Open AccessHydrofracturing tests on granite samples using a true triaxial device equipped with acoustic emission sensors
Author(s) -
Miguel Herbón-Penabad,
Andrea MuñozIbáñez,
Jordi DelgadoMartín,
N. A. González-Molano,
José Alvarellos-Iglesias,
Jacobo Canal-Vila
Publication year - 2021
Publication title -
iop conference series. earth and environmental science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.179
H-Index - 26
eISSN - 1755-1307
pISSN - 1755-1315
DOI - 10.1088/1755-1315/833/1/012187
Subject(s) - strain gauge , acoustic emission , stress (linguistics) , materials science , hydrostatic pressure , displacement (psychology) , overburden pressure , hydrostatic equilibrium , hammer , hydraulic press , geotechnical engineering , composite material , geology , mechanics , engineering , metallurgy , mechanical engineering , physics , psychology , philosophy , linguistics , quantum mechanics , psychotherapist
We present a series of tests performed on granite samples using a true triaxial device designed and built at the Rock Mechanics Laboratory (University of A Coruña). The experiments were performed using cubic rock samples of 150 mm-edge, which were loaded to different stress conditions ( σh < σh < σy < 45 MPa) on each loading axis. The device is based on a stiff steel frame that can be coupled to a servo-hydraulic testing machine that provides de vertical stress (av), while two high-pressure pumps are used to deliver the lateral stress ( σh and ah ). An additional high-pressure pump is used to inject the fluid (mineral oil) into the rock sample at a low constant-flow rate. The aluminium loading platens, which are bevelled at the edges to avoid interaction among adjacent faces, have holes and grooves to introduce acoustic emission sensors that allow the location of fracture propagation. The specimens were drilled using a 6 mm drill bit until reaching the geometrical centre. Then, a 1/8” (~3.18 mm) stainless steel tube is glued to the samples with epoxy. Strain measurements during the experiments were conducted using four strain gages attached to the orthogonal faces of the specimens. The system was further equipped with three LVDTs to account for the bulk displacement on each axis. Our results suggest a linear relationship between the breakdown pressure and the confining stress under hydrostatic conditions but no clear correlation in non-hydrostatic stress regime.