Applying the mechanical joint to the screwed steel pipe pile, a new field joint system composed of shear keys against torsional moment were proposed. In order to make clear the load carrying capacity of the proposed structure system, investigations including the loading test using the actual scale structure and the FEM analysis were carried out. Major results of the test are as follows; (1)The proposed joint system have enough load distribution performance, because the shear resistant keys and the joint parts have ability for enough plastic deformation. (2) Maximum load of the test exceeded the design strength of the joint that determined by the shear strength of the shear resistant keys or the bearing strength of the joint parts. As the result of these investigations, it is confirmed that the design method of proposed joint is proper to torsional moment load and it have enough strength against torsional moment load. Therefore, it can be said that the proposed joint system is applicable for the screwed pipe pile, as a main conclusion.

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In general, detached layers of airport asphalt pavement are detected with extraordinary sounds made by a hammer when it is hit on the pavement surface at nights. However the investigation needs a lot of workers and efforts because targeted area of airport asphalt pavement is so large. Therefore a new method is attempted in the study. The method takes infrared thermography continuously while a car on which cameras are mounted is driven. It was conducted on a real runway to see whether stripping damages in between the airport pavement layers were efficiently detected or not. As a result, dotted low-temperature distributions of the pavement surface were found at some locations. Most of them were found at the same or quite near places where extraordinary sounds were made by hammer-hitting. Then finite element analyses were carried out to simulate the surface temperature distributions of deteriorated pavements. The results show good agreement with the ones obtained from the filed investigation. These facts suggest the infrared thermography scanning is a quite promising technique to detect detached layers of airport asphalt pavement.

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Methods for manufacturing granulated materials using conventional fly ash as main raw material adopt technologies like granulations, solidifications, high-temperature curing and pulverization. Theses methods are perplexed and need long time manufacturing processes and high manufacturing cost. In this context, the authors have developed a technology which uses fly ash with small amount of water and cement. They are mixed and granulated within a short period of time. In this paper, the authors did various physical/mechanical tests to compare granulated materials prepared from fly ash with foundation soil such as sandy soil or gravel rich soil.

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The composite foundation of piles with improved soil is proposed to resistant the intensive seismic horizontal force. A soft or loose ground at the shallow depth is improved by the cement mixing method. Piles are constructed through the improved soil mass in order to transmit vertical loads to bearing stratum. The laboratory horizontal loading test was performed to investigate the behaviors of the composite foundation. Moreover, the simulation analysis by 3-D FEM analysis was carried out. It is shown that the horizontal bearing capacity of the composite foundation was much greater than that of the piles without the ground improvement, and the improved soil mass and piles worked as a mass. We examined the application of the simple design spring model of the composite foundation (beam-spring model) with the results of the in-situ horizontal loading test that we carried out before and this laboratory test.

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The ground reinforcing type foundation, which is a caisson type pile foundation with steel reinforced bars around the pile, was recently developed with the aim of increasing the bearing capacity of the caisson type pile foundation. Compared to current popular foundation, the ground reinforcing type foundation can reduce the construction cost dramatically because of the smaller in size of caisson. This research is focusing on the effect of inclination of reinforcements on the horizontal capacity of the ground reinforcing type foundation. For that purpose, the horizontal loading tests in the centrifugal acceleration were then conducted. Testing results showed that the horizontal capacity of foundation that placing the reinforcement in the diagonal direction is higher than that of the foundation placing the horizontal reinforcement. Testing results showed that the horizontal capacity of foundation that placing the reinforcement in the diagonal direction is higher than that of the foundation placing the horizontal reinforcement because normal force can act on the reinforcements effectively. Finally, a new design method for the ground reinforcing type foundation was then developed by using beam-spring model. This method can be used to evaluate the effect of inclination to the horizontal capacity and the model results agreed well with the testing results.

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An introduction of performance based design to infrastructures is on process. According to the performance based design, examination of not only bearing capacity but also long-term displacements of pile foundation are required in advance. On checking bearing capacity and displacements of pile foundation, it is important to consider the influence of pile group effect. Up to now, however, the research concerning pile group effect has focused horizontal resistance and displacement. In this research, pile group effect on bearing capacity and vertical displacement is examined through centrifuge model test and numerical simulation with soil-water coupling FEM, in which parameter is pile spacing (1.5D and 5.0D). As the result, followings are obtained; 1) evaluated from bearing capacity obtained through short-term load test, pile group effect is not appeared in pile spacing 5.0D; 2) evaluated from long-term displacements, pile group effect is appeared even in pile spacing 5.0D.

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Waste disposal site discharges carbon dioxide gas and methane gas due to decompose waste by microorganism. Methane gas is a kind of green house gas. The countermeasure which is oxidative decomposition of methane by methanotrophs is proposed to reduce methane gas. The oxidative decomposition by methanotrophs needs oxygen gas, methane gas and water. Therefore, a final cover material has to have suitable air permeability and hydraulic conductivity. In this study, the authors carried out the water retentivity test of soil and the measurement of natural water content under the nearly constant relative humidity to candidate material which is Kanto loam, two kinds of coal ash, water-granulated slag and pit sand. The authors discussed the experimental results and proposed the design method of a final cover material from matric potential and evaluated from volumetric gas content.

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In this paper, field observation result in dredging clay reclaimed land where the vacuum consolidation method was applied is reported. In addition, the prediction accuracy of soil-water coupled finite element analysis for ground de-formation behavior by the vacuum consolidation method and the stress state of improved ground was examined. In this analysis, the modified Cam-clay model considering the anisotropy which authors proposed as a constitutive equation was applied and it was compared with the original modified Cam-clay model. By the application of the proposed model, it was shown that the principle of the vacuum consolidation method could be examined from the ef-fective stress pass and that settlement and horizontal displacement in the improvement area could be predicted at the sufficient accuracy.

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