Impact of Small Clearance Bored Pile Construction under Rail Transit Bridges in Soft Soil Area

Abstract

Objective The impact of small clearance construction between bored piles and piers of operational rail transit bridges in China′s coastal soft soil areas is becoming a bottleneck factor restricting urban rail transit planning and construction. Therefore, it is necessary to study the impact of small clearance bored pile construction on the deformation of surrounding strata and bridge piers. Method Taking an ongoing project of urban road pile-slab structure under passing the rail transit bridge in Zhejiang Prov. as example, through designing soil lateral deformation monitoring tests and building a displacement smart monitoring system for bridge and piers, the coordinated deformation characteristics between deep soft soil strata and inclinometer boreholes are analyzed, together with the impact law of bored pile construction on the deformation of surrounding strata and bridge piers. Result & Conclusion To ensure good coordination in deformation between inclinometer boreholes and strata, inclinometer boreholes in soft soil areas should remain for 6 days after the completion of construction. The sensitivity of the silt layer to the construction loading and unloading process is high, resulting in the maximum deformation of soft soil strata induced by construction. Under construction conditions, the deformation amplitude of the bridge piers in three directions is about 2 to 3 times that of non-construction conditions. The drilling excavation process and concrete pouring process have a significant disturbance effect on the depth direction of bridge piers. Therefore, the monitoring focus of construction beneath operational rail transit bridges should be put on vertical displacement.

Keywords

• rail transit
• soft soil area
• bored pile small clearance construction