Geosyntheics are widely and effectively used for the geotechnical barrier as liners in the waste landfill and the contaminated site． Basic concept and applicability of geosynthetics for the geotechnical barrier are summarized．The most important point of the geosynthetics usage is keeping the good performance of the materials． Practically applied sites using newly developed geosynthetics liners are examined with their advantageous points.

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A series of tilting tests and shaking table tests were carried out so as to develop an aseismic countermeasure for masonry retaining walls using collapse prevention net and soil nailings. Tilting tests were carried out so as to investigate into the reinforcement mechanisms and the effect of backfill stability on the reinforcement effect. Shaking table tests were carried out to understand the resistant mechanisms in dynamic field. Results from a series of model tests clarified the resistant mechanism. It was also found from the tests that collapse prevention net was highly effective in reducing horizontal displacement by restricting the blocks with soil nailings as well as preventing the collapse of masonry retaining walls. In additions to the above, a design methodology was also proposed by reflecting the resistant mechanism revealed by the model tests.

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For evaluating the stability of river dyke, it is important to understand the influence of the behavior of pore-air on the water seepage in unsaturated soil, due to the possibility of pore-air trapped and compressed in the dyke. In this paper, the pore-air behavior in unsaturated soil is examined by the rainfall and river water infiltration experiments in one-dimension. As a result, it was recognized that the generation of pore-air pressure was attributed to the reduction of air permeability at the soil surface by the rainfall, and that the local crack in the soil occurred due to the larger pore-air pressure. And then, it was shown that the pore-air pressure generation was prevented in while keeping the air permeability at the surface by using the breathable - waterproof geotextile.

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Geotechnical engineers are increasingly concerned with embankment failures induced by heavy rainfalls. In an attempt to reduce the risk for embankment failures, geotechnical engineers have recently proposed an L-shaped geodrain system with which seepage water flow into the embankment may be prevented even in the event of heavy rainfalls. In the conventional research, the vertical drain material has been arranged to form a straight line. In geotechnical engineering practice, however, the vertical drain may conveniently be mounted in a form of alternate arrangement. Moreover it is assumed that water level of the side of embankments is always constant. In this paper, the effects of water level repression in embankment is discussed when the vertical drain material is set to be alternate arrangement. And also the applicability of a simple estimate equation is examined. The effects of water level repression at the side of embankments are investigated as well.

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Since a river dike located at the downstream where urbanization has been in progress is composed of sandy soil consisting mainly of soft and fine particles, the river dike is considered to be easily damaged by pore air that has been enclosed within the dike. Therefore, the establishment of counter-measure method which prevents degradation of the dike by air blow is pressing need. So, this research examines the effect of the breathable–water proof sheet as counter-measure method which controls enclosure of pore air in a dike. According to the previous research to the breathable–water proof sheet, the seepage prevention effect and the mitigating effect of pore air pressure were confirmed from the model tests. We conducted in-site test on a real dike. As a result of artificial rain fall experiment in the dike, the usefulness of the breathable–water proof sheet became clear from the response of a soil water meter and specific resistance monitoring.

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Rockfall protection soil wall, which it can absorb the rockfall energy from 100 to 3000kJ, has been widely applied to many rockfall protecting works. Conventionally, the wall is designed based on the limit equilibrium method, but the performance based design considering the deformation of the wall based on the experimental data is proposed in recent years. In order to rationalize the design method of the wall, authors carried out the model test and numerical analysis to confirm the behavior of the wall when the rock impacts the wall. Numerical analysis can simulate the behavior of the wall of the model test. This paper reports that it can extend the range of application of the rockfall protection soil wall for rockfall energy and field conditions.

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This paper shows examination of efficient corresponding method to large scale embankment disaster. In case of disaster, large sand bag is used points of high construction efficiency and economical at many restoration spots. Large sand bag was adopted at along river and mountainous region from past example, but there were checked about performance of safety and durability. The large sand bag is effective as emergency rehabilitation, even if it is removed at the restoration. If large sand bag is used restoration without removed, it will become effective restoration method. Therefore, we inspect durability and stability of large sand bag that will applied to restoration.

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The cases that roads were impracticable because of differential settlement occurred after massive earthquakes are often reported. Shikoku Electric Power Company has taken countermeasure works voluntarily to enhance earthquake safety of its facilities and to build further feelings of safety and security. As a part of them, we took the countermeasure to enable emergency vehicles to run on the roads in a power station even when differential settlement of road are occurred after a massive earthquake. There are various countermeasure methods considered against differential settlement of road, and among them we adopted the method by using geotextile because its reinforced part is gently deformed against differential settlement and the maintenance after construction is comparatively easy.

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In the confined-reinforced earth method, a composite layer which has a high stiffness is constructed in the subgrade to support the pavement. This layer consists of granular materials, geogrids and confining members. Compacted granular materials are reinforced between some geogrids and are further confined by some members. Construction of this layer beneath the asphalt pavement is expected to prevent unevenness even if the road embankments settle due to earthquake. In this study, a series of model tests was performed for the purpose of investigating the reinforcement effects against different designs such as a layer thickness and an introduction of pre-stress in the confining members.

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Recently, the incident that difference in level on the road occurred by seismic shaking make for emergency vehicle not to pass through have been informed. Especially in energy facility, after earthquake that kind of vehicle going through is very important to perform disaster-prevention activities. Therefore we need the effective and reasonable countermeasure not to occur its difference by huge earthquake. We think that what the road must have the limited function is available for traffic after event. And so we report for the result that we had evaluated the effects of the roadbed reinforced with geotextile by centrifuge test.

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We have developed the pile slab track soil embankment using the material which is recycling soil excavating tunnels near sites. This embankment has high performance to reduce seismic settlement of concrete slab confirmed by the shaking table test. But, it has one problem. This problem is the displacement of slab by flowing granular rocks between the slab and chemical piles. We propose a method of a large gabion to package granular rocks between the head part of improvement pile and concrete slab. And, we confirm the property of the large gabion method by actual size loading tests. This paper describes shaking table test results of the 1/10 scale model of pile slab embankment with large gabions inserted between improvement piles and the concrete slab.

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On Tokaido Shinkansen, the conutermeasures for the train safety in the case of large-scale earthquake are under execution. In order to prevent the deformation of ballasted tracks, the method to reinforce ballasted tracks with stacked geosynthetic bags that are filled with ballast(geosynthetic bags method) is adopted. In this study, we tested a various condition of the geosynthetic bags method. As a result of this test, we clarified the behavior of the geosynthetic bags method and formulated the relationship between displacement and load.

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Considering geomenbrene (GM), geosynthetic clay liner (GCL) and clayey soil layer formed composite liner system, GM/GCL and GCL/clayey soil interface shear (τf) strengths have been investigated by large scale direct shear tests. The test results indicate that the values of τf are 30-90% of the shear strength of the clayey soil, and GM/GCL interface is a weaker surface and its shear strength shall control the design in term of stability. The test results also indicate that increasing the water content of bentonite in the GCL, tends to reduce τf values possibly due to the extrusion of hydrated bentonite.

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The effect of type of leachate (liquid) on self-healing capacity of the geosynthetic clay liners (GCLs) has been investigated by laboratory leakage rate tests. Four types of liquids, namely, tap water, 10 g/l NaCl solution, 100 ml/l ethanol solution and 11.1 g/l CaCl2 solution were used. The test results indicate that the types of liquid have a significant effect on self-healing capacity of GCLs through the influence on the amount of hydration induced expansion of the bentonite inside GCLs. Free swelling index of the bentonite with the corresponding liquid can be used to evaluate the relative effect of the liquid. Also, for the conditions investigated, it seems that overburden stress (σ) on the GCL samples does not change the general tendency of the effect of the types of liquid.

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This study focused on bisphenol A and 1,4-dioxane, which are sometimes detected with high concentration in Japanese waste leachate, and clarified the barrier performance of liner sheets against these organic chemical compounds using diffusive permeation test. Benzene easily passed through the liner sheets (PVC sheet, LDPE sheet, and HDPE sheet) in a month as known in previous studies. Although bisphenol A can be adsorbed on the sheets, it cannot pass through the sheets in this testing duration. In addition, dissolved 1,4-dioxane cannot be adsorbed on any sheets and cannot pass through any sheets. The liner sheets exhibited a good barrier performance against 1,4-dioxane.

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Geosynthetic clay liners (GCLs) have been expected to be used as hydraulic barriers in the cover system, particularly for containment of hazardous wastes. A trapdoor test was performed to investigate the behavior of overlapped GCLs subjected to differential settlements, under a small overburden pressure simulating the use of GCL as a landfill cover barrier. In addition, soil tank tests were performed to measure the hydraulic barrier performance of overlapped GCLs section subjected to slippage of up to 100 mm and a decreased overburden pressure, due to the differential settlement. The testing results presented that an overlapped GCLs section subjected to differential settlements of up to 150 mm maintained its hydraulic integrity under the tested condition

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We have estimated the relationship the failure probability of which geomembrane sheets, liner of bentonite soil mixture, the travel time and the change of life cycle costs (LCC) in the waste disposal site by using the , Dynamic Programming. In the relationship the failure probability and LCC about the radioactive contaminant, the time change of radioactivity about the radioactive contaminant are considered. In the result, we have recognized that LCC is responded sensitively along the change of the failure probability, and that the travel time for liner of bentonite soil mixture is very effective in reducing LCC. In the disposal radioactive contaminant, the countermeasures decreasing the failure probability of geomembrane sheets will be required, rather than designing the excessive long travel time.

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We have developed gas-permeable/waterproof sheet (GPWS), comprising a micro-porous sheet which is waterproof but have gas permeability, coated with nonwovens to protect and reinforce it, and investigated applicability of GPWS as a landfill cap cover. In this study, gas permeability of GPWS under wet condition was evaluated. Results showed that GPWS exhibits sufficient gas permeability under wet condition that upper nonwoven layer of GPWS is saturated, when slight differential pressure (at least 0.1 kPa) is applied.

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Pond is less than 15m in height and fill dam is more than 15m in height. There are two hundred ten thousand of ponds in Japan. When we repair the pond's dike, we can’t get soil materials from nearby mountains. Nobody is permitted to get from mountain's soil with license, because of environmental problems. We introduce surface watertight sheet method covered with random soil. We cover the random soil on the sheet to prevent deterioration by ultraviolet rays, also keep 80 years in durability to be equalized with previous front core type method of irrigation pond. We clarified that pond's dike should be designed by both the safety factor in the covered soil as a slope sliding stability and a safety factor as a rotational slip of the whole embankment. The former is for empty conditions of construction. The latter is for saturated conditions. We clarified that the seepage line is described a parabola in the covered soil and safety factor in the covered soil is mainly controlled by PSR. We introduce a pond which was adopted by this method.

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This paper attempted to develop a thermo-graph inspection method for the evaluation of heat-welded seam of geomembrane. Then the proving tests using this inspection method were conducted at heat-welding construction works in Nobeoka new landfill. On the proving tests, heat-welding works and the thermo-graph inspection could be carried out in parallel, the results of inspection were displayed on the computer correctly. Those results indicated that this method can be applied practically at construction site of the geomembrane on landfills.

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In this study, for more effective utilization for coating materials for slope surface of banks and roads, foundation building of eco-friendly type slope surface and reinforcement of earth structure, erosion resistance ability and strength and deformation characteristics of mixed reinforced soil with low additive rate of short-fiber and solidification materials are discussed. As a result, the erosion resistance ability based on a long-term field test construction was verified, and addition of strengthening effect and confined effect of toughness were also verified by static and dynamic compression tests.

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The strength and deformation characteristics of the granular sand are improved by mixing the flexible short fibers. Many factors such as the mixture ratio, fiber materials, fiber length and orientation affect the improvement effect of the short fiber reinforcement sands. Especially, the mixture ratio of short fiber is very important for the improvement and the design. In this study, we carried out a series of tri-axial compression tests of four kind of silica sands in order to investigate the relationship between the optimum mixture ratio and the average grain size. From the results, we can understand that the optimum mixture ratio of sand, whose grain size is larger, becomes smaller.

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Mud-plastered wall has been used since the old days in Japan. The physical properties of wall clay used for the wall differ by regions because the wall clays are collected in the vicinity of each construction site. Straws are mixed in the clay as reinforcing materials for preventing the shrinkage crack. However, the mixing amount is determined by the experience and intuition of craftsmen. In addition, it is hard to obtain straw recently. In this study, we measured the crack area and the strength of the wall clay from various regions, and the tests were carried out on the clay mixed with bamboo fibers as alternative reinforcing materials. As a result, the unconfined compression strength increased and the crack area decreased by mixing bamboo fiver compared to the wall clay with straw. From the above, it was clear that the wall clay strength and crack properties were improved by mixing bamboo fiber.

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The Pacific coast of Tohoku Earthquake was occurred on March 11, 2011. As a result, largest-ever liquefaction damage has occured with a focus on Urayasu city, Chiba Prefecture. Especially, in the Tokyo bay coast landfilled area and inland areas led to significant damage. The main factor of this liquefaction damage is considered to be the duration of this earthquake. Existing method of suppressing liquefaction have been used cement solidification technique. This technique increases cohesion of soil material and inhibits the liquefaction. This paper reports on the results of basic research conducted and whether these techniques lead to suppression of liquefaction related to the duration of earthquakes.

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The objective of the present study is to improve durability of the cement-treated soil against wetting and drying repeated actions by applying fiber reinforcement technique. The wetting and drying cycle tests were conducted on the specimens of the cement-treated soils and the fiber-reinforced cement-treated soils, respectively. The degradation ranks were evaluated based on the observation of the external state changes, and the changes in deformation and strength characteristics were evaluated by unconfined compression tests on the specimens after each cycle of repetitive actions. From the laboratory test results of 1 to 15 cycles, it was clearly shown that the durability of the cement-treated soil against wetting and drying repeated actions was greatly improved by fiber reinforcement.

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A zeolite functional paper and a calcium silicate functional paper were developed to adsorb and remove cations and anions in water respectively. The effectiveness of these functional papers to nitrogen and phosphorus which are factors of eutrophication of a lake, a river, etc. is verified. A series of adsorption tests to the water solution containing NH4-N and PO4-P was carried out, and the adsorption properties of these functional papers were examined. Main conclusions are as follows. Adsorption of NH4-N to the zeolite functional paper and PO4-P to the calcium silicate functional paper is caused in a short time. Mutual adsorption is not prevented if both NH4-N and PO4-P are mixed in a water solution. Once they adsorbed, it will not separate easily.

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The flexible container bag using the zeolite functional paper, which supports natural zeolite powder, as an inner package was newly developed for the countermeasure against decontamination of the radioactive cesium from the accident at the Fukushima No. 1 nuclear power plant. First, the feature, the specification, and the example of application were shown. A series of filtration tests was conducted for a suspension of soil contaminated by radioactive cesium, and suspended solid and the cesium concentration of filtrate water were measured. Based on the test results, the effectiveness of the simple filtering method using the new flexible container bag with zeolite functional paper was confirmed.

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Under the influence of radioactive cesium that has diffused from the Fukushima Daiichi nuclear power plant, it is concede that the health is damaged by radiation. Therefore, decontamination work has been performed the vicinity of the residential area to reduce the health hazards. However, even after decontamination, there is a possibility that the material containing radioactive cesium by wind and rain, etc., so that radiation dose will be increased again. By doing so, the geosynthetics which can adsorb radioactive cesium is placed at the site which decontaminated. Some experiment works have done for the purpose of controlling the inflow of the material containing radioactive cesium to the decontamination area.

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An collapsing accident involving continuous-fiber reinforced soil on steep slope occurred. The accident cause may be drainage capacity degradation by clogging by ferric hydroxide gel. Ferric hydroxide gel is formed by chemical processes depending on groundwater environment and exposure time. So, we investigated the chemical background condition of the accident and measured water permeability variations of clogging geosynthetics with time. Then we found that ferrous ion rich groundwater which produces ferric hydroxide gel by oxidation abundantly flowed out at the accident site. And the drainage capacities of geosynthetics are rapidly degraded by clogging of ferric hydroxide gel.

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We continue a study of the three-axial net reinforcement from last year. This study investigated the pull-out strength by using the steel reinforcement which modeled three-axial net reinforcement.Modeled steel reinforcements were5 types. Pull-out strength increased by installing the protrusion in the reinforcement.And, the pull-out strength of the projecting reinforcement increased in proportion to loading stress. As a next step,we examined the predictionmethod of pull-out strengthwhich introduced the projection coefficient. When the number of projections became five, the projection coefficient became the approximately constant value. These results can be utilized for design of three-axial net reinforcement in which the projections.

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In order to improve the pullout resistance of geocell, a square-shaped geocell having straight longitudinal members with transversal walls at separated locations was developed. A series of pullout tests was performed on two types of small scaled geocell models which have conventional diamond-shaped cells and square-shaped cells embedded in compacted backfill consisting of either of two gravels having different particle sizes. The pullout tests on a geogrid, Tensar SS-35, was also performed for comparison. The results indicated that the newly developed square-shaped geocell reinforcement has higher initial stiffness and peak pullout resistance compared with the diamond-shaped geocell reinforcement, exhibiting comparable performance to the geogrid. With the square-shaped geocell, effects of the spacing between adjacent transversal walls and height of the transversal walls on the pullout resistance were found. In addition, the maximum pullout resistance obtained in a series of the tests using the square-shaped geocell were summarized to show the influencing factors, as well as the particle size of gravel backfills.

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As a basic study for the constructing a model of soils mixed with elastic particles such as rubber tips, it was intended to estimate the compressive property caused by the deformation of the elastic particles. A series of onedimensional compression tests was executed using aluminum and rubber rods, considering the effects of initial arrangement of rod-stacking. In the experiment, pictures of the states of compression were taken with digital camera. The images were analyzed by computer to calculate the volumetric change of rubber particles themselves and pore spaces, and tried to construct a quantitative model for calculating these volumetric change from properties of rubber and geometrical relation of rod-stack model's deformation. As a result, it was revealed that two compressive components concerning to the compression of rubber mixed soil could be predicted by considering the Poisson's ratio of rubber with skill.

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In this study, pullout tests of geogrid embedded in banking material were performed, in order to establish the design procedure of GRS integral bridge. The effect of cyclic loading as well as the confining pressure was mainly focused on in these tests. The experiments revealed that although the pullout stiffness of geogrid at the initial state was much larger than the tensile stiffness obtained by in-isolation tests, it was reduced largely by the large number of cyclic loadings and finally it became at the same level as that obtained by in-isolation tests. This is due to the reduction of interlocking effect mobilized between the geogrid and surrounding soil, and the increase of the stretching region of the geogrid. Based on these test results, new method to predict the pullout stiffness of the geogrid under different confining pressure was suggested.

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Since the surface of the geotextile is unevenness by knit into a fiber, it is difficult to stick the strain gauges on the geotextile directly. So, a method to stick the strain gauges on the geotextile which stuck the vinyl chloride film is popular. This paper is verifying the accuracy of the strain measured by this method. The results of this strain measurement method under the laboratory tensile test and the field tensile test differs by environmental conditions, and the strain measured by this method was smaller than the strain measured by the image analysis under the laboratory tensile test. However, load and strain which were measured by these methods showed linear relation. This paper checked that the strain measured by this method under the same environmental condition could be used for qualitative comparison.

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There are many improper disposal sites and illegal dumping sites. Some of them are made in a steep slope and endangered condition in collapse that become very serious environmental problem. It is strongly required to enhance study for clarification of mechanical property and establishment of stability method of solid waste materials. In this study, evaluation of strength property of solid waste materials with plastic materials is mainly purpose. Especially, tensile property of solid waste materials was investigated by developed tension test apparatus. Therefore, stability method of solid waste ground was considered by using reinforced earth theory.

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In tsunami disaster prevention, the most important structure is a seawall embankment constructed near the shoreline. Many seawall embankments, which were constructed by old technique, collapsed by a tsunami in The 2011 off the Pacific coast of Tohoku Earthquake. In this study, we carried out the fundamental hydraulic model tests to develop the new seawall embankment technique by using the geotextiles. At first, we modeled the embankments and the foundation ground as the rigid body in order to examine the influence that the incline of the embankment gave for the tsunami energy reduction. From the experimental results, we can understand that the embankment can reduce the energy of Tsunami as the incline of the embankment approaches the vertical. Moreover, we carried out the tsunami hydraulic tests for the old seawall model and the geotextile seawall model. We showed that the geotextile seawall model is the most effective to reduce the tsunami energy in the case of the overflow.

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It is not feasible to construct coastal dykes that are high enough to prevent over-topping flow of such giant tsunami as experienced during the 2011 Great East Japan Earthquake. For such coastal dykes as above to survive deep over-topping tsunami current, it is essential to prevent the erosion of backfill. The results of small-scale model tests showed that even facing of a thin flexible planar material, such as nonwoven geotextile sheets, can prevent the erosion of the backfill very effectively if the facing is arranged in such that its stability against over-topping tsunami current is maintained.

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Most of the extensive damage caused by the 2011 off the Pacific coast of Tohoku Earthquake was due to the huge tsunami. With more than 340 bridges, either the girder was lost or the approach fill was washed away or both. A series of small model tests were performed to evaluate the stability against tsunami of the conventional type bridge, for which the girder is placed on the top of the abutments via bearings with unreinforced backfill, and Geosynthetic- Reinforced Soil (GRS) Integral Bridge, for which the girder is integrated to the facings and the backfill is reinforced with geogrid layers. It is shown that GRS IBs are much more stable against over-topping tsunami current.

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Because many sea walls were damaged severely by the tsunami flood in the 2011 Off the Pacific Coast of Tohoku Earthquake, the reconstruction strategy requires making the sea walls tough against the level 2 tsunami flood. Based on the field survey on the tsunami damage by the authors, several lessons on the toughness of the earth banks and the possibility to apply them as the hardware measures can be obtained. Then, in order to clarify the above effective lessons, the over-flow model tests on the retrofitting methods to advance the toughness of the earth banks with the geosyntetics and so on are conducted and discussed. As the results, the possibility to apply the earth bank similar to the sea walls and to improve the toughness of the earth bank easily with the geosynthetics and so on.

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Overflows of huge floods caused levee breaches at a great number of places. As a reinforcing technology to increase the resistance against overflow erosion, we performed a series of model tests on a new type of levee in which concrete panels connected to geo-grid layers reinforcing the backfill cover the slopes and crest of the levee, as well as conventional types. The model test revealed that 1) with a score protection in front of the toe of downstream slope, the new type levee exhibits much higher resistance against overflow erosion than the conventional type levee; 2) the new type levee even with a steep backslope of 1:0.5 can maintain the high resistance of overflow erosion. It is shown that the new type levee can function effectively as a flood barrier at low cost and small cross section.

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Based on lessons learned from tsunami damage and generation of enormous quantity of post-quake waste in the Great East Japan Earthquake, two types of tsunami refuge places which can be diverted to landfill for future massive earthquake with utilizing Geosynthetics were examined. As tsunami refuge site (1), circular tsunami refuge place with soccer coat surrounded by 20m high dam body at perimeter was designed. 5m high linear refuge place with bicycle and pedestrian roads was also designed as tsunami refuge site (2) to use green belt buffer between land use zone of residential site and agricultural field.

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Geotextile-reinforced soil wall makes a unified and stabilized soil structure by pull-out and friction resistances of geotextile from soil. Since an embedment length of geotextile depends on soil properties, it is often difficult to apply the reinforced soil wall to steep site, which is close to hard bedrock, because the required length of geotextile is not secured. When the soil is confined to geotextile, it is confirmed that the dilatancy of soil is restrained. Authors focus on a confining effect of soil using geotextile and proposes a confined soil wall, which is layered the confined soil layers by using geotextile, like a retaining structure. This papere presents design and constuction procedures of the geotextile-confined soil wall.

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A number of Geosynthetic-Reinforced Soil Retaining Walls (GRS RWs) collapsed during heavy rainfalls and earthquakes in Japan. In the US, most collapse cases are in the private sector. The collapse is due to insufficient redundancy resulting from excessively economical, therefore inadequate, structure type, design and construction. As the actual soil density is higher than the design value while the apparent cohesion due to suction and the passive earth pressure on the front face of the facing base are ignored in design, GRS RWs have redundancy that is not covered by the safety factor. They have rather large redundancy under normal ordinary conditions and it increases by seismic design. The redundancy increases by good structure, good design and good construction, reducing the long-term maintenance cost and the cost by failure/collapse. The method to have relevant redundancy is discussed.

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Analysis method of the CO2 emissions is proposed for geogrid reinforced soil wall. The methods for L-shaped RC wall and no-reinforced embankment are also shown for comparison. Using the CO2 emissions intensities which are summarized from previous documents and the spread sheets which are shown in this paper, the CO2 emissions for three kinds of geo-structures can be estimated by considering each construction condition. Based on example analysis, it is shown that geogrid reinforced soil wall has a strong advantage in environmental impact comparing with Lshaped RC wall or no-reinforced embankment. Contents of this paper are from achievement produced by Technical Committee: Stage 5 established in IGS Japan chapter (2010-2012).

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12 case histories on failure and deformation of geogrid reinforced soil walls were collected. The probable failure and deformation mechanism was identified and the counter measures were studied. More than half of the cases were reinforced soil wall which had been constructed on valley or sloped foundation in mountain area. Main mechanism was seepage of rainfall over the drainage capacity. In much of the case, reinforcing system, height and slope of reconstructed wall was almost same as those of initial state. This achievement may contribute for not only developing of design method to decrease the failure and the deformation but also lifecycle management of reinforced soil wall. Content of this paper is from achievement produced by Technical Committee: Stage 5 established in IGS Japan chapter (2010-2012).

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The life cycle analysis method is proposed for geogrid reinforced soil wall. The proposed method evaluates life cycle cost as total cost of initial cost, maintenance cost and seismic risk. This paper shows the standard evaluation method of the seismic risk which is a product of failure probability and seismic disaster costs. Based on the proposed method, LCC of geogrid reinforced soil wall, L-shaped RC wall and no-reinforced embankment were compared. It is cleared that LCC of the geogrid wall is the lowest in spite of traffic volume and structure length. Content of this paper is from achievement produced by Technical Committee: Stage 5 established in IGS Japan chapter (2010-2012).

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This study focuses residual settlement of asphalt pavement system subjected to traffic loads in the view of geotechnical engineering. Firstly, the effects of residual deformation properties of the base aggregates during wheel loading that is concerned with stress conditions in the subbase layer was investigate by performing of laboratory wheel loading test of asphalt pavement. At the results of model loading test, it was confirmed that large residual deformation of the base aggregates due to traffic loads lead degradation of asphalt mixture material. The effects of geogrid-reinforcing technologies on the residual deformation characteristics of the asphalt pavement structure were also examined in the present study. This study investigates the performance of the followings three geosyntheticreinforcing technologies applied to the subbase layer on the stability of pavement system; a) short-fiber mixing, b) geogrid-reinforcing, and c) combined of short-fiber mixing and geogrid-reinforcing. The residual settlement of the subbase layer caused by traffic loading can be reduced by applied the above reinforcing technologies.

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The lightweight geomaterial mixed with EPS beads (LWGME), a mixture of superlight EPS beads and normal geomaterial, is one of the geoform. As for LWGME, the applicability as subgrade soil is checked. However, the design parameter as the subgrade soil of LWGME is not clear. This study, as a part of our studies to make clear the design parameter of LWGME used for subgrade, conducted the resilient modulus test. Moreover, resilient modulus from resilient modulus test is a non-linear elastic modulus depending on a stress state. Therefore, subgrade resilient modulus was computed by structural analysis of the pavement using GAMES, and the estimate equation in consideration of combination conditions is proposed so that subgrade resilient modulus could be computed easily.

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Dredged soft clay from the sea-bed of the port of Kobe was employed in on-going project of land reclamation work in North-West part of Kobe airport island. Since the clay was characterized with its super-high water content, a series of geo-grid sheet was displayed on the soft clay ground in order to achieve the prescribed trafficability for vehicles in use for spreading surface soil. Prior to the reclamation work, a trial test was carried out in order to observe the behavior of fully-instrumented geogrid sheet . In addition, the in-soil pull-out test of geogrid was performed for a better understanding into the sheet behavior when subjected to tension force. In this paper, the results of the trial test are discussed based on these in-situ laboratory tests.

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Extremely soft clay ground formed by dredging is located in North-West part of Kobe Airport Island. In an attempt to make the ground for land use in near future, soil spreading work using geogrid sheet was employed in order to acieve the prescribed trafficability of the spreading machine. Prior to the work, a trial work using fully instrumented geogrid sheet was carried out in order to examine the details of the construction scheme work. In this paper, the results of two-dimentional FE simulation considering soil-geogrid interaction are presented. In this analysis, an interface element reflecting properly the result of in-soil pull-out test of the geogrid was employed. Ground behavior of extremely soft clay ground in the event of soil spreading with geogrid sheet was successfully evaluated by 2D FE analysis.

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