Journal of Japan Society of Civil Engineers, Ser. C (Geosphere Engineering)
Online ISSN : 2185-6516
ISSN-L : 2185-6516
Current issue
Displaying 1-8 of 8 articles from this issue
Paper (In Japanese)
  • Junichi YAMANOBE, Munehito ENDO, Kazuhito KOMIYA
    2022 Volume 78 Issue 2 Pages 60-71
    Published: 2022
    Released on J-STAGE: April 20, 2022
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     In this study, the effects of curing temperature and curing time on the unconfined compressive strength of cement-stabilized soil were investigated in a laboratory test. A simple method was proposed for curing cement-stabilized soil at temperatures of 80°C‒100°C for construction sites using a retrofitted commercial pressure cooker. The analysis was conducted using cement-stabilized soil samples containing various amounts of fines and cement to obtain fairly low scatter with a strength ratio within ±0.1 in magnitude. The strength ratio defined as the unconfined compressive strength of cement-stabilized soil specimens cured at 100°C for one day against those cured in water at room temperature for 28 days. Next, a prediction method including a series of procedures such as soil sampling, specimen manufacturing, curing and unconfined compression testing was proposed to estimate the 28-day strength of cement-stabilized soil at construction sites using the strength ratio. To investigate the accuracy of the proposed prediction method, in-situ tests were conducted to improve the ground at field sites composed of sandy soil and volcanic cohesive soil.

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  • Yudai FUJIE, Hiroyuki HARA
    2022 Volume 78 Issue 2 Pages 72-82
    Published: 2022
    Released on J-STAGE: April 20, 2022
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     A white layer, containing magnesium hydroxide (Mg(OH)2) as the main component may be deposited on the surface of cement treated soil under saline condition. This layer has the function of protecting cement-treated soil from deterioration due to seawater. In this study, in order to clarify the conditions for the deposit of Mg(OH)2 layer, the effects of magnesium concentration in seawater and the pH of cement-treated soil were investigated in laboratory tests. It was observed that the Mg(OH)2 layer was deposited when the pH of the cement-treated soil was above a certain value, regardless of the soil type. In addition, pH value of the treated soil which the Mg(OH)2 layer was deposited varied depending on the magnesium concentration in the contacting seawater. The deposition of Mg(OH)2 layer depends on the range of pH (12.29-12.81) and the concentration of magnesium (50-1750mg/L).

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  • Osamu TAKAHATA, Takuya HARADA, Shinji MIYAGUCHI, Mitsuru KUWABARA, Mar ...
    2022 Volume 78 Issue 2 Pages 83-95
    Published: 2022
    Released on J-STAGE: May 20, 2022
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     The Neogene Sedimentary Rock containing heavy metals is distributed over the southern coastal area in Fukushima. Therefore, leakage measures had been required for using its rock containing naturally derived heavy metals into embankment, etc. in public works by regulation standard from 2010. However, these rocks and soils have been used for road embankment in many areas up to now without serious problem, even though there is a possibility that heavy metals leakage occurs in some conditions by material characteristics. This study evaluated the effectiveness of retarding acidification caused by a soil covering and a degree of compaction based on the results of outdoor exposure tests using pilot-scale road embankment constructed of the Neogene sandstones.

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  • Yoshihiro TSUNEKAWA, Toshinori SAKAI, Hiroaki MIYATAKE, Masuo KONDOH
    2022 Volume 78 Issue 2 Pages 96-115
    Published: 2022
    Released on J-STAGE: May 20, 2022
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     Ground anchors help to stabilize slopes by transferring the load to the anchor. In some cases, the anchor head can be transformed or the anchor body can bend, which can cause loading in the shearing direction and affect the anchor performance. However, there has not yet been sufficient investigation of the influence of the anchor transformation on the restraint function because determining the transformation of the anchor in the unobservable underground section is challenging. Therefore, in the present study, the anchor load was observed, and a fiberscope was used to investigate a landslide site where anchors had fractured. As a result, it was possible to determine how the anchors fractured and transformed in the ground. The influence of this transformation on anchor performance was considered.

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  • Takayuki SHUKU, Shinya YAMAMOTO
    2022 Volume 78 Issue 2 Pages 116-127
    Published: 2022
    Released on J-STAGE: June 20, 2022
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     This study proposes an unified approach to solve a design optimization problem in geotechnical engineering using quantum annealing (QA). This paper shows how to formulate a design optimization problem as a quadratic unconstrained binary optimization problem (QUBO) that required in implementation of QA. Then the performance of the QA was presented by comparing QA with existing methods such as simulated annealing (SA) and random sampling through a numerical example. In addition, quantum Monte Carlo simulation (QMCS) was newly proposed based on the characteristics of QA, which is revealed in the numerical test, and a numerical example of design optimization of pile foundation considering variability of geotechnical parameters was presented.

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  • Satoru HARASAKI, Hideo KOMINE, Shigeru GOTO, Hailong WANG, Daichi ITO, ...
    2022 Volume 78 Issue 2 Pages 128-139
    Published: 2022
    Released on J-STAGE: June 20, 2022
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     The 2011 off the Pacific coast of Tohoku Earthquake affected severe damage to nuclear power plant in Fukushima. In the decommissioning of Fukushima Daiichi Nuclear Power Plant, fuel debris retrieval is a hard project because of scattering of radioactive materials, leakage contaminated water, and radiation exposure. To tackle those problems from the point of view of soil mechanics, super heavy bentonite slurry has been researched and studied. In the process of decommissioning, super heavy bentonite slurry may contact radioactive materials, and therefore, used slurry must be disposed as radioactive waste. However, disposal system of used super heavy bentonite slurry has not been established. Considering present radioactive waste disposal in Japan, it is desired that used slurry volume can be reduced and disposed according to the radiation level. The authors are attempting to built a disposal system with focusing on centrifugation in this study. This study measures the vertical distribution of constituent materials in centrifuged super heavy bentonite slurry by using methylene blue adsorption test. Results show following conclusions: i) The products of relative centrifugal acceleration and separation time may be essential element govering the amount of separating and collecting constituent materials from super heavy bentonite slurry by centrifugation. ii) Centrifugation is effective on separating and collecting of barite from super heavy bentonite slurry.

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  • Ryota OHASHI, Shin-ichi NISHIMURA, Minoru KANESHIGE, Toshifumi SHIBATA ...
    2022 Volume 78 Issue 2 Pages 140-152
    Published: 2022
    Released on J-STAGE: June 20, 2022
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     Recently, 3-dimensional survey has been developed with use of UAV, and the rebuild of the 3-dimensional shape for structures has been easier. Despite such development of the technic, it is not imported to the design for the geo-structures. In this study, for the purpose to incorporate the 3-dimensional survey technic into the design, two earth-fill dams are surveyed 3-dimensionally by the drone, and its 3- dimensional finite element models are made based on the survey results. Finally, the FEM models are applied for the seismic response analysis, and the structural weak locations inside the earth-fill are searched. The rigidity inside the earth-fill is interpolated based on the sounding results. As the sounding methods, the Swedish weight sounding (SWS), and the piezo cone penetration test (CPTu) are employed. As the interpolation method, the 3-dimensional kriging method, which is one of the geostatistical methods, is used. According to the analytical results, the location of the high acceleration, or high shear stress inside the earth-fill, has been identified 3-dimensipnally.

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  • Kaoru KOBAYASHI, Kazunobu MUTSUMOTO, Youhei KOYANO, Keiya MATSUURA, To ...
    2022 Volume 78 Issue 2 Pages 153-164
    Published: 2022
    Released on J-STAGE: June 20, 2022
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     Capillary barrier (CB) is a tilting soil layer system that is composed of a finer soil layer underlain by a coarser soil layer that can prevent salt accumulation in the semi-arid region. In the design of CB, it is necessary to predict the diversion length of CB and consider the unsaturated permeability behavior in long-term soil by numerical analysis. However, the parameters required for numerical analysis, such as the pore connectivity coefficient, especially that of coarse grained soil, are very important to set unsaturated permeability coefficient, but its value is almost not clear. In this paper, the water movement amount in CB of the fine soil layer and the crushed shell layer (the substitute of coarse soil layer) are measured by soil moisture sensors with one-dimensional cylindrical devices. Based on the real-time measurement results, an inverse analysis is carried out on HYDRUS to identify the pore connectivity coefficient of crushed shell particles. Based on the above process, the water movement results of the capillary rise block experiment of CB using crushed shell particles are compared with the analysis results using the pore connectivity coefficient of crushed shell particles, and the validity of identified pore connectivity coefficient is confirmed.

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