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MODEL EXPERIMENT STUDY ON EROSION OF LOESS SLOPE DUE TO RAINFALL
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摘要: 针对边坡表层受降雨冲刷易引发水土流失并导致滑坡灾害的难题, 以黄土边坡为例, 提出了一种基于减排水理念的生态固坡综合防护方法。采用自主研制的边坡降雨模拟实验装置, 考虑不同改良剂掺量、格构防护形式、雨强、历时、坡比等因素对防护效果的影响, 研究不同因素组合影响下的边坡土体侵蚀规律与演化机理。试验结果表明, 黄土边坡坡面侵蚀可归纳为溅蚀、片蚀、沟蚀、坍塌、滑坡的过程; 随改良剂掺量增加, 改良边坡抗侵蚀能力增强, 综合考虑提出改良剂的最优掺量为3‰; 与素土边坡相比, 3‰改良剂改良边坡受雨强的影响较小; 随降雨历时增加, 改良剂改良效果越明显; 改良剂、框格梁以及两者的综合利用, 均能有效提高边坡抗雨水冲刷与侵蚀能力; 边坡坡度增大至一定程度, 坡体受降雨侵蚀易突然发生整体滑塌, 需进行重点关注; 改良剂主要通过絮凝作用使土颗粒之间镶嵌黏结更紧密, 从而提高黄土的持水性和抗蚀性。Abstract: Slope surface erosion due to rainfall is liable to cause soil erosion and landslide hazard, which is a difficult problem.This paper takes a loess slope as an example and puts forward a comprehensive protection method of ecological slope based on the concept of water reducing and drainage.In order to study on soil erosion law and evolution mechanism of slope under different factors, the simulation experiments were carried out with the self-developed slope rainfall simulator.It considers modifier content, lattice protective form, intensity, duration, aspect ratio on the effect of protection.Test results show that the loess slope surface erosion can be summarized as splash erosion, sheet erosion, gully erosion and landslides.With the increase of the modifier content, the corrosion resistance of the improved slope is enhanced, and the optimal dosage of the modifier is 3‰.Compared with the plain loess slope, rainfall intensity has little influence on improved slope with 3‰modifier.With the increase of rainfall duration, the improvement effect of the modifier is more obvious.Modifier and frame as well as their comprehensive utilization can effectively improve the slope resistance to rainfall erosion.When the slope gradient increases to a certain extent, the slope is prone to collapse suddenly due to the rainfall erosion, which needs to be emphasized.The modifier mainly makes the soil particles more compacted by flocculation, so as to improve the water holding capacity and corrosion resistance of loess.
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Key words:
- Loess /
- Landslide /
- Slope rainfall simulator /
- Modifier /
- Ecological slope /
- Gridiron /
- Microscopic mechanism
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图 1 边坡降雨冲刷模拟装置
①.流量表; ②.降雨雾化喷头; ③.降雨架; ④.模型槽; ⑤.导水槽; ⑥.集水桶
Figure 1. The simulation device for slope rainfall erosion
图 2 降雨条件下坡面侵蚀的演变过程
a.5 min; b.10 min; c.15 min; d.25 min; e.35 min; f.45 min
Figure 2. Evolution process of slope surface rainfall erosion
图 4 45 min后各边坡冲刷情况
a.素土; b.1‰PMP; c.2‰PMP; d.3‰PMP; e.4‰PMP; f.6‰PMP
Figure 4. The slope erosion situation after 45 min
图 5 不同工况下的黄土侵蚀累积量
Figure 5. Cumulative quantity of loess erosion under different working conditions
图 6 降雨45 min后各工况边坡侵蚀现象对比图
a.工况1;b.工况2;c.工况4;d.工况7;e.工况8;f.工况9
Figure 6. The slope erosion phenomenon after 45 min
图 8 25 min后不同雨强下的素土坡体
a.70 mm h-1; b.100 mm h-1; c.140 mm h-1
Figure 8. Soil slope under different rainfall intensity after 25 min
图 9 降雨15 min累积冲刷量随坡比的变化
Figure 9. Change of cumulative erosion with slope ratio after 15 min
图 11 素黄土SEM图像
a.×100;b.×500;c.×1000;d.×2000;e.×5000;f.×10000
Figure 11. The SEM images of loess
图 12 改良黄土SEM图像
×100;b.×500;c.×1000;d.×2000;e.×5000;f.×10000
Figure 12. The SEM of modified loess
表 1 试验用土参数
Table 1. Parameters of experimental soil
土的类型 改良剂掺量/‰ 密度/g·cm-3 含水率/% 塑限ωp/% 液限ωL/% 抗剪强度参数 崩解性 湿陷性 c /kPa φ /(°) 原状土 — 1.60 13.5 14.5 31.6 55.0 30.3 有 有 改良重塑土 0 1.60 13.5 14.5 31.6 4.7 22.8 有 有 1 1.60 13.5 15.2 32.3 7.0 24.3 无 无 2 1.60 13.5 14.5 34.6 13.2 23.2 无 无 3 1.60 13.5 14.5 37.4 15.1 24.7 无 无 4 1.60 13.5 14.7 39.9 18.6 24.2 无 无 6 1.61 13.5 13.2 42.3 22.4 26.0 无 无 
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表 2 不同工况表
Table 2. Different working table
工况编号 素土 改良剂改良土 框格梁 坡比 雨强/mm·h-1 1 √ — — 1︰1 70 2 — 1‰ — 1︰1 70 3 — 2‰ — 1︰1 70 4 — 3‰ — 1︰1 70 5 — 4‰ — 1︰1 70 6 — 6‰ — 1︰1 70 7 √ — √ 1︰1 70 8 — 1‰ √ 1︰1 70 9 — 3‰ √ 1︰1 70 10 √ — — 1︰1 100 11 — 3‰ — 1︰1 100 12 √ — — 1︰1 140 13 — 3‰ — 1︰1 140 14 √ — — 1︰0.75 70 15 — 3‰ — 1︰0.75 70 16 √ — — 1︰1.25 70 17 — 3‰ — 1︰1.25 70
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表 3 冲刷速度降低率
Table 3. Reduction rate of scour velocity
改良剂掺量/‰ 冲刷速度降低率α/% 5min 10min 15min 25min 35min 45min 1 32.4 7.1 53.7 72.9 76.6 77.1 2 45.4 59.2 82.9 93.8 94.9 94.7 3 83.4 83.2 91.3 96.2 96.7 95 4 52.1 62.9 85.6 95 95.4 94.8 6 52.5 70.6 89.4 96.5 97.2 97.4
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表 4 各工况下的累积冲刷量降低率
Table 4. Reduction rate of cumulative erosion under various operating conditions
工况情况 素土加格构梁 1‰改良土 3‰改良土 1‰改良土加格构梁 3‰改良土加格构梁 β/%(25min) 60 77 96 92 97 β/%(45min) 63 77 94 91 96
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