The old subgrade has completed the

The old subgrade has completed the consolidation settlement of the foundation under the accumulated pressure of its own gravity and traffic flow on the road every day, while the new subgrade has larger construction settlement and post construction settlement compared with the old subgrade due to no external force. Therefore, it is very necessary to deal with the new subgrade base, otherwise the new and old subgrade will have a large settlement difference, which will lead to the failure of the new and old subgrade splicing. We can solve this problem by displacement method, drainage consolidation method, dynamic compaction method and other common methods. In addition, a layer of permeable material should be laid in the area rich in groundwater. It is also necessary to compact the foundation according to the requirements of the construction specifications, so as to ensure the settlement after construction and reduce the settlement difference between the new and old subgrade.