Abstract: To avoid that mining impacts on the settlement of above highway roadbed, goaf treatment schemes were put forward, such as roof blasting, filling mining and filling mining+roof blasting. According to the rules it is set that the subgrade settlement limit is 0.3 m, and filling rate is 0.85, 0.9 and 0.95. PFC3D explosion model to simulate the blasting was introduced, 7 schemes were put forward for simulating methods of filling body, and the 7 schemes were implemented. The simulation results show that the igneous rock 4 in rock migration process has the function of inhibitting the movement of the overlying strata. The influence of filling mining + roof blasting on the land subsidence is obviously lower than using the filling mining alone. The goaf treatment schemes meeting the requirements to limit the settlement are: Filling mining (filling rate is 0.9 and 0.95), and filling mining + roof blasting (filling rate is 0.85, 0.9 and 0.95).

Key words: goaf treatment, existing highway subgrade, settlement limit, simulation and study