利用HCA研究黏土渗透系数的标准探索
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摘要
黏性土渗透系数影响因素较多,甚至不同试验手段对试验结果都有较大影响。针对目前渗流试验中存在的问题,提出采用空心圆柱扭剪仪(HCA)测定软土渗透系数的方法,对其开展意义、可行性及试验步骤进行说明分析,并以重塑高岭土作为研究对象,开展一系列试验研究,探讨利用HCA开展渗流试验的标准,最终进行动力特性对软土渗透性影响的试验初步探索。结果表明:(1)以3600s作为单位时间,当连续24h的单位时间内平均渗透系数差值小于2%,将该阶段中得到渗透系数平均值作为最终渗透系数较为准确;(2)综合试验效率、试验间的可比性以及试验结果准确性,建议利用HCA开展重塑高岭土渗流试验时可选水力梯度范围为10～15;(3)重塑高岭土经过交通荷载作用10万次后,其渗透系数比经静载压缩同等轴向应变后的渗透系数低12.79%,即研究动力特性对渗透系数的影响意义重大。
There are many factors affecting the permeability coefficient(k) of cohesive soil, and different test methods have great influence on the test results. To solve the problems existing in present test methods, a hollow cylindrical torsional shear apparatus(HCA) was used for seepage tests. The significance, feasibility and experimental procedures for HCA seepage test were demonstrated, and remolded kaolin was used to carry out a series of experiments to explore the standard rules for permeability tests.Finally, a preliminary study of the dynamic test was explored. The results show that:(1) If 3 600 s is taken as the unit of time, the difference in average permeability coefficient in the unit time is less than 2% in continuous 24 h. Therefore, it is accurate to take the average of permeability coefficient obtained in this stage as the final permeability.(2) The hydraulic gradient range in HCA permeability test for kaolin is suggested between 10 and 15 after comprehensive consideration of test efficiency, comparability, and the accuracy.(3) After 100 000 cycles of dynamic traffic load, the permeability coefficient of kaolin is 12.79% lower than that of the same axial strain in static compression test, indicating that it is important to study the influence of dynamic characteristics on permeability coefficient.
There are many factors affecting the permeability coefficient(k) of cohesive soil, and different test methods have great influence on the test results. To solve the problems existing in present test methods, a hollow cylindrical torsional shear apparatus(HCA) was used for seepage tests. The significance, feasibility and experimental procedures for HCA seepage test were demonstrated, and remolded kaolin was used to carry out a series of experiments to explore the standard rules for permeability tests.Finally, a preliminary study of the dynamic test was explored. The results show that:(1) If 3 600 s is taken as the unit of time, the difference in average permeability coefficient in the unit time is less than 2% in continuous 24 h. Therefore, it is accurate to take the average of permeability coefficient obtained in this stage as the final permeability.(2) The hydraulic gradient range in HCA permeability test for kaolin is suggested between 10 and 15 after comprehensive consideration of test efficiency, comparability, and the accuracy.(3) After 100 000 cycles of dynamic traffic load, the permeability coefficient of kaolin is 12.79% lower than that of the same axial strain in static compression test, indicating that it is important to study the influence of dynamic characteristics on permeability coefficient.
引文
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[16]LEROUEIL S,BOUCLIN G,TAVENAS F,et al.Permeability anisotropy of natural clays as a function of strain[J].Canadian Geotechnical Journal,1990,27(5):568-579.
[17]BOWDERS J J,DANIEL D E.Hydraulic conductivity of compacted clay to dilute organic chemicals[J].Journal of Geotechnical Engineering,1987,113(12):1432-1448.
[18]严佳佳,周建,龚晓南,等.主应力轴纯旋转条件下原状黏土变形特性研究[J].岩土工程学报,2014,36(3):474-481.YAN Jia-jia,ZHOU Jian,GONG Xiao-nan,et al.Study on deformation characteristics of original clay under the condition of pure rotation of main stress axis[J].Chinese Journal of Geotechnical Engineering,2014,36(3):474-481.
[19]曹洋,周建,严佳佳.考虑循环应力比和频率影响的动荷载下软土微观结构研究[J].岩土力学,2014,35(3):735-743.CAO Yang,ZHOU Jian,YAN Jia-jia.Study of the microstructure of soft soil under dynamic load of cyclic stress ratio and frequency[J].Rock and Soil Mechanics,2014,35(3):735-743.
[20]冯晓腊,沈孝宇.饱和黏性土的渗透固结特性及其微观机制的研究[J].水文地质工程地质,1991(1):6-12.FENG Xiao-la,SHEN Xiao-yu.Study on the permeability and consolidation properties of saturated cohesive soil and its micro mechanism[J].Hydrogeology&Engineering Geology,1991(1):6-12.
[21]党发宁,刘海伟,王学武,等.基于有效孔隙比的黏性土渗透系数经验公式研究[J].岩石力学与工程学报,2015,34(9):1909-1917.DANG Fa-ning,LIU Hai-wei,WANG Xue-wu,et al.Empirical formula for permeability coefficient of cohesive soil based on effective void ratio[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(9):1909-1917.
[22]CHAPUIS R P,AUBERTIN M.On the use of the Kozeny-Carman’s equation to predict the hydraulic conductivity of a soil:reply[J].Canadian Geotechnical Journal,2004,41(5):994-996.
[2]邓永锋,刘松玉,章定文,等.几种孔隙比与渗透系数关系的对比[J].西北地震学报,2011,33(增刊):64-66.DENG Yong-feng,LIU Song-yu,ZHANG Ding-wen,et al.Comparison among some relationships between permeability and void ratio[J].Northwestern Seismological Journal,2011,33(Suppl.):64-66.
[3]CHAPUIS R P.Predicting the saturated hydraulic conductivity of soils:a review[J].Bulletin of Engineering Geology&the Environment,2012,71(3):401-434.
[4]TAVENAS F,LEBLOND P,JEAN P,et al.The permeability of natural soft clays.Part I:methods of laboratory[J].Canadian Geotechnical Journal,1983,20(4):629-644.
[5]NAGARAJ T S,PANDIAN N S,et al.Stress-state-permeability relations for overconsolidated clays[J].Géotechnique,1996,46(2):363-366.
[6]曹文炳,李克文,刘英兰.研究黏性土释水和渗透特性的多用途渗透固结试验装置[J].水文地质工程地质,1986(4):48-51,59.CAO Wen-bing,LI Ke-wen,LIU Ying-lan.Amulti-purpose osmotic consolidation test device for studying the release and infiltration characteristics of cohesive soil[J].Hydrogeology&Engineering Geology,1986(4):48-51,59.
[7]杜延龄,李春华,徐家海.研究饱和黏土渗透特性的试验装置[J].水利学报,1980(4):73-77.DU Yan-ling,LI Chun-hua,XU Jia-hai.Research on saturated clay permeability test device[J].Journal of Hydraulic Engineering,1980(4):73-77.
[8]柯瀚,王文芳,魏长春,等.填埋体饱和渗透系数影响因素室内研究[J].浙江大学学报(工学版),2013,47(7):1164-1170.KE Han,WANG Wen-fang,WEI Chang-chun,et al.Indoor research on the influence factors of saturated permeability coefficient of landfill[J].Journal of Zhejiang University(Engineering Edition),2013,47(7):1164-1170.
[9]张改玲,王雅敬.高围压下砂土的渗透特性试验研究[J].岩土力学,2014,35(10):2748-2754,2786.ZHANG Gai-ling,WANG Ya-jing.Experimental study on permeability of sand under high confining pressure[J].Rock and Soil Mechanics,2014,35(10):2748-2754,2786.
[10]GRANT A.Discussion:the development of a new hollow cylinder apparatus for investigating the effects of principal stress rotation in soils undrained anisotropy and principal stress rotation in saturated sand[J].Géotechnique,1985,35(1):78-85.
[11]黄博,丁浩,陈云敏,等.GDS空心圆柱仪动力试验能力探讨[J].岩土力学,2010,31(1):314-320.HUANG Bo,DING Hao,CHEN Yun-min,et al.Dynamic test capability of GDS hollow cylinder[J].Rock and Soil Mechanics,2010,31(1):314-320.
[12]郝鑫.海底交通隧道下饱和软黏土动力特性试验研究[D].杭州:浙江大学,2016.HAO Xin.Experimental study on dynamic characteristics of saturated soft clay under subsea transportation tunnel[D].Hangzhou:Zhejiang University,2016.
[13]CAZAUX D,DIDIER G.Comparison between various field and laboratory measurements of the hydraulic conductivity of three clay liners[J].ASTM Special Technical Publication,2002(1):3-24
[14]ASTM.D5084-03 Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter[S].West Conshohocken,PA:ASTM,2007.
[15]TAVENAS F,JEAN P,LEBLOND P,et al.The permeability of natural soft clays.Part II:permeability characteristics[J].Canadian Geotechnical Journal,1983,20(4):645-660.
[16]LEROUEIL S,BOUCLIN G,TAVENAS F,et al.Permeability anisotropy of natural clays as a function of strain[J].Canadian Geotechnical Journal,1990,27(5):568-579.
[17]BOWDERS J J,DANIEL D E.Hydraulic conductivity of compacted clay to dilute organic chemicals[J].Journal of Geotechnical Engineering,1987,113(12):1432-1448.
[18]严佳佳,周建,龚晓南,等.主应力轴纯旋转条件下原状黏土变形特性研究[J].岩土工程学报,2014,36(3):474-481.YAN Jia-jia,ZHOU Jian,GONG Xiao-nan,et al.Study on deformation characteristics of original clay under the condition of pure rotation of main stress axis[J].Chinese Journal of Geotechnical Engineering,2014,36(3):474-481.
[19]曹洋,周建,严佳佳.考虑循环应力比和频率影响的动荷载下软土微观结构研究[J].岩土力学,2014,35(3):735-743.CAO Yang,ZHOU Jian,YAN Jia-jia.Study of the microstructure of soft soil under dynamic load of cyclic stress ratio and frequency[J].Rock and Soil Mechanics,2014,35(3):735-743.
[20]冯晓腊,沈孝宇.饱和黏性土的渗透固结特性及其微观机制的研究[J].水文地质工程地质,1991(1):6-12.FENG Xiao-la,SHEN Xiao-yu.Study on the permeability and consolidation properties of saturated cohesive soil and its micro mechanism[J].Hydrogeology&Engineering Geology,1991(1):6-12.
[21]党发宁,刘海伟,王学武,等.基于有效孔隙比的黏性土渗透系数经验公式研究[J].岩石力学与工程学报,2015,34(9):1909-1917.DANG Fa-ning,LIU Hai-wei,WANG Xue-wu,et al.Empirical formula for permeability coefficient of cohesive soil based on effective void ratio[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(9):1909-1917.
[22]CHAPUIS R P,AUBERTIN M.On the use of the Kozeny-Carman’s equation to predict the hydraulic conductivity of a soil:reply[J].Canadian Geotechnical Journal,2004,41(5):994-996.