Geotechnik最新文献

Zum Titelbild: Moderne Geobaustoffe sind technisch leistungsfähig und können heute gleichzeitig biologisch abbaubar sein. Die Naue GreenLine Produktlinie leistet ihren Beitrag zu umweltverträglichem Bauen und übernimmt überall dort, wo eine zeitlich befristete Funktion gewünscht ist, zuverlässig Funktionen wie Trennen, Filtern, Abdichten und Erosionsschutz. Ob Böschungssicherung, “mineralische Dichtungen von der Rolle”, Wegebau oder Küstenschutz: Anschauliche Projekte zeigen, wie sich diese Lösungen praktisch umsetzen lassen. Der Beitrag auf den Seiten A6-A9 gibt einen Ausblick darauf, wie bewährte Lösungen zukünftig noch grüner werden und zugleich effizient bleiben. (Foto: Naue)

Investigations on the slaking potential and disintegration resistance of sandstones and their causes

Sandstone frequently occurs in Germany's subsoil as foundation ground and is used as a building material or natural stone in various ways. Nevertheless, most of them are not durable, but show signs of disintegration over periods relevant to foundation engineering, which usually has a lasting effect on the quality of the construction, causes hazards, and therefore often requires expensive remedial measures. This paper presents a study in which 21 types of sandstone from ten different geological formations (Triassic to Tertiary) were examined and classified concerning their slaking potential. The results show that most of the investigated sandstones belong to the class of weak rocks, whereby various parameters determine durability and structural strength. In summary, an excellent correlation between the slaking index and structural strength was determined for the sandstones examined, and the sandstone groups were assigned to the slaking classes so that this group of rocks can be assessed in terms of their durability before a construction project. In future projects, such investigations can help to correctly categorize and classify the sandstones that occur in the subsoil or are suitable for further use during the preliminary geotechnical investigations in order to minimize risks and costs in the long term.

Diaphragm wall pit for lock construction - New construction of the Gleesen lock, Dortmund-Ems Canal-km 137.9

The DEK is divided into the southern section (Datteln to Bergeshövede) and the northern section (Bergeshövede to Papenburg). In the southern section of the northern stretch, there are six canal steps between Bergeshövede and Gleesen, which are also known as the “Rheine lock steps”. Originally, the lock staircase consisted of seven locks with an effective length of around 67 m and a chamber width of around 8.60 m. Between 1914 and 1918, six additional “large locks” with a usable length of around 160 m and a chamber width of 9.80 m to 10.00 m were added to these so-called “small locks”. The large Bevergern lock was designed so that it could take over the function of two canal stages (small Bergeshövede and Bevergern locks). The large locks at Bevergern, Rodde, Venhaus, Hesselte and Gleesen are now over 100 years old and need to be replaced. The new locks will have a chamber with a usable length of 140 m and a width of 12.50 m. This will enable large motor cargo ships (GMS) and oversized large motor cargo ships (üGMS) with a width of 11.45 m to pass through the Rheine lock steps in future. The Gleesen lock is located in the municipality of Emsbüren, Gleesen district, in the south of the district of Emsland.

On the reproducibility of sand sample preparation using robotic arms

In the present study, the reproducibility of the preparation of sand samples in geotechnical laboratory experiments was analyzed. The focus was on the use of two robotic arms – the industrial KUKA KR 16 R1610-2 and the smaller RoArm 2 MS – for the automated preparation of samples with homogeneous packing density using the pluviation method. Three different sands (HCU Sand, Elbsand, and Hamburg Sand) were examined with regard to their loosest state in accordance with DIN 18126:2022. The samples were prepared by raising a funnel at a constant speed to ensure uniform and reproducible packing density. In addition, funnel tests were conducted to determine the angle of repose φ_S. The geometry of the sand heaps was captured using LIDAR, and both 2D and 3D evaluations were performed. The results show very low variations in bulk density and repose angle, indicating a high degree of reproducibility in sample preparation.

Single and strip foundations on stone columns – Computation of settlement

Priebe's method for computing the performance of ground improved by stone columns is accepted as a standard design approach worldwide. In his seminal paper from 1976, Priebe presented his approach for the first time. He refined this approach later and provided a comprehensive explanation in his paper in 1995. Therein, he provides two graphs which can be used to calculate the settlement of single and strip footings founded on a group of stone columns. However, he does not explain the underlying fundamentals used to derive the curves presented in these graphs. Furthermore, the diagrams are intended for manual computations, making them less convenient for software implementation. Consequently, the authors revisited Priebe's 1976 approach for footings and further developed it in an equivalent manner to Priebe in his approach for unlimited grids of columns. This paper presents a new formula for calculating the improvement factor for single columns considering the compressibility of the column material. Additionally, an approximate solution for determining the area ratio of perimeter columns for arbitrary arrangements under foundation footings is presented. With these two contributions, Priebe's method for ground improvement under single and strip footings is easily applicable in software assisted calculations.

Für die Umsetzung von Projekten im Tief- und Tunnelbau im Lockergestein ist die Bestimmung der Eigenschaften des anstehenden Baugrunds eine wesentliche Voraussetzung. Die Eigenschaften vor dem eigentlichen Lösen sind gemäß VOB/C als Bandbreiten für die Beschreibung der Homogenbereiche nach den entsprechenden Gewerken anzugeben. Zusätzlich sind „wesentliche Änderungen der Eigenschaften und Zustände von Boden, Fels und sonstigen Stoffen nach dem Lösen“ anzugeben. Bei Bauverfahren im Tief- und Tunnelbau spielt üblicherweise auch die Interaktion zwischen Abbaugerät und Baugrund eine entscheidende Rolle, wie z. B. bei gemischt- und grobkörnigen Böden die Abrasivität für eine Abschätzung des Verschleißes oder bei feinkörnigen Böden die undrainierte Scherfestigkeit im Hinblick auf eine Verwertung. Diese Interaktion kann insbesondere beim Einsatz von Tunnelbohr- und Rohrvortriebsmaschinen oder auch bei Bohr- und Schlitzwandarbeiten einen großen Einfluss haben. Nachfolgend werden zusätzliche, d. h. über die gemäß VOB/C geforderten Kennwerte der Homogenbereiche hinausgehende Laboruntersuchungen empfohlen und beschrieben, die bei Arbeiten im Tief- und Tunnelbau im Lockergestein ergänzend durchgeführt werden sollten, um die Eigenschaften des anstehenden bzw. abgebauten/ausgehobenen Materials bestmöglich zu beschreiben. In diesem Zusammenhang werden auch Vorschläge für die erforderliche Zahl an Untersuchungen und die erforderliche Güteklasse der Proben gemacht.