The reinforcement and separation are important functions for geotextiles used in road construction on the soft ground. In this paper, we experimentally investigated concentrating on the separation function, and had a try to represent the function quantitatively. The cyclic loads were employed to the test specimens, the settlement, pore pressure and the mixing between the subbase layer and the subgrade soil were measured. The needle-punched non woven had a enough strength and showed an excellent effect on the separation. As the result of considering the relationship between the separation and reinforcement function of geotextiles, it is obtained that the separation was principal function in road construction on soft ground.

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Geotextiles have been rarely used for paved roads on soft ground in Japan. Because there are a few reports which confirmed the efect of placement of geotextile within base layer.
A test road having the reiforced subbase with geotextile was constructed for repetitive loading by heavy truck on soft ground. The test road was constructed 64m (8m×8 section) in length, 5m in width. This report describes the estimation of durability of pavement structure at each repetitive number of loading by measuring a rut depth and dynamic elastic deformation at the surface of the pavement.

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The bearing capacity of foundation ground with one layer geogrid is studied on the basis of both laboratory loading tests and theoretical consideration. The test results show that there exists an optimum installed depth of geogrid which a maximum reinforcing effect is mobilized. The depth is about the same value as the width of strip footing, and is independent of the geogrid width and the ground density. A bearing capacity equation is formulated using limit equilibrium method and the validity is examined from the direct comparison between the calculated results and the loading test results.

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A large number of waste containers have been constructed every where in Japan, for increasing wastes by the developmennts of industry and diversity of human lives.
this paper summarized desings and field work methods of geomembranes based on investigations about actua performance of today's waste containersin Japan, and discussed technical problems of geomembranes on the waste containers.

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Many studies have been made on leakage detection of waste disposal lined with geomembrane. But, there is no method to locate a leak point reliably.
We developed a leak point location system, based on 2 electrical techniques, phase detection and to make anisotropic electric conductivity of ground.
The purposes of this paper are: (i) to describe an outline of the system; (ii) to introduce 2 electrical approaches, phase detection technique and to make anisotropic electric conductivity of ground; (iii) to show some experimental results.

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The purpose of this study is to establish the design methods of constructing retaining walls at low cost in the field of agricultural civil engineering.
Friction resistance values in the earth for the design of retaining walls were obtained from the friction resistance test of geotextiles in the field.
The four kinds of retaining walls reinforced with geotextiles, which were spunbonded nonwoven fabric horizontal laying, spunbonded nonwoven fabric or geo-grid wrapping and continuous thread-reinforced soil, were constructed to observe settlement, deformation, soil moisture and underground water level. Each of these walls was 5 meters in height, 8 meters in width.
The results of the observations showed that the stability of the steep slope (60 degrees) retaining walls below 5 meters in height and about 60 degrees constructed by wrapping method at 1 meter interval in height or continuous thread-reinforced soil method of the width of 1.5 meters, was obtained under the condition of enough drainage.

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The authors carried out a large scale of test embankment where a vertical retaining wall of concrete blocks was used and the backfill was reinforced with geogrid. The height of retaining wall is 5m. This paper reports the results of monitoring the lateral displacements of the retaining wall, strains produced on the geogrid, and so on.
Without any trouble, 40 days have passed since the embankment was completed. At the present stage, the lateral displacement of retaining wall measured is about 10cm (including the displacement during construction) at the very outside and the strain on geogrid is about 1%. These results show that our construction method proposed can be successfully applied to actual structures.

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A full scale embankment (height 6.25m, front slope 1:0.2, fill material: dry sand) is constructed by reinforcing with geogrids and these are successively disconnected by passing electricity through the nichrome wire which are intertwined in advance. With the decrease of the number of reinforcing grids the embankment gradually loses the stability and finally collapses when all the grids are disconnected.
In the present research the fracture behaviors of the embankment are observed at every stage of grid-disconnection and the analysis on fracture phenomenon is conducted by the conventional limit equilibrium method. It was learnt that the effects of the pseudo retaining wall (width 70cm) formed by the pile of sandbags sandwiched by geogrids on the front slope is required to be taken into consideration in the stability analysis of the embankment. In that the collapse-phenomenon of the embankment without reinforcement is fully explained and understood as a result of the study.

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As to an embankment reinforced with extensible materials like geogrids, reinforcement effect appears with deformation occurring in the embankment. In order to evaluate the actual stability of reinforced embankments, it is necessary to take account of the embankment deformation, In this paper, the influence of slope gradient and reinforcement length on the failure mode and the failure height of embankments on hard ground was investigated by centrifuge model tests. As a result, in case that the slope gradient is steep, slip surface approximately becomes plane. Also, it was found that the embankment deformation increasing with the gravitational acceleration could be expressed by a method with consideration for deformation.

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From the studies on retaining walls made of sand reinforced by continuous fibers, the stability of the overall structure seemed to be affected by the deformation of the reinforced sand itself. To reduce the deformation of the wall, the use of geogrid together with the fiber-reinforced sand wall was suggested. Pull-out tests on geogrid in sand reinforced by continuous fibers were carried out as the first step of the study. It was found that both the cohesion component and the frictional resistance of the geogrid in the reinforced sand were higher than those in non-reinforced sand. Therefore, the reinforcement by the continuous fibers seems to be effective for the pull-out resistance of geogrid in sand.

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Sand mixed with continuous yarn gains higher shear resistance and more stability. An attempt has been made to further improve its properties by adding a small amount of cement to the sand mixed with yarn. Our laboratory study indicates that the compressive strength of cement-treated yarn-reinforced sand is 2 to 3 times as great as that of the sand mixed with the same small amount of cement, being much higher than that of the sand reinforced with yarn alone. When the cement content is less than 6%, the permeability of the sand mixed with yarn and cement showed no reduction, suggesting no harmful effect on grass growing on the surface of the improved soil. Similar satisfactory results were obtained of Kanto loam mixed with yarn and cement or lime.

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As the history of geotextiles is rather short, estimation of the durability of geotextiles has yet been not clear. We tested spunbonded nonwovens on their durability to weathering and chemicals by acceleration method. The results of weathering tests show that when spunbonded nonwovens are exposed for long term, they must be coverd properly. And the results of chemical tests show that spunbonded nonwovens can be used for long term in the normal soil conditions (pH 5-9).

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The method of evaluation of the in-soil deformation behavior of geogrid is discussed based on the simplified assumptions concerning frictional properties between geogrid and soil and pull-out force vs. strain relationship of geogrid. By solving differential equation on the elongation of geogrid in the soil derived from the assumptions, displacement of geogrid in the soil, the distribution of shear stresses and tensile forces acting any part of reinforced soil can be obtained, and the pull-out force vs. pull-out displacement can also be calculated. The comparison of the calculated and measured pull-out force vs. displacement relationship shows fairly well coincidence.
Proposed method has a special feature that we can estimate the displacement of geogrid in any part of the reinforced soil as well as the pull-out force vs. pull-out displacement relationship by using the result of direct shear test only.

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