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Study on the Strength and Stability of Silt Roadbed in Western and Central Inner Mongolia

Author: ZhouTianPing
Tutor: LiangHong
School: Inner Mongolia Agricultural University
Course: Forest Engineering
Keywords: Silt Roadbed Strength Drying and wetting cycle Stability of slope
CLC: U416.1
Type: Master's thesis
Year: 2011
Downloads: 56
Quote: 0
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Abstract

Silt has an extensive distribution in China, it is neither clay nor sandy soil and possesses the distinctive engineering characteristics. The regional features of silty soils enable them to have many unique physical and mechanical properties. The western and central of Inner Mongolia belongs to arid and semiarid lands and distributes a large of area silts. Comparing with other silt areas, it has quite difference in geography environment, climatic and hydrogeology condition, mineral composition of soil and engineering mechanical properties. According to the laboratory test and theory analysis, strength and stability of silt subgrade are researched, it can further deepen understanding of the silt soil basic characteristic.In this paper, taking silt soil of National Road 209(Helin-Qingshuihe) subgrade as the research object, the basic physical and mechanical properties and the change law of deformation and intensity during drying and wetting cycles and slope stability are studied and analyzed. The mainly complete works are as follows:Various basic engineering properties of silt are comprehensively and systematically analyzed and studied, such as grain size analysis, marginal moisture content test, compaction characteristics and CBR. The results show that silt soil can be utilized as roadbed filling, but compaction is much more difficult. Therefore it is essential for controlling water and combination of compaction machinery, so as to achieve the best compacting effect.Unconsolidated undrained triaxial test is conducted under the condition of drying and wetting cycles. The failure patter of samples, stress-strain relationship and strength change laws of silt in different are studied. The experimental results demonstrate that while the high compact degree, less cyclic numbers, low confine pressure condition, samples basically present brittleness damage. Stress-strain curves show weak softening type; otherwise samples show plastic failure, stress-strain curves are close to hardening type. Under the same compact degree condition, cohesion force of silt significantly decreased and angle of equivalent internal friction present the tend of vibration attenuation with the circulation times gradually increases.Under the same circulation times condition, soil strength obviously increased and cohesion force rising range is far obvious than the interior angle of friction.On this basis relationship expression between shear strength parameters(cohesion force, angle of equivalent internal friction)and dry-wet circulation times and degree of compaction are established.Based on the orthogonal experimental design.five different factors, sensitivity to effect on slope stability are analyzed, the results showed that the decreasing order of sensitivity in turn is water content, cohesion force, angle of equivalent internal friction gradient, slope height.

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