FracturationInRockMass

Published: 26 March 2021| Version 2 | DOI: 10.17632/7rxhndg2fz.2
Contributors:
Muriel Gasc-Barbier,
Didier Virely,
Veronique Merrien-Soukatchoff

Description

These data were collected before excavating a high cutting in a migmatitic rock for the creation of a bypass in the French Pyrenees (Gasc-Barbier et al., 2008). They can be used to understand the fracturation of the rock mass or to test design methods. Location: Ax-les-Thermes lies 130 km south of Toulouse, just 30 km from the border between France and Andorra, in the primary axial zone of the French Pyrenees. Three orogenic phases that affected the entire mountain lead to considerable fracturing of the site, which is apparent in different forms depending on the area studied. Geological information: The bypass encounters Quaternary superficial formations, fluvioglacial materials, and then the rock substratum, where the benchmark takes place. The slope understudy is mainly composed of Augen gneiss and leptinic gneiss, in practice it is impossible to separate them into two distinct areas and hence the formation is best described as migmatite (in the widest sense). All these rocks are heavily fractured Scanlines (scanlines.xls): For several reasons, excavation was stopped when the proposed 42 m high cutting was 15 m high. This provided an opportunity to realize scanlines on the new cuttings to obtain statistical information on the joint properties “in” the rock mass. A scanline is a horizontal line (of about 10 m) drawn on a rock face. The scanline should have spatial references (dip and dip direction if possible). The standard properties of all the joints that intersect the line are mapped: dip, dip direction, spacing, trace length, weathering, aperture, infill, and roughness. Several lines in different directions were drawn in order to try to intersect the maximum number of joint sets. In this particular case and because of the geometry of the site, the scanlines were drawn on three faces as depicted in scanline_location.png but their lengths were quite different. 11 horizontal scanlines (from 6 to 30 m) were plotted including 856 discontinuities over 181.5 m (scanlines.xls). Borehole images: Two boreholes (SC43.pdf and SP47.pdf) were inspected by camera. borehole.xlxs summarizes the data Mechanical data, elastic waves velocities, uniaxial and Brazilian tests, and shear tests on natural joints are provided on labo_Ax.xls

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Institutions

CEREMA

Categories

Design Methods of Rock Mechanics, Jointed Rock

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