Centrifugal model tests and three-dimensional elasto-plastic finite element analyses are conducted in order to clarify the effects of the ring-cut excavation method on the displacements of the ground and the stability of a tunnel face. In the experiments, the ground is excavated by an excavation robot, which is controlled by computer programs. The displacements and the stability of the tunnel faceare compared between such two methods as the full-face excavation method and thering-cut excavation method, and quantitative effects of the ring-cut excavation method are made clear.

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Sequential excavation analysis was conducted to identify the effects of mechanical properties of ground on the support characteristic curve and final support reaction.
As a result, it was found that the final support reaction was nearlythe same in elastic and elastoplastic models where the shotcrete after application had high stiffness but that there was great difference in final support reaction between the two models where the shotcrete had small stiffness as the groundwas deformed substantially near the tunnel face in the elastoplastic ground.

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Shotcrete in a mountain tunnel immediately after it is sprayed is affected by stress redistribution during tunnel excavation causing considerable deformation and strain. Some scholars are of the opinion that shotcrete yields causing considerable strain and can no longer be counted on as a support against earth pressure. In this study, load exceeding the strain at the peak strength was applied to shotcrete at early age. Then, the load was removed and the shotcrete was allowed to harden for a certain period of time. The strength and the modulus of elasticity of shotcrete after reloading were examined. As a result, it was found that when strain equal to or exceeding the peak strength was applied, strength and modulus of elasticity increased with time subsequently. Thus, shotcrete, even if subjected to heavy load at early age, proved to be counted on to work as a support

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Recently, road tunnel construction using the shield tunneling method has been utilized on infrastructure projects in urban areas. Due to the strict site constraints in urban area, the divergent junctions are to be located underground. Normally, for the construction of an underground diversion junction, large-scale cut and cover methods or the NATM method with ground improvement works shall be adopted. However, these methods involve significant issues relating to safety, cost and the construction period.
We then considered that we could construct a divergent junction with minimum section by cutting through the existing tunnel shield using another shield machine. For the development of a new construction method, various experiments have been carried out using specially designed segments for ease of cutting. This paper discusses the possibility of actually adopting this method based on the experiments undertaken.

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The design and construction methods of the underground joint method for shield tunnel construction have not been established, even though it has been put into practical use. In this study, the technical issues of this method were clarified first. The deformation behavior of the segments close to the opening of the shield liner for the underground joint was verified using two-dimensional frame analyses by focusing on the effects of the cover height, ground conditions, size of the opening, swelling pressure due to ground freezing and joint types. On the basis of the analytical results, basic information for establishing a new technical guideline of this method was given.

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To predict shield behavior correctly, understanding geological structure around the tunnel is important. Therefore, this paper infers the 3D geological structure using the data obtained from boring and investigates the 3D geological structure using the site data, such as, the soil component of muck and the horizontal shield jack moment. Furthermore, the horizontal deviation of the segment is examined using the inferred 3D geological structure. As a result, not only macro geological structure but also micro geological structure have an effect on shield behavior and shield operation.

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To investigate methods for designing high-quality shield tunnels by understanding and rationally assessing the actual loads acting on a shield tunnel during its construction and their effects on its segments, the authors monitored the loadsat the site of construction and conducted a three-dimensional FEM analysis usingthe monitored data. This paper describes the kinds of loads that need to be considered as loads that possibly act during construction and the long remaining effects of construction loads, which were determined based on monitored data of segments, and the results of the numerical analysis, which reproduced behaviors of the segments that received loads during construction.

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In greater Tokyo, there are plans to construct new belt highway and ring road toreduce terrible traffic congestion in the urban area But it is difficult to constructhem because there is so much infrastructure which was constructed over pastyears above ground and shallow underground. It is necessary of using the deep underground, and we must construct connecting sections of tunnel without cut and cover method. The highway needs long changing lanes, so new a construction methodthat stabilizes tunnel structure of connecting section without obstructive pillars is required. The objective of this research is to propose this new method, reinforcing shield tunnel with transverse arched structures and ground anchors without pillars in the connecting section, and analyze dynamics behavior of this compound structure.

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Urban telecom tunnels in Japan measure approximately 600 km and many of them arealready twenty through thirty years old. Selection of the optimum material for repairing cracks and water leakages is one of the most crucial points. For the purpose of selecting the optimum concrete structure repair material, this study has clarified the advantages and disadvantages of the currently employed water leakage repair materials, and has found out that a new modified polyurea resin provides an excellent material for ensuring conformance to cracks and others. Thus, detailed test evaluation was conducted, and, based on the results of this evaluation, the material is being utilized at the worksite of actual urban tunnels forthe past few years, with the result that the validity of this material has been verified.

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Tokyo Metro Co., Ltd. is constructing the No.13 subway line 8.9km long between Ikebukuro and Shibuya. This project includes a section 1, 245m long between Zoshigaya station and Nishi-Waseda station (tentative station names), where two single-track shield tunnels of 6, 600mm in segment outer diameter will be constructed in parallel. Since this section crosses a river, the longitudinal alignment is Vshaped, requiring construction of a pumping station at a depth of 40m under highly pressurized groundwater.
This paper discusses the result confirmed that adesign method was proper and the suggestion of a simple calculation method aboutthe non-open cut method of construction

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On the occasion of the stability evaluation to the unstable rock blocks in rock cliff which exist in the upper part of a tunnel entrance, many judgments based on the displacement behavior of the rock blocks are made. It is known that the time from the generation of the displacement to the collapse of the rock block is very short. Therefore, it is hard to catch a sign of collapse. The authors measured the dynamic characteristic of the rock blocks by the seismometers as well asthe vertical displacement measurement of the rock blocks by the displacement meters. As a result, it was confirmed that the dynamic characteristics of the rock blocks change before the displacement occurs.

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