Analysis Of Monitoring And Numerical Simulation For Settlement And Deformation Of Expansive Soil Embankments

Because of low CBR strength and high natural water content, expansive soil is usually unsuitable to be used as embankment fill of highway directly. And for road building in expansive soil regions, expansive soil excavated is generally treated as waste cut, which results in great damage to local natural environment and great increase of engineering investments. Therefore, combined with the development of western expansive soil project, embankments filled with expansive soil in core were successfully constructed in Nanyou Expressway in Guangxi Autonomous Region, and physical treating technique was put forward by Changsha University of Science & Technology. To validate the rationality and effectiveness of physical treating technique, by the combination of in situ and laboratory tests, field monitoring and numerical simulation, taking the trial embankment as research object, the research on settlement, deformation and stability of expansive soil embankments was carried out.Firstly, basic situation about trial embankment treated with the technique of non-expansive clay wrapping was introduced, and the monitoring schemes of monitoring profile were designed. Through the tracking observation of settlement and lateral displacement of embankment and variation of water content inside slope, monitoring data was analyzed and actual settlement of the embankment was obtained.Subsequently, by conventional laboratory tests, tri-axial tests and in situ tests, the variation laws of between strength parameters c ,φand water content was obtained, the function expression of elastic modulus and poisson ratio changed with overburden pressure and water content was got by regression analysis, which will provide parameters conforming to reality for developing numerical simulation by adopting different soil constitutive models.By using FLAC software of the finite difference method, in the application of Mohr-Coulomb and Duncan-Chang constitutive model, through two loading methods of loading step by step and one time, the settlement of embankments treated physically was calculated and was researched compared with field monitoring data.By way of numerical simulation, numerical model and calculating method agreed with the practical situation were determined and applied as suitable calculation model and method for the settlement of expansive soil embankments. Simultaneously the stability of embankment slope was analyzed by adopting Strength Reduction Method. Finally, by means of the analysis of various factors influencing reasonable core height of expansive soil embankments, using for reference on current controlling methods of allowable settlement of embankments, adopting calculation model and method determined by research, the relationship between maximum settlements and core height was obtained, which will provide references for satisfying the strength and stability of embankments, and using expansive soil to fill embankments as more as possible.