Structural Dynamic Failure Mechanism Of Energy Dissipation Shed Under Rockfall Impact

The energy dissipation shed is a passive protection structure for falling rocks,but the analysis of its dynamic response and failure mechanism needs further research.Based on the national natural fund project(No.51408084),the dynamic response law and dynamic failure mechanism of the rockfall impact energy dissipation greenhouse are studied with the model test,the wavelet analysis and the numerical simulation as the research means.The results obtained in this paper are as follows:(1)Through the model test method,we reveal the rule of acceleration variation under different rockfall height,shape,sand cushion and quality condition.With the increase of mass and height,the acceleration of rockfall impacting the roof of the shed increases roughly linearly.Under the same working conditions,the acceleration of the roof falling by the spherical falling rock is greater than that of the other rock falling roof.The acceleration of the cylindrical,cubic,rectangular and spherical rockfall roof caves is increased from 25.56 g to 40.73 g,with the falling rock mass of 5kg and the falling height of 2m as an example.Under the above conditions,the acceleration of the spherical rockfall is 18.29% higher than that of the long square rockfall impact roof cave,and the acceleration of the roof of the roof cave is 35.57% more than that of the cubic body falling stone,and the acceleration of the roof of the roof cave is 59.33% more than that of the cylindrical body.The acceleration produced by a stone impacting the shed.The acceleration generated by the rockfall hole(laying the 3cm cushion)is 48.64% less than that of the rockshed tunnel,and the acceleration of the rockfall hole(laying 12 cm cushion)is 77.72% less than that of the rockfall impact shed hole.The data show that the cushion has a very significant energy dissipation effect on the falling stone punching hole.(2)Through the rockfall test of the energy dissipation shed hole,the acceleration variation rule produced by the rockfall impact energy dissipation shed hole is analyzed.The acceleration of the roof of the energy dissipation ceiling can be obviously reduced by the energy dissipation bearing.Taking the spherical falling stone with the mass of 5kg and the falling height of 2m as an example,the acceleration of the energy dissipation shed hole is 52.82% less than that of the roof,which shows that the energy dissipation effect of the energy dissipation shed hole is very significant.(3)Based on the Fu Liye change,the time-frequency analysis of the shock acceleration signal of the energy dissipation greenhouse is carried out,and the frequency,logarithm spectrum,power spectrum and the corresponding vibration frequency of the maximum value of the acceleration signal are obtained.Through spectrum analysis,it is found that the maximum value of the spectrum of the energy dissipation shed tunnel is 59.74% lower than that of the common shed tunnel,so the energy dissipation effect of the energy dissipation shed hole is remarkable.The main frequency of the energy dissipation shed hole is more different than that of the ordinary shed,and the maximum value of the energy dissipation shed hole is located on both sides,that is,49 Hz and 951 Hz,and the maximum value of the ordinary shed hole is located in the middle,that is,436 Hz and 564 Hz.The autocorrelation analysis of the impact signal of the shed tunnel shows that the peak value of the self correlation curve of the energy dissipation shed is 82.57% lower than that of the ordinary shed,and the shock signal of the energy dissipation shed hole has certain periodicity and frequency.(4)Based on the wavelet analysis,the energy distribution characteristics of the shock signals of the energy dissipation sheds and the ordinary shed are compared and analyzed.The comparison results show that the energy ratio of the energy dissipation shed holes is mainly distributed in the frequency band 2 and the frequency band 3;the shock energy of the rockfall in the energy dissipation shed is mainly distributed in the 15.625 ~ 62.5Hz frequency band,accounting for 63.73% of the total energy and the falling of the ordinary shed.The rock impact energy is mainly distributed in the 0 ~ 15.625 Hz frequency band,which accounts for 74.30% of the total energy.It indicates that the medium frequency impact should be considered mainly in the design of energy dissipation greenhouse.The low frequency impact should be considered mainly in the design of ordinary shed.(5)Based on the numerical simulation method,the distribution of the displacement and equivalent stress of the energy dissipation sheds and the failure mechanism of the energy dissipation shed are analyzed.It is found that the equivalent stress of the energy dissipation shed hole is 22.54% less than that of the ordinary shed.The data show that the energy consumption effect of the energy dissipation shed hole is obvious;the numerical simulation analysis is used to analyze each of the energy dissipation effects.The displacement of the roof of the energy dissipation shed hole is 32% to 37.5% less than that of the ordinary shed,and the displacement of the center observation point of the vertical column of the energy dissipation shed hole is 31.43% less than that of the ordinary shed column center observation point,and the displacement of the observation points in the energy dissipation shed hole is less than that of the ordinary shed observation point.The energy dissipation effect of the Ming Xiao energy shed hole is obvious.