In order to solve the problem of blasting demolition of tall reinforced concrete water towers in restricted space,a vertical in-situ blasting demolition technology was developed.The impact failure mechanism,collapse process and touchdown vibration of the water tower were analyzed comprehensively by means of high-speed photography,vibration monitoring and numerical simulation.It was found that the collapse process of the tower by vertical in-situ blasting demolition is similar to free fall motion with an acceleration of 9.4 m/s2 calculated by regression analysis,which was slightly smaller than the gravity acceleration.By using the “separated” finite element model,the collapse process of the water tower could be approximately simulated and the impact time of each section cylinder could be accurately captured.In general,cumulative damage by multiple impacts is the main characteristic of the complex failure process of the water tower,which can be simulated by the No.159 concrete material model.The main frequency band of the vibration is mainly concentrated in the range of 5~60 Hz.The high frequency part of the vibration signal attenuates rapidly,and the energy is mainly concentrated in the low frequency part.Moreover,the total energy of the vibration signal decreases significantly with the increase of distance.The test results show that the successive vertical collapse of the tower and the simultaneous blasting on the top water tank can control not only the collapse range of the tower,but also the touchdown vibration and blasting dusts.