滑坡碎屑流消能桩结构动力计算与设计方法

Computation and design methods of energy dissipating pile against landslide debris flow

滑坡碎屑流由于体积大、速度快和运动距离远的特性,常常在下游造成较大破坏形成严重的自然灾害。基于消能桩与滑坡碎屑流结构的动力相互作用过程,采用功能原理和结构力学方法,推导了消能桩对滑坡碎屑流能量耗散的理论计算模型。首先,通过冲击力计算模型获得滑坡碎屑流冲击力的垂向分布;其次,由悬臂梁挠曲变形的关系确定其抗弯反力;然后,根据滑坡碎屑流在坡面上流动的面积、厚度估算消能桩的反力,以及在反力方向上碎屑流通过的距离;最后,计算单根桩的动能耗散量。采用推导的公式进行消能桩的优化设计:综合考虑下游防护对象的位置和滑坡体的堆积位置,计算消能桩的“消能效益”,确定消能桩的数量;根据最大块石的冲击力作用,计算需要消能桩的排数,从而确定消能桩的排布设计。选取一个滑坡碎屑流实例,采用上述理论计算模型设计消能桩,计算出消能桩的数量和排数,并根据计算结果进行优化布设。结果表明,该模型适用于消能桩的优化设计与应用。

Landslide debris flow usually causes serious natural disasters in lower regions because of their enormous volume,rapid velocity and long-runout distance.Based on the dynamic interaction between energy dissipation piles and landslide debris flow,the theoretical calculation model of energy dissipation by piles is deduced by utilizing the power principal and structural mechanics method.Firstly,the vertical distribution of the impact force of landslide debris flow is obtained by calculation.Secondly,the bending force is determined according to the relation of the bending deformation of cantilever beam.Then,the spreading area and thickness of the granular flow on slope surface are used to estimate the distance that the deposits passed over the piles.Finally,the kinetic energy dissipation of every pile is computed.The optimized design of the energy dissipating pile is carried out through the derived formulas:taking into account the position of the objects to be protected and the accumulation area of the landslide.the energy dissipating benefit and the number of piles are calculated.According to the impact force of the maximum stone,the number of rows of piles is calculated to decide the layout design of energy dissipation piles.An idealized landslide is taken as an example to illustrate the use of the proposed theoretical methods.The results show that the method can be used for the optimization design of energy dissipating structures against landslide granular debris flows.