Experimental Study On Buffering Effect Of Waste Tire And Different Material Combinations Under The Rockfall Impact

Rockfall is a common geological disaster in alpine and gorge region.In recent years,it has occurred that many rock fall hazards caused by the loss of personnel and property.Many examples shows that the rockfall hazard is of great seriousness and danger.It is very necessary to study in the failure mechanism and buffering protective measures of rockfall hazards.This paper has put forward the waste tire based combination cushion scheme,combiined with silty clay,medium sand,pisolite and other some low resilient materials,based on the investigation of distribution and risk of rockfall hazards.By setting up waste tires between the concrete slab(component being protected)and the impact plate,and buffering material on the impact plate,the double buffer system was formed.This paper changed the buffering material,the waste tires display form and the height of the rockfall,forming 40 kinds of test modes.In each of the conditions,rockfall impact acceleration,bearing reaction force,acceleration and concrete strain under the protected concrete slab was recorded.After analyzing the dynamic response process of the impact test block and concrete slab,the buffering effecl was evaluated.At the same time,this paper calculated the energy dissipation capacity through the load-displacement curves of waste tires which arc obtained by means of static test.The results showed that waste tires can be used in the actual compression of high utilization rate.The main conclusions of this paper are as follows:(1)After comparative analyzing of the buffering cushion surface damage depth under different conditions,the results show:while the impact height is comparatively smaller(less than 6m),the cushion surface damage depth increases rapidly with the increase of the height.While the impact height increases,the cushion surface damage depth is approximate linear with the height.If the sand cushion is used in the actual project,It is necessary to increase the thickness of cushion layer.The four tires placement can effectively reduce the thickness of the cushion layer.(2)After comparative analyzing of the impact force of rockfall under different conditions,the results show:the impact curve shape of rockfall impact on the cushion and direct impact on the concrete slab are almost the same.Without consideration of the elastic plasticity of the cushion,the impact force will be estimated too high,which leads to the increase of the cushion weight.Waste tire has a significant effect on reducing the impact force.It will be able to effectively reduce 70%of the impact force based on the original buffering effect if waste tires can be added on the base of traditional cushion.(3)After comparative analyzing of the structure stress status under different conditions,the results show:the energy dissipation capability of buffering cushion is very strong.The bearing reaction force under the combination cushion was reduced by 94.1%,comparing with the bearing reaction force under extreme condition without buffering cushion.Waste tire has a very good energy dissipation effect.It can effectively reduce the structural load and reduce the rockfall impact of the structure at the same time.Also,it can save the engineering investment.The maximum stress under the concrete slab is less than 26MPa,which is much smaller than the yield strength of the steel bar.(4)After comparative analyzing of the cushioning effect of different tire arrangement under different conditions,the results show:the cushioning effect of three tire placement is better than the other two placement forms.It can effectively carry out energy dissipation by fully utilizing the lateral deformation of tire.It can be inferred that the three tires placement form can be used to protect part of key nodes of the building in the rockfall area of some key nodes.(5)After comparative analyzing of the cushioning effect of different cushion material under different conditions,the results show:the medium sand cushion has poor punching resistance performance.If the thickness of the cushion is not enough in the actual engineering,the medium sand cushion will probably suffer punching failure and lose cushioning performance when the height of rockfall is great.So,the silty clay and pisolite cushion is more suitable to be used in the structure protection system in the rockfall disaster area.