Abstract
One of the key issues in protective seam mining is the pressure relief and permeability improvement effect. In this paper, the results of X-ray CT scanning experiments and permeability experiments using reconstituted coal specimens subjected to the same stress path and the same effective confining pressure (confining pressure minus pore pressure) are combined using the stress–strain relationship to study the damage to reconstituted coal specimens and its influence on permeability during the unloading process. When the effective confining pressure (σ3 − p) is unloaded from 8 to 6 MPa and the deviatoric stress increases, the damage variables will increase by 0.0351 and 0.084, respectively, compared with the unloading point under the fixed axial displacement with unloading confining pressure (FADUCP) and fixed deviatoric stress with unloading confining pressure (FDSUCP) stress paths. At the same time, the permeability increased by 1.7 and 16.7 %, respectively. Therefore, the damage variable and permeability increased notably little in this process. After the effective confining pressure is unloaded to approximately 5 MPa, together with the decrease in the deviatoric stress, the growth of the damage variable and permeability begins to accelerate. In addition, the relative decrease in the deviatoric stress with appearing damage cracks, and the relative increase in permeability with the same amount of effective confining pressure being unloaded, shows that the damage to specimens under the FDSUCP stress path is larger than that from the FADUCP stress path.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.