Impact Of Rockfall And Its Influence On Vehicle-Bridge Coupling System

Due to the requirements of track regularity and route development,bridge and tunnel account for a large proportion in Western Mountainous Regions.Because of geological conditions,landslides and rockfall are very serious there.Especially after the Wenchuan earthquake,the phenomenon of rockfall hitting bridges often occurs.Therefore,it is necessary to study the rock-fall impact and its influence on the vehicle-bridge coupling system.In this paper,the characteristic of rockfall movement,rockfall impact force and rockfall-vehicle-bridge interaction were studied in sequence.Firstly,the slope is classified according to the angular dependence between adjacent slopes,and the movement patterns of rockfall on each kind of slope were analyzed.The movement process of rockfall was analyzed based on kinematic theory.The results were compared with the professional calculation program Rockfall to verify the calculation results.Secondly,based on the dynamic analysis software LS-DYNA,the numerical simulation of rockfall impact on the bridge structure was carried out to obtain the impact force-time history.The impact force of falling rock at different speeds was compared with the result of code formula to verify the accuracy of the simulation results.On this basis,the response of bridge structure under rockfall impact is studied.Finally,the influence of rockfall impact on vehicle-bridge coupling system dynamic performance was studied by the software BANSYS.The dynamic response of bridge and train were calculated when the train passing through bridge under the impact of rockfall.Parametric analyses were conducted to determine the relation of the safety with the speed of rockfall and the impact position.The research results show that:the mean value and maximum value of the impact force will both increase with the increase of impact velocity.However,due to the duration of the collision will also increase with the speed,the mean value of impact force is not proportional to the speed of rockfall.This is different from the specification.The difference of impact position has little effect on the maximum value of impact force,while the duration of collision will be prolonged with the rise of impact position,it will make the mean value of impact force decreased.Under the impact of rockfall,the train’s lateral acceleration,lateral wheelset force,wheel unloading rate,and derailment coefficient increasing significantly.The effect of the collision force on the train’s vertical acceleration is much smaller.And if the speed of rockfall is faster,the impact position is higher,greater the effect on vehicle responses will be.In addition,when the collision occurs,the closer the train is from the impact point,the greater the response will be.