化学法改良膨胀土的试验研究

发布时间：2018-03-22 08:21

本文选题：膨胀土　切入点：化学改性　出处：《西北农林科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：膨胀土是一种高塑性粘土，因其显著的胀缩特性、多裂隙性和超固结性等不良工程特性而被归为一种特殊土。膨胀土遇水快速膨胀强度大大衰减，失水则快速收缩的变形特性给膨胀土地区的工程建设造成了很大的困难和损失。半个世纪以来，不同研究者们从不从角度解释了膨胀土的胀缩机理，并提出了相应改良膨胀土胀缩特性并加固膨胀土地基的方法，主要包括一些物理法和化学法。本文基于膨胀土的胀缩机理及有机物对粘土的吸附和改性作用，选用无机物硅酸钠（Na2SiO39H2O）、氯化钙（CaCl2）、氯化铝（AlCl36H2O）及氧化钙（CaO）与水溶性有机高分子聚合物阳离子型聚丙烯酰胺（CPAM）、阳离子型表面活性剂十六烷基三甲基溴化铵（HTAB）复配改良膨胀土。同时，参照土工试验规范，改进了自由膨胀率试验方法，以改性土的自由膨胀率测试结果作为衡量改性效果的指标，筛选出最佳改性配方，并测试最佳改性配方下改性土的变形和强度。将改性结果与5%掺量下的氧化钙改性土进行比较。取得如下研究成果：（1）试验方法上，膨胀土的自由膨胀率试验方法改进研究表明：土样的制备过程及试验环境对结果影响很大。土样的粒度组成、环境温度、土样冷却与否等因素均对最终的测试结果有一定影响，其中土样的粒度组成影响最大。根据研究结果提出以下建议：采用控制土样粒度组成的方法测试不同土样的自由膨胀率，将土样分为三个粒组：0~0.1mm、0.1mm~0.25mm、0.25mm~0.5mm，分别取对应粒组质量百分比为0%~20%：20%~50%：20%~50%的土组成测试土样；在同一环境温度下进行不同土样之间的对比试验；土样烘干后要在干燥箱中冷却保证其干燥程度。结果表明，不同改性土样自由膨胀率测试结果的可比性大大提高。（2）改性剂的筛选方面，，将不同掺量的无机物硅酸钠（Na2SiO39H2O）、氯化钙（CaCl2）和氯化铝（AlCl36H2O）掺入陕西安康膨胀土改性，自由膨胀率测试结果表明：硅酸钠的改性效果优于其他物质；再将三种无机物以不同掺量分别与不同掺量下的阳离子型聚丙烯酰胺和十六烷基三甲基溴化铵复配改良膨胀土，结果表明：硅酸钠与阳离子型聚丙烯酰胺的复合效果最好，十六烷基三甲基溴化铵单独改性效果亦十分良好。在陕西安康膨胀土中掺入占干土质量2.5%的硅酸钠和0.5%的阳离子型聚丙烯酰胺，改性后的土即可满足工程需要。（3）改性土的变形和强度试验结果表明：变形上，2.5%的硅酸钠和0.5%的阳离子型聚丙烯酰胺改性陕西安康膨胀土和陕西汉中膨胀土的线缩率、体缩率、无荷膨胀率等指标均较原土有较大的改善；强度上，改性土的粘聚力较原膨胀土有显著提高，并改善了素土的应变软化特征，与5%生石灰改性对比，虽然Na2SiO39H2O和CPAM改性土的凝聚力较低，但相较石灰改性土的应变软化趋势，Na2SiO39H2O和CPAM复合改性有很大的优势。（4）改性机理方面：高价的无机阳离子对膨胀土中低价阳离子的置换作用虽然可以降低膨胀土的亲水性，但这种作用相比某些无机物的凝聚作用和某些有机物的吸附凝聚剂表面改性作用还是很微小的。金属阳离子的存在会影响阳离子型聚丙烯酰胺对粘土的吸附作用，有机聚合物对土粒的的吸附作用与无机阳离子对土粒的晶格置换、团聚作用是可以相互配合的。表面活性剂对粘土颗粒表面活性的改变作用对改善膨胀土的亲水性十分重要，研究表明HTAB的改性效果十分显著。
[Abstract]:Expansive soil is a kind of high plastic clay, because of its remarkable swelling characteristics, fissures and over consolidation of poor engineering properties and is classified as a kind of special soil. The rapid expansion of the expansive soil strength greatly attenuated in water, the deformation characteristics of dehydrate, rapid contraction caused great difficulties and loss to the expansion the land area of construction project. For half a century, different researchers never explained from the angle of expansive soil swelling shrinkage mechanism, and puts forward the shrinkage characteristics and reinforcement methods of Expansive Soil Subgrade of expansive soil and corresponding improvement, including some physical and chemical methods.
In this paper, the expansive soil swelling shrinkage mechanism and adsorption of organic compounds on clay and modification based on the selection of sodium silicate inorganic compounds (Na2SiO39H2O), calcium chloride (CaCl2), aluminum chloride (AlCl36H2O) and calcium oxide (CaO) and water soluble organic polymer cationic polyacrylamide (CPAM), cationic surface active agent sixteen alkyl three methyl bromide (HTAB) compound modified expansive soil. At the same time, according to soil test specification, improved testing method for the rate of free expansion, with the modified soil free swelling ratio test results as a measure of modification effect indicators, selected the best modified formula, the optimum deformation and strength formula under the modified soil test results. And the modified calcium oxide and 5% dosage of modified bentonite were compared. The research results are as follows:
(1) test method, the expansive soil free swell test showed that the improvement of soil sample preparation process and test results of environmental impact. The soil particle size composition, temperature, soil and other factors are not the cooling of the final test results have certain effect, in which the particle size of soil samples the most important factor. Put forward the following suggestions: according to the results of the research methods used to control soil grain composition test of different soil samples free expansion rate, the soil sample was divided into three groups: 0~0.1mm, 0.1mm~0.25mm, particle 0.25mm~0.5mm, respectively corresponding grain quality percentage composition of the tested soil samples for 0%~20%:20%~50%:20%~50% soil; comparison test of different between the soil samples in the same environment temperature; soil samples after drying in the drying box cooling guarantee the drying degree. The results show that the modified soil free swelling ratio test results can be compared The sex is greatly improved.
(2) modified screening agent, the different content of inorganic sodium silicate (Na2SiO39H2O), calcium chloride (CaCl2) and aluminum chloride (AlCl36H2O) incorporation of Shaanxi expansive land reform, the free expansion rate test results show that the modified sodium silicate has better effect than other substances; then soil, expansion three kinds of cationic polyacrylamide with different inorganic admixture respectively with different dosage and sixteen alkyl three methyl bromide compound improved the results indicated that the best effect of compound sodium silicate and cationic polyacrylamide, sixteen alkyl three methyl bromide alone modification effect is also very good. In Shaanxi expansive cationic doping the quality of dry soil accounted for 2.5% and 0.5% of the sodium silicate soil modified polyacrylamide, after the soil can satisfy the need of engineering.
(3) the deformation and strength test results show that the deformation of the modified bentonite, cationic polyacrylamide 2.5% sodium silicate and 0.5% modification of Shaanxi expansive soil and Shaanxi Hanzhoung expansive soil shrinkage, shrinkage, free swelling ratio and other indicators were higher than the original soil has been greatly improved; strength, change soil cohesion than the original expansive soil is improved, and the improvement of the strain softening characteristics of soil, with 5% lime modified contrast, although Na2SiO39H2O and CPAM modified soil cohesion is relatively low, but compared to the strain softening trend of lime modified soil, Na2SiO39H2O and CPAM composite modified has a great advantage.
(4) modification mechanism: high price of inorganic cation replacement cation in soil while low expansion can reduce the hydrophilicity of the expansive soil, but this effect compared with the adsorption and condensation of some inorganic compounds and some organic coagulant surface modification effect is very small. The metal cations will affect the adsorption effect of cationic polyacrylamide on clay, organic polymer on the soil particles and the adsorption of inorganic cations on soil particle lattice replacement, aggregation can be matched with each other. To change the effect of surfactants on the clay particle surface activity is very important to improve the hydrophilicity of soil expansion, research shows that the modification effect of HTAB is very significant.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU443

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