| With the development of China's railway transportation system, an increasing number of shallow tunnels traversing the city areas will be built. As a major city tunnel construction method, drilling-and-blasting method will inevitably generate seismic effect, which affects the project efficiency and threatens the safety of surrounding buildings. How to reduce the blasting damage and blasting vibration as well as how to properly handle the conflict between the engineering efficiency and the blasting-vibration control has become one of the key issues in the city tunnel blasting. This paper puts Chang-Hongling tunnel under-traversing JiangChi town as the project background.According to the dense residences, the complex structure, the low blasting seismic level, and the strict blasting control standard, we successively got the blasting shock absorption technology of the digital detonator by the comparative tests between ordinary detonator and digital detonator. We also guarantee the tunnel to pass through Jiangchi Town safely and fast by adopting the blasting excavation with a large number of the digital detonator. Based on a lot of blasting vibration monitoring and test data, it researches spectrum characteristics and wave attenuation of blasting seismic by numerical simulation, and wavelet transformation technique. The main results obtained from the paper are as follows:1) Ordinary detonator blasting shock tests and analysis①Based on the ordinary detonators blasting shock tests, we found that:the efficiency of full-face blasting is the highest, but the shock is the biggest; the shock in "non-explosive excavation in abdominal pilot hole+controlled blasting excavation in subsequent expansion section" is the lowest, and the efficiency is higher; the efficiency of "on-blasting excavation in the up-steps+down-steps controlled blasting" is the lowest, and the shock is bigger;②In engineering practice, adopting four degree compound wedging cut in slotted section can reduce the amount of each explosives and vibration of blasting can be reduced obviously by 20%～30%.2) Digital Detonators blasting shock tests and numerical simulation①Compared with the ordinary millisecond detonator blasting, blasting vibration caused by the digital detonators can be reduced by 50%-60%,and the perforation efficiency can reach 98%; ②By numerical simulation we found the variation of the surface vibration velocity and displacement. In the velocity field, the vibration velocity of the hollow area is the maximum,the free face is the second, the minimum is the unexcavated area; In displacement field, the vertical displacement of the area over the free face is the maximum, and the unexcavated area ahead of the tunnel face is the maximum in horizontal displacement;②By the number of Digital Detonators comparison tests and numerical simulation, it can be found that:When the total delay time is set at 700ms, short-delay blasting time is set at 3～4ms, the damping effect is the best. 3) Blasting shock wave analysis and propagation of wave①Through the blast vibration filed test and regression analysis on the field data, we get the vertical velocity attenuation law:V=116.8(Q1/3/R)1.59;the level velocity attenuation law:V=100.8(Q1/3/R)1.75; the radial velocity attenuation law:V=94.23(g1/3/R)1.67;②Frequency spectrum and energy of blasting seismic are analyzed to gain the conclusions:In the blasting test, with the increase of the explosives in maximum segment, blasting vibration bandwidth energy increases, and vibration bandwidth will move to the low-frequency vibration band; With the increase in the total amount of explosives, the energy's peak value in blasting vibration signal increases obviously; In the dissemination process, the vibration intensity attenuates is decrease, while the Frequency band is widen, the proportion of total low-frequency signal increases.
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