Bad Vilbel, Germany
Bad Vilbel, Germany

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Ross R.,Lahmeyer International Gmbh | El Tayeb A.,Lahmeyer International Gmbh | Richter T.,Dams Implementation Unit
WasserWirtschaft | Year: 2011

The requirements for the implementation of an infrastructure project such as the Merowe Dam in Sudan were different from those of a large scale project in Europe. Distances inside the country, communication, timely procurement of large quantities of materials and equipment, lack of skilled manpower, accommodation, supplies and utilities for a labour force of6 500 men at peak times were to be considered during the entire construction period by the contractors. The employer, DIU, had assigned LI as the "Engineer" for the preparation of the detail design, contracts administration and construction supervision, engineering tasks which differed significantly from those required for a design and supervision project in Europe, for example, in view of the general duties and the quality controls regarding concrete and dam construction.

Semar O.,Lahmeyer International Gmbh | Witt K.J.,Bauhaus University Weimar | Fannin R.J.,University of British Columbia
Geotechnical Special Publication | Year: 2010

The paper gives an evaluation of current practice to assess the vulnerability to suffusion. Therefore comparisons of different approaches concepts are summarized. Suffusion is characterized by the phenomena that the fines can move inside a soil skeleton. In practice the vulnerability to suffusion is evaluated in two steps. First the geometrical possibility of fine movement is analysed. If the fine particles are mobile the hydraulic conditions come into focus as triggering force. In this contribution the authors concentrate on the geometrical criteria used in current design practice. A comparison of limit state conditions and an evaluation of laboratory studies will be delivered. In addition new approaches based on statistical and stochastically methods are discussed. © 2010 American Society of Civil Engineers.

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

Du C.,Lahmeyer International Gmbh
International Journal on Hydropower and Dams | Year: 2010

The post-cooling of roller-compaded concrete (RCC) dams using an embedded, high-density, polyethylene cooling pipe system is discussed. A number of professionals contend that the installation of cooling pipes during RCC construction may affect the RCC placement operations, and that the embedded, thin-walled pipes may be damaged by rollers and other heavy machines during placement and compaction of the RCC mix. Removing heat from mass concrete during initial construction is important to ensure the quality of the concrete. Critical to the success of post-cooling systems in RCC dams is the selection of suitable pipe material and corresponding construction procedure. HDPE pipes 32 mm in diameter were used as cooling pipes embedded in the RCC dam during RCC placement. The post-cooling is as applicable and effective for the temperature control of RCC dams as it is for conventional concrete dams.

Edris M.,Lahmeyer International Gmbh
Applied Thermal Engineering | Year: 2010

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.

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.

The successful grid-integration of the Merowe scheme marks a new era for Sudan's energy supply infrastructure. The 1400 MVA hydropower plant forms the central generation facility within the newly established 500 kV transmission network. The simultaneous commissioning of the large-scale units and the initial energisation of the backbone power grid required strategic time planning and the management of complex technical and organisational interdependencies.

Failer E.,Lahmeyer International Gmbh | El-Hadari M.H.,Dams Implementation Unit DIU | Mutaz M.A.S.,Dams Implementation Unit DIU
WasserWirtschaft | Year: 2011

The Merowe Dam and its hydropower plant is located on the Nile about 350 km north of Khartoum and about 550 km upstream of the Aswan High Dam in Egypt. This project has been designed to serve several purposes, namely: the generation of electricity by the ten generating units of its 1250 MW hydropower plant, the supply of water to centralized agricultural irrigation schemes (about 380000 ha) and the protection against the high floods of the Nile. In 2010 the Merowe hydropower plant generated more than 60 % of Sudans's electricity consumption. Furthermore, the Merowe Dam will act as a sediment trap, reducing the sedimentation of the Aswan High Dam further downstream in Egypt. Due to the fact that more than 90% of the reservoir area is desert land, "only" about 6 000 ha of agricultural land has been submerged. Therefore, there is only a very limited amount of biomass in the reservoir area, which results in the very low CO 2 emissions.

In this paper, the innovative technology and novel construction methods for construction of RCC arch dams which are successfully applied in Gomal Zam RCC arch-gravity dam are presented. Essentially, formation of the temporary transverse contraction joints, post-cooling of the RCC dam by means of the HDPE-cooling pipes embedded while RCC placing and joint grouting through a reinjectable/repeat grouting system are emphasised. The experiences and knowledge collected from the construction practice of Gomal Zam RCC archgravity dam demonstrated the suitability and acceptance of the technology and construction methods for RCC arch dams.

Tziallas G.P.,Lahmeyer International Gmbh | Saroglou H.,National Technical University of Athens | Tsiambaos G.,National Technical University of Athens
Engineering Geology | Year: 2013

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.

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