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1、This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or sell
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3、ding Elseviers archiving and manuscript policies are encouraged to visit:http:/ personal copyDesiccation and cracking behaviour of clay layer from slurry state under wettingdrying cyclesChao-Sheng Tanga, Yu-Jun Cuib, Bin Shia, Anh-Minh Tangb, Chun LiuaaSchool of Earth Sciences and Engineering, Nanji
4、ng University, 22 Hankou Road, Nanjing 210093, China bEcole des Ponts ParisTech, UR Navier/CERMES, 6 et 8, avenue Blaise Pascal, Cit Descartes, Champs-sur-Marne, 77455 Marne-la-Valle CEDEX 2, Francea b s t r a c ta r t i c l ei n f oArticle history: Received 2 November 2010 Received in revised form
5、18 July 2011 Accepted 22 July 2011 Available online 15 August 2011Keywords: Wettingdrying cycle Clay layer Desiccation crack Aggregate formation Image processing Crack patternLaboratory tests were conducted to investigate the effect of wettingdrying (WD) cycles on the initiationand evolution of crac
6、ks in clay layer. Four identical slurry specimens were prepared and subjected to five subsequent WD cycles. The water evaporation, surface cracks evolution and structure evolution during the WD cycles were monitored. The effect of WD cycles on the geometric characteristics of crack patterns wasanaly
7、zed by image processing. The results show that the desiccation and cracking behaviour was significantly affected by the applied WD cycles: the measured cracking water content c, surface crack ratio Rscand final thickness hfof the specimen increased significantly in the first three WD cycles and then
8、 tended to reach equilibrium; the formed crack patterns after the second WD cycle were more irregular than that after thefirst WD cycle; the increase of surface cracks was accompanied by the decrease of pore volume shrinkageduring drying. In addition, it was found that the applied WD cycles resulted
9、 in significant rearrangement of specimen structure: the initially homogeneous and non-aggregated structure was converted to a clear aggregated-structure with obvious inter-aggregate pores after the second WD cycle; the specimen volume generally increased with increasing cycles due to the aggregatio
10、n and increased porosity. The image analysisresults show that the geometric characteristics of crack pattern were significantly influenced by the WDcycles, but this influence was reduced after the third cycle. This is consistent with the observations over the experiment, and indicates that the image
11、 processing can be used for quantitatively analyzing the WD cycle dependence of clay desiccation cracking behaviour. 2011 Elsevier B.V. All rights reserved.1. IntroductionThe formation of desiccation cracks on soil surface due to lossof water is a common natural phenomenon, and can significantly aff
12、ect the soil performance in various geotechnical, agricultural and environmental applications. For example, a cracked soil is more compressible than an intact one at the same water content and the overall mechanical strength is weakened due to the presenceof cracks (Morris et al., 1992). The size (w
13、idth, length and depth), tortuosity, spatial distribution and connectivity of cracks govern the rate and the velocity at which solutes and microorganisms are transported in the soil, and thus control the dispersal of substances in soil (Horgan and Young, 2000). Most importantly, the soil hydraulic p
14、roperties are directlycontrolledbythedesiccationcracknetworks(Chertkov,2000; Chertkov and Ravina, 1999). Many previous studies have indicatedthat the hydraulic conductivity of cracked soils is several orders of magnitudegreaterthanthatofintactsoils(AlbrechtandBenson,2001; Boynton and Daniel, 1985).
15、This issue is therefore a major concern in design and construction of low permeability structures as clay buffers and barriers for nuclear waste isolation, liners and coversfor landfill, etc.Over the past decades, a number of field studies and laboratory experiments have been undertaken to investiga
16、te the initiation and propagation of desiccation cracks in soils (Corte and Higashi, 1960; Kleppe and Olson, 1985; Konrad and Ayad, 1997; Miller et al., 1998; Morris et al., 1992; Nahlawi and Kodikara, 2006; Tang et al., 2008, 2010; Velde, 1999). However, these investigations have been largely qualitative and most are limited in the description of desiccation cracking phenomena. More recently, techniques for quantifying themain features o
