Untersuchung von Cyaniden im Grundwasser des Testfeldes Süd

über einen Zeitraum von ca. 1 1/2 Jahren sind Grundwasserproben des ehemaligen Gaswerkstandortes Testfeld Süd auf Cyanidgehalte untersucht worden. Zur Unterscheidung nicht toxischer und hoch toxischer Cyanidspezies wurden die operativen Parameter Gesamtcyanid und leicht freisetzbares Cyanid in Anlehnung an DIN 38 45 D14 ermittelt. Messwerte für Gesamtcyanid lagen zwischen n.n. und 4.5 mg/l, Messwerte für leicht freisetzbares Cyanid zwischen n.n. und 34 μg/l. Modellierungen der Speziesverteilung mit PHREEQC ( Parkhurst & Appelo 2001) unter Verwendung standortspezifischer geochemischer Parameter weisen auf einen methodisch bedingten Artefakt hin, der zur Untersch?tzung der toxischen Spezies führen k?nnte. Die r?umliche und zeitliche Entwicklung der Cyanid-Messwerte deutet darauf hin, dass Cyanid im untersuchten Grundwasserleiter retardiert wird. Unter Berücksichtigung des geochemischen Milieus und der Zusammensetzung des Grundwasserleiter-Materials kommen F?llung oder Adsorption als retardierende Prozesse in Frage.     

Vorkommen von Vanadium im Grundwasser der Vulkaneifel

Grundwasser - In Quellwasserproben rund um den Ringseitert-Vulkankomplex südöstlich der Gemeinde Kirchweiler (Westeifel) wurden weit über dem Geringfügigkeitsschwellenwert...     

Zur Ermittlung der Verformungen von Stahlbetonbauteilen im Grenzzustand der Gebrauchstauglichkeit

In Beton‐ und Stahlbetonbau 104, Heft 8, wurden die für die Ermittlung der Verformungen von Stahlbetonbauteilen benötigte Normalkraft‐mittlere Dehnungslinie, bzw. Biegemoment‐mittlere Krümmungslinie erläutert. Ein Rechenmodell und ein dazugehöriges Näherungsverfahren sowie deren praktische Anwendungen werden hier vorgestellt. Abschließend wird ein Vorgehen zur Vordimensionierung mit begleitenden Hilfsmitteln dargestellt. About the Calculation of Displacements of Reinforced Concrete Members in the Servicebility Limit State In Beton‐ und Stahlbetonbau 104, issue 8, the determination of axial tensile force – average strain, respectively bending moment – average curvature diagrams, in order to calculate the displacements of reinforced concrete members, were explained. A calculation model for the deformations, an approximation of it, and their practical applications are explained. Finally, a method for preliminary dimensioning with accompanying diagrams and tables is presented.     

Untersuchung verschiedener Bodenmodelle zur Berechnung von Fundamentplatten im Rahmen von FEM‐Lösungen

Investigation of different models for the analysis of foundation slabs with reference to FEM solutions. The realistic interaction between a foundation slab and the soil in FE‐programs is a formidable and complex task, despite the availability of sophisticated software solutions. On the one hand the incorporation of the slab‐soil behaviour into conventional software programs requires considerable experience and thought and, on the other hand, existing software programs are often difficult to understand because of their complexity. Using common design examples four different models, which arc frequently used in FE solutions, are applied in this study. The results are compared and critically examined.     

Experimentelle Untersuchung von Punkthaltern

Experimental investigation on glass point‐fixings. For (glass‐) point‐fixings the structural analysis is often made by experiments due to the usually complex geometric properties of the fixing. The testing is thereby mostly limited to the determination of the load carrying capacity as there is no standard prescribing the testing procedure. But for safe and robust construction design the behaviour of the fixing under load must be taken into account. Therefore the draft standard DIN 18008‐3: “point supported glazing” shall provide a testing regulation that claims, besides the examination of the load carrying capacity, the determination of limit values to ensure the serviceability under load.     

Integrale Quantifizierung von Schadstoffmassenflüssen im Grundwasser – Konditionierung der numerischen Inversion der Konzentrationsganglinien von Immissionspumpversuchen

A series of integral pumping tests (IPTs) were conducted at a former gasworks site to quantify the contaminant mass flux and average concentration in groundwater along three control planes. The resulting concentration-time series were analysed numerically with the help of the inversion code CSTREAM and a flow and transport model representing the highly heterogeneous aquifer. Since the control planes cover the entire downstream width of the potentially contaminated area, they allow conclusions to be drawn about the current location and spread of the contaminant plume. Previous evaluations of integral pumping tests could calculate three scenarios concerning the spread of the plume around the IPT well: (i) the plume is located to the right of the well, (ii) to the left, or (iii) is distributed symmetrically around it. To create a more realistic picture of the plume position, a series of direct-push monitoring wells were installed along one control plane. The concentrations found in these wells were included in the numerical analysis to condition the inversion results, and resulted in a more pronounced plume centre and fringe, which supports the development of optimised remediation strategies.     

Untersuchung der thermisch‐hygrischen Eigenschaften von Ziegeln mit Hohlraumfüllung aus Recyclingmaterial

Investigation on the thermal‐hygral behaniour of bricks with canity filling by recycling meterials. In the investigation project was examined whether bricks with simple cavity structure have a higher heat resistance by use of a heat insulation material filling in the cavities. The insulation material is a recycled product made of polystyrene and wood covered and bonded with cement. The influence of the configuration and thickness of the perforated bricks with vertical perforations and the geometry of the cavities of the brick on the thermal moisture states was evaluated. For investigation of the thermal resistance and the heat transmission coefficients were used the simulation program THERM, that considered the heat transportation through conduction in the brick fragments and the transport mechanisms conduction, convection and radiation in the airfilled cavities. The software package WUFI 2D was employed for the investigation of moisture transfer in the bricks. The investigations showed that the composite brick insulation stone has a thermal resistance twice as high as the initial brick. The moisture states can be partially in the brick more than 80 % humidity. This load is estimated as uncritical because the wooden particles are covered with cement slime.