Abstract: Based on model experiment and UDEC simulation combined analysis method, the deformation characteristics and damage mechanism in the process of load-failure of a new type foamed lightweight soil subgrade were studied. The variation of strain, stress distribution and the law of deformation in the process were obtained. The results show that in the process of load-failure of the lightweight soil subgrade, the inner old roadbed is first to deform. When the load reached 175 kPa, plastic deformation firstly occurs in the middle of the subgrade at the left side. The junction between lightweight soil subgrade and old subgrade is easily affected by the interaction between old subgrade settlement deformation and new subgrade failure deformation, resulting in bending shear failure crack, and finally causing damage. The foamed lightweight soil subgrade load-failure mode is from inside to outside with elastic deformation to plastic yield, finally to shear failure (local damage to overall instability). In the longitudinal direction, the stress transfer of the old roadbed is smaller than that of the lightweight soil roadbed. Within a certain load range (less than 100 kPa), the deformation of the subgrade is inversely proportional to the depth of the subgrade.

Key words: foamed lightweight soil subgrade, deformation characteristics, failure mechanism, simulation