Study On The Influence Of Lacal Coastal Topographic Effect On Blasting Vibration Propagation In Site

Ningde Nuclear Power Phase II Project is located on a small island southeast of the Phase I plant area,and blasting excavation must be used for leveling and negative excavation of Phase II project.Under such complicated geological conditions,in order to improve the blasting construction efficiency reasonably on the basis of ensuring the safety of normal operation of nuclear power,it is necessary to quantitatively analyze the influence of topographic effect of local coast on blasting vibration propagation of site.In order to quantitatively analyze the influence of local coastal topographic effect on blasting vibration propagation in site,the local topography of coast studied in this paper is simplified to in-filled concave landform.The influence of in-filled concave landform on blasting vibration propagation is quantitatively analyzed by studying the mechanism of interaction between various parameters characterizing in-filled concave landform and blasting source characteristics.Among them,the parameters to characterize the characteristics of the in-filled concave landform are the relative width of in-filled concave landform Wr,the relative depth Dr,the relative vibration source distance Xr and wave impedance ratio of filled media k.The frequency of incident wave f is the parameter to characterize the characteristics of explosion source.The parameters that characterize the system’s vibration reduction performance are the system’s vibration reduction performance coefficient E_V.By establishing numerical models in FLAC3D,the interaction and common mechanism of each parameter are analyzed in turn.The results show that:1.The relative depth of concave landform is the most important factor to determine the system’s vibration reduction performance,and affects other geometric parameters’(the relative width of concave landform and the relative vibration source distance of concave landform)effect on the system’s vibration reduction performance.Vibration reduction performance of concave landform system increases with the increase of relative depth of concave landform.2.Optimum effective depth of 20Hz incident wave is 0.75 time Rayleigh wave wavelength,the optimum effective depth of 30Hz,40Hz and 50Hz incident wave is 1 time Rayleigh wave wavelength.3.When the relative vibration source distance of concave landform is fixed and the relative depth of concave landform is less than 0.5 times the wavelength of Rayleigh wave,with the increase of the relative width of concave landform,the vibration reduction performance of the system decreases.When the relative depth of concave landform is greater than 0.5 times the wavelength of Rayleigh wave,there is no obvious difference in the vibration reduction performance of the system under different relative widths.When the relative depth of concave geomorphology is fixed and the depth is less than 0.5 times the wavelength of Rayleigh wave,the relative width of concave geomorphology is 0.25~0.75λR,which is most conducive to improving the system’s vibration reduction performance,the relative vibration source distance of concave landform isλR,which is most beneficial to improving the system’s vibration reduction performance.4.When the relative depth of concave landform is less than or equal to 0.5 times Rayleigh wave wavelength,concave landform is located at 1~1.5λ_R from the source of vibration or 1-1~1.5λ_R from the pseudo-protection point,which is most conducive to the improvement of the vibration reduction performance of the system.5.In the same site,the vertical blasting vibration attenuation of high frequency incident wave is faster.The concave landform with the same size and layout has better vibration reduction effect for high frequency wave.6.The vibration reduction performance of the in-filled concave landform system decreases with the increase of wave impedance ratio between the filling medium and the incident medium.Compared with the in-filled concave landform,the non-filling concave landform vibration reduction system has the best vibration reduction performance.