| The high-speed railway seismic signal generated by high-speed train operation has important research significance and application value in seismic exploration,train operation monitoring,environmental vibration impact and so on.In order to clarify the various characteristics of the high-speed railway seismic signal and the vibration influence of the building structure in the near field,this paper puts forward the synthesis method of the high-speed railway seismic signal on the basis of the field acquisition test and the field monitoring test.the main frequency range of high-speed railway seismic signal and the attenuation characteristics of particle peak vibration velocity are obtained by time-frequency analysis.In order to explore the hidden propagation law and attribute characteristics of high-speed railway seismic signal,the fractal and multifractal characteristics of high-speed railway seismic signal are verified,the relationship between fractal parameters and propagation medium characteristics is established,and in order to clarify the mechanism of local magnification phenomenon,the cause analysis and location prediction of local magnification phenomenon in high-speed railway pier foundation site are carried out.Based on the analysis of seismic signal characteristics of high-speed railway,based on the empirical formula of particle peak vibration velocity attenuation and the vibration response principle of building structure under harmonic excitation,the equivalent particle peak vibration velocity(equivalent PPV)is proposed and used as a parameter for vibration evaluation of buildings around high-speed railway lines.The main conclusions of the verified research results are as follows:(1)The seismic signal of high-speed railway is mainly excited by the irregularity of train track,the vibration of train system and the vibration of roadbed system,and its propagation and attenuation in the medium is affected by the physical properties and spatial diffusion range of the propagation medium.it has the characteristics of easy collection,large energy,cyclic stability,rich information and local amplification.(2)By simplifying the high-speed train in motion to a moving multi-group point source model,considering the influence factors of high-speed-train seismic signal attenuation,the high-speed railway seismic source function is deduced,and on this basis,the field acquisition test of high-speed-train seismic signal is carried out.the results show that the high-speed-train seismic signal synthesized based on the high-speed railway source function can reflect the energy attenuation characteristics of high-speed-train seismic signal.The analysis results of the time-frequency characteristics of the high-speed-train seismic signal show that the main frequency distribution range of the high-speed-train seismic signal is in 0～20Hz,except that the high-speed-train seismic signal generated by train G924 is locally magnified at the focal distance of 45 m,and the peak vibration velocity of the particle attenuates with the increase of the source distance as a whole.(3)Through self-similarity and scale invariance,it is verified that the high-speed-train seismic signal has significant fractal characteristics,and it is concluded that the fractal dimension of high-speed-train seismic signal can be used as one of the basic methods to identify the abrupt change of propagation medium.Furthermore,based on the corresponding curves of generalized information dimension,scaling index and weight factor,it is verified that the high-speed-train seismic signal has multifractal characteristics.at the same time,it is found that the change of propagation medium has an influence on the multifractal parameters: the continuous wall makes the fluctuation intensity of the high-speed-train seismic signal consistent in the range of 1.5m in front of the wall and 18.5m behind the wall,and within 18.5m behind the diaphragm wall.The proportion of large and small fluctuations of high-speed-train seismic signals has changed greatly.(4)Based on the principle of wave superposition in layered foundation,the superposition and travel time of surface wave and near surface body wave are deduced theoretically.Through the methods of calculation and forward simulation,it is verified that the reflection,refraction and transmission of high-speed railway seismic wave in double-layer foundation are the causes of two local magnification phenomena on the surface,and the prediction of local amplification phenomenon in high-speed railway pier foundation is realized.The error range is less than 3m.(5)Based on the equivalent PPV,the vibration evaluation of the building structure around the high-speed railway is carried out,which shows that the attenuation formula of the peak particle vibration velocity of the high-speed-train seismic signal can reflect the actual attenuation characteristics of the high-speed-train seismic signal in the site,and can be used to predict and calculate the peak particle vibration velocity of the high-speed-train seismic signal at each focal distance.At the focal distance of 45 m,the 0～10Hz equivalent PPV value of G924 train exceeds1mm/s.When there is a building structure with vibration sensitivity and protective value here,the long-term repeated action of high-speed railway train will cause vibration influence and even damage to the building structure.The building structure vibration evaluation method based on equivalent PPV has the advantages of high vibration sensitivity,vibration control for specific building structures,and pre-vibration evaluation before the site selection of the buildings around the high-speed railway.The vibration evaluation method of equivalent PPV can visualize the vibration influence degree and range of the local amplification phenomenon.In the vibration evaluation of building structures along the high-speed railway,attention should be paid to the local amplification phenomenon.There are 34 pictures,15 tables and 102 references in this dissertation. |
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