Construction on dolomite in south Africa

Damage to structures and loss of life have been more severe on dolomite than on any other geological formation in southern Africa. The subsidence that occurs on dolomitic terrain following development or during dewatering has given dolomite a notorious reputation and engineers and geologists became reluctant to recommend development on the material. This has led to the pioneering of founding methods for a wide variety of structures aimed at reducing the risk of severity of damage due to subsidence settlement Structures successfully founded on dolomitic terrane include residential and industrial buildings, gold mine reduction works and shaft structures, tailings dams, water retaining structures, and road and rail links. In this article, various methods of construction, some ot which were developed by the authors, are presented. It commences with a classification of a dolomite site in terms of overburden thickness followed by a discussion of the relevant construction methods The methods include mattresses of compacted soil supported by pinnacles or “floating” in residuum, deep foundations such as caissons, the use of specialized piling techniques, and soil improvement by dynamic consolidation     

Die Berechnung der Angströmschen Trübungskonstanten aus Sonnenstrahlungsmessungen in verschiedenen Filtergebieten

Zusammenfassung Zur Bearbeitung von mehreren hundert Messungen der direkten Sonnenstrahlung mit fünf verschiedenen Farbfiltern werden Neuberechnungen derAngstr?mschen Formel (Gleichung 1) für die einzelnen Wellenl?ngen mit insgesamt 144 verschiedenen Werten für die Luftmassem, den Wellenl?ngenexponenten α der Zerstreuungsfunktion, dem Trübungskoeffizienten β und dem WasserdampfgehaltW der Atmosph?re durchgeführt. Es wurde hierbei festgestellt, da? es m?glich ist, die Filterdifferenzen für die Spektralbereiche Blau, Gelb, Rot und zwei Infrarot durch einfache algebraische Formeln darzustellen (Gleichungen 3 und 5), aus denen α und β errechnet werden k?nnen (Gleichungen 6 und 7). Bezüglich des Wasserdampfgehaltes ergab sich, da? es nicht m?glich ist, die Wasserdampfabsorption durch ein einziges Gliedf(mW) darzustellen, das additiv zu dem Zerstreuungsterm derAngstr?mschen Formel hinzugefügt wird, wie es bisher meist geschah. Es wurde eine neue Fassung des additiven Gliedes für die Wasserdampfabsorptionf(α, β, m, mW) berechnet und durch eine Formel (12) wiedergegeben. Auf die Bedeutung der neuen Absorptionsfunktion des Wasserdampfes für die vom Verfasser kürzlich entwickelte Kalibrierung der Aktinometer aus dem Beobachtungsmaterial wird eingegangen (Gleichung 14). Zum Schlu? werden neue Gleichungen (20) entwickelt, die die Bestimmung von α im langwelligen Spektralgebiet der Sonnenstrahlung erm?glichen, in dem auch der Wasserdampf absorbiert. Dies ist wichtig, weil das α, das bisher nur aus dem kurzwelligen Teil des Sonnenspektrum bestimmt werden konnte, nicht notwendig übereinzustimmen braucht mit dem α im langwelligen Gebiet.

---

Summary DeterminingAngstr?m’s turbidity constants from several hundred sets of readings of the solar radiation with five different glass filters,Angstr?m’s formula (equ. 1) was calculated for a total of 144 different values of air massesm, the wavelength exponent α of the scattering function, the turbidity coefficient β and water vapour content W of the atmosphere. It was found that it is possible to express the filter differences belonging to the spectral ranges blue, yellow, red, and two infrared ranges with simple algebraic formulae (equ. 3 and 5) which allow α and β to be calculated (equ. 6 and 7). With respect to the water vapour content it was pointed out that it is impossible to express, in the usual way, the water vapour absorption by a single termf(mW), which is added to the scattering term ofAngstr?m’s formula. A new form of the water vapour absorption was calculated and expressed as a formula (12). The significance of the new water vapour absorption function was discussed with reference to the author’s newly developed actinometer calibration from observational data (equ. 14). In conclusion new equations (20) were derived enabling to be determined in the long wave range of solar radiation, i.e. where the water vapour absorption exists. This is important because so far α could only be determined from the short wave range of solar radiation, which does not necessarily agree with that of the long wave range.

---

---

Dr. Fritz H. W. Albrecht, 10, Belgravia Ave., Box Hill North E 12,Melbourne.     

O18/O16-Isotopenanalysen und Paleotemperaturbestimmungen an Belemniten aus dem Schwäb. Jura

Summary Palaeotemperature determinations were made by the oxygen isotope method on 89 Belemnoids from the Schwäb. Jura, South Germany. The data derived show a well-defined maximum in the Upper Toarcian and Lower Bajocian (up to 29 C). This maximum is followed by a decline in the Upper Bajocian times (13.2 C –18.1 C). In the Lower and Middle Lias, as in the Malm, temperatures between 18 C and 24 C are prevalent.It is indicated that biological-ecological factors may change the O¹⁸/O³⁶ ratio of the carbonate of the rostra and consequently the palaeotemperature results.     

Neoproterozoic tectonothermal evolution of the Central Eastern Desert, Egypt: a slow velocity tectonic process of core complex exhumation

Regional cooling in the course of Neoproterozoic core complex exhumation in the Central Eastern Desert of Egypt is constraint by ⁴⁰Ar/³⁹Ar ages of hornblende and muscovite from Meatiq, Sibai and Hafafit domes. The data reveal highly diachronous cooling with hornblende ages clustering around 580 Ma in the Meatiq and the Hafafit, and 623 and 606 Ma in the Sibai. These ⁴⁰Ar/³⁹Ar ages are interpreted together with previously published structural and petrological data, radiometric ages obtained from Neoproterozoic plutons, and data on sediment dynamics from the intramontane Kareim molasse basin. Early-stage low velocity exhumation was triggered by magmatism initiated at 650 Ma in the Sibai and caused early deposition of molasses sediments within rim synforms. Rapid late stage exhumation was released by combined effect of strike-slip and normal faulting, exhumed Meatiq and Hafafit domes and continued until 580 Ma. We propose a new model that adopts core complex exhumation in oblique island arc collision-zones and includes transpression combined with lateral extrusion dynamics. In this model, continuous magma generation weakened the crust leading to facilitation of lateral extrusion tectonics. Since horizontal shortening is balanced by extension, no major crustal thickening and no increase of potential energy (gravitational collapse) is necessarily involved in the process of core complex formation. Core complexes were continuously but slowly exhumed without creating a significant mountain topography.     

Migmatization and “secondary” granitic magmas: effects of emplacement and crystallization of “primary” granitoids in Southern Bohemia,Austria

The Sauwald and Mühl zones of the prebatholithic, Moldanubian, middle crust in northern Austria contain metapelites and metaluminous to weakly peraluminous metagreywackes, respectively. Both zones were affected by low-pressure, high-temperature metamorphism and anatexis. The metapelites of the Sauwald zone became in-situ diatexites, probably by fluid-absent reactions involving the breakdown of muscovite and the partial breakdown of biotite. The biotite-plagioclase-quartz gneisses of the Mühl zone experienced only slight melting. Following this event, and while the mid crust was still hot, additional heat was locally advected into the Mühl zone by the intrusion of the Weinsberg granite. This brought about fluid-present partial melting of the biotite-plagioclasequartz gneisses, producing relatively large volumes of metaluminous to weakly peraluminous, I-type Schlieren granite. This cool, wet, restite-rich magma remained close to its site of generation. Thus, infracrustal I-type granitoids may be formed anywhere in the crust, and not always at high T. Under special circumstances the heat and fluids from granitic magmas can spawn secondary granites. Also, relatively low initial ⁸⁷Sr/⁸⁶Sr values (of around 0.707) in I-type rocks do not necessarily indicate either lower crustal magma sources or mixing with mantle-derived magma. The Weinsberg granite magma came from the lower crust (P probably <700 MPa), where widespread fluid-absent breakdown of biotite-plagioclase-quartz assemblages occurred. The necessary high heat flow was probably provided by newly underplated mafic magmas. However, these seem not to have mixed or mingled with the crustally derived Weinsberg magmas. Deep equivalents of the Mühl-zone metagreywackes may have formed the Weinsberg protolith. Fluid-absent experiments show that the melting temperature probably exceeded 850°C and that a garnet-bearing, orthopyroxene-rich residue should be present in the lower crust. Fluid-present experiments demonstrate that the availability of free H₂O can radically alter the characteristics of the partial melts, from apparent S-type mineralogy (with fluid-absent melting) to I-type mineralogy (with wet melting).     

Der Lauf der Ruhr als Modell einer heterogenen Stromlinie

Ohne Zusammenfassung     

Bestimmung von Umweltqualitätsnormen für potenziell gewässerrelevante Stoffe

With the Water Framework Directive (WFD) the European Commission (EC) is requested to define environmental quality standards for pollutants to protect aquatic life in surface waters. Quality standards have to be derived by a scientific risk assessment and should not be exceeded. The recommended quality standards are mainly based on long term toxicological tests with algae, crustaceans and fish. The lowest effect concentration is divided by an assessment factor between 10 and 1000, which considers the data quality and quantity. In this work funded by the German Länder Working Party on Water (Länderarbeitsgemeinschaft Wasser – LAWA) environmental quality standards for 40 considered relevant substances were derived for aquatic ecosystems. The data sheets cover the identification of the compounds, their behaviour in the environment (physical‐chemical properties, biotic and abiotic degradation, sorption, bioaccumulation), information about mode of action, uses, analytical determination and available quality criteria. Ecotoxicological effect concentrations for bacteria, algae, protozoa, aquatic plants, crustaceans, fish, amphibians, insects and molluscs are listed. For 17 of the 40 hazardous substances investigated, quality objectives above 1 μg/L were derived. For 12 substances the values were between 0.1 μg/L and 1 μg/L and for 5 substances lower than 0.1 μg/L. Incomplete ecotoxicological data sets of the remaining compounds do not allow the derivation of quality standards. Especially for drugs further ecotoxicological test results are needed.     

Preparation and evaluation of polyaluminum chloride sulfate (PACS) as a coagulant to remove natural organic matter from water

A series of polyaluminum chloride sulfate (PACS) coagulants, which have different SO₄^2–/Al³⁺ and OH/Al (γ) mole ratio, has been successfully developed using AlCl₃·6H₂O, Al₂(SO₄)₃·18H₂O and Na₂CO₃ as raw materials. The coagulation performance of PACS for removing natural organic matter (NOM) from surface water was evaluated, and the effect of SO₄^2–/Al³⁺ mole ratio and γ value in coagulants PACS on DOC and UV₂₅₄ removal was determined. Furthermore, the influence of pH and dosage of the selected PACS with a SO₄^2–/Al³⁺ ratio of 0.0664 and a γ value of 2.0, which achieved the best coagulation performance for the removal of DOC and UV₂₅₄ of all PACS coagulants, on the removal of DOC and UV₂₅₄ and residual aluminum concentration in treated water was investigated. The results were compared with the ones of polyaluminum chloride (PAC) with γ value of 2.0. The experimental data show that the performance of PACS as a coagulant was highly dependent on SO₄^2–/Al³⁺ mole ratio and γ value. Both for the selected PACS and for PAC, the best DOC and UV₂₅₄ removal results were obtained in the range of pH from 5.0 to 8.2 and at the coagulation dose of 5.0 mg/L as Al. Under the optimum coagulation conditions, the selected PACS gave higher DOC and UV₂₅₄ removal efficiencies, and lower residual aluminum concentrations in the treated water than PAC. The maximum removal of DOC and UV₂₅₄ for PACS was approximately 88.0% and 93.0%, respectively. At the optimum coagulant dose and pH 6.5, the concentration of residual aluminum in treated water by both selected PACS and PAC can comply with the regulated limits. The major mechanisms of NOM removal by PACS and PAC coagulation involve complexation‐charge‐neutralization‐precipitation.