温度梯度下压实黏土的水热迁移规律和渗透特性
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摘要
开展了室内压实黏土体模型柱试验,研究了温度梯度作用对压实黏土水热迁移和渗透性的响应规律.结果表明:热量在黏土柱下部比黏土柱上部传输快,温度的升高随离热源距离的增加而明显延迟;底部热源促使压实黏土柱产生温度梯度,进而促使水汽在黏土柱内由底向上迁移,造成水分损失较快;随热源的持续作用,黏土柱内温度梯度逐渐下降,水汽迁移速率减小,含水率下降缓慢并趋于稳定.热源持续作用使土柱上表面开裂程度明显大于下底面,用示踪剂来粗略测量裂缝深度是可行的.温度梯度作用不同程度地增大了黏土体的渗透系数,且黏土柱的两端渗透系数增加较快,中间部分增大倍数次之.
Through the indoor model experiments, the response law s of the moisture-heat migration and permeability of compacted clay w ere studied under the temperature gradient. The results demonstrated that: the heat transmitted relatively faster at the bottom of clay column than the upper of clay column; the rise of the temperature underw ent an obvious delay w ith the increase of the distance from the heat source; the heat at the bottom facilitated the occurrence of the temperature gradient inside the compacted clay column,w hich further prompted the moisture migration from the bottom to the top and caused the quick loss of w ater; w ith the continuous heating,the temperature gradient inside the compacted clay column underw ent a gradual decline,the rate of moisture migration reduced and the moisture content decreased very slow ly and tended to be stable. Under the continuous influence of the heat source,the cracking degree of the upper surface w as significantly larger than that of the bottom and it w as proved to be feasible to test the cracking depth using a tracer. The temperature gradient raised the permeability coefficient of compacted clay to varying degrees. M oreover,the permeability coefficient at both ends of the clay column rose quickly,follow ed by that in the middle of the clay column.
Through the indoor model experiments, the response law s of the moisture-heat migration and permeability of compacted clay w ere studied under the temperature gradient. The results demonstrated that: the heat transmitted relatively faster at the bottom of clay column than the upper of clay column; the rise of the temperature underw ent an obvious delay w ith the increase of the distance from the heat source; the heat at the bottom facilitated the occurrence of the temperature gradient inside the compacted clay column,w hich further prompted the moisture migration from the bottom to the top and caused the quick loss of w ater; w ith the continuous heating,the temperature gradient inside the compacted clay column underw ent a gradual decline,the rate of moisture migration reduced and the moisture content decreased very slow ly and tended to be stable. Under the continuous influence of the heat source,the cracking degree of the upper surface w as significantly larger than that of the bottom and it w as proved to be feasible to test the cracking depth using a tracer. The temperature gradient raised the permeability coefficient of compacted clay to varying degrees. M oreover,the permeability coefficient at both ends of the clay column rose quickly,follow ed by that in the middle of the clay column.
引文
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[2]唐朝生,施斌,刘春,等.黏性土在不同温度下干缩裂缝的发展规律及形态学定量分析[J].岩土工程学报,2007,29(5):743-749.(Tang Chao-sheng,Shi Bin,Liu Chun,et al.Developing law and morphological analysis of shrinkage cracks of clayey soil under different temperatures[J].Chinese Journal of Geotechnical Engineering,2007,29(5):743-749.)
[3]Tang C S,Shi B,Liu C,et al.Influencing factors of geometrical structure of surface shrinkage cracks in clayey soils[J].Engineering Geology,2008,101(3/4):204-217.
[4]Zhou Y F,Rowe R K.Development of a technique for modelling clay liner desiccation[J].International Journal for Numerical and Analytical Methods in Geo-mechanics,2003,27:473-493.
[5]Zhou Y F,Rowe R K.Modelling of clay liner desiccation[J].International Journal of Geo-mechanics,2005,5(1):1-9.
[6]D9ll P.Desiccation of mineral liners below landfills with heat generation[J].Journal of Geotechnical and Geoenvironmental Engineering,1997,123(11):1001-1009.
[7]Southen J M,Rowe R K.Modelling of thermally induced desiccation of geosynthetic clay liners[J].Geotextiles and Geomembranes,2005,23(5):425-442.
[8]Southen J M,Rowe R K.Laboratory investigation of geosynthetic clay liner desiccation in a composite liner subjected to thermal gradients[J].Journal of Geotechnical and Geoenvironmental Engineering,2005,131(7):925-935.
[9]Azad F M,El-Zein A,Rowe R K,et al.Modelling of thermally induced desiccation of geosynthetic clay liners in double composite liner systems[J].Geotextiles and Geomembranes,2012,34:28-38.
[10]Wang M W,Li J,Ge S,et al.Moisture migration tests on unsaturated expansive clays in Hefei,China[J].Applied Clay Science,2013,79:30-35.
[11]蔡光华.垃圾填埋场压实黏土封场系统开裂规律研究[D].武汉:武汉工业学院,2012.(Cai Guang-hua.Cracking law of landfill compacted clay cover system[D].Wuhan:Wuhan University of Technology,2012.)
[12]陆海军,蔡光华,何翔,等.一种温度-水流耦合作用下黏土裂缝的检测装置:ZL.2010.2 0693702.X[P].2010-12-31.(Lu Hai-jun,Cai Guang-hua,He Xiang,et al.A detection device of clay cracking under the temperature-flow coupling effects:ZL.2010.2 0693702.X[P].2010-12-31.)
[13]US-ASTM.Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter:ASTM D5084[S].West Conshohocken,2002.
[14]Rayhani M H T,Yanful E K,Fakher A.Physical modeling of desiccation cracking in plastic soils[J].Engineering Geology,2008,97(1/2):25-31.