Shakingtable Test Research On Steep Slope Bridge Pile Foundation And Its Supporting Structure

Western of Sichuan has a complex terrain and is also geologically active,which makes it one of the most serious areas of earthquake disaster in China.High steep slopes are numerous in these areas,so the bridge foundations of many railway lines will inevitably be located on high-steep slopes and landslides,rock piles and other poor geological bodies.Many high steep slopes are prone to landslides under earthquake,thus causing serious damage to the pile foundation of the railway bridge on the slope.Therefore,it is very important to study the seismic response characteristics and the structure internal force distribution of the pile foundation and its supporting structure under the action of the seismic effect.This paper aims at the response characteristics and internal force distribution of pile foundation and supporting structure of railway bridgeson high steep slopesunder earthquake action.Taking the construction of a large bridge railway project of a certain railway line as background,and by using method such as data research,shaking table model test,FLAC3D numerical simulation and so on,dynamic response characteristics and structure internal force distribution of pile foundation and its supporting structure under earthquake could be studied.The main conclusions are as follows:(1)Under the action of earthquake,the model slope will undergo shear deformation.From the top to the foot of the slope,the incremental amplitude of each measuring point is getting smaller and smalleralong the horizontal direction due to the reinforcement of the anti-slide pile.(2)Under the action of earthquake,the acceleration response is amplified by the slope,and the amplification effect becomes more and more obvious with increasing elevation.The time-history of acceleration shows a "hysteresis effect" phenomenon,and the response on higher position lags behind the lower position.The seismic response of adjacent soils strengthened by bridge piles and anti-slide piles is obviously inhibited.(3)In the vicinity of the interface between the bedrock and the slip body,with the increase of seismic load,the earth pressureof the pile foundation along the pile from top to bottom shows an irregular distributionof first increase and then reduce as the depth increases considering the pile-soil interaction.Anti-slide pile back earth pressure gradually become smalleralong the pile below the sliding surface,but above the sliding surface the earth pressure gradually become larger along the pile.With the increase of seismic load,the soilat the back of the anti-slide pile will produce a certain amount of soil resistance.The following parts of the sliding surface of the pile may be slightly rotated or voided.Therefore,attention should be payed to the control calculationof the turn angle when designing projects.(4)Under earthquake load,as the slope reinforced by the anti-slide piles,the bending momentof bridge pile foundation is relatively small as a whole,and the moment is getting smaller from the inside of the pile to the outer pile foundation at the same height of the pile.Part of the anti-slide pile embedded in the bedrock is similar to the cantilever beam,and the internal force distribution is similar,too.The bending moment of the anti-slide part above the bedrock decreases with increasing height.With the increase of seismic load,the deformation of the pile near the extreme point of bending moment will occur plastic hinge damage.Therefore,when it comes to seismic design,attention should be payed to the calculation of bending bearing capacity of pile at sliding surface.