【作者】 邵玉芳；

【导师】 龚晓南；

【作者基本信息】 浙江大学 ， 岩土工程， 2006， 博士

【摘要】 含腐殖酸软土的加固是地基处理工程中提出的问题,同样涉及土壤固化技术的其它应用领域,如路基填筑、水系治理等。普遍认为软土中的腐殖酸通过阻碍水化反应,分解水化产物等,使水泥、石灰等固化材料几乎失效,但是含腐殖酸固化土特性的研究却未受到足够的重视,已有的研究成果很少且不尽相同,因此有必要深入地研究腐殖酸对土壤固化的作用机理,从而为含腐殖酸软土的加固提供依据。 在论述了土壤的固化机理、材料,以及腐殖酸的结构、性质的基础上,分析了腐殖酸对土壤固化的影响,其中富啡酸是由于其盐类还原能力和络合能力较强,易形成络合物,从而具有高度的吸附活性;胡敏酸是由于其所含官能团多,能解离出较多的氢离子,因此具有较强的离子交换能力。两种腐殖酸都能通过延缓水化反应、分解水化产物来影响土壤固化。 进行了含腐殖酸水泥固化土和OL-1固化土的强度影响试验,结果表明:胡敏酸对固化土强度的影响大于富啡酸,QL-1固化剂能显著改善胡敏酸的影响;水泥掺入比对QL-1固化土的影响较大,只有当水泥掺入比大于10%时,OL-1固化剂才表现出明显的增强效果;胡富比对两种固化土的影响都较小;含腐殖酸水泥固化土的强度随龄期的增长缓慢,而QL-1固化土的后期强度与早期强度相比有较大的提高。 通过四因子二次正交旋转组合试验研究了OL-1固化土各影响因子的显著程度及互作效应,结果表明,各因子显著性的排列次序是:胡敏酸含量>水泥掺入比>富啡酸含量>生石膏掺入比;富啡酸含量对固化土的早期强度影响较大,而胡敏酸含量对固化土的后期强度影响较大,随着龄期的增长,两种腐殖酸对固化土强度的影响逐渐减弱;较高的生石膏掺入比有利于提高含腐殖酸固化土的早期强度,而不利于其后期强度的增长。 通过扫描电镜试验,研究了含腐殖酸固化土各影响因子的作用机理,结果表明:富啡酸和胡敏酸含量较高时,固化土中的针状、网络状水化产物晶体不可见或很少;水泥掺入比太低时,即使是腐殖酸含量较低的土,其水化产物的生成也很少:当腐殖酸含量较高,而水泥掺入比较低时,生石膏掺入比对固化土几乎不产生影响。 通过固结不排水三轴剪切试验研究了含腐殖酸固化土的应力-应变关系,建立了一个本构模型,该模型摆脱了传统流动法则的束缚,经试验验证更加符合固化土的实际情况。 最后结合水系疏浚废土经固化后用作路基填料的两个工程,进行了土壤固化技术的应用研究。水系疏浚废土中一般含有机质,需要在固化剂中添加消除有机质影响的特殊成分或使用专门用于加固有机质土的土壤固化剂。两种含有机质的疏浚土,经改良后,均可用作地基填料;经估算,采用固化疏浚废土用作路基填料,比采用传统材料可以降低造价20%左右,不但解决了填料的来源,而且进行了废物利用,避免了废土的占地堆放及环境污染,是一种具有多种效益的方法。更多还原

【Abstract】 Firstly encountered in the practice of composite foundation, stabilization of humus-containing soft soil became a serious problem restricting the application of soil stabilization in many areas such as pavement construction, water system regulation, etc.. It is generally accepted that soil humus can prevent the hydration process and decompose hydrated products, thus depress the function of cement and lime stabilization. But study on the characters of stabilized humus-containing soil does not receive much attention except several preliminary yet inconsistent results. Further investigation is necessary to elucidate the mechanism, for the sake of providing a basis for humus-containing soft soil stabilization.Based on the discussion of mechanism, materials of soil stabilization and structure, properties of humus, influence of humus on soil stabilization is analyzed. Because of the strong reduction and complexation ability, fulvic acid can be easily formed into complex compounds that are active in adsorption. While humic acid has strong cation exchange ability because its numerous functional groups can dissociate plenty of H~+. Both of the two acids can affect soil stabilization by retarding hydration reaction and decomposing hydrated products.Unconfined compression tests were done to determine the strength variation induced by the various assumed factors affecting the strength of humus-containing cement stabilized soil and QL-1 stabilized soil. Results showed that the influence of humic acid is much more marked than that of fulvic acid, QL-1 stabilizer can dramatically alleviate the effect of humic acid; cement mixing ratio has major influence on QL-1 stabilized soil, QL-1 stabilizer is only effective when the cement mixing ratio is above 10%; the ratio between the amount of humic acid and fulvic acid has little influence on both stabilized soils; the strength of the cement stabilized soil does not increase dramatically by age, but it means much more for the QL-1 stabilized soil.Four main factors that affect the QL-1 stabilized soil were studied by quadratic rotation-orthogonal combination test, which reveals that the significance sort order is that humic acid content>cement mixing ratio>fulvic acid content>gypsum mixing ratio; fulvic acid has more influence on the short-term strength and humic acid the long-term strength, but the influence is decreased by age; higher gypsum mixing ratio is beneficial for the short-term strength but deleterious to the long-term strength of the stabilized humus-containing soil.SEM test shows that the higher the content of fulvic and humic acid, the less the spiculate and/or reticulate hydrated products in the stabilized soil system; when the cement mixing ratio is too low, there will be little hydrated products formed even with a low humus content; the gypsum mixing ratio has nothing to do with the strength of the stabilized soil when it is accompanied by high humus content and low cement mixing ratio.A constitutive?model, which gets rid of the restriction of the flow rule, was established using the data obtained from consolidated undrained triaxial test of the stabilized humus-containing soft soil. Calculated data by the model are in good agreement with the experimental data.Finally, the related soil stabilization technique was applied to treat dredged soft soil from water systems into roadbase filling. Dredged soils from water systems often contain humus, so only those stabilizers with special components to reduce the influence of humus can be effective. The two samples of dredged soils containing humus are successfully treated into roadbase filling; it is estimated that the construction cost using stabilized soil can be decreased by 20% compared with the traditional materials, and it has extra benefits to waste recovery and farmland protection.更多还原