A new engineering-geological rock durability classification

The construction of the 5.3-m diameter, 82-km long Orange—Fish Tunnel in the Republic of South Africa, in sensibly horizontal beds of mudrocks, siltstones and sandstones of the Karoo Supergroup (Upper Carboniferous to Triassic age), revealed the paramount importance of rock durability. The presence of non-durable rock types was found to be one of the causes of the rock distress problems encountered in some tunnel sections during construction.

Geomechanical tests conducted on representative samples of potentially difficult rock types from the Orange—Fish Tunnel, indicated important limitations of international rock material classifications, such as the Deere—Miller Modulus—Strength and the Deere—Gamble Durability—Plasticity systems. The inadequacy of these classifications in the case of the Karoo sedimentary rocks, underlined the need for a new rock durability classification which could be used for the timely indication of the presence of non-durable rock material sections at tunnel level.

An account is given of the lithology, mineralogy and the postulated weathering mechanics of the Karoo rocks encountered, as well as the application of these parameters to the numerical methods used for the quantitative assessment of rock durability. It is considered that a reliable appraisal of this time-dependent parameter can be provided by the measurement of the strength and free swelling properties of the intact rock material.

A new rock durability classification, styled the Geodurability Classification, is discussed. This empirical system appears to be practical and simple as it depends on the minimum number of index rock properties, which can be measured fairly rapidly in a field laboratory by means of simple test apparatus and semi-skilled labour. It is based on different ranges of ratios of the uniaxial compressive strength, σ_c, and the “Duncan” free swelling coefficient, ε_D, as index parameters. The intact rock material is classified according to a rating system which varies from “excellent” (Class A) to “very poor” (Class F).

The extensive use of the Geodurability Classification indicated such a system to be particularly relevant to compacted and weakly cemented rocks, where the tendency of the rock material to deteriorate with time (and not the presence of rock discontinuities such as joints and bedding planes) dominates the time-dependent behaviour of tunnel rock masses.     

Oberrheinisches Grundgebirge und Rheingraben

Zusammenfassung Anstelle des Rheingrabens befand sich während der variszischen Faltung eine von Blattverschiebungen durchsetzte Scherzone. Sie diente granitischen und gabbroiden Intrusiva sowie den Vulkaniten des Rotliegenden als bevorzugte Aufstiegsbahn. Vorzerklüftet und isostatisch unkompensiert behielt der Krustenspan bis zum Mitteldogger seinen kratonischen Zustand, gehalten von der Klammer variszischer Konsolidation. Vom Mitteleozän an hatten neuerliche Blattverschübe das basale Kluftgitter für die vertikale Grabentektonik vollends gangbar gemacht. Keilförmig trieb sich der Lineamentkörper in die Kruste vor, junge Füllmassen einsaugend und die Grabenschultern isostatisch aufstemmend. Die randlichen Widerlager wurden auseinandergetrieben, wodurch Raum für die sich steigernde Taphrogenese und den im Aquitan folgenden antithetischen Zerfall der Grabenscholle geschaffen wurde. Der dem aufwallenden basaltischen Substrat entspringende Grabenvulkanismus bildete den Höhepunkt krustaler Zerspaltung.

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The Rhine-Graben is preceded by Hercynian transcurrent faulting favouring intrusion and extrusion of granitic and gabbroide plutonites and lower Permian extrusives. Though fractured and isostatically out of balance, the Rhine-block remained cratonic until Middle-Dogger times on account of its "Hercynian" nature. From middle-Eocene times on, renewed transcurrent movements facilitated dip-slip movements along the graben-edge-faults. The Rhine block, sucked down the young fill and isostatically buckled the graben edges. Marginal buttresses were driven apart; they gave room for increasing thaphrogenesis and for anti-thetic collapse during Aquitanian times. Basaltic graben volcanism underlined the peak of tectonic activity.

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Résumé Lors du plissement varisque, il y eut à l'endroit du fossé rhénan, une zone d'écailles; celle-ci favorisa la montée de roches intrusives granitiques et gabbroïques ainsi que de volcanites du Rotliegend. Préalablement fracturée et dans un état isostatique non compensé, cette zone d'écaillés conserva son état cratonique jusqu'au Dogger moyen, enserrée entre des masses de consolidation varisque. A partir de l'Eocène moyen, de nouveaux déplacements des écailles préparèrent le réseau de fissures pour une tectonique verticale en fossé. Un segment linéamentaire s'enfonça en coin dans l'écorce, déterminant l'aspiration de nouvelles masses de remplissage et la montée isostatique des compartiments flanquant latéralement le fossé. Les contreforts ont été écartés les uns des autres, ce qui a fourni l'espace pour la taphrogenèse et pour la fragmentation antithétique du massif affaisé qui s'est produite à l'Aquitanien.La fissuration crustale a atteint son point culminant avec le volcanisme à caractère basique qui a fait éruption dans le fossé.

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Circumstellar dust shells around very young and massive stars

In this paper we investigate the properties of dust in circumstellar shells around very young massive compact IR sources (Becklin-Neugebauer objects).We found no correlation between the optical depth in the centre of the 10-m band and the 3.1-m ice band. An inverse correlation between the strength of the silicate feature and the colour temperature for the 8–13 m interval was detected. Our sample of BN objects extends this kind of relation already known for Mira stars and OH/IR stars to higher optical depths.We present a radiative transfer model for BN objects and discuss its main properties. Using this model, the interpretation of the observations led to the conclusion that the type of silicates present in the dust shells of very young stellar objects is different from that type around oxygen-rich giants and supergiants. These different silicates may be tentatively identified with pyroxenes and olivines, respectively.We studied the influence of the adopted dust model in deriving source parameters of BN objects. The object W3-IRS5 was discussed in some detail.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.     

Experimental investigations of astronomically important interstellar silicates

In this paper methods and results of laboratory experiments for the investigation of the silicate component of interstellar dust are reviewed. In Section 2 basic properties expected for astronomically important interstellar silicates (AIIS) are discussed. Chemical constraints coming from the abundance of elements, from the depletion in the interstellar gas and from theoretical calculations of the condensation processes point to magnesium silicates. Some basic structural properties of interstellar silicates, the expected high degree of lattice disorder and spectral features expected for interstellar silicate grains are discussed. In Section 3 a review on laboratory investigations of AIIS is given. Physical and chemical methods for producing amorphous silicates are summarized. Important measurements of optical data for AIIS are listed. Spectral characteristics of amorphous silicates produced in order to simulate the interstellar dust silicates are discussed. From the comparison of the observed MIR silicate bands with those of the experimentally produced silicates it is concluded that at least two types of dust silicates exist in interstellar space: molecular-cloud silicate (suggested to be of pyroxene-type) and late-type star silicate (suggested to be of olivine-type). The mass absorption coefficient at the 10 m peak of both types of silicate grains amounts to 3000 cm² g^–1 and the ratio of 20 to 10 m peaks amounts to about 0.5. Finally, open questions in connection with laboratory experiments are mentioned and recommendations for future experiments are given.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.     

Denitrification and Pesticide Elimination in Drinking Water Treatment with the Biodegradable Polymer Poly(ϵ‐caprolactone) (PCL)

A combination of denitrification and pesticide sorption with the biodegradable polymer poly(?‐caprolactone) (PCL) was examined. The function of PCL is to act as carbon source and carrier for the bacteria and simultaneously as sorbent for the pesticide endosulfan. In a short‐term examination (1 month) the addition of the pesticide endosulfan to a continuous‐flow fixed‐bed reactor resulted in an inhibition of biomass production without reduction of the denitrification performance. However in a long‐term semi‐batch reactor test (6 months) biomass production and partly denitrification rates were affected. No significant differences in microbial composition between the reactors were observed. Regardless of the type of reactor or presence of endosulfan, Acidovorax facilis was the main constituent.     

Bücher- und Zeitschriftenschau

Ohne Zusammenfassung     

Alaska in den Jahren 1909 und 1910

Ohne Zusammenfassung     

Observationally-based infrared efficiencies and planck means for circumstellar dust grains

In this paper the mean relative efficiency factors for absorption of dust grains in the wavelength range from 8 to 22 m have been derived from IR spectra of the optically thin dust shells surrounding the O-rich supergiants Cep, Ori, X Her, and R Cas. The resulting absorption efficiency curve has been extrapolated into the near as well as the far infrared regions, having regard to restrictions set by experience. Planck mean efficiency factors have been calculated for the temperature range from 30 to 1500 K. The curveQ _P(T), which shows a maximum atT=300 K, has been approximated conveniently by a power law on either side of this maximum.