Estimation of the Effect of Lateral Flow on Piled Bridge Abutments in Soft Ground Considering Piled Slabs as a Countermeasure of the Abutments

The effectiveness of a simple method to estimate the lateral movement of piled bridge abutments due to lateral flow from the safety factor (Fs) of slope stability analysis was studied. This was accomplished through the construction and measurement of actual piled bridge abutments and its backfill, with and without piled slabs as a countermeasure. To do this, a computer program SLOPILE (VER 3.0) considering the lateral earth pressure acting on a row of piled bridge abutment was developed. SLOPILE (VER 3.0) can calculate the slope stability for both planar failure surfaces in infinite slopes and arc failure surfaces based on Fellenius or Bishop simplified methods. SLOPILE (VER 3.0) was utilized to design the piled bridge abutment reinforced by a piled slab at a real site. The piled slab can effectively prevent the lateral flow of soft ground and satisfy not only the safety factor of a slope but also the allowable bearing capacity of piles. To verify the design method, an instrumentation system was adapted. The instrumentation results from a case study clearly showed that the piled slab effectively resisted the lateral movement of a bridge abutment due to placement of backfill. Also, the surcharge loads due to backfill were supported by the piled slab and transmitted to the bedrock through the piled slab.