碎屑流高风险区桩群防护结构优化布局研究

桩群是一种可有效耗散碎屑流运动能量，抑制碎屑流运动距离及速度的山地灾害防护结构。在碎屑流沟口与受灾体之间构建一组桩群减速带，可达到保护受灾体的目的。以物理模型试验为基础，开展弧型桩群、方型桩群和圆型桩群的沟槽型碎屑流冲击动力响应研究。讨论了3种不同类型的桩群对沟槽型碎屑流运动形态的影响，进一步开展弧型桩群的结构优化研究。结果表明：采用桩群结构可有效减小沟槽型碎屑流堆积距离并抑制其运动速度；3种不同形状桩群之间，弧型桩与方型桩的拦挡效果明显优于圆型桩；弧型桩由于凹槽式外型，对沟槽型碎屑流堆积面积、淤埋深度的抑制效果稍优于方型桩；在相同高度、直径等几何参数下，弧型桩体积比圆型桩小22.6%，比方型桩小39.2%，因此弧型桩的制作成本也相对较低；弧型桩排数从1排增加到3排，桩群拦挡率分别提升7.2%、4.5%；适量增加槽口与桩之间距离Ld可以有效提高弧型桩群防护结构的能量耗散效率。该研究可为桩群在沟槽型碎屑流防治工程中的应用提供理论及技术支持。

Optimal layout of a new type of baffle based on high-risk areas of rock avalanches

The baffle, as a kind of mountain disaster protection structure, can effectively dissipate the movement energy of rock avalanches and restrain the movement distance and speed of rock avalanches. The construction of a baffle’s speed bumps between the rock avalanches gully and the disaster zone can greatly protect the disaster zone. In this study, based on the physical model experiment, the dynamic impact response of the channelled rock avalanches is implemented on the arc-shaped, square and cylindrical baffles. The effects of three types of baffles on the motion performance of channelled rock avalanches are discussed, and the structural optimisation of the arc-shaped baffles is further investigated. The results show that the baffles can effectively reduce the channelled rock avalanches accumulation distance and control the movement speed. Among the baffles of these three shapes, the blocking effect of the arc-shaped baffles and the square baffles is more efficient than that of the cylindrical baffles. Owing to the concave shape of the arc-shaped baffles, the blocking effect is much better than that of square baffles on the deposit areas and deposit depth. At the same height and diameter, the arc-shaped baffle volume has 22.6% and 39.2% less than the cylindrical baffle and the square baffle, respectively. Thus, the production cost of the arc-shaped baffle is lower than another two baffles. When the row of the arc-shaped baffles is increased from one to three, its blocking rate is increased from 7.2% to 4.5% as well. An appropriate increase in Ld can improve the energy dissipation efficiency of the arc-shaped baffles. This can provide theoretical and technical support for the application of pile groups in channelled rock avalanches control engineering.