Geosynthetic drain (GD) are intensively and successfully used as drainage materials, such as drains to accelerate the rate of consolidation of saturated clayey soils; as a liquid collection layer in landfill; as a capillary barrier; etc. Permeability (drainage capacity) of a GD is mainly influenced by the confining pressure and the material confining it. For all the products, the drainage capacity reduces with the increase of confining pressure; and the value of confined in soil is less than that confined in rigid plates or a rubber sleeve. It is suggested that a value used for design should be determined by a test closely simulating the field confining conditions. If only manufactured value is available, reduction factors considering soil clogging etc. should be applied. Some up-to-date theories for design GD as vertical drain (PVD) and horizontal drain and in leachate collection system of a landfill have been presented.

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This study aims to develop an inexpensive liquefaction countermeasure with a focus on the placement of geogrid beneath the residence. In order to attain this aim， a series of shaking table tests were carried out to explore the effect of the geogrid shape on reducing liquefaction-induced settlement. It was indicated from the results of these tests that high stiffness and length of geogrid were reducing liquefaction-induced settlement. Thereafter， discussion was made on clarification of the mechanism of reducing liquefaction-induced settlements of sand deposits reinforced by geogrid.

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The geocell reinforced base course is expected to improve supportive force and stress dispersion effect. However, its effect is still under study, and no design method has been established. For that reason, Geocells is mainly used for temporary roads. Therefore, in order to clarify the design method of the geocell reinforced base course, it is necessary to grasp the stress dispersion effect and the effect of reducing the pavement thickness. In this study, loading tests were carried out on the model ground, and the reduction of the pavement thickness was examined from the strength deformation characteristics and the stress dispersion effect of the geocell reinforced base course.

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The deformation potential of geogrid-reinforced aggregate layer was investigated through laboratory large scale model tests. The influence of the aggregate layer thickness was mainly considered together with reinforcement depth. Cyclic pressures were applied with increasing the amplitude after every 500 cycles. Under low pressure amplitude, the rate of surface deformation reached a stable stage with increasing load cycles, regardless of reinforcement condition. This rate was more progressive with load cycles under high pressure amplitude, which was more obvious in unreinforced case. Surface deformation was considerably resulted from lateral flow in thick aggregate layer, and from subgrade deformation in case of thin aggregate layer, especially for the reinforced case. The contribution of subgrade deformation was small on surface deformation in thick aggregate layer, while it was significant in thin layer. The effective reinforcement condition was achieved when geogrid was placed at the middle of layer.

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Several previous studies proposed the method of estimation for geosynthetics settlement above sinkhole. And, assumption of that methods have fixed vertical load for anchor area (They assumed fixed vertical load for anchor area). However, vertical load around sinkhole practically increase due to loosening pressure with different settlements. In this study we proposed a method of evaluating the value of geosynthetics settlement above sinkhole considering variation of vertical load on anchor area and compared it with experiment results. As a result, estimated value showed good coincidence with the experimental result.

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The confined-reinforced earth (CRE) method was introduced in subgrade layer beneath a road pavement to reduce differential settlement between bridges or culverts and their approaches that is caused by large earthquakes. This method consists of granular material, geogrid layers and confining tie rods. In this study, the effect of the thickness of a pavement, which was simulated as overburden, on the CRE under differential settlement condition was investigated. The CRE was made on a fixed plate, which was simulated an abutment of a bridge, and a moveable plate, which was considered as an embankment to simulate settlement. The overburdens of 1, 2 and 4 kPa on the CRE were performed. It was found that the surface settlement distribution of the CRE and tensile strain in the geogrids increased with increasing overburden.

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The horizontal displacement more than 15cm occurred on the facing of a 20m high reinforced soil retaining wall that was under construction for the purpose of the alignment improvement of the existing national highway located in Hyogo, Japan. In this paper, the causes of the excessive deformation, together with the numerical examination into countermeasures are in detail described. First, various site investigations and laboratory tests were carried out to manifest the current state of the reinforced soil retaining wall. Second, the deformation behavior of the wall was simulated by performing numerical analysis. Finally, an appropriate countermeasure to prevent further development of the wall deformation was proposed by predicting the stress-strain behavior of the reinforced soil retaining wall with the remedial work.

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As for the protection mat used for landfills, the nonwoven fabric which generally laminated fiber is used. A delamination in this laminating structure is reported as one of the causes of the damage of the protection mat. However, the general test method to evaluate detachment strength of the protection mat is not suggested. Therefore we examined a test method to evaluate detachment strength of the protection mat. As a result, we confirmed that we might evaluate detachment strength by the shear detachment examination that used a loop fastener and adhesive tape. The test also confirmed the relationship between fiber entanglement and detachment strength, the difference in detachment strength depending on the type of protection mat, and the difference in detachment strength due to the tensile member used for the test. We report an examination and the result that I went for to confirm detachment strength in this article.

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The effect of the shape of a damage hole on the self-healing capacity and permittivity of geotextile encased-geosynthetics clay liner (GCL) was investigated through a series of constant head leakage rate tests. Three different damage shapes, circle, rectangle and square were tested with different size. Hydraulic radius (Rh) (damage area/periphery length of a damage) has been used to analyze the effect of the shape of a damage hole. The test results indicate that the self-healing ratio (  = healed area/total damage area) was influenced by the shape of a damage. For a rectangular or a square damage under the same damage area condition,  tends to decrease with increase of Rh. In case of a circular damage, it has a larger Rh, but had a higher value of  compared with a square damage of the same area. It has been explained that for a square or a rectangular damage, at corner locations, the amount of the bentonite entered the damage hole will be reduced due to so called “corner effect”.

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At coastal areas where wave calmness cannot be secured, if revetments of coastal waste disposal sites are constructed using impermeable sheets, the sheets may not be laid in the shape as designed due to scouring of foundation stones. If large size stones are used to withstand scouring, impermeable sheets may be damaged by stone corners. In this study, the standard of protection mats, sandwiched between stone materials necessary for maintaining the impermeable sheet quality, was verified by laboratory experiment, field demonstration experiment, and FEM analysis. As a result, it was suggested that long-fiber nonwoven fabric with a basis weight of 1700g/m2 or more, placed under the impermeable sheet as a protective mat, can be used to withstand the overload up to 50 kPa.

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In the repair work for aging embankments of small earth dams, the installation of geosynthetic clay liners (GCLs) has been proposed as an alternative solution of constructing the sloping core zone. However, the design standard has not yet been established due to limited investigation on the mechanical characteristics of GCLs laid in small earth dams. In this study, direct shear tests were conducted on needle-punched GCL/mixed soil simulating embankment soil interfaces. It is revealed that extrusion of powdered bentonite from hydrated GCLs is observed on the interface between woven geotextile surface and silica sand, which does not cause the reduction of shear strength under low confining pressure.

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Diffusive permeation tests were conducted to evaluate barrier performane of PVC geomembranes against organic compounds in waste leachate. The partitioning coefficients became large when the organic compound had a low solubility and a high octanol-water partitioning coefficient. Most of their diffusion coefficients were approximately 10-13 m2/s, but 1,4-dioxane and bisphenol A had the lower diffusion coefficient than them. In particular, 1,4-dioxane could not pass through PVC geomembranes at all in testing duration of 2 weeks.

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Reynoutria Sachalinensis growing in Hokkaido is remarkable, there are problems in traffic safety such as sight disorder in road intersections and curved areas, because it is difficult to travel with small width roads and river banks maintenance and management by weeding must be carried out. For this reason, it is required to develop a method of effectively eliminating Reynoutria Sachalinensis or a method of suppressing the growth of reducing the cost. As one of countermeasures, in order to suppress the growth of Reynoutria Sachalinensis, a test construction was carried out using a net-shaped weed control sheet. As a result, although it was a short period of time, it was possible to suppress the growth of Reynoutria Sachalinensis by the mesh sheet.

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The cohesion of continuous fiber reinforced soil resulting from a box shear test conducted under a low vertical stress condition is lower than that conducted under a high vertical stress condition. Moreover, the soil reduces in strength when water is infiltrated. However, there is no research of measuring the vertical earth pressure acting in continuous fiber reinforced soil, whose purpose is to protect surfaces of slope, or the rainwater infiltration behavior of the soil. In this study, we have measured both over about one year. The measurement results show that the acting vertical earth pressure is as low as 10-20 kN/m2, and that the soil saturation increases temporarily during execution or rain but is kept stable because of the water coming out of the soil quickly and the effect of plate-equipped anchors.

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In a cold district, many slopes collapse at the beginning of spring because the frozen ground melts. As a temporary or recovery action against such a problem, slope protection work with thin gabions is frequently used and is widely recognized as an action suitable to cold districts. However, now that many years have passed since construction, lots of gabions have a large deformation or break. In this study, we have tried to develop slope stabilizing method with a combination of highly flexible geocells and steel drainpipes: the former is expected to have the good characteristics of following frost heaves and melting subsidence, while the latter can discharge water from the surface frozen slope, and to construct an experimental embankment slope to evaluate the performance of the slope stabilizing method.

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A gabion faced reinforced soil wall is developed because it is suitable for places that have a risk of water rise in an embankment, such as wetlands and catchment areas, and it can have a steep slope. Accordingly, we constructed an experimental wall in a cold and snowy environment to measure, over two seasons, the deformation behavior associated with the melting frozen ground and the water content behavior of an embankment caused by snowmelt or heavy rain. In this study, we have used the measurement results and the outcomes of heat transfer and seepage flow analyses with the former results to work on not only how to arrange permeable heat insulating materials suitable to cold and snowy environment and base drainage layers but also whether nonwoven fabric is necessary.

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A new silt fence with zeolite sheet was developed for the countermeasure against nutrient salts, radioactive cesium and heavy metal in the water. The fence has double layer of polyester sheet, which is generally used for the common silt fence, and zeolite sheet is enclosed with these layers. Its functions are filtration, separation and adsorption. A trial construction for countermeasure against eutrophication was carried out at a regulating reservoir in Shizuoka City. Field measurements and analyses of water quality and adsorption amount of nutrient salts for zeolite sheet were performed. The workability of the fence, adsorption of nitrogen for zeolite sheet, and filtration and separation of the fence were confirmed. In another trial, the durability for 12 months of the zeolite sheet in the fence was also verified.

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In this study, in order to investigate dynamic behavior of a newly developed absorbing system by means of Geocell filled with one-size aggregate, 3D-FE impact response analysis of the Geocell walls was carried out taking impact velocity of the weight as variable. The applicability of the proposed method was investigated comparing with the experimental results. From this study, the following results were obtained: (1) the time histories of the impact force, penetration of the weight and transmitted impact stress obtained from FE analysis were almost similar to those of the experimental results; and (2) the envelope of transmitted impact stress and the deformation of Geocell wall can be appropriately simulated by means of the proposed numerical analysis method.

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In this paper, case study is in detail described, regarding a geosynthetic reinforced wall (GRW) with high embankment behind was constructed over a deep valley. The descriptions deal with a flow of planning, site investigation, design and the construction of the GRW, together with engineering countermeasures in cope with the 20m high, which is beyond the scope of the current design and construction manual for the GRW. The details of geotechnical surveys, soil properties by laboratory tests, design of the GRW as well as the embankment, the observational construction with the FE analysis are well documented. Some useful countermeasures are proposed when the construction of GRW is obliged to conflict the current design/construction manual for GRW.

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In order to keep the seismic stability and durability of sheet pile quay walls economically, the method using geocell was proposed in the present study. Geocell layers consisting of geosynthetic material and gravel are located on the upper parts of existing ties, and fixed to the sheet pile wall. A series of shaking table tests of the sheet pile quay walls were conducted on 1G filed to evaluate the effects of the proposed method. The shaking table tests revealed that the arrangement direction of the geocell influenced the seismic stability of sheet pile quay walls. The seismic stability of the quay wall using the geocell layers with the more stable arrangement direction almost equaled to that of the conventional quay wall with vertical anchor plates, independent of the density of backfill.

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A slope stability analysis method has a long history and various stability method have been proposed since the Fellenius method proposed in the 1930s. In practice, a circular slip surface has been generally used to calculate a safety factor, however, for evaluating the stability of reinforced slopes that have complex strata with weak layers, the safety factors obtained by using this method are not always the minimum values. In this study, a calculation method of the safety factor with a noncircular slip surface in unreinforced and reinforced slopes is proposed using a limit equilibrium of Spencer's method. To validate the proposed method, the calculated safety factor by the proposed method compares with the previously presented results.

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Kyushu Shinkansen (Nishi-Kyushu route) is the route of about 66km between Takeo-Onsen and Nagasaki stations, which is currently under construction. The Genshu Viaduct Bridge in Nishi-Kyushu route is GRS integral bridge with PC girder to be located in the valley of about 70m a short tunnel are continuous in Isahaya city (Takeo-Onsen station origin 47k263m). GRS integral bridge had been built with RC girder and SRC girder so far, but this is the first time GRS integral bridge is built with PC girder. In this paper, we report on the design and construction of the GRS integral bridge with PC girder will be the first case while thinking into account past achievement of GRS integral bridge buildings.

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In recent years, it has been reported that the surface-wave method is useful as an efficient way to evaluate the current condition of a reinforced soil wall. In this study, we have applied the surface-wave method to five reinforced soil walls, having different degrees of deformation, in the Okhotsk area of Hokkaido to investigate the relationship between the distribution of VS and the slope angle of wall panels. The results show that as long as the slope angle is large, VS reduces locally rather than increasing proportionally to the depth. Accordingly, we find that the use of VS has the possibility of evaluating the degree of damage to reinforced soil walls.

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The river embankment failure due to overtopping of river water is mostly generated by the back slope erosion of the embankment. By using air permeable-waterproof sheet in the condition of overtopping water, we experimented its erosion resistance on the back slope and the boundary with drains set at the bottom of the back slope which is claimed to be a weak point in terms of erosion. As a result, we could find effectiveness of air permeable-waterproof sheet against back slope erosion of the river embankment due to overtopping water.

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The authors have recently proposed an aseismic reinforcement at the toe of embankment using sandbag-structure which in turn enables one to save the construction cost, to work easily and to reuse the embankment materials. In this paper, the results of static loading test as well as the shaking table test by using a stacking soil-bag are presented. The results of static loading test on the sandbag-laminate showed that the creep of the stacking soil-bag on loading could be greatly eliminated by applying a preloading-prestress cylce. Regarding the shaking table test, the stacking soil-bag structure exhibited almost no deformation as long as the structure is subjected to the prescribed prestress, even when it undertook the lateral load equivalent to the dynamic earth pressure. Based on these experimental results, it was confirmed that the stacking soil-bag structure at the toe of embankment could be a useful countermeasure against the earthquake attacks.

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Although fiber mixed reinforced soil used for reinforced soil method can enhance mechanical property by mixing into base materials, it is mainly used for sandy soil and there are not many study examples that it is mixed into cohesive soil. The previous study showed that the reinforcing effects by short fiber (SF) appear notably by compacting cohesive soil, which is parent material, at wopt. But those focused on the property of SF exist very a few. Aiming at understanding the effects that the property of SF which is mixed into SF mixed reinforced soil (aperture and rigidity) has on intensity deformation property, this study conducted a uniaxial compression test against SF mixed reinforced soil using 3 types of SF with different aperture and rigidity and examined the results.

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Urayasu City had a big damage due to the great Eastern Japan Earthquake in 2011. In the survey results after earthquake, the particle size distribution of the sand boil contained a lot of silt. Therefore, this research is focused on the effect of fine fraction contents on the liquefaction suppression behavior of short fibers mixed stabilized soil. This study carried out unconfined compression test and undrained cyclic shear test of decomposed granite soil with different fine fraction contents mixed a short fiber and cement. As a result, it was cleared that short fiber mixed stabilized soil containing fine particle fraction has an effect of improving liquefaction strength.

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The short fiber mixing reinforced soil method is a method of improving the mechanical properties of the ground by mixing short fibers into soil. Various things have been elucidated, such as the existence of the optimum value of the mixing ratio of the short fibers to the strength from the research which has been carried out so far. However, the reinforcement mechanism by mixing short fibers is not so clear. Also, the relationship between the mixing ratio and the reinforcing effect is often not clear in the setting conditions of the density of the test specimen. In this study, two kinds of test specimen preparation conditions were set, and then we carried out the triaxial compression tests using short fibers with different diameters in which mixing ratio were varied. From the result, the strength and deformation characteristics differed for each specimen preparation condition, and we considered about the reason.

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The authors have recently proposed aseismic countermeasure for embankment currently in service, in which the toe is reinforced by using a soil-bag structure. Moreover, the performance was examined in a largescale shaking table test using a model embankment with 4m high. As a result, the soil-bag structure was found effective in terms of reducing the response acceleration in the embankment to some extent. However, it was also found that the structure was not robust enough by exhibiting shear deformation during shaking. Accordingly, it is now needed to increase the overall stiffness by increasing the shear resistance of the soilbag structure. A series of direct box shear test was, hence, carried out in order to manifest the characteristics of not only the geotextile-to-geotextile friction but also the soil-bag to soil-bag friction.

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