Funding Project Management Coordination Structural Approaches – Dikes, Reservoirs and Dams...

Funding Project Management Coordination

Structural Approaches – Dikes, Reservoirs and Dams

IMPROVEMENT OF THE GENERAL RESISTANCE OF DIKES AGAINST EROSION DURING DIKE OVERFLOW

Tobias Kubetzek, Jesper Steuernagel, Hendrik Ramm, Nicole Saenger, Ulrich Zanke

11.04.23 | Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 2

• Urbanization brought a great damage potential to the areas along the rivers and to former floodplains. This trend has not been stopped yet

• During the last flood periods several dams and dikes broke, causing enormous damage and the loss of many lives

• As a consequence of the climate change the sea level and the river gauges will rise. Dikes existing could lose their protectional function within the next years

• In the near future the majority of the German river dikes must be redeveloped

Introduction

Experiment Set-up

Dimensioning

Measurement program

Outlook

Introduction


Introduction

Introduction

Experiment Set-up

Dimensioning

Measurement program

Outlook

• Dikes effected by overflow must be built as an overflow structure, otherwise overflowing water erodes the top and the landside of the dike

• In general erosion leads to a quick collapse of the dike

• Common overflow section of dikes are protected by armourstones or concrete sealing. These methods are not suitable for the long distances of river dikes

• Conventional structures of geosynthetics are not practicable for redevelopement


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Experiment set-up


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Experiment set-up

• Full scale research dike (dimensions of a common dike along the Rhine, Germany)

• A closed sheeting and a high capacity propeller pump enable the overtopping of the dike

• Two experimental areas • Weir heads according to the width of the spillway slab


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Experiment set-up


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Experiment set-up

• Revetment with new combinations of geosynthetics– Erosion control mat– Geogrid (top layer)– Non woven geotextile– Geogrid (bottom layer)

• Top soil not as sacrificial layer but as part of the revetment

• Stable with and without vegetation


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Experiment set-up

• Fixing by pegs– State of construction– Worst case scenario

• Stabilization by root penetration– Common loading case– Difficult to calculate– Laboratory test of shear resistance


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Dimensioning

– Erosion of top soil and vegetation

– Gliding of the top soil on the geosynthetics

– Gliding of the geosynthetics on the ground

– Erosion beneath the geosynthetics

– Failure of the geosynthetics or the anchorage


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Dimensioning

– Erosion of top soil and vegetation

– Gliding of the topsoil on the geosynthetics

– Gliding of the geosynthetics on the ground

– Erosion beneath the geosynthetics

– Failure of the geosynthetics or the anchorage


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Dimensioning

• Wire heads up to 1.0 m causes shear stresses of approx. 900 N/m²

• Investigation of heads up to 0.3 m• Loads have to be transferred by pegs

Shear stress against the overflow

0

500

1000

1500

2000

0,0 0,5 1,0 1,5 2,0 2,5

q [m³/s/m]

max

t 0 [

N/m

²]


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Dimensioning

• Minimization of load-displacement • Search for an optimal pitch

• Reduction of effort while increase in efficiency• Reduction of the number of parts lowers the cost of

deployment and maintenance

Experiment 5Ad = 12mm; L = 500mm

0

10

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40

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60

70

80

0 500 1000 1500 2000 2500 3000 3500

Force [N]

Lo

ad

-dis

pla

ce

me

nt

[mm

]


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Dimensioning

• Finite-Element-Method (FEM) simulation of the deformation – ABAQUS 2-D-model

• FEM-simulation of the estimated forces during the overflow– ABAQUS 3-D-model

– Adaption of the peg pitch

– Adaption of the top anchorage


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Dimensioning

• Starting conditions– Peg dimension of 0.5 m length and Ø=12 mm

– Spillway slab of 20 m to 12 m

– Starting pitch 1 x 1 m

– Non-vegetated (worst case) revetment


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Measurement program

• Pressure sensor– Indikation of turbulences

• Area scanner– Deformation of the geosynthetics

• Ground radar– Erosion beneath the geosynthetics– Change in density of / rearrangement in the subsoil

• If applicable – Resistance strain gauges on the geogrid

• Turbidity sensor– Indication of erosion


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

Outlook

• Short-term experiments in 2008– Certification of the effectivity of the geosynthetic

combination (stability in a worst case scenario)

– Optimizing the pitch for the pegs

• Long-term experiment (winter 2008 / spring 2009)– Laboratory test of the shear resistance

– Overflow on the vegetated testing area

– Experiments with alternative erosion protection measures

• Aim– Consideration of our results in the guidance for the

remediation of the river dikes in Hesse, Germany


Introduction

Experiment set-up

Dimensioning

Measurement program

Outlook

End

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Funding Project Management Coordination Structural Approaches – Dikes, Reservoirs and Dams...

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