Soil Nail Walls Supporting Stub Abutments on Shallow Foundations — A Case Study

The Route 47 Improvements Project in Cumberland County, New Jersey involved widening Route 47 at the interchange with Route 55. The north and south bounds of Route 55 pass over Route 47 through two bridges supported on stub abutments. Three meter high soil nail walls were constructed in front of the abutments in order to accommodate the widening at the Route 55 bridge structures. The abutments of the Route 55 bridges are founded on shallow foundations and rest on top of a 1.0V:1.5H slope. Design of the soil nail walls was conducted using a limiting equilibrium approach. The finite element method was also used to estimate the deformations of the bridge abutments under the various stages of construction of the wall. Based on the finite element analysis, it was concluded that installing a system of tiebacks penetrating the abutment stem and tying it to a stable soil zone far from the back of the abutment would considerably reduce the amount of abutment deformation. The soil nail walls were instrumented to assess the stability of the system during and after construction. The instrumentation consisted of strain gages attached to selected soil nails for measuring the distribution of tension force along the nails and tiltmeters and optical survey points mounted at selected locations on the wall and abutment to detect any rotation and movement. The instrumentation data indicated that the system was stable and that the abutment and wall deformation were minimal and within acceptable limits. Design, construction and performance of the soil nail walls are discussed in this paper.