Study On Seismic Response Of Bridge Foundation Reinforced With Stabilizing Piles On Steep Slope

Some bridge piers are inevitablely located on high steep slope such as landslide,talus,high embankment by the influence of engineering geological conditions.In order to control the forced deformation of bridge piles in earthquakes,the stabilizing piles are widely used in the seismic protection project of bridge foundation in steep slope.In engineering practice,it is necessary to take the slope effect into consideration,the soil is asymmetric distribution in two sides of bridge foundation and the backside soil exert pressure on bridge piles.On the other hand,there is interaction between stabilizing piles and bridge foundation,including the rear-row stabilizing piles transfer some landslide thrust to bridge foundation,and the bridge foundation share some extra horizontal load to front-row stabilizing piles.Meanwhile,the bridge pile deformation is affected by the seismic response characteristics and failure form of steep slope,the bearing state of stabilizing piles and so on.As there is rather scarce experimental investigation on bridge foundation reinforcement with stabilizing piles and other aseismic retaining structures,it is lack of relevant literature and technical datas,and the design principles of stabilizing piles are rather vague,many design schemes emphasize the engineering experience or empirical calculation,the optimization design of stabilizing piles remain stagnant on bridge foundation reinforcement in steep slope,it seriously restricts the construction quality in seismic fortification area and brings potential threat to people lives and property.It is imperative to carry out the experimental research of strengthening bridge foundation with stabilizing piles in steep slope,make rational analysis of seismic response of bridge piles,stabilizing piles and steep slope,optimize the similar design as soon as possible.In this paper,the model tests were regarded as the analytical object that the stabilizing piles were acted to strengthen bridge foundation in anti-slide section and slide section.According to the large shaking table model tests with different scale ratio,the deformation characteristics of bridge piles,front-row stabilizing piles,rear-row stabilizing piles were analyzed in vibrations of different frequency and peak acceleration,the spectrum response and seismic characteristics of steep slope were discussed combined with the failure development.The influence of stabilizing pile position was analyzed by three-dimension dynamic simulation in bridge foundation reinforcement,the optimum design and particular steps of bridge foundation reinforcement with stabilizing piles were provided by summing up main influence factors.According to the forced deformation characteristics of bridge piles in steep slope,the mechanical model and assumed conditions were established,and the calculation method was studied.The main research contents are as following:(1)The shaking table test models of bridge foundation reinforced with stabilizing piles in steep slope were conducted,the similarity design of physical parameters was carried out by dimensional analysis.According to the test purpose and experimental conditions,the microconcrete piles and geotechnical material were prepared,moreover,the span load simulation,seismic wave loading,boundary treatment were scientifically launched,and the whole set of experimental design was obtained.(2)On the basis of shaking table model tests of bridge foundation reinforced with stabilizing piles in anti-slide section and slide section,the forced deformation characteristics of bridge piles,front-row stabilizing piles,rear-row stabilizing piles were analyzed in vibrations of different frequency and peak acceleration,the seismic reinforcement effect of stabilizing piles and the damage characteristics of steep slope were discussed,the unloading effect and failure mechanism of rear-row stabilizing piles were deeply analyzed.(3)The filtering effect,response characteristics of natural frequency,frequency band coupling effect of slope soil were studied by analyzing frequency spectrum of acceleration-time curves,the dynamic response of bridge foundation reinforced with stabilizing piles on steep slope was obtained by analyzing nephograms of PGA amplification coefficient and soil strain in earthquake vibrations of different frequency and peak acceleration,and the response characteristics of different soil strain were summarized.Moreover,the phosphor bronze strip used in measuring the soil deformation was verified,and the qualitative relationship between soil damping and seismic frequency was discussed,the change law of landslide thrust of plastic silty clay was studied by combining with the space amplification theory of seismic waves.(4)According to the large shaking table model test results of bridge foundation reinforcement with stabilizing piles on steep slope,the three-dimensional simulation models of prototype worksites were established,the influence of front-row stabilizing pile location,rear-row stabilizing pile location on forced deformation of bridge foundation was analyzed,the seismic interaction of bridge foundation and stabilizing piles was summarized by studying the main control factors,and the change law of forced deformation of stabilizing piles was obtained.The optimum design principles of bridge foundation reinforced with stabilizing piles were suggested by considering earthquake response of steep slope,meanwhile the safety thresholds of bridge foundation and stabilizing piles in active service were put forward.(5)On the basis of analyzing the forced deformation of bridge piles on steep slope,the mechanical calculation model and basic assumptions were suggested which regarded the displacement and deformation of bridge pier,horizontal soil pressure as the boundary conditions.The backside bridge pile was set as the analytical object,the calculation result was based on the corrected superposition method,and the feasibility of calculation method was verified by comparing theoretical results and three-dimension simulation,moreover,the change rules of correction factor along with earthquake intensity were discussed.