【作者】 高飞；

【导师】 张豫川；

【作者基本信息】 兰州大学 ， 土木工程·岩土工程， 2019， 硕士

【摘要】 随着我国经济的发展,黄土地区出现了大量的高填方工程。此类工程能够拓展城市建设用地,加快基础设施的建设。然而大规模的削山造地带来了众多高填方工程问题,填土的沉降变形使得填方形成的超大填筑体工后沉降、不均匀沉降甚至失稳等危害非常显著,许多已完成的填土工程的潜在隐患近年来逐渐显现。为探求黄土高填方地基的沉降规律,本文通过室内试验与数值模拟进行了较为全面的相关研究,为解决此类工程问题提供一定的参考依据。本文通过一维固结试验对不同含水率、不同压实度、不同荷载下压实黄土的变形规律进行研究,分析压实黄土变形达到稳定所需时间,并且采用不同的模型对压实黄土的应变时间关系进行拟合。然后,通过填方体室内模型试验研究一次加载和分级加载两种工况下填方的沉降和压力变化规律,使用image J软件对沉降过程中的孔隙变化等微观指标进行量化分析。通过数值模拟对黄土的施工期沉降及工后沉降进行模拟,分析工后沉降随含水率、压实度、填方高度的变化规律。最后分析高填方沉降影响因素,提出相应的控制措施。结果表明,压实黄土一维固结试验曲线大致分初始变形、变形减缓及变形稳定三个阶段;当初始状态相同时,随着荷载的增加,压实黄土土体变形达到稳定所需时间也会相应地增加;Burgers模型能很好地反映各级荷载作用下土体一维固结变形和时间的关系,可以作为压实黄土土体变形的模型。一次加载和分级加载两种工况下,填方土体沉降表现出相同的“三阶段”规律,一次加载时填方土体稳定时的沉降大于分级加载时的沉降,但分级加载条件下稳定时间较长;随着龄期的增加,土颗粒间排列逐渐趋于紧密,土样孔隙主要为镶嵌孔隙,土体结构更为密实。高填方施工期中心处沉降大,两侧沉降小,两侧沉降以中间轴对称分布;在一定范围内,减小含水率、增大压实度和降低填方高度能减小黄土高填方地基的工后沉降。更多还原

【Abstract】 With the development of China’s economy,a large number of high fill projects have appeared in the loess area.These projects can expand urban construction land and speed up infrastructure construction.However,large-scale mountain-cutting and earth-shaping bring many high fill engineering problems.The settlement and deformation of fill make some hazards very obvious,such as the post-construction settlement of the super-large fillings,uneven settlement,and even instability of the super-large fillings formed by filling.The potential hidden dangers of many completed fill engineering have gradually emerged in recent years.In order to explore the settlement law of loess high fill foundation,this paper has carried out a relatively comprehensive related research through laboratory tests and numerical simulation,and has provided some reference basis for such engineering problems.Through one-dimensional consolidation test,the creep law of compacted loess under different moisture content,different compactness and different loads is studied;time required for compacted loess to reach settlement stability is analyzed;different models are adopted to fit the strain-time relationship of compacted loess.Then,through indoor model tests,laws of settlement and the variation of earth pressure of fill under two working conditions of one-time loading and graded loading are studied;and microscopic indexes such as pore change in settlement process of are quantified and analyzed by using image J software.The parameters obtained from the above tests are used to simulate the settlement of loess during construction and the settlement after construction;the variation law of settlement after construction with water content,compactness,and fill height is analyzed.Finally,the influencing factors of high fill settlement are analyzed and corresponding control measures are put forward.The result shows that the one-dimensional consolidation curve of compacted loess roughly presents three stages of initial deformation,deformation mitigation and steady deformation.When the initial state is identical,with the increase of load,the time required for the deformation of compacted loess soil to reach stability will correspondingly increase.Burgers can well reflect the relationship between the one-dimensional consolidation deformation of soil under various loads and time,and it is suitable for being used as a creep deformation model of compacted loess soil.The settlement of the fill soil shows the same “three-stage” rule under the two working conditions of one-time loading and graded loading.The settlement of the fill soil under one-time loading is larger than that under graded loading.However,the stabilization time under graded loading is longer.With the increase of age,the arrangement of soil particles gradually tends to be close.The pores of soil sample are mainly embedded pores,and the structure of soil is closer.During the construction period of high fill,the settlement at the center is large,while the settlement at both sides is small,and it is evenly distributed symmetrically in the middle axis.In a certain range,reducing the water content,increasing the compaction degree and reducing the fill height can reduce the post-construction settlement of loess high fill foundation.更多还原