Experimental Study On Foam Sandwich Reinforced Concrete Slab Impacted By Rockfall

Rockfall disaster is one of the common natural disasters in mountainous areas.Rockfall disaster has the characteristics of sudden,randomness and destructive power,which seriously threatens people’s life and property safety.With China’s "Silk Road Economic Zone" strategy put forward,a large number of railways,highways,bridges,tunnels and other transportation infrastructure is built in western mountains.After the wenchuan earthquake on May 12th,the collapse of rolling stone enter into the active period,caused a great threat on its impact within the scope of transport infrastructure and human activities.It have becoming an important factor hindering the economic development of these areas,so it is particularly urgent to study on the rockfall disaster.This article aims at improving the impact resistance of the roof and tunnel shed slab.According to the bullet-proof mechanism of composite armor,designed and producted the sandwich reinforced concrete slabs and reinforced concrete slabs back-coated carbon fiber cloth and aramid fiber cloth,a total of 36 specimens.In order to facilitate a large number of destructive tests,our experimental group designed and reformed the experimental platform.Designed and producted the drop hammer,it made of cast steel,the quality of 99.1kg.Carried out the drop-weight test,taking into account the changes of drop hammer impact energy,the thickness of the foam board,the concrete materials of top plate.Collected the data of falling hammer acceleration,plate bottom reaction force,plate bottom acceleration,bottom steel bar and concrete strain,and other time-varying data during the impact of each working condition.Analyzed the impact response modes of sandwich reinforced concrete slabs and evaluated the impact resistance of each type of the specimen.Two kinds of improved foam sandwich reinforced concrete slabs and backfill fiber reinforced concrete slabs were subjected to drop-weight test,analyzed the experimental phenomena and data.The main results of this paper are as follows:1、Under the impact of the drop hammer with 5827.1 J impact energy(height of 6 meter),the impact time of sandwich reinforced concrete slab are longer than ordinary concrete slab.Relative to ordinary concrete slab,the sandwich reinforced concrete slab decreased by 34.2%on the peak of the reaction force and 30.91%on the peak of the falling hammer acceleration,and the damage degree of sandwich reinforced concrete slab is much smaller than that of ordinary reinforced concrete slab.Sandwich reinforced concrete slab with the top plate material selected EPS foam particles instead of stone,its overall impact resistance has improved.2、The test impact on foam sandwich reinforced concrete slab of different impact energy,obtained three impact response modes of the foam sandwich reinforced concrete slabs impacted by rockfall:1)The test slab is not damaged and is always in the elastic phase;2)The test slab local yield deformation,but can be repaired;3)The test slab through the destruction of penetration,can not continue to use.3、The impact test of sandwich reinforced concrete slab with different thickness of foam board show that:the thickness of the foam plate has a certain impact on the impact resistance of the test plate,but in a certain thickness range of the impact of the test is not large;the situation in the foam board is not breakdown of the case of the underlying reinforced concrete slabs are well protected,while in the case of the breakdown of the foam board are more serious damage.4、According to the bulletproof mechanism of composite armor,a layer of tiles(high hardness)laid on the surface of the sandwich panel,and carried out the impact test.The test results show that the impact resistance is stronger.Therefore,designed the improvement program of sandwich slab according to the combination of the two,the test results show that the improved sandwich concrete slab successfully resisted the test drop hammer can achieve the maximum impact energy(height of 14 meter).5、Under the maximum impact energy of the drop hammer(height of 14 meter),the case of carbon fiber cloth is significantly better than the aramid fiber cloth,only the local damage zone;While the use of aramid fiber cloth and without any protective measures of the concrete plate,along the board direction obvious serious penetrating cracks.Due to the high tensile strength of the two composites,the splashing of concrete fragments in the destruction zone is effectively prevented.