This part of the review concentrates on the papers dealing with laboratory testing but not directly related to the session theme. The review shows the areas of ongoing research. The papers accepted for publication are categorized and their contribution summarized. Some general conclusions are drawn, concerning laboratory testing, rock mass characterization and modeling.
Cette partie du rapport presente une analyse des contributions qui ne sont pas directement lies au sujet principal de la session. La revision montre les sujets de recherche en cours. On fait une classification des papiers publies et un resume de leur contribution. Les conclusions concernent les methodes d'essai au laboratoire et la caracterization et modelisation des massifs rocheux.
Dieseri Bericht bezieht sich auf die Veröffentlichungen die Labor-Pruefungen behandeln, jedoch nicht direkt mit den Themen de Sitzung verbunden sind, Der Bericht erwehnt die Gebiete in denen gegenwartig geforscht wird. Die zur Veröffentlichung angenommenen Arbeiten sind geordnet worden und Ihr Beitrag ist zusammengefasst worden. Einige allgemeine Schlussfolgerungen in bezug auf Labor-Pruefungen, Kennzeichnung von Felsmassen und ihre Modellierung werden dargestellt.
The general reporters have been asked to give a global view of the contents of the papers accepted in this session and to review the major trends in the theme. My co reporter, Professor Emmanuel Detournay, has covered those contributions directly related to the session theme. It is my duty, then, to review the other papers, many of them cover only partial aspects of the session theme or are loosely related to it. This part of the report will concentrate on compression testing, shear behavior will also be commented. The purpose of laboratory research is to learn about the behavior of rocks. We want to solve the problems that happen in the field. Consequently, the results must be representative of field behavior and they must be fed into a valid model if they are to be of any use. Hence, laboratory testing and modeling tend to go together. A review of the papers published since 1995 in journals and in the International Symposia of our Society' (including this Congress), was used as a guide to find out the areas of ongoing research and the actual trends on our subject.
Stiff testing machines have become very common in research laboratories to study the stress-strain behavior of rock samples. Wu et. al describe the development of a new computer controlled system to produce arbitrary load paths in the triaxial test. Other types of testing arrangements, such as the hollow cylinders tested by Nguyen Minh et al., are also used to study the behavior of rock under more truly triaxial stress conditions, including tensile stresses, or to simulate the loading conditions around a tunnel. The use of hollow cylinders allows obtaining truly triaxial stress states, but an elaborate sample preparation and mounting procedure are required. Also, the variation of stresses along the thickness of the sample may render the interpretation of the results more difficult than in the conventional triaxial tests. Direct measurements of tensile strength are not generally needed for routine projects. Direct measurement of tensile strength, as proposed by the ISRM, is usually difficult to perform and indirect measurement procedures exist. A new procedure of preparing the samples, proposed by Luong and Hoteit (1988) to study the fundamental fracture modes of granite, is shown schematically in Figure 1. Two concentric perforations, each drilled from opposites ends of the sample, leave an annular central section subjected to tensile stresses when the sample is loaded in compression. The procedure can be easily applied in engineering laboratories in order to obtain direct measurements of the tensile strength. It seems interesting to explore the use of the proposed method as a standard procedure.
