[in Japanese]

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Recent years have seen a striking application of TBM for tunnels in Japan. To realize rapid excavation of TBM tunnels, it is essential to improve tunnel progress during difficult ground conditions. In the spalling rock conditions, immediate support behind the TBM is necessary to catch and hold the debris from the tunnel crown. For this purpose, the authors developed the light prefabricated steel support, Rock Liner, which is able to install within the tail of the TBM and thus eliminate the downtime.
The article outlines the light prefabricated steel support for TBM tunnels and its application results to the 5m dia. tunnel project.

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Recently, rationalization has been required in construction of steel bridges in order to reduce construction cost and periods. Taking the trend into account, the rampway bridges on the Wangan Route at Osaka Nanko area have been constructed by Hanshin Expressway Public Corporation.
This paper reports a rational design, construction method of the rampway bridges, and the related experimental studies on the applicability of precast slabs with simplified joints and longitudinal prestressing by sequential jacking-up and down method, as well as the field loading test results on one of the completed bridges.

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The construction result with recent large-diameter slurry shields shows that actual thrust and torque values are to a considerable extent lower than the installed capacity values.
This paper analyzes the actual performance data with large-diameter slurry shields between Komagome and Meguro of the Namboku Line constructed by the Teito Rapid Transit Authority and the measurement data during shield excavation of the Tanimachi section of the Line while providing the basic values necessary for thrust and torque of shield machines. This paper also proposes a method for estimating the installed thrust and torque of large-diameter slurry shields.

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The purpose of this paper is to present the rational design and construction methods of a continuous composite two-I-girder bridge with pre-stressed concrete slabs. Since this type of bridge has possibilities on realizing good cost performance, speedy construction, on-site labor saving and easy maintenance, the number of construction of it has been increasing. In the design of Chidorinosawa Bridge, we carried out several experimental and analytical studies in order to establish the rational design and construction methods. In this paper, in addition to results obtained from the above researches, valuable information on designing and constructing the composite two-I- girder bridge are summarized.

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A pretensioning system without abutment becomes possible by use of hollow prestressing bar (HPC system). The anchorage of the HPC system is contributed by bearing of nuts and bond between screws and concrete, which nuts and screws are at two ends of the bar. It is supposed that the anchorage of the HPC system can be calculated if the characteristics of the bond and bearing action are known respectively. In this study, some experiments were carried out to evidence the assumption and the results of the experiments show that the assumption is true. The time-depending characteristics and strength of anchorage which are needed in the HPC system were evidenced further in the experiment with a real scale specimen.

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Recently, since choride induced damage has come into the social problems, the maintenance and reinforcement of harbor facilities along the seaside received deterioration induced chloride is widely recognized as important issue.
The deterioration model of concrete members received deterioration induced chloride is developed in this paper. Existing deteriorated structures are investigated for developing the deterioration model. In investigation, crack width, cover concrete depth and corrosion rate of reinforcement are measured. Prediction system of bearing capacity in future of deteriorated structures based on reliability theory is developed by considering the variation of parameters obtained in situ.

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Recent demand for pipe-jacking method is to make possible long distance construction of water and sewage conduits in the local underground. It requires the reduction of propulsion force by decrease in friction of soils acting on outer pipe-wall. In this paper, the occurring characteristics of propulsion force are effectively measured during a cycle among field propulsion works, and friction data are analyzed based on laboratory experiment also. In order to decrease propulsion force, the lubricant effect and the “manicure” method are developed and evaluated on many execution works through sand, silt and clay ground respectively. As a result, expected effect is reported as satisfactory achievement.

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As a countermeasure against possible liquefaction in sandy grounds, a new sand compaction method is developed recently, in which gradual cylindrical cavity expansion of sand is done with least vibration and noise in driving a pile into sand In the present study, the mechanism and some characteristics of the compaction method are investigated by the soil-water coupled elasto-plastic analysis. The numerical results mainly indicate that even the comparatively dense sandy ground is improved not only because most of sand elements near/at the expanded area show hardening with compression below the C. S. L. in p′-q stress space, but also because the sequential operation of expansion followed by pulling the casing pipe makes the frictional resistance between soil and casing to controllable limits.

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This paper presents the methodology related to Decision-Making of Reinforcement of Slopes Based on Cost-Benefit-Analysis. As for an example to show the applicability of the proposed method, the slopes closed to highway, which are located at four major cities in Japan, were focused on. In detail, by considering the locality of seismic activity and losses due to slope failure quantitatively, risk was evaluated. Furthermore, by regarding the amount of risk mitigation by means of the installation of ground anchor as the benefit, cost-benefit -analysis was carried out to obtain the optimum countermeasures. The results showed that the proposed method has great possibility to determine the reinforcement of slope rationally.

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This paper is trying to estimate prospective future costs relating maintenance and repair work of existing quaywalls in Japanese ports. Firstly, current condition and past records of maintenance work of quaywalls including costs have been collected through nationwide surveys and interviews to port maintenance engineers.
Using the acquired data, a function to estimate regular maintenance costs (RMC function) was established and its applicability was verified.
Finally, the maintenance and repair cost was estimated with the RMC function in the years of 2010 and 2025, which might be approximately 10% and 20% respectively of total investment to port construction by government bodies.

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