Fv. 287 Strandgata: Kjøreplass bru. Road Construction in Quick Clay

Abstract

Rambøll was responsible for the geotechnical design of a pedestrian road through an area with quick clay in Modum municipality Norway. This paper reviews the ground conditions and soil parameters, describes stability calculations and describes the design solution, including protection against erosion and the implementation of each construction phase. The design was done according to guidelines given by the Norwegian Public Roads Administration (NPRA) and The Norwegian Water Resources and Energy Directorate (NVE). The pedestrian road was considered to be an important project to improve the traffic safety for the pedestrians and cyclists in the area and the project was designed as a K1-project according to NVE guidelines. For K1-projects the design must ensure no reduction of the current factor of safety in any of the construction phases.

To determine the soil parameters comprehensive field and laboratory tests were performed. Interpretation of CPTUs and laboratory data indicated a weak layer in the slope, approximately coinciding with the critical shear surface. 3D–effects of the slope were taken into account and the soil parameters were increased to the level where a safety factor of ca. 1,0 was attained. The pedestrian road was located half way up the slope and stability calculations were performed both for the slope above the road and for the slope between the road and the river Simoa below. The design solution included lightweight material for the new road filling to avoid increased loads. Movements in the slope and the pore pressure were monitored throughout the project.