川西非饱和混合土动剪切模量和阻尼比分析

发布时间：2018-11-01 15:05

【摘要】：四川盆地西部山区地处青藏高原东缘,是我国境内地震灾害及地震造成的次生地质灾害频发地区,隶属于世界两大主要地震带之一的地中海-喜马拉雅山地震带系,该地区素来以地质构造复杂、地震频发著称。该地区广泛分布一种特有的崩坡积混合土,且在自然条件下常处于非饱和状态。本论文主要对川西非饱和混合土展开了动剪切模量和阻尼比分析。本论文完成的主要工作及获得的主要成果与结论如下：首先,对取自五个不同滑坡点的崩坡积混合土进行了常规物理力学性质试验,主要包括矿物成分分析、天然含水率、天然密度、土颗粒密度、土颗粒级配试验、界限含水率试验等。通过矿物成分、颗粒级配、液塑限等差异性比选选出了三种物性差异明显、有代表性的三种混合土(文中所列3号土、4号土和5号土,其细粒成分分别以粘土、粉土和粉质粘土为主)进行动力特性试验研究。其次,运用动三轴仪,模拟地震荷载作用下小变形范围内的三种混合土的动变形特性,采用Hardin-Drnevich双曲线模型、运用数学软件Mathematica拟合得到Gd/Gmax-yd和λ～yd等曲线。在拟合曲线的基础上,研究了饱和度、细颗粒含量、干密度、循环振动次数、固结比和振动频率等因素对川西混合土的动剪切模量和阻尼比的影响。尤其重点研究了饱和度和细颗粒含量的影响效果,发现随着饱和度的增加,川西混合土的动剪切模量减小、阻尼比增大；随着细颗粒含量最大粒径的增大,混合土的动剪切模量和阻尼比均增大。还将试验结果与文献值进行了比对。最后,对三种典型的川西混合土的动力特性试验数据分别按饱和状态和非饱和状态分组汇总,拟合各组汇总数据获得了三种土分别在饱和状态和非饱和状态下的动剪切模量比函数Gd/Gmax＝Gd/Gmax(yd)和阻尼比函数λ～λ(yd),给出了川西混合土的动剪切模量比和阻尼比的推荐值。该推荐值可作为该地区工程抗震设计和地震安全评估的参考值。
[Abstract]:The western mountainous area of Sichuan Basin is located in the eastern margin of the Qinghai-Xizang Plateau. It is a frequent area of earthquake disasters and secondary geological disasters caused by earthquakes in China. It belongs to the Mediterranean Himalayan seismic belt, one of the two major seismic zones in the world. The area has long been known for its complex geological structure and frequent earthquakes. A special sloping mixed soil is widely distributed in this area, and it is often in unsaturated state under natural conditions. In this paper, the dynamic shear modulus and damping ratio of unsaturated mixed soils in western Sichuan are analyzed. The main achievements and conclusions of this paper are as follows: firstly, the conventional physical and mechanical properties tests of caving mixed soil from five different landslide points are carried out, including mineral composition analysis, natural moisture content, and so on. Natural density, soil particle gradation test, limit moisture content test, etc. Through the difference of mineral composition, particle gradation and liquid plastic limit, three kinds of mixed soil were selected. The three kinds of mixed soil (soil No. 3, soil No. 4 and soil No. 5 listed in this paper) were composed of clay respectively. The dynamic characteristics of silt and silty clay are studied. Secondly, the dynamic deformation characteristics of three mixed soils in small deformation range under seismic load are simulated by using dynamic triaxial instrument. The Gd/Gmax-yd and 位 ~ yd curves are obtained by using Hardin-Drnevich hyperbolic model and mathematical software Mathematica. On the basis of fitting curves, the effects of saturation, fine particle content, dry density, cyclic vibration frequency, consolidation ratio and vibration frequency on the dynamic shear modulus and damping ratio of mixed soils in western Sichuan were studied. Especially, the effect of saturation and fine particle content is studied. It is found that with the increase of saturation, the dynamic shear modulus of mixed soil decreases and the damping ratio increases. The dynamic shear modulus and damping ratio of mixed soil increase with the increase of the maximum particle size of fine particle content. The experimental results were compared with those of the literature. Finally, the experimental data of dynamic characteristics of three typical mixed soils in western Sichuan are summarized according to the saturated state and unsaturated state, respectively. The dynamic shear modulus ratio function (Gd/Gmax=Gd/Gmax (yd) and damping ratio function 位 ~ 位 (yd), of three kinds of soils under saturated and unsaturated conditions were obtained by fitting the data collected in each group. The recommended values of dynamic shear modulus ratio and damping ratio of mixed soil in western Sichuan are given. The recommended values can be used as reference values for seismic design and seismic safety assessment of engineering in this area.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411

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