Date of this Version
Kim, S., Eun, J., Alhowaidi, Y., and Robertson, D.(2021). Feasibility Study: Alternatives to Prevent Settlements and Bumps at Bridge Approach. NDOT Research Report M106.
This project aims to examine the feasibility of improving the current design practice of the approach slab foundation in Nebraska and the alternative of using geosynthetic reinforcement of soils to prevent the bump issues near the end of bridge approaches via an in-depth numerical simulation study. A large-scale pullout test is also conducted as complementary to provide input parameters for the interaction between the regional soil and selected geosynthetics. Based on the results, it is recommended that the number of grade beam piles could be reduced to 40-50 % of the total number of abutment piles while maintaining the same dimension and length to sufficiently prevent the “bump” issue not only near the interface of the bridge abutment and the approach but also at the interface of the approach and the roadway pavement. In the geosynthetic reinforcement case, 2-3 layers of individual geosynthetic reinforcements at both near the interface of the bridge abutment and the approach and the interface of the approach and the roadway pavement could be recommended to efficiently prevent the bump issue. Unlike individual geosynthetic reinforcement, extended geosynthetic reinforcement is not recommended due to its less efficacy, constructability, and economic reasons. Alternatively, a combination of grade beam piles (current design practice) and 2-3 layers of individual geosynthetic reinforcement near the interface of the approach and the roadway pavement could also be recommended to prevent differential settlements at both areas. Such an approach can also be used for the repair of an existing bridge approach and the roadway pavement. Considering the estimated costs for the installment of grade beam piles and geosynthetics, the alternative design of using geosynthetic reinforcement could be a more cost-effective and economical method compared to the current design practice.