Study On Blasting Vibration Effect And Characteristic Of Rock Dynamic Damage For Blasting Excavation In Nuclear Power Station

In construction site of the blasting for rock excavation on land to open channel project in Taishan Nuclear Power Station, Guangdong, China and rock blasting and foundation excavation at Fangchengang Nuclear Power Station, Guangxi, China, rock blast vibration has been monitored. The regression analysis on relationship between vibration velocity, explosive mass and propagation distance of seismic wave are carried out by using the classic experience formula of M.A Sakowski. At the same time, the attenuation laws of different directional vibration velocity induced by rock blasting are obtained through regression analysis to practical test data on the ground of sluice gate and rock foundation. To ensure the safety of buildings, it is of great significance to control maximum charging weight in advance for different monitoring point which has a distance with center of blasting. Based on blasting vibration monitoring data, the Characteristic of blasting vibration of sluice gate and rock foundation has been studied. As for those monitoring data, peak particle velocity declines rapidly when monitoring point is close to the center of explosion and it decreases slowly as the distance increases. For blasting vibration signal of sluice gate, the results of blast vibration velocity to vertical direction are generally larger than horizontal radial and horizontal tangential direction. However, to blasting vibration signal on rock foundation, the results of blast vibration velocity to vertical direction, horizontal radial and horizontal tangential direction are close each other. By this taken, it is necessary to statistically analyze the value of horizontal radial, horizontal tangential and vertical peak particle velocity every time and obtain the maximum value among of different directional vibration velocity as blasting safety control standard in the Blasting monitoring process, controlling nicely blasting vibration effect by obtaining maximum charging weight as a result of regressive analysis on blasting safety control standard.The spectrum characteristics of blasting vibration signal is analyzed by using matlab software on fast Fourier transform (FFT) as for as on land to open channel 1th project in Taishan Nuclear Power Station, which show blasting seismic wave’s vibration frequency mostly vary from 10Hz to 50Hz that are much higher than natural frequency of lock gate 5.26Hz and common civil buildings varying from 2Hz to 5Hz; so resonance effect will not happen generally. In the processing of obtaining wavelet component to same blasting vibration signal by using different wavelet basis function of wavelet transformation, the result of wavelet decomposing is related with wavelet basis function. All the relative error between raw signal and reconstruction of signal are from 10-11 to 10-12 which meeting precision demand. Blasting vibration signal is decomposed to nine wavelet component, the energy sum of 5th,6th,7th wavelet component occupy 94% to total energy.Three-dimensional energy spectrum is drawn by sym5 wavelet basis function, from which we can know that main energy of raw blasting vibration signal is in the region of 0.125s-0.60s and 10-75Hz.Moreover, Hilbert-Huang transform and empirical mode decomposition is used to analyze vibration signal, which is decomposed to eight IMF component and one surplus. All the relative error between raw signal and reconstruction of signal are from 10-15 to 10-16 which meeting precision demand. It show that C2, C3, C4, C5, C6 components are main components of raw blasting vibration signal by the analysis of power spectral density(PSD) to each component and raw signal.Three-dimensional energy spectrum is drawn, from which we can know that main energy of raw blasting vibration signal is in the region of 0.125s～0.625s and 10～80Hz in accordance with the conclusion of wavelet transform.Rsearchers have conducted six groups of sound wave tests in site of rock blasting and foundation excavation at Fangchengang Nuclear Power Station before and after each blasting. The change rate of sound wawe travel speed through rock mass can thus be obtained and η=10% is regarded as critical damage value of bedrock. Acquiring damage degree and damage characteristic of bedrock by measuring the damage depth, thereby the safety threshold is put forward by analyse attenuation law of vibration signal and characteristic parameters of damage. According to requisition of damage depth to different layer of excavation, the peak ground velocity at a distance of 30m from the center of explosion and single-stage maximum charge weight is known. The research achievements have some guiding function and coclusions from the analysis can be for reference to blasting design and blasting construction.