Numerical Study On Dynamic Response Characteristics Of Piled Wharf Under Underwater Explosion Impact Load

With the development of national economy,China’s shipping industry has entered a stage of rapid development.Port engineering has become an important part of China’s economic construction in peacetime.As an important part of port engineering,wharf has significant social,economic and political benefits.Once the wharf structure is wrecked,it will bring huge losses to the country and people,and the consequences are unimaginable.Therefore,its safety protection has always been an important part of the overall national security strategy.Taking the explosion load as an extreme load,studying the dynamic response and failure mode of the wharf structure under the impact load of explosion can provide theoretical basis for the safety assessment and anti explosion protection design of the wharf structure,which has important military value and social political significance.In this paper,taking the high pile wharf as the research object,the numerical simulation analysis of the high pile wharf structure under the explosion load is carried out to explore the dynamic response and damage of the structure under different explosion loads,analyze the possible damage mechanism,and further use the numerical simulation method to carry out the damage effect research of the full-scale real high pile wharf under the explosion load.The main research contents and achievements are as follows:(1)Based on ALE algorithm,the numerical simulation of underwater explosion in infinite and near surface is carried out.The numerical results are compared with the traditional empirical formula to verify the accuracy of the numerical simulation results in this paper.By comparing the pressure curves of shock wave in infinite domain and near free surface,it is found that the existence of free surface can weaken the effect of shock wave,mainly reflected in weakening the peak pressure and reducing the pulse width of shock wave shape.The rigid interface has great influence on shock wave,mainly the change of reflection wave at the bottom of water.Through the contrast analysis of the peak value and the pulse width of the irregular reflection area,it is found that the attenuation effect of the free surface on the shock wave decreases with the increase of the sounding;(2)The overpressure of underwater explosion measured in this simulation is larger in the range of small explosion distance(the explosion center distance is less than 40 cm in this paper),but with the increase of the distance between the measuring points,the error between the theoretical value and the simulation value of overpressure is smaller gradually,and when the explosion center distance is more than 60 cm,the curves of the two curves almost coincide;The results show that the reliability of the simulation results is greatly affected by the distance between the explosion centers;(3)Based on the multi-material fluid structure coupling algorithm,the full coupling model of underwater explosion of wharf frame structure is constructed,and the dynamic response and damage of wharf structure are discussed.When the shock wave propagates to the structure water air interface,the structure will be damaged by punching because of the water cut-off effect;when the shock wave propagates to the structure interior,the shock wave in the structure will form the tensile wave which is opposite to the propagation direction,in this case,it is easy to cause the tensile failure of the concrete structure;(4)Under the action of underwater explosion load,except for the damage of all piles in different degrees,the plastic damage of the bedrock area at the bottom of the first pile at the end of the wharf and the bedrock area connected with the crown beam is relatively serious.The underwater pile foundation here should be properly reinforced in the anti explosion design of the wharf;(5)when the relative explosion distance is 0.252(m/kg3)and the relative explosion depth is 0.693(m/kg3),the peak pressure of underwater explosion load on the wharf structure is relatively large.This special situation should be considered in the anti explosion protection design of the wharf structure.