| With the development of national economy and infrastructure construction in northwest China,more and more railway sections are designed as elevated structures.Heavy-haul trains are developing in the direction of large axle load and high speed,which makes the surrounding environment vibration induced by vehicles running on viaducts more and more serious.As a result,the influence of vibration on the safety of buildings and comformability of human along the line is increasing,especially in the northwest alpine region,the dynamic stability of slope under freeze-thaw environment is also involved,which seriously restricts the development of Heavy-haul Railway in China.This paper is based on the project of National Natural Science Foundation of China: the evaluation of the impact of heavy-haul trains on the vibration of structures along the line and the study of the vibration reduction system.The vibration of surrounding structures induced by Heavy-haul Railway Viaduct is taken as the main line.Based on the measurement and analysis of several typical sections of Shuohuang Heavy-haul Railway,the analysis model of vehicle-viaduct-site-building system is established by using random vibration theory,and the prediction formula of the vibration propagation and attenuation law of the surrounding site of viaduct is put forward.Combining with the relevant standards at home and abroad,the vibration response of buildings around viaduct and the dynamic damage of freeze-thaw slope at bridge-tunnel junction are evaluated.In view of sensitive buildings in key sections,reasonable vibration reduction(isolation)measures are proposed.The main research contents are as follows:A theoretical analysis model of environmental vibration transmission chain of Heavy-haul railway viaduct system is established based on random vibration theory.The power spectral density functions of the forces acting on the bridge deck,the piers acting on the ground,the ground response functions and the vibration responses of the buildings under the multi-point excitation of the piers are obtained respectively.The theoretical analysis model is validated by the measured values of site velocity power spectrum,and the vibration propagation law of vehicle-viaduct-site-building system under the influence of different factors is revealed.Based on the vehicle-bridge coupling vibration equation and the most dangerous arrangement of ZH live load,a method for identifying dynamic loads of simple supported bridges is proposed.By establishing the vibration equation of the train-bridge system,introducing the dynamic load coefficient of the train,and combining with the measured deflection time history of the bridge span,the dynamic load coefficient of the train is obtained.Combined with the static load of the code,the dynamic load of the train is identified.The results show that the calculation method of train dynamic load proposed in this paper makes up for the problem that the dynamic effect of train on bridge is not taken into account in the existing standards.The attenuation law of ground vibration wave around heavy haul railway is studied,and the prediction formula of ground vibration velocity induced by heavy haul railway viaduct is put forward.On the basis of measurement results,a three-dimensional computational model of viaduct-pier-site system is established.The improved Sadowski formula is reasonably introduced to fit the relationship between the peak particle vibration velocity of ground points and the distance from bridge axle,vehicle load and speed.The concept of energy index is put forward in the formula,and the relationship between energy index and wagon speed and wagon weight is established.The vibration characteristics of buildings around heavy haul railway are analyzed and the vibration response of buildings is evaluated.Based on the measured data of Shenshan elevated section and subgrade section of Shuohuang Railway,the vibration responses of buildings under different axle loads and speeds are analyzed.It is found that the vibration of buildings along the railway is mainly low-frequency within 40 Hz,and the predominant period of buildings near the viaduct is more obvious.Compared with the limit value stipulated by GB/T50355-2018,the vibration of some buildings near the track is close to or beyond the limit value,and corresponding vibration reduction measures should be taken.The influence of train dynamic load on the vibration and damage mechanism of the tunnel face slope of Dongfeng Tunnel along the railway in alpine region are analyzed.Based on the indoor freeze-thaw cycle damage test and mechanical test,the variation of physical and mechanical parameters of rock samples with different porosity under different freeze-thaw cycles is analyzed.Microscopic damage evolution characteristics of rock samples with different water content under different freeze-thaw cycles were analyzed by scanning electron microscopy(SEM).A tunnel-slope model considering RHT damage of rock mass is established to analyze the dynamic response,deformation characteristics and damage distribution of rock slope under the combined action of train dynamic load and freeze-thaw.Vibration reduction measures of buildings induced by Heavy-haul Railway viaducts are put forward.The effectiveness of three-dimensional vibration isolation bearing and honeycomb wave blocker on environmental vibration wave are studied,and the vibration characteristics of buildings with different parameters on site are analyzed.The validity of the new three-dimensional vibration isolation bearing composed of butterfly spring group and vibration isolation rubber bearings to control the three-dimensional vibration of the frame structure is verified.The influence of location,depth,filling material and filling mode of honeycomb wave blockade on vibration isolation effect are analyzed.The results show that three rows of Rubber-filled honeycomb wave blockades can effectively reduce the low-frequency vibration of the site in the vicinity of the proposed protected area. |
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