A unified view about the design strength of nonwoven fabric has not yet been reached. To clarify the design strength, the biaxial tensile tests were performed.
In consequence, nonwoven fabric which was confined the lateral face showed approximately a 15% decrease in strain when compared with non-confined nonwooven fabric. The rate of decrease could be explained by biaxial Poisson's Ratios. Tensile strength also increased 15% when compared with non-confined nonwooven fabric.
However the tensile strength was less than what was estimated by the slope failure test. It is necessary to examine a study as compositions of sand and nonwooven fabric.

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The creep characteristics of spun-bonded non-woven fabrics were investigated using a plane strain creep test.
200mm wide samples were used. Several light weight hinged rods were spaced on the sample. These rods are fitted with pins which pierce the fabric and resist contraction during the test. The test temperature was maintained at 20±2°C.
According to the test results, creep deformation characteristics varies largely with the type of fabrics. In the case of fabrics made from polypropylene, creep deformations increase rapidly as the applied stress level increase above 10 to 20 percent of the maximum tensile strength, but in the case of fabrics made from polyester, creep deformations do not increase largely below 60 percent of the maximum tensile strength.

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We have developed Geocomposite used as both reinforsing and drainage material, which is composed by three layers (nonwoven-woven-nonwoven).
For this geocomposite, we have done wide-width tensile test and long term creep test, and estimated the mechanical property.
Judging from the test results, we confirmed that this geocomposite has advantageous property for reinforcing material compared by non-woven Geotextile, and we considered the long term mechanical property (creep, relaxation) in soil structure.

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The geogrid tensional farces were measured in three cases of gogrid-reinforced embankments with different fill materials and slop angles in order to check if three available design methods for such embankments are applicable or not. As a result, measured gogrid tensional forces were found to be much lower than the design forces; current design methods for this purposeuare very much on the safe side.

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To investigate the reinforcing effects of geotextile across slip surface in soil, a series of special direct shear tests was performed on sand reinforced with geo-grid. In the direct shear apparatus, a geotextile was buried across the slip surface in soil box.

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In this paper, the auther shows the principle of the displacement method for the stability analysis of the reinforced structures by the geotextiles. This method, which has been developped in France, is based on the limit equilibruium considering the deformations of geotextiles. Then, an interpretation of the data is presented on the failure experiment of full-scale reinfoeced retaining wall carried out at Public Works Research Institute. The failure was induced through dead weight by the cuttings of the geogrids in the backfill. The displacement method gives a good accordance of the strain distribution along the geogrids after construction. And the evolution of the factor of safety principally explains a series of changes observed during the experiment, that is, the occurence of cracks at the top of the backfill, their developments and the entire failure of the rataining wall.

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In constructing a retaining wall at a place adjacent to the abutment wing wall of a bridge. A new method of direct-foundation type construction by means of reinforced earth has been proposed here insted of a pile-foundation-reversed T type conventioal concrete one. In that the multi-anchored vertical faced earth-wall reinforced with polymer grids is employed and also preloaded to reduce the residual settlement that results from the wall's contact with river water. A vertical faced reinforced-earth test-embankment is constructed to check and verify the applicability and effectiveness of the method. The report deals with these tests and practical behaviors of the wall.

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Full-scale loading tests on sand embankments which were reinforced with geotextiles were carried out in order to investigate the reinforcing effect of geotextiles.
Test conditions were as follows. (1) Geotextiles (Hard type, Soft type). (2) Inclination of slope (1:1.5, 1:1). (3) Loading position (top of slope, 1m from the top) (3) During the loading tests, the surface deformation of the slope, the stress of the geotextiles and the vertical loading pressure were measured.
The test results showed that the condition of the loading position was most significant.
In the case of loading on the top of the slope, the effect of geotextile reinforcement was noticeable. On the other hand, backside loading test results didn't show a clear difference in the load-settlement curves between reinforced embankment and un-reinforced one.

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When the geotextiles are used in drainage applications, the relationship between the opening size of geotextile and soil particle size becomes a essential factor. In this paper there methods have been used to measure the opening size of geotextiles. The results indicate that the method which water drains out and washes soil particles through the geotextile is suitable for needle-punch nonwoven whose opening size is finer than 50μm.
Next, the clogging tests on five geotexile samples with silty sand were carried out, and the test results were compared with the typical filter criteria already formulated by some reseachers.

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A testing apparatus has been developed to measure the hydraulic conductivities both normal to and in the plane of a geotextile specimen. For the in-plane flow condition, the system is also capable of measuring the hydraulic conductivity of the geotextile in the confinement of a soil under a specified confining pressure. This paper briefly describes the apparatus, the testing program and the in-plane hydraulic behavior of a nonwoven geotextile and a woven-nonwoven composite geotextile. The test results show the requirement of in-soil testing for actual simulation of the field condition.

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Non-woven geotextiles have been used worldwide as drainage and filteration materials. But the permeability of geotextile depending on surcharge has not been yet estimated clearly, so a testing apparatus has been developed to measure the permeability normal to geotextile specimen under confined conditions. We tried the permeability test of geotextile with this apparatus. In this paper the cross-plane permeability of a nonwoven geotextile and a woven-nonwoven geocomposite under confined condition is described.

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The serious damages to the sand liquefied groud by earthquakes are often reported everywhere in the world.
Now, a preventive method is developed by means of installation of the drainage of excess pour pressure by the use of geosynthetic board drains.
The drain materials are easily transported anywhere to the sites by the roll package. Each of the drain material is inserted into the ground through the mandrel like the general vertical drain method.
For designing the intervals of the drains to be inserted, large scale vibration table experiments and field vibration tests were performed. The effect of this preventive method using geosynthetic board drains against liquefaction was well verified available as the preventive construction method against liquefaction.

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The paper presents a simple method for the evaluation of laboratory discharge capacity of Plastic Board Drain (PD) which has been widely used as vertical drain for the improvement of soft ground. The effects of confining pressure and local bending deformation on the discharge capacity values of various drain types were investigated in detail. It was found from constant head permeability tests that the discharge capacity is significantly decreased due to the increase in confining pressure and the local bending strain. It was also found that the flow inside the PD is not laminar and hence Darcy's law cannot be applied for the evaluation of permeability. Lastly, a simple design method to obtain the required discharge capacity of PD has been proposed.

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Large-scale model tests were carried out under artificial heavy rain conditions to study the behavior of 5m hight steep slope embankments having soil-walls reinforced by continuous threads. The erodability of the soil-walls and the stability of the embankments were examined.
According to the test results, it was concluded that the soil-walls reinforced by continuous threads are highly resistant to erosion due to rain and that the stability of the embankment having soil-walls can be analyzed using circular slip method if soil-walls are thin, or conventional design method for concrete retaining walls if soil-walls are thick enough.

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This paper presents an experimental study on the performance of 6m high grid reinforced embankments, subjected to additional loading after construction. Additinal loading was applied by a surcharge of a 3m high filling, then submerging the structure in water, then rapidly lowering the water level outside the embankment.
The embankments were constructed with 1:1 slope using silty sand and instruments were used to monitor the deformation of the embankments as well as strain levels in the polymer grids.
On the basis of the mesured grid strain distribution during loading, the current design methods, such as the limit equilibirium method, and the critical safety factor where the reinforcement strains largely increase, were evaluated.

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With the aim of assessing the biaxial tension in the geotextiles laid over a soft ground and underneath the embankment thereon, measurements have been taken through biaxial tension measuring sensors attached to the geotextiles. The results have validated that the textiles were subjected to a biaxial tension while embankment was being carried out and that the axial tension registered the peak value immediately following the embankment and then reduced thereafter.

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Estimating the stability of geogrid reinforced embankment in consideration of deformation behavior, it is indispensable to grasp the displacement dependence property of pull-out resistance of geogrid in soil.
In this paper, an equation is deduced on the relation between pull-out resistance and pull-out distance taking account of strain distribution of geogrid. It has three constants of geogrid's break strength, brew strain and minimum length required to break. The measured results in pull-out test are in good agreement with the theoretical values.

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This paper describes about the pull-out resistance of geogrid employing the soil material which was used to build a reinforced embankment in Niigata prefecture, and also refers to the friction coefficient which works between soil and geogrid. According to the verification, the finite element analysis which used joint element method satisfied the experimental result. On the other hand, it was shown that the friction coefficient is gradually decreases with increasing the normal stress.

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The most common test used to measue the interaction between soil and geo-grid is the pull-out test. The distribution of pull-out resistance of geo-grid in soil, however, is not uniform. The test results obtained with pull-out tests is affected considerably by the non-uniformity.
This paper attempts to investigate a suitable method by which can obtain the pull-out resistance parameters of geo-grid in soil (c*, β).

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This paper introduces a new apparatus which is capable of carrying out both “Pull-out test” and “Direct shear test” of geogrid reinforced soils. And by the results of both tests carried out, the difference and relationship between the pull-out resistance and the direct shear strength were discussed.
Main conclusions obtained from this study are as follows:
The pull-out shear stress and the shear stress in each pull-out test and direct shear test may be related in each other for the small value of the vertical confining pressure. But when a large value of the vertical pressure is applied, those relations between the results of both tests are not always hold good.

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The most common test used to measure the interaction between soil and geo-grid is the pull-out test. The distribution of pull-out resistance of geo-grid in soil, however, is not uniform. The test results obtained with pull-out tests are affected considerably by the non-uniformity.
This paper attempts to investigate a suitable method by which can obtain the pull-out resistance parameters of geo-grid in soil (c*, β).

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The design method for steep embankments reinforced with geogrids is usually adopted in Japan on the basis of Jewell's two-part wedge analysis. However the assumptions that are made in Jewell's method differ from the Japanese embankments or retaining walls design criteria and hence the adopted design method gives results on the safety-side, which was found out from field measurements of test or practical construction. In this report the revised design method is proposed with a view to obtain an optimum design method for the steep reinforced embankments.

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The existing state and the point at issue for the design methods of the geogrid reinforcedsoil wall are examined and the procedure to perform its design reasonablly are investigated. On the basic of the investigation, a design method of the geogrid reinforced-soil wall is proposed and the comparison with the design methods which have been currently used is performed and discussed on its results.

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Investigations to the execution of the construction methods using Geogrids were conducted for the stabilization of soils having found the problems arising from the field working sites. This abstract is made from some of such problems in line with those of the connection and laying of Geogrids.
Since the laying work of Geogrids is observed quite simple and the detailed execution methods of Geogrids are not always specified at the working sites, there frequently exsist uncleared understandings for the details during the course of the works.
This abstract focuses on the such problems and suggests the some solutions towards them for the smooth execution.

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