Characterization of weathered acidic volcanic rocks and a weathering classification based on a rating system

It is important to recognize the effect of weathering in the performance of rock in engineering works. The aim of this study was to determine the weathering characteristics of acidic volcanic rocks from northwest Turkey and their effects on some engineering properties of the rocks. A series of simple and multiple regression and factor analyses suggested that porosity, indirect tensile strength, block punch strength and P wave velocity were the most suitable parameters for a quantitative estimation of weathering grades for engineering purposes. A weathering classification system for the acidic volcanic rock materials was developed based on rating these four engineering parameters. In addition, a weathering classification system based on visual descriptions and Schmidt hammer rebound values is also suggested for the rock masses studied.RésuméIl est important de bien définir l’état d’altération des roches pour les travaux de génie civil. Le but de cette étude est de caractériser l’état d’altération de roches volcaniques acides du nord-ouest de la Turquie et d’analyser l’effet de cette altération sur les propriétés géotechniques de ces roches. Un ensemble d’études de corrélations et d’analyses factorielles des correspondances a montré que la porosité, la résistance à la traction, la résistance à l’impact et la vitesse des ondes P représentaient les paramètres les plus appropriés pour caractériser différents états d’altération de ces roches. Un système de classification de l’état d’altération pour des roches volcaniques acides a été mis au point sur cette base. De plus, des descriptions de terrain et l’indice de rebond au marteau de Schmidt sont utilisés pour caractériser l’état d’altération du massif rocheux.

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