Abstract: To understand the overlying rock strata caused by filling and abandoned goaf under earthquake, ensuring that the upper surface of subgrade is not due to the earthquake generating additional settlement which affects normal use, the goaf and the overlying rock strata were simulated with filling rate(0.85, 0.9, 0.95) and earthquake acceleration(0.2 g, 0.3 g, 0.4 g). Simulation using PFC3D as platform, modeling of complex strata, and the introduction of filling and the simulation method of earthquake, the overlying rock strata migration, stress, and the surface of the subgrade settlement characteristics were obtained. The additional earthquake surface subsidence law was qualitatively obtained, the relationship among the filling rate, earthquake acceleration and additional settlement were analyzed quantitatively, and so were for the reasons. The working parameters of settlements of highway subgrade were confirmed.

Key words: abandoned goaf, earthquake, upper surface of subgrade, additional settlement, simulation and research