| Recently,the threat of rockfall to the people has increased dramatically.At present,the prevention and control of rockfall disasters is mainly based on passive protection.Among them,flexible shields are widely used in rockfall protection in complex terrain due to the advantages of high adaptability,low cost and beautiful shape.The steel gantry is the weak link of the flexible shield,and it often breaks before other components during the impact of the rockfall.Vibration-isolating spring support has an excellent vibration effect.By adding vibration-isolating spring support at the lower part of the steel gantry,the mechanical properties of the flexible shield can be improved.Considering the ultimate bearing capacity of the steel gantry and the impact load of rockfall,and discussing the design links of the flexible shield,the design process of the flexible shield with vibration-isolating spring support is proposed.The research contents and results are as follows:（1）The ultimate bearing capacity formula of the steel gantry under the condition of elastic restraint under the impact of any angle is deduced,and verified with ANSYS.In addition,the influence of the strength of the elastic restraint and the impact angle on the ultimate bearing capacity of the steel gantry is discussed.The results show that except for the case where the impact angle is larger,the elastic restraint conditions reduce the ultimate bearing capacity of the steel gantry compared with the fixed restraint conditions.（2）Analyzing the most unfavorable conditions of rockfall impact on the steel wire mesh and steel gantry respectively,and establishing the corresponding calculation model.Analyzing the stiffness contribution of steel gantry,vibration-isolating spring support,and steel wire rope during rockfall impact,deduced the combined stiffness of rockfall impact,and deducing the formula of impact force of rockfall impact on steel wire net by equivalent linearization method;According to the energy principle and considering the dynamic amplification factor,the formula of the peak impact force of rockfall on the steel gantry is deduced.It is verified with ANSYS/LS-DYNA,and the vibration isolation effect of vibration-isolating spring support is discussed based on the peak impact force formula.The results show that the theoretical derivation is safe and reliable;the error of the formula for the peak impact force of rockfall impact on the steel wire net is not more than 20%.The formula for the peak impact force is corrected by considering the amplification factor of 1.25;the impact of the rockfall impact on the steel gantry is more significant,The vertical stiffness ratio has a greater impact on the vibration isolation effect than the horizontal stiffness ratio.The reasonable control of the vertical stiffness ratio and the horizontal stiffness ratio can reduce the peak impact force by22.38%～51.52%,0.83 %～17.13%,respectively.（3）Compared with the arc shape and catenary shape,the parabolic steel gantry is safer and more economical;the vibration-isolating spring support should be arranged in a concentrated manner in a local area;combining with the energy principle,application requirements,steel gantry bearing capacity and overall Stability puts forward the design process of flexible shield with vibration-isolating spring support. |
PDF Full Text Request