Shinya Inazumi

Influence of pulling out existing piles on the surrounding ground

Teardowns of social infrastructure, including civil structures, have been increasing in number in recent years because these structures have aged and their utilization has decreased along with the decrease in population. The number pile foundations being pulled out is now far greater than that being newly installed. However, after a pile foundation is pulled out, the mechanical characteristics of the surrounding ground may be affected by the existence of the resulting hole formed by pulling out. There are no regulations yet on injecting fillers into pull-out holes, and the influence of filler strength on the surrounding ground is yet to be elucidated. This study considers the influence of a pull-out hole on the static and dynamic characteristics of the surrounding ground using two-dimensional dynamic finite-element analysis. The special qualities required by fillers injected into such holes are also clarified.

Evaluation of Containment Performance from Viewpoints of Diffusion and Dispersion for Impervious Structures at Coastal Landfill Sites

The containment performance of impervious structures is considered the most important performance, which the toxic substances are enclosed in coastal landfill sites. The containment performance is evaluated generally by the hydraulic conductivity and the thickness of impervious structures to focus on an advection. However, the leakage of toxic substances is affected by a diffusion and a dispersion. The diffusion and the dispersion are considered to be easily distinguished on the impervious structure which has the low-hydraulic conductivity. Such phenomena should be considered due to evaluate the containment performance. This is because to improve the containment performance and comprehend leakage of the toxic substances. The containment performance is evaluated from the viewpoint of the diffusion and the dispersion in this research. Concretely, the influence which the toxic substances leaks from impervious structures on the diffusion and the dispersion is evaluated by the infiltration and advection–dispersion analysis on steel-made side impervious walls. In other word, The relation between the leaking amount of toxic substances and coefficient of molecular diffusion, the relation between the travel time or the flow velocity and the leaking amount and the change in the water-level difference are considered respectively. So, the leaking amount which is influenced by a diffusion and a dispersion is considered. Consideration about to secure the containment performance of impervious structure which is restrained leakage by a diffusion and a dispersion.

Penetration behavior of chemical grouting considering ground uncertainty

The chemical grouting is one type of ground-improvement methods. It injects liquid consolidation material into the gaps of a soft sandy ground. It is mainly used for improving a stable ground, such as by preventing liquefaction and increasing the strength of the ground. Chemical grouting has been successfully applied at many construction sites; however, the behavior of the chemical solution being injected into the ground is unclear. Furthermore, because the ground involves uncertainty, it is difficult to determine the penetration range of the chemicals (grouting materials). In this study, the authors carry out a seepage flow analysis of a chemical solution for a ground requiring improvement due to uncertainty. They then compare the difference in the behavior of the chemical solution between the case in which the ground is assumed to be heterogeneous and that in which it is assumed to be homogeneous.

Fluidity evaluation of fluidisation treated soils based on the moving particle semi-implicit method

This paper presents results of a fluidity evaluation for fluidisation-treated soils using the moving particle semi-implicit method (MPS method). In recent years within Japan, fluidisation-treated soils have been frequently used as soil materials for land reclamation projects, backfilling underground spaces, etc. However, the design and mixing of fluidisation-treated soils are based on previous experiences applied to new situations. It is useful to consider the findings based the application of the MPS method to the fluidity assessment and theory of fluidisation-treated soil, which is the focus of this study. As a result, it was clarified that the fluidity of fluidisation-treated soil could be sufficiently reproduced using Bingham model with the MPS method.

Evaluation of flow-ability on fluidization treated soils based on flow analysis by MPS method

Recently, fluidization treated soils have come to be used as landfill materials or fillers in such landfill of underground space in Japan. However, the design and construction of the fluidization treated soils at present is based only on empirical knowledge. Therefore, taking into account the findings based on a theory is thought to be useful. In this study, it has evaluated the flow-ability of the fluidization treated soils based on the flow analysis by the MPS method and the experimental evaluation. Favorable results have been obtained in the numerical flow analysis by using the Bingham model to the MPS method. In addition, the authors have developed a fluidization treated soil with increased flow-ability (super-fluidization treated soil). It has evaluated from two aspects of mechanical properties and flow properties of the high flow of the super-fluidization treated soil. The flow properties show that it has a high flow-ability than the fluidization treated soil.

Assessment of potassium silicate based surface penetration materials with low viscosity in the repair of concrete structures

In recent years, surface penetration has attracted attention as a repair method for concretes structures. Silicate based penetration materials have been used in this method. In this study, visual appearance, water permeability, water absorption, water-vapor permeability, neutralization (carbonation) and chloride ion penetration testing of a silicate based surface penetration material are performed. The protection and waterproofing effects of a silicate based surface penetration material are evaluated based on the results. The silicate based surface penetration material penetrates deeply into the concrete surface, shows self-repair functionality, is effective to the neutralization (the carbonation) of the concrete and improves the performance of waterproofing. The penetration depth of the silicate based surface penetration materials plays an important role in the surface penetration method. Therefore, permeability testing of a mortar specimen, penetration depth testing of the mortar specimens with various silicate based surface penetration materials, viscosity testing of the materials and modelling of the one dimensional penetration into the mortar specimens are performed. The results of viscosity testing and coefficient of permeability suggest that these silicate based surface penetration materials will perform well surface penetration materials.

Potential for silica-based solidification materials as soil improving agents

In a series of studies, the authors have developed a powdery silica-based solidification material composed of heat-treated inorganic solid wastes with a high content of silica products (such as waste glass and waste fly ash) mixed with alkali aids. This material is most suitable for use with iron or steel slag, such as that which comes from a blast furnace or a steel-making process. The powdery silica-based solidification material mixed with iron and steel slag can be expected to exhibit higher mechanical strength and more predominant characteristics than a powdery cement-based solidification material. In this study, the solidification mechanism for the mixture of the silica-based solidification material, blast furnace slag and water is clarified from the viewpoints of chemistry and mineralogy by conducting X-ray diffraction analysis, X-ray fluorescence spectrometry and inductively coupled plasma spectroscopy.

Prediction of spatial distribution on soil surveying values using geostastics methods

Recently, land subsidence and liquefaction are becoming evident. But neither the countermeasure nor research technique have not been established. In order to determine the cause, more detailed comprehension of soil properties is essential; therefore, in this research new-typed Swedish sounding testing machine (the NSWS testing machine), capable of measuring more detailed physical properties of in-ground was utilized and conducted a subsurface investigation at a narrow detailed house at which land subsurface have occurred. Based on the result of the investigation presented physical properties of the in-ground in the plane manner using Kriging method, one of geostatistics methods. Also, the comparison of converted N-value measured by the NSWS and converted N-value estimated by Kriging method is presented to examine the composite capability and benefit of Kriging method and NSWS for simplified on-site verification and re-measurement for reaffirmation (diagonal measurement) in the confined detached house ground.

Numerical simulation for the movement of cesium-137 in grounds

Fukushima Dai-ichi nuclear disaster occurred by Great East Japan Earthquake in 2011. As the result, a lot of radioactive substances was discharged to atmosphere and deposited in surface of ground by rain. In damaged area, decontamination has been conducting. Usually decontamination for the ground is digging out for 5 cm from the surface of the ground, but its safety and validity is apprehended. In this study, permeation behavior analysis of radioactive substance in the ground was carried out in order to prepare new decontaminations. Specifically, behavior and advection-dispersion analysis was conducted by advectiondispersion equation was embedded a term that considered half-life. As a result, it is found that this analysis method has enough validity by comparing analysis result with result on the spot. Furthermore analytic evaluation for the current decontamination is performed.

Life cycle assessment on recycling of construction sludges in geotechnical engineering fields

Although waste recycling has been promoted in response to increasing environmental awareness in Japan, its marketability is being questioned due to the recycling cost. The ultimate goal of waste recycling is to reduce the environmental load. In this paper, we examined the evaluation method for social environmental efficiency to socially evaluate waste recycling, by incorporating environmental load as an environmental cost in addition to the direct cost. The social environmental efficiency evaluation including consideration of uncertainties is conducted, because waste recycling involves various uncertain elements. As the results, the social environmental significance of construction sludge recycling can be evaluated quantitatively while focusing on the particular construction sludge with a lower recycling rate.