Blasting Induced Vibration Characteristics And Control Index Of Above-ground Buildings At Shallow-buried Section Of XianNv Tunnel Entrance

At present, blasting excavation technique is still a main construction method in great majority of rock shallow buried tunnels. Nevertheless, there are often many engineering structures such as buildings on the surface of these shallow buried tunnels, inevitably, the blasting excavation will give rise to the buildings’ vibration response, which will affect the residents’ life and normal use of the building. In order to control the blasting induced vibration on buildings effectively, we need to research on its characteristics.This text is based on the entrance of XianNv tunnel, among its shallow buried section, to study on the following aspects:the propagation law about blasting seismic wave, and the characteristics of buildings’ vibration response, as well as vibration control requirements, author adopted combinative ways that consist of the field test, the data analysis, the access to information as well as the theoretical discussion.Firstly, via analysing the waveform of blasting seismic wave, we find the intension of blasting-induced vibration on cut hole’s part is the strongest, which reaches the peak of whole waveform. And the results of regression analysis about particle vibration velocity showed that it does not conform to the Sadov’s formula, which may due to the irregular field or the data error.Secondly, after the analysis of No.2 building’s data, we obtained that buildings’ vibration response is bigger to meet critical side than the back side blasting. Statistics showed that, vibration velocity in horizontal direction is bigger than in the vertical direction, while the horizontal one has greater influence on the building, which is the key point of vibration control.And via the research on three directions’ vibration velocity attenuation at No.1 house, following conclusions can be made: vibration velocity attenuation rate stays high when the zero distance is above 40m, while is little below 40m,40m can be taken as a critical value.Then we make a comparision between the attenuation rate of three directions’ vibration velocity, and find that in the interval of (40m-80m), horizontal radial one is the highest, however is the lowest in the interval of (30m-40m). The vibration duration of blasting seismic wave is almost within Is, because of its rapid decay, the main vibration period is short, generally below 0.5s, some even below 0.1s.And the FFT analysis shows that the major velocity amplitude concentrate mainly on frequency range (19.0 Hz-120.0 Hz), while the rest is small.Again, by observing the displacement nephogram on every direction,we find that the vibration displacement at corner, doors and windows, floor surface, wall surface structure near the edge and wall joints as well as base surface is usually bigger, under the condition of only considering one direction’s blasting vibration,the particle displacement increases over time fluctuantly in some axial, while in some other axial is bobbing near the equilibrium position, under the condition of three direction’s blasting vibration together, the particle displacement mostly increases over time fluctuantly, occasionally bobbing near the equilibrium position.Finally,after the analysis of all groups’ computing result of three direction’s blasting vibration,we find the maximum displacement between layers is 1.84 mm, according to the requirements of building’s aseismic deformation calculation,the structure is safe,which is consistent with the observations,it shows that the displacement control indexes of blasting vibration can refer to the seismic design specification, the specification can also be as a useful reference to improve blasting vibration safety procedures in the future.