Effect of Sand Mining on Bridge Capacity and Safety under the Bridge

Abstract

Sand excavations at river beds have compromised the safety of several bridges in recent years. An expressway that connects a huge line bridge is selected as the research object in this study. The phenomenon of the excessive digging of river sand under a bridge is considered, and the influence of the development of bridges on bridge carrying capacity and safety is studied through theoretical analysis, numerical simulation, and field test. Research results show that dredging under the bridge has reduced the bearing capacities of pile tip soil and single pile, but has less effect on the deflection and bending moment of the pier stud and the mid-span deflection on the girder. When test vehicles run on the bridge, the increase in the vertical and portrait dynamic displacements of the sand excavation bridge pier top is less than that of the sand bridge pier. Braking will result in a significant increase in dynamic displacement compared with the working car test data. Experimental data on passing cars are considerably larger than those on the traction test vehicle, and passing cars are seriously overloaded. Under the action of test vehicles and passing cars, the dynamic deflection change of the girder mid-span is not evident. Vehicle weight is the main factor that influences the vertical displacement of the pier top. When a vehicle brakes, longitudinal braking force is the main factor that influences the portrait displacement of the pier top. Braking on the bridge is highly detrimental. Therefore, measures such as speed limit, weight limit, and reinforcement should be taken to avoid water scouring and to ensure the safety of the bridge structure.