Dynamic Response Analysis Of Ground Anchor Buttress Grille Dam Under The Impact Of Debris Flow

Debris flow disasters occur frequently in the mountainous areas of China,and the annual casualties and property losses are extremely serious.The disaster prevention work of the debris flow must not be delayed.The ground anchor buttress grille dam is a new debris flow prevention structure derived from the improvement of the traditional grille dam.It has the characteristics of strong interception ability,strong permeability and good stability.At present,with regard to the ground anchor buttress grille dam,theoretical research has been carried out on the aspects of foundation erosion,pull-out force of the anchor system,internal force calculation,displacement and deformation of the grille dam.On this basis,for the theoretical study of the impact dynamic response of the ground anchor buttress grille dam,this article is based on the impact dynamics theory,with the help of nonlinear dynamic finite element simulation analysis software ANSYS/LS-DYNA,the dynamic response of the ground anchor buttress grille dam under the impact load of debris flow and various factors affecting the dynamic response of the dam are systematically analyzed and studied.The main research contents are as follows:(1)ANSYS/LS-DYNA was used to establish a finite element model of block stone impact on ordinary grille dams and ground anchor buttress grille dams.The ordinary grille dam was set as a control group to explore the ability of the ground anchor buttress grille dam to resist impact.The results show that the impact resistance of the ground anchor buttress grille dam is good.Under the impact of the same parameter block rock,the displacement response and bottom support force of the ground anchor buttress grille dam are smaller than those of the ordinary grille dam.The displacement of the ground anchor buttress grille dam can be reduced by 36%~93% compared with the maximum displacement of the ordinary grille dam.When the block rock impact grille column of the dam body,compared with the ordinary grid dam,the reaction force of the bottom support of ground anchor buttress grille dam column is reduced by 80%,and the reaction force of the bottom support of each column is evenly distributed.(2)The influence parameters of the dynamic response of the ground anchor buttress grille dam under the impact of a single rock are analyzed,and explored the impact of changes in parameters such as impact speed,impact mass,concrete strength level,and reinforcement ratio.The results show that the displacement of the dam increases with the increase of the speed and the mass of the impactor,and decreases with the increase of the concrete strength level and the reinforcement ratio.Among them,the impact of the speed of the impactor and the mass of the impactor on the displacement are the most significant.The main peak value and secondary peak value of impact force increase with the increase of impact speed,impact mass,and concrete strength level.As the reinforcement ratio increases,the main peak value of impact force increases,but the secondary peak value decreases.The impact speed and impact mass have the most significant impact on the impact force,followed by the concrete strength level,and the reinforcement ratio has the smallest impact on the impact force.The increased internal energy of the dam structure increases with the increase of the impact speed and impact mass,and decreases with the increase of the concrete strength level,the reinforcement ratio has little effect on the change of the internal energy of the structure.The reaction force of the support of the grille column increases with the increase of the speed and the mass of the impactor,while the concrete strength level and the reinforcement ratio have little effect on the reaction force of the support.The force change of the reinforcement of the grille beam increases with the speed of the impactor,the mass of the impactor,and the diameter of the reinforcement,the increase of the concrete strength level has little effect on the force of the reinforcement of the grille beam.The impact speed and impact mass have a significant effect on the stress of the anchor cable,with the increase of the impact speed and impact mass,the change in the force of the anchor cable is more obvious.However,the increase in concrete strength level and reinforcement ratio has little effect on the stress of the anchor cable.(3)Considering the limitation of single rock impact dam and the randomness of the impact location of the rock,the random impact of the two rocks is used to simulate the impact of the ground anchor buttress grille dam under different working conditions,explored the dynamic response changes of the ground anchor buttress grille dam under the impact of multiple stones.The results show that when the ground anchor buttress grille dam is impacted by multiple stones,the displacement and deformation of the grille column are significantly affected,and the impact has little effect on the deformation of the grille beam.The closer the block stone impact position is to the dam body at the top and side spans,the more impact energy absorbed by the dam body,the greater the displacement and deformation of the dam body.The damage of the ground anchor buttress grille dam under the impact of multiple stones is local damage,and the stress changes of the grille beam under different working conditions are consistent.The maximum stress and strain appear at the location of the impact point,and stress concentration is easy to occur.When rock impacts frame beam,the stress and strain at the impact point is much larger than the end of the frame beam.It is recommended to consider the mechanical model of the grille frame beam as a fixed beam when performing dynamic analysis on the ground anchor buttress grille dam structure.