2027
Large tailings heaps and the influence on infrastructures due to the resulting soil
deformation
Les grands terrils miniers et leur influence sur les infrastructures voisines à travers la déformation
des sols
Katzenbach R., Leppla S.
Technische Universität Darmstadt, Institute and Laboratory of Geotechnics, Germany
Seip M.
Ingenieursozietät Professor Dr.-Ing. Katzenbach GmbH, Frankfurt am Main, Germany
Schleinig J.-P.
K+S Aktiengesellschaft, Kassel, Germany
Schnürer F.
K+S KALI GmbH, Kassel, Germany
ABSTRACT: In the context of potassium fertilizer production the residua, mostly consisting of granular rock salt, is stored on large
tailings heaps. The salt residue has a strongly visco-plastic material behaviour with a rate-dependant strength. The heaps have a base
area up to a square kilometre and heights up to 120 m. Using the Finite-Element-Method (FEM) and a numerical constitutive law for
the salt residue, developed at the Technische Universität Darmstadt (TU Darmstadt), the influence of the heaps on infrastructures like
buildings, streets, railway tracks and pipelines can be estimated. In the context of the approval procedures of the extension of existing
heaps comprehensive numerical investigations regarding stresses and deformations are necessary to guarantee the stability and the
serviceability of the heaps and influenced infrastructures. For verification of the numerical investigations according to the
observational method monitoring programs have to be installed.
RÉSUMÉ : Dans le contexte actuel de production d’engrais riches en potassium, les résidus, principalement constitués de sel gemme
granulaire, sont stockés sous forme de larges terrils. Les résidus salins présentent un important comportement visco-plastique, et une
résistance à la rupture fortement dépendante du temps. La surface occupée par ces terrils peut atteindre un kilomètre carré et une
hauteur de 120m. L’influence de ces terrils sur les infrastructures du type bâtiments, routes, rails et pipelines peut être estimée en
combinant la Méthode des Eléments Finis (MEF) et l’utilisation d’une loi constitutive numérique pour le matériau salin, développée à
la TechnicheUniversität Darmstadt (TU Darmstadt). Dans le contexte actuel qui encourage l’extension des terrils existants, il devient
nécessaire de mener des études numériques poussées évaluant les contraintes et déformations, afin de garantir la stabilité et le bon
fonctionnement des terrils et des infrastructures avoisinantes. Des programmes de contrôle doivent être mis en place afin d’effectuer
la vérification des études numériques, obtenues grâce aux méthodes observationnelles.
KEYWORDS: Tailings heap, visco-plastic material behaviour, observational method.
MOTS-CLES : Terrils miniers, comportement visco-plastique, méthode observationnelle
1 INTRODUCTION
During the production of potash and the converting into
fertilizer for agriculture and into specialty products for the
chemical industry a large amount of residua, mostly consisting
of granular rock salt, is deposited on large heaps. The resulting
tailings heaps with a ground view up to 1 km² and a height up to
120 m cause normal stresses of 2,200 kN/m² and shear stresses
of 550 kN/m² on the contact surface. An impression of the
dimensions of such tailings heaps is given in Figure 1.
Figure 1. Rock salt heaps.
For analyses of the load and deformation behaviour of the heaps
the Finite-Element-Method (FEM) in combination with
elastoplastic constitutive laws for the soil and a viscoplastic
constitutive law for the granular rock salt, developed at the
Institute and Laboratory of Geotechnics of the TU Darmstadt,
are used.
The verification of the developed constitutive law for the
granular rock salt was done by back-analyses of laboratory tests
and the monitoring data of specific projects. The paper focuses
on the challenges of an extension of a tailings heap and the
influence on a railway track as only 1 example from engineering
practice (Katzenbach et al. 2004, Katzenbach et al. 2006).
2 PROJECT DESCRIPTION
In order to ensure the further production an existing 120 m high
tailings heap needs to be extended (Figure 2).
The planned extension of the tailings heap approaches the
railway track to the south. The existing heap was stored in
blocks with a lower and an upper layer (Figures 3 and 4). The
slope ratio is up to 40°. Since 2008 the extension is stored with
layers on the slope (Figure 5).
