【作者】 张卫兵；

【导师】 谢永利；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2007， 博士

【摘要】 受自然条件和地理特点的制约,西部山区高等级公路建设中出现了大量的黄土高路堤。由此而引发的高路堤沉降变形问题始终备受学术界及工程技术人员的重视。本文在总结国内外研究现状的基础上,围绕黄土高路堤的沉降变形规律、沉降影响因素和沉降计算等问题,以三处典型黄土高路堤原位试验为依托,结合室内试验、离心模型试验及有限元仿真分析等手段开展了以下研究工作:1.路堤压实黄土蠕变特性研究。通过一维固结试验,研究压实黄土在各种情况下的次固结特性,探讨了固结状态、加载时间、加载比对压实黄土次固结系数的影响,揭示了次固结系数与压缩指数间的关系。试验结果表明,随着固结压力的变化,压实黄土的次固结系数表现出与当前应力状态有关的变化规律。当处于正常固结状态时,次固结系数近似为一常数,且次固结系数与压缩指数具有很好的相关性;而当超载预压处理后,次固结系数随超载比和超载作用时间不同而变化。其次,进行了不同压实度、不同含水量情况下一维蠕变试验,研究了高路堤填土在高应力下的流变特性,在Kelvin模型基础上得出了变形随时间和应力变化的计算模型。2.以三处黄土高路堤为载体,开展了黄土高路堤沉降原位试验研究。试验中通过布置沉降杯和压力盒等测试元件,对路堤施工及工后各过程中路堤横断面、填挖交界处,以及路堤填土层间土压力与位移的变化规律进行了现场实测和分析。并在此基础上对黄土高路堤的沉降组成进行了研究。3.借助离心试验手段,通过不同路堤断面形式,不同地形条件下的10组离心模型试验,着重对黄土高路堤沉降变过程、空间效应对沉降变形规律的影响及黄土高路堤的湿化特性进行了研究。分析了加载期与稳定期沉降变化规律及其构成变化,并与原位试验进行对比。4.基于MARC有限元软件,从填土高度、边坡形式、路堤与地基模量、模量比及填土泊松比等方面对路堤沉降的影响展开深入的探讨,并分析了各因素对高路堤沉降构成的影响。同时对空间效应的影响及路堤的湿化性状进行了数值仿真分析。结果表明,路堤沉降的组成除地基沉降外,主要是路堤自身的压缩变形量,而由填土高度、土体泊松比及路堤边坡形式等因素引起的侧向变形对路堤沉降也有较大的影响。空间效应对路堤沉降及土体应力分布产生一定影响,湿化将引起路堤局部应力水平的提高,从而产生边坡失稳。5.黄土高路堤自身压缩沉降计算及工后蠕变计算的研究。首先在一维分层总和法中引入压缩模量随填土应力变化时的修正表达式,使路堤沉降计算时能够考虑到不同土层压缩模量因填土荷载增加的变化的情况:其次针对高路堤填土变形的特性,提出了侧向变形影响的修正系数K表达式,使得高路堤沉降与路堤高度、边坡形式及填土特性建立了联系;最后结合室内试验成果给出了计算黄土高路堤工后蠕变沉降的实用计算方法。并将模型计算结果其与现场实测、模型试验及有限元计算结果进行了对比,验证了计算方法的可靠性。论文研究明确了黄土高路堤的沉降构成,分析描述了黄土高路堤的沉降变形及其发展变化特征,基本解决了黄土高路堤的沉降计算问题,对今后的设计和施工具有重要的指导作用。更多还原

【Abstract】 For restrained by its’ natural conditions and geographical characteristics, there are a lot of high loess- filled embankments welling up during the highway construction in west area. The issue on settlement -deformation of high loess-filled embankment aroused from above status has been paid more attention to by academic community and engineering technicians. In this dissertation, based on the present research situation and combining the field tests, experiment indoors, centrifuge model test and numerical simulation, the following research work focused on settlement and deformation laws, the influencing factors and its calculating method has been carried out.1. Research on creep characteristics of compacted loess. Firstly, based on a series of 1 -D consolidation test, the characteristics of secondary consolidation on compacted loess were studied and the influence of consolidation pressure, consolidation time, compression index and overload ratio on the coefficient of secondary consolidation were analyzed .The test results indicated that with the change of consolidation pressure, the coefficient of secondary consolidation shows a sound regularity with the variation of stress conditions. In normal consolidation state the coefficient remains approximately a constant value. But when surcharge preloaded, the coefficient will change with the overload ratio and its duration time. Also, under normal consolidation state, there is a significant correlativity between the coefficient of secondary consolidation and compression index and which has little influenced by overload ratio and its duration time. Secondly, the rheological characteristic of compacted loess under high stress has been studied after a series of 1 -D creep test with different degree compaction and water content. As a result, an empirical model of deformation varying with stress and time has been put forward.2. Relying on three typical high loess- filled embankment and through arranging testing component, the varying laws of settlement and earth pressure at transaction, the boundary between filling and digging and among the layers of filling have been measured and analyzed during the stage of construction and after that .At the same time, based on which, the composition of settlement for high loess- filled embankment has been studied.3. In virtue of centrifuge model test, through 10groups test simulating different section form and orographic condition, the laws of settlement -deformation and the wetting characteristic have been researched. Also, the composition of settlement during the stage of loading and holding is analyzed. Compared with the results of field tests and numerical simulation, the research achievement is enriched further more.4. Based on the large common finite element MARC programmer, the influence of settlement on high loess- filled embankment has been discussed in depth from the aspects of the filling height, the form of slope, deformation modulus of embankment and groundsill, modulus ratio and Poisson’s ratio. In the meantime, the influence on the composition of settlement suffering from above factors is analyzed. Also, the numerical simulation of the steric effect and the wetting properties on embankment has been worked, the results shows that apart from the foundation settlement, the amount of compressive deformation of embankment itself is a main component of settlement, meantime, which is influenceed by the lateral deformation caused by the height of filling, the Poisson’s ration and the form of slope .The steric effect has a great influence on distribution of settlement and stress of soil mass. Wetting will cause localized stress level enhance, consequently which can induce the slope collapse.5. Research on calculating method of creep settlement after construction and compression settlement for loess-high fill embankment itself. Firstly, a revised expression about the modulus of compressibility varying with stress is introduced to layer-wise summation method, which can consider the variation of modulus of compressibility with the increasing filling load on settlement calculation. Secondly, the expression about coefficient of correction K of lateral deformation is brought forward in view of the deformation characteristics of loess-high fill embankment, which can establish tiles between the settlement and the height, the form of slope and filling property. At last, combining the experiment indoors, an applied method of calculating creep settlement after construction for high-stacked embankment has been put forward. Through comparing the results using above method with model experiment and FEM calculation, the reliability of the method is verified.The research from the dissertation crystallized the composition of high loess-filled embankment, analysed and described the settlement -defoemation laws and its characteristics of variation and basicly solved the problem of settlement calculation of high loess-filled embankment, which can offer references to the design and construction for the future.更多还原