ABSTRACT

Durability tests and evaluation of sub-zero temperature effects to some argillaceous clastic rocks were carried out. Welded tuff, limestone, sandstone and schist samples collected from different parts of Japan were tested and results are presented. Schist and dolomite from Ganesh Himal area along the higher Himalayas of Nepal were also tested, and the results are compared. The slaking tests were performed on all samples in pure water. The results reveal that the slaking index of schist from Japan is lower than that of schist from Nepal. Regarding carbonate rocks, the slaking index of limestone from Japan is higher than that of dolomite from Nepal. A tendency of decrease in slake durability with an increase in porosity is also observed. Freezing and thawing experiments conducted on welded tuff and schist reveal that crack initiates earlier but extends slower in schist than in welded tuff. It is also observed from the freeze-thaw experiment that the welded tuff deteriorates and wears faster than the schist. However, sandstone remains relatively intact for a long run of freeze-thaw cycles.

Zusammenfassung

Bestandigkeitstests sowie die Bewertung der Auswirkungen von Minusgraden auf Tonschiefer Truemmergestein wurden durchgefuehrt. Dabei wurden geschweißter Tuff, Kalkstein, Sandstein und Schiefer aus verschiedenen Gebieten Japans sowie Schiefer und Dolomitgestein aus dem Ganesh Himal Gebiet, dem höheren Himalaya Nepals, untersucht und die Resultate verglichen. Fuer alle diese Gesteine wurden Slaking-Tests in reinem Wasser vorgenommen. Die Resultate zeigen, dass das Slaking von Schiefer aus Japan höher als das von Schiefer aus Nepal war, wohingegen bei kalkhaltigem Gestein das Slaking von Kalkstein aus Japan niedriger als das von Dolomitgestein aus Nepal ausfiel. Es wurde dabei auch eine Tendenz zur Löschbestandigkeitsverringerung bei gleichzeitig erhöhter Porositat beobachtet. Gefrier- und Tautests an geschweißtem Tuff und japanischem Schiefer zeigten, dass Risse in Schiefer schneller auftraten, aber sich langsamer ausweiteten als in geschweißtem Tuff. Bei Gefrier- und Tautests wurde ebenfalls beobachtet, dass geschweißter Tuff schneller verfallt und verschleißt als Schiefer. Sandstein hingegen blieb ueber lange Tau- und Gefrierzyklen intact

Resume

Des tests de solidites et l'evaluation de l'effet des temperatures en dessous de zero sur les rocs argileux ont ete effectues. Les rocs d'origine volcanique (cendre), les rocs calcaires, sableux et les schistes de differentes regions du Japon, ont ete etudies. Les schistes et les dolomites de la region de Ganesh Himal le long du haut Himalaya (Nepal) ont ete etudies et compares à ceux du Japon. Les tests de desintegration sur les rocs ont ete effectues dans l'eau pure. Les resultats montrent que l'index de desintegration des schistes du Japon est inferieur aux schistes du Nepal. En ce qui concerne les rocs carbonyles, l'index de desintegration des rocs calcaires du Japon est superieur à ceux des dolomites du Nepal. Une decroissance de la resistance à la durabilite est observee avec une plus grande porosite des rocs. Les tests de congelation-decongelation sur les schistes et les rocs d'origine volcanique (cendre) du Japon montrent une apparition precoce des fissures mais l'expansion des fissures est plus rapide dans les rocs volcaniques. Des tests similaires montrent que les rocs volcaniques (cendre) se desagregent plus rapidement que les schistes. Cependant, les rocs sableux restent intacts après plusieurs cycles de congelation-decongelation.

Introduction

Durability is an important rock characteristic controlling the stability of natural and artificial slopes (Dick and Shakoor, 1995:121). The slaking behaviour of a rock is a crucial factor that plays a major role in its failure (Dhakal et al., 2002: 32). Likewise, freezing and thawing has enormous effect on the strength of a rock if it undergoes cycles of freezing during winter and thawing during spring. Many geoenvironmental problems such as slope failures, slope deterioration, ground subsidence etc. are associated with the natural processes of ground freezing and thawing (Yamabe and Neaupane, 2001:1029). The cyclic freezing and thawing test simulates environmental loading/unloading conditions similar to these processes.

Despite having much works and literatures, the durability characteristics and the effects of sub-zero temperature to different rocks, particularly those subjected to the freeze-thaw cycles are not available in detail. Therefore, a comprehensive examination of different rocks under subzero temperature condition, including its effects on the durability is essential. Under these circumstances, an investigation regarding the slake durability and the cyclic effect of temperature variation were carried out to some argillaceous clastic rocks.

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