Approximately 40 years have passed since impermeable liner as first used in leakage insulation works on solid waste disposal sites. Today, it is the most common impermeable material with a great many proven records. Meanwhile, compared with the knowledge on the material characteristic of liner sheet, knowledge concerning its application on solid waste disposal sites as a impermeable material has been up to now somewhat deficient. In this report, starting with the real situation of deterioration of seepage control liner on actual waste disposal sites and suggestions for a method to predict its durability, development of a highprecision method which was introduced for inspection of the liner sheet joints. This method uses remote sensing technology at the time of installation of the seepage control liner, as well as a rapid management method that covers a wide area of liner sheet. In addition, problems inherent to waste disposal sites and research topics concerning seepage control liner are described.

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The strength of the Kanto loam falls by agitating. Then, it is necessary to apply stabilization in order to be reused. There is short fiber-reinforced soil in one of the techniques for reinforcing the soil. If the Kanto loam can be reinforced with a short fiber, it will lead to reuse of the construction generated soil. However, research of short fiberreinforced soil is targeting sand in many cases. Therefore, the mechanical characteristic of short fiber-reinforced soil using cohesive soil is not clarified. In this study, intended for short fiber-reinforced soil using Kanto loam in the base material, is performed unconfined compression test, the large box shear test, and were discussed reinforcing effect.

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In the authors’ laboratory, the development of a completely new type of embankment by using heavy steel slag as the fill material has recently been underway with missions to achieve low-cost, environmentally tender and high resistance against earthquakes and heavy rainfalls. In the image of this reinforced embankment, geotextile sheets are placed in the compacted steel slag so that a high earthquake resistance, together with significant flexibility against deformation of the foundation soil may be achieved. However, little information is available as to the type of geogrid appropriate in the steel slag as well as the in-slag shear characteristics of the geogrid. In this paper, a comparison of pull-out shear force resistance of bonded/extruded types of geogrid is made in pull-out test in the laboratory.

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This study was intended to clarify the compressive property of soils mixed with deformable particles. Generally, in the case of soil mixed with deformable particles such as rubber, it is thought that two more compression components, one is compression of the deformable particle themselves and the other is the following reduction of pore space, are added to the ordinary volumetric compression. Therefore, a series of one-dimensional compression tests was executed using rubber and aluminum tips to estimate these compression components. As a result, it was found that the latter compression component was far larger than the former. And it was also confirmed that the rubber tips were hardly compressed, though the volumetric compression of rubber tips were appeared in an early stage of compression.

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In this study, the difference in triaxial shear property of Liquefied Stabilized Soil (LSS) mixed with fiber material cured in laboratory and at field was investigated. A series of Consolidated–Undrained triaxial compression tests under the conditions at constant strain rate, constant deviator stress (partial creep test), and changed strain rate during monotonic loading have been carried out for both specimens of LSS mixed with fiber material amount of 0 and 20 kg/m3 prepared by trimming LSS retrieved from a model ground by block sampling and cured in laboratory at curing time of 28 and 56 days, respectively. Based on the test results, it was found that the maximum deviator stress, qmax in q~ε_a curve of LSS mixed with fiber material cured at field tend to be larger than that cured in laboratory, and the brittle property of LSS after the peak in q~ε_a curve has been improved to ductile property by the addition of fiber material even in field.

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In this study, we tried to develop a cost-effective method of improving soil with high water content utilizing cold climate and the large sandbags made of geotextile. We have put the dredged soil with high water content into large sandbags and made various measurements, such as water content and frost depth. From the results, we confirmed that the water content of the dredged soil was reduced from the initial value of 420% to the value of 140% in one year.

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We have developed the pile slab track soil embankment using the material of poor quality. This embankment has high performance to reduce seismic settlement of concrete slab confirmed by the shaking table test results of the 1/10 scale model of pile slab embankment and the large gabion method by actual size loading tests. This paper describes design method of the pile slab track soil embankment checked based on the knowledge gained from the experimental results.

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A bentonite mixed soil (BMS) layer used as a component of the barrier system in the landfill may crack owing to a local subsidence of base ground. In order to verify a function of geonet (GN) to prevent a crack from growing in the BMS layer, first, pull-out tests of GN from a compacted BMS layer were conducted to determine their frictional resistances. Then In-situ local settlement tests for the BMS barrier model with a 50 cm in thick were conducted to observe deformation behavior and occurrence of crack. Last, a run-out length of GN over a concerned cavity was calculated based on elastic model. As the results, it was found that the cracked BMS layer underlaid with the GN did not fall down into the cavity while it without GN fell down thoroughly. A run-out of 50 cm of GN was thought enough to keep the pull-out force induced by deformation.

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This research examined the pull-out resistance mechanism using a different form geogrid by carrying out a series of pull-out test, and investigating the influence of arch action on a test result. Furthermore, the increase of the pull-out force by arch action was presumed by carrying out pull-out tests which changed the length of pull-out box. As a result, it turned out that pull-out resistance mechanism is based on the form of geogrid, and pull-out resistance of geogrids which have rough surface and small aperture is overestimated because of the influence of arch action. On the other hand, in the case of HDPE the influence of arch action is small, since pull-out resistance is mainly passive pressure which was occurred by ribs.

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Compared with conventional type cantilever retaining walls (RWs), Geosynthetic-reinforced soil (GRS) RWs are much more cost-effective exhibiting lower life cycle cost. When seismic design is performed, this advantage becomes more obvious enhancing the construction of GRS RWs. On the other hand, no-seismic-design policy is often employed based on such experiences that a number of soil structures that were not seismic-designed survived earthquakes in the past and that restoration of damaged soil structures is easier than RC/metal structures. These unexpectedly better performance of soil structures is due mainly to the redundancy involved in design. However, such redundancy decreases or even vanishes by poor construction, heavy/prolonged rain, unexpected scoring/excavation in front of RW etc., which increases the number of collapse. The roles of redundancy are illustrated by analyzing a GRS RW having full-height rigid facing that did not collapse by seismic loads that were substantially higher than the design seismic load during the 1995 Great Kobe Earthquake.

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This paper discusses a tsunami-resistant structure with geogrid. The results of flume tests to investigate the effect of the structural shape on tsunami-energy dissipation showed that a structure with slope on the upstream side and vertical face on the downstream slide is the most resistant. A geo-structure with a geogrid gabion system is proposed. The effectiveness of the proposed system was confirmed through flume tests performed under various flow conditions.

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Conventional type coastal dikes consisting of unreinforced backfill covered with concrete-blocks are designed to resist against wave forces by the self-weight of the concrete-blocks while dissipating the uplifting water pressure via a pervious layer underlying the blocks. However, continuous waves, like tsunami bore, generate dynamic positive wave pressure in the previous layer underlying the blocks that uplifts the blocks. In addition, the shoulder-blocks on the downstream slope are lifted up and dragged away by negative water pressure generated around the top of slope by overflowing tsunami current. In order to alleviate these structural defects, a new type coastal dike is proposed, which integrates concrete-blocks using geotextile to an underlying low-permeable soil-cement layer. The results of hydraulic model tests indicate that the new type dike has a high stability against tsunami bore by restraining the generation of dynamic positive wave pressure inside the backfill, while resisting against uplift force by anchoring the concrete -blocks with geotextile to stable backfill and connecting each other via a joint structure.

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Many earth structures such as railway embankment are damaged by the Tsunami generated by Pacific coast of Tohoku Earthquake. These damages were mainly caused by the prolonged overtopping of Tsunami. However, the detail mechanism of the erosion of embankment body as well as the influence of the erosion of supporting ground to the entire stability of the embankment have not been understood. In this study, therefore, a series of hydraulic model tests which imitates the prolonged overtopping phenomenon were carried out. The experiment revealed that the erosion speed decreased by arranging geotexile in the embankment. Furthermore, partial ground improvement can effectively decrease the influence of supporting ground erosion to the stability of embankment

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The authors examined the most suitable tide wall shape for tsunami energy reduction. As the results, we understood that the steep slope was more effective than the traditional sea wall for the tsunami energy reduction. In this study, we examined mechanical stability of the steep slope tide wall reinforced by geotextiles for overflow tsunami. At first, we installed pressure gauges in the rigid model and measured horizontal tsunami pressures. We considered the measured forces to the external forces and designed the tide walls which changed some parameters. We carried out tsunami model experiments to examine the stability of designed tide wall model. As the experimental results, we got the some important knowledge to design a tenacious tide wall.

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Persistent reinforced seawall against tsunami consists of a covering concrete block and a cement stabilized soil in the back side of the block, and both side is integrated by geotextile. The characteristics of the seawall are as follows; 1) inhibit water pressure acting on back side of the block and 2) increase a resistance against haydraulic uplift acting on the block during overflow of tunami. Authors developed a precast concrete block in which the geotextile was directly inserted in the concrete block for use as the covering of the seawall. This paper reports characteristics and performance of the geotextile inserted concrete block, and constructability of the seawall using the developed concrete block.

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Many dike failures by the torrential downpour and rising river level are reported recently. As one of the key factors, the air behavior including the enclosure and consequent blow of air phase were observed in the saturation process of dike, which accelerated the failure of dike with air blow and resulting cracks on the surface. Therefore, it is needed to establish the counter measure method to prevent the degradation of dike by air blow. This research by the model test of dike failure under artificial rainfall and water level raising examined the effect of breathable-water proof sheet and drain as counter measure method on controlling the enclosure and blow of pore air in a dike. From the test results, the proposed counter measure method can restrain the accumulation of air phase and reduce the water level within the dike. As a result of this research, the usefulness of the breathable–water proof sheet and drain became clear, which can be greatly helpful to the disaster mitigation.

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The lattice-frame-reinforcement-sheet, which was developed as a soil stabilization sheet, has been applied to soft ground for the purpose of soil improvement. It was also expected that the lattice-frame-reinforcement-sheet was capable of reducing liquefaction damage of soil structure. Therefore, the authors have carried out a series of centrifuge tests with the lattice-frame-reinforcement-sheet in order to evaluate seismic performance of diverselyreinforced embankments on a liquefiable foundation. As a consequence, it was found that the lattice-framereinforcement-sheet had a great effect on preventing the differential settlement of embankments and the suppression of crack generation after the liquefaction.

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Image analysis on the deformation of segmental geosynthetics reinforced soil retaining walls (GRS walls) was carried out based on the results of dynamic centrifuge model tests. Although the deformation mode of reinforced area of the GRS walls was classified into shear and stretch deformation, the shear deformation was predominant. The value of the residual displacement calculated from the shear strain inside the reinforced area was almost equal to the actual measurement value. The vertical distribution of the shear strain showed an arcuate shape. In the reinforced area, the local deformation at the part close to geosynthetics was not similar to that at the part without geosynthetics.

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Abutments, box culverts, and other concrete structures are generally supported by soil structures formed with fill and backfill. Soil bearing such structures below their junction often develops uneven settlement, which causes deflection and adversely affects the evenness of pavement on the soil. In this study, we constructed test pavement having a Geocell layer on the boundary between fill and slab concrete to reproduce the condition previously mentioned and performed a driving test to confirm Geocell’s pavement deflection suppression. After the test, we removed the Geocell from the test pavement and performed a tensile test on the pavement to measure its material degradation accumulated during the driving test.This paper discusses the method of the experiment and its results.

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Asphalt pavement has structural problem that is low durability against traffic loads and environmental interaction. In Western countries, reinforcing technologies using geosynthetics have often been used to reinforce the base layer to improve the stability. On the other hand, studies on the application of soil reinforcing technologies such as geosynthetics to pavement systems are limited in Japan. In the present study, the effects of geogrid reinforcing method on the residual deformation characteristics of flexible pavement structure are examined. From the results of laboratory wheel loading tests on asphalt pavement, it was confirmed that arranging geogrid in the subbase has advantage to reducing the residual settlement caused by heavy traffic load. Well-compaction is important to increase the reinforcing effects.

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In a cold region, it is reported that reinforced soil walls covered with concrete facing panels or steel frames can collapse by frost heaving force. In this research, we have observed over two seasons of freezing and thawing behavior of reinforced soil walls built at the site of the Kitami Institute of Technology. The results show that one wall using geocells and geogrids showed no deformation that may lead to destabilization in the future compared with another wall using steel mesh forms and geogrids. In addition we have performed laboratory tests to check the geogrid for deformaion caused by the surrounding soil freezing and thawing. The test results suggest that the geogrid has a low possibility of having a partially significant elongation under low confining pressure.

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For reinforced soil walls, the judgment of the healthy-unhealthy is usually carried out by the uniform control value, such as wall displacement. However, it is believed that many reinforced soil walls are stable with some deformation with age. The authors have proposed a maintenance method not monitoring a uniform control value but judging the presence or absence of functional deterioration factors. In this paper, we report the result of the various measurements by applying the proposed maintenance method in the 6m height geogrid reinforced soil wall model with cavity.

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In this research, we have tried to make a berm ditch using a polypropylene drainage material that has a threedimensional mesh and spiral structure featuring both high strength and flexibility. We have actually constructed the ditch and made various measurements, such as soil temperatures and ditch displacement, over two years. From the results, we have confirmed that the berm ditch developed in this research is not damaged by frost heave since it is able to follow the frost heave and thaw settlement of the ground. In addition, we have conducted a simple transmissivity test and found that the material maintains its water transmissivity performance after two years.

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This study aims to investigate the reinforcement mechanism and its expression factor exerted by soft plastic in the landfill which contains many soft plastics. First, geotechnical tests were performed in order to compare the index properties between landfill sample and decomposed granite soil. Then, the tensile strain of soft plastic arranged in both samples was measured under compression process. The test result showed that the tensile strain of soft plastic arranged in landfill sample was more than 10 times that in decomposed granite soil. It is implied that uneven surface of soil particle along soft plastic in landfill sample was larger than that in the decomposed granite soil, since the landfill sample contains various types of granules which have an irregular shape. As a result, the soft plastic was elongated largely and larger tension force was generated on the soft plastic in landfill sample.

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The health damage by the diffused radioactive cesium from the Fukushima disaster to the inhabitants has been deeply concerned. Therefore radiation decontamination works for residential houses and their vicinity have been conducted. However, even after decontamination works, the periphery of forests faces potential risks of re-rising radioactive dosage brought by wind and rain. Last year we proposed a method that geosynthetics with an absorbing function of radioactive cesium laid on the ground of the decontaminated areas aforementioned restrains the transition of radioactive cesium1). This report presents the one-year-after results: Effectiveness of radioactive cesium absorbing function of the method to restrain radioactive cesium is confirmed by increase of the amount of radioactive cesium in the geosynthetic materials.

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In a closed water body, nutrient salts of nitrogen and phosphorous flow from rivers, accelerating eutrophication and thereby causing water pollution and offensive odors. This paper first presents the outline and features of our developed zeolite functional paper which can adsorb cations such as NH4+. Furthermore, we propose a simple purification unit made of the zeolite functional paper and geosynthetics that can be installed easily in small channels. Next, a durability test of the zeolite functional paper to a water stream and adsorption tests using the miniature of the simple purification unit to aqueous solution including NH4-N are discussed. These results clarify that the applicability of the simple countermeasure against eutrophication is expected.

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This paper examined the utilization of bamboo that has been cut down in order to solve the standing problem of bamboo forest. Focusing on water absorptivity of bamboo chips and flakes, we consider improving the high water content soft clay such as dredged bottom mad. As a result, we found that there is sufficient improvement effect on bamboo chips and flakes. Improving effect would be affected by the differences in the absorption properties of bamboo chip and flake. In addition, the combination with solidification material, it is effective to reduce the solidification material addition rate. And, the addition of solidifying material is found also affects the decay of bamboo in improved soil.

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The Sanriku Railway Kitariasu-Line suffered enormous damage from the 2011 off the Pacific coast of Tohoku Earthquake, is under repair between Omoto and Tanohata in order to reopen the whole line in April 2014. In this restoration, Geosynthetic-reinforced soil (called GRS) integral bridge was applied to three bridges, one for river crossing culvert and two for over road bridges. This paper reports execution management of GRS integral bridge.

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Haipe-Sawa bridge of The Sanriku Railway Kitariasu-Line was suffered enormous damage from the tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake. The repair of this bridge from outflowing by the tsunami, Geosynthetic-reinforced soil integral bridge (called, GRS integral bridge) was applied. The superstructure, 60m (33m +27m) length, has continuous SRC through girder to ensure the building limit of the cross road. To apply GRS integral bridge, measurement has implemented. This paper reports the results and study of the measurement at the under-construction and post-construction.

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GRS integral bridge is applied for the first time as a railway structure in Hokkaido Shinkansen, and long-term and under-construction measurement are being carried out.From the characteristics of the GRS integral bridge, tensile displacement to geotextile occurs repeatedly by forced displacement due to expansion and contraction of concrete action.In addition, the possibility of tensile displacement to geotextile in the displacement-to-back direction of the approach block is caused to act is concerned.In this paper, to organize the data obtained from the long-term dynamics measurement, for the displacement situation back embankment and stretching behavior of the bridge part that affects the tensile displacement of geotextile , and the behavior of the actual structure was discussed.

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