饱和砂土小应变动力特性试验研究

发布时间：2018-01-08 20:28

本文关键词：饱和砂土小应变动力特性试验研究　出处：《浙江大学》2014年博士论文　论文类型：学位论文

【摘要】：土体的动力特性作为岩土工程问题分析设计的重要问题,不仅在地震场地分析、机械基础设计等土体动力问题分析中具有关键作用,在某些静力变形分析中亦具有重要作用。土体的动力特性影响因素众多,以往的研究结果存在较多矛盾和不足。本文在总结以往研究成果基础上,以土体的小应变动力特性为研究对象,采用弯曲-伸缩元测试系统,共振柱测试系统,动三轴试验系统联合进行了土体小应变动力特性研究,首先介绍了弯曲-伸缩元联合测试的测试原理,重点研究了饱和程度、弥散性、土体组构和循环应力历史对砂土小应变动力特性的影响,具体研究内容如下： (1)对弯曲-伸缩元的构造组成、连接方式及联合测试原理进行了详细的介绍,填补了国内弯曲-伸缩元联合应用的空白。采用不同方法宽区段激振频率,深入分析了接收波形及准确确定剪切波压缩波传播时间的影响因素,得到了可靠的剪切波压缩波传播时间确定方法。应用弯曲-伸缩元联合测试剪切波速和压缩波速,得到土体剪切模量和侧限模量及泊松比,分析了围压和密实度对泊松比的影响,为了方便工程计算,建立了泊松比与剪切模量相关关系。 (2)由于不同研究者试验得到的Vp与B值关系具有较大的离散性,因此有必要对Vp与B值关系的各影响因素进行深入的研究。在本文研究中,采用了三种级配不同的砂土,考虑了孔隙水类型,密实度,颗粒级配对Vp-B值关系曲线的影响,并对试验结果进行合理的机理解释。 (3)对两种洁净砂和两种天然砂进行了不同围压不同密实度的饱和试样弯曲元与共振柱对比试验研究,并通过剪切波速的弥散性对饱和砂土弯曲元与共振柱试验结果的偏差进行解释。为进一步对细粒含量及渗透系数对饱和砂土弯曲元测试的影响,对不同细粒掺量的饱和南京砂进行了弯曲元与共振柱对比试验研究。本文的试验结果为饱和砂土弯曲元小应变剪切模量测定提供了有效的方法和建议。 (4)采用两种常用的重塑砂土制样方法得到不同初始组构的饱和试样,通过弯曲元测试系统和共振柱测试系统分别对不同组构的饱和砂土试样进行剪切模量和阻尼的测试并进行了对比研究。将本文的研究成果与已有研究成果进行对比分析,从微观角度对试验结果进行了机理解释。 (5)采用动三轴与弯曲元联合测试系统,对饱和砂土在排水条件下进行循环加载,以研究循环荷载应力历史对其小应变动力特性的影响。并对不同初始平均主应力值、不同初始偏应力值、不同应力幅值、不同组构各因素进行了研究。上述研究成果显示：一方面,土体的动力特性参数(小应变剪切模量、阻尼、泊松比等)的影响因素众多,尽管以往已进行了大量的研究,但仍存在大量问题需要深入研究,本文的研究成果有助于人们深入了解砂土动力特性的影响因素及影响机理。一方面,弯曲元和伸缩元是一种快速方便的动力特性参数测试手段,本文的研究成果为弯曲元和伸缩元进一步广泛的应用及动力特性参数的准确测试提供了有力的理论支撑。
[Abstract]:The dynamic characteristic of soil is an important problem in the analysis and design of geotechnical engineering problems . It plays a key role in the analysis of soil dynamic problems such as seismic site analysis and mechanical foundation design . ( 1 ) The structure composition , connection mode and joint test principle of the bending - telescopic element are introduced in detail to fill the blank of the joint application of the domestic bending - telescopic element . The influence factors of the wave propagation time of the shear wave are analyzed deeply by using different methods . The influence factors of the shear wave velocity and the compression wave velocity of the shear wave are analyzed in depth . The influence of confining pressure and compactness on the Poisson ' s ratio is obtained . In order to facilitate the engineering calculation , the relation between Poisson ' s ratio and shear modulus is established . ( 2 ) Because the relationship between Vp and B value obtained by different researchers has great discreteness , it is necessary to study the influencing factors of the relationship between Vp and B value . In this paper , three different kinds of sand soil are adopted , the influence of pore water type , compactness and particle size matching Vp - B value curve is considered , and the reasonable mechanism explanation is made on the experimental results . ( 3 ) The comparison tests of saturated sand and resonant columns with different compaction degrees were carried out on two kinds of clean sand and two natural sand , and the deviation between the bending element of saturated sand and the resonant column was explained by the dispersion of shear wave velocity . ( 4 ) Two kinds of saturated samples with different initial textures were obtained by using two kinds of commonly used sand - making methods , and the shear modulus and damping of saturated sand samples with different fabrics were tested by bending element test system and resonant column test system . The results of this paper were compared with the existing research results , and the experimental results were explained from the microscopic angle . ( 5 ) Using dynamic triaxial and bending element joint test system , cyclic loading of saturated sand under drainage condition is carried out to study the influence of cyclic loading stress history on its small strain dynamic characteristics . The research results show that , on the one hand , the influence factors of dynamic characteristic parameters ( small strain shear modulus , damping , Poisson ' s ratio , etc . ) of soil mass are numerous , although a lot of research has been carried out in the past , many problems need to be studied deeply .

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU441;TU411

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