兰州大学机构库 >土木工程与力学学院
含盐量对固化硫酸盐渍土强度特性的影响
Alternative TitleEffect of Salt Content on Strength Characteristics of Solidified Sulphate Saline Soil
贾梦雪
Thesis Advisor吕擎峰
2017-05-31
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword硫酸盐渍土 固化 含盐量 抗压强度 机理
Abstract

含盐量对固化盐渍土固化剂的类型和掺量有较大的影响,但是目前对于硫酸盐渍土的固化研究都是针对一定的含盐量进行的,对其一般性规律研究较少。本文为研究因硫酸盐含盐量变化而引起的固化硫酸盐渍土力学性质变化规律,选用石灰粉煤灰、水玻璃、石灰粉煤灰水玻璃三种方案固化硫酸盐渍土,通过无侧限抗压强度试验研究固化硫酸盐渍土的抗压强度随含盐量变化的规律,并采用界限含水率试验、X射线衍射(XRD)试验、傅里叶变换红外光谱(FTIR)分析和物理吸附试验研究不同含盐量固化土的稠度特征、物相特征、化学成分和微观结构特征,探讨了含盐量对固化硫酸盐渍土抗压强度影响的机理。

(1)石灰粉煤灰固化不同含盐量硫酸盐渍土的无侧限抗压强度试验结果显示:①同一含盐量下,当含盐量小于2.8%时,固化土的无侧限抗压强度随石灰含量的增加先增大后减小,峰值点石灰含量9%;当含盐量大于等于2.8%时,固化土的无侧限抗压强度随石灰含量的增加而非线性增大。②同一石灰掺量下,随着含盐量的增加,固化土的无侧限抗压强度先增大后减小,峰值点含盐量为1.8%。土中含有一定量的SO42-有利于提高石灰粉煤灰固化土的抗压强度,强度增长机理:一方面SO42-在Ca2+的作用下与粉煤灰中的活性Al2O3反应生成致密且强度较高的钙矾石,另一方面硫酸盐作为碱激发剂激发粉煤灰活性,活性SiO2和Al2O3与Ca(OH)2发生火山灰反应生成更多的水化硅酸钙凝胶和水化铝酸钙凝胶,提高了固化土的强度。

(2)水玻璃固化不同含盐量硫酸盐渍土的无侧限抗压强度试验结果显示:随着含盐量的增加,固化土的无侧限抗压强度总体呈现下降趋势。含盐量增加到2.3%时,一方面硫酸钠会在固化土试样内结晶形成芒硝晶体,由于芒硝晶体体积是无水硫酸钠的4.18倍,其大量的形成会挤压固化盐渍土试样,使其体积剧烈膨胀,产生微细裂纹,从而导致固化土样结构的破坏;另一方面Na2SO4解离出Na+,使得硅酸胶粒周围的Na+浓度增大,加速了硅酸的聚合,促使其凝胶化,降低了水玻璃固化土内部的粘结强度,从而导致水玻璃固化盐渍土的无侧限抗压强度下降。

(3)二灰和水玻璃固化不同含盐量硫酸盐渍土的无侧限抗压强度试验结果显示:随着含盐量的增加,固化土的无侧限抗压强度先增大后减小,峰值点含盐量为1.8%。二灰和水玻璃固化土的抗压强度随含盐量变化的规律与石灰粉煤灰固化土的大体一致。

Other Abstract

The salt content has a great influence on the type and content of the curing agent in the solidified saline soil, but the research on the curing of the sulphate saline soil is carried out for certain salt content and its general law is less. The purpose of this paper is to study the change law of mechanical properties of the solidified sulphate saline soil caused by the change of sulfate salt content, the lime-fly ash, sodium silicate, lime-fly ash and sodium silicate are selected to solidify sulphate saline soil. The unconfined compressive strength test was conducted to research the variation law of the compressive strength of the solidified sulphate saline soil with the change of salt content. Also, limit moisture content, X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and physical adsorption tests were carried out to reaearch the consistency characteristics, phase characteristics, chemical composition and microstructure of the solidified soil with different salt content and discuss the mechanism of the effect of salt content on compressive strength.

(1) The results of unconfined compressive strength test of sulphate saline soil with different salt content solidified by lime-fly ash are shown as: ①Under the same salt content, the unconfined compressive strength of the solidified soil increases firstly and then decreases with the increase of lime content when the salt content is lower than 2.8%, and peak strength corresponds to a lime content of 9%. but the strength of solidified soil increases with the increase of lime content when the salt content is higher than 2.8%. ②Under the same lime content, the unconfined compressive strength of solidified soil increases firstly and then decreases with the increase of salt content, and peak strength corresponds to the salt content of 1.8%. A certain amount of SO42 in the soil is benefit to improve the compressive strength of the soil solidified by lime-fly ash, the strength growth mechanism: on the one hand, under the action of Ca2+, high strength and dense ettringite is produced by the reaction of SO42- and activated alumina in the fly ash, on the other hand, sulphate stimulates the activity of fly ash as a base activator and the pozzolanic reaction of active SiO2 and Al2O3 with Ca(OH)2 produces more hydrated calcium silicate gel and hydrated calcium aluminate gel, so it improves the strength of the solidified soil.

(2) The results of unconfined compressive strength test of sulphate saline soil with different salt content solidified by sodium silicate are shown as: The unconfined compressive strength of the solidified soil shows a decreasing trend with the increase of salt content. When the salt content increases to 2.3%, on the one hand, the mirabilite crystal will be formed in the solidified soil samples, as the mirabilite crystal volume is 4.18 times the sodium sulphate anhydrous, the formation of a large number of mirabilite crystal will extrude solidified sulphate saline soil samples so that the volume of samples swell intensely resulting in micro-cracks, so the destruction of  structure will appear; on the other hand, Na+ is dissociated from Na2SO4 so that the Na+ concentration increases around colloidal silicate. It accelerates the polymerization of colloidal silicate to promote its gelation so that the bond strength of the soil solidified by sodium silicate is reduced, resulting in the decrease in unconfined compressive strength of the saline soil solidified by sodium silicate.

(3) The results of unconfined compressive strength test of sulphate saline soil with different salt content solidified by lime-fly ash and sodium silicate are shown as: the unconfined compressive strength of solidified soil increases firstly and then decreases with the increase of salt content, and peak strength corresponds to the salt content of 1.8%. The change law of compressive strength of lime-fly ash and sodium silicate solidified soil with salt content is approximately the same as that of lime-fly ash solidified soil.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226379
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
贾梦雪. 含盐量对固化硫酸盐渍土强度特性的影响[D]. 兰州. 兰州大学,2017.
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