电渗前后淤泥质土的物理力学性质对比研究
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摘要
为深入研究电渗排水对土体工程性质的影响,采用铁丝为电极,在模型箱内对南京市某河道淤泥质土进行电渗排水模拟试验。电渗前后土的物理力学性质对比分析表明:电渗后土体的液、塑限与塑性指数均降低;电渗前后土体在相同含水量和干密度情况下进行直接剪切试验,发现电渗后土体的凝聚力和内摩擦角均降低,即电渗后土体在特定情况下出现了强度衰减的现象。论文基于土中阳离子流失机理对土体在特定情况下的强度衰减现象进行了微观解释。另外,利用提出的新的电渗机理从微观角度解释了电渗过程中土体开裂现象,阳极因快速失水,最早出现裂隙,但裂隙延展范围较小;阴极含水量始终高于阳极,且失水速度较慢,裂隙延展范围较大。值得一提的是,在以往的研究中并未关注到电渗加固过程中土中阳离子流失对电渗后土体性质的影响。
In order to study the effect of electro-osmotic drainage on soil properties,electro-osmotic consolidation of the muddy soil in a river channel in Nanjing was studied in laboratory by using wire electrode in a model.Before and after electro-osmosis,the muddy soil was analyzed and compared through physical and mechanical properties.The results demonstrated that liquid limit,plastic limit and the plastic limit index decreased after electro-osmosis.Before and after the electro-osmosis,the soil was used for direct shear test under the same water content and dry density.It’s found that the cohesion and internal friction angle of the soil reduce under specific conditions,that is,electro-osmosis leads to strength attenuation.In this paper,the mechanism of soil strength attenuation is explained based on cation loss in soil during electro-osmosis.In addition,this paper proposed a new electro-osmotic mechanism to explain the phenomenon of soil cracking in the process of electro-osmosis from the microscopic point of view.The anode had the earliest fracture due to rapid dehydration,but the extension range of fracture was smaller.The water content of cathode was always higher than that of the anode and cathode had the slower water loss.So,the cathode had a large range of crack extension.It is worth mentioning that,the influence of the cation loss on the properties of the soil has not been noticed in the past study.
In order to study the effect of electro-osmotic drainage on soil properties,electro-osmotic consolidation of the muddy soil in a river channel in Nanjing was studied in laboratory by using wire electrode in a model.Before and after electro-osmosis,the muddy soil was analyzed and compared through physical and mechanical properties.The results demonstrated that liquid limit,plastic limit and the plastic limit index decreased after electro-osmosis.Before and after the electro-osmosis,the soil was used for direct shear test under the same water content and dry density.It’s found that the cohesion and internal friction angle of the soil reduce under specific conditions,that is,electro-osmosis leads to strength attenuation.In this paper,the mechanism of soil strength attenuation is explained based on cation loss in soil during electro-osmosis.In addition,this paper proposed a new electro-osmotic mechanism to explain the phenomenon of soil cracking in the process of electro-osmosis from the microscopic point of view.The anode had the earliest fracture due to rapid dehydration,but the extension range of fracture was smaller.The water content of cathode was always higher than that of the anode and cathode had the slower water loss.So,the cathode had a large range of crack extension.It is worth mentioning that,the influence of the cation loss on the properties of the soil has not been noticed in the past study.
引文
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李苗,张林洪,王苏达.2007.电渗法处理填土地基的排水效果影响因素分析[J].岩土工程技术,21(1):4-6,10.
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汪闻韶.1999.汪闻韶院士土工问题论文选集[M].北京:中国建筑工业出版社.
王协群,邹维列.2007.电渗排水法加固湖相软黏土的试验研究[J].武汉理工大学学报,29(2):95-99.
庄艳峰,王钊,林清.2005.电渗的能级梯度理论[J].哈尔滨工业大学学报,37(2):283-286.
Bjerrum L,Moum J and Eide O.1967.Application of electroosmosis to a foundation problem in a norwegian quick clay[J].Geotechnique,17:214-235.
Casagrande L.1952.Electro-osmotic stabilization of soils[J].Journal of the Boston Society of Civil Engineering,39:51-83.
Glendinning S,Lamont-Black J and Jones C J F P.2007.Treatment of sewage sludge using electrokinetic geosynthetics[J].Journal of Hazardous Materials,A139:491-499.
Hoeksema R J.2007.Three stages in the history of land reclamation in the Netherlands[J].Irrigation and Drainage,56:113-126.
Shang J Q and Loky.1997.Electrokinetic dewatering of a phosphate clay[J].Journal of Hazardous Materials,55:117-133.
Yang L A.2003.Mechanics of the consolidation of a lumpy soft clay fill[D].Singapore:National University of Singapore.
李瑛,龚晓南.2012.等电势梯度下电极间距对电渗影响的试验研究[J]岩土力学,33(1):89-95.
李苗,张林洪,王苏达.2007.电渗法处理填土地基的排水效果影响因素分析[J].岩土工程技术,21(1):4-6,10.
李瑛,龚晓南,焦丹,等.2009.软黏土二维电渗固结性状的试验研究[J]岩石力学与工程学报,28(增2):4034-4039.
陶燕丽.2015.不同电极电渗过程比较及基于电导率电渗排水量计算方法[D].杭州:浙江大学.
汪闻韶.1999.汪闻韶院士土工问题论文选集[M].北京:中国建筑工业出版社.
王协群,邹维列.2007.电渗排水法加固湖相软黏土的试验研究[J].武汉理工大学学报,29(2):95-99.
庄艳峰,王钊,林清.2005.电渗的能级梯度理论[J].哈尔滨工业大学学报,37(2):283-286.
Bjerrum L,Moum J and Eide O.1967.Application of electroosmosis to a foundation problem in a norwegian quick clay[J].Geotechnique,17:214-235.
Casagrande L.1952.Electro-osmotic stabilization of soils[J].Journal of the Boston Society of Civil Engineering,39:51-83.
Glendinning S,Lamont-Black J and Jones C J F P.2007.Treatment of sewage sludge using electrokinetic geosynthetics[J].Journal of Hazardous Materials,A139:491-499.
Hoeksema R J.2007.Three stages in the history of land reclamation in the Netherlands[J].Irrigation and Drainage,56:113-126.
Shang J Q and Loky.1997.Electrokinetic dewatering of a phosphate clay[J].Journal of Hazardous Materials,55:117-133.
Yang L A.2003.Mechanics of the consolidation of a lumpy soft clay fill[D].Singapore:National University of Singapore.