| Passive flexible rockfall barrier as an important rockfall disaster protection structure,involving complex large deformation,large strain,transient problems.There are a complex synergistic effect of the components,energy dissipation device energy consumption and other issues.In recent years,experts at home and abroad have studied the mechanical behavior of intercepting mesh and energy dissipating components more extensively,however,the analysis of the numerical simulation calculation theory for the impact mechanical response of flexible rockfall barrier have improved.Study of different impact modes impacting flexible rockfall barrier is not sufficient.Accordingly,in this paper,in order to solve the problem of the rotating projectile impacting flexible rockfall barrier system,overall deformation and force changes of the components of the flexible rockfall barrier without considering the rotation effect and considering the rotation effect were studied.To reflect the superiority of the optimized design,main contents and conclusions are as follows(1)Research background and current status of the flexible rockfall barrier were analyzed.Mechanical behavior of the components,impact mechanical behavior of the system and numerical optimization simulation analysis were discussed.Defects of the existing research were pointed out,and research content and technical route of this paper were determined.(2)Deformation mechanism of the projectile impact and the ring-net passive flexible rockfall barrier was described,and numerical simulation method was introduced.According to the numerical simulation method,test results of ring-net passive flexible rockfall barrier designed were in good agreement with the simulation results.the maximum error of the tension force was 6.3%.Displacement and force of ring-net passive flexible rockfall barrier under the impact of rockfall were related to impact process force transmission mechanism.Oscillating effect of the wire rope was related to the deformation and performance change of the ring-type brake energy dissipater.(3)For the ring-net passive flexible rockfall barrier without rotating projectile impact,as the impact angle of projectile impact increases,displacement of rockfall in the protection system moving outward increasesd,and vertical displacement decreased.Internal force of the ring mesh was mainly concentrated in the impact point area.there was no obvious slip jamming and wire rope pulling off phenomenon in each component.Wire rope tension force of each system did not exceed 120 k N,and it was within the safe range.It avoided the possibility of pulling off.(4)For the ring-net passive flexible rockfall barrier with rotating projectile impact,degree of impact of clockwise rotation of rockfall on the flexible rockfall barrier system safety performance was greater than that of counterclockwise rotation.Considering setting the initial impact kinetic energy about 3/4 of the system protection energy level and the most unfavorable situation impacting posts stress has reached 173.45 MPa,upper pulling anchor rope tension oscillation degree was larger.Design process was considered to enhance the overall system energy dissipation capacity,it reduced role of wire rope tension and its impact on the steel posts.(5)In response to the safety performance problems that may occur during the impact of the above two cases of projectile impact,a new type of ring-net passive flexible rockfall barrier was designed by applying similar flexible protection system design advantages to ring-net passive flexible rockfall barrier design.Designed new type of ring-net passive flexible rockfall barrier was compared with the original structure.From the view of overall performance,the new type of ring-net passive flexible rockfall barrier had unique elastic buffering performance.Maximum buffer deformation of the new structure was increased by6.62%,and maximum impact force was reduced by 5.45% compared with the original structure within the boundary conditions.It strengthened the buffering capacity of the system against the thrown rockfall and improved the overall protection performance.Under the deformation effect of piston rod and edge support rope setting on the impact force transmission dispersion effect,mesh and posts stress and wire rope tension were reduced.Safety performance of the ring-net passive flexible rockfall barrier has improved. |
