The paper focuses on a description of geometrical parameters of jointing mainly gathered from the interpretation of trace maps from 2 small rock faces of Giurassic limestone, classic parameters (e.g. trace length, frequencies) and some joint pattern structure measures are statistically evaluated. A comparison is made between real and simulated maps form 2D & 3D models. The implication of modelling assumptions on simulated trace planes is pointed out.


Cet article donne une description des paramètres geometriques des champs de fractures au moyen de I'analyse des reseaux bidimensionnels des traces relevees sur deux petites parois de cal caire jurassique. On donne une estimation statistique de certains paramètres classiques (par exemple longeur des traces, frequences) et de certaines mesures de la structure du reseau des fractures. On donne aussi une comparaison entre les reseaux reel et des reseaux simulees en 2 et en 3 dimension et on remarque les implications des hypothèses de la modelisation sur les reseaux simules.


In diesem artikel ewrden die geometrischen parameter der bruchfelder durch die analyse von zweidimensionalen karten mit den auf Jura-Kalksteinwanden vermessen abdrucken beschrieben. Es werden einige klassische parameter (z. b. die lange der abdrucke, die frequenz) sowie einige Meβwerte, die typisch fuer das bruchfeld sind, statistisch geschatzt. Daruber hinaus wird auch ein vergleigh in 2D und 3D zwischen dem naturlichen und einem simulierten bruchfeld angestellt, und es werden die implikationen der modellierung gshypothesen auf dem simulierten bruchfeld betont.


Joints are an intrinsic characteristic of rock mass and appear at the various scales of the technical investigation. Therefore the behaviour of rock systems, subject to any physical disturbance, basically depends on the conditions of the many facets of this parameter. In any case the amount and the quality of the information gathered on rock joints is not homogeneous and must account for some particular aspects like: natural variability of the surveyed quantities, different forms of biases, data reliability and precision. The knowledge of the hidden structure of joint patterns can be pursued in at least three steps: 1) statistical characterization and estimation of basic indicators (mainly attitudes, trace lengths, apparent spacings or frequencies); 2) use of some form of inference toward set recognition, size or areal extension of joints, jointing intensity, measures of joint network structure; 3) reassembling, through conceptual models, a synthetic rock mass image that statistically reproduce the geometrical relations of the natural joint fabric. An impressive body of knowledge is available for the analysis, statistical inference and modelling of the geometrical aspects of natural jointing. A synthesis of the current trends (Cravero & Iabichino, 1992), though not complete, lists over 200 contributions, mainly on analysis procedures, and remarks at the same time the broadness and the degree of specialization required for the development of this general subject. In this paper, an example of characterization from trace maps, using statistical descriptors, is given using different procedures, also comparing sample statistics to those obtained from 2D and 3D simulated joint patterns. After some general remarks on the site and on the geology, results and comparison are given for a class of basic parameters: attitudes, joint length & size, and jointing intensity measures.


Geostructural data were gathered from two small adjoining rock surfaces in a limestone quarry for cement production. Limestone may be ascribed to Medium and Upper Giurassic. The stratigraphic sequence, with strata ranging from centimeters to meters has been intensely deformed and folded; therefore the resulting rock structure is fractured at a very high degree, with a fracture average length of only few centimeters (about 10 cm or less).

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