Plain concrete with a design thickness of 30 cm and uniaxial compressive strength of 18 N/mm² is the standard lining for general sections of road tunnels of normal cross section constructed by the mountain tunneling method. However, the function and performance of the lining and its evaluation method are not fully established, which is an issue when introducing new technologies to the lining. This paper proposes an evaluation flow in terms of the load-bearing capacity of the lining, which consists of an evaluation method using the cross-sectional load-bearing capacity and an evaluation method using the load-bearing capacity of the entire structure. The applicability of the proposed flow was confirmed by evaluating the load-bearing capacity of a thin-walled high-strength lining as an example of a new lining technology. It was found that the use of the evaluation method based on the load-bearing capacity of the entire structure enables the evaluation of the load-bearing capacity of the lining in a more rational manner, taking into account the gradual destruction of the lining and the failure mode of the lining when it becomes unstable.

 2D trapdoor tests were conducted to simulate the deep ground displacement in sand layer in 50g centrifugal environment. The trapdoor width (B), and sand depth (H) are 3m, and 12m in prototype scales. The tests were conducted in medium dense (D_r=80%) and very dense sand (D_r=95%) assuming the relatively deep and relatively firm ground. Earth pressures and displacement in the ground were measured by small earth pressure cells and PIV. The ground resistances at various locations from the trapdoor center were also measured by cone penetrometer at small and large trapdoor movements, which correspond to small volume loss ratio by tail void closure as a common condition and extremely large volume loss by over-excavation as a condition of potential accident. From the tests, affected spatial area in terms of ground displacement and cone resistance were investigated and discussed. For the small volume loss, 20-30% reduction of the resistance from the intact condition was observed at the depth over the half of H at the tunnel centre, but the reduction occurred in the very limited horizontal location from the centre, less than 0.5B. For the large volume loss in deep tunnel excavation in sand, the effect of over excavation may appear at ground surface at smaller volume loss for the very dense ground than the medium dense sand due to the narrow loosening width. Although there are some differences in the effect of large over excavation on the penetration resistance depending on the sand density, the effects became very small at the horizontal location over 2.0B for this experimental conditions.

 The noncontact acoustic inspection method using acoustic irradiation induced vibration and laser Doppler vibrometer can remotely detect internal defects in concrete. However, fundamental verification experiments using shotcrete specimens have not been conducted for shotcrete, which has an uneven measurement surface. In this study, a shotcrete specimen was fabricated and a basic fundamental experiment using the noncontact acoustic inspection method was conducted. The experimental results show that defects can be detected in the same way as in the previous demonstration test conducted in the ceiling of a large underground cavern where an underground power plant is located.