Experimental and modelled mechanical behaviour of a rock fracture under normal stress |
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| Authors: | A Marache J Riss S Gentier |
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| Institution: | (1) Université Bordeaux 1, GHYMAC, Av. des Facultés, Talence Cedex, France;(2) BRGM, Orléans Cedex, France |
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| Abstract: | Summary The mechanical and hydromechanical behaviour of isolated rock joints is of prime importance for a correct understanding of
the behaviour of jointed rock masses. This paper focuses on the mechanical behaviour of a fracture under normal stress (fracture
closure), using approaches based on both experimentation and modelled analysis. Experimental closure tests were carried out
by positioning four displacement transducers around a fracture, leading to results which tended to vary as a function of transducer
location. Such variations can be explained by the non-constant void space distribution between both walls of the fracture.
The present study focuses on the importance of transducer location in such a test, and on the significant role played, in
terms of mechanical response, by the morphology of the fracture surfaces.
An analytical mechanical model is then developed, which takes into account the deformation of surface asperities and of the
bulk material surrounding the fracture; it also includes the effects of mechanical interaction between contact points. The
model is validated by simulating the behaviour which is very similar to experimental observations. Various parametric studies
(scale effect, spatial distribution of contact points) are then carried out. The study of scale effects reveals a decrease
in the normal stiffness with increasing fracture size. Finally, analysis of the role of various mechanical parameters has
shown that the most influential of these is Young’s modulus corresponding to the bulk material surrounding the joint. Many
applications, such as geothermal fluid recovery from fractures, could benefit from these results.
Correspondence: Antoine Marache, Université Bordeaux 1, GHYMAC, Av. des Facultés, 33405 Talence Cedex, France |
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| Keywords: | : Fracture mechanical behaviour normal stress experimental device roughness analytical model parametric study |
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