We collected the results of geotechnical surveys at 11 locations in 7 seaports where the design shear strength of the clayey ground was evaluated by using the combined method. In the combined method, for each soil sample taken by the fixed piston sampler, both the unconfined compressive strength and the strength of triaxial CU compression test were carried out to estimate the quality of the soil sample. The quality-evaluation results of 283 samples classified to the regions I (good or very good), II (moderate), III (poor) and IV (very poor) were 49.5%, 25.1%, 9.5%, and 15.9%, respectively. The satisfactory quality was 74.6% when "good or very good" and "moderate" were combined. The average ratio of the S_u(UCS), the average of q_u/2 to S_u(SCU), the simple CU strength was 0.773, which was slightly higher than the moderate 0.75. A practical design shear strength evaluation method was proposed for the cases where more than half of samples (50-70%) are classified to regions I and II and some (25% or less) are classified to be regions IV.

This paper discusses the factors affecting the strength development of dredged soil stabilized with steel slag. Fifteen different soils and forty-five slags were tested, focusing on silica eluted from dredged soil as well as calcium eluted from slag. The higher unconfined compressive strengths were obtained according to the elution mass of silica from the dredged soil when the sufficient calcium was eluted from the steel slag. Similarly, the higher unconfined compressive strengths were obtained according to the elution mass of calcium from steel slag when the sufficient silica was provided from the soil. These results indicated that required elution masses of both silica and calcium exist to achieve the target strength. To obtain the strength of 100 kN/m², calcium elution of 5.0 mg/g and silica elution of 60 mg/g are required.

There have been many reports of damage caused by earthquake-induced lateral displacement on an abutment-backfill interface. As such displacement may lead to the derailment of high-speed trains, earthquake countermeasures for existing railway abutments have become an urgent issue, and various countermeasures have been enforced for the Tokaido Shinkansen line since its opening. As per the current design standards, the existing method for constructing earthquake-resistant countermeasures does not necessarily assume Level 2 (L2) seismic activity. In addition, there are limits to the construction environment and construction efficiency, such as construction on tracks being possible only at night and traffic restrictions on the roads near abutments. Therefore, we aim to develop and apply a method for the construction of earthquake-resistant countermeasures to increase the earthquake resistance of existing railway abutments against L2 seismic activity and enable construction work beside abutments during the day. In this study, we developed a countermeasure construction method for railway abutments using reinforcing bars integrated with side walls and verified its effectiveness through tilting tests and model shaking tests. Based on the results, it is confirmed that the sliding mode of the reinforced abutments with the side wall joints is dominant. Moreover, it is possible to improve the maximum resistance of the abutments and limit their residual horizontal displacement and subsidence of the back embankments near the abutments.

Up-flow column percolation tests were conducted to discuss the rigor interpretations and the engineering applications, adequate descriptions of which have been limited. Two types of marine sediments were tested using the two different sizes of columns (Φ 5 cm×h 10 or 30 cm) with a flow rate of 12 or 36 mL/h. Trends in concentrations with pore volumes of flow (PVF) were examined. Since the concentration trends of selenium provided a monotonous decrease and showed the maximum value of approximately 0 PVF, and showed half of the maximum value less than 1 PVF, their leaching was considered to diminish immediately. On the other hand, arsenic and fluorine concentrations showed initial increases and consequent decreases, therefore their leaching continued after 10 PVF. Since monotonous decreasing leaching contaminants show the maximum concentration of approximately 0 PVF, a more realistic risk analysis can be conducted to obtain the maximum concentration from column tests. To investigate the trends in concentrations, column tests should be carried out at least 2 PVF.

In mountain tunnel construction projects, the estimated condition based on the survey are often different from and the actual condition due to the ground uncertainty, leading to a large increase in construction costs. For the purpose of improving rock classification in preliminary survey of construction projects, we have studied the applicability of Artificial Neural Network (ANN). In this study, we began by optimizing our neural network model and compared the results of rock classification with other machine learning methods focusing on physical characteristics. After that, we investigated the effect on rock classification by inputting rock type information to the neural network. It is concluded that the performance of ANN is better than other algorithms and consideration of rock types is necessary.

This study focuses on road embankments with and without damage by the 2007 Noto-Hanto earthquake and by the 2011 off the Pacific coast of Tohoku earthquake in order to investigate: a) the relationship between the global safety factor evaluated by pseudo-static analysis and the degree of actual damage, and b) the value of the horizontal seismic coefficient which should be employed in the conventional design method for preventing severe damage. For these purposes, a series of numerical analyses based on the parameters evaluated by the field and laboratory tests were performed in the present study. The results from dynamic centrifuge model tests on road embankments conducted previously by the first author were also analyzed to supplement a lack of data. The following conclusions can be derived from the results presented in this paper: a) the crest settlement tended to increase with decreasing global safety factor with the consideration of seismic force, which suggests that the global safety factor evaluated by pseudo-static analysis can qualitatively explain the degree of earthquake-induced damage of embankments, and b) the value of the design horizontal seismic coefficient to prevent severe damage with crest settlement larger than 40 cm could be obtained by 0.20∙A_max/620, where A_max is the predicted maximum acceleration of an earthquake.

In this research, the authors are developing a solidifying material for ground improvement using inorganic waste as a raw material. The solidifying material is a mixture of blast furnace slag, inorganic waste containing a large amount of silica (such as waste glass fine powder or fly ash), and an alkaline aid while being heat-treated. In this paper, the authors reviewed the mixing process of fine powder of waste glass or fly ash and heat treatment of an alkaline aid, and produced an additive that was simplified by mixing only. Then, the difference in the performance of the solidifying material depending on the presence or absence of the heat treatment process in the additive manufacturing was verified in terms of the influence on the curing action. Specifically, assuming that the solidifying material to which each additive is added is applied to the high-pressure injection stirring method, that is one of the ground improvement methods, the viscosity of the solidifying material over time and ordinary Portland cement are added separately.

In urban areas, excessive groundwater pumping has caused severe ground settlement in the past. As a result, the pumping of groundwater is now regulated, raising the level of groundwater and causing various problems such as the risk of liquefaction. Shallow subsurface model has been well utilized for the evaluation of geo-disasters such as earthquake motion and liquefaction potential. To date, it has been constructed nationwide by various methods. In this study, we constructed shallow subsurface model using Kansai Geo-informatics Database from the surface layer to the engineering basement for every 250m mesh in the Osaka and Kobe areas. We also modeled the grain size characteristics of the sand layer and the geotechnical properties of the clay layer. These results provide basic data for solving geotechnical problems.