Analogy between indentation and blasting tests on brittle rocks

SummaryAnalogy Between Indentation and Blasting Tests on Brittle Rocks This paper presents a common mechanism of breaking quasi-brittle rocks either by drilling and blasting or by indentation. Only minor modifications, to account for the prevailing boundary conditions pertaining to either one of these cutting processes, are required.Rock breakage by drilling and blasting or by indentation is based on the formation of a heterogeneous stress field due to the application of concentrated loads either by the indentor or by the detonation of the explosives. Rock behavior varies according to the stress level generated into the material. In the high stress zone it is plastic or pseudoplastic. In low stress region, failure is of the brittle extension type.In indentation the formation of a confined plastic zone is essential before chipping. However, for blasting plasticity is not necessary to occur prior to chipping because the high pressure gases that are generated from the explosion are usually quite sufficient — under suitable conditions — to create failure by extension cracking.Energy consumed in these rock cutting processes is a function of the relative amount of fines produced and their size distribution (or degree of fineness). Further improvements in rock breakage efficiency can be achieved by the proper choice of the important parameters for the specific techniques.The above analogy can be extended to other well known rock testing and breakage techniques.

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ZusammenfassungAnalogie zwischen Eindruck- und Sprengversuchen bei sprödem Gestein Dieser Bericht befaßt sich mit einem verbreiteten Verfahren zum Brechen von quasi-sprödem Gestein durch Bohren und Sprengen oder durch Eindrücken einer Spitze. Es sind nur geringe Veränderungen nötig, um die wichtigsten Randbedingungen des jeweiligen Bruchverfahrens zu berücksichtigen.Das Brechen von Fels durch Bohren und Sprengen oder durch Eindruckbeanspruchung beruht auf der Erzeugung eines inhomogenen Spannungsfeldes durch Aufbringung konzentrierter Lasten mittels einer Eindruckspitze oder einer Sprengung. Das Verhalten des Gesteins wird von der Spannungsintensität bestimmt. In Bereichen hoher Spannung ist es plastisch oder pseudoplastisch. In Zonen niedriger Spannung erhält man Dehnungssprödbrüche. Bei der Eindruckbeanspruchung ist die Ausbildung eines begrenzten plastischen Bereichs vor der Bruchauslösung ausschlaggebend. Dagegen ist für Sprengung plastisches Verhalten nicht notwendig, da die bei der Explosion entstandenen Gase unter hohem Druck bei vergleichbaren Voraussetzungen gewöhnlich völlig ausreichen, Zerstörung durch Dehnungsbruch herbeizuführen.Die für solche Felsbruchverfahren benötigte Energie ist eine Funktion des gewünschten relativen Feingutanteils und dessen Größenverteilung (oder Feinheitsgrad). Die Effektivität von Felsbruchverfahren kann durch richtige Wahl der wichtigen Parameter für die jeweilige Technik gesteigert werden.Die oben beschriebene Analogie kann auf andere bekannte Test- und Bruchverfahren übertragen werden.

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RésuméAnalogie entre poinçonnement et foudroyage des roches fragiles Cet article traite du mécanisme de rupture observé lors du poinçonnement et du foudroyage de roches du type fragile. Des modifications d'importance secondaire sont à apporter à ce mécanisme pour tenir compte des conditions aux limites propre à chacun de ce deux éssais.La rupture des roches dans des éssais est due à l'existence d'un champ de contraintes hétérogène résultant du poinçonnement or de la détonation des explosifs. Le comportement rhéologique des roches varie selon l'intensité des contraintes. A la zone comprimée, elle est du type plastique ou pseudoplastique. Par contre, dans la zone tendue, la rupture est du type fragile par extension.Dans la poinçonnement, la formation de la plasticité confinée sous le poinçon précède l'écaillage. Alors qu'en foudroyage la mise en plasticité autour du trou n'est, à priori, pas nécessaire, la forte préssion du gaz après la détonation pourrait — sour certains conditions — suffire pour rompre la roche autour de la charge d'explosif.La dépense énergétique dans le phénomène de rupture dépend de la taille des fines et de leur pourcentage dans les produits de rupture. Le choix approprié des paramètres importants du processus de coup résulte en une amélioration du son rendement.Enfin, l'analogie décrite ici pourrait être étendue à certains techniques d'éssai et de coupe de roches fragiles caractérisés par un champ de contraintes hétérogène.

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Isotopic and chemical investigations on Angra dos Reis

We report on extensive isotopic studies of Pb, Sr and Xe and on chemical abundance measurements of K, Rb, Sr, Ba, Nd, Sm, U and Th for total meteorite and mineral separates of the Angra dos Reis achondrite. U-Pb, Th-Pb and Pb-Pb ages are concordant at 4.54 AE for the total meteorite and for high-purity whitlockite in Angra dos Reis. This establishes Angra dos Reis as an early planetary differentiate which has not been disturbed for these systems since 4.54 AE ago. Measured⁸⁷Sr/⁸⁶Sr in pyroxene and whitlockite for Angra dos Reis (ADOR) are distinctly below BABI by two parts in 10⁴ and only one part in 10⁴ above the lowest⁸⁷Sr/⁸⁶Sr (ALL) measured in an Allende inclusion. The difference in ADOR-ALL corresponds to an interval of condensation in the solar nebula of ～3 m.y. If²⁶Al was the heat source for the magmatism on the parent planets of Angra dos Reis and the basaltic achondrites (BABI) then the relatively large difference in⁸⁷Sr/⁸⁶Sr, BABI - ALL, must be the result of planetary evolution rather than condensation over ～10 m.y. Xe isotopic measurements confirm the presence of large amounts of²⁴⁴Pu-produced fission Xe and show that²⁴⁴Pu was enriched in the whitlockite relative to the pyroxene by a factor of ～18. We present chemical element enrichment factors between the whitlockite and the fassaitic pyroxene in Angra dos Reis. The enrichment factors demonstrate close analogy between the rare earth elements and their actinide analogs. The enrichment factor for Pu is intermediate to the enrichment factors of Nd and Sm.     

Soil studies for highway construction in arid zones

An appreciation of the special features of the desert environment is necessary for proper construction and subsequent maintenance of highways in arid zones. Geotechnical tests and chemical analyses were carried out on a large number of samples of dune sand collected from four different sites in the Sahara desert. It is concluded that greater use can be made of local materials and that cement-stabilized sand should prove an adequate base for highways. Some useful suggestions are given for engineers operating in the hot deserts.     

Sample preparation and analytical techniques for determination of polyaromatic hydrocarbons in soils

Polyaromatic Hydrocarbons (PAHs) have been determined in soil samples for many years. PAHs can arise in the environment from natural sources, oil and petroleum products and combustion processes. Although oil spills influence PAHS concentrations in local areas, the major sources of PAHS are anthropogenic and derived from land based combustion sources. PAHs are globally distributed and the highest concentrations generally occur close to urban centres. Monitoring is essential during the assessment and remediation. It makes further demands on the analytical methods used, since the transformation products are often present in lower concentrations than the parent PAHs and they may be difficult to identify in the complex mixtures found in these samples. It is therefore essential to use powerful analytical tools to fractionate, separate and identify the analyses in the samples. In this paper we review those aspects relating to the analysis and monitoring of PAHs in soils. The aim is to provide an overview of current knowledge, so as to assess the need for future monitoring of PAHs and the present capability for their analysis. Further monitoring of PAHs is justified because of their ubiquity in the environment, their persistence and bioaccumulative properties and their potential for toxicity both to aquatic organisms and human consumers.     

Shallow-water loading tides in Japan from superconducting gravimetry

Gravity observations from superconducting gravimeters are used to observe loading effects from shallow-water tides on the Japanese east and west coasts. Non-linear third-diurnal and higher-frequency shallow-water tides are identified in the tide-gauge observations from these coastal areas. The most energetic constituents in the tide gauge observations are also seen in the gravity observations due to their loading effects on the deformation of the Earth. Even though the shallow-water tides at the Japanese east coast have an amplitude of only a few millimetres, they are still able to generate a loading signal at gravity sites located several hundred kilometres inland. In particular, the S₃, S₄ and S₅ solar tides occur in both gravity and tide gauge observations. It is indicated that in other shelf regions with large shallow water tides, the shallow water loading signals account for a significant signal, which should be taken into account.Acknowledgement The authors would like to thank the Hydrographic and Oceanographic Department (Japan Coast Guard), Japan Meteorological Agency and Hokkaido Development Agency for access to the tide-gauge data. Also, the Global Geodynamic Project Information System and Data Center (GGP-ISDC) is acknowledged for providing the gravity data.     

Focal mechanism study of north Potwar dformed zone, Pakistan

Introduction Northern Pakistan is one of the seismically active regions in the world. Numerous studies have been undertaken to highlight and understand the ongoing collisional process of the Indo-Pakistan plate with the Kohistan island arc. Besides the N-S compression, as a result of the con-vergence, transpressional features have also been recognized. However, in the studied area pres-ence of evaporites (Eocambrian) has led to the development of duplex type models with the basal decollemen…     

Analysis of the distribution coefficients and mobility characteristics of phenols in different soil types

Adsorption studies were carried out on soil samples of high organic and low organic content to analyze the distribution coefficient and mobility of phenols. The results show that the amount of phenols adsorbed by the soil varies linearly with the fraction of organic carbon. Soils that are highly organic compared to those with low organic matter content retain the phenols to a greater extent. Adsorption studies on the different soil types indicated that the extent of adsorption of phenols by different kinds of soils is important, as a smaller amount of adsorption by the soil increases the risk of contamination of the groundwater supply.