Abstract:There are some earth caves and karst in the airfield runway subgrade of some newly constructed airport,and the bearing capacity of the overburden soil in the subgrade is low. In order to access the stability of the airfield runway subgrade,the mechanical response of the subgrade with and without strengthening after the action of airplane gravity load is analyzed by using the layer-structure model and the elastoplastic finite element method. Under the action of the dynamic airplane load,the large plastic deformation takes place in the overburden soil of earth caves and karst of the subgrade without strengthening. The plastic zone appears around the caves,and the whole subgrade is in the unstable state. After the overburden soil of the subgrade is grouted,or the overburden soil of the subgrade,earth caves and karst are grouted,the displacements and the plastic zone there are greatly reduced,but there is still the plastic zone in the overburden soil of the subgrade,and the vertical deformation of the roadbed is quite large. Thus,other strengthening measures are proposed for the runway subgrade.