With the recent emphasis on infrastructure development, geosynthetics in India have received a tremendous boost. Apart from the consistent use in pavements of the east-west and north-south corridors and golden quadrilateral of the NHDP projects being executed by the NHAI, reinforced soil walls in urban flyover approaches have become common, due to their distinct advantages over conventional reinforced concrete walls. These apart, the use of high strength geotextiles and geocell mattresses for foundation of high embankments on soft soils has also proven to be feasible even in black cotton soil areas. Increasing emphasis is being given to the development and use of natural fibre (particularly, jute and coir) geotextiles for civil engineering applications. The paper traces many of these developments and summarizes the key issues to be taken note of for utilizing the vast potential geosynthetics offer, in India’s march to development.

View full abstract

This paper presents about the current situation of technology and market regarding geosynthetics in Vietnam. As Vietnam has a relatively complicated territory: Countless mountains, numerous rivers, long and meandering coastline. In additional, its rapid development of economy in recent years has challenged the relatively poor infrastructure system as well as experts, engineers in these fields. To meet this challenges, new technologies and materials have been applied in numerous constructions and geosynthetics is one of the most important structures. However, after decades of arrival, geosynthetics still remains a highly difficult technology for Vietnamese engineers. This paper will analyze some main factors of technology and culture that make difficulties for geosynthetics to widely apply and use in this country. It also mentions some recent big projects and key institutions, companies that relate to this technologies to picture the market of Vietnam.

View full abstract

A comparison of strength characteristics of two types of geotextile subjected to pullout force was made by means of in-situ pullout test. It was well demonstrated that the pullout strength property consisted of two components; i.e., the frictional resistance between soil and geotextile, together with in-soil interlocking effect of geotextile. Moreover, an integral type at the lattice nodal point exhibited larger interlocking effect than an bonded type. Based on the test results, it is strongly suggested to employ an integral type of geotextile in well-compacted fill material so that the pullout deformation of geotextile may well be restrained due to the interlocking effect.

View full abstract

For the last two decades, geosynthetic-reinforced soil retaining walls (GRS RWs) have been constructed for important facilities such as railways and highways. In order to achieve greater seismic performance, a new-type of geocell which have three dimensional structures, having straight longitudinal members with transversal members has been developed. In this paper, in order to investigate the seismic stability of the new-type of geocell reinforced retaining, a series of shaking table model tests was carried out by using the new-type geocell and geogrids as tensile-reinforcement in the sandy and gravelly backfills. Furthermore, an unreinforced retaining wall (T-shape) model was also tested for comparison. It was found that new-type geocell reinforced soil retaining wall model exhibited higher seismic performance than both geogrid reinforced soil retaining wall model and unreinforced retaining wall model.

View full abstract

Large earthquakes often lead to large differential settlement between bridges and their approaches. In some of these cases, emergency vehicles cannot pass the unevenness after earthquakes. In order to mitigate this problem, confinedreinforced earth (CRE) method was introduced in subgrade layer, at the bottom of pavement layer of road structures. Some laboratory prototype scale model test with various prestress in geogrid layers were carried out to investigate the effects of prestress on deformation of confined-reinforced layer due to differential settlement. The levels of prestress is applied via prestrain set as 0%, 0.016%, 0.05% and 0.1% in elongation. The results show that the prestress in geogrid plays an important role in reduction of differential settlement between bridges and their approaches.

View full abstract

Load settlement behavior, bearing capacity improvement and surface deformation characteristics of geogrid reinforced soil were investigated through experimental study. Rigid circular steel plate was used as a model footing. In model experiments, it included one unreinforced test and four reinforced tests; one with triangular geogrid and three with biaxial geogrids. Test results show that triangular geogrid reinforcement outperforms biaxial geogrids of almost same unit weight. For biaxial geogrids, larger bearing capacity improvement was noticed with geogrid of higher tensile strength. Uniform surface deformation was observed with no reinforcement and triangular geogrid reinforcement, while higher non uniformity was observed with stiffer biaxial geogrid reinforcements.

View full abstract

A large quantity of sediments was generated by the tsunami flood in the 2011 Off the Pacific Coast of Tohoku Earthquake. For recycling the above tsunami sediments, an up-cycle block mixed the sediments with cements and shaped in the rectangular parallelepiped solid was proposed and its engineering quality has been proved. Then, the application of the up-cycle block to the civil engineering structures etc. has been required to be discussed from the engineering view point. In this study, the practical method to apply the up-cycle block to the earth bank body as one kind of earth bank materials was discussed on the tsunami resistant performance of the combined up-cycle blocks with the geosynthetics effectively. The above performance was evaluated experimentally depending on the overflow tests for the earth bank models in which the up-cycle block models were set. As the results, the application of the combined up-cycle blocks in the earth bank against the tsunami flood and the effectiveness of the geosynthetics to combine the up-cycle blocks could be clarified.

View full abstract

During the 2011 off the Pacific coast of Tohoku Earthquake, at many places, coastal dykes fully collapsed by deep over-flowing tsunami current. A great number of residential houses and infrastructures were washed away. It has been required to develop cost-effective anti-tsunami coastal dykes. A series of experiments of hydraulic constant flow on 100 mm-high dyke models were conducted to evaluate the resistance of sandy embankment against hydraulic overtopping with changing cover materials, slope angle and the width of the embankment. Effect of using geosynthetic-reinforcing material was also examined. It was clarified that the resistance of a dyke against overtopping tsunami is improved by covered with both gravel and panels. The effect of using geosynthetic-reinforcement required more research for clarifying.

View full abstract

GRS integral bridge is composed of a pair of abutments (full-height rigid facing) integrated with geosynthetic reinforced backfill and a girder integrated to those abutments. Because of that structure, the abutments support continuously tsunami load acting on both of the girder and abutments, unless the girder is not flowed away. In this study, laboratory tests were conducted supposing that GRS integral bridge affected by the tsunami. In the tests, horizontal force was loaded from orthogonal direction against bridge axis statically on the model abutment. From the tests results, improvement of resistance to lateral force can be expected comparing with the case of un-reinforced backfill, because the friction between the abutment and backfill is increased or kept by introducing the geosynthetics. And, the relation between the external loaded force and the measured force on the back of abutment was tried to estimate and calculate, based on the test results.

View full abstract

We have recently developed a GRS levee as a cost-effective flood barrier having a relatively small cross section with high resistance against overflow erosion. For further improvement of the performance of the GRS levee, we performed a series of model experiments to evaluate the overflow and infiltration of GRS levees constructed by using various fill material having different fines contents and geogrids having different apertures. The results of the model tests revealed that: 1) inclusion of a larger amount of fines content in the fill materials increased significantly the resistance against overflow erosion; 2) the GRS levee using a geo-grid with a smaller aperture had higher resistance against overflow erosion; 3) the infiltration discharge of the GRS levee was smaller than that of the levee with no reinforcement due to reduced infiltration erosion in the GRS levee.

View full abstract

The tsunami caused by the 2011 earthquake off the Pacific coast of Tohoku inflicted a huge damage on the tide wall of the coastal areas of Tohoku region, due to the large scale scouring of the bottom side of landward gradient slope. In order to prevent the damage of the tide wall by tsunami, it is necessary to protect its foundation by preventing the scouring of the foundation of landward gradient slope. In an attempt to examine the preventive effect of the geocell reinforcement against the scouring of the foundation of landward gradient slope of tide wall, in this research, we conducted an experiment using an open channel recirculating water tank and a model ground. As a result, we found out that it is possible to prevent the scouring and the collapse of the tide wall by the geocell reinforcement.

View full abstract

When using a lightweight geomaterial mixed with EPS beads as subgrade soil, the structure of the subgrade is two-layer structure. The elastic modulus of the subgrade is necessary for a structure design of pavement by multilayer elasticity method. But the subgrade elastic modulus of two-layer structure is not clearly. Because the elastic modulus of the subgrade is depended on the stress level. In this study, using LWGME, we were investigated the effect of wet density on the subgrade modulus in the case of a two-layer structure.

View full abstract

The contribution of fiber reinforcement to shear moduli and shear strength of granular material has been widely investigated by geotechnical engineering. A modelling approach for evaluating the constitutive behavior of fiber reinforced granular material has been required for predicting the deformability of fiber reinforced ground. In this study, the deformation property of fibrous material in fiber reinforced granular material is investigated for the purpose of fabricating a new constitutive model based on rule of mixture. Furthermore, the relevance of deformation property between fibrous material and granular material is considered from test results. The deformation property of fibrous material represents a tensile behavior on initial deformation, and finally pull-out behavior is observed. It is also considered that the deformation of fiber is progressed with equal to strain energy increment of granular material.

View full abstract

Continuous fiber reinforced soil is fiber reinforced soil having the function of serving as a vegetation growth base. This study attempted to evaluate the performance of continuous fiber reinforced soil to which a solidifying agent is mixed for the purpose of improving stability. It was found that the addition of 1-2 percent of the low-alkali solidifying agent resulted in an increase in shear strength, in particular under low confining pressure, as well as in a lower decrease in shear strength under submerged conditions. It was also confirmed that there were no practical problems regarding the greening performance and the durability to freeze-thaw or dry-wet cycles. These findings demonstrate the usefulness of continuous fiber reinforced soil mixed with low-alkali solidifying agent.

View full abstract

This study is focused on the improvement of shear strength of soils and development of soils toughness by mixing short fibers. Also, the authors studied to suggest as one of the new liquefaction suppression technique. As a result, liquefaction resistance increased with mixing short fibers due to development of apparent cohesion. However these increasing of liquefaction resistance were quite limited. Therefore, this study is focused on different length of short fibers in order to improve the effect of liquefaction suppression. As a result, it was revealed from the unconfined compression test results and bending test results that the strength deformation characteristics of soil which mixed short fiber can be improved from brittle failure to ductile failure and these effects of improvement depend on the length of fiber. Also it was revealed from the cyclic shear test that the liquefaction strength increased with mixing short fibers.

View full abstract

In Japan, innovations leading to lower maintenance and repair costs for asphalt pavement structures are required. For a general roadway in Japan, it is only possible to apply a soil reinforcing technology that is equivalent to excavating and backfilling concerned with maintenance of lifeline facilities. In this study, therefore, model loading tests on asphalt pavement with fiber-reinforced recycled concrete aggregate layer were performed to develop a new soil reinforcing technique that can be applied to ordinary road. As the results of the present study, it was confirmed that mixing short fiber in the subbase layer made of crushed concrete aggregate has advantage to reducing the residual settlement caused by heavy traffic load.

View full abstract

Two kinds of functional papers are newly developed to adsorb nitrogen and phosphorous in the water. Zeolite functional paper (Z500-paper) adsorb NH4-N and PAdeCS® (Phosphorus Adsorbent derived from Concrete Sludge) functional paper (P260-paper) adsorb PO4-P. A series of adsorption tests were carried out for the solution of NH4-N and PO4-P. Main conclusions are as follows. P260-paper adsorbs PO4-P in very short time. The adsorption capacity of Z500-paper for NH4-N decreases by the combined use of P260-paper. When P260-paper is used, pH of the solution raises from 7 to 11–12. When applying at water purification work, it is effective to use independently in order of Z500-paper and P260-paper, respectively, and then to carry out a neutralization process.

View full abstract

This study aims to investigate the effect of reinforcement exerted by soft plastics contained in landfills, which especially focuses on the continuous or discontinuous-placed state of soft plastic, to the slope stability of landfills. Two conditions of landfills were simulated in a large box. The one case was “continuous model” in which the soft plastics were mixed and placed continuously in the entire sample, and the other case was “discontinuous model” in which the soft plastics were placed discontinuously with an interception layer formed with decomposed granite soil in the center of the samples. The results obtained from the comparative tests showed that the distribution of lateral pressure on the wall of both cases was quite different. In addition, the deformation of the continuous model maintained self-standing and stable condition, while that of the discontinuous model did not converge in accordance with the lateral stress released during the movement of the sidewall. It is believed that the horizontal tensile stress generated on a soft plastic will be transmitted to other soft plastics as long as the soft plastics were continuously mixed and placed in the entire landfill, and that a large reinforcing effect will be exerted in the entire landfill as a result.

View full abstract

In renovation work for the purpose of improving water shielding properties of an aging embankment of irrigation pond, a method for installing a bentonite geosynthetic clay liner may be adopted. In this case, it is important to have a precise understanding of the frictional interaction properties between geosynthetic clay liner and soil in the embankment for the investigation of stability of the embankment against earthquakes and heavy rainfall after renovation. For this reason, in this study, direct box shear test apparatus was used to fully examine the frictional interaction properties between the bentonite geosynthetic clay liner and the soil used in the pond embankment under low stress, the deformation characteristics of bentonite within the liner, etc.

View full abstract

Liner sheets are welded together by welding machine for the construction of landfill liners. After welding, the seam between the sheets are carefully inspected for the detection of faulty welds. There are various inspection methods such as Visual Inspection(VI), Air Pressure Testing (APT) and Vacuum Box Testing (VBT). VI has possibility of overlooking, APT can only be applied to seams joined by double fusion welding, is easy and effective, but does not indicate the exact location of the fault. VBT is time-consuming if all the seams are to be inspected. The thermo-graph inspection (TGI) has developed as a new method of non-destructive test, which is viable and can complement the demerits of existing methods. TGI measures the temperature of the sheet surface when they are welded. To evaluate quality of the seam, this method uses threshold temperature, which is obtained by welding experiments and strength tests of the seam samples, to judge whether the seam is correctly welded. However, it requires hundreds times of experiments to obtain the value. The problems is that if the material of the sheet changes, time-consuming experiment is always needed. To solve this issue, a heat transfer model of geomembrane seam welding is attempted to develop to derive the threshold temperatures for the faulty welds detection which can be applied to various kinds of materials. To verify the model accuracy, measurement of the vertical distribution of the temperature of the seam was conducted. The temperature at jointed part and at the surface were obtained by the thermos-couples while the sheets were welded by self-propelled heat-welding machine. The model values correspond reasonably well with the experimental data on various conditions.

View full abstract

The U-shaped ditch installed on a cut slope in a cold district can be damaged by the phenomenon of frost heaving. The authors have developed a berm ditch highly resistant to frost heaving by combining very strong and highly flexible geosynthetic drainage material and recycled aggregate. This study attempted, with an aim of improving workability, to fabricate a berm ditch using drainage material alone. In addition, the permeability was improved to the same level as the conventional U-shaped ditch by changing the cross-sectional shape. All berm ditches made under this study demonstrated that the heaving caused by the adfreezing and frost heaving phenomenon could be prevented.

View full abstract

Experimental geotextile reinforced soil walls in which a steel frame or geocell is used as facing panel were constructed and the deformation behavior associated with freezing and thawing was observed for three seasons. As a result, it was found that front displacement was larger when using high frost susceptible soil than when using no frost susceptible soil. However, little is known about the extent of the load exerted by freezing and thawing on the geogrid combined with the facing panel in the soil. For this reason, in this study, a geogrid attached with strain gauge was used to construct a reinforced soil wall in an outdoor and indoor soil vessels in order to observe the behavior of the geogrid under freezing and thawing conditions.

View full abstract

Hachinohe area which is located in the north east has a climate of low temperature and less rainfall during the winter period. On the other hand, in the Hachinohe area, volcanic cohesive soil was depositing widely and thick called the Takadate loam. That is region specific soil and sensitive soil on the frost heaving action. There are many cases that are not construction aggressive frost heave measures method in Cut slope, In recent years these problems often occur and has become a regional problem of maintains. In this study, we examined the seven countermeasures method, which was carried out in situ test. And from test recording to calculate the thermal conductivity of the soil, and induces the thickness of the heat insulating layer by analysis to verify the integrity of in-situ test results. As a result, As a result, we were able to confirm the method of calculating the insulation thickness and the possibility of measures method that does not use a heat-insulating material.

View full abstract

Geotextile-confined soil wall is a stable retaining structure which is layered a confined soil layers by using geotextile. Since the structure of the wall does not require a friction resistances of geotextile and soil, the width of the wall becomes slender than that of the geotextile reinforced soil wall. Although many of the walls constructed in the past have not damaged by an earthquake, the seismic behavior of the wall is not clarified. Authors carried out the shaking table test to evaluate the seismic performance of the wall. The characteristics of the wall obtained from this test are as follows; 1) the wall behaves integrally and the overturning mode becomes conspicuous at the failure, 2) the stability of the wall can be evaluated from stability analysis of the seismic coefficient method.

View full abstract

The permeable pavement may mix Roadbed materials to subgrade soil in a subgrade when it becomes the soft ground. As these measures，become able to maintain a design thickness and restraint of the drop of the support power of the pavement by laying a geotextiles (the following nonwoven fabric) nonwoven fabric between roadbed and a roadbed. But, do not reach it before it is established method to evaluate the durability performance of the nonwoven fabric which it laid under pavement. I examined it of the nonwoven fabric after having laid it with pavement.

View full abstract

In this study, a series of shaking table model tests was carried out to investigate into the resistant mechanism of the proposed reinorcement methodology, which combines inclined soil reinorcement with failure prevention net. It is found from the model tests that the failure prevention net could work to restrict dropping of the wall facing block, and to propagate the pull out resistance mobilized by the soil reinorcement. In additions to the above, especially when the wall displacement become relatively large, mobilization of the resistance thanks to the flexural rigidity of the soil reinorcement was also indicated as well as the pullout resistance. As a result of the above reinorcement mechanism, proposed method could effectively improve seismic perormance of the masonry wall.

View full abstract