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Test Study on the Soil Water Characteristic Curve and Strength of Unsaturated Soils and Application

Author: MengChangJiang
Tutor: YangQing
School: Dalian University of Technology
Course: Geotechnical Engineering
Keywords: Unsaturated soil Soil-water characteristic curve Influences Strength Water content Slope stability
CLC: TU411
Type: Master's thesis
Year: 2006
Downloads: 1092
Quote: 18
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Abstract

Nowadays, the engineering development is playing a important role in our country, many important projects, such as the South-to-North water Diversion project, the Special railway lines for passenger transport project, are constructing actively. Unsaturated steep slopes are common geotechnical problems in these civil engineering, in which landslides often occur. Slope failures are caused by many factors, among which water is the most significant one. Rainfall and the shifting groundwater and other factors all can change the water content of unsaturated slopes, however, the most significant distinguish between saturated soils and unsaturated soils is matric suction, which is much important to the unsaturated soils’ strength, the changes of the soils’ water content will bring on the changes of the matric suction, and result in the changes of the soils’ strength. As a result, the research on the relationship among water content and matric suction and the soil strength are of value to civil engineering projects.Therefore, A brief and practical idea for the application of the theory of unsaturated soils is received, namely "water content-matric suction-shear strength—factor of the slopes stability". For the sake of discussing the relationship the water content and the slopes stability, enhancing the application of the theory unsaturated soils, this paper has focused on the following aspects:1. Getting the samples of the remolded residual soils, making many tests of the soil-water characteristic curve, and fitting the results by function, then finding simple and practical formula simulation. At the same time, aiming at the influences of soil-water characteristic curve, they make a series of tests discuss the different influences, provide effective references for the practical projects. After that, the Hydraulic Hysteresis theory was discussed a little.2. The properties of the saturated and unsaturated soil strength were measured through the tri-axial test with remolded residual soil samples, by which some rules of the relationship between soil strength and water content are analyzed.3. The theory and formulas on the forecast of unsaturated strength are Summarized, a reasonable predictive unsaturated soil strength equation is put forward by soil-water characteristic curve and the unsaturated strength formula.4 The analysis on unsaturated slopes stability of different water content were discussed based on soil-water characteristic curve and strength tests, and on the new strength forecast equation in this paper, which can get a rule of the unsaturated slopes stability with the unsteady water content. Pointing out the limitations and causes about the traditional slope analysis methods, educing the unsaturated theory that is of great value for the slope engineering, which will provide a reliable theory reference for the soil slope constructioru design and assessment management.

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