New Data Processing Protocols to Isolate Fracture Deformations to Measure Normal and Shear Joint Stiffness

Autor: Timothy R. M. Packulak, Mariem T. Ahmed Labeid, Mark S. Diederichs, J. J. Day
Rok vydání: 2021
Předmět:
Zdroj: Rock Mechanics and Rock Engineering. 55:2631-2650
ISSN: 1434-453X
0723-2632
DOI: 10.1007/s00603-021-02632-7
Popis: The importance of discontinuity geomechanical properties is increasing as the use of numerical models with explicit or discrete rock mass structure becomes the state of practice. Joint normal stiffness and joint shear stiffness are two parameters that characterize the deformation behaviour of discontinuities. This paper presents practical guidelines to correct direct shear testing data for machine influences with regard to normal and shear joint stiffness using a method originally employed by Goodman (Methods of geological engineering in discontinuous rocks. West Publishing Company, St. Paul, 1976) to correct the normal deformation of a direct shear test. This method of correcting the normal deformation has been extended to the shear deformation to account for machine influence during the shear loading stage. The normal stiffness of 23 rough fracture specimens and 10 smooth ground specimens were measured on discontinuities in granitic specimens from NQ and NQ3 sized core using a power law (Swan in Rock Mech Rock Eng 16:19–38, 1983), a hyperbolic law (Bandis et al. in Int J Rock Mech Min Sci Geomech Abstr 20:249–268, 1983), and two semi-logarithmic laws (Bandis et al. 1983; Evans et al. in Geotherm Resour Counc Davis Calif USA 16:449–456, 1992). Measurements from direct shear tests completed at varying maximum applied normal stress show a positive correlation between normal stiffness and normal stress. In addition, the shear stiffness was measured on 19 rough fracture specimens and 4 smooth ground specimens. The compilation of results from these measurements has a range of measured shear stiffness due to varying joint topology and roughness showed a positive correlation between shear stiffness and maximum applied normal stress. As the majority of the joints exhibited non-linear behaviour under normal loading conditions and linear behaviour under shear loading conditions, it is recommended that a stress-dependent normal stiffness model and a linear shear stiffness model be used for numerical modelling purposes.
Databáze: OpenAIRE
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