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Author(s):	Steiner, Walter
Title:
Abstract:	Glacial soil deposits are present in Europe on both sides of the Alps, in Scandinavia, Northern Germany, Poland and in North America. There are typical names of the stages of the glaciation, however, the geotechnical characteristics of glacial deposits are similar in all regions; but are very heterogeneous locally. Glacial deposits extend from boulders to invisible silt particle (rock flour) and to clay particles, both of similar grain size. In this paper the focus will be on clean gravel without fines, so-called open gravel and the challenges and solutions for tunnelling. Face support by pure bentonite slurry is insufficient in open gravel. Different techniques have been used in practice: clogging the pore channels with fines of appropriate gradation by controlling the content fines in the slurry. Use of high viscous slurry with increased clay or bentonite content. In another solution lime powder and polymers were added in the excavation chamber of an earth-pressure shield to modify the ground. Other aspects such as muck disposal will be evaluated. Glaziale Lockergesteine kommen unter anderem in früher vergletscherten Gebieten von Europa (Alpen und Skandinavien) und Nordamerika vor. Die Eiszeiten werden mit spezifischen Namen bezeichnet und erreichten unterschiedliche Reichweiten und Ablagerungsbedingungen der Lockergesteine, die durch Schmelzwasser gesteuert wurden. Zum Verständnis der geotechnischen Eigenschaften, wie Kornverteilung, Durchlässigkeit, mechanische Eigenschaften, muss die geologische Geschichte verstanden werden. Es reicht nicht, aus Sondierungen Proben zu entnehmen und daran mit Korrelationen und Versuchen die bodenmechanischen Eigenschaften zu ermitteln. In durchlässigem Kies genügt Stützflüssigkeit aus Bentonit allein nicht, um die Ortsbrust im maschinellen Tunnelbau zu stützen. Es wurden verschiedene Methoden angewandt: Verstopfen von Porenkanälen mit geeignetem feinkörnigem Boden und ausreichendem Gehalt an feinem Material in der Stützflüssigkeit, die Anwendung hochviskoser Stützflüssigkeit mit höherem Gehalt von Bentonit und anderen Tonarten. Eine weitere Lösung bestand in der Beigabe von Kalkmehl und Polymeren in die Arbeitskammer von Erddruckschilden, um den Boden knetbar zu machen. Andere Aspekte wie Ablagerung und Kosten des Ausbruchmaterials werden auch erläutert.
Source:	Geomechanics and Tunnelling 16 (2023), No. 1
Page/s:	68-80
Language of Publication:	English/German

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