碱性材料对红土结构的侵蚀及危害
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摘要
水泥等碱性物质大量用于加固岩土工程,但红土结构在使用碱性材料加固后经济寿命反而明显缩短,其相关机制亟待明确。基于材料的化学分析和加速寿命实验原理,采用不同浓度的过饱和碱液恒温浸泡红土,模拟碱性加固材料对红土侵蚀的不同时长;然后检测红土被侵蚀后渗液中有效离子的浓度变化,显微观测红土颗粒和孔隙的劣化趋势,揭示碱性物质对红土结构的缓慢破坏机理。对比试验表明:碱性加固材料加速了红土中倍半氧化物、硅酸根等支撑物质的变异和流失;土颗粒的胶结物、包裹层、填充物均遭受了明显破坏,颗粒级配严重失衡。碱性物质还逐渐改变了倍半氧化物的表面电性,使硅溶胶、氧化铝等粘结成分变质,导致酸碱接触带附近的红土分崩离析。化学反应的生成物被压力渗水带出后,在土工结构中形成了大量的微架空和细观通道,并导致红土的工程指标劣化,诱发渗透破坏和溃塌灾难。
Alkaline materials,such as cement,are largely used to reinforce geotechnical engineering.The economic life of laterite structure is clearly shortened with alkaline reinforcing materials,and the ruinous causes are desiderated.Based on chemical analysis and principle of accelerated life test,laterite is dipped in supersaturating lye at constant temperature and multi-concentrations for simulating time of laterite erode by alkaline reinforcing materials.Changes in concentrations of effective-ion are tested in leachate,and pores-characteristics and grain-size-gradations of laterite are analyzed.Mechanism is put forward to explain how laterite structure is chronically demolished.Underprops of laterite structure,such as Al,Ti,and SiO3,are lost with speedup by alkaline substance.Coating layers of granule,bonded granules,and fillings between grains are clearly destroyed.Laterite is eroded into poorly-graded soil.Exterior polarity of sesquioxides is inchmeal changed by alkaline materials in contact zone,leading to viscous substances degenerating,thus laterite is decomposed and its structure is chronically ruined.Inner hollows and thin piping are largely engendered since reaction products are extruded off structure by seepage.As a result,engineering indices of laterite become bad and seepage failure and engineering collapse may befall.
Alkaline materials,such as cement,are largely used to reinforce geotechnical engineering.The economic life of laterite structure is clearly shortened with alkaline reinforcing materials,and the ruinous causes are desiderated.Based on chemical analysis and principle of accelerated life test,laterite is dipped in supersaturating lye at constant temperature and multi-concentrations for simulating time of laterite erode by alkaline reinforcing materials.Changes in concentrations of effective-ion are tested in leachate,and pores-characteristics and grain-size-gradations of laterite are analyzed.Mechanism is put forward to explain how laterite structure is chronically demolished.Underprops of laterite structure,such as Al,Ti,and SiO3,are lost with speedup by alkaline substance.Coating layers of granule,bonded granules,and fillings between grains are clearly destroyed.Laterite is eroded into poorly-graded soil.Exterior polarity of sesquioxides is inchmeal changed by alkaline materials in contact zone,leading to viscous substances degenerating,thus laterite is decomposed and its structure is chronically ruined.Inner hollows and thin piping are largely engendered since reaction products are extruded off structure by seepage.As a result,engineering indices of laterite become bad and seepage failure and engineering collapse may befall.
引文
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[2]黄英,符必昌.红土化学成分的变化特征[J].昆明理工大学学报,2002,27(4):63-66.[HUANGY,FU B C.The Change Properties of the ChemicalCompositions for Laterite[J].Journal of KunmingUniversity of Science and Technology,2002,27(4):63-66.(in Chinese)]
[3]Chen Xiaobin,Zhang Jiasheng,Liu Baochen,et al.Effects of stress conditions on rheological properties ofgranular soil in large triaxial rheology laboratory tests[J].Journal of Central South University ofTechnology,2008,15(s1):397-401.
[4]吴艳,翟玉春,牟文宁,等.粉煤灰提铝渣中二氧化硅在高浓度碱液中的溶解行为[J].中国有色金属学报,2008,18(增1):S408-S411.[WU Y,ZHAIY C,MU W N,et al.Dissolving behavior of SiO2 inresidue of fly ash detached A12O3 in highlyconcentrated alkali solution[J].The Chinese Journalof Nonferrous Metals,2008,18(s1):S408-S411.(in Chinese)]
[5]周训华,廖义玲.红粘土颗粒之间结构连结的胶体化学特征[J].贵州工业大学学报:自然科学版,2004,33(1):26-29.[ZHOU X H,LIAO Y L.Collochemistry character of the structure connectionamong laterite mineral grain[J].Journal of GuizhouUniversity of Technology:Natural Science Edition,2004,33(1):26-29.(in Chinese)]
[6]Gerson A R.The surface modification of kaoliniteusing water vapour Plasma[C]//Cisneros G.Computational Chemistry and Chemical Engineering.New Jersey:World Scientific Press,1997:227-235.
[7]J Francis,Young.Advanced cement-based materials[C]//Wang Peiming.Proceedings of the 5thInternational Symposium on Cement and Concrete(Volume 1).Shanghai:Foreign Languages Press,2002:193-198.
[8]黄英,何发祥,金克盛,等.胶结材料对云南红土胶结特性的影响研究[J].铁道科学与工程学报,2007,4(5):51-56.[HUANG Y,HE F X,JIN KS,et al.Effects of cementatory materials on Yunnanlaterite[J].Journal of Railway Science andEngineering,2007,4(5):51-56.(in Chinese)]
[9]Sayao A,Maia P,Nunes A.Considerations on theshear strength behavior of weathered rockfill[C]//DFrancis.Proceedings of the International Conferenceon Soil Mechanics and Geotechnical Engineering.Boston:ISSMGE,2005,1917–1920.
[10]巴恒静,张武满.混凝土寿命加速实验方法与预测[J].硅酸盐学报,2007,35(2):242-246.[BAH J,ZHANG W M.Accelerated life test and servicelife prediction of concrete[J].Journal of the ChineseCeramic Society,2007,35(2):242-246.(inChinese)]
[11]Zhang Lanlan,Chen Muhong,Xiang Rong,et al.Distribution of biogenic silica content in surfacesediments from the southern south china sea and itsenvironmental significance[J].Marine ScienceBulletin,2009,11(1):43-52.
[12]沙德仁.提高硅钼黄比色溶液稳定性的研究[J].玻璃纤维,2010,26(4):18-28.[SHA D R.Study of improving the stability of colorimetric Solutionof silicon molybdenum yellow[J].Fiber Glass,2010,26(4):18-28.(in Chinese)]
[13]Deutsches Institut für Normung e.V.(DIN).DINEN 13535-2001 Fertilizers and liming materials-Classification;German version EN[S].London:Normung Press,2001.
[14]AFNOR.NF U42-041-2-2000 Fertilizers andliming materials and soil improvers-Vocabulary-Part 2:terms relating to fertilizers[S].Paris:CEN Press,2000.
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