Experimental study on the effect of rainfall patterns on the failure mode of debris flows after earthquakes: A case study of Tiantanggou, Jiuzhai
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摘要:
降雨过程中降雨强度的变化会影响土体渗透率及饱和过程, 从而改变土体的力学性质, 影响泥石流起动模式及破坏规模。为探究不同降雨模式对震后泥石流起动机制的影响, 自制了小比例模型槽, 结合可控雨型的降雨模拟系统, 进行了人工降雨诱发泥石流的室内模型试验; 基于不同降雨模式下泥石流的起动过程分析, 对坡体内部含水率和孔隙水压力的变化规律进行了研究。研究结果表明: 递增型降雨模式下泥石流发生突然, 呈整体滑坡转化为泥石流起动模式, 坡体破坏规模最大; 递减型降雨模式下表现为后退式溃散失稳起动模式; 均匀型降雨模式下则表现为溯源侵蚀起动模式; 中峰型降雨模式下以局部滑坡转化为泥石流起动模式; Ⅴ型降雨模式下则由坡面侵蚀加剧转化为泥石流启动模式, 破坏规模最小。研究结果可以为九寨沟地区泥石流的预报预警提供参考。
Abstract:Variable rainfall intensity can influence soil permeability and saturation processes, change the mechanical properties of soil, and affect the initiation mode and damage scale of debris flows. To explore the response mechanism of debris flows under different rainfall modes after earthquakes, laboratory tests of artificial rainfall-induced debris flows was performed through a small-scale model trough and rainfall simulation system. Based on the starting process of debris flow under different rainfall patterns, the variation of water content and pore water pressure in the slope was studied. The results show that the landslide transforms to a debris flow under the increasing rainfall model, and the damage scale of the accumulation is the largest; the debris flow under the decreasing rainfall occurs after the backward breaking instability; the initiation of debris flow under uniform rainfall mode results from traceable erosion; local landslides are transformed into debris flows under the middle-peak rainfall pattern; under the Ⅴ-shaped rainfall pattern, the slope erosion is intensified and transformed into debris flow, with the smallest damage scale.The research results can provide reference for the forecast and warning of debris flow in Jiuzhaigou area.
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Key words:
- rainfall pattern /
- debris flow /
- physical model experimentation /
- water content
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图 4 各降雨类型的降雨强度随时间的变化
Figure 4. Variation of rainfall intensity of different rainfall patterns with time
图 6 各降雨模式下含水率变化曲线(1#~8#为含水率传感器编号)
Figure 6. Variation curves of water content for different rainfall patterns
图 7 递减型降雨模式下孔隙水压力变化曲线(1P~8P为孔隙水压力传感器编号)
Figure 7. Variation curves of pore water pressure for decreasing rainfall pattern
表 1 各降雨模式下坡体破坏过程汇总
Table 1. Summary of slope body failure process under different rainfall patterns
试验编号 1 2 3 4 5 降雨类型 递增型 递减型 均匀型 中峰型 V型 泥石流起动时间/min 16 9 22 25 35 最大侵蚀速率/(kg·min-1) 12.86 10.55 3.87 4.92 2.16 累计侵蚀量/kg 80.95 61.03 63.95 41.9 19.97 
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