Optimizing approach slab design for settlement using soil-structure interaction modelling – A case study

ABSTRACT: The Ministry of Transportation of Ontario (MTO) is considering alternative approach slab configurations to reduce the frequency and severity of pavement surface distress that is commonly observed at approach slabs of bridges. Excessive embankment settlements will result in approach slab settlements that impact the highway rideability and can lead to serious safety concerns. At the Highway 417 overpass at County Road 3, the settlements have been excessive and resulted in significant degradation of the approach pavement, which required speed reduction warnings. MTO therefore undertook a study to assess potential approach slab rehabilitation options at that location. The work undertaken included geotechnical investigations, analysis to estimate the settlements that had occurred and the potential ongoing settlements. Soil-structure modelling was then carried out to evaluate numerous combinations of approach slab and pavement configurations to arrive at the most effective design for the rehabilitation of the County Road 3 bridge approaches and to provide guidance for approach slab rehabilitation at other bridges.