Influence of anisotropy on the mechanical properties of Baixo Alentejo Flysch Rocks (Portugal)

António B. Pinho, I. M.R. Duarte, F. R.S. Rosa, J. A. Rodrigues-Carvalho

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Citation (Scopus)


This paper aims to contribute to the knowledge of the mechanical properties of the shales and greywackes which constitute the flysch-type deposits of the Baixo Alentejo Flysch Group, in the south of Portugal. These formations are flysch-type deposits constituted by sequences of usually thick greywacke beds alternating with thin shale beds, which include sometimes intercalations of conglomerate beds. All the sedimentation of these flysch formations was controlled by tectonics. At the same time, should have occurred along with the first Hercynian deformation phase, a low-grade metamorphic event (chlorite zone), that affected these flysch deposits. This study highlights the influence of anisotropy and heterogeneity of these flysch rocks on their physical and mechanical characteristics. The anisotropy verified in some physical properties and on mechanical properties, due to the foliation makes difficult the sample preparation for the laboratory tests. Besides, it induces a scattering of the properties values measured, as for example, the strength and the deformability. The heterogeneity is related to the main features of these geological formations, which are constituted mostly by thinly stratified greywackes and shale beds, which sometimes may affect the results of the laboratory tests making them less representative. The study is made by using both shales and greywackes that constitute these flysch-type deposits in order to evaluate their geotechnical properties, mainly of the shales. Samples of these two rock materials, are tested accordingly a laboratory testing programme, which includes which included mineralogical analysis (X-ray diffraction), physical tests (bulk density, porosity, and void index) and mechanical tests (uniaxial compression, and deformability tests).

Original languageEnglish
Title of host publication13th ISRM International Congress of Rock Mechanics
Editors Hassani, Hadjigeorgiou, Archibald
PublisherInternational Society for Rock Mechanics
Number of pages10
Volume2015- MAY
ISBN (Electronic)9781926872254
Publication statusPublished - 1 Jan 2015
Event13th ISRM International Congress of Rock Mechanics 2015 - Montreal, Canada
Duration: 10 May 201513 May 2015


Conference13th ISRM International Congress of Rock Mechanics 2015


  • Anisotropy
  • Baixo Alentejo Flysch
  • Flysch rocks
  • Greywackes
  • Mechanical properties
  • Shales


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