The number of irrigation pipelines buried without withdrawing existing open channel is recently increasing due to the number of irrigation pipelines buried without withdrawing existing open channels is recently increasing due to aging facilities and the conversion from open channels to pipelines. In this study, the lateral loading experiments on buried pipe were conducted to investigate the effectiveness of existing channel walls on thrust restraint for bends of pressure pipelines and the effect of geogrid on reinforcement of channel walls that are not suitable for use as thrust restraint. The experimental results show that the lateral resistance force increased when channel walls were on the passive side of the buried model pipe. In addition, channel walls with geogrid were also worked to enhance the lateral resistance force to the displacement of the pipe.

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We have developed a vibration-reducing material for reducing the vibration that occurs during the running of heavy construction machinery. This vibration-reducing material is a pad made of polyolefin elastomer with 3D mesh structure. In addition to its vibration-damping effect, this material has excellent compression-resistant and vibration reducing performance due to a special molding process. In full-size tests, we have confirmed the vibration-reducing effect of the material on the running vibration from three types of heavy construction machinery. We have also confirmed on-site the durability and vibration-reducing effect of the material on the running vibration from a large scale piece of heavy machinery, a 350-ton class crawler crane.

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Earthquakes may cause road surface bumps to form near the boundaries of box culverts in road embankments. Such earthquake-induced bumps block emergency vehicles, such as ambulances, and therefore, have been a major seismic issue for the maintenance of road embankments. However, there are few clear maintenance standards in place despite the ubiquity of such road structure containing box culverts across embankments. Research on their economic efficiency is also sparse. Against this backdrop, this study aimed to investigate the effectiveness of road bump countermeasures which utilize geotextiles and are potentially low-cost. Experiments using simplified models allowed for visual inspection of the difference in effectiveness between the proposed countermeasures and the conventional concrete slab method.

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Liquefaction countermeasure methods for detached houses are expensive, and low-cost methods have not yet been developed. Therefore, there is a need to develop inexpensive and safe liquefaction countermeasure methods for detached houses on the ground with a thick liquefied layer. The objective of this study is to develop a method that lays a low stiffness geotextile that the end restrained to the ground. In this experiment, the focus was on the hammock effect of the end-restrained geotextile, and the pulling experiments were conducted on the type of the ground to be properly restrained and the method of end-restraint. Moreover,1G-field shaking table model experiments were conducted to verify the effectiveness of the amount of sinking during liquefaction by means of end-restrained geotextiles in reducing.

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To investigate the effectiveness of soil nails in repairing damaged geogrid reinforced soil walls (GRSWs), a series of model tests on GRSWs was carries out to simulate earthquake damage by the first tilting, repair with soil nails, and the second tilting to estimate seismic stability of the repaired GRSW. The results showed that the seismic resistance of the damaged GRSW was improved by adding soil nails. Effectiveness of adding soil nails in improving the seismic resistance was found to depend on the length of the soil nails and the degree of damage to the GRSW.

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In this paper, the effect of geotextiles laid during construction using the deep-mixing processing method in order to decrease the consolidation settlement of soft ground was investigated. The experiment was conducted indoors using the deep-mixing processing method and the ground’s settlement characteristics were compared with and without the use of geotextiles. As a result, it was found that the tensile strength of geotextiles occurs in proportion to the embankment thickness. Additionally, it was revealed that the vertical earth pressure of soft ground laid with geotextiles implemented was controlled at a maximum of around 0.7 times the results found in comparison with the conditions where geotextiles were not implemented. Furthermore,the laying of geotextiles decreased the looseness and surface settlement of the embankment.

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With the goal of development of artificial geomaterial that is resistant to disasters in this study, a series of unconfined tests were carried out to investigate reinforcement effect of mixture of short-fiber materials on mechanical properties of short-fiber reinforced soils. Hydraulic experiments were also conducted on an experimental embankment consisted of a layer of the short-fiber reinforced soil. Short-fiber materials were applied used newspaper and short polypropylene fiber, respectively. As a result, the unconfined compressive strength of the short-fiber reinforced soils increased with increasing a degree of compaction of that. In addition, the mixing of short-fiber material to soil had a great reinforcement effect on the overflow erosion resistance of the reinforcing embankment.

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This study investigates the phenomenon of increased earth pressure due to thermal expansion and contraction of girders of integral bridges. Model experiments were conducted using aluminum rod–laminate ground to apply cyclic horizontal loading. Normal and GRS (Geosynthetic Reinforced Soil) integral bridges were used for the experiments, and three patterns of cyclic horizontal displacements—only the active side, both the active and passive sides, and only the passive side—were applied to simulate different seasons when the girder was integrated. The experimental results showed that the reinforcement could reduce the increased earth pressure. The earth pressure at the time of displacement of the passive side increased as the ratio of the displacement of the passive side to the displacement of the active side in cyclic loading increased, regardless of whether reinforcement was used.

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A new slope protection work has been developed that also adds a heat insulating function to slope protection work composed of two layers of geocell with different filling geomaterials. In this study, we conducted full-scale slope tests on five cases with different insulation measures and greening methods. In addition, based on the measurement results of full-scale slope tests, we estimated the maximum frost penetration depth according to the freezing index in each case by heat transfer analysis. As a result, it was clarified that this slope protection work can achieve both heat insulation and greening by installing a heat insulating material between the crushed rock and the sandy soil.

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The authors study geosynthetic-soil reinforcement techniques for the emergency and rehabilitation roads in the event of disasters. This paper reports the results of a physical modeling investigation on the reinforcement mechanism of geocells under vertical loading conditions. Load-settlement relationships for four cases of model loading tests and the results of displacement field measurements of the model ground using the PIV method are shown. As a mechanism of geocell reinforcement, the effect of geocell to constrain the ground horizontal displacement is clarified.

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RRS-s method that combines geocells, soil nails and an additional impervious sheet has been recently developed in the aim of improving further and cost-effectively the stability against heavy or prolonged rainfalls of conventional RRS embankments that combines geocells and soil nails only. To investigate and confirm the workability of the proposed method as well as the overall impermeability including the one of the sheet junction parts (wrapping), full-scale field trial construction tests have been conducted with continuous monitoring of the slope water content. Results are reported in this paper and confirm that an efficient construction is possible while impermeability effects could be confirmed from the first 7 months of monitoring which included relatively high amount of rainfalls.

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According to a dynamic centrifugal model test of an abutment with EPS backfill, it has been reported a　large force caused by collision of slabs acts on the abutment during an earthquake. This report presents the results of a 3-dimensional FEM analysis to confirm this phenomenon and to evaluate the effect of the force on the abutment. As a result, it was confirmed: the force acting on the abutment by the slabs is generated when the inertial force is directed to the back of the abutment; the behavior is similar to that of the past test; the effect of the action on the abutment was greater due to the inertial force than the earth pressure; and replacing the slabs with EPS partly is effective in mitigating the force acting on the abutment.

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It is difficult to backfill and compact the narrow space in the bottom side of the pipe and ensure sufficient quality. Insufficient backfilling may cause unexpected deformation and stress concentration in the pipe. In this study, a method of installing EPS as a pipe foundation was proposed, and its effectiveness was examined through a model experiment using 300 polyethylene pipes. The results showed that, when EPS is installed, depending on its geometry, slightly larger strains may occur at the bottom of the pipe or at the contact point between the pipe and EPS, but these strains are significantly smaller than the strain concentrations caused by insufficient backfilling and are not large enough to cause pipe failure, indicating the effectiveness of the EPS as a pipe foundation.

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RRS method has been developed for improving cost-effectively the stability of existing embankments against large earthquakes and rainfalls by combining geocells and soil nails. In the aim to improving further the stability of RRS embankments against rainfalls along with their cost-effectiveness, it is proposed to use additionally an impervious sheet. By effectively restraining the infiltration of rainwater into the embankment, the number of soils nails can also be reduced in comparison to conventional RRS embankments. During the sheet installation, some heterogeneities inevitably appear (junction parts, damaged parts by anchor pin fixation) so that a series of rainfall laboratory tests and numerical analyses have been conducted to investigate their permeability properties.

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A testing apparatus was developed to measure the permittivity of geotextiles under a wide range of hydraulic head difference conditions. Its validity was investigated experimentally, and an evaluation method of permittivity based on Izbash's law which is for non-Darcy flow in highly permeable porous media was discussed. In this paper, the experimental results for four geotextiles with different thicknesses are reported and considered. The relationship between the permittivity parameters and the thickness of geotextiles is discussed based on the proposed method.

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The non-uniformity of unit area mass, initial thickness and initial void ratio was investigated for 620 layers of specimens cut from a sheet of non-woven geotextile with 1.0 m wide and 1.5 m long. It was shown that it is possible to predict the distribution of void ratio, which is an important parameter to evaluate permeability of non-woven geotextile, using the distribution of unit area mass. And then, compression test was carried out for 15 specimens extracted by considering the normal distribution of initial void ratio of 620 layers. The confidence interval of void ratio in compression process was calculated by assuming void ratio in every loading pressure is normal distribution. Furthermore, the change in the distribution of void ratio during compression process was visually shown.

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For the purpose of examining the applicability of optical fiber sensor in the temperature distribution estimation and the leachate leakage detection of the impermeable sheet in a solid waste landfill, the optical fiber was wired to the model of the landfill slope with impermeable liner, and the temperature measurements using optical fiber sensor were carried out. As a result, Raman measurement is considered to be sufficient in the temperature distribution estimation. Regarding the detection of leachate leakage on the slope, Raman measurement is difficult due to its low spatial resolution, and Brillouin measurement with high spatial resolution is possible. The effectiveness of making the optical fiber wiring perpendicular to the slope direction was shown.

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