ISWC OpenIR  > 水保所知识产出(1956---)
工程堆积体陡坡土壤侵蚀动力过程试验研究
张乐涛
Subtype硕士
Thesis Advisor高照良
2013-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Abstract

生产建设区水土流失是生产建设背景下集各类环境因子控制、人为因素影响及下
垫面条件为一体的综合环境影响体现,改变了原有地表物质组成、结构、形态及水沙
发生、发展规律。作为生产建设项目区人为生产建设活动产生的废弃物堆置而成的特
殊地貌单元,工程堆积体是生产建设区新增水土流失的重要来源,进一步探讨不同扰
动方式下工程堆积体坡面的土壤侵蚀过程、径流水动力学特性及侵蚀产沙的动力过程
对于深化对生产建设区不同地貌单元土壤侵蚀特征的认识和理解具有重要的实际意
义,本文以神府高速公路沿线典型弃土场为例,通过野外模拟径流冲刷试验,对线形
生产建设项目沿线工程堆积体陡坡的土壤侵蚀过程及其对坡面径流动力特性的动态
响应进行了研究,得出的初步结论如下:
(1)分析了陡坡条件下工程堆积体坡面土壤侵蚀过程。
在试验坡度(36°)条件下,重力侵蚀对径流含沙量的变化具有重要影响,重力
作用开始发挥重要影响的放水流量临界值在20 L·min-1~25 L·min-1 之间。不同放水流
量条件下影响径流含沙量的主导因子不同,主要包括径流量V、输沙率Tr 及冲刷时间
t 等,平均径流含沙量可以作为反映堆积体侵蚀特征的指标之一。堆积体坡面产沙过
程存在产沙量的突变、波动变化及稳定发展3 个阶段,不同坡段产沙量的空间分布特
征随着流量的增大出现持续平稳减小、震荡式波动衰减2 种变化形式。土壤剥蚀率
Dr 随放水流量的增加呈现波动式的变化,与单宽流量q 存在线性关系:Dr=0.693q+3.97
(R2=0.781,n=80),与时段产沙量M 及流宽b 呈幂函数关系:Dr=1.689M0.671b-0.669
(R2=0.799,n=80)。各观测时段内的产沙量M 与径流量q 之间呈幂函数关系(指数
>1,有线性相关趋势):M=0.5548qT
1.036(R2 = 0.822,n=80),次径流过程累积产沙
量Ms 与累积径流量Q 之间呈线性关系:Ms=0.687Q + 6.123(R2 =0.975,n=80)。
(2)分析了工程堆积体陡坡坡面径流的水动力学特性。
平均流速V 与径流量qT 之间呈幂函数关系:V = aqT
b(R2>0.86,n=5),对薄层
水流、细沟水流及径流全过程而言,a 值依次为6.69、2.4、3.2,b 值依次为0.28、0.22、
0.24,受表面粗糙度影响,薄层水流条件下径流量的指数<0.5;不同坡段的平均流速沿坡面呈“S”型曲线分布:
b
V = aeL(L 为坡长,b<0,R2>0.60,n=20),与径流量
相比,坡长对径流流速的影响更大。水深h 与径流量qT 呈简单的幂函数关系,薄层
水流条件下径流量的指数比室内研究结果略大,细沟流条件下径流量的指数比室内研
究结果偏小,沿程水深会出现极大值或极小值,水深是影响坡面径流水动力学特性的
主导因素,平均水深不宜作为描述堆积体坡面径流水深特征的指标。坡面径流多处于
过渡流状态,随冲刷时间的延续,由薄层水流的层流向细沟流的过渡流转变;径流型
态开始发生由过渡流向紊流转变的临界放水流量在20 L·min-1~25 L·min-1 之间,随放
水流量的增加,径流沿程开始出现不同的径流型态(面流一直呈层流状态,细沟流由
过渡流向紊流转换);径流Fr>1,表明坡面径流属急流范畴,Fr 随冲刷历时呈幂函
数递减,坡面径流由急流逐渐向缓流转变。不同坡段的平均阻力系数⎯ƒ与坡长L 之间
呈形如
k
f = meL(k>0,R2>0.70,n=20)的指数函数关系。阻力系数f 与弗罗德数
Fr 存在指数为负的幂函数关系:f = 4.70Fr-2,与雷诺数存在指数为正的幂函数关系:
f = 0.0024Re0.9592(R2 = 0.7956,n=80)。
(3)分析了径流含沙量及产沙量与坡面径流水动力学参数间的关系。
径流含沙量与水力半径、单位水流功率、雷诺数、阻力系数等水力参数间存在幂
函数、指数函数及对数函数3 类函数形式的数量关系,其中,除与单位水流功率呈正
相关外,与其余3 个参数均呈负相关(sig<0.001);各观测时段内的产沙量与雷诺数、
径流切应力、水流功率分别呈幂函数递增、指数函数递增、指数函数递增关系(sig
<0.001),径流的能量参数能够更好的描述工程堆积体陡坡坡面的泥沙产出过程。
(4)分析了工程堆积体陡坡坡面土壤侵蚀动力过程。
在坡面水蚀输沙动力过程的径流切应力模型中,薄层水流侵蚀的可蚀性参数为
5×10-3 s·m-1,搬运表层松散堆积物的临界切应力为0.02 pa;细沟侵蚀可蚀性参数为
3×10-3 s·m-1,产生细沟侵蚀的临界切应力为12.8 pa。在水流功率模型中,试验条件下
土壤侵蚀发生的平均临界水流功率为1.14 N·m-1·s-1,平均土壤可蚀性参数为7.6×10-3
s2·m-2;细沟侵蚀发生的临界单位水流功率为0.09 m·s-1,土壤可蚀性参数为1.15
kg·m-3,初步结果显示,单位水流功率并不能有效描述薄层水流侵蚀的输沙过程。从
试验的全部过程看,坡面土壤侵蚀速率与径流动能之间存在形如Dr=ln(F) + b 的数学
关系。过水断面单位能量能够较好的描述细沟侵蚀的动力输沙过程,一般表达形式为
Dr = a (E – b),试验条件下细沟侵蚀发生的临界断面单位能量为0.53 cm。
(5)生产建设区因其独特的下垫面条件,其侵蚀过程亦有其不同的表现形式和
发展特征,宜依其扰动方式及程度进行划分,分别单独进行研究,不宜照搬一般经验;坡面径流调控理论依然是生产建设背景下水土流失治理的指导思想;现行主要模型及
其控制方程均能较好的描述工程堆积体陡坡坡面细沟侵蚀动力过程,就拟合效果看,
水流功率理论>断面单位能量理论>单位水流功率理论>水流剪切力理论>坡面径
流动能理论;土壤侵蚀的动力过程描述中,力学参数与能量参数的选取各具优势,实
际应用过程中具体参数的选择要依实际问题加以判定,不可一概而论。工程建设堆积
体薄层水流侵蚀过程可能应该从力学参数的角度加以考察,而细沟侵蚀过程似乎更适
宜从能量参数的角度进行研究。
关键词:工程堆积体;陡坡;侵蚀产沙;水动力学特性;动力过程

Other Abstract

Soil erosion in production and construction areas is a comprehensive reflection of
environmental impacts as an integration of various controlling environmental factors,
human factors and surface conditions, which alters the original compositions, structures of
surface materials and morphologies, even bringing about important impacts on the basic
rules of occurrence and development of runoff and sediment. As a kind of special
geomorphic units stacked with spoils produced by artificial activities of production and
construction, engineering accumulation is an important source of soil erosion newly arising
in production and construction areas. It is of important practical significance for deeply
comprehension and understanding of soil erosion characteristics of different geomorphic
units in production and construction areas to further explore the soil erosion process,
hydraulic characteristics of runoff and dynamic process of erosion and sediment yield
under different disturbance. In the paper, a set of field pouring water scouring
experiments were conducted on steep slope with 72.7% gradient and 12-meter length of
typical spoil ground along the line of Shenfu freeway to investigate the soil erosion process
of deposit slope and its dynamic response to dynamic characteristics of slope runoff under
simulated runoff conditions. Preliminary conclusions drew from the experiments are as
follows:
(1) The soil erosion process of engineering accumulationin in steep slope under
simulated runoff conditions is analysed. Under experimental conditions, gravitational
erosion has great influence on the variation of sediment concentration, which has a critical
discharge of inflow in between 20 L·min-1 and 25 L·min-1; the dominant factors influencing
sediment concentration are not the same under different discharges, including run-off V,  sediment transport rate Tr and scour time t and so on. The average sediment concentration
can be used as an indicating parameter to characterize the process of soil erosion of
engineering accumulation in steep slope. The process of slope sediment yield falls into
three stages: abrupt, fluctuation and stable. Spatial distribution of sediment yield along
different slope profiles under different runoff conditions can be reduced to two types:
steady decrease and violently fluctuating reduction. Soil detachment rate Dr that
fluctuates with increasing discharges is linearly related with unit discharge q: Dr =
0.693q+3.97(R2=0.781,n=80), which can also be expressed as the power function of
sediment yield and flow width over different time-intervals: Dr
=1.689M0.671b-0.669(R2=0.799 , n=80). Sediment yield can be described with power
function of run-off over the same time-interval(exponent > 1, linear trend): M =
0.5548q1.036(R2 = 0.822,n=80),accumulative sediment yield Ms is linearly related to
cumulative run-off Q during each runoff event: Ms=0.687Q + 6.123(R2 = 0.975,n=80).
(2) The hydro-dynamic characteristics of steep slope runoff of engineering
accumulation under simulated runoff conditions are studied. Average flow velocity V can
be well simulated with a power function of flow discharge qT: V = aqT
b(R2>0.86,n=5),
and the exponent of flow discharge differs under different flow states. For sheet flow, rill
flow and the whole runoff process, the value of a is 6.69, 2.4, 3.2 respectively; the value of
b is 0.28, 0.22, 0.24 respectively. Subjecting to the effects of surface roughness, the
exponent of flow discharge for sheet flow is less than 0.5. Average flow velocity V of
different slope segments shows S-Curve trend with the increase in slope length
L:
b
V = aeL (b<0,R2>0.60,n=20); Compared to flow discharge, slope length has greater
impact on flow velocity. Flow depth h increases exponentially with flow discharge q, the
exponent of flow discharge for sheet flow is somewhat larger than indoor findings; on the
contrary, the exponent of flow discharge for rill flow is somewhat less than indoor findings.
It is inappropriate to describe the depth features of slope runoff generated on engineering
accumulation with the indicator of average flow depth. Flow depth is the leading factor
influencing hydrodynamic characteristics of slope runoff, the relationships between
average flow depth and slope length vary under different discharges, from which a
maximum or minimum value of flow depth along the distance was observed. The flow
regime of slope runoff mostly belongs to the transition flow condition, shifting from  laminar sheet flow to transitional rill flow as scour time continues; turbulence condition
occurs with the increase of water discharges, critical discharge controlling the
transformation of flow regime from transition to turbulence is between 20 L·min-1 and 25
L·min-1, different flow regimes exist along the distance(laminar for sheet flow all along,
changes from transition to turbulence for rill flow) . The value of Fr which has
exponential descending relation to time t (Fr= 12.576t-0.719, R2 = 0.894, n = 80) is mostly
greater than1, indicating slope runoff belongs to the supercritical flow condition, shifting to
subcritical flow condition with the water supply process gradually. Average resistance
coefficient⎯ƒ along the distance obeys exponential function of slope length L to increase:
k
f = meL (k>0,R2>0.70,n=20); Relationship between resistance coefficient f and Froude
mnuber Fr accords with negative power function: f = 4.70Fr-2, relationship between
resistance coefficient f and Reynolds number Re accords with positive power function: f =
0.0024Re0.9592 (R2 = 0.7956, n=80).
(3) The relationships between sediment concentration, sediment production and
hydrodynamic parameters of slope runoff are investigated. Relationships between
sediment concentration and main hydraulic parameters such as hydrodynamic radius, unit
stream power, Reynolds number, resistance coefficient in accordance with the equations of
power function, exponential function, logarithmic function and so on, of which sediment
concentration is positively correlated with unit stream power and is negatively correlated
with other 3 parameters(sig < 0.001). Relationships between sediment yield over
different time-intervals and Reynolds number, flow shear stress, stream power appear
different trends including power-function ascending exponential ascending and exponential
ascending respectively(sig<0.001), sediment yield process of engineering accumulation in
steep slope can be better described with runoff energy parameters.
(4) The dynamic process of soil erosion in steep slope of engineering accumulation is
simulated by using different theories. In the flow shear stress model, the soil erodibility
parameter is 5×10-3 s·m-1, and critical shear stress of carrying rickle on surface is 0.02 pa
under conditions of sheet flow erosion; the soil erodibility parameter is 3×10-3 s·m-1, and
critical shear stress of rill erosion is 12.8 pa under conditions of sheet flow erosion. In
the stream power model, average stream power of soil erosion is 1.14 N·m-1·s-1, and
average soil erodibility parameter is 7.6×10-3 s2·m-2 under test conditions; critical unit  stream power of rill erosion is 0.09 m·s-1 and Soil erodibility parameter is1.15 kg·m-3;
preliminary results show that sediment transport process of sheet flow erosion can not be
effectively depicted with unit stream power. In terms of the whole experimental process,
soil erosion rate Dr can be expressed as a logarithmic function of runoff kinetic energy F:
Dr=ln (F) + b (R2 = 0.5035, n=80). Unit energy of water-carrying section can be used to
describe dynamic process of sediment transport of rill erosion, which can be expressed
with the following equation: Dr = a (E – b) (R2 = 0.7624, n=65); critical unit energy of
water-carrying section of rill erosion is 0.53 cm under test conditions.
(6) Soil erosion process in production and construction areas has different forms and
shows different development characteristics, it is advisable to carry out relevant research
separately on the basis of clarifications of disturbance and intensity, not copying the
general experience; theories of slope runoff regulation can still provide important guidance
for comprehensive control of soil erosion in engineering and construction areas; dynamic
process of rill erosion in steep slope of engineering accumulation can be well simulated
with current models and control equations, in terms of fitting effects, all theories tested
should be ranged in the order of stream power theory>unit energy of water-carrying
section theory>unit stream power theory>flow shear stress theory>runoff kinetic energy
theory; mechanics indexes and energy indexes have different advantages on descriptions of
dynamic process of soil erosion in steep slope of engineering accumulation, which
should be determined on practical considerations instead of lumped together. It seems
that the dynamic process of sheet flow erosion and rill erosion ought to be investigated
from the perspectives of mechanics indexes and energy indexes respectively.
Key Words:Eengineering accumulation, steep slope, soil erosion and sediment yield,
hydro-dynamic characteristics, dynamic process

Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8942
Collection水保所知识产出(1956---)
Recommended Citation
GB/T 7714
张乐涛. 工程堆积体陡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,2013.
Files in This Item:
File Name/Size DocType Version Access License
工程堆积体陡坡土壤侵蚀动力过程试验研究.(1599KB)学位论文 开放获取CC BY-NC-SAApplication Full Text
Related Services
Recommend this item
Bookmark
Usage statistics
Export to Endnote
Google Scholar
Similar articles in Google Scholar
[张乐涛]'s Articles
Baidu academic
Similar articles in Baidu academic
[张乐涛]'s Articles
Bing Scholar
Similar articles in Bing Scholar
[张乐涛]'s Articles
Terms of Use
No data!
Social Bookmark/Share
All comments (0)
No comment.
 

Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.