When the center drift advanced method is applied, ‘dodging effect’, that is, the reduction of the amount of convergence and crown settlement at the time of widening excavation of the main tunnel, and reduction of the sectional force of support members, is often expected. However, the discussion regarding the influence on the mechanical behavior of the main tunnel has been limited.

 In this paper, the mechanical behavior of the Yoshinomoto tunnel with the center drift advanced method was considered with the in-situ measurement data and the result of numerical analysis, and it was found that the dodging effect cannot always be obtained under the extreme fragile ground conditions. Also, the design index of the center drift where the effect was shown was discussed through the analysis considering the size of the drift, the stiffness of the support, and the ground condition.

 Since the stress around the opening of a circular shaft is complicated, it is difficult to properly model it in 2D analysis, and a vertical 2D beam model that is designed for safety is used based on past experience and experience. Often. However, it is not economical compared to the 3D model, and its effect is considered to be large especially when the opening is large. On the other hand, FEM analysis using a 3D model is very complicated, and the design method is not systematized, and the evaluation is based on the designer’s judgment.

 Therefore, in this study, by using 3D FEM analysis, we investigated the effects of an opening and a rail beam on the circular deep shaft behavior around the opening. We propose a rational 2D modeling method for the sidewall of the opening considering the 3D effect.

 It is important to attain hydraulic barrier performance in chemical grouting. A new approach to detect the end point of the channel caused in improvement body by imperfect chemical grouting was proposed. Salt water as tracer is infiltrated through the channel and the diffusion from the end is monitored by electrical resistivity tomography in this approach. The resistivity of measurement area is continuously changing, so the monitoring may be difficult using conventional inversion analysis method that assumes resistivity is stable. Therefore, the time-lapse analysis method is used. The time-lapse analysis method is particularly effective for the monitoring of tracer, because it is characterized by being able to handle a continuous change of the electrical resistivity distribution during measurement. As a result of an outdoor tank experiment for the verification of effectiveness of the proposed approach, decrease of electrical resistivity has been clearly detected around the end of the channel and the position of the end has been detected by use of the time-lapse analysis method. Furthermore, the validity of the experiment result has been confirmed from the advection-dispersion analysis performed for the reappearance of the experiment.

 This research was conducted by TEPCO Power Grid, Inc. to study the reinforcement of shield tunnels with reduced load resistance capacity. For reinforcement, it was decided to apply the buried formwork method considering the workability in the tunnel, and the characteristics of load resistance capacity for reinforcement and its calculation method were examined by the load test of the test pieces that reproduced the reinforcing member. As a result of the test, the bending strength was equal to or higher than the calculation result by considering the thickness of the buried formwork. Regarding shear strength, shearing crack did not progress due to the buried formwork, and it was difficult for shear fracture to occur. However there were cases in which shear fracture occurred, it was evaluated that the shear strength needs to consider the thickness of the buried form as well as the bending strength. Based on the examination results, the calculation method of load resistance capacity of the reinforcing member was shown.

 In recent years, deterioration such as rebar corrosion has been reported in shield tunnels for power transmission owned by TEPCO Power Grid, Inc. In this case, there are many cases of repair by the cross-section repair method in order to suppress the progress of deterioration and restore durability. However, there are few past research cases of the cross-section restoration method for the segment, and there were unclear parts about the effect on load resistance capacity. Therefore, they were examined by a loading test on the specimens whose cross-section were repaired by reproducing the segment. As a result of the test, there was a tendency for changes in the behavior of cracks and destruction situations, but no deterioration in load resistance capacity was observed due to cross-section repair method. Therefore, it was decided to calculate and check the bending strength and shear strength of the segment when the cross-section is repaired, as in the case where the cross-section is not repaired.

 Taking the case of an existing shield tunnel for power transmission where the deformation of the tunnel was caused by the unexpected load fluctuation, the comparison of the load bearing performance by the allowable stress design method and the limit state design method was conducted. As a result of the existing structure, the allowable stress design method satisfied the load bearing performance, but the limit state design method could not satisfy the load bearing performance and required an increase in the amount of reinforcing bars. Since the tunnel under consideration required large-scale reinforcement, it was shown that the design by the limit state design method is an effective design method against unexpected fluctuations.

 The widening works of the existing railway cut-and-cover tunnel are increasing as increasing the mutual direct operation. In this case, the length of side-wall removing of the tunnels tends to be longer. Therefore, there is a possibility that the tunnels designed on the assumption of the 2-dimensional behavior behave 3-dimensionally. In this paper, first, 3-dimensional step analysis based on finite element method is applied to the simulation of the widening works using hanging protection. Next, 2-dimensional analysis method based on beam-spring analysis is developed and considered in comparison with the field data.