The gyosyntethics liners of landfills are important not to contaminate groundwater and soil. This paper introduces the several cases for reduction of the influence to environment in design, construction and maintenance of landfills. And the theme is proposed on the process of the landfills; location, design, construction and maintenance.

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A new type geogrid-reinforced soil wall combined with soil cement was developed recently. Centrifuge shaking table tests were carried out to verify the seismic stability of this wall. Deformation was much smaller than those of the conventional geogrid-reinforced soil walls or the soil cement walls. Tension crack was induced at the top of the soil cement wall by the effect of inertia force induced in the soil cement wall. But the generation of tension crack was protected by mixing the short fibers in the soil cement and the reinforced soil wall showed very high seismic stability.

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In this study, an attempt was made to discuss effects of geogrid properties on seismic stability of the reinforced soil wall. Centrifuge shaking table tests were conducted to study the behavior of geogrid-reinforced soil wall. Properties of model geogrids, which were used in this study, were investigated by tensile tests and pullout tests. It was found that stability of reinforced soil wall was strongly influenced by shape and stiffness of geogrid. Deformation of the reinforced area is especially limited by confirming the area with the geogrid of high stiffness. Therefore, the soil wall can be stable. The horizontal seismic coefficients at failure obtained from the centrifuge shaking table tests were different from those of centrifuge tilting table tests, which were made in the past few years. But their failure modes were similar each other.

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The EPS construction method used on steep slopes, where space is limited, and in other similar locations is often executed using vertical concrete panels as the wall surface. It is therefore difficult to restore vegetation on the wall. The EPS lightweight embankment method, which uses expandable metal, welded metal screens, or Geogrid as the wall surface in order to build a steep reinforced embankment where vegetation can be restored, has recently been applied at a number of work sites in Japan. However, certain aspects of this method are still not understood, such as how work executed by this method is affected by the traffic load. A full-size embankment 3m in height was constructed and used for vibration testing as part of research to clarify these types of behaviors.
This paper reports on the results of the vibration testing.

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After the recent large earthquakes like the 1995 Hyougoken-Nanbu earthquake in Japan or the 1999 Chi-Chi earthquake in Taiwan, several series of model tests have been conducted to investigate the seismic behavior of reinforced soil retaining walls (RWs), while they did not focus on the effect of subsoil conditions under RWs. In this study, therefore, two types model reinforced soil RWs were constructed with and without inserting a steel plate wrapped with teflon sheet at the interface between the reinforced backfill and the subsoil, and model shaking table tests using a sinusoidal wave were performed to investigate the effect of the teflon sheet on the behavior of RWs. As a result, the RW without the teflon sheet tilted predominantly, those with the teflon sheet slid predominantly. Tensile forces mobilized in the reinforcements were also affected by such a different displacement mode.

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A series of shaking table tests were performed to validate a high dynamic stability of preloaded and prestressed geosynthetic-reinforced soil (PLPS GRS) abutment. Three-dimensional models, which were free from the friction between the backfill and the sidewalls of the sand box, were used. The test results revealed that the dynamic stability increases significantly by increasing the dry density of backfill and by fixing the tie rod to the top reaction block by using a ratchet system. It was shown that the ratchet system not only prevents a large reduction in the vertical prestress applied to a PLPS GRS structure when the backfill exhibits compression, but also contributes significantly to the dynamic stability of the structure by preventing the increase in the height of backfill. It was shown that by the latter function, the dynamic stability of PLPS GRS abutment could be very high even when the initial prestress is very low.

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The preloaded and prestressed (PLPS) geotextile-reinforced soil structure can have substantially high stiffness and stability in the vertical direction when subjected to cyclic vertical load. The struture has a high damping ratio, flexibility and ductility when subjected to cyclic horizontal load during earthquakes. The structure can also exhibit a high resistance against large lateral deformation. By taking advantages of these features, the structure could function as a base isolation system supporting a massive superstructure. To examine this feasibility, a series of shaking table tests on models supposing a model massive super-structure. It was found that by adjusting the natural frequency of the system, the structure could function as a base isolation system.

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Free swell and hydraulic conductivity tests were conducted on geotextile-sandwiched geosynthetic clay liners (GCLs) with NaCl-CaCl₂ and LiCl-CaCl₂ solutions to evaluate their chemical compatibility and applicability to landfill liners. Flexible wall permeameters were used for the hydraulic conductivity tests. Main conclusions derived from the experimental results are: (1) the hydraulic conductivity of GCLs were correlated to the free swell power of ground bentonites, (2) powdered bentonites in GCL are more compatible than granular bentonites against chemicals, in particular aggressive (poly-valent and high concentration) solutions, and (3) divalent cations have more effects on the performance of GCLs than monovalent cations.

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Although the waste refuse reclamation periods in an inland final controlled disposal site may last over 15 years in general, it is a present condition that geomembrane used as impervious layer is protected only with the geotextile. This condition always contains the possibility of risk, such as geomembrane damaged and so on, caused by the heavy industrial machine while landfill of refuse. Hence, the research of filling soil in the honey cam frame and tree planting was conducted to aim at harmonizing a long-term protection of the geomembrane and surrounding natural environment. This paper reports the results based on the actual proof experiment and the construction example.

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The liner sheet installed in a waste landfill is made of a synthetic resin and a synthetic rubber as the main ingredients, and behaves as a typical visco-elasticity. If it is left after a constant strain has given, stress relaxation will occur with time. The liner sheets used in this research are HDPE, FPA and TPO, and each thickness is 1.5mm. Experimental equipment consists of load transducer which measure the tension force, a specimen attachment clamp, a screw moving the clamp and an iron frame. In this research, stress relaxation experiments were conducted in many stages and a constant distortion. Furthermore, comparison between the experiment result and calculation values which was estimated by three-element visco-elastic model was performed.

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Interface shear strength between geosynthetics and geomaterials is an important factor for stability of slope that is made on a geosynthetics multi-liner system by overburden geomaterials behind the seawall of a controlled sea-based disposal site. A series of direct shear tests were conducted to obtain interface shear strength between the adjacent components that are used in the liner system. Shear strength and stress-displacement relations are well characterized by the test conditions either in the air or in the water, and by the types of geomaterials and geosynthetics.

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When a geosynthetics liner system is installed in a slope that is made by overburden geomaterials behind the seawall of a controlled sea-based disposal site, the liner is suffered from shear force caused by the self-weight of the mass of geomaterials. A series of direct shear tests on two to five layered models were conducted by using a newly developed apparatus that can measure each component of the liner system. The resisting mechanism of the multi-liner system was well understood by analyzing shear stress and relative displacement relations between the adjacent components.

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Nonlinear elasto-plastic FEM analyses were conducted to simulate interaction behaviors of a geosynthetics multi-linear system installed in a slope that is made by overburden geomaterials to resist uplift force behind the seawall of a controlled sea-based disposal site. The interaction model was created based on the shear resisting characteristics obtained from a series of direct shear tests between geosynthetics and geomaterials that are used in the liner system. Then, the analysis method was verified by simulating the measured behaviors in direct shear tests on five-layered linear models. For a fundamental case of the slope, having sufficient safety factor obtained from a limit equilibrium method, in which two sets of geosynthetics multi-linear system are installed, distribution of tensile forces induced in geosynthetics were obtained by incremental analysis method that can simulate actual execution procedures. In addition, parameter studies were conducted on the effects of shear resistance between geosynthetics and their tensile rigidity.

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National design standards concerning geomembrane surface linings for dam and reservoirs demand appropriate countermeasures against predicted deformation in foundation ground due to climatic and geologic conditions. However, the ratio of cost for countermeasures compared to the entire construction cost is generally large. Therefore, it is necessary to elucidate the flexibility of geomembranes to foundation ground deformations in order to make the countermeasure low-cost. In this paper, the flexibility of geomembranes to foundation ground deformations caused by frost heaving was examined in the laboratory. The results confirmed that EPDM geomembranes don't require replacement of ground soil to the depth of frost penetration with the generally adopted method of macadam.

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In general, the design methodology of reinforced retaining wall subjected high seismic load such as level 2 earthquake, which is shown in the current railroad seismic-design standard, implements Newmark method for deformation analysis. However, the details of deformation analysis for retaining walls subjected to high horizontal force at the top of the wall such as an electric pole is not fully discussed. To have a better insight into the seismic design, the effect of reinforced zone and inertia force of the electric pole was evaluated in a rational manner. The effective number of reinforcement to satisfy allowable deformation of this structure subjected to high seismic force was also discussed in this study.

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Because of the experience of 1995 Hyougoken-Nanbu earthquake, the improvement of seismic resistance of the entire abutment system, including the abutment itself and the backfill, has become an important topic recently. In this study, based on the concept of reinforced abutment with cement-treated backfill, the comparison between this kind of newly developed abutment system, applied to the current railway construction, and the reversed T-shape abutment has been conducted. According to the results, it can be found that reinforced abutment with cement-treated backfill performs superiorly to the usual abutment so far both in the capacity of seismic resistance and the economical point of view.

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One of the mechanical properties of such lightweight geo-materials in geosynthetics is that Poisson's ratio is very small, compared with natural geo-materials. In this study, the effect of the Poisson's ratio on earth pressure reduction are investigated, particularly in the case that the lightweight geo-material is applied as the back fill material of a retaining wall structure by using the elastic finite element analysis. The results from FE analysis indicate:
(1) Earth pressures against the retaining walls are reduced with decreasing the Poisson's ratio of the lightweight geo-material.
(2) The larger earth pressure is developed at the region of the higher position of the retaining wall.
(3) The earth pressure is strongly influenced by the boundary condition adjacent around the back fill. Therefore, the boundary condition needs to be taken into consideration in the design of wall structures.

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We proposed the simple equation in the past to predict a coefficient of vertical earth pressure acting on a box culvert with compressible material installed on its top. This material is aimed to install to reduce the earth pressure acting on the box culvert. Although the simple equation was derived under the simple hypothesis, it was proved to give a reasonable value. On this study, range of applicability and acceptability of this equation is targeted to investigate using data in public shown in the references and FEM analysis. Furthermore, this equation is extended out of limitation to predict earth pressure acting on pipe culvert through a flexibility factor as indicator representing deformability of pipe.

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The tensile deformation and strength characteristics of polymer geosynthetic reinforcement are more-or-less viscous. Therefore, accurate evaluation and interpretation of the time-dependent tensile stress-strain behaviour of geosynthetic reinforcement is of great significance for the prediction of the long-term residual deformation of geosynthetic-reinforced soil structure. It is discussed that the creep is not a degrading process, but it is a response of a material due to its viscous properties. Viscous properties of four different types of geogrids were experimentally evaluated by performing monotonic loading (ML) at different strain rates while changing the strain rate and performing creep and stress relaxation tests during otherwise ML. The test results were simulated very well by three-component models. The structures of the model are discussed based on the test results. Based on the test results, it is discussed that usually it is not necessary to introduce a creep reduction factor when the design strength of geosynthetic reinforcement for a given lifetime is determined, but a correction for strain rate is relevant.

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One of the main uncertainties in the design of permanent reinforced soil structures is the strength and deformation characteristics throughout the design life of polymeric reinforcement under load in the backfill. The current design practice focuses primarily on the creep deformation and the design tensile rupture strength is determined by using a relatively large creep reduction factor. To have a better insight into the time-dependent strength and deformation characteristics of polymer geogrid, in total 34 creep and stress relaxation tests were performed at various tensile load levels, each lasting for 24 hours, by using polypropylene (PP), polyester (PET) and high density polyethylene (HDPE) geogrids. A series of constant rate of strain (CRS) loading tests was performed on specimens that had been subjected to creep or relaxation loading. The tensile strength after creep and relaxation loading of each geogrid was essentially the same value as the one obtained from a monotonic CRS tensile loading test before the creep or stress relaxation test. This result shows that it is not necessary to use a creep reduction factor when determining the design tensile strength for prototype reinforced soil structures subjected to seismic force.

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Comparison of in-soil deformation behavior of geogrid observed by pull-out test results and those calculated by the authors' formerly proposed method was performed. Based on the results, it has been pointed out that it is important to construct a reinforced soil structure so that sufficient frictional resistance develops between soil and geogrid since the pull-out force vs. pull-out displacement relationships depend not only on the embedded length of geogrid but on the normal stress exerted on the geogrid.
From a series of pull-out tests and in-soil creep tests, it has been found that the pull-out force vs. pull-out displacement relationship for both tests almost coincide with each other within the range of the pull-out force smaller than sustained creep load. Based on the comparison between calculated in-soil creep deformation behaviors by using the method proposed in this paper and those observed by in-soil creep test, the importance of the establishment of design method considering not only the deformation of geogrid itself but the overall deformation of the reinforced soil structure due to the relative displacement between soil and geogrid has been pointed out.

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It is considered that pullout characteristics are influenced by properties of soil. Particularly in this study, particle size was focused and a series of pullout tests was carried out with three kinds of sand which have different particle size. It was found that the pullout resistance was larger as the particle size of soil was larger. To discuss the effects of particle size in detail, we observed the deformation of soil around geogrid while it was pulled out. The test results showed that the larger area was deformed with the pullout of geogrid in sand of larger particle size. Therefore, pullout resistance was larger for the large particle size.

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Residual deformation of two types of geogrid subjected to cyclic loading, simulating traffic loading, was evaluated by performing a series of load-controlled cyclic loading tensile tests. Cyclic tensile loads were applied at two or three different load levels, at five different loading frequencies with two different load amplitudes. Creep loading tests were performed at the same loading levels as the cyclic loading tests. The two potential influencing factors for the development of residual deformation of geogrid during cyclic loading are; 1) loading rate effects due to material viscous properties; and 2) time-independent cyclic loading effects. Among the two, the loading rate effects are much more dominant on the residual deformation during cyclic loading within the limit of the test conditions in the present study, showing that it is necessary to introduce the loading rate effects in a constitutive model to predict the residual deformation of geogrid subjected to cyclic loading.

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Some of principal problems related to the required discharge capacity of the prefabricated vertical drain remain ambiguous in practice on the product quality check. Of these hydraulic gradient required when testing, and reducing pro perties of discharge capacity due to confining pressure are especially important. They were proved in the conference held in Kochi in 2000 that the required discharge capacities presented by some concerning countries were different from each other on the similar condition and the hydraulic gradients required in the quality test wasn't associated with by some countries. Therefore, actually demanding concept is to indicate how to predict the required discharge capacity regards with appropriate improvement of soft ground, not showing unified controlling value itself. In this paper, two items, the discharge capacity defined by the hydraulic gradient of one and reducing tendency of discharge capacity due to confining pressure, are made the targets as primary problems and the group of equations is presented to evaluate the discharge capacity characteristics. And comparing with the results of FDM calculation and laboratory test results, the signification of hydraulic gradient of one is described to become the useful criteria and the result of analyzing shrinkage of passage area for water can derive the role of membrane enveloping test specimen affecting amount of discharge capacity.

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Geotextile or goecomposite drain sheets are used commonly for collecting and draining the seepage water in an embankment or the pore water in a cohesive soil with high moisture content. In these cases the combined hydraulic characteristics of the multi-layered structure depend on both the permeability of soil and the transmissivity in plane direction and the permittivity in cross-plane direction of a geodrain sheet.
In this study a laboratory two dimensional model test is conducted for a cohesive soil embankment in which a geotextile is placed. The effects of thickness of geotextile, overburden pressure and degree of compaction (i. e. soil density and permeability) on the hydraulic properties of the models are investigated and the results of tests and the interaction between the geotextile and the soil conditions are discussed.

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This study evaluates the residual strength of polyester based web-shaped geosynthetic. The material studied was recovered from under an embankment where it had endured a period of several months and 1.5 years' respectively. Tests on polyester based web-shaped geosynthetic show that they retain more than 90% of their initial strength after a period of sustained load. The study also presents the results of the monitoring of the embankment.
It is suggested that the design strength of polyester based web-shaped geosynthetic in seismic application, is greater than the limiting design strength used to preventing creep rupture.

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High strength geosynthetics is a new reinforcement material, which is used as reinforcing a embankment, by laying the material to the lower part of the embankment. It is used in the case that the stability of embankment cannot be secured when the embankment is built on soft ground, in the same way with wire net laying method. In recent years, the embankment reinforcement using this new material has been increasing at expressway construction sites of the Japan Highway Public Corporation. From the construction results, it becomes clear that an actual measurement value of the tension occurred in the material shows rather small value compared with the design value. In this paper, in order to verify the effectiveness of the embankment reinforcement, a fundamental study was conducted on strength occurrence mechanism of a composite body of soil and high strength geosynthetics by using large-size box shear testing equipment.

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Goesynthetic short fiber-mixed reinforced soil construction method is capable of improving and controlling the mechanical characteristics, e. g. apparent cohesion, toughness, and ultimate and residual shear strength, resistance of erosion caused by rainfall and weathering, and such other properties as green vegetation concerning environmental conservation. Moreover the method is applicable to weak strength soil as an effective reuse of surplus material in a construction site, and consequently the technique may fulfill multi-functional performance. However comprehensive understanding and sufficient data are not available yet regarding the internal reinforcing phenomena and mechanism of the fiber-soil particles mixture in which short-length fibers are distributed homogeneously.
In this study a new type of reinforced soil blended with a short-length geofiber with limbs in its normal direction is developed with the intention of increasing its reinforcing effect furthermore and being possible for the natural soil or the fibers to be reused in case of any modification of the geostructure some day. This paper describes the results of effects of limb length of fiber using both a large-scale box shear test and an unconfined compression test.

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In this paper, a new method called reinforced river dike is proposed as a new application of soil reinforcement technique. In order to establish design and construction methods for the proposed reinforced river dike, a real-scale field construction and field monitoring were conducted at Shin-Sakai River in Gifu Prefecture, Japan. Then, full-scale destruction experiments were conducted at Awara town in Fukui Prefecture, to investigate failure mechanism of the reinforced river dike. Based on the results from the field monitoring and real-scale destructive experiments, a new reinforced river dike was constructed, and the real-time monitoring of the experiment is on going.

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The use of geosynthetic-reinforced soil walls as revetments has been expected to be used for protecting coastal area in the developing countries, particularly from the view points of economical saving and environmental preservation. It has been proved from the results from model tests that reinforcement with wrap-around non-woven geosynthetics for soil walls as revetments is successful by means of sewing together and injecting mortar in the frontal part of embankment. A design concept has been proposed for determining the spacing distance and length of geosynthetics which are used for reinforcement of revetment of coastal area under assailing ocean waves

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Reinforced dike section using geogrid at its bottom met a damaging earthquake named the Tottoriken-Seibu Earthquake on October 6 2000. As there laid a loose sand layer beneath the 3m high dike, the section was constructed using geogrid sheets at its bottom to prevent an anticipated soil liquefaction in 1996. 4 years later, this section was hit by the earthquake, however, 80% of the treated length of the section survived without damage, 120m long section within the treated section subsided by about 1m. Settlement and groundwater table together with strong ground motion were kept to measure since the completion of the dike construction. Effectiveness of the geogrid reinforcement for small scale dike against soil liquefaction was examined using observed data and numerical analysis.

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Influence of traffic load on the performance of geosynthetics in reinforced expressway embankment was investigated at the embankment used as a detour of the main line construction section. Strains of geosynthetics were measured throughout the construction of the embankment and the effects of traffic load were monitored for three months. At the end of project, the geosynthetics were recovered from the detour embankment and their strengths were checked.

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Deformation characteristics under constant load by the overburden weights and the self weight, and large number of cycles of cyclic load in service, such as traffic loads, are important as a long-term performance of reinforced soil structure. It is important to know the deformation characteristics of the backfill materials and such structures under constant loads and cyclic loads. Cyclic loading tests on models of a reinforced soil pier, and triaxial specimen of a backfill materials were performed. A long-term measurement results of a prototype reinforced soil bridge abutment were also introduced and its deformation characteristics are discussed.

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For the appropriate design of large foundation deformation patterns of the reinforcement layers may to some extent permit the use of the results of small scale loading tests. This paper reports some of the small-scale model tests on reinforced sandy ground, which basically enunciates the various deformation pattern of the planar geocomposite reinforcement layer, subjected to static vertical loading. Initially load tests were carried out at three different relative densities (Dr=32%, 70%, 89%) from which optimum length (L) and placement depth of single geocomposite layer was found as 2.5B (B=footing width) and 0.4B respectively. After careful observation of the shape and deformation patterns of the reinforced zone, the same geocomposite layer was made into two possible shapes (V and channel shape). Load test results indicate that V-shape caused enormous increase in bearing capacity compared to plane layer.

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The use of Geogrid steep-slope reinforcement earth walls using steel wall-surface material is spreading rapidly as a road-embankment construction method. This method has been executed with the reinforcing material (Geogrid) arranged in a zigzag pattern at more than 1, 000 locations in Japan, but the present design method does not clarify the installation pattern of the Geogrid in the direction parallel to the embankment. This report describes a model pullout experiment and a model loading experiment employing the full pattern and the zigzag pattern. These experiments were performed as part of research intended to establish a method of designing the execution pattern in the direction parallel to an embankment. The results confirmed the stability of the zigzag pattern.

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Recently the method at face of slope for geogria reinforced soil wall has been changing from using vegetation sandbag to using steel facing unit. It is proved effects of confining that steel facing unit is equal to using vegetation sandbag by a lot of execution. And, many different stiffness of steel facing unit is used in geogrid reinforced soil wall. But such the steel facing unit is not proved definitely degree of confining. In this research, the test embankment was constructed by different stiffness of steel facing unit and, the deformation of the steel facing unit and degree of compaction around the steel facing unit was measured.

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The retaining wall for falling stone using geosynthetics is, capable of countering steep topographic conditions and the large energy of falling stones. In the past, we conducted an experiment with vertically dropping a weight of 50kN from the height of 20 meters, as well as basic research on the evaluation of impact absorbing performance of this method and the mechanism. From this research, the retaining wall for falling stone is confirmed to show protective work and to be safe structure. However, the route and impact of the actual rock fall are complicated. Therefore, it is considered that the influence by falling stones is different from the case with vertically dropping a weight. In this study, a retaining wall for falling stone is built along the National Highway route 305. The route and impact of a falling stone and behavior of a retaining wall for falling stones was confirmed, by dropping actual stones on the slope face (the height 30 meters). A performance test on impact buffering materials was also conducted as a preliminary test. This paper presents the results of this falling stone experiment.

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