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Open access

Andrzej Pytlik

Abstract

At present, the suspended monorail systems constitute a very common means of transportation in the Polish hard coal mines. The main advantages of the suspended monorail include the independence of the route from the working floor surface irregularities and the possibility to transport cargo of significant mass and size.

The masses and dimensions of machines and devices transported via monorail have increased considerably in recent times. This particularly concerns the transport of longwall system elements. In Poland, the maximum speed of suspended monorail travel is 2 m/s. Due to the fact that preparations are currently underway to increase the maximum speed above 2 m/s, it is necessary to inspect what influence it will have on work safety and mining support stability.

Current operational experience and tests have shown that dynamic loads induced by the suspended monorail transportation have a significant influence on the roadway support stability, working protection durability and on the monorail operators. This is particularly true during the emergency braking of a suspended monorail by means of a braking trolley, where the overloads reach 3g.

Bench tests of the selected steel arch and rock bolt support elements utilised in the Polish hard coal mines were conducted in order to determine the resistance of steel arch and rock bolt supports to static and dynamic loads.

The article presents the results of the tests conducted on a steel arch support in the form of the sliding joints of an ŁP/V29 yielding roadway support, which is commonly employed in the Polish hard coal mines. Tests of elements of the threaded bolts with trapezoidal threads over the entire rod length were conducted as well.

The conducted strength tests of steel arch and rock bolt support elements under static and dynamic loading have shown that dynamic loading has decisive influence on the support’s retaining of its stability. Support element stability decreases along with the increase of the impact velocity. This concerns both the steel arch support and the rock bolt support.

Open access

Krzysztof Skrzypkowski, Waldemar Korzeniowski, Krzysztof Zagórski, Ireneusz Dominik and Krzysztof Lalik

Abstract

This paper discusses the pull-out laboratory tests and the monitoring of expansion-shell bolts with a length of 1.82 m. The bolts comprised the KE-3W expansion shell, a rod with a diameter of 0.0183 m and a profiled, circular plate with a diameter of 0.14 m, and a gauge of 0.006 m. The bolts were installed in a concrete block with a compressive strength of 75 MPa. The tests were conducted on a state-of-the-art test stand owned by the Department of Underground Mining of the AGH University of Science and Technology. The test stand can be used to test roof bolts on a geometric scale of 1:1 under static and rapidly varying loads. Also, the stand is suitable for testing rods measuring 5.5 m in length. The stand has a special feature of providing the ongoing monitoring of bolt load, displacement and deformation. The primary aim of the study was to compare the results recorded by two different measurement systems with the innovative Self-Excited Acoustic System (SAS) for measuring stress variations in roof bolts. In order to use the SAS, a special handle equipped with an accelerometer and exciter mounted to the nut or the upset end of the rod was designed at the Faculties of Mining and Geoengineering and Mechanical Engineering and Robotics of the AGH University of Science and Technology. The SAS can be used for nondestructive evaluation of performance of bolts around mining workings and in tunnels. Through laboratory calibration tests, roof bolt loads can be assessed using the in-situ non-destructive method.

Open access

Joachim Scheiner

Zusammenfassung

Die Mobilität von Kindern hat sich in den vergangenen Jahren zu einem kaum noch überschaubaren Forschungsfeld entwickelt, in dem Deutschland jedoch bemerkenswert still bleibt. Die Motivationen für die Forschungen liegen vor allem in der Zunahme des Mitfahrens im Pkw auf Kosten der nichtmotorisierten und/oder selbstständigen Mobilität der Kinder. Dies hat negative Folgen für die Gesundheit und Entwicklung der Kinder und ist unter anderem mit Problemen der Verkehrssicherheit und des Umweltschutzes verbunden. Der Beitrag gibt einen Überblick über das Forschungsfeld. Er diskutiert Schwerpunkte der Forschung, Methoden und Einflussfaktoren der Mobilität von Kindern. Darüber hinaus diskutiert er die – eher spärliche – praxisorientierte Literatur und zeigt Wege auf, wie die nichtmotorisierte und selbstständige Mobilität von Kindern gefördert werden kann.

Open access

Anna Growe and Tim Freytag

Abstract

The principles of sustainability are currently applied in Germany and many other countries as important guidelines for urban development. However, different forms of understanding regarding sustainable development and different approaches concerning its implementation can be found in various spatial contexts. This paper focuses on Freiburg, Heidelberg and Tübingen, three cities in southwestern Germany. These cities produce different images due to ambitious urban development plans which are based on the three pillars of ecological, economic and social sustainability in different ways. Numerous similarities between these three cities notwithstanding, they highlight different aspects of sustainable urban development and emphasise them via particularly widespread awareness of ‘showcase projects’. For Freiburg, this includes Vauban and Rieselfeld, for Heidelberg Bahnstadt, and for Tübingen Französisches Viertel and Loretto. The central questions in this paper are therefore: How do images and the implementation of sustainability differ with regard to the three pillars of sustainability? How can differences and similarities with regard to the three pillars of sustainability be explained and what consequences can be drawn for future studies in sustainable urban development? Following a classification of research perspectives on sustainable urban development, distinguishing between more practically oriented aspects, on the one hand, and theory-based critical considerations, on the other, this article examines showcase projects from the three selected cities on the basis of planning documents, websites, local newspapers and academic literature. Moreover, further projects are taken into consideration. The paper concludes with general observations and discussions concerning the image and implementation of sustainable urban development.

Open access

Mathieu Duval and Loїc Martin

Abstract

We used DosiVox to evaluate the impact of cement thickness on the dose effectively absorbed by the enamel layer. Until now, the thickness of the dental tissues adjacent to the enamel layer was not considered by any of the most widely used combined US-ESR dating programs (DATA and USESR). Instead, if adjacent tissues are present, their thickness is by default assumed to be sufficient to fulfill the infinite matrix conditions.

Our result suggest that such an assumption may represent in first instance a fair approximation of the reality, as even with a thickness of only 1 mm, the cement contributes to at least 98% of the beta dose rate coming from the outer side of the enamel layer. However, when cement is < 1 mm thick, DATA or USESR would overestimate the external beta dose rate and the value should be corrected accordingly by considering the relative contribution of the sediment. The impact of this correction on the total dose rate may vary, as it is directly dependent on the radioactivity of the cement itself, as well as of the sediment or dentine. Our results show that a very thin cement layer (0.1 mm-thick) can significantly contribute to the beta dose rate and should therefore not be neglected. Consequently, based on these results, we recommend the systematic measurement of the thickness of the dental tissues adjacent to the enamel layer during sample preparation, in order to proceed to beta dose rate corrections if necessary. Although this work has been especially focused on the case of fossil teeth showing cement, the conclusions stand for any other geometry involving different dental tissues adjacent to the enamel layer dated by ESR.

Open access
Open access

Charles C. Ekeh, Etim D. Uko, Ejiro F. Eleluwor and Friday B. Sigalo

Abstract

Geophysical well logs were used to delineate the stratigraphic units and system tracks in the XYZ Field of the Niger Delta. The gross percentages for sand levels range from 93-96% in the shallow levels to 60-66% in the deeper levels. Porosity values ranged between 27% at shallower sections and 9% at deeper depths. Six depositional sequences were identified and categorized into their associated system tracts. Porosity decreases with depth in normal compacted formation for both sandstone and shale units. Surface porosity for sandstone is 42%, and for shale it is 38.7% from extrapolation of sub-surface porosity values to the surface. The depth to the base of Benin Formation is highly variable ranging between 1300 and 2600m. This study reveals the possibility to correlate sand levels over long distances which enables inferring porosity values laterally. The knowledge of the existent stratigraphic units, the Benin, Agbada and Akata Formations and their petrophysical parameters such as porosity, lateral continuity of the sands and shales, the variation of the net-togross of sands with depth, enables the reservoir engineer to develop a plan for the number and location of the wells to be drilled into the reservoir, the rates of production that can be sustained for optimum recovery. The reservoir engineer can also estimate the productivity and ultimate recovery (reserves) using the results on this work.

Open access

Emilia Jaroszewska

Abstract

The industry which was a driving force of the economy and contributed to the population growth in many cities for decades became later the source of their problems. The crisis of the activity of old industrial cities creating the economic base (especially of the traditional industry), provoked by the deindustrialisation process and in post-socialist countries additionally by the “shock” of the economic transformation, caused long-lasting and unfavourable changes in many areas. It resulted in the present process of shrinkage of old industrial cities in demographic, economic, social aspects as well as spatial ones (Bontje 2004; Oswalt 2005; Turok, Mykhnenko 2007; Pallagst et al. 2009; Cunning-ham-Sabot et al. 2010; Bontje, Musterd 2012; Hospers 2012, 2014; Haase et al. 2013; Pallagst et al. 2014; Stryjakiewicz 2014; Runge et al. 2018). This process can take a different course in different socio-economic patterns depending on the geographical situation and the time of observation. However, it leads to unfavourable results in each place, first of all to a decrease in the number of inhabitants. The aim of the article is twofold: (1) the identification and analysis of the process of urban shrinkage of Wałbrzych city as well as (2) the examination of different regeneration strategies adopted to mitigate negative effects of urban shrinkage. It is particularly important to understand this process and results of the adopted strategies especially in the context of the future development of this city which according to demographic forecasts will be shrinking in the long run.

Open access

Barbara Maćkiewicz, Raúl Puente Asuero and Antonio Garrido Almonacid

Abstract

Increasing demand for urban agriculture (UA) can be perceived as a global phenomenon. In some parts of the world its main function is to feed the rapidly growing population while in others it is more associated with lifestyle and environmental issues. Undeniably, UA provides opportunities for sustainable city development. UA can support all pillars of sustainable development: ecological, economic, and social. However, depending on existing circumstances certain pillars may be influenced more than others. In this paper we concentrate on urban allotments in Andalusia and take Baeza as an example of a city with an interesting approach to urban gardening. We attempt to answer the question how urban allotments in Baeza affect the city’s sustainable development and what remains to be done to make this influence more effective. Our study showed that allotment gardens in Baeza endorsed all three pillars of sustainable city development. However, developing broader community relations on the city scale, revival of declining local grocery market and dissemination of environmental initiatives which allotment gardens may also promote and facilitate was missing.