Excavation for the foundation of 1A anchorage of AKASHI-KAIKYO BRIDGE was finished in August 1991. This excavation had large depth and scale: 64m depth and 80.6m inner-diameter, which we had not experienced before. And, there was also some concern about bottom ground failure due to the ground water, because the ground water level was very high and the bottom ground was soft rock whose permeability was not so low.
Accordingly, we observed behavior of the retaining wall as well as condition of the bottom ground and estimated them by simulation analyses in order to predict and confirm stability of them during the excavation. We thus finished it in safety. This paper describes results of observation of the retaining wall and the bottom ground and simulation analyses in this excavation work.

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Underground storage of pressurized gas has been well experienced in Europe and America. However, it is difficult to find storage works in Japan, because of its poor geological condition which we are usually encountered during construction. In this paper, a survey has been conducted and technical reports on the Underground storage of pressurized gas on abroad have been carefully investigated in order to discuss the capadbility of that in Japan. We also demonstrate a few condition to make possible underground storage in Japan.

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Water front development for rapid industrialization and urbanization in our country have caused tremendous environmental pollutions, and one of these various pollutions was the water pollution caused by marine construction works (dredging and reclamation works). In the first half of 1970's, these works often broke out many troubles with fishermen everywhere in our country.
In order to solve these problems, Port Bureau of M. of Transport carried out many kinds of intensive field investigation, together with The 1-5's Port Construction Bureaus, in 1973-74. And using these field studies etc., the 4's Bureau developed pre-forecasting method of water pollution by marine construction works.
This report presents that we analyzed the contents of these investigations and determined the index of water pollution by works and created the table of the SS load per unit soil volume handled by marine construction works.

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In recent years, it becomes very important problem to establish the optimum design methods of a hard metal bit of a shield machine in long underwater tunneling works to elongate the wear life and to reduce the thrust and the excavation torque. Here, 6 kinds of hard metal bit of sintered alloy are tested to verify the wear lives in a steady state excavation test for a weathered granite soft rock mass. At the same time, the relations between the excavation force, the rake angle, the clearance angle of the cutter bit and the radius of tip curvature due to wear and the shape variations have been investigated. As a result, it is clarified that the wear resistance of hard metal E 1 sintered in hot isostatic pressing is excellent and the bit shape having rake angle π/18rad and clearance angle π/6rad is best to maintain the longest wear life.

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In recent years, the studies at the view point of landscape design are done in the process of constructive planning of a new highway. This study examines the psychological evaluation for the shape of tunnel gates by semantic differntial method. In this paper, sixteen photos of tunnel gates which were taken at the highways in Japan are used for the comparison. The results are as follows. In case of wall type, the shape of upper part gives differential image, exactly the curved shape gives lighter, softer and more rhythmical image and more favorable impression than the straight one. On the other hand, the arch type which is slender at the top gives the same image and the bell mouth type gives favorable impression to the people.

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Evaluating the landscape of bridges quantitatively has been considered to be very difficult since it involves subjective factors such as aesthetic sense. Therefore, by accumulating the knowledge of experts and clarifying the mechanism of its usage, the authors have developed an advisory system which can quantitatively evaluate the landscape of different types of river-crossing bridges. A user can select a suitable bridge type from the landscape point of view by considering the advice from this system. The authors have also studied basic problems of expert systems such as the possibility of the independent development of the rules, the knowledge base and reasoning engine respectively.

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The design optimization of the retaining wall structures is studied by using GA. The design variables of this design problem are the vertical positions of the waling beams and the horizontal interval of the cross beams. These are continuous variables essentially, but are treated as discrete variables in this paper. As the ready-made steel products are used for the structural members, the construction cost, which is one of the objective functions of this study, is discontinuous with respect to the design variables. The basic requirements for these types of the structures are not only the construction cost, but also the structural security and the workability. So the design problem is formulated as discrete multi-objective design problem, and the modified GA is tried to applied to this problem. Several numerical design problems are solved and the results show the utility of the method of this paper.

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In the present paper, the results of specialists' assessment of danger levels are compiled using the s-p score table. A method is proposed here as to the determination of the weight of judgement factor which is rather difficult but very important to the engineers, and the viability of the method is evaluated.
Furthermore a method is also suggested to evaluate the judgement of an inexperienced engineer by using the compiled judgements of specialists. In case the inexperienced engineer's judgement is not in conformity with that of the specialist the cause or reason is informed to the inexperienced engineer and the same judgement of a specialist is made possible.

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Determination of microbial corrosion is very important to anticipate the remaining service life of the concrete structures in order to avoid the recurrence of structures collapse or failures. The behaviors of Fe-ions and formation of Fe-rich layer were studied. Fe-ions started to migrate to carbonated zone during carbonation process. When surface pH decreased by microbial corrosion process, Fe-ions accumulated and concentrated locally forming Fe-layer at areas between corroded and sound zones. Results show that Fe-layer depth is more than the depth of corrosion. Calculation of Fe-layer formation rates as a mean to determine the corrosion rate with certain factor of safety is proposed.

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Carbonation process involves the reduction of surface pH of concrete and is the prerequisite to microbial corrosion to occur. The highest carbonation rate was found in specimens exposed to 0.5% CO₂ gas, followed by 5% and control (0.03%) specimens. The carbonation rates for 5%, 0.5%, and control were 7.1, 16.4, and 4.3mm/year, respectively. Microbial corrosion experiment showed that 0.5 % specimens had the highest corrosion rates and percentage mass loss of 3.8mm/year and 13.9 percent/year, respectively. It can be concluded that carbonation stimulated microbial corrosion process. However, under quite high CO₂ gas concentration (5%), corrosion process was reduced due to formation of much calcite in the carbonated zone. Growth of T. thiooxidans was stimulated on the reduced pH of carbonated surface.

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The damping device has been the center of interest in our country as an effective method to suppress the wind-induced cable vibrations of cable-stayed bridges. It may happen that the transverse local vibrations of the cables as a partial structure system couple with the vibrations of the cable-stayed bridge as a whole structure system, for those bridges in recent years which tend to be more longer and to have the multi-cable system. Therefore, the effects of cable vibration dampers on the whole structural damping of a two-span steel cable-stayed girder bridge where the viscous-shear dampers have been installed near the lower end of each cable was investigated by means of complex eigenvalue calculation.

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