Three-dimensional structural analyses of the shield-driven “Green Heart” tunnel of the high-speed line South

The tunnel lining generates a significant part of the bore tunnel project costs. This tunnel structure is one of the most important components of the whole tunneling process. The tunnel structure has to fulfill all necessary functional requirements during its lifetime. Because of this it is essential for engineers first to understand the realistic tunnel-lining behaviour and then to design a tunnel structure in a properway. The design of the lining structure is actually quite simple because of the wide range easy-to-use models now available. In contrast, predicting realistic tunnel-lining behavior is very difficult. The available numerical models for a segmented concrete lining cannot predict realistic structure behavior at all stages of excavation and during the tunnel lifetime. Conventional models ignore the influences of assembling processes, imperfections of segments, type of joints and variation in stress distributions in the concrete sections. This paper deals with three-dimensional finite element analyses of the tunnel structure, observations during the construction phase and in-situ measurements on the Second Heinenoord Tunnel (Bakker 1999) applied on the structural design of the shield-driven “Green Heart” Tunnel of the High Speed Line-South in the Netherlands.     

The “Landscape must become the law”—or should it?

The idea that society ought to be governed by the “law of landscape” must be seen in the context of the process by which the idea of landscape merged with that of nature in the course of the Renaissance and Enlightenment. In order to comprehend how these ideas morphed into the idea that “nature must become the law” as propounded by IFLA this history is traced. Through the linkages of “natural” social ideals with what was seen to be a “natural” style of landscape gardening, reforms sought to promote what often was seen to be a more just and economically, socially and physically sustainable form of society. This was an inherently conservative approach. It is shown how the ideas of landscape that developed from the Enlightenment to the period of land embellishment took a diabolical turn during the era of National Socialism in Germany. The idea of rooted-in-the-soil native plants as the ideal constituent of a German “landscape” continued among landscape architects and landscape planners after the liberation from National Socialism. Though somewhat diluted in the course of the second half of the twentieth century it re-emerged in a kind of renaissance in late twentieth and early twenty-first centuries under the terms “ecological planning” and the “nature garden”. Another source of these ideas lies particularly with the thinking of “anthroposophists”. The passage of a current legal landscape document, The European Landscape Convention, the heritage of the idea that “landscape must become the law” has gained new pertinence.     

Nitrogen elimination by rapid alternation of aerobic/“anoxic” conditions in “orbal” activated sludge plants

Methods of operation for obtaining maximum nitrogen elimination in the “Orbal” endless channel extended aeration plant are compared. The most efficient method required balancing of sludge concentration, organic load and oxygen input against one another in such a way that a rapid alternation of aerobic/anoxic conditions was brought about between aeration points in each channel. This resulted in minimal amounts of ammonia and nitrate remaining in the effluent. Automated control of oxygen input and of sludge concentration is considered necessary for consistent maximum nitrogen removal.     

Some practical aspects of the “biocarbon process”

In the presence of granular activated carbon the aerobic decomposition of organic compounds is facilitated (Koppe et al., 1974a,b). As could be shown by many laboratory tests several effects are given. First of all the faster adaptation of the bacteria has to be mentioned which is most important with substances which are difficult to be degraded like pentaerythrite. Additionally the degradation efficiency of the activated sludge process will be increased and equalized by granular activated carbon. Finally the effect of low temperatures can be compensated by the presence of granular activated carbon. With domestic wastewater for instance full nitrification could be obtained at a temperature of 4°C.Adsorption of organic compounds cannot be the explanation because the effect could be observed during several months whereas the calculated adsorption capacity had to be exhausted after two days. True causes are that specialized bacteria are retained in the pores and niches of the activated carbon in the lag-phase, that micro-organisms find area to grow in the log-phase (approximately 100 m²/m³ with 1 kg m⁻³ granular activated carbon) and that the enrichment of some exoenzymes at the activated carbon occurs (compare Figs. 1 and 2; and Müller & Sekoulov, 1975; Lue-Hing et al., 1976; Larsson et al., 1976; Rincke & Wolters, 1970). Since micro-organisms and activated carbon intimately react, this modification of the activated sludge process was called “biocarbon process” which has to be distinguished from the process with powdered activated carbon (de Walle & Chian, 1977).After completion of the laboratory tests, full-scale tests were started. In full-scale tests several difficulties had to be overcome. In some cases it was difficult to avoid the sedimentation of the granular activated carbon in the aeration tanks. Another task was the separation of the carbon from the surplus activated sludge. Finally it was of interest to determine how much carbon is lost by wet abrasion to be able to make a feasibility calculation. The full-scale tests have been performed in two wastewater treatment plants of the Ruhrverband: Nordenau and Günne.     

Philosophie des neuen DBV/BDZ‐Merkblattes “Sichtbeton”

Philosophy of the new DBV/BDZ‐Code of Practice “Architectural Concrete” In August 2004 the Deutsche Beton‐ und Bautechnik‐Verein E.V. (DBV) and the Bundesverband der Deutschen Zementindustrie e.V. (BDZ) published after 1977 and 1997 the third edition of the Code of Practice "Architectural Concrete". For the first time four classes SB 1 to SB 4 are defined which differ in demands on texture, porosity, steadiness of shade, evenness and quality of construction joints and formwork joints. Further demands concern test surfaces. In the main part comments on design and bidding procedure of architectural concrete and on their implementation are given. They are based on experiences which were made on prominent buildings on architectural concrete during the last years. The last part deals with the assessment of the architectural concrete surface. Principle is that the first and decisive criteria is the overall impression.     

The stabilization of “dissolved” iron in freshwaters

Laboratory experiments have been conducted to see what substances are capable of holding iron at a concentration of about 1 ppm in a “dissolved” form (i.e. will pass through a 0.45 μm pore size filter) in oxygenated water. The results show that reagents capable of doing this include humic and tannic acids, surfactants such as sodium dodecyl sulphate and sodium dodecylbenzene sulphonate, and the inorganic ions silicate and phosphate. In contrast, the synthetic polymer polyvinylpyrrollidone and the simple ions Cl⁻, HCO₃⁻, SO₄⁻ and NO₃⁻ showed no ability to stabilise iron. The efficiency of phosphate at keeping iron in the “dissolved” state was found to decrease in the presence of cations, particularly divalent ones, but increased with rise in water pH in the range 6–11.It seems unlikely that much of the stabilization observed for any of the reagents tested is due to their forming complexes with the iron. A much more likely explanation is that the substances for which positive results were obtained are able to stabilize fine colloidal iron particles and inhibit them from forming larger aggregates.     

From the gardens of the Qur'an to the “gardens” of Lahore

Mughal gardens are often interpreted as symbols of an Islamic paradise, but the precise relations between historical gardens and religious meaning remain vague. To clarify these relations, this paper compares garden imagery of the Qur'an with historical places of Lahore, Pakistan, “the Mughal City of Gardens”. Part one surveys garden imagery in the Qur'an to identify theological and aesthetic attributes of paradise. Part two shows how historical gardens, mosques, and shrines in Lahore exemplify different aspects of paradise symbolism. The results suggest new directions for the study of historical gardens and paradise symbolism in Muslim cultural landscapes.     

Risk assessment of “down-the-drain” chemicals: Search for a suitable model

Legal and regulatory authorities around the world generally require that risk assessments are undertaken for the licensing of new and existing substances that present high risk to the environment or the human health. This applies to ‘down-the-drain’ chemicals that are usually found in household products, such as detergents, that are mainly discharged into rivers via sewer systems. However, the data available for these chemicals is often limited due to cost constraints: in particular, concentration time series for works effluent are generally unavailable, even load data for specific works is often scarce.Although a wide range of models are available, there is a general lack of knowledge on their suitability to model the fate of down-the-drain chemicals at the catchment scale. Several models are presented in this review. The models selected are: the Mackay models, EUSES, Mike 11, QUAL2E, TOMCAT and GREAT-ER. Various applications of these models were investigated to investigate their strength and weaknesses. It appears that, where the availability of data is limited, multimedia fate models such as the Mackay models and EUSES may best be applied to estimate the global risk within each media. However, for site-specific risk assessment the GREAT-ER in-stream water quality model was considered to be more appropriate for modelling down-the-drain chemicals, because it accounts for both spatial and temporal variability, while its data requirements are lower than for models such as Mike 11 and QUAL2E.