Application of Cement-based Sealants for Prevention and Remediation of Environmental Impact of Submarine Resource Mining

摘要

Recurrent studies on submarine hydrothermal deposits have been directed toward the practical mine development and the corresponding environmental impacts. Even after the extraction of submarine resources, the original environment shall be maintained in order to prevent harmful effects on the marine ecosystem. Nonetheless, relatively little research about mineral exploitation on the seafloor has been focused on how to prevent its environmental disturbances and rehabilitate the mining site. Authors invented an environment-friendly underwater mining method that aims to control the dispersion of seabed surface sediments and fill the extracted areas by sealing a submerged mine site with an anti-washout cement-based material. This work investigates technological properties and environmental impacts of sealants with different cementitious binders and anti-washout agents on a laboratory scale. Using the remotely operated vehicle Hyper-Dolphin, field trials were conducted in the marine submerged Wakamiko crater. The results indicate that a sealant with particular types of cement and anti-washout agent showed superior anti-washout, filling and hardening properties under submarine hydrothermal conditions. Less dispersion of surface sediments was observed after covering the seafloor surface with the sealant during the field-scale experimental exploitation. Sealants had less negative effects on the seafloor ecosystem.