ISWC OpenIR  > 水保所知识产出(1956---)
扰动堆积土体边坡土壤侵蚀动力过程试验研究
张少佳
Subtype硕士
Thesis Advisor高照良
2014-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Keyword黄土高原 扰动堆积土体 侵蚀产沙 水动力学特性 动力过程
Abstract

随着西部大开发的推进和区域经济建设的需求,黄土高原地区生产、开发类
建设项目越来越多,由此引起的扰动堆积土体所带来的土壤侵蚀问题愈发凸显。
由于遭到剧烈的扰动,松散堆积土体原有土体结构遭到破坏,并且常常缺乏水土
保持工程措施和植物措施的保护,在暴雨条件下极易发生剧烈土壤侵蚀而破坏农
田、道路等,给人民的生命财产带来巨大的损失。为了探明扰动堆积土体的土壤
侵蚀特性随坡度和初始水动力条件的变化,我们建设了标准的试验小区,探讨其
在 3 个坡度、4 个放水流量下土壤侵蚀的特性及其发生的原因和过程。通过整个
试验过程得到以下主要结论:
(1)从小区的土壤侵蚀特性来看:试验条件下的产流速率随时间的变化规
律基本一致,均呈现先增大然后基本稳定的变化特性;平均产流速率与放水流量
呈线性正相关关系;在 30L/min 的放水流量下产流总量与坡度没有明显关系,其
他流量下产流总量随着坡度的增大而增大。小区产沙速率随时间的变化规律在不
同坡度不同放水流量并不完全一致,基本呈现以下 2 种变化规律:①在最大放水
流量下,产沙速率先迅速增大,然后逐渐减小,最后稳定在一定的范围内;②在
其他情况下,产沙速率先增大然后基本稳定。平均产沙速率与放水流量、坡度均
存在线性正相关关系,但 M a -Q 回归方程的显著性水平(Sig.值)要高于 M a -S 回
归方程的显著性水平,说明与坡度相比放水流量对平均产沙速率的影响更大。
(2)径流含沙量随时间的变化规律主要一下有 3 种:①放水流量较小且坡
度较小时,径流含沙量在较长的一段时间内基本稳定,在试验后期(18min)才
逐渐减小;②放水流量较大或坡度较大时,径流含沙量前期(9~12min 以前)
逐渐减小之后基本稳定;③介于前两种情况之间的径流含沙量随时间不断减小。
平均径流含沙量与放水流量呈线性负相关关系,与坡度则呈线性正相关关系。试
验条件下产流产沙关系基本可以用幂函数 y=ax b 来表达,a 值在 0.388~1.445 之
间变化,b 值在 0.256~0.911 之间变化;随着放水流量和坡度的增大 a 值在不断
增大,而 b 值在不断减小;当放水流量为 60L/min 时,虽然产流产沙之间仍呈现
正相关关系,但幂函数已经不能很好地拟合两者之间的关系。(3)各个放水流量下,在小区中部(断面 3 上下)都存在一个流速大小稳
定在 0.3~0.5m/s 的断面。处在该断面以上的断面,平均流速随放水时间整体呈
现减小趋势;处在该断面以下的断面,平均流速随放水时间整体呈现增大趋势。
各观测断面的平均水深均随着放水时间的延长不断增加;在小区的上部(断面
1~2)平均水深变化剧烈,而在小区中下部(断面 3~5)平均水深变化较为舒
缓并一直处在 0.5mm~1mm 之间;平均水深与放水流量无较为明显的关系。
(4)试验条件下坡面流基本为层流,只有在断面 1 和部分时段为过渡流;
除了个别现象外,坡面流均属急流范畴;各个放水流量下弗汝德数与雷诺数均为
负相关关系;阻力系数与雷诺数存在幂函数关系,但与放水流量关系不明显。分
析阻力系数沿坡长的变化情况发现,0~6m 的坡长范围内土壤侵蚀强烈,是坡面
流中泥沙的主要供给部位;6~20m 坡长范围内土壤侵蚀微弱,该区域对坡面流
中的泥沙仍有供给,但供给速率缓慢。坡面阻力系数与水深呈线性正相关关系,
因此变化特性与水深基本一致。
(5)水流切应力随坡长的变化可以很好地解释小区土壤侵蚀的主要发生部
位在小区中上部(0~10m)的原因。水流切应力虽然与单位面积土壤侵蚀速率
存在较好的线性关系,但由于水流剪切力只代表了水流剥蚀土壤颗粒进入坡面流
的能力,且本试验选取的坡度属于陡坡范畴,重力侵蚀作用表现强烈,该侵蚀模
型已经不适合来解释本试验条件下侵蚀速率的变化。由于水流功率是反映了坡面
流搬运能力,所以水流功率模型能运用于本试验条件下来反应土壤侵蚀速率的变
化。
关键词 :黄土高原;扰动堆积土体;侵蚀产沙;水动力学特性;动力过程

Other Abstract

With the demand for western development and promoting regional economic
development, the Loess Plateau production, development construction projects, more
and more disturbed soil erosion resulting accumulation of soil brought increasingly
prominent. Since being violent disturbances, loosely packed soil of the original soil
structure is destroyed, and often lack the protection of soil and water conservation
measures and plant measures under storm conditions are prone to severe soil erosion
and destruction of farmland, roads, etc. a huge loss to life and property of the people.
In order to investigate the disturbance of soil erosion characteristics change with the
accumulation of soil slope and initial hydrodynamic conditions, we have built a
standard test cell, to explore the reasons for its three slope, drainage flow
characteristics of the next four and occurrence of soil erosion and processes. Through
the entire testing process the following conclusions:
(1) From the point of view of soil erosion characteristics of the cell: the
production flow rate variation under the test conditions consistent over time, showed
steady increases first and then change the basic characteristics; average production
flow rate and drainage flow positive linear correlation relationship; at 30L/min flow
rate of the total runoff and drainage slope no obvious relationship with the slope of
the total runoff increases other traffic. Cell sediment rate variation with time different
in different slope drainage flows are not entirely consistent, basically showing
variation of the following two kinds: ① at maximum drainage flow, sediment
production rate increases rapidly at first, then gradually decreases, and finally
stable within a certain range; ② in other cases, sediment production rate increases first and then basically stable. The average sediment flow rate and drainage, slope
linear relationship existed, but the significance level (Sig. value) Ma-Q regression
equation than Ma-S regression equation significant level, indicating that compared
with the slope drainage greater impact on the average sediment flow rate.
(2) Sediment concentration variation with time what has three main kinds:①
turn on the water flow is small and the slope is small, the sediment concentration over
a long period of time basically stable in the late test (18min) gradually decreases.②
Large or steep drainage flows when runoff sediment concentration early (9~12min
ago) decreases after.③Between sediment concentration between the first two cases
reduced with time small. Average runoff sediment concentration and drainage flow
was a negative linear correlation with the slope of the linear positive
correlation. Runoff and sediment relations under test conditions which can be used to
power function y=ax b expression, a value change between 0.388~1.445, b value
changes between 0.256 and 0.911; Brainage flow and slope with a value
increase increasing, and b values continue to decrease; when the drainage flow
60L/min, although still showing a positive correlation between runoff and sediment,
but the power function has not fit well the relationship between the two.
(3) The flow rate of each water distribution in the cell middle (vertical section 3)
are stable in the presence of a flow velocity 0.3~0.5m/s in cross-section. Section in
the section above, the average velocity over time as a whole showed a decreasing
trend drainage in the following section of this section, the average velocity over the
whole drainage time an increasing trend. The average depth of each observation
section of the drain with the extension of time are increasing; in the upper part of the
cell (section 1 and 2) with an average depth of rapid change, and in the lower part of
the cell (sections 3-5) average water depth is more soothing and has been at the in
between 0.5mm~1mm; average depth of the drainage flow is no obvious relationship.
(4) Under the experimental conditions substantially laminar flow overland flow
only in sections 1 and part-time for the transition flow; addition to individual
phenomenon, the overland flow are rapids areas; Froude number under the various
drainage flow and Reynolds number are negative correlation; drag coefficient and
Reynolds number exponential relationship exists, but no significant relationship with   the drainage flow.Analysis of changes in slope along the length of the drag coefficient
was found, slope length within the range of 0 to 6m intense soil erosion is a major part
of overland flow in the supply of sediment; 6 ~ 20m slope length within the range of
weak soil erosion in the region on the slope surface stream sediment supply remains,
but the slow rate of supply. Slope resistance coefficient and a positive linear
correlation between the depth of the water, so basically the same features and changes
in water depth.
(5) Flow shear stress increases with slope length changes can be well explained
by the cell soil erosion occurs mainly in the area of the upper part of the reason (0~
10m).Although there is a good flow shear stress linear relationship with unit area of
soil erosion rate, but due to the ability to represent the flow shear flow and erosion of
soil particles into overland flow, and the slope of the selected test areas are steep,
gravity erosion the strong performance of the erosion model is not suitable to explain
the change in erosion rate under the test conditions. Since water is a reflection of the
power handling capability of overland flow, so the stream power model can be applied
to the experimental conditions down to reflect the changes in soil erosion rates.
Keywords: Loess Plateau; accumulation of disturbed soil; erosion and sediment
yield; hydrodynamic characteristics; dynamic process

Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8991
Collection水保所知识产出(1956---)
Recommended Citation
GB/T 7714
张少佳. 扰动堆积土体边坡土壤侵蚀动力过程试验研究[D]. 北京. 中国科学院研究生院,2014.
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