Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Experimental Study on Mechanical Properties of the Canal Foundation Expansive Soil of Water Transportation Open Channel Project in Cold and Arid Regions

Auteur : 崔子晏

Grade : Master 2022

Université : Xinjiang Agricultural University

Résumé partiel
The first phase of water supply project in northern Xinjiang crossed the expansive soil area,that is a cross-basin water diversion project mainly based on open channels.Some of open channels cross the expansive soil area,it has been multiple sliding failure phenomenon since running.At present,scholars at home and abroad have many research results on the mechanical properties of expansive soil in open channels,but the experimental conditions studied are mostly drying-wetting cycles.They believed that the change of water content is the main factor causing the deformation and failure of canal slopes.Considering the influence of freezing-thawing cycles on its mechanical properties,there are few studies.The research on the mechanical properties of expansive soil in open channel projects in cold and arid areas needs to be further explored.Therefore,on the basis of the existing research results,in order to further reveal the failure mechanism of the expansive soil slope of the open channel the first phase of water supply project in northern Xinjiang,the indoor direct shear test,compression test,permeability test,triaxial test and microscopic scanning electron microscope test of the expansive soil under normal temperature and drying-wetting-freezing-thawing cycles of soil are carried out separately,the results of mechanical properties soil are investigated and their affecting mechanism are discussed.Based on the existing non-linear elastic E-B constitutive model,the deformation law of expansive soil under drying-wetting-freezing-thawing cycles is improved.The relevant conclusions of the experimental study are as follows :（1）Experiment on mechanical properties of expansive soil under normal temperature :（1）Direct shear test:The cohesion is decreases with the increase of water content.The internal friction angle decreases slowly when it is less than the optimal water content,and then decreases significantly.Due to dry density increasing,the cohesion increases more significantly than the internal friction angle.（2）Compression test:According to the analysis result,the stable void ratio decreases trend with increasing water content.With increasing dry density,the initial void ratio decreases,and the stable void ratio tends to be constant.With increasing consolidation pressure,the structure type of soil gradually evolves to turbulence and laminar flow structure from flocculation structure,the effect of particle aggregation is obvious,the number and size of pores decreases,and the compressibility of expansive soil decreases,all above are established based on result of scanning electron microscopy experimental test（SEM）.（3）Permeability test:The permeability of expansive soil is strong under low consolidation pressure,and it is small under high pressure（200～1 600k Pa）with an order of 10-6～10-8.The permeability coefficient is positively correlated with the void ratio,which can be expressed in the form of power function.The results of scanning electron microscopy（SEM）show that the loose accumulation structure changes into a closely combined laminar flow structure with increasing consolidation pressure,and the area of pores decreases,which provides the conditions for the permeability coefficient decreases significantly.（2）Experiment on mechanical properties of expansive soil under drying-wetting-freezing-thawing cycles :（1）Direct shear test:With the increase of drying-wetting-freezing-thawing cycles,the fracture rate of expansive soil increases and the shear strength decreases gradually.Among them,the change of cohesion is more significant,and the internal friction angle only has a slight fluctuation.Cohesion is exponentially positively correlated with the number of cycles and fracture rate.（2）Compression test:The relationship between fine microscopic index and compression index under cyclic action was established.With the increase of drying-wetting-freezing-thawing cycles,the overall compressibility of expansive soil increases,and its compression curve can be divided into quasi elastic and quasi plastic segments

Mots clés : Expansive soil ;Drying-wetting-freezing-thawing cycle ;Shear strength ;Compression deformation ;Permeability characteristics ;Microscopic mechanism ;Triaxial test ;Duncan-Chang model ;

Présentation (CNKI)