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原文传递 Impact of Severe Drought on the Compacted Expansive Clays (Subgrade) in Northern Louisiana.

题名：	Impact of Severe Drought on the Compacted Expansive Clays (Subgrade) in Northern Louisiana.
作者：	Wang, J. X.; Khan, A.; Ikra, B. A.
关键词：	Expansive soils, Pavement roading, Louisiana(State), Moreland clay, Characterization, Constitutive surface, Winkler’s soil model, Virtual load, Closed-form solution, Excel spread sheet, Montmorillonite-smect, Louisiana
摘要：	Understanding unsaturated expansive soil has always been a major challenge for soil scientists and engineers. Due to presence of high quantity of montmorillonite mineral in the Moreland clay in northern Louisiana, structural damage due to soil heave/shrinkage has always been a key concern for geotechnical engineers. In this research, a state-of-the-art characterization of the Moreland clay is presented. It includes the identification of its swell-shrink properties, soil index property measurement, plotting of the soil water characteristics curve (SWCC) to understand the water retention capacity of the clay, development of an empirical equation for its unsaturated shear strength, establishment of its three-dimensional constitutive surface, and the soil heave predictions. The characterization indicated that the Moreland Clay is highly expansive. An analytical method is developed to analyze the heave/shrinkage-induced stresses in pavement. To get the closed-form solutions, a virtual load concept is proposed to analyze a pavement that is assumed as a beam resting on expansive soil, integrating the heave/shrinkage of expansive soil in the Winkler’s soil model. Field observations from a country road in Texas on expansive soil indicated that initiation and propagation of the cracks in the road had a good match with the location where the maximum bending moment was found. Preliminary results have demonstrated that the closed-form solutions could provide a reliable prediction for the bending moment and shear force in the pavement. As compared with the finite element models, the analytical model is significantly simple and more easily implemented. All the equations and calculations are incorporated in the Excel spreadsheet, which is easily handled in pavement design. In this research, expansive soil stabilization is investigated by employing geo-polymer concrete (GPC) and cement as stabilizers, respectively. Three batches of the soil were stabilized with GPC (5-20%) to establish a base line. Results were then compared with the soil stabilized using one batch of cement (10%). It was concluded that even though cement is by far the best soil stabilizer the application of higher percentage of GPC, a satisfactory level of soil stabilization can be achieved as well.
报告类型：	科技报告