Research On The Vibration Effect Of Building Collapsing By Blasting Demolition

With the continuous development of urbanization in China,a large number of old buildings(structures)need to be demolished.Due to its high efficiency,economy,environmental protection and safety,blasting demolition technology has become the preferred method for demolishing tall buildings.However,the ground vibration caused by buildings collapse poses a great threat to the safety of the surrounding buildings.It is of great significance to study the effect of ground vibration caused by buildings collapsing in blasting demolition for greatly compensating the inadequacy research and guiding the design theory.In this paper,the ground vibration characteristics and the dynamic response characteristics of the building structure are studied by the combination of practical engineering test,simulation test and numerical simulation.The main work accomplished was as follows:(1)The main theories of the collapsing touchdown process and seismic wave propagation and attenuation process of building blasting demolition are systematically summarized.Then based on the energy method,a theoretical analysis of the generation and propagation attenuation of the collapsing vibration is carried out,and the energy estimation formula at a certain distance from the explosion area is obtained..(2)Based on the blasting demolition project of a large building group in a city,a comparative analysis of blasting vibration and ground-touching vibration was carried out.In view of the shortcomings of the actual engineering test,an outdoor simulation experiment is designed and carried out.From the perspective of the three elements of ground motion,the propagation and attenuation law of landslide touchdown vibration is studied,and the corresponding regression analysis is made.And the characteristic changes of the collapsed ground vibration during the propagation and attenuation process are obtained.(3)Choosing modern signal analysis methods such as wavelet packet transform and HHT analysis,the energy characteristic distribution of different frequency bands,as well as the analysis of instantaneous energy spectrum,marginal spectrum and three-dimensional energy spectrum are studied.The time-frequency characteristic distribution of the ground vibration signal and its variation with the distance are obtained,which provides a visual and effective method for the comprehensive evaluation of the ground vibration signal characteristics.(4)Based on the blasting demolition project of a large-scale building complex in a city,a numerical analysis model is established to study the dynamic response characteristics of the building structure under the ground vibration due to collapse,and the influence law of the three elements of collapse touchdown vibration on the dynamic response of structure,which provides a useful reference for improving the safety evaluation standard of demolition blasting vibration.