| At present, there are not any codes about highway construction in loess area in China. Systematic study about the deformation behavior of highway embankment in loess area is lacking. Due to the influence of embankment filling properties, environmental impacts and heavy load traffic, the embankment diseases, which would seriously affect the long-term performance of the highway embankment, including excessive settlement and differential settlement, slope instability and failure of the retaining wall, occur frequently on the embankment, especially on the asymmetric embankment. In order to understand the dynamic deformation behavior of loess embankment, it is necessary to explore the causes of differential settlement and to analyze the dynamic response of the embankment under traffic overloading. This work has great theoretical and practical significance for diseases treatment and prolonging the service life of the embankment aiming at reducing the post-construction maintenance cost. Therefore, field test and numerical simulation are conducted in this dissertation for systematic study of the mechanism of action, deformation behavior, stability and dynamic response of the loess embankment under traffic load.A series of numerical simulations are conducted with the particle flow code PFC2D to study the macro-mechanical response of the soil-geosynthetic interface and the evolution of micro-fabric parameters. Simulation results indicate that the fabric anisotropy has a significant impact on the shear strength of sand. Within the stronger contact force chain, the principal direction of fabric anisotropy has a good agreement with that of principal stress. However, for the weaker contact force chain, the principal directions of fabric anisotropy and principal stress are perpendicular.Field test is conducted at the construction site of Shan-ping highway in Shanxi province considering the lack of long-term monitoring data about highway embankment in loess area. The settlement, lateral displacement, base pressure under the embankment and strain of the geogrid are all monitored. The results show that the lateral deformation of the embankment can be effectively reduced by using geogrid. During the construction of the embankment, the strain of the first layer of geogrid reaches the largest value, following the second layer of geogrid, and the strain of the third layer of geogrid is the smallest.The deformation behavior of the asymmetric loess embankment during construction and operation period reinforced with geogrid and EPS (Expandable Polystyrene Sheet), respectively, are studied through2-D finite element analysis. Parametric study is also performed considering the amplitude of traffic load, the stiffness of geogrid and the vertical spacing between geogrid layers. The results show that the settlement and lateral deformation of embankment can be effectively controlled by using geogrid under traffic load. The larger the traffic load, the better the reinforcement effect. Increasing the stiffness of the geogrid and reducing the vertical spacing of geogrid layers can significantly reduce the lateral displacement of the embankment toe, while the effect is not obvious for controlling the settlement of embankment crown.The stability of the asymmetric loess embankment reinforced with geogrid and EPS, respectively, are studied through numerical simulation. The impacts of embankment filling properties, properties of the reinforcements, elevation difference of the two sides of the embankment and the type of traffic load are all analyzed. The results show that the safety factor and area of plastic region of the embankment reinforced with geogrid are always greater than that reinforced with EPS, which indicates that the stability of the embankment reinforced with geogrid is better than that reinforced with EPS.The dynamic behavior of the aysmmetric reinforced-embankment is studied through numerical simulation considering the effect of traffic load of coal trucks, treating the traffic load as semi-sine wave. Parametric study is also performed considering the amplitude, frequency of traffic load, the interval between trucks and elevation difference of the two sides of the embankment. The results show that the amplitude and frequency of traffic load had greater effects on the deformation of embankment, while the interval between trucks and elevation difference of two sides had less effects. The reinforcement effect of geogrid is better than EPS.The achievements in this dissertation are valuable for the deformation control of highway embankment reinforced by the geogrid in loess area. Also, they have great theoretical and practical significance for improving the design of the loess highway embankment, prolonging the service life of the embankment and reducing the cost of maintenance during the operation period. |
