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In this research, a reinforcement mechanism for shallow foundations is determined through laboratory model tests and numerical analyses. The numerical analyses are performed with the finite element program FEMtij-2D using the elastoplastic subloading tij model. The frictional behavior between the reinforcement and the ground is simulated using an elastoplastic joint element. Several tests were performed whereby the installation depth, length, roughness, and fixity conditions at the edges of the reinforcement were varied. Results show that the effectiveness of the reinforcement and the bearing capacity of the reinforced ground depend on the position, length, roughness, and fixity condition of the reinforcement. A significant increase in the bearing capacity can be achieved if the geosynthetics are properly placed at an optimum length with the boundary fixed to the ground. The effect of the loading position is also investigated because in reality the load on a foundation does not always act at the center of the foundation. The numerical results accurately describe the experimental results; the simulations accurately account for the mechanical behaviors of both the soil and reinforcement and the frictional behavior between them. Therefore, the simulation technique can be used to predict the bearing capacity of reinforced ground.

Pile foundations are commonly used for heavy superstructures in soft grounds. The failures of pile foundations have been reported in past major earthquakes. An economical and effective method for improving the seismic performance of existing pile foundations is the partial-ground-improvement method (PGI). The main concern of this method is how to determine the size and the location of the areas around a pile foundation to be improved. In this paper, numerical analyses and shaking table tests are conducted to find the optimum pattern for the PGI method. In the numerical analysis, the three-dimensional (3D) dynamic finite element method (FEM) is used with a unified system consisting of a ground, a group-pile foundation and a superstructure. Furthermore, the mechanical behaviors of the ground, the group-pile foundation and the superstructure are modeled by the Cyclic Mobility model, the axial force-dependent model, and the tri-linear model, respectively. With the above-mentioned numerical method, four different patterns of PGI are investigated and then an optimum pattern for the PGI method is proposed. All the numerical analyses are also confirmed by 1 g shaking table tests. All the tests and the numerical analyses are conducted under dry condition.

In this paper, particular attention was paid to the seismic enhancement effect of group-pile foundation with partial ground improvement method that is used for existing pile foundations in practical engineering. A model test on a full system with a superstructure, a nine-pile foundation and a sandy ground was conducted with the shaking table test device. The model pile is made from aluminum and the model ground is made from Toyoura Sand. The shaking table test device is 120 cm in width and 160 cm in length. The maximum acceleration is 1 g and the maximum displacement is 5 cm. The maximum payload is 16 kN and the highest frequency is 10 Hz. The model ground is carefully prepared to obtain a ground with controllable unified density. Before the shaking table test, the pattern of the partial ground improvement for an existed group-pile foundation is carefully selected using numerical tests with a 3D elastoplastic static finite element analysis. In the analysis, the nonlinear behavior of ground and piles are described by the cyclic mobility model ( Zhang et al., 2007 ) and the axial force dependent model (AFD model) proposed by Zhang and Kimura (2002) can take into consideration of axial-force dependency in the nonlinear moment–curvature relations. The applicability of the numerical analysis has been verified in previous works by comparing the numerical results with a real-scale field tests ( Kosa et al., 1998 ). Based on the results from the numerical tests on seismic enhancement effect of group-pile foundation with ground improvement, an optimum pattern of partial ground improvement of an existing pile foundations has been picked out for shaking table test. A numerical analysis using the program DBLEAVES ( Ye, 2007 ) is also conducted for the same optimum pattern for comparison purposes. The effectiveness of the partial ground improvement method has been proved by both the shaking table test and the numerical analysis.

静的圧入締固め工法（コンパクショングラウチング工法，以下CPG）は低流動性モルタルを高圧で地盤内に圧入し，地盤を締め固める工法である．CPGは既設構造物の液状化対策工法として実施工で採用されているが，施工時に地盤隆起を起こし施設に悪影響を与える可能性がある．本ノートでは，CPG施工時の地盤隆起を予測する手法を，空洞拡張理論の考え方と既往の設計法を利用して考察を行い提案している．そして，提案手法の精度を実測値と比較して検討している．

Liquefaction is a common phenomenon of the sandy ground in an earthquake. It leads to the floatation of underground structures or subsidence of structure in the ground. Formerly, the phenomenon was associated with the main shock that lasts for relatively a short time. In recent years, however, it has been found that the bearing capacity of soils may also decrease during short-term seismic motions that occur multiple times (aftershocks) in the same way as in a long-term seismic motion. Crushed tiles abundant in Aichi Prefecture (Japan), a center for tile industry, are one of the promising recycling materials for a countermeasure against soil liquefaction. This research investigates the effectiveness of these tiles as a countermeasure against liquefaction for a long-term seismic motion and short-term multiple aftershocks in case of small structures, and confirms their physical and mechanical properties.

To increase bearing capacity of a foundation, geosynthetic is laid beneath the foundation. In previous research, the authors investigated the reinforcement mechanism by changing the length and the laying depth of the reinforcement (Nakai et al, 2009). In the present study, to get more bearing capacity, the reinforcing effect in the case that each edge of the reinforcement is fixed with the soil is investigated. For this purpose, 2D model tests and the corresponding non-linear finite element analysis are carried out. In these tests and simulation, the depth of the reinforcement is changed under constant length of reinforcement. Reinforcing effects, under concentric and eccentric load, are discussed. It is revealed that a significant increase of the bearing capacity is observed in the model tests when the reinforcement is set up in the ground with an appropriate depth under both concentric and eccentric loads. The results of numerical simulation - in which the stress-stain behavior of the soil and the frictional behavior between soil and reinforcement are properly taken into consideration - show good agreement with the observed results.

Liquefaction usually occurs in many sandy grounds during earthquake including Japan. Liquefaction causes damage of structures by making floatation or subsidence of them, and reduces the necessary performance of the structures. For example, stability of retaining wall based on skeleton weight of the structure is reduced due to subsidence and inadequate support which causes the destabilization of the structure. In addition, the light weight underground structure suffers damage such as floating due to the reduction of shear strength of soils during liquefaction. The damage occurs not only to the civil engineering structures (roads, bridges, etc.) but also to the residential buildings which makes the building unusable. On the other hand, Aichi Prefecture (Japan) is a center of the production of tiles where the crushed tile can be used as recycling materials for a measure of soil liquefaction. In this research, we have investigated the material property of the crushed tile and examined the effectiveness of countermeasure against liquefaction by shaking table tests. It is found that liquefaction of the ground can be reduced using crushed tiles because of its high friction and drainage properties. In the research, we found that the anti-liquefaction manhole which was backfilled by clashed tile floated only by 1/3 of the magnitude observed in the case of without countermeasure against liquefaction.

Reactions of hidered phenols, such as 2,6-di-t-butyl-4-methylphenol, 3,5-di-t-butyl-4-hydroxybenzyl alcohol, and 2,6-di-t-butylphenol, with benzyltrimethylammonium tribromide were carried out in dichloromethane in the presence of water, t-butyl alcohol, or aqueous sodium hydroxide at room temperature. Sequential reaction processes were provided by the obtained products.

The reaction of 1,4-benzenediols with 1.1 equiv of benzyltrimethylammonium tribromide in dichloromethane in the presence of aqueous sodium acetate at room temperature gave 2,5-cyclohexadiene-1,4-diones in good yields. On the other hand, the reaction of 1,4-benzenediols with a large excess of the reagent in aqueous acetic acid at 40–60°C gave polybromo-substituted 2,5-cyclohexadiene-1,4-diones in good yields.