落石冲击混凝土棚洞力学特性研究

落石冲击棚洞结构作用过程复杂，缺乏统一的落石冲击力表达式。首先，将落石简化为刚性球体，基于Hertz接触理论，推导得到落石冲击力半正弦算法的理论表达式，考虑落石冲击下棚洞的非弹性特征，根据落石与材料碰撞过程中落石加速度曲线特征，采用函数拟合法推导得到落石法向冲击下其冲击力的理论计算方法；然后，基于ANSYS/LS-DYNA软件建立落石冲击棚洞数值计算模型，研究不同冲击速度下落石冲击棚洞动力特征；最后，与现存常见的多种方法进行对比，得出以下结论：Hertz半正弦法得到的落石冲击力远大于函数拟合法和数值法，而函数拟合法和数值法得到的落石冲击力时程曲线相接近，表明函数拟合法更能反映落石与棚洞接触碰撞动力关系；对比其他计算方法可以得到，Hertz算法适用于分析无能量损失下的弹性碰撞问题，而Logistic算法适用于材料大塑性变形的情况，弹塑性接触理论结果和动力有限元结果存在差异，而采用函数拟合推导的计算方法得到的落石最大冲击力和落石冲击作用时间与动力有限元法更接近，更能反映落石冲击棚洞动力响应特征，推导的落石冲击力计算方法可为工程实践中棚洞防护设计提供理论参考。

Investiagtions on mechanical characteristics of rockfall impact on concrete shed cave

The impact of rockfall on the shed cave structure is complicated and lacks a unified expression of rockfall impact force. First of all, the falling rock is simplified into a rigid sphere, the theoretical expression of the rockfall impact force is derived using half-sine algorithm based on the Hertz contact theory. Considering the inelastic characteristics of rockfall impact on shed cave, the method of function fitting is used to calculate the impact force of rockfall under normal impact according to the characteristics of the rockfall acceleration curve during the collision between the rock and the material, and then a numerical calculation model of the rockfall impact on shed cave is established to study the dynamic characteristics of the rockfall impact on shed cave at different impact speeds based on ANSYS/LS-DYNA software. Finally, compared with the existing common methods, some conclusions are drawn. The impact force of rockfall obtained by Hertz half sine method is much larger than that obtained by function fitting method and numerical method, and the time-history relationship of rockfall impact force obtained by function fitting method in this paper is close to that obtained by numerical method. It indicats that function fitting method can better reflect the dynamic relationship of the collision between the falling rock and the shed cave. Compared with other calculation methods, it can be obtained that the Hertz algorithm is suitable for analyzing the elastic collision problem without energy loss, and the Logistic algorithm is suitable for the situation of large plastic deformation of the material. There are differences between the elastoplastic contact theory results and the dynamic finite element results, and the maximum impact force and the impact time of the rockfall obtained by the calculation method derived from the function fitting are closer to the dynamic finite element method, and it can better reflect the dynamic response characteristics of the rockfall impact on the shed. The calculation method of rockfall impact force deduced in this paper can provide theoretical reference for the design of protection measures in practical engineering.