| 其他摘要 | Rill erosion is the process of soil particles separating in the groove and handling by rill flow, and it is one type of
surface corrosion, and the rill formed can be completely filled by normal farming activities. In the loess plateau region, rill
erosion of slope accounts for more than 70% of the total erosion, and rill erosion is a major erosion in the loess plateau hilly
land, and is also an important part of mechanism of slope erosion prediction. Rills are small channels which function as both
sediment sources and sediment transport vehicles on hill slopes. It is a quantum leap during the process of soil erosion on
slopes, and is also the beginning of qualitative changes in the process of soil erosion. The rill morphology development plays
an important role in the understanding of rill erosion. Rill morphology changes have many influence factors in the process of
rill erosion, so systematically studying the relationship between rill shape coefficient and influencing factors can make us
better understand the process of rill erosion and erosion mechanism. For the study of rill morphological development process,
the combination scouring tests of 6 slopes (2°, 4°, 6°, 8°, 10°, and 12°) and 5 discharges (8, 16, 24, 32, and 40 L/min) were
carried out, and the effect mechanism of rill transverse profile morphological development on the loess slope surface was
investigated, as well as the dynamic characteristics of the impact. The results showed that rill width-depth ratio ranged from
3.006 to 4.841, and according to the hydraulic optimum section, the rill flow was far from steady state. In rill erosion,
downward erosion and lateral erosion gradually transited to downward erosion. Because of incised and lateral erosion, rill
cross-sectional shape was gradually widened and deepened with the increase of slope and time. Along with the change of slope,
cross-sectional shape coefficient varied within the range of 0.36-0.522. Research showed that: The rill cross-sectional shape
was approximating to the trapezoidal hydraulic best section with the increase of the flow, slope and scour lasted time, namely
the section with the least resistance. With the increase of water flow length, cross section shape changed gradually from wide
and deep to narrow, and the cross-sectional shape coefficient was reduced. Through calculation, the groove profile form ranged
within 0.6-11.26, and increased with the increase of slope, but had no significant correlation with discharge. With the increase
of slope, the average spacing of drop pit on bed face decreased, the depth of drop pit increased, and the groove profile shape
coefficient increased. Comprehensive resistance coefficient and energy dissipation showed a good power function relationship
with groove profile shape coefficient, and with the increase of profile shape coefficient, the slope shape resistance increased.
Rill hydraulic characteristics and groove shape showed the role of mutual connection and restriction and reaction system.
Groove profile shape coefficient was larger, the bed surface shape resistance increased, and drop pit also would be developed
more maturely. The water in drop pit had strong turbulence and aeration, which had significant effect on energy dissipation. |
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