Study On Failure Characteristics Of Sandbag In Sand Pillows Under The Action Of Riprap

The engineering structure of sand pillow combined with riprap is widely used in revetment and beach(bottom)protection engineering to achieve the effect of resisting erosion and siltation.However,during construction,the impact of the riprap is easy to cause damage to the sand pillow,thus affecting the engineering effect.Therefore,in order to study the reliability of the riprap cover sand pillow,this paper establishes the stone water movement model,and carries out the following experimental research: the interaction relationship between the stone and the geotechnical bag under the impact load,centrifugal model test study on the influence of roundness of riprap on the damage of sand pillow,experimental study on on-site riprap cover sand pillow.Finally,theoretical calculations,laboratory tests and field tests are combined,and the following conclusions are obtained through analysis and summary:(1)Accelerate the movement of the stone before entering the water.After entering the water,make the shifting movement and then make the uniform motion.When the throwing height is 0m,the stone is in an accelerated motion with a gradually decreasing acceleration after entering the water,and the momentum and kinetic energy of the stone gradually increase until it is constant;when the throwing height is greater than 2m,the stone is in an decelerated motion with a gradually decreasing acceleration after entering the water,and the momentum and kinetic energy of the block are gradually reduced until constant.As the particle size increases,the energy loss rate of the block to the uniform velocity gradually decreases,but with the increase of the throw height,the energy loss rate is gradually increasing.The duration and duration of the movement of the block in the shifting phase increases as the particle size increases and the throw height increases.(2)By generalizing the shape of the block stone,the throwing test is carried out with the ideal sphere.The test results show that the strength and maximum elongation of the sandbag material after impact are increased with the increase of the particle size and the throw height.The damage will be gradually reduced,and the damage of the sand pillow bag will gradually increase,and the functional relationship between the impact energy and the material strength reduction and the maximum force elongation reduction will be fitted respectively.(3)It is obtained by the riprap centrifugal model test: when the centrifuge acceleration is less than 35 g,the roundness of the stone has a great influence on the damage of the sandbag bag;when the centrifuge acceleration exceeds 35 g,the roundness of the stone will have less impact on the damage of the sandbag bag.(4)Through the field test combined with the theoretical analysis of water movement,it can be preliminarily concluded that in the process of riping,if the depth of the throwing area is sufficient and the stone can reach a uniform motion,the sand pillow will not be damaged.If the depth of the head is not enough to meet the water depth required for the stone to reach a uniform motion,the sand pillow is easily pierced and damaged.If the throw height is less than 1m,even if the water depth of the throwing area is not enough,the sand pillow will not be damaged.