Inverse Infiltration Modeling of Dike Covers Made of Dredged Material Using PEST and AMALGAM

Tim Jurisch,Fokke Saathoff,Stefan Cantré

doi:10.3390/geosciences11020041

Abstract

A variety of studies recently proved the applicability of different dried, fine-grained dredged materials as replacement material for erosion-resistant sea dike covers. In Rostock, Germany, a large-scale field experiment was conducted, in which different dredged materials were tested with regard to installation technology, stability, turf development, infiltration, and erosion resistance. The infiltration experiments to study the development of a seepage line in the dike body showed unexpected measurement results. Due to the high complexity of the problem, standard geo-hydraulic models proved to be unable to analyze these results. Therefore, different methods of inverse infiltration modeling were applied, such as the parameter estimation tool (PEST) and the AMALGAM algorithm. In the paper, the two approaches are compared and discussed. A sensitivity analysis proved the presumption of a non-linear model behavior for the infiltration problem and the Eigenvalue ratio indicates that the dike infiltration is an ill-posed problem. Although this complicates the inverse modeling (e.g., termination in local minima), parameter sets close to an optimum were found with both the PEST and the AMALGAM algorithms. Together with the field measurement data, this information supports the rating of the effective material properties of the applied dredged materials used as dike cover material.

Highlights

In engineering practice, numerical simulations of water infiltration are a component of the design of flood protection dikes
The Ks values estimated with parameter estimation tool (PEST) and AMALGAM (Ks(PEST-Var. 1b, M2) = 2.31 × 10−6 ms−1; Ks(AMA-Var. 1, M2) = 1.85 × 10−6 ms−1) both match the Ks(rel, M2) closer than the Ks values from the laboratory and field analyses
The AMALGAM result may be explained with possible realistic boundary conditions, this can only be seen as a strong hypothesis for the structure

Summary

Introduction

Numerical simulations of water infiltration are a component of the design of flood protection dikes. Infiltration analysis is required by national (German) and international standards and regulations for sea and estuary dikes as well as river dikes [1,2,3,4] This analysis is usually performed using hydraulic simulations in the steady and transient state to determine problematic hydraulic loads which may lead to failure, e.g., corresponding to the failure modes provided in the EC7 [5]. From these considerations, the desired material properties of individual construction elements are chosen in accordance with the applied directives and material availabilities. The predicted or predefined properties of these material properties are checked on the construction site by comprehensive laboratory and field tests

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Discussion

Conclusion