Numerical Simulation Analysis Of 3D Wave Field Of Rail Transit In Water-bearing Soil

Rail transit is closely related to people’s production and life.While bringing convenience to people,the vibration impact on the environment cannot be ignored.The development of vibration reduction and noise reduction technology depends on the understanding and grasp of the three-dimensional transmission of vibration in subgrade and surrounding soil layers.In this paper,the field measurement and numerical simulation are used to study the distribution characteristics of three-dimensional wave field in the ground near the subgrade and track under the excitation of train moving load.This paper first introduces the field observation of a subgrade section of Beijing Rail Transit Line 13,and proposes a method to identify the train passing time and running speed from the observation data.The results show that with the increase of the distance from the track,the vibration intensity decreases and the vibration duration increases.High frequency vibration decays fast,low frequency vibration decays slowly.Through the regression analysis of the vibration holding time of the surface measuring points,the passing time of the train is identified,and then the running speed of the train is calculated.The estimated vehicle speed is positively correlated with the PGA of site vibration,which verifies the feasibility of the proposed method.Then,a new method of wave field superposition modeling based on the Green’s function of finite element is proposed to solve the problem of huge calculation of three-dimensional finite element of complex train track soil system.The first step is to decompose the random samples of wheel set load time history into a series of harmonic moving loads;the second step is to establish the rail soil finite element model to calculate the wave field function under harmonic moving loads,i.e.the numerical Green’s function;the third step is to synthesize the wave field under the random load of a single wheel set;finally,the whole train movement is calculated by superpositionaccording to the front and back position relationship of the train axle Wave field under excitation.The reliability of the method is verified by numerical simulation.This method has the advantages of small scale and fast calculation speed,and is suitable for the three-dimensional wave field simulation analysis of rail transit soil on PC.Finally,the vibration of subgrade and surrounding soil under different speeds is simulated and analyzed by using the modeling method in this paper.The variation law of vibration displacement,acceleration and stress on the site surface and subgrade depth direction is revealed.The influence of train speed on vibration intensity and attenuation characteristics is investigated.Based on the observation data and numerical simulation results,a statistical attenuation relation is evaluated,and some suggestions are put forward.