Abstract
This study experimentally investigated the self-healing behavior, referring to the naturally occurring water permeability decrease, of fractured rocks exposed to water-CO2-rock interaction (WCRI). The experiment was conducted on prefractured specimens of three rock types typical of the Shendong coalfield: coarse-grained sandrock, fine-grained sandrock, and sandy mudrock. During the experiment, which ran for nearly 15 months, all three specimens exhibited decreasing permeabilities. The coarse- and fine-grained sandrock specimens exhibited smooth decreases in permeability, with approximately parallel permeability time curves, whereas that of the sandy mudrock specimen decreased rapidly during the initial stage and slowly during later stages. The sandrock specimens were rich in feldspars, which were dissolved and/or corroded and involved in ionic exchange reactions with CO2 and groundwater, thereby generating secondary minerals (such as kaolinite, quartz, and sericite) or CaSO4 sediments. These derivative matters adhered to the fracture surface, thereby gradually repairing fractures and decreasing the water permeability of the fractured rocks. In comparison, the sandy mudrock had a high content of clay minerals, and the water-rock interaction caused rapid expansions of illite, mixed illite-smectite, and other clay minerals, thereby narrowing the fractures and causing the rapid permeability decrease during the initial stage. In later stages, the derivative matters generated by the dissolution and/or corrosion of feldspars and other aluminum silicate minerals in the mudrock filled and sealed the fractures, causing the slow permeability decreases during the later stages, as in the sandrock specimens. Neutral and basic groundwater conditions facilitated better self-healing of fractured mudrocks rich in clay minerals, whereas acidic groundwater conditions and the presence of CO2 facilitated better self-healing of fractured sandrocks. Thus, this study’s results are of significant value to aquifer restoration efforts in the Shendong coalfield and other ecologically vulnerable mining areas.
Highlights
The Shendong coalfield is located in the Maowusu Desert, West China, which has an arid or semiarid climate, vulnerable ecology and environment, and scarce water resources
Manual irrigation is usually necessary to satisfy the water requirements of ground vegetation, and ecological restoration of mining-damaged aquifers is another water-conservation approach that is urgently needed for such mining areas
The permeability curves of the coarse-grained sandrock specimen and the fine-grained sandrock specimen were similar: the permeability of the former decreased from 3:27 × 10−11 m2 at the beginning of the experiment to 1:26 × 10−11 m2 at the end, with an average decrease of 4:5 × 10−14 m2/day, whereas that of the latter decreased from 2:40 × 10−11 m2 to 6:65 × 10−12 m2, with a slightly lower average decrease of 3:9 × 10−14 m2/day
Summary
The Shendong coalfield is located in the Maowusu Desert, West China, which has an arid or semiarid climate, vulnerable ecology and environment, and scarce water resources. The technology has been applied in 15 mines in the Shendong coalfield and has effectively alleviated water consumption issues in this mining area [7,8,9,10] This technology transfers and stores water by draining groundwater accessed in the mining process to a stope for conservation. This technology alters the original groundwater network and, if water-conducting fractures are connected with loose surface layers, may even induce the release of near-surface water In this situation, manual irrigation is usually necessary to satisfy the water requirements of ground vegetation, and ecological restoration of mining-damaged aquifers is another water-conservation approach that is urgently needed for such mining areas
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: 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.
