High-level radioactive waste from nuclear power generation will be disposed in a stable geological environment with a depth of more than 300m. JNC has been consistently assigned to lead R & D on geologic disposal in Japan and compiled the achievement into H 12 report in 1999. H 12 gave a comprehensive assessment of the technical feasibility and reliability of the disposal concept in Japan with a generic manner, which provided the technical basis for Japanese HLW disposal program to move from the phase of generic R & D into the implementation phase. In the stage of implementation, JNC, with other relevant research organizations, is assigned to continue basic R & D for further improving the technical reliabilities of geological disposal in Japan.

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Ductile segment is primary lining material for shield tunnel. Ductile segments were used from 1965 year. In this paper we report the results that we have investigated thickness of main parts and functions for corrosion of ductile segments. According to the results, thickness of main parts of ductile segments have not decreased at least for 24 years. The cause of the results are follows; The outer surfaces of ductile segments are not corroded under the ground. Because there are very little oxigen in underground water. The inner surfaces of ductile segment are not also corroded except water leakage from outer of tunnel.

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The Percussion Test is one of soundness estimation methods in structural system. We carried out a field test on the old rigid framed viaduct, which was going to be pulled down. We gave artificial cracks to the viaduct by using concrete cutter and measured the vibration of viaduct by Percussion Test at every stage of artificial damage. On the other hand, we calculated impact response of viaduct by strike using 3D framed model. We estimated the degree of damage of viaduct by comparing measured vibration with numerical one.
We present the validity of Percussion Test for the damage detection of structure in this paper.

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Recently, tomographic analysis method has been applied to the seismic refraction survey in tunnel geological investigations. In tomograpic analysis method, it is necessary to arrange measuring points that enable seismic rays to pass across the whole tunnel planning positions. Therefore, seismic refraction survey measurements for the seismic reciprocal method in 96 tunnels were re-analyzed to consider application to the tomographic analysis method. It is resulted that seismic rays partly passed across the tunnel positions in 43% tunnels, and these are caused by thick over burden, divisions of the measure line, and inappropriate arrangements of the shooting points and receiving distances. In this work, we report reasonable planning of the seismic refraction survey for the tomographic analysis method.

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Tunnels may deform resulting a change of tunnel shape because of natural disasters such as volcanic eruption, diastrophism, or earthquake. Those tunnels were handled by past standard measures; however there is a need to evaluate this past standard. In this research, record data of Toya tunnel which experienced damages because of the eruption of Usu Mountain is arranged and analyzed in order to obtain a proper restoration measure. Moreover, features of the proposed measure were compared with the past standard measure.

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Constructions of twin type closed tunnel with a center pillar, which stands very close to each other, tend to increase because of the limitation of the land utilization. This paper deals with the approach of the design method of the twin type closed tunnel which does not construct this center pillar. The authors had an experience with the construction of three types of twin closed tunnels on the same tunneling site. By this experience, the ordinary closed tunnels have some safety and environmental problems concern with the construction of center pillars. An applicability study of this construction method is described by comparison between the results of numerical analysis and the field measurements at this construction.

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This paper describes the field experiment of the permeation grouting with horizontal directional drilling as the countermeasure against liquefaction of the foundation soils beneath existing structures. The permeation grouting with horizontal directional drilling was performed beneath an exiting coastal levee. Investigations were conducted before and after the grouting, which included the removal of the levee to investigate the shape of the improved bodies. The investigations have revealed that the improved soils satisfy the required strength and the improved bodies have the same quality as the improved ones by grouting with linear boring reported in literatures. The placement of the improved bodies, which means the accuracy of the location system of the horizontal directional drilling, followed the planning position.

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Recently, fiber reinforced plastic method (FRP), mainly using carbon fiber and/or aramid fiber, has increasingly been used to prevent concrete spalling from tunnel lining. However, no sufficient design criteria or countermeasure selection criteria has been established. Thus, it has been desired to establish a rational design method in order to apply FRP. This paper introduces a series of punching shear tests of concrete slabs glued with a fiber sheet, and proposes a method to evaluate of the effect of FRP in order to establish design criteria. This paper also analyzes and categorizes past concrete spalling accidents into four levels according to their spalling scales, and proposes selection criteria and a design method of FRP.

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In this paper, methodology associated with the evaluation of cost variation in underground construction projects due to geotechnical risk is presented. In detail, indicator kriging is adopted to evaluate spatial distribution of mechanical parameter, RMR (Rock Mass Rating), which associates with rock mass classification and support patterns. Consequently, results pointed out that the evaluation method proposed in this study is applicable to predict cost variation in underground construction projects due to geotechnical risk, and useful to discuss the cost-benefit of additional in-situ investigation to reduce cost overrun risk.

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This paper shows check methods of the load acting on segments during tunneling to apply limit state design method to shield tunnels. According to construction records, it has turned out that a possibility that force of jack driving and brush pressure from tail seal will damage segment is high.
So this paper shows the check methods of segments against force of jack driving by the result of model experiments and real construction data. On the other hand, this paper defines the brush pressure from tail seal by load measurement records of real spots. The damages are estimated by calculation of segments against this brush pressure, and we've gotten the view of preventing from those damages.

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Recently, NATM method has been adopted in tunneling under shallow and unconsolidated ground. In order to stabilize the face and control the ground surface settlement, a variety of forepiling methods have been proposed. Above all, long-sized forepiling is evaluated as the effective one for its ability to reinforce the ground. However, this method is not economical, and has a bad influence on the total construction period. Therefore, authors proposed a new forepiling method using middle-sized forepiling as the more effective one, based on a series of laboratory tests. In this paper, the outline of this new method, the results of laboratory tests and its application to actual work are presented.

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In long horizontal boring, exceeding 30m, the accuracy of drilling becomes a problem in soft ground. In the jet-mixing method, once the exact accuracy of drilling cannot be obtained, the purpose of ground improvement may be unable to be achieved. To improve the accuracy of horizontal drilling, the direction controlling method was needed. In order to correct the direction, a mechanically simple wedge system was introduced. The prediction value of the amount of corrections, and the experiment results of drilling for 60 meters were compared and discussed. As a result, it has been recognized that by selecting of a suitable wedge angle and size of the bit, the drilling direction is controllable.

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This paper presents the development of a durability assessment system for high-strength friction grip (HSFG) bolted joint by using a neural network system. Most important factors of slip resistance on HSFG bolted joints are the bolt tension and the slip coefficient. So the authors have been investigating bolt tensions and slip coefficients of HSFG bolted joints on existing steel bridges.
Then the database system of HSFG bolted joints was constructed. And the prediction system of bolt tension by using a neural network was developed. As the result of a verification, we showed that this system will be able to predict bolt tensions of existing bridges.

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In order to inspect the breaking structure of burn cuts without large cut holes, we study step-by-step blasting.
According to the blasting at the center hole neither connections among a center hole and it's surrounding holes and increase free faces by expanding center hole were observed. At the next step-by-step continuous blasting, however, we observed that the cut area expanded sequentially and appox. 90% of drilling length could be advanced. By vacant holes surrounding the center hole become free faces on a limited small area, and many minimum cracks are produced and grown around the charging center hole.
As a result, it is observed that the cut is accomplished by continuous blasting at the effected weak area.

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