This paper describes a new rock mass classification system for superficial geotechnical works extended over large scale areas. Certain criteria (factors), are selected from various data Concerning rock mass so as to be possible to group the more representative rock's qualitative characteristics. In relation to the above factors, groups of data form the limits creating the three classes (A, B, C) of the new system.
Cet extrait decrit un nouveau system de classification des roches, pour des traveaux geotechniques superficiels, etendus sur une region a grandes dimentions. Quelques criteres (facteurs) Sont selectionnes des elements varies, concernant les roches, pour grouper les caracteristiques qualitatifs, les plus representatifs. Des groups de ces elements, a la relation aux facteurs au-dessus, forment des limites constituant les trois classes (A,B,C) de nouveau system.
ln der vorliegenden Arbeit wird anhand von Beobachtungen an Felsen in grossraumiger Ausbreitung versucht, ein neues Klassifizierungs - System der Felsen festzulegen. Von den bisher gesammelten Daten sind einige Kriterien herausgestellt, nach denen die typischen und qualitativen Eigenschaften der Felsen eingeordnet werden. Nach den herausgestellten Merkmalen und in Bezug auf die festgelegten Kriterien lassen sich die Felsen in drei Kategorien (A, B, C) einreihen.
The study for the construction of housing and industrial estates, road networks (national or regional) with high and abrupt slopes, quarries of marbles and other construction materials, etc., in the region of Atalanti (central Greece), asked for a comprehensive investigation study of the rock formations, over an area of almost 55.0 km2. This area, which in the past suffered of an intense seismic activity that caused damages and losses of human lives, is today the centre of multi - directional activities, which for their technical and economic planning require geotechnical information in relatively short time. Under these circumstances there was a need to classify the rock masses of Atalanti region in such a way as to get simply and fast the answers to the posed questions. An other contributing point concerning the derivation of the new system, was the fact that the existing classification systems cover, in general, the work requirements in their own scale, while in the case of Atalanti the interest is among works of great length or surface such as roads, gas or water pipe - lines etc., where different rock formations are involved. The regional rock formations, in order to be more systematically studied, are distinguished into four (4) groups based on their geotechnical origin (sedimentary, volcanic, etc.), their geological time and mode of deposition and their lithological composition (Fig. 1).
The data and information of rock formations were obtained from in situ measurements, observations and participation in the different phases of certain works, as well as from laboratory tests on rock samples. The main aim was the selection, on a qualitative basis, of the most representative system's factors, among a great number of data, information, observations and test results. The in situ measurements concerned: a) measurements of joints spacing, the results of which were classified after ISRM (1975) related classification, b)measurements of joints density per m3 of rock mass, for the estimation of Jv index. All measurements took place at selected and representative places having the main characteristics and appearance of the rock group under study.