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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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3～5μm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SiO_2、Al_2O_3、K_2O、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。
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 SiO_2, Al_2O_3, K_2O, 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.
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 SiO_2, Al_2O_3, K_2O, 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.
引文
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[4] 李光雷,蔚立元,靖洪文,等.酸腐蚀后灰岩动态压缩力学性质的试验研究[J].岩土力学,2017,38(11):3247-3254.LI Guang-lei, YU Li-yuan, JING Hong-wen, et al. Experimental study of dynamic compressive mechanical properties of limestone after acid corrosion[J]. Rock and Soil Mechanics, 2017, 38(11): 3247-3254. (in Chinese)
[5] 杨德欢,颜荣涛,韦昌富,等.粉质黏土强度指标的水化学敏感性研究[J].岩土力学,2016,37(12):3529-3536.YANG De-huan, YAN Rong-tao, WEI Chang-fu, et al. A study of water chemical sensitivity of strength indices of silty clay[J]. Rock and Soil Mechanics, 2016, 37(12): 3529-3536. (in Chinese)
[6] 张先伟,孔令伟,陈成,等.水化学环境对湛江组黏土结构强度的影响研究[J].岩土工程学报,2017,39(11):1967-1975.ZHANG Xian-wei, KONG Ling-wei, CHEN Cheng, et al. Effects of hydrochemistry on structural strength of Zhanjiang formation clay[J]. Journal of Geotechnical Engineering, 2017, 39(11): 1967-1975. (in Chinese)
[7] GRATCHEV I, TOWHATA I. Stress-strain characteristics of two natural soils subjected to long-term acidic contamination[J]. Soils and Foundations, 2013, 53(3): 469-476.
[8] WAHIDA S, GAJO A, DI MAGGIO R. Chemo-mechanical effects in kaolinite. Part 2: exposed samples and chemical and phase analyses[J]. Géotechnique, 2011, 61(6): 449-457.
[9] KORICHI S, ELIAS A, MEFTI A. Characterization of smectite after acid activation with microwave irradiation[J]. Applied Clay Science, 2009, 42(3/4): 432-438.
[10] 汤连生.水-土化学作用的力学效应及机理分析[J].中山大学学报(自然科学版),2000,39(4):104-109.TANG Lian-sheng. Mechanical effect of chemical action of water on soil and analysis on its mechanism[J]. Acta Scientiarum Naturalium Universitatis Sunyatseni (Natural Science), 2000, 39(4): 104-109. (in Chinese)
[11] 周修萍,江静蓉,梁伟,等.模拟酸雨对南方五种土壤理化性质的影响[J].环境科学,1988,9(3):6-12.ZHOU Xiu-ping, JIANG Jing-rong, LIANG Wei, et al. Effect of acid rain on physical and chemical properties of five southern soils[J]. Environmental Science, 1988, 9(3): 6-12. (in Chinese)
[12] 李志清,李涛,胡瑞林,等.蒙自重塑膨胀土膨胀变形特性与施工控制研究[J].岩土工程学报,2008,30(12):1855-1860.LI Zhi-qing, LI Tao, HU Rui-lin, et al. Expansion characteristics and construction control of remolded Mengzi expansive soil[J]. Chinese Journal of Geotechnical Engineering, 2008, 30(12): 1855-1860. (in Chinese)
[13] CHAVALI R V P, PONNAPUREDDY H P R. Swelling and compressibility characteristics of bentonite and kaolin clay subjected to inorganic acid contamination[J]. International Journal of Geotechnical Engineering, 2018, 12(5): 1-7.
[14] BENDOU S, AMRANI M. Effect of hydrochloric acid on the structural of sodic-bentonite clay[J]. Journal of Minerals and Materials Characterization and Engineering, 2014, 2(5): 404-413.
[15] PANDA A K, MISHRA B G, MISHRA D K, et al. Effect of sulphuric acid treatment on the physico-chemical characteristics of kaolin clay[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2010, 363(1-3): 98-104.
[16] WANG Y H, SIU W K. Structure characteristics and mechanical properties of kaolinite soils. II. Effects of structure on mechanical properties[J]. Canadian Geotechnical Journal, 2006, 43(6): 601-617.
[17] BAKHSHIPOUR Z, ASADI A, HUAT B B K, et al. Effect of acid rain on geotechnical properties of residual soils[J]. Soils and Foundations, 2016, 56(6): 1008-1020.
[18] 李相然,姚志祥,曹振斌.济南典型地区地基土污染腐蚀性质变异研究[J].岩土力学,2004,25(8):1229-1233.LI Xiang-ran, YAO Zhi-xiang, CAO Zhen-bin. Study on physical and mechanical property variation of polluted erosive foundation soils in typical district of Jinan[J]. Rock and Soil Mechanics, 2004, 25(8): 1229-1233. (in Chinese)
[19] SIVAPULLAIAH P V, PRASAD B G, ALLAM M M. Effect of sulfuric acid on swelling behavior of an expansive soil[J]. Soil and Sediment Contamination: An International Journal, 2009, 18(2): 121-135.
[20] 杨和平,曲永新,郑健龙.宁明膨胀土研究的新进展[J].岩土工程学报,2005,27(9):981-987.YANG He-ping,QU Yong-xin, ZHENG Jian-long. New development in studies on Ningming expansive soils[J]. Journal of Geotechnical Engineering, 2005, 27(9): 981-987. (in Chinese).
[21] 张扬,王婷.我国酸雨综述[J].中国科技博览,2009(32):212.ZHANG Yang, WANG Ting. Overview of acid rain in China[J]. China Science and Technology Review, 2009(32): 212. (in Chinese)
[22] 李献民,王永和,杨果林,等.击实膨胀土工程变形特征的试验研究[J].岩土力学,2003,24(5):826-830.LI Xian-min, WANG Yong-he, YANG Guo-lin, et al. Test study on engineering deformation characteristics of compacted expansive soil[J]. Rock and Soil Mechanics, 2003, 24(5): 826-830. (in Chinese)
[23] STRZALKA D, GRABOWSKI F. Towards possible q-generalizations of the Malthus and Verhulst growth models[J]. Physica A: Statistical Mechanics and Its Applications, 2008, 387(11): 2511-2518.
[24] 欧孝夺,唐迎春,钟子文,等.重塑膨胀岩土微变形条件下膨胀力试验研究[J].岩石力学与工程学报,2013,32(5):1067-1072.OU Xiao-duo, TANG Ying-chun, ZHONG Zi-wen, et al. Test research on expansive force under small deformation of remolded expansive rock and soil[J]. Chinese Journal of Rock Mechanics and Engineering, 2013, 32(5): 1067-1072. (in Chinese)
[25] 汪贤恩,谭晓慧,辛志宇,等.膨胀土收缩性质的试验研究[J].岩土工程学报,2015,37(增2):107-114.WANG Xian-en, TAN Xiao-hui, XIN Zhi-yu, et al. Experimental study on shrinkage properties of expansive soils[J]. Chinese Journal of Geotechnical Engineering, 2015, 37(S2): 107-114. (in Chinese)
[26] 徐世民,吴志坚,赵文琛,等.基于Matlab和IPP的黄土孔隙微观结构研究[J].地震工程学报,2017,39(1):80-87.XU Shi-min, WU Zhi-jian, ZHAO Wen-chen, et al. Study of the microscopic pores of structured loess based on Matlab and IPP[J]. China Earthquake Engineering Journal, 2017, 39(1): 80-87. (in Chinese)
[27] 戴张俊,陈善雄,罗红明,等.南水北调中线膨胀土/岩微观特征及其性质研究[J].岩土工程学报,2013,35(5):948-954.DAI Zhang-jun, CHEN Shan-xiong, LUO Hong-ming, et al. Microstructure and characteristics of expansive soil and rock of middle route of South-to-North Water Diversion Project[J]. Chinese Journal of Geotechnical Engineering, 2013, 35(5): 948-954. (in Chinese)
[28] MOORE C A, DONALDSON C F. Quantifying soil microstructure using fractals[J]. Geotechnique, 1995, 45(1): 105-116.
[29] WANG Y H, SIU W K. Structure characteristics and mechanical properties of kaolinite soils. I. Surface charges and structural characterizations[J]. Canadian Geotechnical Journal, 2006, 43(6): 587-600.
[2] CHENG Ai-zhen, WEI Hua-hong, TAN Fei. Analysis of the temporal-spatial distribution and seasonal variation of the acid rain in Guangxi[J]. Meteorological and Environmental Research, 2010, 1(1): 62-65.
[3] 黄淑娟,唐毓勇.百色酸雨状况及成因分析[J].云南地理环境研究,2008,20(增1):20-23.HUANG Shu-juan, TANG Yu-yong. Analysis on status and cause of Baise acid rain[J]. Yunnan Geographical Environment Research, 2008, 20(S1): 20-23. (in Chinese)
[4] 李光雷,蔚立元,靖洪文,等.酸腐蚀后灰岩动态压缩力学性质的试验研究[J].岩土力学,2017,38(11):3247-3254.LI Guang-lei, YU Li-yuan, JING Hong-wen, et al. Experimental study of dynamic compressive mechanical properties of limestone after acid corrosion[J]. Rock and Soil Mechanics, 2017, 38(11): 3247-3254. (in Chinese)
[5] 杨德欢,颜荣涛,韦昌富,等.粉质黏土强度指标的水化学敏感性研究[J].岩土力学,2016,37(12):3529-3536.YANG De-huan, YAN Rong-tao, WEI Chang-fu, et al. A study of water chemical sensitivity of strength indices of silty clay[J]. Rock and Soil Mechanics, 2016, 37(12): 3529-3536. (in Chinese)
[6] 张先伟,孔令伟,陈成,等.水化学环境对湛江组黏土结构强度的影响研究[J].岩土工程学报,2017,39(11):1967-1975.ZHANG Xian-wei, KONG Ling-wei, CHEN Cheng, et al. Effects of hydrochemistry on structural strength of Zhanjiang formation clay[J]. Journal of Geotechnical Engineering, 2017, 39(11): 1967-1975. (in Chinese)
[7] GRATCHEV I, TOWHATA I. Stress-strain characteristics of two natural soils subjected to long-term acidic contamination[J]. Soils and Foundations, 2013, 53(3): 469-476.
[8] WAHIDA S, GAJO A, DI MAGGIO R. Chemo-mechanical effects in kaolinite. Part 2: exposed samples and chemical and phase analyses[J]. Géotechnique, 2011, 61(6): 449-457.
[9] KORICHI S, ELIAS A, MEFTI A. Characterization of smectite after acid activation with microwave irradiation[J]. Applied Clay Science, 2009, 42(3/4): 432-438.
[10] 汤连生.水-土化学作用的力学效应及机理分析[J].中山大学学报(自然科学版),2000,39(4):104-109.TANG Lian-sheng. Mechanical effect of chemical action of water on soil and analysis on its mechanism[J]. Acta Scientiarum Naturalium Universitatis Sunyatseni (Natural Science), 2000, 39(4): 104-109. (in Chinese)
[11] 周修萍,江静蓉,梁伟,等.模拟酸雨对南方五种土壤理化性质的影响[J].环境科学,1988,9(3):6-12.ZHOU Xiu-ping, JIANG Jing-rong, LIANG Wei, et al. Effect of acid rain on physical and chemical properties of five southern soils[J]. Environmental Science, 1988, 9(3): 6-12. (in Chinese)
[12] 李志清,李涛,胡瑞林,等.蒙自重塑膨胀土膨胀变形特性与施工控制研究[J].岩土工程学报,2008,30(12):1855-1860.LI Zhi-qing, LI Tao, HU Rui-lin, et al. Expansion characteristics and construction control of remolded Mengzi expansive soil[J]. Chinese Journal of Geotechnical Engineering, 2008, 30(12): 1855-1860. (in Chinese)
[13] CHAVALI R V P, PONNAPUREDDY H P R. Swelling and compressibility characteristics of bentonite and kaolin clay subjected to inorganic acid contamination[J]. International Journal of Geotechnical Engineering, 2018, 12(5): 1-7.
[14] BENDOU S, AMRANI M. Effect of hydrochloric acid on the structural of sodic-bentonite clay[J]. Journal of Minerals and Materials Characterization and Engineering, 2014, 2(5): 404-413.
[15] PANDA A K, MISHRA B G, MISHRA D K, et al. Effect of sulphuric acid treatment on the physico-chemical characteristics of kaolin clay[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2010, 363(1-3): 98-104.
[16] WANG Y H, SIU W K. Structure characteristics and mechanical properties of kaolinite soils. II. Effects of structure on mechanical properties[J]. Canadian Geotechnical Journal, 2006, 43(6): 601-617.
[17] BAKHSHIPOUR Z, ASADI A, HUAT B B K, et al. Effect of acid rain on geotechnical properties of residual soils[J]. Soils and Foundations, 2016, 56(6): 1008-1020.
[18] 李相然,姚志祥,曹振斌.济南典型地区地基土污染腐蚀性质变异研究[J].岩土力学,2004,25(8):1229-1233.LI Xiang-ran, YAO Zhi-xiang, CAO Zhen-bin. Study on physical and mechanical property variation of polluted erosive foundation soils in typical district of Jinan[J]. Rock and Soil Mechanics, 2004, 25(8): 1229-1233. (in Chinese)
[19] SIVAPULLAIAH P V, PRASAD B G, ALLAM M M. Effect of sulfuric acid on swelling behavior of an expansive soil[J]. Soil and Sediment Contamination: An International Journal, 2009, 18(2): 121-135.
[20] 杨和平,曲永新,郑健龙.宁明膨胀土研究的新进展[J].岩土工程学报,2005,27(9):981-987.YANG He-ping,QU Yong-xin, ZHENG Jian-long. New development in studies on Ningming expansive soils[J]. Journal of Geotechnical Engineering, 2005, 27(9): 981-987. (in Chinese).
[21] 张扬,王婷.我国酸雨综述[J].中国科技博览,2009(32):212.ZHANG Yang, WANG Ting. Overview of acid rain in China[J]. China Science and Technology Review, 2009(32): 212. (in Chinese)
[22] 李献民,王永和,杨果林,等.击实膨胀土工程变形特征的试验研究[J].岩土力学,2003,24(5):826-830.LI Xian-min, WANG Yong-he, YANG Guo-lin, et al. Test study on engineering deformation characteristics of compacted expansive soil[J]. Rock and Soil Mechanics, 2003, 24(5): 826-830. (in Chinese)
[23] STRZALKA D, GRABOWSKI F. Towards possible q-generalizations of the Malthus and Verhulst growth models[J]. Physica A: Statistical Mechanics and Its Applications, 2008, 387(11): 2511-2518.
[24] 欧孝夺,唐迎春,钟子文,等.重塑膨胀岩土微变形条件下膨胀力试验研究[J].岩石力学与工程学报,2013,32(5):1067-1072.OU Xiao-duo, TANG Ying-chun, ZHONG Zi-wen, et al. Test research on expansive force under small deformation of remolded expansive rock and soil[J]. Chinese Journal of Rock Mechanics and Engineering, 2013, 32(5): 1067-1072. (in Chinese)
[25] 汪贤恩,谭晓慧,辛志宇,等.膨胀土收缩性质的试验研究[J].岩土工程学报,2015,37(增2):107-114.WANG Xian-en, TAN Xiao-hui, XIN Zhi-yu, et al. Experimental study on shrinkage properties of expansive soils[J]. Chinese Journal of Geotechnical Engineering, 2015, 37(S2): 107-114. (in Chinese)
[26] 徐世民,吴志坚,赵文琛,等.基于Matlab和IPP的黄土孔隙微观结构研究[J].地震工程学报,2017,39(1):80-87.XU Shi-min, WU Zhi-jian, ZHAO Wen-chen, et al. Study of the microscopic pores of structured loess based on Matlab and IPP[J]. China Earthquake Engineering Journal, 2017, 39(1): 80-87. (in Chinese)
[27] 戴张俊,陈善雄,罗红明,等.南水北调中线膨胀土/岩微观特征及其性质研究[J].岩土工程学报,2013,35(5):948-954.DAI Zhang-jun, CHEN Shan-xiong, LUO Hong-ming, et al. Microstructure and characteristics of expansive soil and rock of middle route of South-to-North Water Diversion Project[J]. Chinese Journal of Geotechnical Engineering, 2013, 35(5): 948-954. (in Chinese)
[28] MOORE C A, DONALDSON C F. Quantifying soil microstructure using fractals[J]. Geotechnique, 1995, 45(1): 105-116.
[29] WANG Y H, SIU W K. Structure characteristics and mechanical properties of kaolinite soils. I. Surface charges and structural characterizations[J]. Canadian Geotechnical Journal, 2006, 43(6): 587-600.