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Bad Vilbel, Germany

Tziallas G.P.,Lahmeyer International Gmbh | Saroglou H.,National Technical University of Athens | Tsiambaos G.,National Technical University of Athens
Engineering Geology

The paper deals with the determination of the mechanical properties of heterogeneous rocks in the laboratory and proposes a methodology for predicting the rock mass strength of flysch formations consisting of siltstone-sandstone alternations in different proportions. In order to simulate such formations, composite specimens comprising superimposed disks of intact sandstone and siltstone material with different thickness ratios were prepared. Wave velocity (P and S), uniaxial and triaxial compressive strength and Young's modulus of the composite samples were determined in the laboratory. According to the laboratory results, the uniaxial compressive strength and Young's modulus decrease with the increase of the siltstone percentage in the specimens, and yield the strength of siltstone when the siltstone percentage in the rock is equal to 37%. Additionally, the triaxial compression tests on composite samples revealed a significant decrease of the mi parameter for a siltstone percentage of only 17%. A comparison is made between the results of the present study with similar laboratory and empirical references from literature. Finally, it was possible to suggest how the relation between uniaxial compressive strength, σci, and siltstone percentage, sl, may differ according to the ratio of the compressive strength of the two main rocks, weak and strong, which comprise the heterogeneous rock. © 2013 Elsevier B.V. Source

Edris M.,Lahmeyer International Gmbh
Applied Thermal Engineering

Multi-shaft and single-shaft configurations allow customization to optimize plant performance, capital investment, construction and maintenance access, operating convenience, and minimum space requirements. Technical comparison between both configurations at partial loads has not been published before. This paper will primarily address a comparison between the two configurations based on thermodynamic simulation results for a gross power capacity of approximately 800 MWel at ISO conditions. This capacity has been chosen based on power market requirements. The analysis approach for each configuration is divided into three components: (1) Performance, (2) Plant configuration, and (3) Environmental impact. The first component dealt with plant gross power output, plant gross efficiency, plant auxiliary power demand, plant generator losses and plant shaft power. The second component dealt with space limitations and extension capability. The third component dealt with specific emissions of NOx and specific emissions of CO2. The thermodynamic simulations have been carried out using Thermoflow® at base load and part load respectively. The results show that the single-shaft configuration is more suitable with regards to performance, NOx specific emissions, CO 2 specific emissions, start-up and extension possibilities. The multi-shaft configuration is more suitable with regards to space limitations, steam turbine shaft power, availability, and reliability. © 2010 Elsevier Ltd. All rights reserved. Source

Stabel B.,Lahmeyer International Gmbh
Underground - The Way to the Future: Proceedings of the World Tunnel Congress, WTC 2013

Commissioned in 1964 the Vianden Pumped Storage Plant is situated on Luxembourg's eastern border to Germany and is operated by the Société Electrique de l'Our (SEO) who is extending the plant capacity by 200 MW by installing an additional unit in a new powerhouse/transformer cavern (PHC/TC). As the Engineer for the previously commissioned stages and for the presently executed 11th Machine (M11), Lahmeyer's responsibilities included design and supervision of the underground works. For the powerhouse complex of the M11, geotechnical exploratory works were performed consisting of an adit, boreholes, in-situ and laboratory tests. The in-situ tests included: borehole scanning, stress measurement by borehole slotter, dilatometer tests and water pressure tests. The paper presents the results of the exploration campaign and the characteristic design parameters. The rock engineering analyses and design of the PHC/TC are elaborated and representative results are presented. By May 2011 the PHC/TC excavation has been successfully completed. The PHC/TC was monitored systematically and closely in several sections employing different types of instruments. The monitoring results were promptly evaluated and are presented and compared with the initially estimated values. A comparison shows a good match. The paper also reports on scheduled and achieved progress rates. © 2013 Taylor & Francis Group. Source

In July and August 2005 extreme floods occurred in the project, causing landslides above the diversion tunnel intakes. After the second slide both diversion tunnel intakes were blocked, resulting in the overtopping of the dam that had reached almost half height at that time. After studying many options for new/additional diversion concepts the selected solution included driving a provisional bottom outlet through the dam in drill & blast technology from the downstream to the upstream face into the reservoir. Source

Desalination plants are processing huge quantities of sea water for the production of high quality potable and process water. With regard to environmental impact the main concerns are the increased temperature and salinity of the process effluent (brine, cooling water) which has to be rejected to the sea. Many national and international environmental regulations and guidelines are stipulating dis- charge limits for temperature and salinity to be complied with by the projected desalination plant in order to obtain the environmental approval for operation. The World Bank guidelines, as well as many national regulations, assume a so called "Mixing Zone" around the point of water dis- charge, within which initial mixing with ambient sea water takes place, and stipulate limits for temperature and salinity increase over ambient conditions at the edge of this mixing zone. However, the size of this mixing zone is not clearly defined and the procedures by which the temperature and salinity values are to be determined are missing. In consequence compliance with the stipulated discharge limits can hardly be proven in quantitative terms and the results of Environmental Impact Assessment (EIA) reports are usually rather imprecise in this regard. This presentation describes in a simplified manner an alternative approach for assessment of the environmental impact and corresponding limitation of temperature and salinity increase due to water discharge from desalination and power plants, which is considered more adequate for this purpose. It is proposed to substitute the unclear criterion of a "Mixing Zone" size by the water volume available for dilution of the discharged effluent. A basic procedure for the determination of a minimum dilution water volume is outlined, considering the temperature or salinity increase between intake and outfall and the discharged water flow rate. The described general approach may be considered by both environmental authorities stipulat- ing discharge limits and the responsible project parties to enable a more adequate assessment regarding compliance of a desalination project with applicable environmental regulations on a sound data basis. © 2010 Desalination Publications. Source

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