| 酸性环境对百色膨胀土胀缩性能的影响及其微观解释 |
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| 引用本文： | 常锦,杨和平,肖杰,刘雄,陈冠一,毛瑞.酸性环境对百色膨胀土胀缩性能的影响及其微观解释[J].交通运输工程学报,2019,19(1):24-32. |
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| 作者姓名： | 常锦 杨和平 肖杰 刘雄 陈冠一 毛瑞 |
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| 作者单位： | 1.长沙理工大学 交通运输工程学院，湖南 长沙 4101142.长沙理工大学 道路灾变防治及交通安全教育部工程研究中心，湖南 长沙 410114 |
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| 基金项目： | 国家自然科学基金项目51608053湖南省自然科学基金项目2017JJ3335湖南省研究生科研创新项目CX2017B458 |
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| 摘 要： | 以广西酸雨重灾区百色膨胀土为研究对象, 模拟不同酸性条件(pH值分别为3、5、7) 开展无荷膨胀率、膨胀力与线缩率试验, 研究酸雨对其胀缩性能的影响, 并采用扫描电镜(SEM) 图像和X射线衍射(XRD) 图谱分析了其微观结构与矿物成分, 运用IPP图像处理软件定量分析了SEM图像中试样的微结构。研究结果表明: 试样起始含水率降低时, 酸性环境对其膨胀变形的促进作用加大; 起始含水率由17%降至9%时, 不同酸性环境下试样的无荷膨胀率之差变大, 相比中性溶液, pH值为3和5的酸性溶液浸泡试样的无荷膨胀率增幅分别由20.6%和5.6%增至26.9%和7.0%;随着溶液pH值的减小, 试样无荷膨胀率、膨胀力与线缩率均呈阶段性增长; 相比中性溶液, pH值为3的酸性溶液浸泡试样的实测无荷膨胀率、膨胀力与线缩率分别增加了24.3%、37.5%和16.9%;环境酸性越强, 试样水分蒸发的速度越快, 脱湿至稳定时的含水率越低, 受酸侵蚀土的孔隙数和尺寸随之增加; 当溶液pH值从7分别降至5和3时, 土体孔隙率由8.7%分别增至11.9%和19.4%, 直径为3~5 μm的孔隙数急剧增多; 酸性环境使矿物结晶的程度变差, 其中游离的SiO2、Al2O3、K2O、MgO和CaO等胶结物出现不同程度的溶蚀和淋滤, 使原叠聚体间的结构联结强度减弱, 由面面叠聚结构逐渐向边边结构演化, 环境酸性愈强, 这种演化趋势愈剧烈, 直接导致膨胀土的胀缩变形增大。
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| 关 键 词： | 路基工程 酸性环境 百色膨胀土 胀缩性能 微观结构 胶结物 溶蚀 淋滤 |
| 收稿时间： | 2018-07-11 |
Effect of acid environment on swelling-shrinkage properties of Baise expansive soil and its microscopic interpretation |
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| CHANG Jin,YANG He-ping,XIAO Jie,LIU Xiong,CHEN Guan-yi,MAO Rui.Effect of acid environment on swelling-shrinkage properties of Baise expansive soil and its microscopic interpretation[J].Journal of Traffic and Transportation Engineering,2019,19(1):24-32. |
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| Authors: | CHANG Jin YANG He-ping XIAO Jie LIU Xiong CHEN Guan-yi MAO Rui |
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| Affiliation: | 1.School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha 410114, Hunan, China2.Engineering Research Center of Catastrophic Prophylaxis and Treatment of Road and Traffic Safety of Ministry of Education, Changsha University of Science and Technology, Changsha 410114, Hunan, China |
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| Abstract: | The Baise expansive soil in heavy acid rain area of Guangxi was selected as the study subject. To explore the effect of acid rain on the swelling-shrinkage properties of Baise expansive soil, the load-free swelling rate test, swelling force test and linear shrinkage rate test were carried out under different acid conditions (pH values are 3, 5 and 7, respectively). The changes in the microstructure and mineral composition of expansive soil were analyzed through the scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns, the microstructures of specimens in SEM images were quantitatively analyzed based on the image processing software Image-Pro Plus (IPP). Research result shows that with the decrease of initial water content, the effect of acid environment on the expansive deformation of specimen increases. When the initial water content decreases from 17% to 9%, the differences of load-free swelling rate between the specimens under different acid environments increase. Comparing with the neutral solution, the increasing ranges of specimen load-free swelling rates soaked in acid solutions with pH values of 3 and 5 grow from 20.6% and 5.6% to 26.9% and 7.0%, respectively. With the decrease of solution pH value, the load-free swelling rates, swelling forces and linear shrinkage rates of specimens increase by stages. Comparing with the neutral solution, the measured load-free swelling rate, swelling force and linear shrinkage rate of specimen soaked in a solution with pH value of 3 increase by 24.3%, 37.5% and 16.9%, respectively. The more acidic the environment, the faster the water evaporation in specimen, and the lower the water content in specimen when it is dehumidified to stable. Both the pore number and size of acid-eroded soil increase with the increase of acidity. The soil porosity increases from 8.7% to 11.9% and 19.4%, respectively, when the solution pH value decreases from 7 to 5 and 3, respectively. The rapid increase of porosity mainly focuses on pore diameter ranging from 3-5 μm. The acid environment decreases the degree of mineral crystallization. Among them, the free colloidal minerals, such as SiO2, Al2O3, K2O, MgO and CaO, show different degrees of erosion and leaching. The erosion of colloidal mineral weakens the structural connection strength between the stacking structures, resulting in the evolution of stacking structure from face-to-face to edge-to-edge. The more acidic the environment, the severer the evolutionary trend, which directly leads to an increase of the swelling-shrinkage deformation of expansive soil. |
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