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Stephanie Glendinning Paul Hughes Peter Helm Jonathan Chambers Joao Mendes David Gunn Paul Wilkinson Sebastien Uhlemann 《Acta Geotechnica》2014,9(5):799-816
Understanding the age and construction quality of embankments used for road and rail infrastructure is critical in the effective management and maintenance of our transport networks, worth £billions to the UK economy. This paper presents for the first time results from full-scale, carefully controlled experiments on a unique model embankment conducted over the 4-year period between 2008 and 2011. It combines point location and spatially distributed measurements of pore water pressures and water content with outputs from hydrological modelling to draw conclusions of significance to both ongoing research in this field and to the asset management practices of infrastructure owners. For researchers, the paper highlights the crucial importance of transient permeability and soil water retention behaviour of fill materials in controlling the magnitude and distribution of pore water pressure in response to climate and weather events. For practitioners, the work demonstrates that there are significant differences in pore water pressure behaviour across the embankment, which is influenced by construction-related issues such as compaction level, aspect and presence of a granular capping material. Permeability was also observed to vary across the embankment both spatially and with depth, being dependent on degree of saturation and macroscale effects, particularly within a ‘near surface zone’. It is proposed that this ‘near surface zone’ has a critical effect on embankment stability and should be the focus of both ongoing scientific research and inspection and monitoring as encompassed by asset management regimes. 相似文献
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爆炸荷载作用下的堤坝破坏形态研究在国防以及工程应用中都具有重要意义。为了研究堤坝在不同爆炸工况下产生的破坏形态,在LS-DYNA软件框架内,建立了适合于爆炸荷载作用下土体动力分析的实用模型,并基于多物质ALE法,对均质土坝遭受爆炸袭击开展了仿真分析,得到了不同炸药埋深以及不同孔隙水压力上升程度下的堤坝爆炸弹坑形态。结果表明,随着炸药埋深的增加,堤坝弹坑尺寸具有增大的趋势,但当埋深超过一定范围,则无法形成弹坑;同时,爆炸荷载作用下含水土体的孔隙水压力发展对弹坑的形成具有重要影响,孔隙水压力上升程度越强,产生的弹坑尺寸就越大。研究结果可以为堤坝抗爆安全设计以及爆破拆除堰塞坝等工程提供参考。 相似文献
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针对青藏高原冻土区高速公路拟采用的透壁通风管碎石路堤,进行了表面开放和封闭透壁通风管碎石试样降温效果的室内试验,分析比较了表面开放和封闭边界条件对透壁通风管负温通风增强碎石路堤降温效果的影响差异。分析表明,表面开放和封闭透壁通风管碎石路堤都以外界空气通过管壁透气小孔与通风管附近碎石区域孔隙空气循环产生的强迫对流传热增强降温作用,另外,表面封闭透壁通风管碎石路堤能够在上部碎石区域产生孔隙空气循环的自然对流降温效应。因此,表面封闭透壁通风管碎石路堤的降温效果更为显著。 相似文献
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以某高速公路填筑试验路堤为例,基于非饱和土渗透及强度理论,采用渗流场与应力场、稳定性计算耦合的方法,对两种不同透水特性的路堤在降雨过程中孔隙水压力和稳定性系数随时间变化的特点及规律进行较为深入的探讨。结果表明,（1）透水性能较好的路堤斜坡下部降雨入渗要强于斜坡上部,透水性能较差的路堤斜坡,雨水往往以近似于均匀的形式入渗;（2）透水能力强的路堤斜坡在短暂的超强降雨或者强度较低但持续时间超长的降雨过程中,其最小稳定性系数易于出现滞后现象,一般滞后0.5～3 d,透水能力差的路堤斜坡最小稳定性系数有显著滞后特点,一般滞后7～15 d;（3）总降雨量一定、雨强大于等于50 mm/d条件下透水能力强斜坡能达到的最小稳定性系数随降雨时间增长而降低,而透水能力差的斜坡最小稳定性系数受雨强和降雨时间共同影响。 相似文献
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软土路基沉降变权重组合S型曲线预测方法研究 总被引：11，自引：0，他引：11
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。 相似文献
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It has been widely accepted that reinforcement made of polyethylene and polypropylene is susceptible to creep and soil’s hydraulic conductivity varies with its void ratio. However, unfortunately there is no available sensitivity analysis on time-dependent embankment behaviour taking either reinforcement viscosity or time varying hydraulic conductivity of subsoil into consideration. The influence of geosynthetic reinforcement viscosity and decreasing hydraulic conductivity with consolidation on the time-dependent performance of embankments with floating columns is investigated using a fully 3D coupled model. For an embankment at the working height corresponding to a post-consolidation polypropylene geotextile strain of about 5%, it is shown that the assumption of constant hydraulic conductivity and the failure to consider the viscous behaviour of geosynthetic reinforcement can underestimate time-dependent embankment deformations (including differential crest settlement and horizontal toe movement). The effects of factors including the foundation soil, reinforcement stiffness, column stiffness, column spacing, column type (floating and fully penetrating), and construction rate, on the time-dependent behaviour of column supported embankments are explored. 相似文献
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《Geomechanics and Geoengineering》2013,8(3):191-197
A translational failure of a highway embankment constructed on sloping ground may occur either in the mode of overall instability or in the mode of local instability. The stability analysis of the first mode is based on the assumption that the whole cross-section of the embankment will slide along the inclined base surface, whilst the second mode is based on the assumption of Rankine's active state of stress. In this paper the determination of the prevalent mode of failure – overall or local – is provided via a chart derived from force polygon analysis, with the dimensionless parameter, c′/γH, and the effective friction angle, φ′, as its axes. Furthermore, the determination of the most probable failure plane in the cross-section of the embankment is attempted and additionally the role of the cohesion in the stability is discussed. Finally, an estimation of the amplitude of failure at the road surface in the case of local instability is given. A confirmation of the aforementioned was achieved through case studies of highway embankments that have failed as a consequence of water infiltration and the development of high pore water pressures. A comparison between the local and the respective overall instability safety factor is given. 相似文献
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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. 相似文献
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软土地基上路堤填筑的破坏性状分析 总被引：5，自引：0，他引：5
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。 相似文献
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This paper aims to investigate the mechanical behaviour of a hybrid reinforced earth embankment built in limited width adjacent to a slope. This embankment system incorporates reinforced earth embankments with soil nails, installed in the existing ground. Soil nails work to provide additional resisting forces to stabilize the embankment which may be unstable due to insufficient reinforcement length. Nail forces developed in the hybrid reinforced earth embankment with various geometric conditions in the fill space are analyzed. The FE method is used to simulate the construction of the hybrid reinforced earth embankment. Influence of reinforcement length, reinforcement stiffness, and slope gradient on the nail forces developed following the construction is analyzed and discussed. Additionally, design concerns for the hybrid reinforced earth embankment system are also studied. Simple charts for estimating the maximum nail force mobilized at back of the hybrid reinforced earth embankment are established in this research and can be helpful in the design of the soil nails in the system. 相似文献
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土石坝拟静力抗震稳定性分析与坝坡地震滑移量估算 总被引：7，自引：3，他引：4
单独采用拟静力抗震稳定性安全系数,并不能准确地评价土石坝的动力稳定性, Newmark等采用刚塑体滑移量或永久变形评价土石坝地震稳定性的建议得到了逐步认同,但土石坝地震永久变形或滑移量的估算尚缺乏合理方法。为此,将土石坝地震动力响应分析和拟静力极限平衡分析相结合,提出了合理地估算坝坡上潜在滑坡体地震滑移量的数值计算方法。首先,根据土石坝地震动力响应分析,针对圆弧滑动面和非圆弧光滑渐变曲面形式滑动面,分别采用简化Bishop法及改进的简化Bishop法计算坝坡上潜在滑动体的各个时刻拟静力安全系数。随后,对其中安全系数小于1的瞬时超载阶段,通过时间积分确定潜在滑动体的滑移量。最后,结合算例并通过具体数值计算与分析探讨了竖向地震动分量、滑坡体竖向地震响应、振动孔隙水压力等各种因素对土石坝地震位移及抗震性能的影响。 相似文献
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Three-dimensional analysis of embankments on soft soils incorporating vertical drains by finite element method 总被引：4，自引：0，他引：4
Jos Leito Borges 《Computers and Geotechnics》2004,31(8):665-676
Three-dimensional behaviour of an embankment on soft soils incorporating vertical drains is analysed by a numerical model based on the finite element method. The model, which incorporates the Biot’s consolidation theory (coupled formulation of the flow and equilibrium equations) and constitutive relations simulated by the p–q–θ critical state model, is applied on both the embankment with vertical drains (three-dimensional analysis) and the same problem but without vertical drains (two-dimensional analysis). Special emphasis is given to the analysis, during and after the construction period, of the excess pore pressures, settlements, horizontal displacements and stress levels. 相似文献
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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. 相似文献
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冻土地区三角形块石路基与水平块石路基的保冷效果研究 总被引：2，自引：2，他引：0
Time varying temperatures and pore-air velocities in two gravel embankments, horizontal and triangular gravel embankments, are studied using the "Rock-Block model" and the results are visualized in the form of isotherms and velocity vectors for different times of the year. Simulation results show that for both the two embankments there is a counter-clockwise rotation of pore-air extending throughout most of the embankment during winter months, whereas in summer the pore-air rotation changes to the opposite. The pore-air velocities in the triangle gravel embankment are somewhat higher than those obtained from the horizontal gravel embankment. The stronger convection in winter enhances the upward transport of heat out of the triangle gravel embankment, thus having more apparent cooling effect than the horizontal gravel embankment. During summer months, the pore-air velocities are nearly the same for both the two embankments. The results of the present study show that though the two gravel embankments have the effect of cooling the permafrost beneath, the temperature fields in the triangle gravel embankment are a little lower and more stable compared with those gotten from the horizontal gravel embankment, showing that the triangle gravel embankment has more apparent cooling effect than the horizontal one. 相似文献
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Finite Element Method has been used to operate the numerical analysis and comparison between the traditional ventilated embankment and the adjustable ventilated embankment adopted in Qinghai-Tibet Railway construction. The numerical results show that: 1) The adjustable ventilated embankments can prevent the thermal entry from air into ducts during summer from thawing the permafrost beneath the embankments; 2) The cooling effects of the adjustable ventilated embankments on permafrost is much better than the traditional ventilated embankments although two kinds of embankments can generate the thawing bulbs at the beginning of finishing construction; 3) The drop of the mean temperature of permafrost under the adjustable ventilated embankments keeps faster than that of the mean temperature of permafrost under the traditional ventilated embankments. It is clear that the adjustable ventilated embankments can keep the embankment more stable than the traditional ventilated embankments. 相似文献
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Loess covers about one-tenth of the world’s land area. While it is often used as embankment fill, loess is not an ideal construction material due to its wet collapsible nature, as it may cause significant embankment settlement and other related problems. Although explosive compaction (EC) technology has been used for many years, the challenges in experimental testing and theoretical analysis hinder its wider application. This paper contributes to the development of a design construction scheme of EC technology for loess embankment improvement through an integrated approach that involves finite element modeling, small-scale experiments, full-scale simulation and field implementation. In this study, a reliable finite element model is developed and validated through a small-scale experiment. The model is developed based on the software ANSYS/LS-DYNA®14.5 and takes into account the coupling between different materials (including soil, explosives, air and pavement). Critical performance factors such as the volume of the explosion cavity, the density of the compacted soil and the soil pressure can be obtained directly from the model. The model is then extended to simulate full-scale embankments. A sensitivity study is conducted to establish the correlations between the design parameters and the abovementioned performance factors. The relationships served as design guidelines for the successful implementation of the EC technique in an embankment section on the Cheng-Chao highway in China. The results demonstrated the feasibility of the EC technique as a ground improvement method for loess embankments, and it illustrated the effectiveness of the numerical method as a tool in design.
相似文献20.
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. 相似文献