A series of model shaking table tests and their stability analyses were performed with an aim at estimating the earthquake resistance of geotextile reinforced embankments.
Test results showed that the earthquake resistance increases when geotextiles are thickly included, geotextiles with large stiffness are used, and a slope surface is rolled up with geotextiles.
A few variations of stability analysis formulae were briefly reviewed. The simplest analysis assuming a given constant elongation of geotextiles showed a fairly good agreement with experimental results. Another stability analysis which pursues a consistent strain of soil and geotextile was also conducted and compared with experimental results, which gave a fairly larger strain of geotextiles in case of non-woven fabric.

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Shaking table tests were conducted on saturated sand layer reinforced with wires in order to apply reinforced earth method to liquefaction countermeasure method.
In this paper, the effects of placing direction, reinforcing range and stiffness of reinforced materials on the liquefaction resistance are investigated. Shown below are results of this tests.
i) Reinforcing effect is confirmed on shaking table tests.
ii) If reinforcing effect is greater for vibration at low acceleration ratio than for vibration at high acceleration ratio.
iii) Reinforcing effect is greater as stiffness is greater, reinforcing interval is narrower and reinforcing area is wider.

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Whether the earth pressure working on the back face of retaining wall is reduced effectively by using short and planar tensile-reinforcing members, which are not connected to the back face of the wall. It is apparent that the reinforcing effects decrease by not connecting the reinforcing members to the wall back face. However, the connections may be damaged by possible relative settlement between the wall and the back fill.
It was found from the small model tests that the earth pressure on the wall is remarkedly reduced by reinforcing the back fill even if the reinforcing members are not connected to the wall back-face. The failure mode of the back fill when a load is applied to the crest was found to be the sliding along a shear plane created in the reinforced zone, as compared to the failure mode of overturning of the reinforced zone together with the wall when the reinforcing members are connected to the wall back-face.

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The numerical analysis is carried out to reinforced earth retaining wall model tests by using RBSM model proposed by KAWAI. The result obtained from this method shows the good approximation comparing with test results. And the followings become more clear;
1) The lateral pressure at the retaining wall decreases by reinforcing membrane.
2) The points of maximum axial strain of reinforcing membrane are located near the edge of plastic zone in the soil embankment.

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An earth pressure acting on a retaining wall with polymer grid reinforced soil backfill and a deformation of the wall are analysed by the method which is capable of taking into account the displacement dependence property of the pull-out resistance of the polymer grid in soils. Two types of the wall systems, which are rigid and flexible, are analysed. The relationship between spacing and length of the polymer grid and the reduction effect of earth pressure and deformation of the wall is discussed.

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In December, 1985. We built a multiple anchored retaining wall of 5m in height, using geotextile. In order to study the effects of surcharge on the geotextile faced retaining wall, a fill-up was made on this retaining wall in June. 1986. The surcharge consisted of three different types retaining walls and a slope. And it was made 5m in height using cohesive soil.
In August 5. 1986, one of the retaining walls. multiple anchored geotextile retaining wall with 2m long steel bar anchors collapsed due to a heavy rain. approximately 240mm per 20 hours and resultant percolating water.
The mechanism of rupture are investigated.

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A series of testings on earth embankments had been conducted with a view to formulate a rational design as well as a proper construction technique of polymer grid reinforced embankment. In practice experimental embankments (height 3m, slope 1:0.7) were constructed laying in the earth-fill polymer grids at various lengths and at various spacings in the vertical direction. Tests were also done for both cases of embankment with and without slope protection measures. A comparative studies of grid reinforcing effect was carried out by conducting tests on embankments under heavy rain (reinfall intensity 15mm/hr) and reinforcing effects of grids as a result of integration of earth and grid was under special scrutiny. In this report a summary of test results were described. The FEM analysis based on elasto-plastic models was performed using these results. It was confirmed that models simulate the actual conditions of practical construction.

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Direct shear tests have been done with a large scale shear testing apparatus, in order to investigate the shearing characteristic between geotextile and soil, which is one of the basic and very important properties in application of geotextiles to the earth works. Tests have been carried out with three types of geotextiles, varying soil conditions and codition of shear test.
The results are following; First, the friction angle between plastic net and soil, and also non-woven fablic and soil can be considered nearly equal to the angle of shear of soil, regardless of the difference of water content of soil or soil types. On the contrary, geomenbraine shows lower angle of friction on condition of wet soils. And, with cohesive soils, any type of geotextiles indicate the same aparent cohesion as soil.
Further consideration has been added, on the basis of the resuls above, to the estimation of ancor length of geotextiles against the pull-out force.

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Large triaxial compression tests of Toyoura-sand reinforced with a single layer of polymer grid, plastic net or non-woven fabric were carried out. By measuring the strain of geotextile moblized with compression, the reinforcing effect and the reinforcing mechanism were investigated.
It was found that failure mode changes with confining pressure, and that the increase of the maximum deviator stress by geotextile layer can be estimated with the tensile strength of the geotextile, and that the increase of the deviator stress at any axial strain by geotextile layer can not be estimated only with mobilized tensile force of the geotextile.

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A reinforcing mechanism, and strength and deformation characteristics of the reinforced soil have been investigated by a laboratory element test using a small size specimen. However, the properties of soil that reinforced with a full scall reinforcing material can not be studied by the laboratory test as the size of specimen is very small.
In this paper, a series of large scale triaxial compression tests were performed in order to investigate the strength and deformation characteristics of sand that reinforced with full scall reinforcing materials (geo-grid, non-woven and metal strip for terre armee). The tests were carried out on a dry sand sample, the results were represented by comparing the stress-strain relation of reinforced sand with that of unreinforced sand.

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A test device and method for a practical, accurate in-plane permeabillty test for woven and nonwoven geotextiles has been presented. The test apparatus uses parallel flow of water through a geofabric specimen measuring 20cm by 20cm and is capable of testing not only a single layer of geofabrics but multiple layars and soil-fabric-soil composites. The range of vertical stress that can be applied to the specimen is up to approximately 5kgf/cm². Based on the comparison with the results of bentonite-coated specimens, it is concluded that no significant leakage occurs along the boundaries of a geofabrics specimen during the in-plane permeability test. The coefficient of permeability of geotextiles is maintained constant under a constant vertical stress applied to their plane, but decreases markedly with increasing stress.

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A method of preventing leakage through the bottom of a large reservoir by adapting a geomembrane placed on the bottom. A large-scale permeability test was performed before designing this method, and the report of this test was given at the 3rd International Conference on Geotextiles. Geotextiles, which were placed under the geomembrane, were compressed by water pressure and became impermeable. Water, through defects in the geomembrane, did not flow horizontally through the geotextile which was deemed permeable. As a result of the test the following was proved: that geotextiles helped close the contact between the geomembrane and the rough ground surface, and prevented flow through cavities caused by the rough ground surface. The geotextiles had the double advantage of having a cushioning effect and preventing horizontal flow under the geomembrane. The research work was performed to investigate the leakage phenomena through the geomembrane having defects.

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In the packed-drain method, surcharge pressure considerably concentrates on the sand piles due to a reinforcement effect of the stocking, and it causes a reduction of the consolidation pressure for the soft clay.
To avoid this problem, a packed-drain of which diameter expands as the ground settlement progresses was developed by utilizing a moisture weakening fiber for the conventional packed-drain stocking.
A large scale labalatory test was carried out using a 3.0m high consolidation cylinder, and the effectiveness of the developed packed-drain was proved.

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For the purpose of making clear the effectiveness of reinforcement of embankment using a nonwoven fabric as a tensile-reinforcing material, loading model tests were conducted.
We made a reinforced Kanto Loam embankment, having a steep slope inclined at an angle of 73°, by laying nonwoven fabrics horizontaiiy and rolling up along the embankment slope.
We carried out two cases of loading tests, for embankment reinforced with a nonwoven fabric and unreinforced embankment.
The results of these tests may be summarized as follows;
a) Local collapse of slope can be prevented by reinforcing embankment with a nonwoven fabric.
b) Yield load of reinforced embankment is about 3.6 times as large as that of unreinfored embankment (for Kanto Loam of Cohesion: C=0.1kgf/cm², Internal friction angle: φ=10°).

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In order to carry out stability analysis of reinforced embankment, a method of analysis was developed which will express accurately the slipping at interface between soil and reinforcement or breaking of reinforcement. We studied an effect that a change of a length, an interval and a tensile rigidity of the reinforcement gived a stability of it for assumed reinforced embankments by Finite Element Method using joint element. So, we constructed a reinforced embankment by Polymer Grid, measured a strain of Polymer Grid, compared with analysis.

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When geotextile is placed between a soft subgrade and aggregate layer, the bearing capacity of road system is significantly improved. In such application the basic function of geotextile are as follows: (1) confinement of subgrade soil and aggregate layer, (2) reinforcement by vertical compornent of tensile stress develops in geotextile, (3) material saparation. In this study, based on the results of two dimensional model tests, especially the first function is investigated.
Geotextile reduces the stress transmission to subgrade and restrains the sliding failure of subgrade soil on both side of loading area. Next, the reinforcement of aggregate layer by geotextile is due to increasing of holizontal confinement stress, and it seems that this function has important effects upon the bearing capacity of road systems.

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At the first stage, static triaxial compression tests were conducted on models installed singular geotextile-grid-cell and compared the difference in stress and modulus of deformation with geotextile plane installed horizontally and without geotextile. At the second stage, unconfined compression tests were conducted on the models installed plural geotextile-grid-cells in dry and wet conditions.
Dynamic triaxial tests were conducted on models installed singular geotextile grid-cell.

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This paper describes large-scale model tests investigating the effects of spun-bonded non-woven fabrics for the drainage system and reinforcing material in the embankment under heavy rainfall condition.
The test were conducted, using the embankments reinforced by the non-woven fabrics with two kinds of thickness.
The main test result shows that these non-woven fabrics are useful for reinforcing materials and a thick fabric can be used for the drainage system, but a thin one laid into a embankment have little drainage effect.

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In this paper, The stability of slope of the embankment reinforced with spun-bond non-woven fabrics under the effect of a seepage flow caused rainfall and the practical application of stability analysis are discussed, using the results of large-scale model test.
The test varing the types of fill material and lengths and spacing of non-woven fabrics laid in the embankment were carried out. Their studies reveal that reinforced embankments are able to have high stability of slope under the heavy rainfall and the results of stability analysis based on the rational estimate of tensile strength of non-woven fabrics in the embankment coincide with those of model tests.

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