Study On The Dynamic Response Of Surrounding Rock Of Metro Tunnel In Loess Area Under Train Vibration Load

With the acceleration of urbanization process,and the rapid development of urban rail transit system.Subway,as an important part of it,not only promotes urban economic development and facilitates the travel of urban residents,but also brings certain environmental vibration problems caused by subway train operation,which has a certain impact on the normal production and life of people along the line.Based on this,this paper uses the research methods of literature investigation,indoor model test and numerical simulation to study the dynamic response characteristics of surrounding rock of subway tunnel in loess area under train vibration load.the specific research process is as follows: The main contents are as follows:(1)under the action of single point cyclic vibration load,the influence of load amplitude and frequency on the dynamic response characteristics of tunnel surrounding rock and the propagation and attenuation law of soil vertical vibration acceleration amplitude in stratum and surface are studied based on model test and numerical simulation method.finally,the results of numerical simulation and model test are compared and verified.(2)based on the vertical vibration excitation principle caused by track irregularity in the process of wheel-rail interaction during subway train operation,the characteristics of typical track irregularities at home and abroad are analyzed and compared.the time domain samples in accordance with the characteristics of domestic subway track irregularity are obtained by simulating the American five-level track irregularity spectrum under a specific spatial wavelength range.Then,by establishing a simplified vertical vibration model of wheel-rail secondary suspension,the wheel-rail interaction force of subway type B train at different speeds is simulated.On this basis,the single-layer discrete elastically supported track model is further established,and the finite element method is used to simulate the reaction load of subway tunnel roadbed at different speeds.(3)on the basis of single point cyclic vibration load,the vertical and longitudinal vibration acceleration responses of subway tunnel surrounding rock under different train speeds are studied by numerical simulation method from the point of view of time domain,frequency domain and 1cm frequency spectrum.Finally,based on the existing rail transit environmental vibration standards,the speed limit range of metro rail transit operation in urban areas is discussed.