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蒙脱石在酸碱条件下的力学效应
Alternative TitleThe Mechanical Effects of Montmorillonite under Acid or Alkaline Conditions
Language中文
刘剑
Thesis Advisor崔鹏
2015
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline岩土工程
Keyword水土化学作用 蒙脱石 胶结物 水化硅酸钙 粘聚力模型
Abstract近些年来,我国地质灾害频繁发生,严重威胁广大人民群众的生命财产安全,也给人们的生产生活带来了极大的负面影响。滑坡是比较常见的一类地质灾害,尤以土质滑坡为甚,对其诱发因素的认识,目前已基本达成共识,大致有降雨、地震、火山活动、工程活动等或上述因素之间的耦合作用。其中,降雨是最常见、最主要的诱发因素。很多研究表明,降雨诱发滑坡的作用主要体现在降水下渗过程中转化而成的地下水与土体之间的相互作用,即水土相互作用(water-soil interaction,简称WSI)。 水土相互作用主要分为两类:水土之间的物理力学作用以及水土化学作用。长期以来,岩土领域的研究人员将目标主要集中在前者,如孔隙水压力、基质吸力、有效应力等等;而对后者的力学效应则往往视而不见,尽管水土化学作用早已引起部分学者的注意,但对它的研究和重视程度依然是比较低的。 本论文以典型粘土矿物蒙脱石为胶结物,配制了蒙脱石-石英砂重塑土,研究了在野外滑坡孕育温度(15℃、20℃、25℃)条件下,重塑土与超纯水、pH=3HNO3、pH=13.5NaOH溶液(模拟正常水体、酸雨、碱性废液)作用后的粘聚力变化情况,并通过X衍射,从矿物成分变化的角度,对粘聚力变化的机理进行了深入分析。此外,为实现定量描述水土化学作用下的粘聚力变化,本论文深入分析了土体粘聚力产生的本质原因,建立了基于粘土矿物胶结微观性质的饱和蒙脱石-石英砂重塑土粘聚力计算模型,并在水土化学作用机理的基础上,初步实现了该作用下的粘聚力变化计算。 通过实验研究和深入分析,本论文取得了以下结论: (1)超纯水条件下,电导率EC表现为逐渐上升,浸泡液pH也逐渐上升,最终表现为弱碱性,粘聚力表现为先上升后下降再上升。硝酸条件下,浸泡液pH逐渐上升,电导率EC总体表现为降低,粘聚力表现为先下降后上升再下降。氢氧化钠条件下,浸泡液pH和电导率EC均表现为持续下降,但后期逐渐减缓,粘聚力表现出先下降后上升再下降的特征,后期出现反弹。 (2)温度对超纯水中蒙脱石的消耗促进有限,但对硝酸与蒙脱石之间的化学反应有较大促进作用。在强碱溶液与蒙脱石之间化学反应的前期,温度有较大 促进作用,后期效果不明显。 (3)硝酸会溶蚀蒙脱石,导致土体粘聚力降低,浸泡中期粘聚力增大的机理尚不明确。超纯水和碱性条件下均生成了沸石类矿物和胶结物水化硅酸钙(CSH)。超纯水条件下,还有胶结物碳酸钙(CaCO3)生成。这些新生胶结物的胶结键强度远大于相邻蒙脱石层组间的结合力强度,是上述两种条件下粘聚力增大的原因,化学溶蚀和离子交换是粘聚力减小的主要原因。 (4)超纯水条件下,土体抗剪强度总体变化不大;酸性条件下,土体抗剪强度变化与粘聚力变化一致;碱性条件下,土体抗剪强度表现为总体增大。 (5)在综合考虑了水作用的基础上,基于蒙脱石胶结微观性质,构建了饱和蒙脱石-石英砂重塑土的粘聚力定量模型,并结合粘聚力变化机理,建立了水土化学作用下的粘聚力变化定量计算模型。模拟结果较好。
Other AbstractIn recent years, more and more geological disasters occurred in our country, these hazards had threaten many people’s lives and property seriously, and brought greatly negative effect on human’s living and production. Soil landslide was one common type of geological disaster. And researchers had reached a consensus to the causative factors about soil landslide, such as rainfall, earthquake, volcanic activity and human engineering activity, etc. Among the factors, rainfall was the the most common and the main inducing one. Many researches showed that the induced effect of rainfall was mainly reflected in the interacted process of soil and groundwater, which was transformed from rainwater. The process was called water-soil interaction(WSI). The water-soil interaction could be divided into two major types: the physical and mechanical interaction between soil and water, and the water-soil chemical interaction. For a long time, researchers in the field of geotechnical engineering mainly targeted at the former, such as pore water pressure, the matrix suction and effective stress, and so on. However, the latter mechanical effect was usually ignored. Although the water-soil chemical interaction had drawn the attention of some scholars, but the attention the researcher had paid was still relatively low. In this paper, the typical clay mineral——montmorillonite was taken as the cement to make up montmorillonite-quartz sand remolded soil. And the changes of cohesive force, which were caused by water-soil chemical interaction under landslide development temperatures(15 degrees Centigrade, 20 degrees Centigrade and 25 degrees Centigrade), were studied. The chemical environments included ultrapure water, pH=3HNO3 and pH=13.5NaOH solution, which simulated normal water, acid rain and alkaline waste liquid. By X-ray diffraction test, the mechanism, why the cohesive force changed, was analyzed from the perspective of the mineral composition change. Furthermore, in order to achieve quantitative description of cohesive force change caused by water-soil chemical interaction, this paper analyzed the essence of cohesive force, and modeling of cohesive force for saturated montmorillonite-quartz sand remolded soil was established. Then, based on the mechanism of water-soil chemical interaction, change of cohesive force calculation was realized preliminarily. By the experimental research and analysis, the conclusions were as follows: (1)Under ultrapure water condition, conductivity EC was characterized by increasing, pH also rose gradually and showed weak alkaline finally, the cohesive force of remolded soil rose firstly, then fell, finally rose again. Under nitric acid condition, pH of the soaking liquid rose gradually, conductivity EC reduced in the mass, and the cohesive force value rose and fell after the first decline. Under the condition of sodium hydroxide, pH and conductivity EC were both characterized by declining trend, the velocity slowed down gradually at later stage, the cohesive force showed rising and falling after the first drop, and then rose again. (2)Temperature promoted montmorillonite’s corrosion in water limitedly, but had a great influence on the chemical reaction between HNO3 and montmorillonite. In the early period of chemical reaction between strong base and montmorillonite, temperature had a larger role in promoting, the effect was not obvious at later stage. (3)The nitric acid could corrode montmorillonite, this lead to cohesive force’s drop. The mechanism of cohesive force’s increasing in soaking medium-term was not clear. Under both ultrapure water and alkaline condition, the zeolite minerals and calcium silicate hydrate (CSH) were generated. Under ultrapure water condition, calcium carbonate (CaCO3) was also generated. These new cements’ bond strength is far greater than the strength of binding force which exists between
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/15059
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
刘剑. 蒙脱石在酸碱条件下的力学效应[D]. 北京. 中国科学院研究生院,2015.
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