重塑土的动力特性及其对地震动的影响

发布时间：2018-09-07 10:49

【摘要】：地震会使地面发生震动甚至移动,并且经常伴随着地质灾害,其潜在的破坏力会对人们的生活造成严重影响。20世纪初,国内外学者通过对地震的研究发现,场地土层条件对地震动影响显著。随着大量震害资料的积累和理论研究的深入,证实了地震灾害的破坏程度与土的动力特性密切相关。土的动力特性是通过动剪切模量和阻尼比这两个参数来反映的,这两个参数也是土层地震反应分析和场地安评的关键。目前国内外对原状土的动剪切模量和阻尼比的研究已相对成熟,对重塑土动力学参数的研究成果相对较少。本文结合实际工程场地安全性评价项目,通过共振柱试验测定了粘土、粉质粘土、粉土和粉砂四类土的动力学参数,根据试验结果对比研究重塑土和原状土的动力特性及其对地震动的影响。1)通过对粘土、粉质粘土、粉土和粉砂四类重塑土和原状土分别进行共振柱试验,提出了重塑土与原状土的最大动剪切模量、动剪切模量比与剪应变关系曲线、阻尼比与剪应变关系曲线,确实存在差异。粉质粘土的最大动剪切模量相对差值的离散程度相对粘土、粉土和粉砂的离散程度要大些,总体来说,四种土的离散程度相差不大;粘土的动剪切模量比的相对差值的离散程度相对粉质粘土、粉土和粉砂的离散程度要大些。2)对影响重塑土和原状土的动力学参数异同的因素进行了分析。这些影响因素中,矿物成分的差异、结构性差异和试样尺寸的影响这三项较难控制;但粒组含量的差异、试验操作的影响以及制备试样的影响这三项在今后试验时可以进行改进,进而减少重塑土和原状土的动力学参数的差异。3)通过研究固结时间对粘土、粉质粘土、粉土和粉砂四类重塑土动力特性的影响,提出固结时间对重塑土的最大动剪切模量、动剪切模量比与剪应变关系曲线有影响,这种影响有明显的规律性。具体表现为重塑土的最大动剪切模量均随固结时间的延长而增大;动剪切模量比也均随固结时间的延长而增大。4)通过对三个理想剖面进行土层地震反应计算,对比分析重塑土和原状土的动剪切模量比对地表加速度峰值、地表加速度反应谱和地表反应谱特征周期的影响。动剪切模量比非线性部分不同,原状土值计算得到的平均地表加速度峰值大于重塑土值的计算结果,而原状土值计算的平均特征周期小于重塑土值的计算结果,并且由二者计算得出的地震动参数的相对差值随着土层厚度和震幅大小的变化而变化。
[Abstract]:Earthquakes make the ground shake or even move, and often accompanied by geological disasters, its potential damage will have a serious impact on people's lives at the beginning of the 20th century, scholars at home and abroad through the earthquake research found, The effect of soil conditions on ground motion is significant. With the accumulation of a great deal of seismic damage data and the deepening of theoretical research, it is proved that the damage degree of earthquake disaster is closely related to the dynamic characteristics of soil. The dynamic characteristics of soil are reflected by two parameters: dynamic shear modulus and damping ratio, which are also the key of soil seismic response analysis and site safety assessment. At present, the research on dynamic shear modulus and damping ratio of undisturbed soil has been relatively mature, and the research results on dynamic parameters of remolded soil are relatively few. In this paper, the dynamic parameters of clay, silty soil and silty sand are determined by resonance column test combined with the project of site safety evaluation. According to the experimental results, the dynamic characteristics of remolded soil and undisturbed soil and their effects on ground motion were studied. 1) Resonance column tests were carried out on four types of remolded soil and undisturbed soil, namely, clay, silty clay, silt and silt, respectively. The relationship curves of maximum dynamic shear modulus, dynamic shear modulus ratio and shear strain, damping ratio and shear strain of remolded soil and undisturbed soil are presented. The dispersion degree of the maximum dynamic shear modulus relative difference of silty clay is larger than that of clay, and the dispersion of silt and silt is larger than that of clay, generally speaking, the dispersion degree of the four soils is not different. The relative dispersion of the dynamic shear modulus ratio of clay is larger than that of silty clay, silt and silt. The factors affecting the dynamic parameters of remolded soil and undisturbed soil are analyzed. Among these influencing factors, the difference of mineral composition, the structural difference and the influence of sample size are difficult to control, but the difference of granulation content, The influence of test operation and the effect of sample preparation. These three items can be improved in future tests, thus reducing the difference in dynamic parameters between remolded soil and undisturbed soil. 3) by studying the effect of consolidation time on clay and silty clay, The effect of consolidation time on the maximum dynamic shear modulus, the ratio of dynamic shear modulus to shear strain curve of remolded soil is proposed, and the influence of consolidation time on the dynamic characteristics of remolded soil is obvious. The results show that the maximum dynamic shear modulus of remolded soil increases with the extension of consolidation time, and the dynamic shear modulus ratio increases with the extension of consolidation time. The effects of dynamic shear modulus ratio of remolded soil and undisturbed soil on the peak acceleration of the surface, the response spectrum of the surface acceleration and the characteristic period of the surface response spectrum are analyzed. The dynamic shear modulus is different from the nonlinear part. The peak value of the ground acceleration calculated by the undisturbed soil value is larger than that of the remolded soil value, while the average characteristic period of the undisturbed soil value is smaller than that of the remolded soil value. The relative difference of ground motion parameters calculated by the two methods varies with the thickness of soil layer and the magnitude of earthquake.
【学位授予单位】：黑龙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU435

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