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

| 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 3 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 4 Introduction Experiment set-up Dimensioning Measurement program Outlook Experiment set-up

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 5 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 6 Introduction Experiment set-up Dimensioning Measurement program Outlook Experiment set-up

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 7 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 8 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 9 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 10 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 11 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 12 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 13 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 14 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 15 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 16 Introduction Experiment set-up Dimensioning Measurement program 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

| Institut für Wasserbau und Wasserwirtschaft | Fachgebiet Wasserbau | Prof. Dr. -Ing habil U. Zanke | Dipl. -Ing. T. Kubetzek | 17 Introduction Experiment set-up Dimensioning Measurement program Outlook End Thank you for your attention