The Analysis Of The Reconsolidation Settlement Of The Old Road Soft Soil Foundation Caused By Road Widening

In recent years, with China’s rapid economic growth, some highways built earlier have been unable to meet the requirements of traffic growth and social development, their capacity need to be expanded by providing more lanes. The current designs of the highway widening usually consider adding new lanes adjacent to the existing highway at one side or both sides preferentially, solving the differential settlement and coordinate deformation between the new and old subgrades become the primary problem to solve in highway widening project. Most existing studies show that highway distress after construction mainly appears at the connecting position of new and old roads. However, different to the common recognition, the distress after widening construction of Guang-San highway mainly appears on the pavement of old road, significant longitudinal cracks appear on the pavement of old road.Firstly, this paper summarize the current research on the reconsolidation settlement problems caused by the highway splicing widening on soft soil both at home and abroad, then analysis the relationship between old road reconsolidation settlement and old road subgrade drainage consolidation result, new road composite foundation reinforcement result. First make a description to the fact of the old road soft soil foundation reconsolidation caused by highway splicing widening by means of analysis to the monitoring data during new embankment filling, new pavement construction and after construction of actual highway widening project. And finite element numerical modeling of widen highway cross-section using ABAQUS is followed, the research to the settlement law of three models under different old road subgrade drainage consolidation result and new road composite foundation reinforcement result is made, comparing with the field test result, verified the correctness of the model, and then analysis the effect law of different factors by using the analysis result of the three models.Research shows that:(1)Obvious settlement appeared at the slope toe of old embankment during new embankment filling, and the settlement of old road foundation increase largely during new pavement construction, the old road foundation settlement even exceed the settlement of new road foundation in a period of time. The differential settlement between new and old roads was not big after widening construction.(2) The model both considering the old road subgrade drainage system and the composite foundation below new road shows that the settlement of old road during the new road filling period is the smallest.(3) The result of the model without drainage plates and with reduction of CFG piles under new road matches the field test data mostly.(4) The settlement of the old road pavement during the new embankment filling period has a great relationship to old road subgrade drainage consolidation result and new road composite foundation reinforcement result, the more better the old road subgrade drainage consolidation result and new road composite foundation reinforcement result are, the smaller settlement of old road pavement occur during the new embankment filling period.