It has been reported that tunnels constructed using the sheet pile method at the period of high economic growth have insufficient lining thickness, back cavities, and loose areas at the top due to the concrete placing technology and the methods adopted in construction management. Furthermore, in tunnels that have been in service for several decades, it is often reported that the strength of the surrounding ground has decreased and caused heaving related problems. These tunnels are not always safe in the event of an earthquake since the mechanical characteristics and load conditions of the ground change significantly from those at the time of design. Therefore, in this study, the behavior of the deteriorated loose area or a cavity behind tunnel during an earthquake will be examined

Roads, railroads, and airports support the movement of people, goods, and information, and occupy a major role in the development of cities. It is said that a country will decline if such infrastructure cannot be maintained properly. Automobiles, trains, aircraft, etc. will run on a daily basis after the construction of roads, railroads, airport facilities, etc. Repeated traffic loads and further exposure to environmental conditions such as rain, snow, and sunlight can lead to deterioration of materials, and thereby the structures in those facilities. Roads may suddenly collapse, or railroad rails may suddenly distort in midsummer, making the facility inoperable. Therefore, in order to minimize such "risks", we conduct research on maintenance and improvement of structures used in transportation facilities to tackle the geotechnical engineering issues.

It has been pointed out that internal erosion causes an increase in soil void volume, and changes in particle size, which results in the destabilization of the soil and reduces the stability of river embankments. On the other hand, the stability of the embankment during heavy rain is considered to be greatly affected not only by the strength, but also by the ease of water penetration, that is, the water retention ability of the embankment. But this is not enough to consider changes in the water retention ability caused due to internal erosion. Therefore, in this study, we try to model the water retention behaviour by using the particle size distribution and the pore ratio as indicators, with the aim of clarifying the change in the water retention of the ground caused due to internal erosion.

In 2009 G8 L’Aquila Summit, it was reaffirmed to half the global GHG (greenhouse gas) emissions by 2050, and as a part of this, it was announced to support the goal of reducing global GHG emissions by more than 80% across the developed countries. Under these circumstances, it is necessary to pursue all technical options in order to significantly reduce CO2 emissions associated with the use of fossil fuels by 2050. From this point of view, the Ministry of Economy, Trade and Industry regards CO2 as a carbon resource, recovers it, and promotes carbon recycling to reuse it in other forms. In this regard, through geotechnical engineering, we conduct research on carbon recycling of geomaterials to absorb CO2 during their manufacturing processes.

The coupled numerical manifold method (NMM) and discontinuous deformation analysis (DDA) areenhanced to simulate deformations of continuous soil and discontinuous masonry structures. Anelasto-plastic NMM-DDA is formulated that incorporates elasto-plastic constitutive laws into incremen-tal forms of the equation of motion. A node-based uniform strain element is applied to avoid volumetriclocking, which often occurs in conventional NMM-DDA. The proposed method is applied to three funda-mental boundary value problems: a beam bending problem, a bearing capacity problem of a footing, anda bearing capacity problem of a masonry structure. The method is verified through comparisons with conventional solutions

A novel method is proposed for determining the deformation anisotropy of rocks by a single triaxial test using a single specimen sampled from an arbitrary direction. Transversely isotropic elasticity is assumed for the purpose of application of the test method to sedimentary and metamorphic rocks, and the non-axial symmetric stress–strain relationships of anisotropic rocks are determined by triaxial testing by means of a simple improvement to the cap in the triaxial testing apparatus. Both the elastic parameters and the directions of the transversely isotropic elasticity can be obtained by measuring the shear deformations that occur under triaxial stress conditions. An overview of the method for determining transversely isotropic elasticity is presented in this paper, along with the results of a sensitivity analysis performed assuming simulated strains with random measurement errors. The results show that the directions of anisotropy can be determined precisely using the directions of the principal strains measured during isotropic compression and that the elastic parameters can be determined uniquely from the stress–strain relationships observed during both the isotropic and axial compression processes.