落石冲击拦石墙的动力响应模拟研究

Simulation Study on Dynamic Response of Rock Retaining Wall under Rockfall Impact

为深入研究落石冲击作用下拦石墙的动力响应特征,以达到提高拦石墙结构设计安全性的目的,基于ANSYS/LS-DYNA有限元软件,建立了相应的有限元模型。首先结合已有的模型试验以及常见的冲击力计算公式验证了有限元模型的可靠性,然后重点分析了落石质量、落石冲击速度、落石冲击角度、落石形状等4个因素对落石冲击拦石墙结构动力响应的影响规律。动力响应评价从冲击力、冲击变形、拦石墙Mises等效应力3方面进行。结果表明:冲击力、冲击变形、拦石墙Mises等效应力与落石质量、落石冲击速度呈正相关;法向冲击力、冲击变形与落石冲击角度呈正相关,且冲击角度为90°时,法向冲击力达到最大;切向冲击力随落石冲击角度的增加呈先增大后减小的趋势,切向冲击变形与落石冲击角度呈负相关;拦石墙Mises等效应力与落石冲击角度呈正相关;落石形状对动力响应影响较大,长方体落石产生的冲击力、拦石墙Mises等效应力分别为球体落石的4~7,4~6倍,冲击变形为球体落石的1/4~1/3;长方体落石与缓冲层接触面积越大,冲击力、拦石墙Mises等效应力越大,冲击变形越小。针对具体的拦石墙工程问题,应正确认识落石冲击作用下拦石墙的动力响应规律,才能采取有效的措施,减少不必要的损失。

In order to deeply study the dynamic response characteristics of rock retaining wall under rockfall impact and improve the structural design safety of rock retaining wall, the corresponding finite element model is established based on ANSYS/LS-DYNA finite element software. First, the reliability of the established finite element model is verified by combining the existing model experiments and common impact force calculation formulas. Then, the influencing rules of the 4 factors(rockfall mass, rockfall impact velocity, rockfall impact angle and rockfall shape) on the dynamic response of rockfall impacting rock retaining wall structure are especially analyzed. The dynamic response evaluation includes impact force, impact deformation and Mises equivalent stress of rock retaining wall. The result shows that(1) impact force, impact deformation and Mises equivalent stress of rock retaining wall are positively correlated with rockfall mass and impact velocity;(2) normal impact force and impact deformation are positively correlated with rockfall impact angle, and the normal impact force reaches the maximum when the impact angle is 90°;(3) tangential impact force increases at first and then decreases with the increase of rockfall impact angle, and tangential impact deformation is negatively correlated with rockfall impact angle;(4)the Mises equivalent stress of rock retaining wall is positively correlated with rockfall impact angle;(5)the shape of rockfall has great influence on the dynamic response, the impact force and Mises equivalent stress generated by the cuboid rockfall on rock retaining wall are 4-7 and 4-6 times as large as that generated by the spherical rockfall, and the impact deformation is 1/4-1/3 of that generated by the spherical rockfall;(6) the larger the contact area between cuboid rockfall and cushion, the larger the impact force and Mises equivalent stress of rockfall retaining wall, and the smaller the impact deformation;(7) in view of the specific problems of rock retaining wall project, the dynamic response rule of rock retaining wall under rockfall impact should be correctly understood, so that effective measures can be adopted to reduce unnecessary losses.