ABSTRACT

The Urft dam, the Diemel dam and the Eder dam are three old masonry dams located in Germany. The paper describes the rehabilitation measures and the corresponding stability analyses carried out to adjust the dams to today's standards. Remedial works such as the excavation of inspection galleries, the installation of a grout curtain with a downstream drainage screen as well as the installation of pre-stressed permanent tendons were carried out. In all three cases the stability of the upgraded dam could be proven on the basis of finite element analyses.

ZUSAMMENFASSUNG

Die Urft-, Diemel- und Edertalsperre sind drei alte deutsche Schwergewichtsmauern aus Bruchsteinmauerwerk. Im Beitrag werden Instandsetzungsmaß- nahmen und Standsicherheitsnachweise beschrieben, die erforderlich waren, um die Staumauern an den heutigen Stand der Technik anzupassen. Hierzu wurden Kontrollgange aufgefahren, Dichtungsschleier mit luftseitiger Dranage sowie vorgespannte Daueranker hergestellt. In allen drei Fallen konnte unter Beruecksichtigung der Instandsetzungsmaßnahmen die Standsicherheit der Mauer auf der Grundlage von Berechnungen nach der Methode der finiten Elemente nachgewiesen werden.

RÉSUMÉ

Les barrages de Urft, Diemel et Eder sont trois barrages-poids vieux allemands construit de maçonnerie de moellon. Dans cet article, operations de remise en etat et preuves de stabilite sont decrits, qui etaient necessaires pour adapter les barrages à l'etat de la technique actuelle. À cet effet, des galeries de contrôle etaient creuses, voiles d'etancheite avec des drains à la face aval et tirants precontraints permanents etaient fabriques. Dans tous les trois cas, tenant compte des operations de remise en etat, la stabilite de la barrage pouvait être prouvee à partir de calculs selon la methode des elements finis.

Introduction

The stability of the Urft dam, which was built from 1900 until 1905, as well as the Diemel dam and the Eder dam, which were built between 1908 and 1923, was not sufficient under consideration of today's standards. Therefore, rehabilitation measures became necessary.

Urft dam
Dam and foundation rock

The Urft dam has a height of 58 m and a width at the foundation level of approximately 50.5 m. The 226-metrelong dam crest has a curvature with a radius of 200 m. The Urft reservoir has a storage volume of approximately 45 million m3 (Fig. 1).

The rock mass in the area of the dam belongs to the Upper Rurberger layers of the Lower Devonian. There are massive sandstone layers as well as alternating sequences of silt-, sand- and claystone layers at the left slope, whereas silt- and claystones are prevailing in the middle of the valley. The right hillside mostly consists of alternating sequences of silt- and sandstone layers. The orientation of the families of discontinuities, which are important for the stability and the permeability of the underlying rock, are shown in Figure 2.

(Figure in full paper)

Monitoring program and results

In order to adjust the dam to the generally acknowledged technical standards, an appropriate remediation program was developed. Most important elements of the rehabilitation measures were the excavation of two inspection galleries by blasting and the installation of a monitoring program.

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