Fakultät Umweltwissenschaften, Fachrichtung Hydrowissenschaften.

Hydrological Regime Simulation in Earth y g gDams and Dikes using the Program

PCSiWaPro® as a Basis for Stability AnalysisPCSiWaPro as a Basis for Stability Analysis

Kassel, 16.05.2014 Jinxing Guo

Table of contentsTable of contents

Introduction Introduction

Hydrological regime analysis

Description of simulation Program PCSiWaPro®

Simulation results

Further application of the simulation results (in general)

Literature

2

1. Introduction

• Dikes as an effective flood protection systems

1. Introduction

• Dikes as an effective flood protection systems • about 630 km of dike length in Saxony alone • Simulation is necessary, especially in forecasting floods for dams and dikes.

[Source: André Künzelmann / UFZ, flooding of the Elbe, August 2002] [Source: Website of TU Dresden]

3

Introduction

Dam stability is influenced by

Introduction

• Dam stability is influenced by

various factors, such as

construction soil materials andconstruction, soil materials and

geometry, atmospheric conditions

(e g precipitation) vegetation and(e.g. precipitation), vegetation and

so on.

Example for the instability of the dam

The effect of precipitation

• Direct influence on the water

content change in the unsaturated

slope and seepage line (in an

extreme rainfall event)

4

IntroductionIntroduction

The importance of vegetation on slope stability

• Influence on the water content in

the upper layer of dams via the

p g p y

the upper layer of dams via the

soil-plant-atmosphere continuum

(COPPIN ET AL 1990 ) (COPPIN ET AL., 1990.)

• Soil reinforcement from the root

system (Gray 1995) main effectsystem (Gray, 1995)—main effect

5

2. Hydrological regime analysis2. Hydrological regime analysis

Model analysis:

• Calculation of seepage in a dam model (numerical modeling)

Water balance (especially in an extrem rainfall event)

How fast is the unsaturated area moistened in order to lead t d i t bilit (l d lid )?to dam instability (landslide)?

unsaturated

saturated

Water balance in the saturated and partially saturated zone (I. Hasan et al., 2012)

6

2. Hydrological regime analysis

Laboratory analysis:

2. Hydrological regime analysis

Result from a physical model experiment in IWD of TU Dresden

[S Ai 2004][Source: Aigner, 2004]

Landslide in the partially saturated region Clear hydrological process

p y g

7

3. Description of Program PCSiWaPro®

Advantages:

3. Description of Program PCSiWaPro

Based on Richard‘s equation and van Genuchten-Luckner modelE t l l ti f li i

Advantages:

Exact calculation of seepage line in dams

Consideration of atmospheric boundary conditions root water boundary conditions, root water uptake and soil evaporation

Consideration of hysteresis in unsaturated zoneunsaturated zone

integrated weather generator for arbitrary time series in high resolutionimplemented parameter identification implemented parameter identification algorithm

Soil databases according to DIN 4022 and DIN 4220 plus pedotransferand DIN 4220 plus pedotransferfunctions

8

Description of Program PCSiWaPro®

Model setup

Description of Program PCSiWaPro

p

Transient flooding level, rainfall (an example)

Boundary conditions

Analysis of function of rubber wall (an example)

9

Description of Program PCSiWaPro®

Material parameters

Description of Program PCSiWaPro

10

4. Simulation results

1) Simulation for the laboratory experiment

4. Simulation results

Simulation of the physical dam model with atmospheric BC also a test of rubber wall efficiencyy

cm Pressure head

Water content

11

Simulation resultsSimulation results

2) Simulation for a dam in Germany

73 0Water Levels in the Dam

Comparison of the caculated and measured data

72,5

73,0

evel

) [m

]

71,5

72,0

ove

sea

le

70,5

71,0

rlev

el (a

b Pegel6398/ measured

computed by PCSiW P

70,0

0 30 60 90 120

150

180

210

240

270

300

330

360W

ater

PCSiWaPro

Time [d] (I. Hasan et al., 2012)

• showing a very good agreement between measured and computed values

12

g y g g

3) Simulation for an earth dam in China)

0,220,24

)

0,120,140,160,180,2

tion

(m

/d

)

0,020,040,060,080,1

Pre

cip

itat Precipitation

0,

Jan Feb Mrz Apr Mai Jun Jul Aug Sep Okt Nov Dez

Time

300301

a

294295296297298299300

ove

th

e se

am

)

289290291292293294

lev

el a

bo

leve

l (m

water level above the sea level

286287288289

Jan Feb Mrz Apr Mai Jun Jul Aug Sep Okt Nov Dez

wat

er

Time

13

Time

Precipitation and water level change of an earth dam in China in 2006

Simulation results

Change in the degree of pressure g g phead during the simulation time

(08.02.2006 – 30.06.2006)

Clear movement of the seepage line

14

Simulation results

Ch i th d f Change in the degree of water content during the

simulation time (08 02 2006 30 06 2006)(08.02.2006 – 30.06.2006)

15

Simulation results

Water content in the dam on 25.06.2006 Water content in the dam on 25.06.2006

smaller degeneration rate of soil water in the core when the water core when the water level falls clear sensitivity of the

model parameters (hydraulic conductivity, pore space diameter...)

2% 8%19% 40%

285 m

∆

16

Simulation results

280Water level in the dam slope

283 0

284,0

285,0

vel)

Water level in the clay core

276277278279280

a le

vel)

280,0

281,0

282,0

283,0

he

sea

lev

272273274275276

ve t

he

sem

)

measured by pore water pressure

276 0

277,0

278,0

279,0

(ab

ove

t(m

) measured by pore water pressure measurer (PE26)

l t d b PCSiW P269270271272

evel

(ab

ov (m

measured by pore water pressure measurer (PE15)

caculated by PCSiWAPro

273,0

274,0

275,0

276,0

ater

leve

l caculated by PCSiWaPro

265266267268

J F b M A M i J J l A S Okt N D

wat

er le

272,0

,

Jan Feb Mrz Apr Mai Jun Jul Aug Sep Okt Nov Dez

Wa

Time (2006)

Jan Feb Mrz Apr Mai Jun Jul Aug Sep Okt Nov Dez

Time (2006)

• The agreement between the measured values and the computed ones usingthe program PCSiWaPro® was good for both cases.

• Deviations could be caused by poorly estimated hydraulic soil parameterswhich are based on the given DIN 4220 values and not on actual measurementsfrom China.

17

Simulation results

Conclusion:

The agreement between measured and computed values was very

d i G

Conclusion:

good in Germany;

The deviation for Chinese dams was credited to the uncertainties of

i lmaterials parameters;

More local investigations of the soil parameters in China are necessary

in order to get better application results of PCSiWaPro.

The computation of various variants indicates clearly the sensitivity of

the Model parameters (geometry, soil parameters und geohydraulic

boundary conditions).

18

What’s it for?

leeyankun.blogspot.com

Too much water causes instability!

20

6. Application of the simulation results --- Stability analysis--- Stability analysis

Method for the stability analysis:Method for the stability analysis:

Basic definition --- factor of safty

• The "infinite slope" – Model

• Bishops simplified method

• Mohr Columb Model

To be improved

• Mohr-Columb Model

• Bacelona Basic Model

• Cambridge model

21

Stability analysis model

--- Mohr–Coulomb failure criterionMohr Coulomb failure criterion

--- Improvement of the Mohr-Coulomb Model by D.G.Fredlund (1993)

Reference: Pierre Delage, 2013

22

Stability analysis model

Fs (factor of safety) analysis within the root layer :Fs (factor of safety) analysis within the root layer :

• Significant reinforcement from the roots has been considered;• Weight of vegatation is neglected;• For Fs analysis under the root layer there is no C in the equation• For Fs analysis under the root layer, there is no Cr in the equation.

23

Stability analysis model

1) Cohesion (C') VS water content:

C0 - - initial soil cohesion with θr

(Guo, 2013)

C0 initial soil cohesion with θrC0 - - soil cohesion with θs

(B k B lli h 2009)(B.k.Bellingham, 2009)

2) Matric suction (Ua – Uw) VS water content

(by VAN GENUCHTEN-LUCKNER)

24

Stability analysis model

3) Friction (tanØ’) VS water content3) Friction (tanØ ) VS water content

(Bian Jiamin and Wang Baotian, 2011; Guo, 2013)

(Bian Jiamin and Wang Baotian, 2011)

4) tanØb VS water content

(S.K. Vanapalli et al., 1996)

25

Stability analysis model

Relationships between water content and those four Relationships between water content and those four parameters:

W

negative Cohesion (C' )Water

Content negative

negativeSoil internal friction (tanØ’)

θnegative

positive

Matric suction (Ua – Uw)

tan Øbtan Ø

26

Stability analysis results

Factor of safety analysis on different lays in the slope on one day (29.06.2006)

Depth inthe slope* Water Fs value

from the Fs value withoutthe slope*

(air side, m)

contentθ

from the new

model

withoutinfluence of

water content

Water content simulation from PCSiWaPro®

0.3 0.15 13.1 18.6

0.3' 0.15 4.6 14.4

1 0 15 2 6 5 5 Clear positive effect of root on the stability

1 0.15 2.6 5.5

10 0.19 1.7 5.4

20 0 1 1 8 1 9Necessity of protective structure on the bottom layer of the slope

20 0.1 1.8 1.9

50 0.05 0.9 1.8

*vegetation root depth = 0.5m‘ no vegetation layer

Failure Mode Foundation Type F.S.Shear Earthwork for Dams Fills etc 1 2 1 6

layer of the slope

Shear Earthwork for Dams, Fills, etc. 1.2 - 1.6(Bowels J. E, 1988)

27

Stability analysis results

Conclusion and outlook

Based on the simulation results of water content from PCSiWaPro®,

t bilit l i d l b t k f l t l t

Conclusion and outlook

new stability analysis model can be taken as a powerful tool to

forcast the possible landslides.

N d l i l h l f l f h d i i f h i d New model is also helpful for the determination of the size and

the structure (e.g. the core) of the dam.

Programing work of those relationship models into the program

PCSiWaPro® is in planning to get the distribution of the Fs value

ith th t t t hwith the water content change.

28

6. Literature

Bian Jiamin and Wang Baotian 2011; Research on Influence of Water Contents on the Shear StrengthBian Jiamin and Wang Baotian, 2011; Research on Influence of Water Contents on the Shear StrengthBehavior of Unsaturated Soils; Chinese Journal o fUnderground Space and Eng ineering;

Bowles, J. E. 1988. Foundation Analysis and Design, 4th Edition, McGraw-Hill.

D.Gfredlund, et al, 1993; Effect of pore air and negative pore water pressures on stability at the end-of-construction;

Francisco Sandro Rodrigues Holanda1 and Igor Pinheiro da Rocha, 2011; Streambank Soil Bioengineeringg g , ; g gApproach to Erosion Control;

Pierre Delage, 2013; Testing and modeling of unsaturated soil.

S. K. Vanapalli, D. G. Fredlund, D. E. Pufahl and A. W. Clifton 1996; Model for the prediction of shearstrength with respect to soil suction; Canada, Geotech. J. 33: 379-392 (1996).

Tien H. Wu ,2013; Root reinforcement of soil: Review of analytical models, test results, and applicationsto design; NRC Research Press;

USDA National Agroforestry Center; Vegetation for Bank Erosion Control.

Y ng X eming 1989 Cl ifi tion of oil tem nd oil te nd the m l ondition Soil 02 1989Yang Xueming, 1989 ;Classification of soil system and soil water and thermal conditions; Soil, 02.1989.

29

Thank you for your attention!

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Project introduction

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11. Doktorandenworkshop zur hydrologischen ModellierungKassel, 15-17.05.2014

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