This paper describes model tests investigating the feasibility of utilizing polymer grid for suppressing the differential settlement of asphalt pavement constructed on a very soft clay, the Ariake clay ground. Repeated loading tests were carried out on pavement models of 2.2sq.m and 1m depth of a standard specification and those reinforcement by polymer grids in several geometries. The main results derived from are as follows: Polymer grid placed at the interface between base course and subgrade (the Ariake clay) contributes effectively for suppressing the differential settlement of pavement; Maximum pull-out resistance of polymer grid in subgrade, Tmax, closely depends upon the shear characteristics of the soil, Tmax/L=αc_u+σtan (βφ), where α=0.53 and β=0 for the Ariake clay.

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A new transmissivity test is proposed to determine the drainage characteristics of geotextiles for design purposes. The test results give both the vertical and horizontal permeabilities under the condition of one-dimensional compression. The paper describes the testing apparatus, the method to calculate the coefficient of permeability, the drainage characteristics of nonwooven fabrics and the behavior of a combined body of soil and fabric.

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We used the non-woven geotextile for the drainage system and reinforcing material in the steep slope embankment. This embankment was left in outdoor for three years and three months. It was inrestigated that the geotextile had contributed for stabilizing the embankment. Then we took to pieces of this embankment, and picked up the geotextiles in the soil. We estimated the endurance property of non-woven geotextile in the soil with tensile strength, elongation, tear resistance, thickness, unit weight, and water permeability. In the result the property of geotextile did not become weak at all, and we have no problem for using the non-woven geotextile in the soil obviously.

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Undrained cyclic torsional simple shear tests were conducted on sand samples reinforced with wires, copper plate, non-woven fabrics in order to apply reinforced earth method to liquefaction countermeasure method. In this paper, the effects of placing direction and stiffness of reinforced materials on the liquefaction resistance are investigated. Shown below are results of this tests.
i) Reinforcing effect is greater in case of putting materials to direction of principal stress.
ii) If reinforced materials are placed to the other direction, the reinforcing effect depends on the stiffness of reinforced materials.

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In earth filling work on very poor clayey ground utilizing geotextiles, rational estimation of sand volume needed for sand layer construction is required. A new estimation method was proposed by authors where the distribution model of sand layer thickness is expressed by logarismic normal distribution. First the estimation procedures on the actual work using new method are described. Then a detailed comparison of the construction results and the estimation results was made. The applicability of proposed method was investigated and it became clear that the new estimation method was useful.

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We were able to place the static load (60ton steel plate) and Dynamic load (Dump truck weight about 20ton) on the Fabric reinforced wall which had been completed in Feb. 1986 in order to evacuate the critical condition of the wall's behavior. We measured their displacement in horizontally and vertically their settlement by the buried instrument (horizontal inclinometer, pressure gauge and horizontal displacement gauge, etc.). Through these experiment, we learn that the effect by Dynamic loads was smaller and the face of wall moves forward by bigstatic loads near the top of wall. We recognized that nowadays Reinforced Fabric wall designmethod is safer than anticipated condition and Safety Factor about their pullout resistance and Rupture resistance Safety Factor 1.5 is reasonable. The displacement and vertical pressure occured during their construction was larger than those measurement this time so we convinced that the constructability and survivability is more important.

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The method of steep reinforced embankment using high tensile polymer grids has to be formulated with several assumptions. The present paper deals with instrumented constructions to evaluate them.
In two cases of construction, one vertical and the other slanting, several layers of grid are laid in the embankment. As a result of it the tension on the grid is considerably reduced compared with designed tension.
These studies reveal that the reinforcing effect is higher than that of the design assumption as the fill material is integrated with polymer grids laid in the embankment. The authors are of the opinion that such an integrated effect should be incorporated in the future designs.

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The chemical board vertical drain method using nonwoven fabric has been spreading rapidly as a method to improve soft ground for the reasons that on land there is no disconnection of the draining section, its handling is easy, execution of work is simple and the drain can be placed at short intervals and the cost of the work is inexpensive. However, because of a problem in the cutting of the drain under water, its placing in water had not been done so far.
At this time a cutting mechanism of the draining material in water has been developed, incorporated in a nonwoven fabric (TAFNEL) drain method and its water placing method established. Draining work extending to 330, 000 meters on the sea was executed and extremely good results were obtained from the records of measurements made with the passage of time.

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Series of laboratory pull-out tests were carried out using fore samples of geotextile and two sands. When the pullout force acts on geotextiles embedded in sand, two critical modes that are pullout failure and tensile failure of geotextile are observed. It seems that these two failure modes are closely related to confining pressure and deformation modulus of geotextiles. Also, in the pull-out test the nonuniform shear stress distributions occur along the specimen, so in this paper effective shear length that is obtained from the pull-out experiments introduced to consider the pullout resistance.

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The creep characteristics of geotextiles under sustained load are important for their satisfactory performance in civil engineering. In this paper, series of laboratory creep tests are carried out and typical test results are given for some wovens and nonwovens. They indicate that creep resistance of needle-punch nonwoven and multi-filament woven are larger than heat-bond nonwoven and mono-filament woven made from polypropylene. Also the test results are analyzed to investigate their creep parameters based on emprical creep equation for soils developed by J. K. Mitchell. The parameters obtained from the analyze are almost equal to the soil's one.

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The permeability properties of geotextiles and geotextile/soil systems were studied using gradient ratio testing apparatus improving on the type of U. S. Army Engineer Waterways Experiment Station.
It is suggested that the permittivity is better than permeability to evaluate the characteristics of geotextiles as filter materials. From the results on six geotextiles, it is confirmed that the decrease of permittivity according to the surcharge load is very slight, although the thickness decreases greatly.
It is also obtained from the results of long term permeability tests for the geotextile/soil systems, that the permeability decrease with time by clogging of geotextiles. Further, the trend is approximately straight on the log-log diagram.

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This paper is concerning with small laboratory scale reinforced embankment subjected to horizontal sinusoidal seismic loading with a shaking table. In this test, we combined various parameters; the length of the reinforcing, the number of the reinforcing layers, the slope of the face and the sort of the reinforcing materials.
The result showed that the part of the reinforcing was acted as one block and the block resisted to the earth pressure like the gravity-type retaining wall.

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Most of design methods for geotextile reinforced embankments are based on only equilibrium of moment or earth pressure in the critical state, but deformation behaviour has to be taken into account.
This paper describes model load tests on geotextile reinforced embankments filled in a small box. And the influence of the kind and length of geotextile on bearing capacity and deformation behaviour was investigated. It was found that considerable deformation occures before it reaches the critical state, and that restraint of deformation can't be estimated only by ultimate tensile strength of geotextile.

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The paper describes the bearing test of model engineering sheet with large strain gauges on soft clay ground. The destribution of strain explained the supporting mechanism of sheet or net. As the settlement curve was approximately parabolic, the bending analysis was able to bring the bending angle of sheet. In addition, the most suitable condition of sheet spreading is discussed. In textile sheet, it should be spread about 10% loosely, and another sheet or net should not be spreaded loosely.

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It is the purpose of this paper to point out that the reinforcement of retaining structure is affected by the stiffness of geotextiles. Model loading tests were carried out to investigate the bahavior of embankments reinforced by geotextiles with 4 kinds of stiffness. The results of the tests are summarized as follows: (1) judging from the load-settlement curves, higher stiffness of geotextiles is more effective for reinforcement, (2) horizontal deformation of embankments reinforced by geotextiles with lower stiffness is relatively large, and (3) earth pressure on the facing wall depends on the stiffness of geotextiles.

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Large scale experiments on the behavior and the failure mechanism of embankment reinforced with polymer grids were carried out under heavy rain condition. The observations on the strains in the polymer grids show that the maximum tensile forces were greatly smaller than the assumed one in the limit analysis method. And the erosion gradually occurred in the surface soil between polymer grids. Therefore a rational design method which can consider the change of the stress-strain patterns and an appropriate slope protection method must be developed.

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The slope of reinforced embankment is increasingly steeper now-a-days and as a result the slope treatment is growing more important than ever with the necessity of protecting its unstable condition due to erosion by rain. In the present research the authors have proposed a new type of slope-frame which is incorporated rigidly with the grid net-work assembly (15cm width) laid in the earth embankment. The effectiveness of the slope in this method is confirmed by the destruction experiments conducted on reinforced and non-reinforced embankments in the presence of an artificial heavy rain.

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Large scale experiments on the behavior and the failure mechanism of embankment reinforced with spun-bonded non-woven fabrics were carried out under heavy rain condition. Test results show that the amount of drainage water from fabrics is not so large as expected, but the seepage water gather near fabrics and it cause erosion of the surface soil near fabrics. And the fabrics restrained the deformation or the plastic strains of the reinforced earth effectively, in spite of low stiffness of them. These observations led to the conclusion that the fabrics certainly modified the failure mechanism or the stresses and strains pattern and therefore an appropriate design method based on the real mechanism of the reinforced earth structures must be established.

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The sand mat is one of the most effective drain filters and is often used for soil improvement works practically. Recently, however, it becomes in hard to get the good sand materials and thus the permeability of sand mat used at many construction sites is so small that it is impossible to apply practically for the drain filters. Therefore, the development of the artificial drain materials like as geotextiles is requested.
In this paper, the drainage effect of the new type “Band-shape Drain Material”, which is made of the PVC and nonwoven fabric, is examined by laboratory test and numerical analysis and its design method for practical application is introduced.

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In addition to use of common design formula, the authors have examined the stability of geotextile-reinforced earth retaining walls by use of slippage on curved surfaces.
Analyses concept consist of internal stability which suppose that the walls keep their balance on circular surfaces and external stability which suppose that the walls keep their balance on logarithmic spiral curved surfaces or paraboric curved surfaces of the third order.
Then distribution map of stability can be made of calculated ratios of slipping-resisting forces, which utilize to design and examine the stability of the walls.

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Deterioration in the durability of concrete structures, which is mainly caused by saline permeation, freezing and thawing actions and carbonation of concrete, has recently become a social problem, and it has been required to further improve the structural durability of concrete.
This paper describes a newly developed concreting method, “Textile Form Method”, using a special textile having high permeability of aeration effects. In this method, excess water and entrapped air are bled out of the textile form, hereby improving structural durability of concrete and producing concrete with higher density toward the surface free from air bubbles and blow holes.
The above improvement have been proved by filtering effect of geotextile and the method has been attracting the attention as a new field of concrete textiles.

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