Construction Application Of Dynamic Consolidation In Reusing Of Old Subgrade

In the rebuilding and widening of old highways, one hot topic is how to make good use of the existing subgrade to have a low construction cost and a short construction period and then reach a highly-efficient and economical aim.In the rebuilding and widening of old highways, the consolidation degree of subgrade between old highways and new widening side changes with the heights of old subgrade and the variance of consolidation is bigger. The standard of compaction degree of old subgrade is different from the one of the exsiting subgrade of freeway so there exists a variance of deflection due to the variance of density between new subgrade and old one. If old subgrade is reused and new subgrade is compacted by layer, there is a big shear stress at the binding site between new subgrade and old one and the binding site will become fragile. Therefore, nonuniform deflection problems between new foundation and old one, nonuniform density problems between new subgrade and old one, the binding section's processing problems between new subgrade and old one are 3 critical technical problems in the reusing of old road embankment. The scientific processing of these 3 problems has an important relation with the stability of subgrade and has a direct effect on the life of the pavement structure.This topic introduces dynamic consolidation method. For old road embankments, a dynamic consolidation is directly used to make the soil of old road embankments denser and achieve the density requirements of the existing specifications. For new subgrade, 2 filling methods are used, and one is to fill the new subgrade 50cm higher than designed elevation and have the dynamic consolidation on the new subgrade to achieve the density requirement, the other to compact the new road embankment by layer after dynamic consolidation on the old road embankment to the elevation of old road embankment and then have the dynamic consolidation twice on the binding site between new road embankment and old one. These 2 methods greatly reduce the problems of 3 kinds mentioned above and make good use of old road embankment and save lots of money and time. This topic acquires original data of old road embankment through lots of field tests and indoor tests and uses a finite element analysis and a test section is performed on the field and finally the paper reasonably gives some construction parameters of dynamic consolidation and the safety distance from the dynamic consolidation site is tested and analyzed and finally the paper presents the safety distance the dynamic consolidation requires on the people and buildings under construction. This will help in similar kinds of construction in the future.