边坡坡度对路堤风吹雪影响研究

路堤边坡坡度是影响风吹雪区域路堤积雪的重要因素,利用现场模型试验以及流场数值模拟的方法,研究边坡坡度对路堤积雪影响规律,分析积雪形成机理。结果表明:路堤周围积雪范围与流场风速减弱区域存在较好的对应关系,但并非定量对应,用流场中风速减弱区域简单地定量判断积雪范围的方法误差较大;迎风边坡坡度的改变对路堤周围积雪分布影响较大,较缓的迎风边坡坡度将有效地减小路堤周围积雪量和积雪范围,路面更不易形成积雪,可以减小风雪流对路堤工程的危害;背风边坡坡度的改变对路堤周围积雪影响较小,路堤设计时可作为次要因素考虑;根据试验和模拟结果得出路面不易积雪的临界边坡坡度在40°和45°之间,保守起见,建议工程应用中取40°为路面不易积雪的临界边坡坡度。     

锚杆加固在路堤边坡治理中的应用

路堤边坡失稳是生态环境和工程建设中经常遇到的广泛且严重的地质灾害之一,它给世界各国造成生命财产和经济建设的巨大损失。本文介绍了一种有效的公路路堤边坡加固技术——锚杆加固。文章首先对影响路堤边坡稳定的主要因素及锚杆加固边坡的原理进行了分析,并从锚杆设计原则、设计要素和施工要点等三个方面具体介绍了锚杆加固在路堤边坡加同中的应用。     

基于非线性有限元的路堤稳定可靠性分析

本文以非线性有限元理论和可靠度理论为基础,提出了应用于土体的非线性随机有限元的基本思路。根本土体材料的特性编制了非线性有限元程序及非线性随机有限元程序,与可靠度计算程序结合使用,得出应力、应力水平、抗剪强度可靠指标的等值线图,从而分析路堤稳定的安全系数和可靠指标。并采用降低c和tgφ值的思路得出路堤稳定的安全储备系数,并与定值方法指标进行比较。通过工程实例本文方法对路堤稳定可靠性分析的应用是很有参考意义的。     

高路堤及涵洞建造对居住环境流场的影响

高路堤涵洞是道路交通的重要组成部分,但是高路堤涵洞的建设往往会对周围环境的流场造成一定的影响。本文针对山区修建高路堤时,研究周围房屋建筑的流场变化,建筑物周围的风环境是人们关注的一个重要指标。本文用Fluent对山区典型区域进行流场分析,研究了不同高路堤及其涵洞对流域内空气流速、大气压强以及湍流度的变化情况造成的影响。探讨了路堤高度、与路堤距离以及涵洞宽度等因素与空气流速与大气压强与湍流度改变量之间的关系。主要得出以下结论:路堤越高,房屋前方空气流速、压强越小,湍流度先增大后减小。与路堤不同的距离改变时,对房屋前方的空气流速以及压强影响轻微;在距离为22 m和37 m时,湍流度变化较大,其他距离影响较小。涵洞宽度改变时,对房屋前方的空气流速影响很大,宽度越大,空气流速越大;涵洞宽度增大时,压强先增大后减小;湍流度随着涵洞宽度的增大呈现波动性分布。     

废旧轮胎加筋路堤边坡模型试验研究

废旧轮胎用于岩土工程加筋,不但可以消纳、处理大量的废旧轮胎,减轻废旧轮胎造成的环境问题,而且可以为大量的加筋土工程提供质优价廉的加筋材料。该文通过加筋边坡模型试验,对废旧轮胎加筋路堤边坡的应力、变形特性以及影响因素等加筋机理进行了探讨。试验结果表明,轮胎加筋对于路堤边坡的应力演化有显著影响,加筋路堤破坏时相对素土边坡没有出现明显整体变形破坏,应力值没有出现陡降;轮胎加筋可显著降低靠近轮胎单元体正下方及其附近砂土承担的竖向附加应力,且顶层加筋轮胎与加载板距离越小,附加应力值减小越明显;轮胎加筋对减小路堤沉降量效果明显,且荷载越大效果越显著;加筋路堤中,顶部轮胎层距离加载板越近、轮胎加筋层间距越小,路堤模型沉降越小,初始密度较小时,路堤加筋效果较好;路堤边坡加筋前后破坏形态存在明显差异,对于路堤边坡剪出口位置的影响较大,顶部轮胎位置对于路堤边坡破坏形态作用较明显。     

球笼式等速万向联轴器强度设计缺陷的回归辨识

复杂机械产品零部件的强度受多因素影响,且这些影响因素与零部件强度之间的关系非常复杂,常常难以建立其解析的数学模型,这给复杂机械产品零部件强度设计缺陷的辨识带来了困难．以球笼式等速万向联轴器为研究对象,将其内外沟道的接触应力作为强度判断的依据,将历史设计方案中影响零部件接触应力的设计参数作为因变量,建立接触应力与各相关影响因素的回归方程,通过拟合后的回归方程分析各因素对内外沟道强度的影响程度,计算出各影响因素的最大拟合误差值．将新设计方案中影响零部件接触应力的设计参数代入回归方程,求得参数设计值与回归方程的输出值之间的差值,将此差值与回归方程最大拟合误差值进行对比分析,辨识出球笼式等速万向联轴器设计中存在的强度设计缺陷,有效提高了设计质量和效率．     

公路工程路堤临界填土高度一种计算方法研究

路堤临界填土高度是公路工程中一个非常重要的问题,填筑高度小于临界填土高度时,地基的变形和稳定能得到控制。依据极坐标表示的弗拉曼公式和统一强度理论,考虑中间主应力σ₂对地基承载力的影响,推导出土的静止侧压力系数K₀≠1条件下地基的临塑与临界荷载公式,提出路堤临界填土高度一种计算方法。结合算例,对中间主剪应力系数b和土的静止侧压力系数K₀取不同值时,临界荷载与路堤临界填土高度计算结果进行了对比分析,结果表明:基于统一强度理论得到的计算方法能确切地反映地基承载力的实质,使地基土体强度得到充分的发挥。     

基于两方程模型的路堤风吹雪数值模拟

道路风吹雪灾害是风吹雪地区道路规划中考虑的重要因素之一,对于风吹雪问题,数值模拟作为其研究的主要手段之一,在近年得到了较快的发展;但由于风吹雪问题的复杂性,数值模拟方法及参数的选取还有待进一步完善。采用欧拉-欧拉方法,利用雪相两方程控制模型,结合实测经验公式确定充分发育来流雪相浓度,将其作为雪相浓度壁面条件进行模拟计算,利用平坦地面风吹雪对模拟方法进行验证,分析了湍流施密特数对路堤风吹雪模拟结果的影响,并对不同风速下路堤风吹雪进行了模拟。结果表明:平坦地面风吹雪模拟与现场实测结果一致,湍流施密特数对路堤周围空间雪相浓度计算结果影响较大,不同来流风速下路堤周围雪相浓度分布规律一致,这为进一步研究道路周围风致积雪重分布及防治提供参考。     

高填石路堤的稳定性分析

随着山区高等级公路的迅速发展，高路堤特别是高填石路堤已成为我国山区高等级公路建设中无法回避的一种路堤结构形式，在高填石路堤修筑所面临的问题中，填石路堤的经济合理的施工技术、简便易行的质量控制方法等方面是急需解决的最关键的问题。本文所要分析的就是对其稳定性的破坏原理与影响因素做出研究。     

坡度及防雪栅对路堤周边流场影响的数值研究

路堤边坡坡度是影响路堤周边流场的重要因素,防雪栅是道路风吹雪灾害中常见的防雪措施,通过改变边坡坡度以及在路堤的迎风侧合理设置防雪栅,有利于改善路堤周边的积雪分布。采用数值模拟方法研究不同边坡坡度的路堤的流场特性,分析路堤积雪分布,在此基础上,在路堤迎风侧设置防雪栅研究不同层数防雪栅对路堤的挡雪效果。结果表明:路堤的绕流场特性与边坡坡度密切相关,气流流过路堤形成的风速减弱区范围与边坡坡度成正比;通过在合理位置设置合理参数的防雪栅,可以改善路堤周边流场并减弱风雪流从而起到阻雪的效果。     

YZ32重型压路机在高填方路基压实及补强中的应用

本文通过试验主要介绍了YZ32重型压路机在高填方路基的应用,结合施工实例介绍了YZ32重型压路机在提高高填方路基的整体强度和承载能力方面显著的经济性、良好的效果性。     

寒旱区路基冻融风蚀复合侵蚀机理试验研究

寒旱区路基常年受到风沙侵蚀,同时由于强烈温差变化造成路基填料因积雪融水入渗而引起冻融循环侵蚀破坏。路基会因风蚀和冻融侵蚀的复合作用引起结构损伤下抗剪强度的持续衰减。以内蒙古那-苏省际大通道锡林郭勒盟桑根达来段的风沙土填方路段为例,考虑不设边坡防护的裸边坡为最不利情况,通过冻融风蚀风洞试验研究路基在冻融循环和风蚀循环前后填料土体抗剪强度的变化规律,将路基填料土体抗剪强度的变化作为其抗复合侵蚀能力的表征,分析冻融循环侵蚀和风蚀作用对填料土体侵蚀机理的不同,以及两种不同侵蚀作用受填料含水率的影响,揭示寒旱区路基冻融风蚀复合侵蚀机理。     

Characteristics and mechanisms of embankment deformation along the Qinghai-Tibet Railway in permafrost regions

Based on field monitoring datasets, characteristics of embankment deformation were summarized along the Qinghai-Tibet Railway in four permafrost regions with different mean annual ground temperatures (MAGTs). Then, further analyses were carried out at some typical monitoring profiles to discuss mechanisms of these embankment deformations with consideration of detailed information of thermal and subsurface conditions. The results indicated that in regions with MAGT <− 1.5 °C, embankments only experienced seasonal frost heaves, and of which the magnitudes were not significant. So, the embankments in the regions performed satisfactorily. Whereas in regions with MAGT ≥− 1.5 °C, both traditional embankment and crushed rock embankment experienced settlements, but characteristics and mechanisms of the settlements were different for the two kinds of embankment. For crushed rock embankment, the magnitudes of settlement and differential settlement between right and left embankment shoulders were not significant and increased slowly. In respect that upwards movements of permafrost tables and better thermal stability of permafrost beneath embankment, mechanism of settlements on the embankment was inferred as creep of warm and ice-rich layer often present near permafrost table. While for traditional embankment, particularly in warm and ice-rich permafrost regions, the magnitudes of settlement and differential settlement between right and left embankment shoulders were significant and still increased quickly. Considering underneath permafrost table movements and permafrost temperature rises, mechanisms of settlements on the embankment included not only creep but also thawing consolidation of underlying permafrost. Therefore, some strengthened measures were needed to ensure long-term stability of these traditional embankments, and special attention should be paid on temperature, ice content and applied load within the layer immediately beneath permafrost table since warming and thawing of the layer could give rise to considerable settlement.     

粉煤灰的路用土工性质试验分析

以阜新发电厂煤粉炉粉煤灰为研究对象,通过室内试验研究了粉煤灰的路用土工性质。该粉煤灰属于含砂低液限粉土,级配不良;粉煤灰的比重为2.27,明显低于一般粘土和砂土。在含水率18%~35%范围内均可获得较为理想的压实密度,表明粉煤灰击实密度对含水率不是很敏感。该粉煤灰渗透性较强,遇水易崩解。粉煤灰压缩系数小,因此路基填成后的沉降量也小,利于路基稳定。粉煤灰的抗剪强度主要依赖于内摩擦角,其内摩擦角远大于一般的粘土。粉煤灰的回弹模量E0值与粘土的回弹模量值差别不大。在相应的压实度条件下,该粉煤灰可用于下路堤填料、上路堤填料和下路床填料。     

Cooling effects study on ventilated embankments under the influence of the temperature differences between the sunny slopes and the shady slopes

Based on theories of heat and mass transfer, three-dimensional theoretical and numerical models were presented to analyze the temperature characteristics of embankments in permafrost regions. Conditions of air convective within crushed rock layer and the background of the climate warming in the future were considered. In addition, temperature differences between the sunny and shady slopes of embankments, as well as the uneven distribution of air temperatures inside the ventilated duct were also considered in the models. Cooling effects and temperature field characteristics of three kinds of embankments were analyzed and compared. Results of traditional embankment indicated that there were significant differences in permafrost tables between the sunny and shady slopes, and the underlying permafrost was in serious degradation. A large asymmetric 0 °C melting bulb was formed in and beneath the embankment over winter time. The analysis indicated that the duct-ventilated embankment could lower the temperature of underlying permafrost, and elevate the permafrost table under the embankment. The duct-ventilated embankment could also adjust the differences of permafrost tables, and improve the asymmetry of the temperature fields between the sunny and shady slopes. Due to climate warming, however, a 0 °C melting bulb still developed at the sunny slope foot of the duct-ventilated embankment. To prevent the 0 °C melting bulb from occurring, a closed crushed rock revetment was applied on the sunny slope, and the results indicated that the cooling effect of duct-ventilated embankment with the closed crushed rock revetment was better than that without the closed crushed rock revetment. Soils in and beneath the duct-ventilated embankment with closed crushed rock revetment could refreeze completely over winter time and this kind of embankment could also effectively adjust the differences of permafrost tables between the sunny and shady slopes.     

Thinking outside the box: The time dependent behaviour of a reinforced embankment on soft soil

Applications of eco-friendly geotextiles are gaining a preference over traditional polymeric geotextiles as measures to reinforce earth embankments. Understanding the behaviour of these eco-friendly geotextiles sometimes known as limited life geotextiles (LLG) is in its infancy. This paper explains the behaviour of an embankment reinforced with Sisal fibre geotextiles constructed within a box. The diminishing need for geotextile is represented by an external load ‘outside the box’ which can be manually controlled depending on the rate of increasing foundation shear strength. The excess pore water pressure was observed ‘outside the box’ from the end of the construction of the embankment to the end of the consolidation by monitoring the height of the water in pipes ‘outside the box’.     

In-situ study on cooling characteristics of two-phase closed thermosyphon embankment of Qinghai–Tibet Highway in permafrost regions

The two-phase closed thermosyphon is an effective thermal semiconductor which can decrease the ground temperature of the underlying permafrost only in cold seasons, but does not transfer thermal energy in warm seasons. In this paper, based on the monitoring data of experimental embankment of the Qinghai–Tibet Highway from 2004 to 2011, the working state, temperature distributions and freeze–thaw process of embankment armed with two-phase closed thermosyphon were analyzed. It was found that thermosyphon embankment could play a rapid cooling effect after construction, which can weaken the sunny side-slope thermal effect and ensure the stability of embankment effectively. Compared with traditional embankment, the thermosyphon embankment offered a relatively long freezing period in a year for the underlying permafrost. For this reason, a relatively stable low-temperature zone around thermosyphon was formed. The monitoring data indicated that the artificial permafrost table beneath the thermosyphon embankment elevated to or maintained at the natural level. The thermosyphon can help to enhance the capability of defending against climate warming and further to increase the long-term stability of the embankment in permafrost regions.     

Cooling processes and effects of crushed rock embankment along the Qinghai–Tibet Railway in permafrost regions

Crushed rock embankment (CRE) was most prevalent embankment structure with cooling measures along the Qinghai–Tibet Railway in permafrost regions. Ground temperature dataset from embankment construction (in 2002) to 2010 at nine monitoring sites along the railway were compiled to study long term cooling processes and cooling effects of CRE. Monitoring results indicated that the heat stored in filling materials could dissipate out in two cold seasons after embankment construction. Under cooling effect of CRE, permafrost tables beneath CRE moved upwards significantly during the first three years after embankment construction and then maintain almost constant. But underlying permafrost experienced different thermal process in relative warm and cold permafrost regions. In cold regions, underlying permafrost up to 14 m in depth experienced considerable cooling trends during the first five to sixth years after embankment construction. While in warm regions, the uppermost permafrost layer warmed after upwards movement of permafrost table, and underlying deep permafrost had no obvious cooling trends with time. Finally, differences in freezing and thawing seasons of, and differences in ground thermal regimes of cold and warm permafrost regions were investigated based on ground temperature from natural borehole. Then, the different cooling effects of CRE in two regions were interpreted based on these differences.