膨润土防水毯渗透性能的温度效应
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摘要
以颗粒状钠基膨润土防水毯为研究对象,采用改造的GDS全自动环境岩土渗透仪开展渗透试验,研究温度和压力对渗透系数的影响。研究表明:低围压下膨润土防水毯的渗透系数随温度的增加而减小,温度较高时趋于平缓或略有增大;围压增为100 kPa时,渗透系数随温度的增加而增大。固有渗透率随温度的增加而减小;低围压下固有渗透率减小更显著,仅考虑流体物理性质变化的渗透系数估算值与实测值有很大差异。膨润土吸附结合水量随温度的升高而减小,不能解释膨润土防水毯渗透系数和固有渗透率随温度的变化规律。当温度升高时,粒间孔隙减小且颗粒状膨润土分解成凝胶态蒙脱石颗粒,在低围压下凝胶态蒙脱石颗粒层间距离减小,是渗透系数和固有渗透率随温度的升高而减小的主要原因。
The hydraulic tests were conducted on geosynthetic clay liners( GCL) containing granular Nabentonite under different temperatures and pressures,using the GDS geoenvironmental permeameter. Under low pressures,the hydraulic conductivity decreases with the temperature,and will be gentle or slightly increases when the temperature is over 50-60 ℃. Nevertheless,the hydraulic conductivity decreases with the temperature under the pressure of 100 kPa. The intrinsic permeability decreases with the temperature,which is more significantly under low pressures. Therefore,a great difference exists between the estimated and the measured hydraulic conductivities when only considering the change in physical properties of the fluid with temperature. The adsorbed water content of bentonite decreases with the temperature, resulting in the estimated hydraulic conductivity less than the measured value and intrinsic permeability increasing with temperature,which cannot explain the permeability of GCL. With the increasing temperature,the granular bentonite will transform into the montmorillonite gel. Under low pressure, the distance between montmorillonite in intraparticle pore decreases with temperature, resulting in the decrease in hydraulic conductivity and intrinsic permeability.
The hydraulic tests were conducted on geosynthetic clay liners( GCL) containing granular Nabentonite under different temperatures and pressures,using the GDS geoenvironmental permeameter. Under low pressures,the hydraulic conductivity decreases with the temperature,and will be gentle or slightly increases when the temperature is over 50-60 ℃. Nevertheless,the hydraulic conductivity decreases with the temperature under the pressure of 100 kPa. The intrinsic permeability decreases with the temperature,which is more significantly under low pressures. Therefore,a great difference exists between the estimated and the measured hydraulic conductivities when only considering the change in physical properties of the fluid with temperature. The adsorbed water content of bentonite decreases with the temperature, resulting in the estimated hydraulic conductivity less than the measured value and intrinsic permeability increasing with temperature,which cannot explain the permeability of GCL. With the increasing temperature,the granular bentonite will transform into the montmorillonite gel. Under low pressure, the distance between montmorillonite in intraparticle pore decreases with temperature, resulting in the decrease in hydraulic conductivity and intrinsic permeability.
引文
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[2]ROWE R K,BOSTWICK L E,TAKE W A.Effect of GCL properties on shrinkage when subjected to wetdry cycles[J].Journal of Geotechnical and Geoenvironmental Engineering,2011,137(11):1019-1027.
[3]BOUAZZA A,ABUEL-NAGA H M,GATES W P,et al.Temperature effects on volume change and hydraulic properties of geosynthetic clay liners[C]//Proc.1st Pan American Geosynthetics Conf.,Cancun,Mexico(CD-Rom),2008.
[4]ABUEL-NAGA H M,BOUAZZA A,GATES W.Impact of bentonite form on the thermal evolution of the hydraulic conductivity of geosynthetic clay liners[J].Geotechnique,2013,3:26-30.
[5]XIE H,ZHANG C,SEDIGHI M,et al.An analytical model for diffusion of chemicals under thermal effects in semi-infinite porous media[J].Computers and Geotechnics,2015,69:329-337.
[6]AZAD F M,ROWE R K,EL-ZEIN A,et al.Laboratory investigation of thermally induced desiccation of GCLs in double composite liner systems[J].Geotextiles and Geomembranes,2011,29:534-543.
[7]邵玉娴,施斌,刘春,等.黏性土水理性质温度效应研究[J].岩土工程学报,2011,33(10):1576-1582.[SHAO Y X,SHI B,LIU C,et al.Temperature Effect on Hydro-physical Properties of Clayey Soils[J].Chinese Journal of Geotechnical Engineering,2011,33(10):1576-1582.(in Chinese)]
[8]何俊,阮晓晨,胡晓瑾,等.温度和模拟渗滤液作用下黏土的渗透性能研究[J].水文地质工程地质,2017,44(1):116-122.[HE J,RUAN X C,HU X J,et al.Effects of Temperature and Analog Leachate on Hydraulic Conductivity of Compacted Clay[J].Hydrogeology&Engineering Geology,2017,44(1):116-122.(in Chinese)]
[9]BEAT J.Dynamics of fluids in porous media[M].American Elsevier,New York.1972.
[10]中华人民共和国建设部.JG/T 193—2006钠基膨润土防水毯[S].北京:中国标准出版社,2006.[P.R.C.Ministry of Construction.JG/T 193—2006 Sodium Bentonite Geosynthetic Clay Liner[S].Beijing:Standards Press of China,2006.(in Chiness)]
[11]ISHIMORI H,KATSUMI T.Temperature effects on the swelling capacity and barrier performance of geosynthetic clay liners permeated with sodium chloride solutions[J].Geotextiles and Geomembranes,2012,33:25-33.
[12]CLEARY B A,LAKE C B.Comparing measured hydraulic conductivities of a geotextile polymer coated GCL utilizing three different permeameter types[C]//Proceedings of Geo-Frontiers 2011:Advances in Geotechnical Engineering,ASCE,2011.
[13]吴凤彩.粘性土的吸附结合水测量和渗流的某些特点[J].岩土工程学报,1984,6(6):84-93.[WU F C.The Adsorbed Bound Water Content Measurement and Some Characteristics of Seepage[J].Chinese Journal of Geotechnical Engineering,1984,6(6):84-93.(in Chinese)]
[14]YONG R N.Overview of modeling of clay microstructure and interactions for prediction of waste isolation barrier performance[J].Engineering Geology,1999,54:83-91.
[15]何俊,施建勇.膨润土中饱和渗透系数的计算[J].岩石力学与工程学报,2007,26(增刊2):3920-3925.[HE J,SHI J Y.Calculation of Saturated Permeability Coefficient of Bentonite[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(Sup 2):3920-3925.(in Chinese)]
[16]GEE M L,Mc Guiggan P M,Israelechvili J.Liquids to solid like transition of molecularly thin films under shear[J].Journal of Chemical Physics,1990,93:1895-1906.
[17]叶为民,申淼,王琼.温控高压实膨润土-砂混合物微观结构特征[J].佳木斯大学学报(自然科学版),2013,31(3):321-324.[YE W M,SHEN M,WANG Q.Micro-structural Characteristic of Highly Compacted San-bentonite Mixtures at Different Temperatures[J].Journal of Jiamusi University(Natural Science Edition),2013,31(3):321-324.(in Chinese)]