Geosynthetic Horizontal Drains (GHDs) are possible to be used in the case of steep soft clay embankments. To obtain the behavior of GHD-reinforced embankments, the numerical analysis of GHD-reinforced embankments which are referred to the full scale test embankment in site was conducted. As the result, the FEM used in this study can simulate the deformation and stress with the comparison between calculated value and measured data. Further evaluation about material properties of GHD, effects of facing, and arrangement of GHD in the embankment were carried out.

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We, TOBU RAIL WAY CO. LTD, have been working on the construction to lay double tracks in place of a present single line between IWATUKI and KASUKABE. (it's distance is around 7.4 kilometers) There are purpose for this construction; first, to increase the capacity of transportation, second, to relieve congestion and third, to cope with the demand of transportation whose scale may be bigger in the future in TOBU NODA LINE. There is high embankment between the section we are working on. Geological feature of there is poor subsoil which is made from organic silts, humus soil and tuffic clay. Moreover, along the side of a railroad, houses stand together. After our much consideration about aspects of difficulties of the construction, an environmental and economical matter, and periods we would need to spend, we concluded that widening embankment by an usual method which retains a wall might cause some problems.
Then, this time, we have decided to adopt the different way which reinforces banks. Recently, this kind of method has been making actual results and is recognised to be an excellent way for aseismicity.
In this paper, we are going to state about circumstances explaining about how and why we made a decision to try this way-by reinforcing banks-to widen embankment, and also about results from our examinations, plans, methods of construction on the place where there is high embankment placed on the poor subsoil.

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In the reconstruction of a railway embankment with a total length of 600m, a geosynthetic-reinforced soil retaining wall was adopted because of limited space and cost reduction. This structure has a continuous rigid facing in order to reduce the deformation of wall, thereby increasing the overall stability.
The maximum height of this embankment is as high as 8m. In view of few well-documented case history of this kind, this paper describes the actual construction process as well as the countermeasures against troubles encountered in this process.

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In the current design code, the geosynthetic-reinforcement is considered by assuming the gain of tensile strength. This interpretation for geosynthetic-reinforcement is easy to handle in the engineering practice of design work but it might be far from the real mechanism of geosynthetic-reinforcement. Then, the authors organized a research project to ensure and examine the real geosynthetic-reinforcement mechanism and constructed four full-scale geosynthetic-reinforced soil structures in Kanazawa. These soil structures were loaded and were led to various kinds of failure patterns at each final stage where deformation of structures and tensile strain of geosynthetic-reinforcement materials were monitored during the tests. This paper introduces these four full-scale model tests and reports the monitored results. Some comments on the geosynthetic-reinforcement mechanism obtained through constructing these full-scale model tests are also presented.

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This paper describes a test embankment where the geosynthetic-reinforcementis employed to stabilize the slope of embankment. In this site, pre-stressed steel bars were installed in the perpendicular direction to the geosynthetics stratiformly placed, expecting the gain of confining effect for soils which resulted in increasing the toughness of the soil structure. Several different reinforcement patterns with the pre-stressed steel bars were constructed. The gain of confining effect was examined and the stability of the slope was discussed. This paper presents a new method to stabilize the slope using the geosynthetic-reinforcement.

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Steep and high embankment filled by clay and reinforced with the geosynthetic horizontal drains has been completed. Its height is 10m and its slant is 1:0.6, although it is impossible to be filled without the reinforcement by the GHDs. Materials of GHD are compound of plastic core surrounded by the nonwoven filter and the reinforced nonwoven fabric. In this paper, the fundamental properties relating to the friction characteristies between GHD and the surrounded clay, and performance of the boards of GHD and the inside of the filled clay are detected using by the experiments and monitoring system. As the results, it is concluded that the magnitude of the friction depends on a strength of clay and the fill continues to be consolidated by the self weight to advance into stability. And infiltrating water is proved to soon dissipate and settle to the stable condition after raining.
Results derived from the measurement lasted for about more than two years after completion of the filling proved the embankment keeps stable.

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A new rockfall protection MSE-Wall (Mechanically Stabilized Earth Wall) by the reinforcement soil fill which used geosynthetics was designed, and developed. This rockfall protection MSE-Wall is a compilation structure with high energy absorption performance. It is composed of three materials such as the impact catchment bags, the impact transmission bags, and the MSE-Wall. To check the performance of the rockfall protection MSE-Wall, the actual rolling rock test was done. In the test, boulders of 1tf-15tf weight dropped from the slope of about 40m height to the rockfall protection MSE-Wall. As a result of the test, in the case of the falling rock energy was 230tf·m, the transformation of the wall was only 9cm, and it was able to catch the falling rock in all cases. The safety of the rockfall protection MSE-Wall against a very large-scale boulder was confirmed by this actual rolling rock test.

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A bearing capacity of geocell-reinforced grounds under repeated loadings was investigated by a series of field tests. Different sizes and rigidity of geocells which were made of veneer plywood, thin galvanized iron sheet and nonwoven geotextile were employed for the test. The surface deflection of test sections were observed until the repetitions of 1000 cycles of 1.7ton motor truck loading or their structural failure.
From the result of tests it was found that reinforcement effects depended on the properties of confined soil in the geocell and the supporting ground conditions. Moreover geocell materials of high rigidity demonstrated the good reduction of permanent surface deformation; however. progressive large settlement caused the failure of geocell itself. On the other hand a flexible geocell maintained the reinforcement effects on a severe ground settlement subjected to a large number of repetitive stresses.

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The preloaded and prestressed (PLPS) reinforced soil method aims at substantially increasing the stiffness of a geosynthetic-reinforced soil embankment by vertical preloading and prestressing. The first prototype PLPS reinforced soil pier for a railway was constructed, and preloaded and prestressed, which has been opened to service for more than 1 year. Long-term measurements for more than 2 years are described. The PLPS pier showed very small amount of instantaneous and creep compression by dead load and live train load. In addition, some new design and construction methods are proposed which can keep high stiffness for a long time and can improve its constructibility.

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A new construction technology has been proposed to increase substantially the vertical stiffness of GRS soil structures to make the deformation of the backfill in service essentially elastic, sufficiently large vertical preloading is applied to the backfill and to keep the stiffness of the backfill in service sufficiently high, preloading is not unloaded to zero, but sufficiently high vertical prestress is maintained within the backfill. In this study, a series of laboratory model tests were performed to quantitatively and separately evaluate effects of preloading and prestressing, and those of the use of tie rods for prestressing. It should be finally underlined that necessary and sufficiently large preload and prestress can be applied to the reinforced backfill. On the other hand, such levels of preload and prestress cannot be applied to usual unreinforced backfill without excessive deformation or even failure, therefore very high stiff backfill can be realized only when applying the preloading and prestressing method to appropriately designed reinforced soil structures.

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The reinforced soil has been widely used for constructing retaining walls and embankments with steep slope, stabilizing embankment on soft ground, and so on. However, the benefits of soil reinforcing are often restricted by a lack of good quality backfill material. In many cases, use of on-site high-water content and nearly saturated cohesive soil could save substantial cost. Plane strain compression tests have been carried out to study the effects of preloading and prestressing on the stress-strain behavior of geosynthetic-reinforced saturated clay, Kanto loam. The initial stiffness and ultimate strength of a reinforced clay during undrained shearing tests increase substantially by preloading and prestressing. With small prestress after large unloading from preloaded condition resulted into swelling of the soil, leading to a large reduction in the initial stiffness in undrained shearing. The results of compaction model tests have shown that reinforcement is essential for efficient compaction.

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Recent development of new geosynthetics such as composite fabrics has enabled the construction of steep earth fill using such as Kanto loam and/or construction by-products which have never been used as fill materials. Composite fabrics have almost the same tensile strength of geogrids also have the same drainage effect. The aim of this papar is to offer a fundamental data in order to develop a new design method of steep reinforced earthfill considering both reinforce and drainage effects. Therefore, comparison tests of model embankments have been carried out. This papar deals with two series of steep earth fill model test. One is earth fill reinforced with three kinds of geosynthetics, i. e; composite fabric (both reinforce and drainage effects), geogrid (reinforce effect only), and nonwoven fabric (drainage effect only). The step loadings were appried at the top of the fill after 53day's consolidation. Another is earth fill reinforced with composite fabric varying two laying pitches and no reinforced earth fill. The step loadings were appried after 4day's consolidation. Some useful findings have been withdrawn from the test results.

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As well as the sand erosion, the cliff erosion has still been an important issue to be solved from a viewpoint of the disaster prevention, environmental maintenance and landscape at the coastal area. In these five years the authors have been making an extensive effort to investigate the characteristics of the cliff erosion at laboratory and at fields of the coastal area in Northern Ibaraki. Among them, the present paper highlights the results from the wave tank model tests at laboratory which were carried out to investigate on what kind of the countermeasure method was most effective to protecting the coastal cliff erosion. As far as the countermeasures using the geosynthetics, were concerned, it was concluded from them that the geosynthetic-folded filter unit including the stone wastes inside was most promising enough for the present purpose.

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The “Geotextile tube dehydration method” is a construction method used to speed up the dehydration of soil with a high water content by packing it in permeable tube made of geosynthetic.
In this paper, we will outline the “Geotextile tube dehydration method”.
In the “Geotextile tube dehydration method”, the roles of the geosynthetic we expect is as follows.
a) Strength
b) Permeability
c) Easy Planting
d) Long-range Durability
We report each items in detail with actual examples.

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On the basis of the investigation results of the damaged embankments in farm land, the classification of the damage pattern has been presented. It is found that one of the cause of damage is the water-level in the embankment uprising, and the other is the seismic force acting on the mass of embankment. The trial application of the limit state design method to the design for the embankments in farm land is described. The reserve capacity in excess of the required capacity represents the safety margin. The reserve capacity on the seismic deformation for the embankment is calculated by the Newmark method. It may be possible to introduce the performance-based design on the deformation for the embankment in farm land.

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In recent years, a new material called geotextile filter material has come into use in the textile field. Geotextile filter material is a non-woven material made primarily from petroleum fibers. Manufacturers have offered various products in thicknesses, apprarent opening sizes, and tensile strengths, and because it is an industrial product, it is possible to obtain uniform material at a relatively low price. If it were possible to use this material as filter material in rock fill dams, the cost of dam construction could be reduced.
This report presents the results of a study of the feasibility of using geotextile filter material as filter material in rock fill dams. By installing geotextile filter material between the impervious zone and the semi-impervious zone of a rock fill dam, even though the filter is made of coarse gravel or other material that does not satisfy grain size standards.

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It is very important for aiding a safety designing with geomembrane to know stress and strain of the geomembrane installed on the ground of landfill. The relaxation test with constant strain and tensile test with the specimen after creep test had been conducted. After comparison of the stress-strain curve after and before relaxation test at 5% strain, the secant modulus obtained from curves are almost the same. So, when the stress of geomembrane is used for designing under the strain increasing condition, the decreasing of stress by relaxation must not be included in the stress calculation of stress.

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Geomembrane installed on the slope of landfill should be covered with geotextile for the protection. But the risk of passing of heavy machines or falling of waste exists. So, it is very important to study the puncture resistance of the geomembrane on the ground. From the test results, in case in the air, puncture resistance of HDPE is larger then EPDM, but in case with soil support, that of EPDM is larger than HDPE. And the puncture resistance on the ground can be evaluated by summation of ground resistance and puncture resistance in the air.

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With the revision of laws for improving waterproofing capabilities of ordinary waste final disposal plants, various waterproof structures and materials have been proposed. This cut-off sheets has been developed based on an epochal idea. Made of the material with self-repairing waterproof capability, it reacts to damage through direct contact between the damaged part and waste water, and repairs the damage by itself. This paper describes the results of laboratory and field tests of the membrane conducted in the course of its development, and presents cases of its application on actual sites.

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In lapanese waste landfill, from the view point of safety and security the geosynthetics clay liners (GCLs) are being employed as a maintenance of sealing water and protechtion of sepage water in a damaging sheet. But in the present condition, there are not any quality and standard in design and usage of GCLs. As it is not known in details regarding as kinds method of construction and characteristics of bentonite supported GCLs, we give a detailed description
A measurement of hydraulic conductivity was carried out in change of rapping width, the number of hole and hole diameter of the bentonite supported GCLs. And the consideration of quality standard are done for GCLs used in a waste landfill.

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When HDPE Geomembranes are installed in landfill, are subjected to differential settlement, tensile strain is induced. Therefore maximum strain in geomembrane should be estimated to check safety for tensile failure. Tensile behavior depends on the shape of settlement, thickness of protecting layer, the confining pressure and the friction property between the geomembrane and the ground. In this paper, model tests where Geomembrane was subjected to differential settlement were conducted under conditions that thickness of protecting layer and stiffness of geomembrane are constant, and the surcharge pressure is varied. The effects of displacement and surcharge on maximum strain, distribution of strain and elongation of the geomembrane were compared to the calculated results based on Trough Model and Elastic Formula.

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The ground replacement method reinforced by geonet is used for improving the trafficability on soft clay in the temporary road construction. Its design method is based on the surface stabilization method using geosynthetics on soft clay ground. However, the field work is different from the design work.
Therefore we have considered the mechanical behavior of geonet in ground replacement method, and we propose to the design method which applied to this method.

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Recent development of new geosynthetics such as composite fabrics has been able to construct steep earthfill used high water content volcanic cohesive soils such as Kanto loam and/or even construction by-products which have never been used as fill materials. Recent developed composite fabric has almost the same tensile strength of geogrid and of course drainage effect. However, current design method of the steep reinforce earthfill with nonwoven fabric has not considered its reinforced effect and strength increase of cohesive soil by consolidation. Therefore, this paper proposes a new design method of a steep reinforced earthfill taking strength increase of high water content volcanic cohesive soil by consolidation, A characteristics of soil-fabric interface and reinforced effect of composite fabric into account.

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As a method to Geosynthetic-Reinforced Retaining Walls with a rigid facing, for temporary stability of backfill till the execution of wall concrete, Pre-Support Materials have been manufactured by well drainage gabions. As the manufacture of the gabion is not efficient at all, it is a prerequisite to save man power, for a wide range applications of this construction method.
This paper reports the applicability of L-shaped welded. wire netting instead of the gabion as Pre-Support Materials and form-use precast concrete panel as structural members. The applicability are found in loading tests on the full-sized Geosynthetic-Reinforced backfill about deformation by rolling compaction and loads on the bank, and the difference of concrete wall strength between monolithic and complex composition by precast concrete panels.

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FE analysis of plane strain compression tests on an unreinforced specimen and geogrid-reinforced sand specimens were conducted by nonlinear elasto-plastic FEM. The sand specimens was reinforced with 6 or 11 layers of geogrid. In the FE analysis. strength anisotropy, pressure dependency of strength, strain-hardening and -softening and shear banding (or strain localization) were considered for sand. The geogrid was modeled as a planar reinforcement in the plane strain FE analysis. By integrating the results from the FE analyses and the physical tests, the effects of reinforcement rigidity. covering ratio and interface friction angle on reinforcing effects and the dilatancy characteristics of reinforced sand were evaluated. A quantitative relationship was obtained between the reinforcement covering ratio of actual three-dimensional reinforcement and the equivalent interface friction angle in the 2-D plane strain FE analysis. Lastly, the effects and mechanism of the reinforced sand were evaluated based on the local stress paths within the reinforced sand.

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Non-woven geotextile is often used as horizontal drainage for stabilizing embankment with high water content cohesive soil. In order to rationalize the design method, it is needed to establish stability analysis method, which is able to consider the effect of layout condition of horizontal drainage. In this paper, limit analysis method for stabilized clayey soil embankment using non-woven geotextile are proposed, the effect of layout condition of horizontal drainage is examined by conducting numerical analysis.

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A series of shaking table tests were conducted in a 1-g gravity field in order to evaluate the performance of the geosynthetics-reinforced embankment on liquefiable sand layers during earthquakes. Those shaking table tests focused their attention on the influence of the types of reinforcement and the existence of replaced gravel on the liquefaction-induced displacement of an embankment. The conclusions obtained from this study are as follows; 1) It is impossible to prevent liquefaction itself without replaced gravel layer. However, while the acceleration is small, the geo-synthetics reinforcement restrains liquefaction-induced displacement. 2) In general, by combining reinforcing with geo-synthetics and replacing with gravels, the embankments show high stability.

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Many water front structures were heavily damaged during the 1995 Hyogoken-Nanbu earthquake. Shaking table tests were performed in order to understand the mechanism of deformation in the reclaimed ground and to evaluate the potential of geo-synthetic reinforced caisson type quay wall. The conclusions obtained from this study are as follows: 1) While the acceleration is small, the geo-synthetics reinforcement restrains liquefaction-induced displacement. 2) By reinforcing the backfill ground in such a way that it is surrounded by geosynthetics and caisson, the movement of the caisson can be reduced effectively.

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We have studied effects of horizontal reinforcements in a soil embankment focusing on residual deformations of slopes during earthquakes, by performing shaking tests using 5 embankment models with/without reinforcements under a centrifugal acceleration of 50G, and obtained findings as described below:
(1) In reinforced soil embankments, the residual deformation was much smaller than that in a embankment without reinforcement.
(2) Mitigation effects of residual deformation increased as the reinforcement length increased, and tended to be insignificant when the reinforcement length exceeded certain level.
(3) Acceleration response was large in cases where the mitigation effects of reinforcements on residual deformations were significant, showing a relatively high rigidity due to the reinforcements.

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This paper presents the new design method for the geosynthetic reinforced-soil retaining wall with full height rigid facing (GRW) against strong earthquakes. Proposed new method is verified using the case history of GRW which encountered the Hyogoken-Nambu earthquake. This method consists of two procedures; the first one is the seismic stability analysis, and the second is the permanent deformation analysis. The proposed method adopts a modified theory of earth pressure considering the strain localization in the backfill soil and a new method to estimate the residual shear deformation of reinforced backfill. The results of the verification analysis could nearly represent the actual behavior. Trial designs are also conducted by varying the backfill material parameters in order to select the appropriate soil type.

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Since preloaded/prestressed (PL·PS) reinforced soil method had been developed, various researches have been done. These results indicate that preloaded/prestressed reinforced embankments have high stiffness and superior feature on residual settlement against vertical load. But there is no researches on earthquake resistance, which is one of the most important performances, and even no research on horizontal deformation characteristics, which is a basis of earthquake resistance characteristics. Preloaded/prestressed reinforced soil structure must always keep high prestress. If cyclic load is applied to preloaded/prestressed reinforced soil structure in a lateral direction, there is a possibility that all or part of prestress is lost. If all or part of prestress is lost, the structure can not have high stiffness.
As one of studies on earthquake resistance of preloaded/prestressed reinforced soil structures, shaking table tests on retaining wall models are conducted to study the feature of lateral deformation. It was found that preloaded/prestressed reinforced soil structures have superior deformation feature against lateral cyclic load.

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With regard to Large Diameter Reinforced Anchor which is the improved Earth Reinforcment, the characteristics of the hollow FRP rods made by Vinylon for the reinforcement of soil cement colum are reported. Many merits were obserbed by hollow rod like bamboo shape compared with standard round rod or strand rod. Hollow rod dissolves the problem of the dimentional unstability for 7 strand rods, improves the tensile strength and better adhesion with concrete because of bigger surface area. Moreover, the simple end fixing of rod were realized because the end of hollow rod were divided into 6 pieces and locked by conic wedge. Regarding the durability of Vinylon FRP rod, alkaline resistance and creep raputure were measured by the standard of the Japan Society of Civil Engineers and suggesut the long durability for that.

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A method of estimation of in-soil deformation behavior of geogrid, the end of which is fixed to the ground, by using the results obtained from soil-geogrid direct shear test was proposed. From a series of calculation performed by changing the embedment length or the stiffness of geogrid, it was found that the longer the length or the smaller the stiffness of the geogrid, the smaller the influence of the end restraint (free or fixed end) on the in-soil deformation behavior of geogrid. It was also found that the pull-out force versus displacement relationship at small displacement is strongly dependent on the stiffness of geogrid irrespective of the embedment length of geogrid and the condition of end restraint in the ground.

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In order to investigate the deformation and strength characteristics of reinforced sand, a series of direct shear tests were performed. Phosphor bronze strips or sheets were used as reinforcement. Constant volume tests, as well as constant pressure tests, were conducted with different forms of reinforcement stiffness, surface area and surface friction. Test results show that the reinforcing efficiency is higher for reinforcement with larger surface area and rough surface texture. The dilatancy and shear displacement at the residual state also depends on the reinforcement property and geometry. The shear zone become wider in tests on reinforced sand than in tests on sand alone. As high dilatancy of reinforced sand, the peak shear stress and peak vertical stress increase a great deal than those of unreinforced sand.

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Reinforcing effect of geogrid-reinforced soil structures is evaluated by the tensile force of geogrid. However, our research has made clear the existence of the additional confining effect which is independent of tensile force of geogrid.
The factors influencing the confining effect are the shape of geogrid, the density of soil and so on. In this paper, we experimentally examine the effect of the shape of geogrid. In order to evaluate the shape characteristics quantitatively, the shape index, R, has been proposed. The relation between Shape Index, R, and the confining effect was shown.

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A quantitative evaluation of confining or restraint effects which are recognized as one of the fundamental mechanism of earth reinforcement is made in this paper. Firstly a confining stress increment caused by friction between soil and geosynthetic reinforcement material is analyzed phenomenologically. Secondly a uniaxial compression test is carried out for a sand specimen (air-dry Toyoura sand) confined by a geotextile cylinder. A radial normal stress component in the specimen induced by the application of axial compression load is calculated and a hoop tensile stress of geotextile is measured using a pi-meter.
Confining effects equivalent to the frictional effects between soil and geotextile are estimated based on the equilibrium of force. A fair coincidence was obtained between the analytical result and the measured one. In addition the increase in the safety factor was demonstrated based on the reinforcement by confining effects.

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Reinforcing technique of embankment with geo-composite, which has draining function and reinforcing function, is effective for the most of high water content cohesive soils. In order to reinforce embankment efficiently, it is important to understand the interaction property of clayey soils and Geo-composite. Authors discuss on the direct shear strength of clayey soils and geo-composite by conducting the constant volume direct shear test.

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Interface friction between soil and fiber and their interlocking are considered as fundamental factors of mechanical improvement of fiber-reinforced soils (so-called internal reinforcing). In order to study the quantitative effects of the surface roughness fiber on strength and deformational properties, box shear and unconfined compression tests were carried out using cohesion less soil (Toyoura sand) and cohesive soil (a mixture of Toyoura sand and Kaoline clay).
It was found from the test results that both internal friction and cohesion components were increased with the mixing rate of fibers, and the higher degree of fiber's surface friction improved their peak strength, residual strength and ductility.

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It is need to understand concern with settlement of embankment and wall face deformation, strength of geogrid and earth pressure of back the wall, to recognize stability of geogrid reinforced wall with wall block used dry construction method.
We were constructed the 8.0m test embankment of geogrid reinforced wall with wall block used dry construction method. The test embankment was set earth pressure gauges of back the wall and on base, strain gauges on the geogrids and settlement plates in back fill. It was observed deformation of the wall face, top of the embankment and settlement plates about one year.
Next we were trying FEM analisys. This FEM analisys is used double contact point method, because it is able to think friction coefficient of soil and geogrid and wall block and geogrid, . In result FEM analisys of double contact point method is useful for geogrid reinforced wall with wall block used dry construction method.

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Not only the reinforced embankment with geogrid but also the retaining wall with concrete box-type wall have become popular geotechnical structures. This is because the effectiveness and reliability for those structures have been well evaluated. On the other hand, the ground conditions and the circumstance where these structures are constructed have become more complicated, so that the combined technique for those two structures has also been conducted nowadays. It is expected for this combined technique that the advantages for both structures have to be well performed individually. So far, not many measurement data for this combined technique at real construction site have not been obtained and the accumulation of these data is expected in order to evaluate this combined technique quantitatively. The objective of this paper is to evaluate the reinforcing effect for this combined technique based on the measurement data at the real construction site of road embankment in Kyushu, Japan. At the construction site, earth pressures, deformations of the backfill and geogrids, and pore water pressure were measured during step by step construction. Finally, the effectiveness of the use of geogrids for concrete box-type retaining wall was discussed based on those measured data.

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