生物基土壤固化剂加固土的影响因素及其作用机理研究

发布时间：2018-06-13 21:13

本文选题：生物岩土工程 + 黄土　；参考：《西北农林科技大学》2015年硕士论文

【摘要】：黄土广泛分布于我国山西、陕西、甘肃等黄土高原地区,由于含有大孔隙结构且富含碳酸盐等成分,遇水产生崩解,水稳性较差。因此,黄土地区的地基、渠道等工程通常需要进行加固处理。本文选用木质素类高分子化合物、水泥、蜗牛生物体等单一组分或多个组分为加固材料,以杨凌黄土和延安黄土为试验对象,研究分析固化材料种类、掺量与养护龄期等因素对土体抗压强度和水稳性的影响,并对木质素固化黄土的抗压强度、抗剪强度、渗透性和水稳性等工程性质进行研究。最后,通过分析土体加固前后物理化学性质、微观结构特征及物质成分的变化,探讨木质素磺酸钙加固黄土的固土机理。研究结论如下。(1)低掺量木质素磺酸钙能够提高水泥土的早期强度,但长期强度逐渐降低;木质素磺酸钙对高掺量水泥加固土体有抑制作用,因此木质素磺酸钙不适合与高掺量水泥配合使用。(2)木质素磺酸钙与蜗牛生物体复合加固土浸水后的强度损失率大大降低,并且随着养护时间的增长,固化土抗压强度的损失率越来越低。说明木质素磺酸钙与蜗牛生物体的掺入降低了土体对水分的敏感性,耐水性能得到改善。(3)木质素磺酸钙可提高土体的抗压强度,降低渗透性,因而可改善黄土的工程性能;随着掺量的增加,固化土的抗拉强度、抗剪强度指标先增大后减小,渗透系数呈下降趋势。木质素磺酸钙适宜掺量在1.0%左右,养护时间至少在7d以上,含水率略低于最优含水率,应尽量增大固化土的密度。对于不同类型的土体,木质素掺量可能存在不同的最优掺量。(4)通过测定土体加固前后的物理化学性质,试验表明木质素磺酸钙掺入土中后土体的碱性增强;液限明显降低,塑限基本不变或者相对于液限来说变化幅度较小,从而导致塑性指数有所降低;土中的黏粒含量增大。(5)木质素磺酸钙掺入黄土中,使土体的强度提高、水稳性改善、渗透性降低。其作用机理主要表现在,一方面通过分散与联接作用使土颗粒重新排列,另一方面具有填充孔隙的作用。另外,通过其亲水基与黏土颗粒表面上金属阳离子所形成的化学链作用,木质素吸附于在黏土颗粒的表面,疏水基围绕着黏土颗粒表面形成油性层,对黏土颗粒表面的水有一定的排挤作用,并阻止水分进入。这几方面的综合作用使得土颗粒间的黏结力与分子力提高,孔隙减小,土体的整体性增强。
[Abstract]:Loess is widely distributed in the Loess Plateau of Shanxi, Shaanxi, Gansu and other regions of China. Because of its macroporous structure and rich carbonate composition, the loess collapses in water and its water stability is poor. Therefore, the loess area foundation, canal and so on engineering usually needs to carry on the reinforcement treatment. In this paper, lignin macromolecular compounds, cement, snail organism and other single or multiple components are selected as reinforcement materials. The Yang Ling loess and Yan'an loess are taken as experimental objects to study and analyze the kinds of solidified materials. The influence of the content and curing age of soil on the compressive strength and water stability of soil is studied. The engineering properties such as compressive strength, shear strength, permeability and water stability of lignin cured loess are studied. Finally, through analyzing the changes of physical and chemical properties, microstructure and material composition of soil before and after reinforcement, the mechanism of strengthening loess with calcium lignosulfonate is discussed. The results are as follows: (1) low content of calcium lignosulfonate can improve the early strength of cement soil, but the long-term strength decreases gradually, and calcium lignosulfonate can restrain the soil reinforced with high content of cement. Therefore, calcium lignosulfonate is not suitable to be used in combination with high content cement. (2) calcium lignosulfonate and snail biological composite reinforcement soil after immersion greatly reduce the strength loss rate, and with the increase of curing time, The loss rate of compressive strength of solidified soil is lower and lower. The results show that the incorporation of calcium lignosulfonate and snail organism reduces the water sensitivity of soil, and the water resistance is improved.) calcium lignosulfonate can increase the compressive strength and reduce the permeability of the soil, thus improving the engineering properties of loess. The tensile strength, shear strength index and permeability coefficient of the solidified soil increased firstly and then decreased with the increase of the content. The suitable amount of calcium lignosulfonate is about 1.0%, the curing time is more than 7 days, the moisture content is slightly lower than the optimal moisture content, the density of solidified soil should be increased as much as possible. For different types of soil, there may be different optimal content of lignin. 4) by measuring the physical and chemical properties of soil before and after reinforcement, the experimental results show that the alkalinity of soil is enhanced and the liquid limit is obviously reduced after the addition of calcium lignosulfonate into soil. The plastic limit is basically unchanged or the variation range is small relative to the liquid limit, which leads to the decrease of the plasticity index, and the increase of clay content in soil, the addition of calcium lignosulfonate into loess, the increase of soil strength and the improvement of water stability. Permeability is reduced. The main mechanism is that, on the one hand, soil particles are rearranged by dispersion and connection, and on the other hand, they are filled with pores. In addition, lignin is adsorbed on the surface of clay particles through the interaction of hydrophilic groups with the chemical chains formed by metal cations on the surface of clay particles, and hydrophobic groups form an oily layer around the surface of clay particles. The water on the clay particle surface can be squeezed out to some extent, and prevent the water from entering. The combination of these factors makes the adhesion and molecular force between soil particles increase, the porosity decreases, and the integrity of soil is enhanced.
【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】：2015
【分类号】：TU444

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