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EXPERIMENTAL STUDY ON MECHANISM OF SHALLOW LOESS LANDSLIDES INDUCED BY RAINFALL
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摘要: 黄土较松散，内部大孔隙和垂直节理发育，因其特殊的结构为雨水的快速入渗提供了通道。降雨型黄土浅层滑坡已造成了大量的经济损失与人员伤亡。为了有效减轻降雨诱发黄土滑坡对社会和经济的影响，开展降雨型滑坡室内实验研究，具有重大的现实意义。本文旨在研究不同降雨形式和不同坡体结构对黄土斜坡变形破坏过程影响，设计并进行了3组室内物理模型实验，分别为持续强降雨斜坡实验、持续强降雨斜坡（带垂直节理）实验和间歇性强降雨斜坡实验，且每组斜坡内埋设体积含水率传感器、基质吸力传感器和孔隙水压力传感器3种传感器记录其内部变化。通过对每一个黄土斜坡体内传感器的读数变化及实验现象进行分析，同时对不同实验条件下实验过程及结果进行对比，进而得出降雨条件下浅表层黄土滑坡的变形破坏规律，总结出该类滑坡的破坏模式及其诱发机理。实验前期，随着体积含水率不断增大，基质吸力逐渐减小至基本稳定，土体强度随之减小，实验后期上部土体饱和，斜坡产生的变形和土体排水不畅产生了超孔隙水压力，有效应力随之减小，土体强度减小至最小，导致滑坡产生。同时，坡体结构对斜坡稳定性的影响大于降雨形式的影响。Abstract: The loess is loose, and contains numerous large pores and vertical joints inside, which provides channels for the rapid infiltration of rainfall. The shallow loess landslides have caused significant casualties and economic losses. In order to effectively reduce the social and economic impact of landslides induced by rainfall, it is of great realistic significance to carry out the laboratory experimental study on rainfall-induced landslides. The purpose of this paper is to study the effects of different rainfall pattern and different slope structure on the deformation and failure process of loess slope. Three groups of indoor physical model experiments are designed and conducted. They include loess slope with continuous heavy rainfall, loess slope containing a vertical joint with continuous heavy rainfall, and loess slope with intermittent heavy rainfall. Three kinds of sensors including volume moisture sensors, matric suction sensors and pore water pressure sensors are buried to record the internal changes in each loess slope. Analyzing the changing readings of sensors and experimental phenomenon, and comparing the experimental procedures and results under the different experimental conditions disclose the deformation and failure law of shallow loess landslide under rainfall condition. The failure mode and triggering mechanism of this kind of landslides are summarized. The experimental results show that, in the early stage of the experiments, the matric suction of the loess decreased gradually and maintained stable in the end, therefore the strength reduced, with the continuous increases of volume moisture. In the later stage, the upper loess of the slope reached the saturation stage, excess pore water pressure generated by the slope deformation and poor drainage of the loess decreased the effective stress and the strength of the loess, and as a result, the strength reached the minimum, which resulted in landslides. And meanwhile, the influence of slope structure on slope stability is greater than that of rainfall pattern.
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Key words:
- Loess slope /
- Rainfall /
- Landslide /
- Physical model experiment /
- Pore water pressure
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图 5 实验所用仪器
a.降雨喷头；b. EC-5体积含水率传感器；c. MPS-6基质吸力传感器；d. EM50数据采集仪；e. HC-25孔隙水压力传感器；f.数据采集仪
Figure 5. Instruments used in experiments
图 7 均质斜坡实验剖面图
Figure 7. Section of homogeneous slope of continuous heavy rainfall experiment
图 9 持续强降雨含垂直节理斜坡实验剖面图
Figure 9. Section of slope contained a vertical joint of continuous heavy rainfall experiment
图 10 持续性强降雨均质斜坡实验过程
a.初始状态；b.坡肩和坡脚侵蚀；c.局部破坏；d.整体破坏
Figure 10. Process of homogeneous slope continuous heavy rainfall experiment
图 11 体积含水率传感器的读数变化
a. 2、5、6、7号体积含水率传感器读数变化；b. 1、3、4号体积含水率传感器读数变化
Figure 11. Reading changes in volume moisture sensors
图 12 基质吸力传感器的读数变化
a. 2、5、6、7号基质吸力传感器读数变化；b. 1、3、4号基质吸力传感器变化
Figure 12. Reading changes in matric suction sensors
图 13 孔隙水压力传感器的读数变化
a. 2、5、6、7号孔隙水压力传感器变化；b. 1、3、4号孔隙水压力传感器变化
Figure 13. Reading changes in pore water pressure sensors
图 14 持续性强降雨含垂直节理斜坡实验过程
a.初始状态；b.湿润锋和坡肩、坡脚侵蚀；c.局部破坏；d.整体破坏
Figure 14. Process of slope contained a vertical joint of continuous heavy rainfall experiment
图 15 体积含水率传感器的读数变化
a. 2、5、7号体积含水率传感器读数变化；b. 1、3、4号体积含水率传感器读数变化
Figure 15. Reading changes in volume moisture sensors
图 16 基质吸力传感器的读数变化
a. 2、5、7号基质吸力传感器读数变化；b. 1、3、4号基质吸力传感器变化
Figure 16. Reading changes in matric suction sensors
图 17 孔隙水压力传感器的读数变化
a. 2、5、7号孔隙水压力传感器变化；b. 1、3、4号孔隙水压力传感器变化
Figure 17. Reading changes in pore water pressure sensors
图 18 体积含水率传感器的读数变化
a. 2、5、6、7号体积含水率传感器读数变化；b. 1、3、4号体积含水率传感器读数变化
Figure 18. Reading changes in volume moisture sensors
图 19 基质吸力传感器的读数变化
a. 2、5、6、7号基质吸力传感器读数变化；b. 1、3、4号基质吸力传感器变化
Figure 19. Reading changes in matric suction sensors
图 20 孔隙水压力传感器的读数变化
a. 2、5、6、7号孔隙水压力传感器变化；b. 1、3、4号孔隙水压力传感器变化
Figure 20. Reading changes in pore water pressure sensors
图 21 持续强降雨均质斜坡破坏模式
a.原始斜坡；b.坡肩侵蚀；c.坡脚侵蚀；d.后缘裂隙形成与贯通；e.滑动破坏
Figure 21. Failure mode of homogeneous slope induced by continuous heavy rainfall
图 22 持续强降雨含垂直节理斜坡破坏模式
a.原始斜坡；b.坡肩侵蚀；c.坡脚侵蚀；d.后缘节理扩展；e.滑动破坏
Figure 22. Failure mode of slope contained a vertical joint induced by continuous heavy rainfall
表 1 黄土的物理参数
Table 1. Physical parameters of the loess
干重度
/kN·m-3天然
重度
/kN·m-3饱和
重度
/kN·m-3初始体积
含水率
/%饱和体积
含水率
/%竖向
渗透系数
/m·s-113.2 14.7 23.2 10 43 2.23×10-6 
下载: 导出CSV
表 2 降雨实验方案
Table 2. Scheme of rainfall test
实验
类型降雨强度
/mm·h-1降雨
时间降雨
类型斜坡
类型持续强降雨 70 直至斜坡破坏 均匀型 均质斜坡 间歇性
强降雨70 每间隔24h
降雨1h，直至破坏间歇型 均质斜坡 持续强降雨 70 直至斜坡破坏 均匀型 带垂直
节理斜坡
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表 3 降雨滑坡发展过程和滑动时间
Table 3. Development and sliding time of rainfall-induced landslides
实验类型 斜坡特征 现象描述 累计降雨量/mm 滑动时间/min 强降雨 均质坡 ① 前缘坡脚侵蚀。② 后缘轻微沉降，距离坡肩约5cm处产生裂隙。③ 破坏较快，滑动距离近，滑面最浅。 373.3 320 强降雨 含垂直
节理斜坡① 坡脚冲蚀严重，形成临空面。② 裂隙处充满水，有轻微塌陷，裂隙向下扩展，湿润锋在裂隙处呈弧形。③ 破坏最快，滑动距离最小，滑动面最深。 318.5 273 间歇性
强降雨均质坡 ① 坡肩侵蚀，坡脚垮塌。② 降雨后一天内后缘产生许多微小裂隙，距离坡肩9cm，降雨时雨水侵入。③ 所需时间最长，滑动距离短。 415.3 7263
(5天1小时3分)
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