湿干循环条件下膨胀土开裂与渗透性能试验研究

发布时间：2019-04-25 13:34

【摘要】：膨胀土富含2μm的黏粒和强亲水性粘土矿物,密实时渗透性极低,水分难以入渗。而工程实际中,在大气湿干循环作用下,膨胀土中会产生大量裂缝,纵横交错的裂隙使得其渗透性大增,雨水入渗常引起路堑边坡成群坍滑破坏。为弄清膨胀土这一特殊工程性质,本文取南宁外环膨胀土为主要对象,室内模拟大气影响开展试验,探究湿干循环下不同密度的膨胀土开裂规律及其渗透性能。首先,比较了已有的裂隙定量化描述指标以及采集方法,确定用面裂隙率作为定量化描述裂隙的指标;利用数码相机拍摄采集试样表面裂隙,而试样内部断面裂隙则用ICT采集。尽可能模拟实际大气状况而设计了整个试验研究方案。严格按设定方案完成系列试验,获得湿干循环下试样表面、内部裂隙的开展及其渗透性变化的规律,表明ICT获得的SD值能较好的表征裂隙开展状况;湿干循环下裂隙开展及其渗透性变化与试样初始密度密切相关,试样密度增大,其裂隙开展及饱和渗透系数均变小;表面裂隙率与饱和渗透系数间呈良好对数关系;饱和渗透系数的绝对增长率随试样干密度而变化的曲线存在一峰值,当试样密度较峰值所对应干密度越大时,其绝对增长率越小,从而验证了膨胀土填筑施工时控制其干密度的必要性。为检验本文设计的试验方案和测试结果是否有代表意义,还选取广西百色和北京丰台两种膨胀土开展了对比分析试验,结果证明本研究的结论具有普遍性。最后,运用灰色关联理论分析了膨胀土密度、土性参数对裂隙开展及饱和渗透系数绝对增长率的影响程度,并探讨了湿干循环下膨胀土开裂及饱和渗透系数变化的原因。
[Abstract]:Expansive soil is rich in 2 渭 m clay and strongly hydrophilic clay minerals. The permeability of expansive soil is very low and water content is difficult to infiltrate. In engineering practice, a large number of cracks will occur in expansive soil under the action of atmospheric wet-dry circulation, and the permeability of expansive soil will be greatly increased by the crisscross cracks. Rain Water infiltration often results in the collapse failure of cutting slopes in groups. In order to make clear this special engineering property of expansive soil, this paper takes Nanning outer ring expansive soil as the main object, carries on the laboratory simulation atmosphere influence experiment, explores the expansive soil cracking law of different density under wet-dry cycle and the permeability of expansive soil. Firstly, the existing quantitative index of fracture description and collection method are compared, and the surface crack rate is determined as the quantitative index to describe the crack, and the sample surface crack is captured by digital camera, while the fracture of the inner section of the specimen is collected by ICT. The whole experimental research scheme is designed by simulating the actual atmospheric conditions as much as possible. A series of tests were carried out strictly according to the set scheme, and the rules of surface, internal crack development and permeability change under wet-dry cycle were obtained, which indicated that the SD value obtained by ICT could better characterize the crack development status. The fracture development and permeability change under wet-dry cycle are closely related to the initial density of the specimen, increase the sample density, decrease the crack development and saturation permeability coefficient, and the surface fracture porosity has a good logarithmic relationship with the saturated permeability coefficient. There is a peak value of absolute growth rate of saturated permeability coefficient with the dry density of the sample. When the density of the sample is larger than the corresponding dry density of the sample, the absolute growth rate of the sample is smaller. Therefore, it is necessary to control the dry density of expansive soil during filling construction. In order to test whether the test scheme and test results are representative, two expansive soils, Baise in Guangxi and Fengtai in Beijing, are selected to carry out comparative analysis tests. The results show that the conclusions of this study are universal. Finally, the influence degree of expansive soil density and soil parameters on crack development and absolute growth rate of saturated permeability coefficient is analyzed by using grey relational theory, and the causes of cracking and saturated permeability coefficient change of expansive soil under wet-dry cycle are also discussed.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU443

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