RESUME:

Les anciens puits, galeries et descenderies de mine qui debouchent au jour presentent des risques evidents pour la securite des personnes et des biens se situant dans leur zone d'influence directe. Parmi les differentes methodes mises en oeuvrepour traiter les anciens ouvrages miniers, nous presentons plus particulierement la technique du bouchon autoportant. Le bouchon autoportant est un massif en beton mis en place au sein de la colonne du puits et qui s'appuie sur le revetement du puits pour assurer sa propre stabilite, II est dimensionne pour reprendre son propre poids, etre capable de supporter une surcharge en tete et resister à un eventuel debourrage des remblais sous-jacents, Le principe du bouchon en galerie est tres similaire à celui developpe pour les puits, mais il doit, en plus, conforter les terrains en arriere de l'orifice sur une distance suffisante pour eviter tout risque de remontee de fontis. Selon I'inclinaison de la galerie et la nature des terrains de recouvrement, on compte alors sur l'autofoisonnement des terrains eboules ou sur l'auto stabilisation du fontis par formation d'une voûte stable au sein du recouvrement.

ABSTRACT:

: Former mining openings (shafts, adits and declines close to the surface), which are still open or simply covered up, present obvious hazards for the people and human activities near-by. Differents procedures are implemented to secure such openings, but the self-supporting plug technique is often the most appropriate method. Self supporting plugs are concrete structures implemented within the shaft and which rest on its lining to ensure their own stability. The plug must be able to bear its own weight, support an excessive load and resist to a possible underlying backfill column untampling. The principle of a plug in an adit is quite similar to that developped for shafts. However, the adit plug must also strengthen the rock mass at the rear of the opening over a sufficient area to prevent any sinkhole formation or subsidence. According to the type of overburden and slope of galleries, we can depend on rubble self-swelling, or on an auto-stabilization of the disorder with the forming of a steady vault within the overburden, to guarantee the long term stability of the galleries.

ZUSAMMENFASSUNG:

: Aufgegebene Tagesschachte und -Stollen bilden, in ihrem direkten Einwirkungsbereich, ein undiskutabeles Risiko fuer die Tagesoberflãche. In diesem Bericht werden verschiedene Sicherungsmaβnahrnen dieser aufgegebenen Grubenbaue prasentiert.

Im Detail beschreiben wir die Technik des selbshaltenden Propfens, welcher ein in den Schacht engefuegter Betonkiotz ist, der sich zu seiner eigenen Stabilitat auf die Schtwand anlehnt. Dieser Propfen wird so dimensioniert, daβ weder ein Übergewicht auf seinem oberen Ende, noch ein absacken des Fuellmaterials an seinem unteren Ende, sein abrutschen provozieren können, Die Technik des Stollenpropfens ist der des Schachtpfropfens sehr ahnlich, Ein solcher Stollenpropfen muβ aber ausserdem, auf einer ausreichenden Distanz hinter der aufgegebenen Öffnung, die Stabilitat des ehemaligen Stollen sichern, um Tagesbrueche zu verhindern. Je nach Einfallen des Stollens sowie der Geologie des Deckegebirges muβ eine solche Sicberungsmaβnahme soweit reichen daβ ein eventueller Bruch vor der Tagesoberflache auslaufen wird.

EXTENDED SUMMARY

It is quite a complex task to close down and secure mining sites that are abandoned or no longer exploited as such operations are subject to current laws and regulations as well as miscellaneous technical, financial, social and political parameters. More specifically, former mining openings (shafts, adits and declines that are close to the surface) constitute a major problem as several thousands of such works are presently scattered over France. Furthermore, their precise location is not always known accurately enough.

Shafts and adits which are still open or simply covered up present obvious hazards for the people and human activities nearby. Besides, mining works which were back filled in the past in a non-satisfactory fashion can also affect the surface's stability in case of sudden stowage movement. Therefore, it is essential to locate and deal with all suspected or acknowledged openings that require treatment in an efficient and perennial manner in order to make the land's surface safe.

Selection of the most appropriate method to secure such openings is based on a strict appraisal which requires collection of any available information concerning the work and its environment (location, geometrical characteristics of the opening, geology, hydrogeology, etc.)

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