Study On The Effects On Above-ground Buildings About XuDa Railway NieJiaPo Tunnel Blasting Seismic Effect

At present, in the construction of the tunnel blasting excavation is the main method. However, it will inevitably produce blasting vibration during blasting excavation. This threat to people’s lives and property directiy. Therefore, to study the effect of blasting seismic effects on buildings has important practical significance. This paper takes XuDa Raileway NieJiaPo tunnel project as the research object and takes tests, theoretical analysis and finite element analysis method to comprehensively analyzes the characteristics of blasting vibration, blasting scheme and the dynamic response characteristics of buildings under blasting vibration.Firstly, this paper introduced the mechanism, classification and characteristics of blasting seismic waves, and than analyzed the influence factors of blasting vibration damage to buildings. This provides a theoretical basis for the study of the blasting seismic effects on buildings.Then, the paper analyzes the development of blasting scheme combined with the geological and environmental conditions. It provides a reference for future similar projects.And than, this paper is based on the test data to analyze the characteristics of blasting seismic wave and its propagation law, its influence to buildings and apply mathematical analysis software Matlab programming to make regression analysis on Sadov’s formula to obtain the maximum vibration velocity formula of the blasting seismic wave in the process of transmission. This provides a theoretical basis for the study of the blasting seismic effects on buildings.Secondly, we based on the structural dynamics theory to establish the motion differential equations of structural’s one-degree-of-freedom system in the free vibration and forced vibration.We obtained the displacement and the shear formula at the bottom of building structure under harmonic load. It theoretically analyzes the characteristics of blasting seismic effects on buildings and supply a theoretical basis for studying the effect of blasting seismic wave to buildings.Finally, we established a three layer composite masonry structure building finite element model by finite element analysis software ansys. And we get the inherent frequency and vibration model of a building through modal analysis. So we can know blasting seismic wave cannot cause the resonance phenomenon of the building by combining with the blasting vibration testing results and the blasting seismic wave spectrum analysis results. We made transient dynamic analysis on the building structure to study the dynamic response of buildings under the action of blasting seismic wave and found that the maximum principal tensile stress and shear stress occurs mainly in the corner, near the window or the door. This suggests that we should pay enough attention on these positions in building earthquake-resistant. And we also found that the maximum stress value does not exceed the ultimate strength of building materials. It will not cause the damage of structures. The result is consistent with actual observations. So we can conclude that the establishment of the finite element model is reasonable, we can use this model to make analysis and forecast to the influence degree of blasting seismic wave to buildings in actual engineering. This provides a reliable basis for the seismic safety evaluation of building structure.