面板对路堤式加筋土挡墙力学特性的影响

加筋土挡墙作为一种新型的轻型支挡结构,广泛应用于公路、铁路、港口等工程中。随着加筋土挡墙技术的发展,面板的类型也越来越丰富。利用Plaxis有限元软件,对路堤式加筋土挡墙进行了二维有限元计算分析。针对墙背水平土压力、垂直土压力、挡墙侧向位移、筋材应变和挡墙稳定系数等计算结果的分析,探讨了3种类型面板（返包式面板、整体式面板和拼装式面板）对路堤式加筋土挡墙力学性能的影响。研究结果表明,垂直和水平土压力的数值计算结果均小于理论值;相比较与其他两种面板的加筋土挡墙,返包式面板加筋土挡墙筋材的应变最大;面板类型对于加筋土挡墙的整体稳定性几乎没有影响。研究成果为实际工程的应用提供了理论指导。     

高速公路加筋陡坡路基长期工作特性研究

为研究高速公路环境与边坡填筑一体化设计关键技术,在对某高速公路段12 m高加筋边坡进行长期工作特性的现场试验研究基础上,建立考虑格栅黏弹性和土体黏弹塑性流变模型的高速公路加筋边坡数值分析模型,采用增量-初应变迭代法对各种工况进行了分析计算。通过与试验测试数据的对比,验证数值的可靠性,进而进行大量变动参数的数值分析,详细地探讨加筋边坡填筑过程中加筋结构的力学特性。在将试验数据和数值分析结果的对比分析的基础上,得到边坡加筋体内土压力、地基应力和格栅拉力分布规律及其成因,随后与类似加筋直墙和单级加筋路堤的研究结果对比,得到多级加筋陡坡的一般规律及其破坏模式。     

动载下土工格栅加筋桥台挡墙承载性能分析

为研究加筋土桥台结构在顶部条基动载作用下的动力响应问题,通过MTS伺服加载系统施加循环动载,开展室内加筋桥台挡墙动载破坏试验,对比分析3种格栅长度和3类格栅型式的加筋土挡墙沉降及面板水平位移、土压力、筋材应变等参数的分布规律,揭示加筋桥台挡墙的动力承载性能。试验结果表明：在循环动载下不同格栅长度及型式的加筋桥台挡墙破坏模式存在差异,M、A、B型格栅加筋长度 1.0H（H为挡墙高）的挡墙破坏模式均为冲切剪切破坏,A、B型格栅 0.7H和 0.4H的挡墙破坏模式为局部剪切破坏。加筋桥台挡墙面板侧移随筋材长度增加依次减小,A型格栅加筋土挡墙侧移系数总体上相比B型小。桥台挡墙因加筋格栅长度及型式不同导致动土压力衰减规律差异明显,当 1.0H时M型及A型筋材竖向动土压力衰减系数沿墙高呈抛物线函数模型,当 0.7H时,A型和B型筋材竖向动土压力衰减系数沿墙高皆呈指数函数模型。     

Stability analysis of membrane‐reinforced curved earth retaining walls,using a multiphase approach

The stability analysis of curved earth retaining walls, stabilized by reinforcing membranes, is investigated by means of a multiphase model developed in the framework of the yield design approach. This model is an extension of that previously developed for soils reinforced by linear inclusions. It combines the advantage of a homogenization approach in terms of improved computational efficiency, with its capability to account for a specific soil–reinforcement failure condition, in a rational and systematic way. Application of this model is performed on the illustrative example of a cylindrical‐reinforced retaining wall by means of the kinematic approach of yield design, which provides upper bound estimates for the retaining wall stability factor. Nondimensional charts are finally presented assessing the influence of relevant parameters such as the curvature of the wall, the length of the reinforcing membranes or the reinforcement pull‐out resistance. Copyright © 2009 John Wiley & Sons, Ltd.     

A multiphase approach to the stability analysis of reinforced earth structures accounting for a soil–strip failure condition

A multiphase model, developed in the context of elastoplasticity, is applied to the simulation and design of reinforced earth retaining structures. The main feature of this model is to combine the advantage of a homogenization approach, as regards its computational efficiency, with the ability to account for a specific failure condition at the interface between the soil and the reinforcing strips, which may have a decisive influence on the behavior of the structure. A particular emphasis is put on the stability analysis of this kind of reinforced soil structures, formulated within the framework of the yield design theory. Making use of a generalized rigid block failure mechanism, the stability of a reinforced earth retaining wall is investigated by means of the kinematic approach, leading to upper bound estimates for the stability factor of the structure, which are then favorably compared with the results of an elastoplastic analysis. Special attention is paid to assessing in a quantitative way how a specific soil–strip failure condition affects the stability of the reinforced earth structure as a whole.     

Pseudo-static Analysis of Reinforced Earth Retaining Wall considering Non-linear Failure Surface

The seismic stability of reinforced earth has been investigated in this paper using pseudo-static method of analysis considering horizontal and vertical seismic acceleration with non-linear failure surface. The sliding wedge is divided into a number of horizontal slices to determine the strength and length of the geo-synthetic reinforcement for seismic internal stability of battered face rigid retaining wall supporting c-Φ backfill. Results are presented in graphical form representing the required length of geo-sythetic reinforcement under seismic condition to maintain the internal stability of reinforced soil. The influences of horizontal and vertical seismic acceleration, soil friction angle, cohesion, adhesion and wall inclination angle on the required length of the geo-sythetic reinforcement have been studied. From the present study it is seen that the required length of geo-synthetic reinforcement increases due to increase in the value of seismic accelerations.     

考虑填土强度的加筋土挡墙动位移计算

加筋土挡墙在地震荷载作用下的位移大小对结构的抗震性能影响显著。为了计算地震荷载作用下加筋土挡墙的位移,Newmark滑块法通常被用于设计中。由于传统的Newmark滑块法在计算中忽略了填土强度的变化,因而采用单一峰值或残余强度的计算将可能导致计算得到的位移小于或大于实际位移值。在二楔块破坏模式的假定条件下,根据楔块的力学平衡条件,建立了加筋土挡墙滑动安全系数计算式,同时通过引入位移阈值考虑了填土的应变软化特点。通过将计算结果与模型试验结果对比,得到以下结论：相较于单楔块法,二楔块法更能真实地反映出墙体的实际破坏模式,且计算得到的屈服加速度系数更接近试验值;相较于采用单一峰值或残余强度计算的位移,考虑填土应变软化的计算解更接近于模型测试值。     

绕顶转动模式下三维被动土压力的数值研究

已有的刚性挡土墙上三维被动土压力的研究主要基于挡土墙平移模式(T位移模式)下开展的，而对挡土墙绕顶转动模式(RT位移模式)下三维被动土压力的研究尚不充分。因此，该文采用数值方法系统地研究了RT位移模式下三维被动土压力及三维空间滑裂面性状。针对无黏性土体，得到了挡土墙宽度与深度比值、土体摩擦角大小和墙土接触面摩擦角比值对三维被动土压力系数及墙后土体滑裂面的影响，并与T位移模式下的三维被动土压力系数和墙后土体的空间滑裂面形态进行了定量的比较。研究结果表明:RT位移模式下的三维被动土压力系数和空间滑裂面形态均受土体内摩擦角及墙土接触面摩擦角比值的影响，且两者之间存在相互联系。RT位移模式下的三维被动土压力系数和空间滑裂面形态与T位移模式下有显著的区别；RT位移模式下的三维被动土压力系数及空间滑裂面相比于T位移模式下较小。研究成果可为RT位移模式下三维被动土压力的进一步研究和相关工程设计提供参考。     

Hydraulic failure of diaphragm walls: a possible methodology for safety improvement

The paper presents a methodology aimed at reducing—or even avoiding—the risk of heave and uplift failures of reinforced concrete diaphragm walls. The method is based on the simple concept of increasing the drainage capacity of the embedded portion of the retaining walls. The behaviour of a strutted excavation in a cohesionless soil below groundwater is examined by means of two distinct series of numerical analyses, respectively focused on the hydraulic and mechanical behaviour of the retaining system. It is shown that, for some frequent cases, such methodology is capable to improve the safety of the retaining system with respect to both hydraulic and geotechnical limit states.     

不同面板形式加筋土挡墙结构特性现场试验研究

以成昆铁路复线加筋土挡墙为工程依托进行现场原位试验,对比分析工后9个月内新型整体式面板、内嵌返包结构的模块式面板和模块式面板3类加筋土挡墙的结构特性。在此期间发生两次地震,监测了震后挡墙变形及土压力变化。结果表明:整体式面板加筋土挡墙整体稳定性最好,具有良好的抗震性能,格栅应变变化率、墙体压缩量和墙面水平位移均最小。整体式面板和模块式面板加筋土挡墙墙背土压力沿墙高近似呈M型,内嵌返包结构的模块式面板加筋土挡墙墙背土压力沿墙高近似呈倒S型。整体式面板加筋土挡墙的侧向土压力系数沿墙高变化较小,小于美国联邦公路局(FHWA)加筋设计指南计算值;内嵌返包结构的模块式面板加筋土挡墙侧向土压力系数沿墙高呈增大的趋势,挡墙中、下部小于FHWA计算值,上部接近或大于静止土压力系数;模块式面板加筋土挡墙侧向土压力系数大部分处在FHWA计算值与静止土压力系数之间。3类挡墙土工格栅应变沿墙高均呈非线性变化。挡墙墙体压缩量随着时间的增加逐渐增加,在工后前50 d时间内增加速率较快,随后增加速率减缓,进入雨季之后增加速率再次增大。发生地震后,3类加筋土挡墙均出现不同程度的墙背土压力减小、格栅应变增大、墙体压缩量增加和墙面板外移的现象。     

Performance-based analysis and design for internal stability of MSE walls

ABSTRACT

Mechanically stabilized earth (MSE) walls must be designed with adequate margins of safety against internal stability failure described by tensile strength and pullout limit states. Probabilities of failure (or reliability index) will vary strongly with the accuracy of the underlying models that appear in limit state performance functions. In this paper, prior work by the authors and co-workers on this topic is reviewed. Relative performance is explored in the context of the reliability (or probability of failure) of steel and polymeric reinforcing elements in MSE walls using limit state performance functions with load and resistance models having different accuracy.     

填土相对密实度对加筋土挡墙的影响研究

自加筋土出现以来,由面板、筋材、填土组成的加筋土挡墙被广泛研究并应于道路、铁路等土建工程中。填土的压实对加筋土挡墙的变形、土压力及筋材拉力等影响显著。为研究填土相对密实度对加筋土挡墙的影响,进行了3组不同相对密实度的离心模型试验,通过试验数据分析得到以下结论：相对密实度越大,墙体变形越小,特别是加载期变形量;压实可增大面板附近土体约束,使水平土压力大于设计值;试验挡墙设计较保守,筋材填土界面摩擦系数小于设计值;筋材面板之间连接拉力分析表明,连接拉力实测值小于测试土压力。     

The Effect of the Modular Block Type on Segmental Walls in Soil Reinforced by Geogrid

The behavior of retaining walls in geosynthetic reinforced soil is complex and requires studies and research to understand the mechanisms of rupture, the behavior of the reinforcements in the soil and the behavior of the main elements of the system: reinforcement-wall-soil. Several researches have been done on the use of geosynthetics as backfill massive reinforcement material (experimental studies, numerical analysis, reduced models …). This parametric study was conducted to investigate the influence of modular blocks type on the behavior of reinforced soil segmental walls. A 3.6 m high wall is composed of modular blocks of earth sand reinforced with four geogrid layers was modeled. The properties of materials, the wall geometry, and the boundary conditions will be explained later. The finite difference computer program FLAC3D was used in this study. The results of this numerical study allowed deducing the importance of this parameter. The type of modular blocks has significant effect to decrease the values of lateral displacements of the wall and decreased tensile stress values in the layers of geogrid.

     

面板对加筋土挡墙影响的离心模型试验研究

加筋土挡墙因其特有的景观性能、协调变形性能而日益受到设计者青睐。面板作为加筋土挡墙的组成部分,对墙体的承载能力影响显著。针对现有设计规范无法考虑面板形式对结构自身力学变形特性的影响,设计并开展了整体式与分块式面板的离心模型试验。数据测试分析显示：整体式面板加载期的位移小于分块式面板位移;由于分块式面板位移较大,所以其水平土压力小于整体式面板土压力;加筋土挡墙面板底部存在应力集中现象;分块式面板筋-土界面的摩擦系数发挥值大于整体式面板数值,但两者均小于设计规范建议值;由于模型筋材长度较长并且连接件的存在,导致原型设计较为保守。     

重力式挡土墙抗滑动稳定计算方法改进研究

针对目前重力式挡土墙抗滑稳定性计算方法中存在的缺陷,将挡土墙入土部分划分成小网格,遍历搜寻出抗倾覆稳定系数最小的点,此点就是挡土墙的实际倾覆转动点所在的位置,根据此转动点的位置,将挡墙两侧的土体划分成四个部分分别计算各部分土压力,再结合墙底与地基土摩擦力的分析,推导出改进的墙体抗滑动稳定系数的计算公式。还通过改变墙体的几何参数,分析了最小抗倾覆转动点的位置和墙体抗滑稳定性系数随墙体宽度、挡土墙入土深度等的变化规律。     

铁路台阶式加筋土挡墙潜在破裂面特征模型试验

铁路台阶式加筋土挡墙的设计方法尚不成熟,现有设计方法不能满足铁路边坡工程实践的需求。潜在破裂面的确定是加筋土挡墙设计的关键,但现行规范仅对10 m以下单级加筋土挡墙的潜在破裂面有了明确的规定。为了研究台阶式加筋土挡墙在铁路荷载作用下潜在破裂面的特征,设计了1:4的大比例尺二级台阶式加筋土挡墙室内模型试验,以周期性加卸载的方式模拟铁路荷载,通过监测墙面水平位移、墙顶沉降及土工格栅筋带变形,分析确定潜在破裂面的位置和形状。试验结果表明：I级墙（下级墙）潜在破裂面形状与现行规范中的0.3H法破裂面类似,但位置更深,且下部破裂面更缓,表明潜在不稳定范围更大;II级墙（上级墙）潜在破裂面形状与朗肯主动破裂面基本一致,但并未从II级墙坡脚剪出,而是内移刺入I级墙体;研究结果可为铁路台阶式加筋土挡墙的设计提供理论参考。     

A large-scale excavation in soft Holocene deposit and its elasto-viscoplastic analysis

In the present study, the large-scale excavation in the construction is numerically back-analyzed using a soil–water-coupled finite element method with an elasto-viscoplastic model which considers the strain-induced degradation. The measurements of the deformation have been performed during the construction of a new railway station in Osaka, Japan, in which a large and deep excavation has been successfully carried out using a special deep mixing type of soil improvement method with earth retaining walls through the thick Holocene Osaka Umeda clay deposit. A comparison between the numerical results and the measurements of the excavation at Osaka shows that the simulation method can reproduce the overall deformation of the soft ground and the earth retaining walls including the time-dependent behaviour during the excavation and a deep mixing soil improvement method as an additional technique for stability are effective.     

加筋土挡墙静动力学特性大模型试验研究

为了研究加筋土挡墙在交通荷载作用下的受力变形特性,分别设计了在静载和动载作用下的加筋土挡墙大模型试验,分析了加筋土挡墙的竖向土压力、挡墙面板变形、加载板沉降以及动力加速度等参数的分布规律。试验结果表明：静、动荷载作用下加筋土挡墙受振源荷载的水平影响范围约为0.16H～0.54H（H为墙高）,挡墙土压力均呈现水平方向上由振源中心向两侧减小的趋势;同时静动荷载下挡墙面板水平位移的主要影响范围为墙顶往下约为0.55H;加载前期加筋土挡墙内部结构是一个逐渐压密的过程,动荷载作用下加载板沉降量在整个逐级荷载值变化临界处随荷载值的增大呈斜坡“阶梯”式发展;筋土结构对加速度响应有着显著的消散作用,且随着离荷载作用点距离的增大而减小。     

Analysis and Design of Retaining Wall having Reinforced Cohesive Frictional Backfill

The case of a rigid wall with inclined back face retaining reinforced cohesive-frictional backfill subjected to uniformly distributed surcharge load has been analyzed using limit equilibrium approach. The analysis considers the stability of an element of the failure wedge, which is assumed to develop in the reinforced earth mass adjoining the back face of wall. The non-dimensional charts have been developed for computing the lateral earth pressure on wall and the height of its point of application above the base of wall. The theoretical findings have been verified by model tests on a rigid wall retaining a dry cohesive-frictional soil reinforced by geogrid strips. Experimental results are in good agreement with the theoretical predictions. A design example has been included to illustrate the design procedure.     

整体刚性面板加筋土挡墙基频影响因素计算分析

作为一种柔性支挡结构,加筋土挡墙相较于传统重力式挡墙具有优越的抗震性能。由于结构在地震等动荷载作用下的动力响应大小与其自身的固有频率大小有关,因此,固有频率的研究显得尤为重要,特别是其最小值基频。以整体刚性面板加筋土挡墙为研究对象,分别用弹性地基梁模型、线性弹簧模型表示面板、填土及筋材,提出了一种加筋土挡墙固有频率计算方法。计算求得的基频值与既有瑞利能量法计算值具有较好的一致性。参数分析表明：填土中铺设筋材可以增大墙体的基频;对于加筋土挡墙,筋材长度以及筋材-填土界面摩擦系数对墙体基频影响较小;随着筋材竖向间距的增大,加筋密度对加筋土挡墙基频的影响逐渐减小;墙体基频随着面板宽度的增大先减小后增大;随着面板模量的减小,墙体基频趋于恒值。