混凝土大坝在水下爆炸作用下的动力响应分析

Dynamic Response Analysis of Concrete Dam under the Action of Underwater Explosion

为了研究混凝土大坝在水下爆炸冲击荷载作用下的应力分布和动力响应,利用ANSYS/LS-DYNA软件建立大坝结构爆炸数值分析模型,包括炸药、水介质、空气介质、坝体混凝土、岩石五个部分。选取底宽60 m、高85 m的大坝作为研究对象,考虑爆炸荷载作用下混凝土大变形和高应变的影响,采用HJC(Holmquist-Johnson-Cook)本构模型模拟坝体混凝土的损伤破坏和塑性变形,研究了不考虑重力和考虑重力的两种模型条件下可能的破坏模式和破坏机理。数值模拟得到爆炸后大坝的应力分布,进而选取4个典型位置点研究其位移时程和压强时程。研究表明:爆炸初始产生的缺口是冲击波扩散的起点,冲击波会发生多次反射,爆炸初始时最大应力可超过50 MPa,之后在10~30 MPa之间震荡。各个典型位置均在第1次反射时达到最大峰值压力,可将第1个反射压力作为弧面板的爆炸冲击荷载;最大von Mises应力出现在爆源附近的缺口以及坝坡转角等易发生应力集中处;典型位置的位移与距离炸药位置呈负相关;重力产生的位移和压力对爆炸响应起抵抗作用,但最大von Mises应力无显著区别。

In order to study the stress distribution and dynamic response of concrete dams under underwater explosion impact load,the numerical analysis model of dam structure explosion was established by using ANSYS/LS-DYNA software,including explosive,water medium,air medium,dam concrete and rock.The dam with a bottom width of 60 m and a height of 85 m was selected as the research object.Considering the influence of large deformation and high strain of concrete under explosion load,HJC(Holmquist Johnson cook)constitutive model was used to simulate the damage,failure and plastic deformation of the dam concrete.The possible failure modes and mechanisms under the conditions of two models with and without considering gravity were studied.The stress distribution of the dam after explosion was obtained by numerical simulation,and then four typical locations were selected to study its displacement-time history and pressure-time history.The research shows that the notch generated at the initial explosion is the starting point of shock wave diffusion,and the shock wave will be reflected by multiple times.The maximum stress at the initial explosion can exceed 50 MPa,and then vibrates between 10~30 MPa.The maximum peak pressures appear at the first reflection for all the typical positions,and the first reflection pressure can be used as the explosion impact load of the arc panel.The maximum von Mises stresses occur at the notches near the explosion source and the dam slope corners,which are prone to stress concentration.The displacements of the typical positions are negatively correlated with the distances from the explosive position.The displacements and pressures caused by gravity can resist the explosion responses,but there is no significant difference in the maximum von Mises stress.