Vibration Propagation of Dynamic Compaction in Widening Highway Foundations

Dynamic compaction is an economical and effective method to improve foundation conditions. When widening the highway foundation, it is unclear whether the law of dynamic compaction vibration affects the original subgrade and structure, which restricts the use of dynamic compaction technology in the highway foundation-broaden project. By using free losslesss audio codec (FLAC) 3-D numerical calculation software, a dynamic compaction vibration finite difference model was built to analyze the dynamic compaction vibration propagation law of the roadside foundation in the subgrade and pavement structure. At the same time, the vibration acceleration of the key points and the rammer subsoil dynamic pressure value were made as double assessment indicators. The dynamic compaction vibration response of the subgrade and comprehensive evaluation of the foundation reinforcement effect with different parameters were obtained. Through the indoor model test, the reliability of the numerical analysis was verified. The tamping energy of 1500 KN m, drop height of 6 m (corresponding rammer weight of 25T) and rammer diameter of 1.5 m or 2 m are used in the test. The result showed that a good foundation reinforcement effect can be reached as well as the minimal vibration effects on the surrounding environment. Compared with flat terrain, the dynamic compaction vibration acceleration attenuation at embankment toe is more significant. For all, the pavement structure vibration accelerations tended to be a rapid decay. The medial maximum acceleration reached to 3.9m/s2. The compaction vibration's acceleration of road base and sub-base does not significantly change, which both are less than the surface layer.