SETTLEMENT PREVENTION FOR APPROACH EMBANKMENTS

The main cause of differential settlement between approach embankment and structure is considered to be due to compressibility of soil materials. Like the compres- sive characteristics of soil, the settlement deformation is nearly linear to the logarithm of time. Therefore, to reduce the settlement of approach embankment, one measure is to delay the start of paving work in order to allow the occurrence of large-value settlement during the initial stage of construction. Another measure to which the authors are laying stress is that, in order to hasten such a settle- ment during the initial stage, approach embankment in- cluding surcharge portion is constructed prior to the construction of the main embankment, and thereafter the surcharge portion is removed after allowing it to remain there for some time. Using "stress-strain-time" curves which are based on laboratory compression tests of soil, the results of calculation indicated that the preload process is fairly efficient as compared with the conventional process. And field observations of the preload process make reasonable agreement with anyalytical result, ascertaining the effectiveness of the preload process.