墙凸出部分的主动土压力值大于凹处,但墙体绕墙顶转动情况下差异不明显;主动土压力的形状效应由土拱效应引起,截面高宽比对其影响显著,墙土摩擦角影响有限。     

Design of sheet pile installation by vibration

In The Netherlands 70% of the steel sheet piles are installed with vibrators. This is because vibrators have a high production rate and therefore a low installation cost. This method only works for soft peat and clay layers and saturated sand layers which are not densely compacted. During pile installation several problems might occur. In this paper the attention is paid to avoiding jamming of the pile before it has reached its planned depth. In most of these cases this is caused by a design error which has let to a vibrator which is too light. Over the years different design tools, such as computer models, design graphs and design equations, have been developed in order to predict the minimum required vibrator force. In this paper a new design equation is presented, which consists of three parts: the mass of the sheet pile, the friction along the shaft and the soil resistance at the tip of the pile based on the cone penetration resistance. This equation and several other design tools for sheet pile installation, have been compared with 18 field tests. It was found that the general design graphs of the Dutch Union of Foundation Contractors (NVAF), the design equation of the Dutch Civil Engineering Centre for Construction Research and Design Rules (CUR) and the German design equation of the EAU1996 gave very poor results. The computer model Vibdrive from Holeyman (1996), the design graphs for specific locations from the NVAF and the new presented design equation from the author gave reasonable predictions. Since the computer program is, because of its complexity, not regarded as a design tool for daily design work and the local design graphs only exist for a small number of locations in The Netherlands, the new design equation is according to the field tests the best method for the calculation of the vibrator needed for sheet pile installation. This revised version was published online in July 2006 with corrections to the Cover Date.     

桩板墙不同类型挂板的技术经济比较

桩板墙是边坡和滑坡治理工程中常用的支挡结构形式,不同类型的挂板方式在结构受力、经济效益和环境保护等方面有显著差异。针对西部山区城市土地开发过程中的工程滑坡治理问题,基于技术经济比选阐明了桩板墙挂板类型和适用性。以兰雅星河湾项目为依托,分析了该滑坡的变形特征和治理工程总体设计,重点对桩板墙挂板方式优化比选进行详细阐述。     

The transfer matrix method applied to steel sheet pile walls

This paper proposes two subgrade reaction models for the analysis of steel sheet pile walls based on the transfer matrix method. In the first model a plastic hinge is generated when the maximum moment in the retaining structure is exceeded. The second model deals with a beam with an asymmetrical cross‐section that can bend in two directions. In the first part of this paper the transfer matrix method is explained on the basis of a simple example. Further the development of two computer models is described: Plaswall and Skewwall. The second part of this paper deals with an application of both models. In the application of Plaswall the effect of four current earth pressure theories to the subgrade reaction method is compared to a finite element calculation. It is shown that the earth pressure theory is of major importance on the calculation result of a sheet pile wall both with and without a plastic hinge. In the application of Skewwall the effectiveness of structural measures to reduce oblique bending is investigated. The results are compared to a 3D finite element calculation. It is shown that with simple structural measures the loss of structural resistance due to oblique bending can be reduced. Copyright © 2003 John Wiley & Sons, Ltd.     

卸荷式板桩高桩梁板码头结构土压力简化计算

河网地区的淤泥层一般较厚,强度较低,在这些地区新建或扩建码头时需对边坡进行大面积的开挖、换填,工程造价高,采用卸荷式板桩墙高桩梁板码头结构可以很好地解决,但目前关于这种码头结构型式的土压力计算研究非常少。借鉴遮帘板桩码头的土压力计算方法,分析探讨了该新型结构的土压力计算方法。计算中对结构进行分区处理,利用非极限状态土压力理论计算板桩河侧及灌注桩陆侧的土压力,同时考虑土拱效应和卸荷板的卸荷作用,以及平行墙理论,推导计算板桩陆侧及灌注桩河侧的土压力,最后将简化计算结果与离心模型试验结果及有限元数值分析结果进行对比,对比分析表明,该简化计算方法有一定的可行性,可供工程设计参考。     

基于饱和-非饱和渗流理论的基坑防渗措施分析

应用饱和-非饱和渗流理论,对某临河基坑进行了渗流计算,评价了基坑的渗透稳定性,并确定了基坑的最佳防渗措施及相应的参数。计算结果表明：无防渗措施时,基坑坡面土体在渗透压力作用下是不稳定的,必须采取防渗措施。从便于施工的角度考虑,采用钢板桩防渗,其位置定在距基坑右边坡6.0 m处。钢板桩长度对渗流场影响显著,钢板桩应穿过粉砂层,这样才能起到较好的防渗效果,有利于基坑边坡的稳定;同时也不宜太长,太长不仅浪费材料,效果也不会更好,最佳长度应为15.4 m。     

FRP板桩墙变形计算方法探讨

FRP复合板桩弹性模量较低,在使用过程中易产生较大的变形而导致结构无法正常使用,因此设计时要考虑其变形特性。FRP复合板桩的变形包括弯曲变形和剪切变形两部分。通过一种简化的计算FRP板桩变形的方法,使FRP复合板桩设计更为方便。运用该法计算出的最大变形与有限元计算结果较为接近,表明该法具有一定的可靠性。     

MCS-based probabilistic design of embedded sheet pile walls

A probabilistic approach to the design of embedded sheet pile walls is developed in this paper. The approach is based on Monte Carlo simulation (MCS), and it is used to investigate the performance of the partial factors and different design approaches in Eurocode 7 in achieving the target degrees of reliability. The approach is illustrated through an embedded sheet pile wall design example that has been used in literature for the evaluation of Eurocode 7. The approach deals rationally with the correlated load and resistance, and it bypasses a difficult but frequently asked question in Eurocode 7 (i.e. should the passive earth pressure be considered as a load (i.e. action) or a resistance?). The probabilistic design approach (DA) is also used to explore the effects of the soil unit weight variability and uncertainties in over-digging depth and wall friction. The effects of uncertainties in over-digging depth and wall friction are found to be significant. It is also found that, although the soil unit weight variability is generally minor, its effect on the design of embedded sheet pile walls is significant and should be properly accounted for in the design. The MCS-based probabilistic DA proposed in this study provides a straightforward way for proper consideration of such variability with relative ease.     

近海取水工程板桩墙安全性离心模型试验研究

板桩墙明沟结构是海岸电厂取水工程的一种结构型式。根据电厂取水工程初步设计方案,对电厂取水工程结构进行离心模型试验研究,分析板桩墙结构在波浪荷载作用下的安全性。试验表明,悬臂式斜拉桩板桩墙结构在设计最大波浪荷载作用下会产生较大的水平位移,墙身弯矩较大;引起板桩墙位移、弯矩的主要荷载是海床面以上的波浪荷载,板桩墙承载力主要由桩墙被动侧土体抗力提供。工程中板桩墙入土深度的增加不能有效改善墙体水平位移和墙身弯矩,不会提高板桩墙结构的承载能力。     

Probabilistic approach to the design of anchored sheet pile walls

Following a brief review of the physico-mechanical properties of soils, this work analyzes and comments upon some of the most frequently used approaches in anchored sheet pile wall design. The analysis highlights the conceptual differences between the various approaches, often leading, inevitably, to markedly diverging results. Although the probabilistic approach cannot be applied extensively, mainly because it is difficult to obtain statistical modelling of the soil mass, it nevertheless enables designers to avoid certain ambiguities that are present in the commonly used approach based on the Safety Factor. In addition, the probabilistic approach also permits handling of the calibrations required for the approaches to partial coefficients to be effective and applicable to different local conditions associated with the diversity of soils, different modes of construction, etc. Numerical results obtained for a simple probabilistic model lead to conclusions which are certainly not exhaustive but may contribute significant elements for reflection.     

Parametric studies of DDC-induced deflections of sheet pile walls in soft soils

This paper presents a thorough finite element (FE) parametric study of sheet pile wall deflections caused by deep dynamic compaction (DDC). In this study, the effects of several parameters which may affect the wall deflections were investigated. These parameters are (1) wall embedment length; (2) tamping distance; (3) impact energy per blow; (4) blow counts; (5) soil types on the supporting side of sheet pile walls; and (6) wall stiffness. The effects of these parameters were quantified and discussed, and the factors that help to reduce wall deflections were identified. A series of figures which depict the effects of these parameters were generated. Finally, some suggestions and recommendations for design and construction were reached.     

运用ANSYS对板桩墙支护模型的计算分析

运用ANSYS弹塑性有限元应用软件,对深基坑支护工程的板桩墙支护体系模型进行了分析探讨,得到了悬臂板桩墙支护模型的土体位移等值线图、主动土压力云图、墙土接触处的裂缝深度、不同土体材料的沉降影响区域半径。并求证了拉锚式支护结构的锚固力F对控制支护土体变形的有利影响。计算结果表明,ANSYS有限元程序将在深基坑支护工程的设计、施工中提供有效依据。     

流塑淤泥地层深基坑钢板桩围堰位移突变原因分析及处理

广东省珠海市洪鹤大桥主墩承台位于珠江西江流域的流塑状淤泥地层,采用钢板桩围堰进行基坑支护,基坑开挖过程中,钢板桩围堰发生较大的变形。经详细分析,发现导致事故的主要原因有地下水位持续升高导致土体力学性能显著下降、边跨侧钢板桩长度不足、基坑边缘集中荷载过大、施工控制不严、内支撑体系施工精度不足等。为了确保深基坑支护的安全,在全面分析总结了钢板桩围堰变形原因的基础上,结合实际情况,采取了增设穿透淤泥质土层的钢管桩围堰、加强内支撑体系等加固处理措施,并在实施过程中进行持续监测,最终安全地完成了基坑工程的施工。     

巴东县文家滑坡稳定性计算及其敏感性分析

在综合分析文家滑坡区域地质条件、基本特征以及滑坡形成机制的基础上,运用Geo-slope软件的渗流模拟模块,分析了不同水位条件下滑坡的地下水位线特征;进而,利用模拟的地下水位线,综合运用多种极限平衡分析方法对滑坡稳定性进行了定量计算。在此基础上,考虑到滑坡稳定计算参数的随机特征,又进一步对滑坡破坏概率进行了分析,利用Monte-Carlo模型模拟计算得到滑坡的破坏概率。由此综合评判滑坡在不同库水位条件下的稳定性。最后,将正交设计与SPSS统计软件的方差分析模块相结合,对滑坡稳定性影响因素进行了敏感性分析以指导滑坡的实际治理与监测工作。     

桩板式抗滑挡墙地震响应的振动台试验研究

汶川地震路基震害调查表明,在顺层或堆积体边坡中的桩板式抗滑挡墙具有良好的抗震性能。为了更好地了解该结构的抗震性能和优化抗震设计方法,以大型振动台模型试验为手段对其进行研究。为明确地震作用下桩板式抗滑挡墙的地震响应特性,试验采用缩尺的卧龙台站实测地震波对模型激励。试验结果揭示了土压力沿桩身分布规律、桩体位移和边坡岩土体加速度的地震响应特征。研究表明,地震土压力沿桩身呈非线性分布,竖向地震荷载对水平加速度有放大效果。所以,双向加载时的地震土压力比水平单向加载时大,但二者差距在地震基本烈度VII、VIII度区域不显著。滑坡推力、滑床对桩的土体抗力和桩身位移均与输入地震动峰值加速度成正比,即随着地震动峰值加速度的增加,加速度放大比增大;滑动面材料剪切强度折减,滑坡推力、土体抗力和抗身位移均增大,且增大速率加快。此外,结合试验成果,建议了桩板式抗滑挡墙设计时地震综合影响系数Cz的合理取值,对应地震基本烈度VII、VIII、IX度区分别为0.2、0.35、0.4。试验结果有助于揭示该结构抗震机制,也为其抗震设计提供了可靠依据。     

考虑非均质各向异性效应的阻滑桩加固土坡稳定性分析

基于极限分析上限定理与土的抗剪强度折减系数概念,考虑土的强度分布的非均质性与各向异性, 建立了土坡的极限平衡状态方程,由此确定土坡的稳定安全系数及其相应的潜在破坏模式。对于在给定的荷载条件下不能满足抗滑稳定性要求的土坡,考虑采用阻滑桩加固方式,根据桩侧有效土压力的合理分布模式确定桩体与滑动面相交的截面上等效抗滑力和抗滑力矩,考虑土的强度非均质性与各向异性的条件,利用极限分析上限定理建立阻滑桩加固土坡的极限平衡状态方程,将桩侧土压力作为目标函数,运用数学规划方法确定极限平衡状态时的临界桩侧有效土压力。通过大量的变动参数对比计算,探讨了土的强度的非均质性与各向异性等因素对阻滑桩桩侧极限抗力及最优加固位置的影响。     

倒T型导管墙桩基防波堤桩基土抗力及稳定性简化计算方法

倒T型导管墙桩基防波堤作为新型港工结构,主要依靠桩基和自身重力维持稳定。以天津港水文地质条件为算例,建立三维弹塑性有限元模型,通过荷载-位移关系曲线,确定稳定性安全系数。分析极限状态下桩基沿环向与竖向的土压力分布,得出桩侧极限水平土抗力,并将有限元结果与美国规范API土抗力计算方法进行比较。造成防波堤结构失稳的原因主要有两个,即结构自身无法满足强度要求和土体达到极限。结构自身强度达到极限时,可用p-y曲线有限差分迭代法求取安全系数;土体达到破坏极限时,可分别假定转动点位于桩轴线上和偏离桩轴线两种情况,利用极限平衡法,建立抗倾稳定性简化计算方法。经验证,理论方法得到的稳定性安全系数与有限元结果比较接近。