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1.
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
2.
Infrastructures such as roads and railways as well as urbanised areas, in mountainside regions, can frequently be endangered
by rockfalls and, therefore, need to be protected against the impact of rolling blocks. Among the various protection works
that can be used, ground reinforced embankments can be considered a feasible technique. A set of full-scale tests on embankments
made of ground reinforced by geogrids are presented and discussed. The experiments were performed in a specifically designed
and constructed test facility, where concrete blocks up to 9,000 kg in weight were thrown onto a geogrid reinforced embankment
at a speed of about 30 m/s. Several embankments made of different geogrid types, different soils and construction layouts
were tested at different impact energy levels, permitting a quantitative assessment of the resistance impact of these structures.
The experimental results were compared with those obtained from a dynamic finite element method numerical model, and a good
agreement was obtained. 相似文献
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部分排水条件下加筋路堤性状分析 总被引：2，自引：0，他引：2
使用椭圆帽土质模型分析了部分排水条件下软土地基土工合成物加筋路堤的性状,按照Biot理论模拟了固结行为。在路堤施工期地基土的部分固结和不同初始排水条件下,主要分析加筋体的刚度影响和地基土的强度轮廓面,以及在正常工作情况下和在路堤失效情况下土工合成加筋材料的应变特点。分析了加筋体对于地基土变形的影响。结果显示,加筋体可以提高路堤的破裂高度,可以明显地减小路堤施工期最大侧向变形、竖向变形和地基土隆起,可明显提高施工期路堤的安全系数。 相似文献
5.
青藏高原冻土区路面类型对路基温度场影响的非线性分析 总被引：4，自引：1，他引：3
采用焓模型, 建立含相变的冻土路基温度场, 综合考虑气温、太阳辐射、风速风向、坡面蒸发等气象因素, 将诸多气象因素归结为第二、三类边界条件的叠加组合, 对不同气温地区的沥青路面及水泥路面路基温度场进行了有限元计算. 结果表明: 路面类型对冻土路基温度场有着重要影响, 水泥路面的采用可有效地降低路面温度, 延缓冻土上限下降速率, 从而可以有效保护基底多年冻土; 从对基底冻土上限影响的角度来看, 路面类型、外部气温与路基高度三者间存在一定的动态等效关系. 相似文献
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《Computers and Geotechnics》1988,6(2):77-93
The construction of earth embankments may lead to the development of excess pore pressures in foundation and embankment soils. The ability to predict the development and dissipation of these pore pressures is important in assessing the performance of such structures. This paper describes a finite element analysis method that allows the prediction of the behaviour of embankments including stress-deformation and consolidation behaviour. The application of the method is demonstrated through application to a reinforced embankment on peat and clay and to a high rockfill dam. 相似文献
8.
Increased traffic volume has made it necessary to increase highway capacities by widening embankments and pavements. Adding a new embankment to an existing embankment induces additional stresses and deformations beneath the widened and existing portions of the embankment. Differential settlement may develop between and within the new and existing portions of the embankment, especially over soft soils. This differential settlement often causes pavement distress, such as longitudinal cracks or the drop-off (or sinking) of pavement sections. Different techniques have been adopted to remedy these problems, including the use of foundation columns, such as deep mixed columns, vibro-concrete columns, stone columns, and aggregate piers. However, design procedures for foundation columns constructed for this purpose are not well developed. The analyses of eight cases of column-supported widened embankments and two untreated foundations are presented in this paper. The factors considered include the consolidation of foundation soils under existing embankments and the spacing, region, and modulus of foundation columns. Two-dimensional finite difference software was used after the calibration of the model against a field case study and numerical analyses were conducted to investigate stresses and deformations of the widened embankments over soft soil with or without the remediation of foundation columns. The results presented in this paper include the vertical and the horizontal displacements, the maximum settlements, the transverse gradient change, and the distribution of the additional stresses induced by the widening. Recommendations are made for the design of foundation columns to remedy roadway pavement failure due to widening of embankments. 相似文献
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The settlement of highway embankments can directly affect the structural safety of road pavement. Comprehensive assessment of the long-term settlement characteristics of highway embankments is important in highway safety management. The present study conducted long-term settlement monitoring in an embankment of the Xi’an-Xianyang Highway in Shaanxi Province, China, that was constructed with recycled construction and demolition waste. Variations in sectional settlement, cumulative settlement, differential settlement, and settlement rates were made in a barricade section and an arc-shaped protective slope section. The maximum settlement observed in the barricade section was 51.75 mm, with the embankment exhibiting “basin-shaped” settlement. The maximum settlement in the arc-shaped protective slope section was 42.22 mm, and the embankment exhibited “W-shaped” settlement. Furthermore, there were two stages of great increase in the settlement rate. Based on the results, control standards for the sectional settlement of embankments constructed with recycled construction and demolition waste are proposed. Finally, a model for predicting the long-term settlement in road embankments constructed with recycled construction and demolition waste is established based on a Weibull distribution probability density function.
相似文献11.
软土地基上填筑高路堤常常面临地基承载力不足、沉降和不均匀沉降过大等问题。桩承式加筋路堤能够有效地解决这些难题。通过理论分析和有限元数值模拟,研究了路堤填土-加筋材料-桩体-桩间土之间的相互作用机理,讨论了路堤填土中的土拱效率、桩体效率、路堤底面差异沉降和筋材拉力的变化规律。研究结果表明,填土中的土拱效应和筋材张力膜效应能够有效地提高桩体效率,防止软土屈服;筋材内部拉力呈非线性分布,桩顶边缘处筋材拉力最大。 相似文献
12.
Dry soil mix (DSM) columns can be used to reduce the settlement of embankments constructed on soft clays and to improve the stability. During construction the shear strength of the columns needs to be confirmed for compliance with technical assumptions. However, the measurement of the column shear strength can be a contentious issue. All methods of assessing the ultimate shear strength of DSM columns have limitations. These are caused by uncertainties in empirical probe factors required to convert pullout or push in force measured during the lime column penetration test to shear strength and/or testing a small proportion of the DSM column volume and determining whether it is representative of the strength of the entire column. The penetration resistance measured using the lime column test is considered to be more representative of average column shear strength than some other test types. This test can be carried out as a pullout resistance test (PORT) or a push in resistance test (PIRT). Both PORT and PIRT require empirical correlations of measured resistance to an absolute measure of shear strength, in a similar manner to the Piezocone test. In this paper, finite element techniques developed for assessment of T-bar, Ball and Piezocone penetration tests , and are used to assess bounds for the empirical probe factor, N. To simulate the cemented DSM columns, analyses have incorporated a model for a strain softening material. Measured settlements from an embankment constructed on DSM ground improvement are then compared with finite element calculations to infer the shear strength of the columns. These inferred shear strengths are then compared with the results of PORT tests performed beneath the embankment. 相似文献
13.
Stiffened deep mixed (SDM) column is a new ground improvement technique to improve soft soil, which can be used to increase bearing capacity, reduce deformation, and enhance stability of soft soil. This technique has been successfully adopted to support the highway and railway embankments over soft soils in China and other countries. However, there have been limited investigations on its consolidation under embankment loading. This paper developed an analytical solution for the consolidation of embankment over soft soil with SDM column in which core pile is equal to or shorter than outer DM column. The consolidation problem was simplified as a consolidation of composite soil considering the load shear effect of core pile. The developed solution was verified by a comparison with the results computed by three-dimensional (3-D) finite element analysis. A parametric study based on the derived solution was conducted to investigate influence factors—length of core pile, diameter of core pile, diameter of SDM column, modulus of DM column, and permeability coefficient of DM column—on the consolidation behavior of SDM column-supported embankment over soft soil. The developed solution was applied to a case history of SDM column-supported embankment, and a good agreement was found between the predictions and the field measurements. 相似文献
14.
低填方桩承式路堤在交通荷载下的动力响应特性与路堤的承载能力及其稳定性密切相关。基于前人的室内模型试验,采用PFC2D软件建立了桩承式路堤离散元数值分析模型;采用数值双轴试验、数值单向压缩试验分别对路堤填料和桩间土的细观参数进行了标定;同时,根据路堤荷载传递效率对模拟结果与试验数据进行了对比分析,验证了离散元数值模型的正确性及适用性。在此基础上,在低填方路堤表面施加正弦波循环荷载,并对路堤荷载传递效率、接触力分布及路堤沉降等的变化规律进行了分析。模拟结果表明：在循环荷载作用下,低填方路堤中土拱结构的承载力先逐渐弱化并最终趋于稳定;该弱化作用在宏观上表现为路堤荷载传递效率的逐渐降低,而在细观上则表现为桩顶及桩间土上方接触力差异程度的逐渐减小;同时,土拱结构的弱化将不断加剧路堤表面的不均匀沉降。 相似文献
15.
In 1986, the Malaysian Highway Authority constructed a series of trial embankments on the Muar Plain (soft marine clay) with the aim of evaluating the effectiveness of various ground improvement techniques. This study investigates the effect of two such ground improvement schemes: (a) preloading of foundation with surface geogrids and synthetic vertical drains and (b) sand compaction piles. The paper is focused on the finite element analysis of settlements and lateral displacements of the soft foundation. In scheme (a), the numerical predictions are compared with the field measurements. In scheme (b), only the numerical analysis is presented and discussed in the absence of reliable measurements due to the malfunctioning of the electronic extensometer and inclinometer system during embankment construction. The current analysis employs critical state soil mechanics, and the deformations are predicted on the basis of the fully coupled (Biot) consolidation model. The vertical drain pattern is converted to equivalent drain walls to enable plane strain modelling, and the geogrids are simulated by linear interface slip elements. The effect of sand compaction piles is investigated considering both ideal drains and non-ideal drains, as well as varying the pile stiffness. © 1997 by John Wiley & Sons, Ltd. 相似文献
16.
桩承式加筋路堤的现场试验及数值分析 总被引：4，自引：0，他引：4
对一桩体面积置换率为8.7 %的低置换率桩承式加筋路堤进行了现场试验及三维有限元分析。现场主要进行了桩、土荷载分担,孔压、沉降及侧向水平变形等内容的观测。将观测数据与常规设计方法及三维有限元分析结果进行了对比研究,在此基础上对设计方法的适用性进行了分析。研究结果表明,路堤填土的土拱效应造成荷载向桩体转移,这种荷载转移大幅度减小了在软土层中产生的超孔隙水压力。当填土高度大于2.5 m时,土拱效应的应力折减系数可用Russell和Pierpoint或Hewlett和Randolph提出的土拱效应分析方法进行计算,其结果与三维有限元分析也较相符,但在路堤高度较小时,只有Russell和Pierpoint方法与实测结果相接近。路堤施工过程中,实测的水平变形与沉降之比仅为0.2左右,这表明采用桩承式加筋路堤不仅可减小沉降,而且可减小水平向的变形,提高路堤的稳定性。 相似文献
17.
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
18.
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
19.
青藏铁路多年冻土区路基变形裂缝发生机理及其防治 总被引：16，自引：0，他引：16
青藏铁路多年冻土区路基工程的修建,改变了路基基底多年冻土的热量平衡状态.通过对青藏铁路多年冻土区试验工程和已经施工的路基工程所发生的变形裂缝的调查和分析,认为多年冻土区路基几何尺寸不对称和路基边坡坡向不同导致的路基人为上限形态不同,是造成多年冻土区路基温度场不对称以及基底土体冻结融化过程不同步的主要原因,也是造成路基变形裂缝的主要原因.文章在此基础上提出了减少或消除路基温度场不对称,从而减少或消除这类变形裂缝的主要工程结构形式和工程措施,作者的看法和结论已经在2003年青藏铁路冻土区路基工程设计和成形路基补强工程措施设计中得到广泛应用. 相似文献