Abstract
This article summarizes the paper receiving the frontier award from the Japanese Society for Rock Mechanics (JSRM) in the fiscal year of 2014. Seafloor hydrothermal deposits have been found to be widespread in the waters off Okinawa Island. To assist with the design and manufacture of mining and crushing machinery and ore transportation equipment, this study investigated the mechanical properties of these seafloor hydrothermal deposits. Tests were carried out on the strength, hardness, and abrasiveness of boring cores and block samples of the deposits. In a uniaxial compression test, in which a specimen was crushed to 20% of its initial height, the size of the debris was slightly smaller than tuff, andesite, and sandstone. The specific energy calculated from the boring data was found to be closely related to the mechanical properties of the hydrothermal deposits, and its distribution beneath the seafloor was determined from boring data. The results obtained in this study provide important guidelines for the future development of mining techniques for seafloor hydrothermal deposits.
