Study on the time-varying response surface of high-speed railway pier displacement caused by new underpass road
In order to solve the problem that it is difficult to accurately predict the displacement change of adjacent high-speed railway piers caused by the new underpass road,this paper established an integrated space-time-varying finite element model of soil-bridge-track,analyzed the sensitivity of the displacement of high-speed rail bridge piers to soil parameters and road design parameters by using the modified Morris method,proposed a simplified fitting method for time-varying response surface functions,and carried out experimental design based on Box-Behnken Design(BBD).Four time-varying response surface functions of pier displacements and sensitive parameters were fitted in two stages.The structural function was constructed based on the time-varying response surface,and the Monte Carlo method was used to randomly sample the parameters for 107 times to calculate the reliable probability of vertical displacement of high-speed rail piers.The results show that when the new road passes under the 32 m span of the high-speed rail simple supported girder bridge in the soft soil area,the rebound curve slope and the Poisson's ratio of the main bearing strata soil,and the subgrade height and width of the new road are the sensitive parameters affecting the vertical displacement of the high-speed rail pier.The simplified efficiency of the time-varying response surface function of the vertical displacement of the middle pier proposed in this paper is as high as about 80%,and the prediction value of the time-varying response surface function for the displacement of the pier top at different times of soil consolidation is very close to the calculated value of the finite element.The relative error is less than 2%,and the prediction accuracy of the response surface function is satisfactory.In the process of soil consolidation,the reliable probability that the vertical displacement of the most unfavorable middle pier less than the standard limit is as high as 99.9%.When the consolidation of the foundation soil layer is stable,the probability of the most unfavorable vertical displacement of the middle pier is 1~1.8 mm.In this paper,the time-varying and discreteness of the mechanical parameters of the soil layer are considered,and the displacement and reliable probability of the existing high-speed railway bridge pier in the process of soil consolidation are calculated by the time-varying response surface function.It provides a reference for the simplified calculation of the displacement of the existing bridge pier caused by similar new construction projects in the future.
underpass the roadhigh-speed rail bridgesresponse surfacetime-changingsoft soilsreliability