The Analysis about Seepage of the Bank Slope under the Cycle Rising and Drawdown of Reservoir Water Level

Abstract

Bank slope seepage field is analyzed by saturated-unsaturated seepage theory under the three times cycle conditions of water level rising and drawdown . The pore water pressure distribution laws of the water level rising period, the stabilization period, the period of decline and decline stable period for every cycle are researched. The result shows soil near slope region is saturated easily after many rounds of water level rising and drawdown, and saturation region gradually increases. Soil phreatic line near slope falls fastly in the drawdown period, away from the slope, phreatic line declines slowly.

Full text

The analysis about seepage of the bank slope under the cycle rising and
drawdown of reservoir water level
Xiao-wen Liu
1, a
,Wen Wan
1, b
,Xi-zhong Shen
2, c
1School of Architectural Engineering, Nanchang University,Nanchang 330031,Jiangxi,China,
2Yellow River Institute of Hydraulic Research, Yellow River Conservancy Commission, Henan
Zhengzhou 450003, China
a cnliuxiaowen@126.com, b Wanwen @163.com , c Shenxz@126.com
Keywords: water level rising and drawdown; cycle; saturated-unsaturated seepage; pore water
pressure; law.
Abstract. Bank slope seepage field is analyzed by saturated-unsaturated seepage theory under the
three times cycle conditions of water level rising and drawdown . The pore water pressure distribution
laws of the water level rising period, the stabilization period, the period of decline and decline stable
period for every cycle are researched. The result shows soil near slope region is saturated easily after
many rounds of water level rising and drawdown, and saturation region gradually increases. Soil
phreatic line near slope falls fastly in the drawdown period, away from the slope, phreatic line
declines slowly.
Introduction
The water influence on slope stability is very obvious. Bank slopes present saturated and unsaturated
alternating phenomenon under the cycle rising and drawdown of water level. Changes of the moisture
content of the soil slope can cause the soil strength and strain variation and when the water level falls
at the same time, permeability pressure will be also generated, it is very harmful for slope stability .
The change law of slope phreatic line and slope stability under reservoir water level change have been
researched by many scholars[1-3]. However, the seepage law of cycle rising and drawdown of
reservoir level is less studied. In fact the water level fluctuations is in ongoing. Therefore the study for
seepage law reservoir bank slope about reservoir level cycle fluctuation has an important engineering
significance to reveal the mechanism of slope landslide.
Saturated - unsaturated soil seepage equation
Differential equations of two-dimensional seepage can be expressed as[4]:
w
x y
H H
k k Q
x yyx t
θ
 
∂
∂ ∂∂∂   + + =


∂ ∂∂∂ ∂
    (1)
Where H is total head, Kx is the permeability coefficient of x direction, Ky is the permeability
coefficiention of of y direction, Q is boundary flow, θ is unit volume water content, t is time.
Unit volume water change is relation to pore water pressure through the following equation:
w w
m u
θ
∂ = ∂
(2)
Where
w
mis gradient of water storage curve. Total head H definition:
w
w
u
H y
γ
= +
(3)
Where u
w
is pore water pressure, r
w
is water density, y is elevation.
Applied Mechanics and Materials Online: 2013-08-08
ISSN: 1662-7482, Vols. 353-356, pp 112-115
doi:10.4028/www.scientific.net/AMM.353-356.112
© 2013 Trans Tech Publications Ltd, All Rights Reserved
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