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| Effects of layer thickness and temperature on the crack morphology of Chongqing silt |
| FANG Huaqiang1，2，JIANG Chunyong1，2，WANG Chenglong1，2，OU Qiang1，2，LONG Kaiquan1，2 |
| (1. Key Laboratory of New Technology for Construction of Cities in Mountain Area，Chongqing University，Chongqing 400450，China；2. College of Civil Engineering，Chongqing University，Chongqing 400450，China ) |
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Abstract Soil desiccation cracking is a common natural phenomenon. The initiation and propagation of cracks can significantly weaken the structure and integrity of the soil，leading to engineering disasters. In order to study the influence of the layer thickness and the temperature on the crack morphology of Chongqing silt，physical test，XRF test，XRD diffraction test，desiccation cracking test and scanning electron microscope test are carried out. Subsequently，based on digital image processing technology，fractal theory，etc.，the quantitative characterization of the crack morphology is realized. The results show that Chongqing silt is a high liquid limit clay，whose particle morphology presents a dispersed structure and irregular particle clusters，and that the cracks mostly present the forms of three way junctions such as T and Y shapes，and the soil clods divided by the cracks are mostly in the forms of triangles，polygons and sectors. Under the corresponding temperature condition，the number of nodes，the number of cracks，the total length of cracks，the number of clods and the total area of clods all decrease with increasing the layer thickness，while the total crack area，the surface crack rate，the surface crack ratio，the average length of cracks，the average width of cracks，the average area of clods and the maximum area of clods show an increasing trend with the layer thickness. In addition，the frequency distribution of the crack length conforms to a LogNormal function. It is also indicated that the fractal dimension tends to increase slowly with increasing the layer thickness while has a good exponential relationship with the average crack width，and that，under the conditions of the corresponding layer thickness，the distribution range of the crack length shows a decreasing trend with the temperature. The crack morphology of Chongqing silt is multi-scale，including macro-cracks，meso-cracks and micro-cracks. The multi-scale cracks in the soil greatly weaken the engineering properties of the soil.
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2021, Vol. 40 
