| Expansive soil is a kind of special clays featured with the Swell-Shrinking characteristic, fissure character and over-consolidation. With the constructions of a great number of high-grade expressways, the hazards and damages of expansive soils to highways become more and more. Especially in highway engineering, rainfall causes expansion soil slope's landslide, which is the most common and most serious engineering problem. Comprehending rainfall infiltration causes variation law of seepage flow fields in expansive soils'slopes, and the influence of fissures to seepage flow fields in expansive soils'slopes, provide theoretical foundation for researching the inherent mechanism of shallow sliding of expansive soil slopes, improving slope design level, and preventing and treating lanslides'hazards.Combined with a expansive soil slope in Nanyou Expressway, understand permeability of expansive soils through laboratory tests, carry out seepage analysis of expansive soils featured with fissures on the condition of rainfall using ANSYS analysis software, comprehend change law of seepage flow fields'distribution in slopes'inner, the main research contents are as follows:1)Through laboratory soil - water characteristic curve (SWCC) test,shrinkage test and saturated permeating test for expansive soil samples from typical expansive soil districts all over China, and summarize SWCC for expansive soil character and influencing factors. By adopting soil-water characteristic curve to predict coefficient of permeability indirectly, get osmotic coefficient in different water content of hoar, grey dark expansive soil and expansive soil in Deng Town of Henan. Then adopt logarithmic model to fit the relation of their SWCC, and the fitting effect is rather good.2)Using ANSYS software,simulate rainfall condition, research seepage flow fields'distribution in slopes'inner with fissures and without fissures, by comparative analysis about seepage results of two conditions,analytical results indicate that the influence of fissures to seepage flow fields must be considered for expansive soil with very small penetrability when carrying out seepage analysis.3)Combined with expansive soil slopes in practical engineering, set master fractures at different positions,simulate rainfall condition, research seepage flow fields'distributing situation in slopes'inner with fissures. The analytical results of total pressure water head's distribution in slope through different rainfall time show that the existence of fissures and cracks is the main factor that causes expansive soil shallow landslides. |
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