Public attention has been focussed on the safety of travel through road and rail tunnels recently, due to the recent tragic accidents which have claimed hundreds of lives. Many consider tunnel safety to be based in the provision of mitigation systems, but examination of the facts and issues surrounding tunnel travel show that the problems and solutions are related the basic civil engineering design.
The achievement of an appropriate level of safety for tunnel users requires a balance between the requirement to simplify the design and operation of the tunnel and the necessity to provide safety systems, such as cross passages and ventilation, which may have very significant effects on the civil design. These systems are expensive and are not always appropriate, depending upon the length of the tunnel, traffic types and hazards to users.
In order to rationalize tunnel safety design, risk based methods are increasingly used. This paper describes the issues surrounding a risk based design methodology and discusses some of the major factors which effect the civil and mechanical design of tunnels and tunnel systems. In particular, the choice of single or twin bore rail tunnels, means of escape, design fires and ventilation are highlighted, using examples from current projects.

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[in Japanese]

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Chemical grouting is widely used as an efficient method for water cut-off or stability of ground on tunnels or excavations. However, the characteristics of grout permeation is dependent on the grain size distribution or other ground conditions, therefore, the prediction of improvement effect has been considered as the subject to be examined preferentially. In the present study, an evaluation method on the mechanical stability and water cut-off capacity is proposed using a quantitative prediction of cohesion of sand solidified by chemical grouting, and water cut-off capacity that is the function of strains. Finite element analyses are conducted on the NATM tunnel construction project to evaluate the proposedmethod, andthe usefulness of the methodis demonstrated.

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When Tokachi-ohhashi bridge was demolished in 1996, material tests were carried out on the reinforcing steels and forging joints. It became clear that the chemical content of reinforcing steels had been adjusted for optimum strength and forging. While the tensile strength of the reinforcing steel of 44mm in diameter measured up to JES No. 24, broad variations were recorded. The standard deviation of tensile strength for reinforcing steel of 38mm or less in diameter was found to be almost the same as that of present reinforcing sreel. However, the standard deviation of yield strength was considerably larger than that of present reinforcing steel as yield strength had not been standardized at the time of construction. The forging joints displayed full tensile strength.

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The paper analyzes the effectiveness of the applied treatments with reference to their actual lifecycle costs that are summations of actual construction and maintenance costs. The maintenance costs and residual settlements are collected for 10 years after the opening of Do-Oh Expressway for the section between Sapporo and Iwamizawa. Then, the relationship between maintenance costs and residual settlements has been analyzed and formulated. This study has also proved that the various treatments applied for the section are most effective ones and thus, far more cost effective than the alternative, i. e. construction of bridges on the soft ground section.

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Shotcrete-and-rockbolts method (NATM) has been adopted around the bottom section of a large vertical ventilation shaft. It connects two horizontal tunnels and makes complex shape in this section. In this paper we have introduced a design method of NATM using three-dimensional FEM analysis and in-situ test and a method of field measurements in a shaft. According to the result of field measurement we have examined about a reliability of the design method and have discussed about a difference of support mechanism between short-step method and NATM, a distinctive deformation mechanism around a shaft and a specific behavior of ground around connecting section of the shaft.

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Since the Great Hanshin-Awaji earthquake, rubber bearings have been increasingly adopted nationwide. Recently, however, several cases of surface cracking have been reported in the cold region.
We tried to find out the mechanism of ozone cracking under low environmental temperature, and proposed the method to prevent such cracking and to evaluate weatherproof performance of rubber materials. Reliability of such methods was verified by outdoor exposure tests. Further we conducted research on the influence of cracking to bearing performance and confirmed the practicality in the use of natural rubber bearing in cold region.

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A system for measuring large strain in structural members is developed by using digital stereo vision. The system consists of the following processes, 1) trace the target points provided on the specimen surface, 2) identify the coordinates of each target point by digital stereo vision, 3) calculate displacement vector of each target point, and 4) calculate the strain field. All preprocesses are performed automatically, and the strain results can be obtained in some seconds. This system makes it possible to carry out semi-realtime strain measurements, even if an object includes three-dimensional deformation like local buckling.

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Rockfall countermeasures are very important in order to keep the safety of railway transportation. The typical rockfall fence for this purpose is consisted of posts, wire ropes and steel nets, must be designed so that the total absorbing energy of components is larger than the planned rockfall kinetic energy. However, this conventional fence has not been tested precisely so far. Then, static loading experiments for steel nets are carried out to study the relationship between dimensioning and deformation characteristics. In addition, a new-model net fence, which is expected to have large deformation than that of conventional nets, is tested. As a result, it is proved that the absorbed energy of new fences is larger than that of conventional ones.

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To reduce the cost and shorten the construction period in the Kazunogawa Dam project, we applied for the first time 110kg/m³ of reduced binding materials in concrete mix proportion and 1m of thickened layer in the RCD construction method.
Before starting the concrete work, we measured the acceleration or pressures inside the concrete during compaction with vibrating rollers, and determined the work method and specifications.
This paper clarifies the behavior of concrete for RCD during compaction based on field tests and describes a real-time control system that covers all areas of compaction work.

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Portland cement based materials are widely used for enhancing strength of soil mass as in jet grouting or other similar methods. However, degree of improvement depends not only on characteristics of cement but also on types of soil and their fine content. The relations between the soil's fine content and degree of improvement were studied in laboratory by changing both cement amount mixed and fine content. With the level 30% of fine content in the original soil as threshold, the effect of cement mixing differs widely. The authors are proposing two sets of simple formulae for soil with fine component less than 30% and for soil with more than 30% of fine content.

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The motion of the container cranes were accompained by uplifting of their legs during the 1995 Hyogoken-nambu Earthquake. Another from of damage was overturning, followed by derailment and tilting of the structure, which particularly affected the hinged-leg structures. The other side, it seems that quay walls are also damaged due to crane's loading and uplifting phenomena. Therefore, in this paper, to investigate the dynamic behavior of response controlled container crane, we carried out an excitation test on a 1/15 reduced scale model. From the test results, it became evident that the response of crane and reaction force of the crane's rail are reduced and the uplifting phenomenon of crane's legs is evaded.

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This paper deals with two kinds of simplified methods (Method I and Method II) to evaluate the maximum response amplitude of continuous type pedestrian bridges caused by a walking person; Method I does not require not only the eigenvalue calculation but also the dynamic response analysis, and Method II, based on the results of eigenvalue calculation, does not require dynamic response analysis. Numerical examples were evaluated out for several bridge models. It was ascertained that the evaluation value based on each method proposed in this paper was fairly in a good agreement with the computed value when a person walked on the continuous bridges with the same pace as natural frequency.

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Diaphragm wall is frequently used as the retaining wall or the cut-off wall for open cut excavation and also used as the wall foundation for super-structure. The trench wall stability is the key issue for the design and construction method of diaphragm wall. The aim of this study is to investigate the diaphragm wall stability during excavation in saturated sand. Field measurement of the pore water pressure variation during diaphragm wall excavation were carried out in the alluvial deposit. The mechanism for the variation of pore water pressure and its effect upon the factor of safety for trench wall stability is investigated.

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In order to rationalize structural maintenance, a non-contact vibration measurement system with Laser Doppler Vibrometer (LDV) has been constructed in laboratory testing. However, in the case of measuring vibration of existing real structures, the objectives would possess low laser reflection characteristics. Therefore, it is difficult to apply an LDV to these. In this study, the measurement system is improved with an automatic searching function of the optical point that could give the maximum laser reflection around the objective points. This improvement produces a tremendous advance in measurement accuracy for real structures. As a case study, vibration measurement is conducted at a steel girder and a reinforced concrete of existing viaduct. The mode shapes are identified and quality of measurement is also evaluated quantitatively.

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The amount of coal ash has been increasing and development of the effective use has been urgently needed. Authors have been developping the production methods of concrete mixed with coal ash and metal slag. Laboratory tests show that the optimum mix design can be determined from the vibrating compaction energy and physical properties. The present study includes site placing tests which were conducted in order to confirm the applicability of coal ash to concrete of wave dissipating blocks. The preliminary laboratory tests were carried out to investigate the consistency, compactability, and duability of coal ash concrete. From the test results, the optimum mix design method of concrete mixed with coal ash and the compacting method were evaluated.

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In this paper, the risk sharing rules are investigated to characterize the contructural structure for the construction works. The authors exclusively focus upon the GCW forms and the FIDIC forms, which can be regarded as typical examples of incomplete contract forms. Risks involved in construction works are classified into exogenous and endogenous ones. The paper claims that clear differences in both contract forms in coping with endogenous risks can be found, while there are no essential differences in resolving exogenous ones. The paper concludes by summarizing the remaining research issues to be scrutinized in future.

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As many inclination meters have been used at many construction sites where construction works are executed very closely to the existing structurers and an observational construction method is adopted, higher accuracy of inclination measurement is sought for. But the sensor as its core has much room for improvement to prevent precision deterioration due to a long time atmospheric temperature change in the field.
This study developed an all-directional inclination meter that can prevent the effect of temperature change utilizing an eddy current of no-contact. It is proved to be practically useful with good measurement precision and stability through its basic expeiment, indoor test and field test.

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In this paper, a bargaining game model with two-sided outside options is presented to investigate the resolution mechanism of disputes around construction contracts. Most disputes in construction contacts stem from disaccord in contractual interpretation. Arbitration can be regarded as outside option, which is available by both parties in negotiation process. The model explains how dispute resolution processes can be controlled by third parties' adjudication. The differences in dispute resolution mechanisms of GCW and FIDIC are also analyzed, and the remaining research issues are summarized.

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Portable GPS has never been used in practical surveying because of its poor accuracy, but it has great potential for practical use due to its low cost equipment. We proposed a method to improve positioning accuracy in portable GPS surveying by adopting differential GPS in which four active signals from four satellites are fixed during the period of measurement at the two end stations. On May 1, 2000, the intentional degradation of the GPS signals, known as Selective Availability (SA), was turned off. This study aims to compare the results of the positioning accuracy before and after the cessation of SA. The experimental results indicated that our proposal of positioning accuracy is still applicable even after the termination of SA.

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