Abstract: This paper presents the numerical analysis results of the stability of highway subgrade above an elliptical karstic rock cavern. The factor of safety, development of the potential failure plane, which defined as the connection of the plastic zones and the shear strain rates, are used as the failure criteria. The thickness of the overburden material, shape, horizontal distance of the embankment toe to the cavern on the stability of the highway subgrade above the elliptical karst rock cavern are investigated. The results indicate that the settlement shape of the subgrade is a cone type and the magnitude of the settlement is reduced with the increase of the overburden material. The factor of safety will also increase and tends to stable. The failure patterns of the subgrade above the cavern are: tensile failure of the overburden rock and shear failure of the embankment above. For ellipsoid karstic rock cavern, the roof thickness was less than that for horizontal cavern roof.

Key words: Numerical Analysis, Elliptical Karstic Rock Cavern, Embankment Subgrade, stability, Potential Failure Surfaces