Abstract: In expressway widening construction, differential consolidation settlement and mechanical properties between new and old foundations especially soft foundation will cause severe pavement crack; and controlling differential settlement to avoid pavement crack in joint section becomes the key technique in embankment widening project. Focusing on soft foundation treated respectively with thin-wall pipe piles and DJM piles, selecting sections with typical geotechnical condition and comparatively high embankment, by burying settlement plate, a dynamic monitoring has been performed for obtaining the settlement of foundation during embankment widening. The results indicate that(a)the accumulated and differential settlement are both small and the settlement rate is smaller than the controlling standard, which provides basis for differential settlement accessing and (b)the two disposal methods, thin-wall pipe piles and DJM piles, are respectively accommodated for soft foundation with large embedded depth and layer thickness and with small embedded depth and layer thickness; and the treated new and old foundations is turned into fine compound foundation; so, a satisfied result is obtained for foundation widening.

Key words: expressway, widening, soft foundation, settlement monitoring , settlement rate