Preliminary Study On Vibration Effect Of Collapse In Blasting Demolition Of Buildings

With the rapid urbanization in China,a large number of old buildings have reached the design service life.At the same time,urban planning and design in past gradually exposed deficiencies in the current life,and the demand for large-scale demolition is increasingly urgent.Blasting demolition has become the preferred demolition method because of its high efficiency,economy and safety.But blasting demolition is accompanied by many harmful additional effects,such as blasting vibration,collapse vibration and so on.In this paper,by analyzing the measured data of blasting demolition project,the following studies are carried out and relevant conclusions are drawn:(1)The blasting demolition process of structure and the harm of vibration effect caused by collapse body are introduced.Taking the demolition of a school teaching building by blasting as an example,the data characteristics are analyzed and compared with the "Code for Blasting Safety" and "Code for Structural Seismic Design",which proves the safety and efficiency of demolition by blasting under a group of buildings in accordance with the reasonable design of the code.(2)Analyzing the collision process between the collapse body and the ground,establishing reasonable physical,mechanical and mathematical models,and comparing the collision model with the fault cracking model commonly used in ground motion.The collision model is reasonably equivalent to the near-fault seismic fault cracking model,and the directional effect of the collapse vibration is studied by analogy with the near-fault seismic research ideas.(3)Random selection of reasonable size samples in PEER database,referring to relevant scholars’ research on site classification based on ground motion,AI is trained to use ground motion to distinguish the site types and verify their correctness;furthermore,by improving the algorithm,it can provide sufficiently reasonable and credible results;(4)The energy distribution characteristics of underground collapse vibration in class C site are obtained by studying the measured data of Engineering blasting.(5)Based on the analysis of the safety criteria for collapse vibration in the current "Safety Regulations for Blasting",and referring to the energy distribution characteristics of collapse vibration,a new safety criterion(TEDI)is proposed and its rationality and feasibility are verified.The corresponding relationship between the PGV,frequency spectrum,duration and corresponding TEDI of collapse vibration for a specific site type is given.