长江科学院院报 ›› 2020, Vol. 37 ›› Issue (1): 84-89.DOI: 10.11988/ckyyb.20180770

• 岩土工程 • 上一篇    下一篇

聚合氯化铝(PAC)改性膨胀土的胀缩特性试验研究

武雷杰, 杨秀娟, 张路, 樊恒辉, 严武庆   

  1. 西北农林科技大学 水利与建筑工程学院,陕西 杨凌 712100
  • 收稿日期:2018-07-21 出版日期:2020-01-01 发布日期:2020-01-21
  • 通讯作者: 樊恒辉(1973-),男,山西运城人,研究员,博士,主要从事特殊土工程性质及其改良技术研究。E-mail:yt07@nwsuaf.edu.cn
  • 作者简介:武雷杰(1991-),男,河北石家庄人,硕士研究生,主要从事特殊土工程性质研究。E-mail:18792727689@163.com
  • 基金资助:
    国家自然科学基金项目(51579215);杨凌示范区科技计划项目(2018NY-28)

Experimental Study on Swelling and Shrinkage of Polyaluminum Chloride (PAC) Modified Expansive Soil

WU Lei-jie, YANG Xiu-juan, ZHANG Lu, FAN Heng-hui, YAN Wu-qing   

  1. College of Water Resources and Architectural Engineering, Northwest A & F University,Yangling 712100, China
  • Received:2018-07-21 Online:2020-01-01 Published:2020-01-21

摘要: 膨胀土具有吸水膨胀和失水收缩的特性,容易引起上覆构筑物的破坏。通过颗粒分析试验、界限含水率试验、自由膨胀率试验、膨胀率试验、收缩试验和扫描电镜试验,对聚合氯化铝(PAC)改性膨胀土的物理与胀缩特性进行了研究,并与硅酸钠改性土对比。结果表明:掺入PAC的膨胀土,黏粒含量降低,亲水性减弱,液限降低,塑性指数显著下降;在一定掺量范围内,PAC改性后膨胀土的自由膨胀率、无荷膨胀率、有荷膨胀率、线缩率、体缩率等胀缩性指标降低;大量的絮状物通过填充土体中的孔隙与胶结土颗粒,使土体结构性得以改善。PAC改性膨胀土的机理在于其在水介质中可电离产生大量高价[Al]m+和[Alm(OH)n]3m-n絮凝物,这些生成物通过离子交换、电中和、架桥吸附和絮凝网捕作用,降低表面电荷,使黏土颗粒相互聚集,降低膨胀土的胀缩性。

关键词: 膨胀土, 聚合氯化铝, 硅酸钠, 胀缩性, 微观结构

Abstract: Expansive soil is prone to trigger destruction of overlying structures due to characteristics of water absorption expansion and water loss shrinkage. We examined the physical and expansive properties of polyaluminum chloride (PAC) modified expansive soil via particle analysis test, limit moisture content test, free expansion rate test, expansion rate test, shrinkage test and SEM test. Results demonstrated that the clay particle content, hydrophilicity, liquid limit and plasticity index of PAC modified expansive soil decreased; and also the expansion and shrinkage indicators, inclusive of free expansion rate, non-loaded expansion rate, loaded expansion rate, linear shrinkage rate and volumetric shrinkage rate, of PAC modified expansive soil all declined within a certain amount of PAC admixture. A large amount of flocculants improved the structure of soil by filling the pores of soil and cementing soil particles. The mechanism of PAC modifying expansive soil lies in a large number of high valence [Al]m+ and [Alm(OH)n]3m-n flocculants ionized in water medium, which could reduce surface charge by ion exchange, electric neutralization, cementing adsorption and flocculation enmeshment, so that clay particles gather together to lower the expansion and contraction of expansive soil.

Key words: expansive soil, polyaluminum chloride, sodium silicate, swell-shrink characteristic, microstructure

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