FE analysis of grid reinforced embankment system on soft Bangkok clay

The behavior of a reinforced embankment on soft Bangkok clay has been analyzed by plane strain finite element method. The finite element analysis considers the selection of proper soil/reinforcement properties according to the relative displacement pattern of upper and lower interface elements. The large deformation phenomenon is simulated by updating the node coordinates, including those of the embankment elements above the current construction level, which ensures that the applied fill thickness simulates the actual field value. A full scale test reinforced embankment with a vertical face (wall) on Bangkok clay has been analyzed by the proposed finite element method, and the numerical results are compared with the field data. The response of a reinforced embankment on soft ground is principally controlled by the interaction between the reinforced soil mass and soft ground and the interaction between the grid reinforcement and the backfill soil. The tension in reinforcement and lateral displacement of the wall face varied during consolidation of foundation soil. The maximum tension force occurred in the reinforcement layer placed at the base of reinforced mass, due to bending of the reinforced mass resulting from differential settlements. It is considered necessary to account for the permeability variation of the soft ground foundation in the finite element analysis.     

软基路堤填土施工期的稳定性反演分析

提出了依据填土施工期的路堤沉降观测资料计算路基的总瞬时沉降量、总主固结沉降量和地基固指数的基因反演方法，并以实例反演计算有关参数，然后将理论模型和实测结果进行比较，二者符合较好。最后用简化Bishop条分法计算了填土过程中路堤的稳定性。     

Modelling the behaviour of an embankment on soft clay with different constitutive models

The paper investigates the effect of constitutive models on the predicted response of a simplified benchmark problem, an embankment on soft soil. The soft soil is assumed to have the properties of POKO clay from Finland and five different constitutive models are used to model the deposit. Two of the models are isotropic models, i.e. the Modified Cam Clay model and the Soft‐Soil model. The other models are recently proposed constitutive models that account for plastic anisotropy. The S‐CLAY1 and S‐CLAY1S models are embedded in a standard elasto‐plastic framework and account for anisotropy via a rotational hardening law. In addition, the S‐CLAY1S model accounts for bonding and destructuration. In contrast, the Multilaminate Model for Clay (MMC) accounts for plastic anisotropy by utilizing so‐called multilaminate framework. The results of numerical simulations show that accounting for anisotropy results in notable differences in the predicted settlements and horizontal movements compared to the predictions using the isotropic models. There are also significant differences in the K₀ predictions by the different constitutive models and this has a significant impact on the results. Copyright © 2006 John Wiley & Sons, Ltd.     

软土路基沉降变权重组合S型曲线预测方法研究

通过对软土路基沉降发展规律及其沉降曲线特点进行深入研究,在S型单项预测模型基础上,基于5种S型增长曲线模型,引进组合预测的思想,重点探讨了软土路基沉降发展的预测方法与理论,并建立了软土路基沉降预测的变权重组合S型增长模型,通过数学规划方法求解,从而可根据有限的实测沉降观测数据预测软土路基沉降发展过程。工程实例分析表明,利用该模型与方法得到的预测曲线与实测曲线吻合良好,能够满足工程要求,此外,变权重组合预测模型比其它单项模型具有明显的优越性,为软土路基沉降发展预测提供了一种有效而实用的方法。     

软土地基路堤施工控制的离心模拟试验研究

软土路基上快速填筑路堤时的稳定控制是非常重要的。为此在现行规范中,采用了一些位移或位移速率的控制标准。但实践表明,采用现行的标准仍然出现一些地基失稳的事例,说明这些标准需要进一步求证和改进。除了继续收集、分析失效事例之外,通过离心模型试验也可以进一步理解堤基失稳的机制。离心模型试验结果表明：路堤快速填筑使得地基破坏时,地基变形略呈马鞍形,坡肩处沉降比道中处沉降略大,坡脚水平位移增加较快;破坏时的位移速率与现有规范建议的控制标准基本符合,但地基内的孔隙水压力是在地基进入破坏状态并发生较大变形之后才有突然增加的趋势;此外,坡脚水平位移和道中沉降的速率比,可能是一个较好的稳定性控制的指标。     

水泥土桩联合土工格栅复合地基的离心模型试验研究

在软土地基上修筑路堤需要兼顾承载力和变形两方面的要求。针对山区沟谷软基的特点,采用了夯实水泥土桩与土工格栅联合加固的方法,是一种创新,选择合适的试验手段来研究该种型式的复合地基对于工程设计和施工具有重要意义。通过离心模型试验,模拟夯实水泥土桩联合土工格栅复合地基上路堤的填筑进程,水泥土桩采用石膏柱模拟,土工格栅采用预拉伸加筋格网模拟,试验得出了该种复合地基的工程特性。夯实水泥土桩具有较好的加固基础作用,格栅的主要作用是均衡上部荷载和减小差异沉降,采用夯实水泥土桩联合土工格栅的复合地基形式可以满足沟谷软基的沉降控制要求,其最终结论可以为设计和施工提供参考。     

Design method for calculating settlement of stiffened deep mixed column-supported embankment over soft clay

Acta Geotechnica - As a composite column, stiffened deep mixed (SDM) column is formed by inserting a precast concrete core pile into the center of a deep mixed (DM) column. The SDM columns have...     

Numerical analysis of an embankment on soft soils considering large displacements

The behaviour of an embankment built on a Portuguese soft soil is analysed considering the material and geometric non-linearity associated with a coupled soil–water formulation. The numerical predictions are compared with the field data in terms of settlements, horizontal displacements and excess pore water pressures. The repercussions of including the large displacements formulation are also studied. It is found that the analysis considering large displacements results in a decrease in settlements and an increase in the rate of excess pore pressure dissipation, both of which are related to the reduction of the thickness of a deformable layer.     

三角形周期荷载作用下软基路堤沉降研究

采用能够同时考虑主次固结变形的Yin-Graham一维弹黏塑性模型,对三角形周期荷载作用下软土路堤运行期间和运行期结束时的长期沉降进行了理论分析,获得三角形周期荷载作用下软基路堤运行期结束时的总沉降计算公式和工后沉降计算公式。分析了三角形周期荷载作用下软基不考虑流固耦合与考虑流固耦合时长期沉降之间的相互关系,证明了三角形周期荷载作用下当循环荷载次数趋向于无穷大时软基具有最终沉降量与应力随时间增长的模式无关的性质。按照文中提供的总沉降计算公式,针对具体工程的土工参数,对路堤运行期结束时的总沉降量进行了计算,并由此确定运行期开始时软基应发生的沉降量,为合理确定高速公路路面铺筑时机提供沉降标准。     

路堤下河滩相软土地基不均匀沉降分析

通过对河南焦作至巩义黄河公路大桥连接线工程持续两年多的观测,获得了有关数据两万多个。利用这些观测数据,引入路堤断面中点和两侧坡脚地基表面3点沉降的方差这一统计学指标,详细分析了地质结构,填筑速率、填筑高度以及硬壳层等因素对软基不均匀沉降的影响,得到了一些有意义的结论。这些结论对于加深软基不均匀沉降规律的研究具有积极意义。     

路堤下土工合成材料加固软土地基的极限分析

路堤或堤坝工程中土工合成材料加固软土地基得到广泛应用,但其计算方法仍有不足之处。从极限分析的角度来研究,引入滑移线法来改进极限分析上限法,推导出一种新的地基极限分析方法,并基于推导的极限承载力计算公式,把路堤破坏宽度作为变量,求解出路堤极限高度。工程实例对比分析表明,路堤极限高度计算结果与实测结果相差不大。其研究结论为软土地基路堤设计提供了一个新的和有效的方法。     

软土地基上路堤填筑的破坏性状分析

在软土地区建设高速公路、铁路等的填筑路堤越来越多,由于软土的不排水抗剪强度较低,软土地区路堤的填筑十分困难,而软土地基的渗透性很低,通常认为路堤的填筑是在不排水条件下进行。经典的设计方法是基于极限平衡法,无法考虑变形等因素,因此,能综合考虑稳定及变形等因素的有限元方法成为分析此类问题的一种有效手段。依据连云港铁路路堤在软土地基上的填筑试验资料,采用大变形有限元方法及Mohr-Coulomb模型,采用现场试验得到的土体强度值,对平面应变条件下路堤填筑的破坏性状及极限填筑高度等进行了分析,并对比了有限元分析结果及现场试验结果,结果表明,采用大变形有限元方法能够较准确的得到填筑路堤的极限高度,并有效地分析填筑路堤的破坏性状。     

爆炸排淤填石坝的稳定性分析

爆炸排淤填石法广泛用于我国浅海滩涂防波堤的修建,但爆炸排淤填石堤坝的滑动稳定性,目前还没有有效的分析方法。首先通过对处于深厚淤泥中的填石坝体和坝侧土体的极限平衡分析,推导出计算此类堤坝稳定性安全系数的新方法。然后针对一个工程实例,将新方法与几种常用边坡稳定性分析方法的计算结果进行了对比,结果表明,新法优于其他几种方法,其结果较好地反映了堤坝的实际稳定性。     

使用轻质填料处理桥头软基的设计方法探讨

基于一个非线性粘弹性本构模型描述土体的蠕变特性,建立了有限元模型,对某工程中使用EPS作换填材料所产生的效果进行了计算模拟,讨论了主次固结沉降以及超固结状态的影响,探讨了工程中产生较大工后沉降的原因,预测了工程的远期沉降量,探讨了在该类工程中设计EPS的原则和方法。     

Efficient and flexible Bayesian updating of embankment settlement on soft soils based on different monitoring datasets

Acta Geotechnica - In situ monitoring provides valuable information to update the predictions of the embankment settlement on soft soils. Observational data obtained at different monitoring moments...     

Simulation of the progressive failure of an embankment on soft soil

A pragmatic strain-softening constitutive model, which is based on Modified Cam Clay, was applied to the simulation of the progressive failure of an embankment constructed on a deposit of sensitive (strain-softening) clay in Saga, Japan. A comparison of the predictions for this case indicates that if softening is ignored, only relatively small deflections and consolidation settlements are predicted, especially after construction. In contrast, for the case where softening is included in the analysis, progressive failure within the clay induces large shear deformations and finally failure of the embankment is predicted. This comparison suggests that softening-induced progressive failure should be considered in the design of embankments on such soils, and the residual strength of the deposit may have an important influence on the overall factor of safety of the construction. Detailed analyses of predicted excess pore water pressures, shear strains and shear stress levels in the ground indicate that considering the strain-softening process: (a) is associated with the buildup of excess pore water pressure; (b) promotes strain localization; and (c) results generally in a larger zone of soil involved in the failure.     

基于双曲线法的分级填筑路堤沉降预测

在软土地基上修筑路堤多采用分级施工的方法。基于传统双曲线沉降预测法基础上,提出一种软土地基上路堤分级施工情况下沉降预测的新模型,该模型考虑了土体变形的非线性特性和固结性质随荷载的变化,将沉降拟合方程中的待定参数在2个不同荷载级中分别确定。利用有较长预压期的前一级实测沉降,确定与土的固结性质有关的参数,待预测沉降荷载级的最终沉降量由该级较短预压期内实测沉降确定。通过工程实例验证了所建议模型的适用性。     

Numerical analysis of an embankment built on soft soil reinforced with deep mixing columns: Parametric study

The behaviour of an embankment built on normally consolidated soft soil reinforced with deep mixing columns is studied using a coupled soil–water formulation. The numerical predictions are analysed in terms of settlements, increments in vertical effective stresses and excess pore pressures. Firstly, the effectiveness of the use of deep mixing columns is studied. Afterwards, a parametric analysis is performed to study the influence on the soil-columns system of the replacement ratio (columns’ spacing), the deformability of the embankment and columns, and the coefficient of vertical permeability of the columns.     

土工织物加固软土路堤的有限元分析

采用有限元方法对土工织物加固软弱地基路堤的力学机理进行了研究.通过比较路基加筋和未加筋两种情况研究了土工织物的加固机理,结果表明土工织物对于提高路堤填筑高度、减少路堤侧向位移、均化路堤沉降以及加速超孔隙水压力消散有显著的效果.加筋路堤中土工织物的轴力受填筑高度、超孔压消散速度和接触面系数等因素的影响,路堤填筑高度和施工进度的控制有利于土工织物抗拉强度的发挥.对路堤安全系数的研究分析表明传统的极限平衡法验算路堤稳定性偏于保守,采用有限元方法能较好地反映土工织物的加筋作用,可以优化工程设计.     

试剂注入配合比对化学电渗法处治软黏土加固效应对比研究

化学电渗法处理软黏土作为一种快速有效的地基加固方式,近年来受到学术界的广泛关注。为了探讨试剂注入配合比对化学电渗法处治软黏土地基加固效应的影响,以联合注入CaCl₂和Na₂SiO₃溶液注入配合比为研究对象,研究注入CaCl₂和Na₂SiO₃溶液物质的量浓度比分别为1:1、1:2、1:3、2:1、3:1时的电渗排水加固软黏土地基效果,实测试验过程中的排水量、排水速率、排水微观特征(ICP-MS)以及能量消耗等变化规律,初步探讨排水效果、加固效果及均匀性等问题。研究结果表明,试验条件下,联合注入物质的量浓度比为1:1时化学电渗效果最好,且阳极腐蚀量最少、耗能量最低;试剂注入配合比对电渗效果的影响主要由加入试剂中阳离子的种类和数量决定,其中Ca²⁺对化学电渗的影响效果相对较突出。