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Prediction of dilation and permeability changes in rock salt
Author(s) -
Stormont J. C.,
Daemen J. J. K.,
Desai C. S.
Publication year - 1992
Publication title -
international journal for numerical and analytical methods in geomechanics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.419
H-Index - 91
eISSN - 1096-9853
pISSN - 0363-9061
DOI - 10.1002/nag.1610160802
Subject(s) - geotechnical engineering , permeability (electromagnetism) , dilation (metric space) , geology , materials science , mathematics , chemistry , geometry , membrane , biochemistry
A numerical procedure has been developed for predicting dilation (porosity) and gas permeability changes in rock salt. The hierarchical single‐surface constitutive model of Desai and co‐workers is used a finite element program to calculate the state of stress and strain surrounding excavations in rock salt. The elastoplastic constitutive model accounts for strain hardening, a non‐associative volumetric response and stress‐path‐dependent behaviour. The calculated stress and strain fields are used in a flow model based on the equivalent channel concept to predict permeability. Parameters for both the mechanical and permeability models are developed from laboratory test results. Two field experiments adjacent to underground excavations are modelled. The extent of the dilated rock zone around the excavation is predicted well, but the magnitude of the porosity and gas permeability is underpredicted very near the excavations. This discrepancy is attributed to model parameters derived from loading‐only laboratory tests, whereas significant unloading occurs in the field. The shape of the yield surface was found to be an important factor in dilation and permeability predictions. Similar stress, strain and permeability fields were obtained with different model types (plane strain or axisymmetric) and initial stress states, and with instantaneous and progressive excavation.