[en] The Mizunami Underground Research Laboratory (MIU) of the Japan Atomic Energy Agency is a major site for geoscientific research to advance the scientific and technological basis for geological disposal of high-level radioactive waste in crystalline rock. Studies on relevant engineering technologies in the MIU consist of a) research on design and construction technology for very deep underground applications, and b) research on engineering technology as a basis of geological disposal. In the Second Phase of the MIU project (the construction phase), engineering studies have focused on research into design and construction technologies for deep underground. The main subjects in the study of very deep underground structures consist of the following: 'Demonstration of the design methodology', 'Demonstration of existing and supplementary excavation methods', 'Demonstration of countermeasures during excavation' and 'Demonstration of safe construction'. In the FY 2007 studies, identification and evaluation of the subjects for study of engineering technologies in the construction phase were carried out to optimize future research work. Specific studies included: validation of the existing design methodology based on data obtained during construction; validation of existing and supplementary rock excavation methods for very deep shafts; estimation of rock stability under high differential water pressures, methodology on long-term maintenance of underground excavations and risk management systems for construction of underground structures have been performed. Based on these studies, future research focused on the four subject areas, which are 'Demonstration of the design methodology', 'Demonstration of existing and supplementary excavation methods', 'Demonstration of countermeasures during excavation' and 'Demonstration of safe construction', has been identified. The design methodology in the first phase of the MIU Project (surface-based investigation phase) was verified to 200 m depth during shaft excavation. The concepts for the estimation of the influence of high differential water pressures, long-term maintenance and risk management with respect to the geological disposal project have been proposed. (author)