A lot of problems have been occurred during the construction of road on soft ground. These problems are keep appearing even after the construction has been completed. Especially more problems are expected in expanding of the road on soft ground than new road construction.
In case of "Namhae Expressway 2nd Jisun", it has been planed to remove the existing road which was already stabilized for 30 years before applying the soft ground treatment methods. It has also been planning to banking about 5m of ascent from existing road to meet the standards for road ascent slopes. But, in this case, it cause damage the near by houses, factories, railroads due to the soil disturbance due to soft ground improvement and also cause the increase of construction period, poor workability and project cost increase.
But, it could minimize settlement by downgrade of road ascent slope. Differential settlement damage could be mminimized near by median strip through separating lines. If it changes design criteria for the allowable residual settlement depending on soft ground depth then it will be passible to secure easing the construction period through the construction progress simplification. In addition, the stability of soft ground will be ensured as well as workability improvement and cost effectiveness.
However, to expand application of design criteria for changed allowable residual settlement which is applied only to the "Namhae Expressway 2nd Jisun" expansion construction, the real settlement at the time of completion of the expansion and the effects of secondary consolidation settlement should be compared to changed design settlement, and then detailed analysis should be conducted.
In addition, researches and feed back will be required for occurred settlement during operating and road maintenance costs.