Research On The Impact Of Variation Of Reinforcement Ratio And Thickness On The Impact Resistance Of Concrete Slabe

Rockfall,one of the familiar geological disasters in the mountainous area,is featured by randomness,burstiness,unpredictability,etc.With the Development of Western Regions strategy and The Belt and Road,more and more infrastructure will be built in the mountains.It is very important to prevent and control the rockfalls along the road.However,the basic research on the rockfall disasters is relatively weak.On the one hand,there is no technical standard for the of rockfall in our country.At the same time,it is difficult to carry out theoretical analysis alone.So it is very crucial to carry out the experimental study on rockfall impact failure mechanism of reinforced concrete slab,which is of great significance to the rockfall disasters and the practical engineering applications.In order to study the effects of reinforcement ratio and thickness variation on the impact of concrete slab,the test was carried out on the original test bench.Combined with the changing height of the drop hammer,thirty specimens were line of the destructive testing.Acceleration,force and strain time history in the test were collected during the impact process.At the same time,we also obtained and analyzed the test phenomena,the vibration of the test plate etc.The main research work and achievements are as follows:(1)According to the purpose of the study,three different specifications of concrete slabs were designed and fabricated,which included four different reinforcement ratios,two different thicknesses and two plates with steel wire mesh,respectively.Drop hammer was made of steel,and its weight is 99.1kg.(2)Study the impact resistance of the test plates,the results show that:The concrete slabs are most severely damaged under each height;Conventional reinforcement ratio test plate,the bottom damage depth and surface damage diameter are less relevant with reinforcement ratio,and the influence on the impact resistance by changing the reinforcement ratio(plate steel spacing)is weak;Plate,with steel wire mesh(non-conventional reinforcement ratio),bottom cracks and crushed stones it produced are less.By increasing the steel wire mesh at the bottom of the board,the impact resistance of the concrete slab and the rockfall protection have been greatly improved;With different thickness of the test plates,the impact resistance can be effectively improved as the increase in thickness,which can be considered in the actual protection works.(3)The failure process of the test plate under the impact load can be divided into the following stages:when the drop hammer impact to the test plate,the impact load first produces a stress wave in the thickness direction,and the stress wave propagates quickly throughout the thickness of the plate and reflects back and forth.Due to the large impact energy,the tensile waves formed by free surface reflections cause spalling failure.The stress wave effect disappears rapidly and then causes the test plate to vibrate.The inertia effect further destroys the test plate,forming a penetrating hole,while the bottom of the plate produce a series of cracks.Due to the bottom bar,the cracks are no longer the same as the no reinforced concrete slabs,and the main cracks are cracked along the reinforcement.