盐溶液中膨润土峰值剪切强度的计算方法
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摘要
膨润土作为高放废物地质处置库的工程屏障材料,在高放废物储存罐与围岩间起缓冲作用,与地下围岩裂隙水接触,膨润土的剪切强度产生变化,危及核废物处置库缓冲层的安全。因此,计算盐溶液中膨润土的剪切强度对保障核废物处置库缓冲层安全具有十分重要的意义。利用双电层理论,从微观角度定性地解释了盐溶液浓度对膨润土峰值剪切强度影响的机理;根据膨润土在盐溶液中的应力平衡,提出考虑盐溶液的渗透吸力影响的修正有效应力概念,反映盐溶液浓度对膨润土强度的影响;基于膨润土表面的分形模型,导出与渗透吸力对应的修正有效应力的表达式,盐溶液的渗透吸力采用修正的Debye-Hückel公式计算;根据Mohr-Coulomb准则,膨润土在盐溶液中的峰值剪切强度(■)由修正有效应力(p~e)表示为统一线性关系:■。
Bentonite,as a barrier material for high-level waste disposal repositories,acts as a buffer material between waste storage tanks and surrounding rocks.The salt solutions in the cracks of the surrounding rock will affect the peak shear strength of the bentonite and interfere with the stability of the nuclear waste repository.Therefore,the determination of the peak shear strength of the bentonite in salt solutions is of great importance.The peak shear strength of the bentonite affected by salt solutions is analyzed from the perspective of electric diffuse double-layer theory.The concept of modified effective stress is proposed to express the peak shear strength of the bentonite incorporating with the osmotic suction of salt solutions.Based on the fractal model for bentonite surface,the expression for the modified effective stress is related to the osmotic suction based on the stress balance of bentonite in salt solutions.The osmotic suction is calculated by the modified Debye-Hückel equation.Considering the Mohr-Coulomb criterion,the peak shear strength(■) of the bentonite is expressed by the modified effective stress(p~e) in a uniform linear relationship as ■.
Bentonite,as a barrier material for high-level waste disposal repositories,acts as a buffer material between waste storage tanks and surrounding rocks.The salt solutions in the cracks of the surrounding rock will affect the peak shear strength of the bentonite and interfere with the stability of the nuclear waste repository.Therefore,the determination of the peak shear strength of the bentonite in salt solutions is of great importance.The peak shear strength of the bentonite affected by salt solutions is analyzed from the perspective of electric diffuse double-layer theory.The concept of modified effective stress is proposed to express the peak shear strength of the bentonite incorporating with the osmotic suction of salt solutions.Based on the fractal model for bentonite surface,the expression for the modified effective stress is related to the osmotic suction based on the stress balance of bentonite in salt solutions.The osmotic suction is calculated by the modified Debye-Hückel equation.Considering the Mohr-Coulomb criterion,the peak shear strength(■) of the bentonite is expressed by the modified effective stress(p~e) in a uniform linear relationship as ■.
引文
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[28]孙德安,张谨绎,宋国森.氯盐渍土土-水特征曲线的试验研究[J].岩土力学,2013,34(4):955-960.(SUN De-an,ZHANG Jin-yi,SONG Guo-seng.Experimental study of soil-water characteristic curve of chlorine saline soil[J].Rock and Soil Mechanics,2013,34(4):955-960.(in Chinese))
[29]ROCKLAND L B.Saturated salt solutions for static control of relative humidity between 5°and 40°C[J].Analytical Chemistry,1960,32(10):1375-1376.
[30]MITCHELL J K,SOGA K.Fundamentals of soil behavior[M].3rd ed.New York:Wiley,2005.
[31]BURLAND J B,FENG.On the compressibility and shear strength of natural clay[J].Géotechnique,1990,40(3):329-378.
[32]SKEMPTON A W.Residual strength of clays in landslides folded strata and the laboratory[J].Géotechnique,1985,35(1):3-18.
[2]WANG J,SU R,CHEN W M,et al.Deep geological disposal of high-level radioactive wastes in china[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(4):649-658.
[3]DI MAIO C.Shear strength of clays and clayey soils:the influence of pore fluid composition[C]//CISM Courses and Lectures.Vienna,2004,462:45-55.
[4]MAN A,GRAHAM J,VAN GULCK J.Effect of pore fluid chemistry on strain-softening behaviour of reconstituted plastic clay[C]//Proc 5th Int Conf Geoenvir Eng.Cardiff,2006,1:569-576.
[5]WINTERKORN H F,MOORMAN R B.A study of changes in physical properties of Putnam soil induced by ionic substitution[J].Highway Research Board Proceedings,1941,21:415-434.
[6]ZHANG L,SUN D A,JIA D.Shear strength of GMZ07bentonite and its mixture with sand saturated with saline solution[J].Applied Clay Science,2016:24-32,132-133.
[7]ELKADY T Y,AL-MAHBASHI A M.Effect of solute concentration on the volume change and shear strength of compacted natural expansive clay[J].Environmental Earth Sciences,2017,76:483.
[8]ANSON R W W,HAWKINS A B.The effect of calcium ions in pore water on the residual shear strength of kaolinite and sodium montmorillonite[J].Géotechnique,1998,48(6):787-800.
[9]姚传芹,韦昌富,马田田,等.孔隙溶液对膨胀土力学性质影响[J].岩土力学,2017,38(2):116-122.(YAO Chuan-qin,WEI Chang-fu,MA Tian-tian,et al.Effects of pore solution on mechanical properties of expansive soil[J].Rock and Soil Mechanics,2017,38(2):116-122.(in Chinese))
[10]CALVELLO M,LASCO M,VASSALLO R,et al.Compressibility and residual shear strength of smectitic clays:influence of pore aqueous solutions and organic solvents[J].Italian Geotechnical Journal,2005,1:33-46.
[11]WARKENTIN B P,YONG R N.Shear strength of montmorillonite and kaolinite related to interparticle forces[J].Clay and Clay Minerals,1962:210-218.
[12]SRIDHARAN A,RAO G V.Shear strength behavior of saturated clay and the role of the effective stress concept[J].Géotechnique,1979,29(2):177-193.
[13]LIU L,MORENO L,NERETNIEKS I.A dynamic force balance model for colloid expansion and its DLVO-Based application[J].Langmuir,2009,25:679-687.
[14]贾景超.膨胀土膨胀机理及细观膨胀模型研究[D].大连:大连理工大学,2010.(JIA Jing-chao.Study on the swelling mechanism and mesomechanical swelling model of expansive soil[D].Dalian:Dalian University of Technology,2010.(in Chinese))
[15]DEBRUYN C,COLLINS L F,WILLIAMS A.The specific surface,water affinity and expansive potential of clays[J].Clay Miner.,1957,3:120-128.
[16]XU Y F,XIANG G S,JIANG H,et al.Role of osmotic suction in volume change of clays in salt solution[J].Applied Clay Science,2014,101:354-361.
[17]项国圣,姜昊,徐永福.压实膨润土膨胀变形的分形计算方法[J].岩土力学,2015,36(4):1009-1014.(XIANGGuo-sheng,JIANG Hao,XU Yong-fu.Fractal calculation method for swelling deformation of compacted[J].Rock and Soil Mechanics,20015,36(4):1009-1014.(in Chinese))
[18]项国圣,徐永福,姜昊.膨润土表面分维的试验确定[J].地下空间与工程学报,2016,12:369-373.(XIANGGuo-sheng,XU Yong-fu,JIANG Hao.Test determination for the surface fractal dimension of bentonite[J].Chinese Journal of Underground Space and Engineering,2016,12:369-373.(in Chinese))
[19]RAO S M,THYAGARAJ T.Swell-compression behavior of compacted clays under chemical gradients[J].Canadian Geotechnical Journal,2007,44:520-532.
[20]ALEXANDER,MARIANA D,JAIME W,et al.The vapor pressure of water over saturated aqueous solutions of malic,tartaric,and citric acids,at temperatures from 288 K to 323K[J].Journal Chemical Thermodynamics,1995,27(1):35-41.
[21]WIJMANS J G,BAKER R W.The solution-diffusion model:a review[J].Journal of Membrane Science,1995,107(1/2):1-21.
[22]FERNáNDEZ D P,GOODWIN A R H,LEMMON E W,et al.A formulation for the static permittivity of water and steam at temperature from 238 K to 873 K at pressures up to 1200MPa,including derivatives and Debye-Hückel coefficients[J].Journal of Physical and Chemical Reference Data,1997,26(4):1125-1166.
[23]SCATCHARD G.The excess free energy and related properties of solutions containing electrolytes[J].Journal of the American Chemical Society,1968,90(12):3124-3127.
[24]PITZER S K,MAYORGA G.Thermodynamics of electrolytes:Ⅱactivity and osmotic coefficients for strong electrolytes with one or both ions univalent[J].The Journal of Physical Chemistry,1972,77(19):2300-2308.
[25]PITZER S K,MAYORGA G.Thermodynamics of electrolytes:Ⅲactivity and osmotic coefficients for 2-2electrolytes[J].Journal of Solution Chemistry,1973,3(7):539-546.
[26]CLARKE E C W,GLEW D N.Evaluation of thermodynamic function for aqueous sodium chloride from equilibrium and calorimetric measurements below 154°C[J].Journal of Physical and Chemical Reference Data,1985,14(2):489-610.
[27]HAMER W J,WU Y C.Osmotic coefficient and mean activity coefficients of uni-univalent electrolytes in water at25℃[J].Journal of Physical and Chemical Reference Data,1972,1(4):1047-1099.
[28]孙德安,张谨绎,宋国森.氯盐渍土土-水特征曲线的试验研究[J].岩土力学,2013,34(4):955-960.(SUN De-an,ZHANG Jin-yi,SONG Guo-seng.Experimental study of soil-water characteristic curve of chlorine saline soil[J].Rock and Soil Mechanics,2013,34(4):955-960.(in Chinese))
[29]ROCKLAND L B.Saturated salt solutions for static control of relative humidity between 5°and 40°C[J].Analytical Chemistry,1960,32(10):1375-1376.
[30]MITCHELL J K,SOGA K.Fundamentals of soil behavior[M].3rd ed.New York:Wiley,2005.
[31]BURLAND J B,FENG.On the compressibility and shear strength of natural clay[J].Géotechnique,1990,40(3):329-378.
[32]SKEMPTON A W.Residual strength of clays in landslides folded strata and the laboratory[J].Géotechnique,1985,35(1):3-18.