【作者】 黄新恩；

【导师】 白晓红；

【作者基本信息】 太原理工大学 ， 岩土工程， 2010， 博士

【摘要】 在工程中污染可以引起地基土物理性质的改变,进而影响到水泥土地基强度的变化,导致建筑物失稳或破坏,因此研究污染对水泥土的影响非常重要,这已经成为环境岩土工程领域中的一个崭新课题,但是目前国内外的研究只是把实验室内配制的单一化学成份作为污染介质,这就与实际工程情况相距较远。鉴于此,本项目依托高等学校博士学科点项目、山西省回国留学人员科研项目、山西省青年科技研究项目支持,以从实际环境提取的生活污水和造纸厂污水为介质,采用普通硅酸盐水泥和矿渣硅酸盐水泥,制作了两种污染类型的水泥土试块:(1)把不同浓度的生活污水和造纸厂污水与粉质粘土拌合配制成污染土,然后与水泥搅拌形成水泥土,来模拟土体受地下水污染后搅拌形成的污染水泥土;(2)把水泥与未污染的粉质粘土搅拌形成的水泥土试块分别浸泡在生活污水和造纸厂污水中模拟水泥土桩搅拌形成后受到地下水的污染。同时考虑到传统方法对污染土研究的困难,在实验方法上引入了电阻率法,系统定量研究了各种污染类型和条件下水泥土无侧限抗压强度、电阻率、龄期、浓度、液塑性指标、污染物迁移、损伤等的变化规律,主要研究成果归纳如下:第一,研究了土体受不同浓度生活污水和造纸厂污水污染后液塑性指标的变化规律,基于污水的化学成份探讨了其发生变化的机理。第二,污染水泥土是一种特殊的电化学体系,在测试过程中必须考虑直流电的极化等电化学效应问题,通过试验并借鉴前人经验,提出了适合于水泥土单轴压缩试验同步测试电阻率的方法和简单装置。第三,系统研究了土体污染下水泥土的强度和电阻率特性。无论普通硅酸盐水泥土试块还是矿渣硅酸盐水泥土试块,在相同的污染液浓度下,其无侧限抗压强度和电阻率均随着龄期对数的增加而呈线性函数增大;在相同的龄期下,均随着污染液浓度的增加而呈指数函数减小。第四,系统研究了浸泡环境中水泥土的强度和电阻率特性。无论普通硅酸盐水泥土试块还是矿渣硅酸盐水泥土试块,在相同的污染液浓度下,其无侧限抗压强度和电阻率均随着龄期对数的增加而呈线性函数增大;在相同的龄期下,均随着污染液浓度的增加而呈指数函数减小。第五,在以上两种污染类型中,水泥土无侧限抗压强度都与其电阻率呈线性关系,可以据此推测和检测水泥土强度。第六,提出了基于污染液浓度和龄期的水泥土强度预测公式。第七,在分析污染介质在水泥土中迁移的三种形式基础上,建立了相应的离子迁移模型;通过研究水泥土微观结构图片,揭示了污染对水泥土的侵蚀机理,并建立了污染对水泥土的结构的影响模型图;提出腐蚀深度的概念,建立了污染物腐蚀水泥土的腐蚀深度数学模型。第八,根据硫酸根腐蚀水泥土的化学反应方程式,推导了单位体积水泥土中消耗硫酸根量的公式。第九,根据本次水泥土强度,提出了水泥土强度折减系数,并得出了本次试验的不同环境条件下水泥土抗压强度折减系数的统计值。第十,通过无侧限抗压强度实验过程中同步测试电阻率,以变形过程中有效电流与初始电流的比值描述损伤,建立了基于电流变化的水泥土损伤模型,此模型形式简单,特点是没有对应变分段,而是将全应变范围都统一成一个四次多项式方程,且与水泥类型、污染类型无关。并且对归一化后应力-应变曲线进行了拟合。该课题的研究对正确认识生活污水和造纸厂污水对水泥土复合地基的腐蚀性具有指导意义,为进一步研究这两种污水对水泥土复合地基的耐久性提供了试验资料,电阻率法的使用也改变传统方法对于污染地基土腐蚀性研究的困难,极大地扩展了电学方法在污染土中的应用,对于将电阻率法推广于环境岩土工程领域中具有重要的现实意义和广泛的应用前景。更多还原

【Abstract】 Pollution can change the physical properties of soil, further may affect the strength of soil-cement foundation, in turn, induce instability or disruption of buildings. Therefore, studying the effect of pollution on soil-cement has become more and more important which made it a new topic in the area of environmental geotechnical engineering. In recent years, most researchers just considered one single chemical component made in the lab as the polluted medium, which is far from the real engineering condition. Based on this, the sewage and industrial wastewater taken from the real environment were considered as the medium in this study. Two types of soil-cement samples were made of either normal Portland cement or slag Portland cement:(1) use different concentration’s sewage and industrial wastewater mixed with silty clay soil to form the contaminated soil, and then mixed with cement to form the soil-cement block to model the pollution of soil-cement with the soil polluted by groundwater; (2)After mixing the cement with the non-contaminated silty clay soil to form the soil-cement block, put the soil-cement blocks into the liquids with various concentraties of sewage or industrial wastewater to model the soil-cement column under the pollution of groundwater. Considering the difficulty of application of traditional method for the contaminated soil, the electrical resistivity method was introduced to investigate the soil-cement under different pollution types and conditions. The parameters studied in this study were included the unconfined compression strength, electrical resistivity, age, concentration, liquid and plastic limit indexes, transfer of contaminant, and damage and so on. The main achievements are as followed:Firstly, the law of liquid and plastic limit indexes of contaminated soil polluted by sewage and industrial wastewater with different concentration was studied. Also the change mechanism of contaminated soil based on the chemical compositions of polluted liquids was discussed.Secondly, as a special electrochemical system, electrochemical effect problems such as polarization of direct current should be considered during electrical resistivity measuring test. On a basis of test and previous experience, the method suitable for the synchronous testing electrical resistivity of soil-cement in uniaxial compression test was presented and a simplified device for electrical resistivity measuring was developed.Thirdly, the characteristic of strength and electrical resistivity of soil-cement under soil pollution was studied systematically. Under the same contamination concentration, no matter it was normal Portland cement sample or slag Portland cement sample, the unconfined compression strength and electrical resistivity were increased linearly with the increase of the logarithm of age; while under the same age, they were decreased exponentially with the increase of the contamination concentration.Fourthly, the characteristic of strength and electrical resistivity of soil-cement under soaking environment was studied systematically. Under the same contamination concentration, no matter it was normal Portland cement sample or slag Portland cement sample, the unconfined compression strength and electrical resistivity were increased linearly with the increase of the logarithm of age; while under the same age, they were decreased exponentially with the increase of the contamination concentration.Fifthly, in the above two pollution types, the unconfined compression strength of soil-cement had a linear correlation with electrical resistivity. This correlation may be used to predict and check the strength of soil-cement.Sixthly, a strength equation of soil-cement was proposed on the basis of the pollution concentration and age.Seventhly, under the analysis of three transferring types of contamination medium in soil-cement, the corresponding iron transferring model was built. By observing the microstructure images of soil-cement, the principle of pollution for soil-cement was revealed and the affection model diagram of pollution for soil-cement structure was found. Also the concept of erosive degree was presented and the erosive mathematical model of the contamination polluted soil-cement was built.Eighthly, the quantity equation of consumption of SO42- per volume was derived from the equation of SO42- erosive soil-cement.Nighthly, the modified coefficient of strength was proposed based on the strength testing date. And the statistic value of modified coefficient under different environmental conditions was obtained.Tenthly, according to the synchronous tested electrical resistivity in the unconfined compression strength test, using the ratio of effective current to the initial current during deformation to describe damage, the soil-cement damage model based on the current variation was built. This model with a simply form was no staged strain and unified all the strain range to a quartic polynomial equation independently with the types of cement and pollution.This study has a pronounced significance for understanding the erosive of sewage and industrial wastewater for the soil-cement composite foundation correctly, also gives a basis experiment date for the further research on the durability of soil-cement composite foundation. The application of the electrical resistivity method solvs the problem for the traditional method using in investigating erosive of contaminated soil and enlarges the application of electricity method using in the contaminated soil. This study also has a great practical significance and widely application prospects for the application of electrical resistivity method in the environment geotechnical engineering.更多还原