When evaluating the seismic resistance of tunnels while considering the resistance of shotcrete, it is necessary to appropriately consider not only the mechanical properties of shotcrete after hardening but also the effects of the deformation of the ground during excavation. In addition, a quantitative evaluation of the variation is necessary to obtain the characteristic values of materials used in seismic design. In this study, some loading tests were conducted using cylindrical specimens of shotcrete from early age to hardened state, with the aim of obtaining data that will contribute to the seismic evaluation of unlined tunnels. As a result, a set of data was obtained not only on uniaxial compressive strength, but also on splitting tensile strength and hysteresis characteristics, for which there is very little existing data. The average compressive strength of the shotcrete at 28 days was 32.1 MPa, and the characteristic value was evaluated to be 25.8 MPa when the probability of non-exceedance was set at 5%. In addition, it was confirmed that shotcrete made by the dry type spraying method has lower stiffness than the one which is obtained by the previous test using wet methods. Furthermore, the factors behind the decrease in strength and stiffness were analyzed from CT images and mixture estimation results.

 In this study, with the aim of establishing a design methodology that can appropriately evaluate the effect of inner reinforcement work, such as improving the load-bearing capacity of the whole tunnel lining structure, a new analysis method was developed that couples the damaged lining modeled with individual granular elements and the inner reinforcement modeled with shell elements using the finite difference method, which is a continuum analysis method, and its applicability was verified. A full-scale lining specimen that had suffered bending compression failure was subjected to a reload experiment in which it was reloaded without reinforcement and with carbon fiber sheets applied as inner reinforcement work. This confirmed the usefulness of this analysis method in evaluating the effect of inner reinforcement work on damaged tunnel linings, such as cracks in the lining concrete, structural separation such as floating and peeling, and peeling of the sheets, and improving the load-bearing capacity of the entire lining structure, and also clarified issues regarding its applicability.

 In the long-term durability of shield tunnels, it is important to prevent water leakage from the ground, which is a major cause of deterioration of segments and internal structures of the tunnel. However, reports of water leakage due to the deterioration of segments in service suggest that the current leakage prevention measures are inadequate for achieving long-term durability. Therefore, we studied a waterproof coating for the back of the segment aimed at enhancing long-term durability and replication test for tail-brush scratches replicated under actual application condition. In the replication test, we considered it is important to evaluate the pressure effect of fluid materials such as tail sealers filled back of the tail-brush. It was confirmed that highly flexible waterproof coatings, primarily composed of acrylic rubber, form both linear shallow scratches and deep scratches. The developed coating, which maintained flexibility while reducing the kinetic coefficient of friction (COF), was able to suppress deep scratches. This is believed to be because the flexible coating minimized damage by avoiding the load from the tail-brush.

 As for seismic analysis methods for tunnel cross-section, the seismic-deformation-method (SDM) and the FEM dynamic analysis (FDA) are both effective, but the latter is becoming mainstream in recent years due to great advances in the numerical calculation environment. This paper aims to provide a deeper understanding and materials that will contribute to a comprehensive discussion of the SDM, which is in a period of transition. Four points that have not been sufficiently verified so far are discussed through precise comparisons with calculations using the FDM: the tunnel modeling method, the significance of considering the inertia force, the effect of neglecting damping, and the ground spring. In conclusion, the correctness of the calculation principle of the SDM is confirmed, the relationship between the seismic loads considered in the method is clarified, the reality of ground springs is revealed, and the system of factors that cause calculation errors in comparison with the FDA is presented.