Hydraulic erosion tests on river bank slope units in middle and lower reaches of Yangtze River
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摘要: 水作用下长江中下游岸坡正在面临严峻的崩岸破坏。为探究岸坡土体的水力侵蚀特性，进行单元体单面浸水湿化-崩解试验与侧向冲刷水毁室内试验，通过分析冲刷沟形态、测量单元体质量、探究侧向冲刷深度和高度变化规律，研究根系和格栅植被面层对单元体侵蚀破坏的影响，分析运用乔木根系联合格栅植被面层对岸坡进行防冲的可行性。试验结果表明：湿化-崩解与侧向冲刷二者共同作用，引起和加剧岸坡土体的淘蚀破坏。随着水深、流速及冲刷时间的增加，单元体侧向冲刷深度与冲刷高度一直增加；在本实验较小的单元体尺寸下，较粗的乔木模拟根系对于减小单元体冲蚀破坏程度的作用有限，其根土间隙优先流效应在一定程度上反而增加侧向冲刷深度；根系对黏性土的牵拉锚固作用明显强于粉土质砂，能够延缓上部土体的崩塌；设置格栅植被面层后，可有效减小单元体侧向冲刷深度，抗冲效果显著，研究结果可为生态护岸技术研发和应用提供借鉴。
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关键词:
- 长江中下游河岸 /
- 根土复合体 /
- 格栅植被面层 /
- 湿化-崩解-侧向冲刷 /
- 单元体试验
Abstract: The river banks in the middle and lower reaches of the Yangtze River are facing severe hydraulic erosion. To explore the hydraulic erosion characteristics of bank slope soils, the single face soaking-immersion erosion tests and lateral erosion tests by flowing are conducted. By analyzing the morphology of erosion gullies, measuring the mass of single units, investigating the lateral depth and height loss by flowing erosion and studying the influences of roots and grid-vegetation layers on the erosion and destruction of soil units, the feasibility of using tree roots combined with grid-vegetation layers to prevent erosion on the bank slopes is studied. The test results show that both wetting erosion and flowing erosion jointly cause the erosion and destruction of bank slope soils. With the increase of the water depth, flow velocity and erosion time, the lateral depth and height of the lost unit by flowing erosion continuously increase. Under the small unit size of the tests, the effects of simulating roots with coarse tree roots on reducing the erosion and destruction of units are limited. The preferential flow effects of root-soil gaps actually increase the lateral erosion depth to some extent. The anchoring effects of roots on cohesive soil are significantly stronger than those on sandy loam, which can delay the collapse of the upper soil. After setting up the grid-vegetation layer, the lateral erosion depth of the unit can be effectively reduced, and the erosion resistance effects are significant. The research results can provide reference for ecological bank protection. -
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图 2 侧向冲刷侵蚀试验及测点分布示意图
Figure 2. Lateral scouring erosion tests and distribution of measuring points
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图 3 单元体单侧浸水崩解试验质量与崩解率随时间变化规律
Figure 3. Variation of quality and disintegration rate of single-sided immersion disintegration tests of units with time
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图 6 过流宽度8 cm各工况单元体出水口截面轮廓图
Figure 6. Cross-sectional profile of outlet of unit under various cases with flow width of 8 cm
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图 7 过流宽度4 cm各工况单元体出水口截面轮廓图
Figure 7. Cross-sectional profile of outlet of unit under various cases with flow width of 4 cm
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图 9 过流宽度8 cm工况侧向冲刷高度变化规律
Figure 9. Variation in lateral scour height under flow width of 8 cm
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图 10 各工况下单元体冲蚀率随时间变化规律
Figure 10. Variation rule of erosion rate with time of units under various working conditions
表 1 试验土料的粒组含量组成
Table 1 Particle composition contents of test soil materials
土类 砾粒 砂粒 粉粒 黏粒 10~5 mm 5~2 mm 2~0.075 mm 0.075~0.005 mm < 0.005 mm 粉土质砂 1.96% 14.87% 52.92% 20.69% 9.56% 黏土 1.30% 19.71% 12.30% 41.93% 24.76% 
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表 2 单元体侧向冲刷侵蚀试验方案
Table 2 Lateral scouring erosion test programs for units
工况 过流宽度/cm 土体单元处理方式 T1 8 纯土（粉土质砂） T2 纯土+根系 T3 纯土+格栅植被面层 T4 纯土+根系+格栅植被层 T5 4 纯土 T6 纯土+根系 T7 纯土+根系+格栅植被层 T8 4 二元土（双层土） T9 二元土+根系 T10 二元土+根系+格栅植被
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