The late-Hercynian granites of Königshain underwent multistage hydrothermal processes. Extensive high-temperature late-magmatic alteration is, for example, indicated by low Zr/Hf and an REE pattern displaying the tetrad effect. Intensive post-magmatic alteration of the granite occurred along brittle structures. At least two main stages of post-magmatic hydrothermal alteration are involved. The first high-temperature stage, which is characterized by albitization and/or quartz leaching (episyenitization), resulted from fluid-rock interaction with late-magmatic fluids that very probably mixed with external low-salinity fluids. Quartz dissolution was triggered by vapour condensation and/or the cooling of these fluids (below 450 7C) along brittle structures. The high porosity resulting from quartz leaching during stage 1 assisted subsequent circulation of low-temperature fluids at stage 2; the latter is characterized by the chloritization and illitization of episyenites. Almost all major and trace elements were enriched or depleted during one of the main alteration stages. However, Zr, Hf, Th, and Ti were immobile during post-magmatic alteration. The significant depletion of LREE and the enrichment of HREE in albitized samples is controlled by the dissolution of monazite and the new formation of HREE-rich polycrase-(Y) or aeschynite-(Y) during post-magmatic stage 1. Negative Ce anomalies of episyenites are associated with illitization and suggest oxidizing conditions during stage 2.
Wear to the tools used for excavate the rock mass has a significant relevance for the cost and performance of tunnel drives in hard rock. This applies in particular to mechanised tunnelling processes, where the effect of wear is an important factor for system availability. At the moment, laboratory tests and derived abrasiveness indices like the Cerchar Abrasiveness Index (CAI) or the Rock Abrasivity Index (RAI) provide the basis for evaluation of tool wear. It should however be noted that such index values can only take into account influential factors on the scale of the intact rock. Influential factors on the scale of the rock mass, for example mixed‐face conditions, unstable face conditions, blockiness or the primary and secondary stress states at the face, can also be significant for the tool wear that is actually experienced. The possible consequences of such disadvantageous effects, which for example can cause catastrophic failure of tools, can represent many times the abrasiveness of the intact rock.
Der Arbeitskreis AK 3.3 „Versuchstechnik Fels“ der Deutschen Gesellschaft für Geotechnik e. V. (DGGT) erarbeitet Empfehlungen für felsmechanische Labor‐ und Feldversuche sowie Messungen im Gebirge und an geotechnischen Bauwerken. Die vorliegende Empfehlung Nr. 25 behandelt die Bestimmung von mineralogisch‐petrographischen Kennwerten an Festgesteinsproben zum Zwecke der Abrasivitätsbewertung. Es werden Anforderungen an Prüfeinrichtungen und Probekörper sowie Vorgehensweisen für die Durchführung und Auswertung von Dünnschliff‐ und Pulverröntgendiffraktometeranalysen sowie für die Ableitung verschiedener Indexwerte zur Abrasivitätsbewertung festgelegt.
Bei der petrographischen Analyse werden Informationen über Art und Anteile des Mineralinhalts sowie Gefügeeigenschaften eines Gesteins erhoben. Diese Informationen können entweder direkt, z. B. als Quarzgehalt, oder in Form abgeleiteter Indexwerte, z. B. Äquivalenter Quarzgehalt, Schimazek‐Verschleißindex oder Rock Abrasivity Index, zur Charakterisierung der Abrasivität herangezogen werden. In dieser Empfehlung werden der Zweck, die Begriffe, die Prüfeinrichtung, die Anforderungen an den Probekörper und die Versuchsdurchführung und ‐auswertung behandelt.
The growing economic pressure on tunnelling and mining operations has lead to an increasing importance of investigation methods for assessing the abrasiveness of rock and soil. Such investigations can be based on a wide variety of testing procedures and standards covering a wide span of scale, ranging from real-scale tests on site to model tests with simplified tools and microscopic and chemical analyses of rocks and minerals. This paper gives an overview over some of the most important procedures, technical aspects of their application, classification of testing results and the current state of experience.
Abrasivitätstest, quo vadis? Ein kommentierter Überblick über Abrasivitäts-Testverfahren
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.