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China University (2013)

Experimental Study On Salt Heaving Properties Of Inland Sulphate Saline Soil In Cold And Arid Regions

Zhao T Y

Titre : Experimental Study On Salt Heaving Properties Of Inland Sulphate Saline Soil In Cold And Arid Regions

Auteur : Zhao T Y

Grade : Doctoral Dissertation 2013

Université : China University

Résumé partiel
The salt heaving of sulphate saline soil is a complicated academic topic which is highly concerned by geotechnical engineers and researchers. There are many important factors affecting the salt heaving properties, including the macroscopical ones such as salinity composition, soil type, initial dry density, water content, temperature and overlying loads, and the microcosmic ones such as soil structure, inner frictional resistance, cohesion and the soil particle interactions. This thesis carried out the salt heaving tests and theoretical prediction for sulphate saline soil, which was expected to provide theoretical guidance for the evaluation and prevention of salt heaving disaster.As one of the problematic soils in the geotechnical engineering, the saline soil distributes widely over the world, covering nearly100countries and regions from tropical to frigid zones, especially in arid and semi-arid areas. There are many types and largely-distributed inland saline soils in Northwest of China, which characterized with arid and semi-arid environment, high evaporation-precipitation ratio and remarkable temperature variations. These inland saline soils contain some sodium sulphate and possess great potential of salt heaving hazards. Salt heaving seriously affects the stability of highways, railways, industrial and civil buildings on saline soil foundations, restricting the engineering practice and resulting in enormous economic losses. The studies of salt heaving can not only understand the generant mechanism, developmental trend and influencing factors of salt heaving, but also provide a theoretical guidance for evaluation and prevention of the salt heaving hazards.The Gobi saline soil in Guazhou, Gansu province was selected as the typical representative of inland saline soil in cold and arid regions in Northwest of China. Through field investigation, theoretical analysis and laboratorial experiment, this thesis intended to investigate the characteristics of saline soil, calculate the crystal amount of sodium sulfate in soil, and finally explore the impacts of soil type, initial dry density, salt content and water content on salt heaving. Based on the results of test and calculation, this thesis aimed to establish a predictive relationship between salt heaving and soil properties for sulphate saline soil, which could be used for evaluating and preventing the salt heaving deformation. The major conclusions of this study can be summarized as the followings.(1) By field investigation. the inland saline soil in cold and arid regions was characterized, such as the grain size composition, salinity content and micro-structural features. Results showed that there were a large number of coarse particles in the saline soils, and that the major component of soluble salt was sodium sulfate and some sodium chloride. It was found that most of the soil in research area could be divided into sulphate saline soil or sulfurous saline soil ; the salinization degree was middle or weak, only a few soil was classified to strong or super salinization ; and the salts were mainly distributed within the depth ranging from50cm to260cm. Controlled by the local topography and geomorphology, the inland saline soil formation in cold and arid regions was created by the original hydrogeology and climatic condition, with obvious discontinuity and inhomogeneous in horizontal and vertical profiles.(2) The temperature and humidity of the stratum, the most important factors influencing salt heaving, were measured by thermo-sensitive probe and Time Domain Reflectometry (TDR) at a saline soil site during winter and summer in Guazhou, Gansu province. Based on the monitoring data, a mathematical model was established to describe the variation and hysteresis of the soil temperature and humidity with response to the air. It was found that shallow soil was highly influenced by the air, with an obvious variation and a marginal hysteresis in temperature and humidity

Mots clés : saline soil, salt heaving, salt content, water content, sodium sulphate

Présentation (Globethesis)

Page publiée le 21 avril 2013, mise à jour le 10 janvier 2018