受扰动后黏土地基强度变化规律研究

发布时间：2018-11-14 12:26

【摘要】：黏土地基受扰动后土体强度会发生衰减,严重时将导致建(构)筑物的破坏。由于扰动形式的多样性及土体所处环境的差异,使得黏土地基(包括固化黏土地基)受扰动后强度变化机理较为复杂。本文主要通过室内试验及理论分析对黏土受不同形式扰动后强度变化规律进行研究。通过施加等应变循环扭剪、单剪荷载对原状黏土进行扰动,得到土体受扰动后抗剪强度参数指标。得知黏土受循环荷载扰动后抗剪强度将有所折减,折减程度与荷载幅值、作用次数正相关;通过MATLAB编程对其微观图像定量分析,得知黏土受扰动后孔隙的数量、面积比、圆度增加,等效直径减小;利用灰色关联度分析动后黏土微-宏观参数,发现等效直径对宏观强度的影响最大,圆度次之,面积比其次,孔隙数量最小;最后,拟合得到受扰动后黏土静强度变化与微观参数之间的函数关系。通过室内动三轴试验开展水泥固化黏土动后强度研究。得知固化黏土受动应力σd扰动后无侧限强度qu会增大,且qu随σd的增大而增加;研究盐溶液对水泥土水化反应的影响,结果显示盐溶液试样的qu比正常试样高,但达到峰值所用时间少,盐溶液养护下试样的qu随龄期的增加而降低;利用电镜观察并通过LeicaQwin5000系统定量分析,试样受扰动后,孔隙的数量、面积比、等效直径会减小,而圆度、形态比会增大,清水试样受扰动后微观参数的绝对变化率比与盐溶液制样大。通过上述研究,总结扰动后黏土强度变化规律;提取影响动后黏土静强度的主要微观参数,并建立微-宏观参数的联系,为后续研究和实际工程提供技术支持与理论参考。
[Abstract]:When the clay foundation is disturbed, the strength of the soil will decrease, which will lead to the destruction of the building. Because of the diversity of disturbance forms and the difference of soil environment, the mechanism of strength change of clay foundation (including solidified clay foundation) after disturbance is more complex. In this paper, the strength variation of clay subjected to different forms of disturbance is studied through laboratory tests and theoretical analysis. By applying constant strain cyclic torsion shear and single shear load, the shear strength parameters of undisturbed clay are obtained. It is known that the shear strength of clay will be reduced when disturbed by cyclic load, and the reduction degree is positively related to the amplitude of load and the number of times of action. The quantitative analysis of microcosmic images by MATLAB shows that the number of pores, area ratio, roundness increase and the equivalent diameter decrease after the clay is disturbed. By using grey correlation degree to analyze the micro-macro parameters of the clay, it is found that the equivalent diameter has the greatest influence on the macroscopic strength, the roundness is the second, the area ratio is the second, and the number of pores is the smallest. Finally, the functional relationship between the static strength of the disturbed clay and the microscopic parameters is obtained by fitting. The post-dynamic strength of cement solidified clay was studied by dynamic triaxial test in laboratory. The results show that the unconfined strength qu will increase after dynamic stress 蟽 d disturbance, and the qu will increase with 蟽 d increasing. The effect of salt solution on the hydration reaction of cement soil is studied. The results show that the qu of the salt solution sample is higher than that of the normal sample, but the time to reach the peak value is less, and the qu of the sample decreases with the increase of age under the salt solution curing. Observed by electron microscope and quantitatively analyzed by LeicaQwin5000 system, the number of pores, area ratio and equivalent diameter will decrease, while roundness and morphology ratio will increase when samples are disturbed. The absolute change rate of the microscopic parameters after disturbance is larger than that of salt solution. Through the above research, the change rule of clay strength after disturbance is summarized, the main micro parameters which affect the static strength of clay after disturbance are extracted, and the relationship between micro and macro parameters is established, which provides technical support and theoretical reference for further research and practical engineering.
【学位授予单位】：中国民航大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU442

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