In the bagging and dewatering process, dredged soil and other slurry with high water content are bagged and dewatered using permeable geotextile and stacked to make banks. This process proven to be effective in preventing the spread of dioxin, PCB, and other substances as long as turbid water does not escape from the slurry-filled geotextile tubing as these substances are adsorbed by soil grains. However, the small fraction of turbid water that invariably escapes from the geotextile tubing when it is filled with slurry is termed the initial turbidity. Given that bagging and dewatering involved filling geotextile bags with slurry using a pump, we developed a method that minimizes the dispersal of contaminated soil.

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This paper proposes a practical method for estimating elastic modulus E by using Portable Falling Wight Deflection (P-FWD) test and proposes a new pavement material using geotextile. The monitored result of P-FWD test is simulated well by dynamic finite element analysis assuming elastic behavior of ground. Elastic modulus E is back-calculated so that those minimize the difference between time history of measured and calculated displacements. The proposed pavement consists of bag made by textile and lightweight cellular cement. Test construction is carried out to evaluate a performance of the pavement. The pavement placed on soft ground has high stiffness compared with improved subgrade.

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In this paper, we discuss the new construction method to use geo-cell together with a variable slope gutter. We connect the geo-cells with the variable gutter, which is one of the precast concrete product, by special metal fittings to expect the improvement of resistance for soil pressures. By using the method, we can anticipate many advantages for natural environments and construction than other conventional methods. To establish and popularize the proposed method, we perform centrifugal model tests for the optimum arrangement of geo-cell and tensile tests for joint strength of the gutter and the geo-cell. We show these test results and report the construction examples of the proposed method.

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Recently, soil slopes reinforced by geo-cell, which is one of the three-dimensional geo-synthetics materials, has been gradually constructed in Japan. If we can use the local surplus soils as the materials into the cells, the geo-cell reinforced retaining wall is very useful and have many advantages for natural environments and construction costs. In this study, we constructed two test embankments reinforced by the geo-cell and measured displacements of them for 600 days. Moreover, we investigated the condition of geo-cell reinforced soil retaining walls actually constructed in the area of very heavy snowfall after the snow thaws. Our main purpose is examination of the possibility of valid utilization of local surplus soils as inside materials of geo-cells.

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In the geo-cell reinforced soil structures, we can use the various materials as the material into the geo-cells. Mechanical properties of geo-cell reinforced soils change by the kind of filling materials. Therefore, if we want to predict the deformation and strength of them, it is necessary to grasp the relation between the characteristics of the filling materials and the mechanical properties of the geo-cell reinforced soil structures. In this study, at first, we perform the tri-axial compression tests to examine the mechanical properties of the sandy filling materials. In addition, fundamental experiments on the compressibility and the frictional property for the cell structures are performed. Finally, we analyze the relationship between results of these experiments.

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In this study, we are planning to perform tests in order to confirm basic characteristics (bending and compression properties) of textile tubes (jackets) filled with a variety of lightweight soil. In the 20^th Geosynthetics symposium, we reported the test results of the jackets filled with foam cement. Bending and compression strengths of them were small, and no reinforcing effect using textile strength was obtained. But composite light weight soil filled jacket with an outer layer of Portland cement and inner filling cement foam made an effective use of jacket tension. In this report, we performed tests of jackets filled with foam waste glass and Kanto roam, or silica sand.

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The Palace seat industrial method is a soft subsoil reinforcement industrial method with which the reinforcement frame is formed by injecting mortar into a lattice jacket that integrated with the engineering works seat.
This time, the proof experiment that constructed the temporary road of materials vehicular on the rice field using palace sheet was done. 120kN in weight heavy equipment ran with stability on the road that had been constructed on the soft subsoil using palace sheet.
It was able to be proven to be able to use the rice field as a temporary road of urgent disaster if it constructed it by this method.

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A method of improving soft clayey deposit by combining Cap-drain (CPVD) with vacuum pressure is described. The method uses a surface or subsurface soil layer as a sealing layer and no need to place an air-tightening sheet on the ground surface. It is explained that the method has advantages for situations of (a) a higher air/water permeability layer existed on ground surface, and (b) combing vacuum pressure with embankment load. A case history of consolidating a reclaimed clayey deposit by combining CPVD and vacuum pressure is analyzed and discussed. The site was in an under-consolidation state before starting the project. It is shown that the method is effective for this site. The back-calculation shows that for this under-consolidation deposit, vacuum pressure caused almost plane strain type isotropic deformation at near the ground surface.

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Kumamoto rail yard of Kyushu Sinkansen is planned to be constructed on soft clay layer, so consolidation-promotion method is necessary. Pre-load method is often used as consolidation-promotion method, but applying of vacuum-induced consolidation method is planed for reducing deformation of neighboring structures. Therefore, in this area, two types of experimental embankments with Pre-load method and vacuum-induced method were constructed. In this paper, we evaluated effect and influence of these methods, and examined consolidation-promotion method on constructing rail-yard embankment.

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When the drainage purification center was constructed on the weak humus ground of N=0 where groundwater is near to the surface, the influence on railway embankment caused by a ground reinforcement under the facilities was worried. The vacuum consolidation method was used because its influence was comparatively small. Railway embankment has been observing displacement. In this thesis, the feedback analysis of FEM was carried out based on the observation result of the vacuum consolidation method, and the effect of the vacuum consolidation method.

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Kumamoto rail yard of Kyushu Sinkansen is planned to be constructed on soft clay layer, so consolidation promotion method is necessary. Pre-load method is often used as consolidation-promotion method, but applying of vacuum-induced consolidation method is planed for reducing deformation of neighboring structures. Therefore, in this area, experimental embankment with vacuum-induced method was constructed, and effect and influence of this method was evaluated. In this paper, we evaluated modeling of vacuum-induced method by analyzing construction of this experimental embankment, and deformation of neighboring structures caused by vacuum-induced method on constructing rail-yard embankment.

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To evaluate a stability and presence or absence of abnormality of geogrid reinforced soil wall during construction or after construction, field observation which measures a strain of geogrid is carried out. Although a strain gauge has been generally used for strain measurement, it lacks durability, continuity of measuring point and ease of wiring. We develop an “optical fiber sensor geogrid” which optical fiber is inserted in geogrid as new method for strain measurement. This paper reports that it can evaluate a stability of the actual geogrid reinforced soil wall based on strain measurement by using the optical fiber sensor geogrid during construction and after construction.

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In order to predict distribution of vertical stress increment due to pulling-out of reinforcement, the cavity expansion theory was applied to the pull-out test results. First, the approach for applying the elastic solution of the cavity expansion theory which can evaluate stress state when the internal stress of a thick-walled cylinder increases was shown. And the result of the pull-out test was extended and distribution of vertical stress in a reinforced soil wall structure was predicted. As a result, at the place away from the reinforcement about 70cm or more, it was shown that vertical stress increment becomes quite small.

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Based on vertical stress increment due to pull-out of reinforcement, a model to evaluate shear strength on sliding surface in a reinforced soil structure was re-proposed. In order to verify the mechanism, a series of biaxial compression test during pulling-out of reinforcement was carried out. Based on test results, it was shown that the increment of shear strength was caused by pull-out of reinforcement. Furthermore, shear strength increment was evaluated based on relative displacement and stress increment.

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The paper describes a series of reliability analyses that were carried out to investigate the effect of statistical property of soil and reinforcement on reinforced soil structures. Statistical analyses were carried out to determine the probability distribution of the tensile strength of reinforcement. Limit state exceedance probabilities of reinforced slopes and retaining walls were obtained from the first-order and second moment (FOSM) method. Results of reliability analyses conducted with different average and coefficient of variation (COV) of soil and reinforcement parameters showed that the tensile strength of reinforcement can be assumed as a constant under the condition with a lower COV value. The effect of probability distribution of tensile strength of reinforcement is insignificant on reinforced soil slopes, while it is significant under the condition with a higher COV value on reinforced retaining walls.

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Thrust force acts on pipe bend due to internal pressure. In previous study, the lightweight thrust restraint having anchor plate and geogrid has proposed and the effect has proved by lateral loading tests. In addition the resistance mechanism of new method has investigated by distinct element analysis. In this paper, a relationship between incremental resistance and horizontal displacement was modeled based on the resistance mechanism. In addition, using this model, simulation of tests was carried out. As the results, proposed model was good agreement with test results.

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Commonly concrete blocks are installed on pipe bends subjected to thrust force. However damages, separation of joints, have been occurred due to its weight during large earthquake. In previous study, the lightweight thrust restraint with geogrid and anchor plate was proposed and the effect was proved by model tests. In this study, the large-scale tests for new method were carried out in the large pit (8.4m×5.4m×4m), using the pipe bend having a diameter ∅300. As the results, the resistance force using this new method increased 60% comparing with non-reinforced case. In addition it was clarified that the degree of this effect was depended on the stiffness and length of geogrid.

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This paper reports a long term stability of geogrid reinforced embankment constructed in 1995 in which it is 20m high and gradient of slope is 64°C. Formerly, the reinforced embankment was designed by two types of stability analysis based on earth pressure theory or Fellenius method. As a result, placement of geogrid was different due to a difference of shapes of slip surface and definition of safety factore in each theory. This embankment was designed by combining two theories and by using applicable soil parameters, so that an optimum placement of geogrid was determined. To verify a stability of the embankment, FE analysis assuming elastic-plastic behavior of soil is applied. This paper proposes a design method of reinforced embankment and determination of soil parameters by comparing the result of FE analysis with limit equilibrium method.

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In Shizuoka Airport Construction Project a high filling (21m high) is obliged to protect a kind of precious plant (Tashiroran in Japanese Name), so we applied the fill reinforced by geosynthetics. During filling we observed the behavior of the fill (settlement, horizontal displacement, eath pressure, pore water pressure, strain of geosynthetics). From the resuruts of above mentioned field observations it is clear the fill is a sense of stability. This paper describes fill construction and the resuruts of field observations.

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In this research, an innovative and cost-effective earthquake resistant design technique is developed using a novel geosynthetic materials that can reduce the damages of structures during devastating earthquakes. In the developed earthquake resistant technique a smart geosynthetic material known as tire chips is utilized as a seismic performance enhancer.
A series of underwater 1g shaking table test was conducted on a model gravity type quay wall. Two test cases were examined. One case involves a quay wall with the conventional backfill. Another case involves a similar quay wall but reinforced with tire chips. The seismic increment of the load acting on the quay wall and the associated displacement, as well as the excess pore water pressure in various locations of the backfill were measured during the tests. The results reveal that the seismic load against the caisson quay wall could be significantly reduced using the sandwiching technique. In addition, the technique could significantly reduce the earthquake-induced residual displacement of the quay wall.

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A method of installing large compressible materials over a box culvert is one of the methods to reduce vertical earth pressure on a box culvert. From the geotechnical point of view, it is indicated that the waste Expanded Poly-Styrol (EPS) will be effective as a material for reduction of earth pressure.
In order to confirm the effectiveness of the heat compressed crashed EPS (HCCE) as a material for reduction of earth pressure and the mechanism of the reduction effect of vertical earth pressure, the earth pressure on a model box culvert were measured during the vertical loading process in the model tests. It was confirmed that the reduction effect of vertical earth pressure was strongly related to the relative difference of the compression settlement in the ground.

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Air-formed lightweight soil is made by mixing air bubbles into cement-treated soil. The air-formed soil is a geomaterial with high rigidity and strength, so that it shows usually a brittle behavior in deformation-strength property. It is expected that the brittle behavior of the air-formed soil will be improved by mixing short fibers. In order to investigate improvement effect of the strength of air-formed lightweight soil due to mixing various types of short fibers, triaxial compression and bending tests were performed. Three kinds of short fibers are used (nylon threads, waste paper and PET short fibers). Nylon thread is used in place of waste fishing net, waste paper fiber is made by breaking into flocculate, and PET short fibers are a recycle material from waste PET bottle. Increases of residual strength and bending strength of the air-formed lightweight soil by mixing short fibers were clarified. It was also confirmed that short fibers made from waste materials is useful for improving the brittle behavior of air-formed lightweight soil. Furthermore, environmental load of the lightweight soil was evaluated from viewpoint of recycling of constriction surplus soil.

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Stacked soil bags have high compressive strength when compressed vertically, but considerably low resistance against lateral shearing. For this reason, sliding failure would be the fundamental concern in soil structures of stacked soil bags. In this study, to increase resistance against sliding, soil bags were stacked in the inclined direction as castle walls and rock walls. Their shear characteristics as well as those when stacked horizontally were examined. Three layers of soil bags stacked in the inclined (δ=18°) and horizontal (δ=0°) directions were prepared using two kinds of backfill materials, Toyoura sand and recycled crushed concrete aggregate. Lateral shear tests of these soil bags were conducted at different vertical confining pressures (30kPa, 150kPa, 300kPa). Test results showed that the shear strength of inclined stacked soil bags (δ=18°) is much larger than that of horizontally stacked soil bags (δ=0°). It was found that the failure mode is slippage between soil bags at low confining pressure while shear failure of the backfill in the soil bags at high confining pressure. It was shown that soil bags backfilled with crushed concrete aggregate had higher resistance to shear deformation than soil bags backfilled with Toyoura sand due to a high particle diameter and a high shear strength.

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High bearing force and cost effective construction methods can be possible, if used tires are recycled in original form. But such reusing methods are scarcely conducted. In this paper, we make laminar bodies which are packed by granular materials in the hollow center of the tires, using original tires. We validated the characteristics of the laminar bodies thorough compression tests. The experimental results reveal that laminar bodies have high strength especially in pre-stress conditions. In terms of land formation, we propose the easier and earlier construction method. These construction methods can reuse large amount of used tires and contribute to the environment conservation.

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A number of conventional type bridges comprising of a pair of RC abutments supporting a bridge girder with unreinforced backfill collapsed during many previous earthquakes. To develop a new bridge system that has a substantially high seismic stability at a high cost-effectiveness, the seismic stability of three conventional bridge types, which are the gravity type abutment bridge, the integral bridge and the geosynthetic-reinforced soil retaining wall (GRS-RW) with a full-height facing (a FHR facing) as well as a new type was evaluated by a series of shaking table tests. Collapse modes of the four types were examined. It is shown that the new type bridge, which comprises of an integral bridge with a GRS-RW with a FHR facing, has the virtues of the two types while alleviating their drawbacks.

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A new bridge system comprising of a pair of geosynthetic-reinforced soil (GRS) retaining walls having full-height rigid facings that are unified with a girder, without using girder supports, is proposed. To validate the seismic stability of this new bridge system (called the integral GRS bridge), in particular to evaluate the effects of the connection strength of reinforcement at the back of facing, a series of 1g shaking table tests were performed on scaled bridge models comprising of air-dried Toyoura sand as the backfill having different connection strengths. The seismic stability increased with an increase in the connection strength. The test results showed that, for a sufficiently high seismic stability of the new bridge system, it is necessary to ensure not only sufficiently high tensile rupture strength of reinforcement but also sufficiently high connection strength and pull-out resistance.

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The conventional bridge system consisting of unreinforced backfill and a pair of RC abutment needs long-term maintenance of girder-supports. The settlement of backfill forming a bump and a low seismic stability are other problems. A bridge comprising of a pair of geosynthetic-reinforced soil (GRS) walls directly supporting a girder with full-height rigid (FHR) facing is structurally simpler. It has a limited allowable girder length, needs long-term maintenance and has a low-seismic stability of the girder-support system. The integral bridge system is structurally simpler, but the thermal cyclic displacement at the facing increases residual earth pressure and backfill settlement. A new bridge system combining a pair of GRS walls with FHR facing and an integral bridge, taking their advantages while alleviating their problems, is proposed. A series of shaking table tests on scaled models of these four bridge systems were performed to validate a high-seismic stability of the proposed system.

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The design at the earthquake of the Geotextile reinforcement retaining wall industrial method is done based on “Design and construction manual of the reinforcement soil that used the Geotextile (revised edition February, 2000)” now. The reinforcement soil wall has passed several-time seismic hazards. The reinforcement soil wall has high stability because it maintains the function as the soil structure. However, there is a part that has not been clarified yet about the behavior at the earthquake of the Geotextile reinforcement soil wall. A reasonable design method that suits actual behavior is hoped for. This research understands the change of the reinforcement soil wall at the full-scale level by the centrifuge shaking table test in the soils of the overall transforming behavior, the soil pressure, and the acceleration, etc.

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Due to the 2004 Nigata-ken Chuetsu earthquake, a lot of fill structures collapsed. It seems that strength of fill structures was loosed because of rainfall induced by typhoon before this earthquake. So, using a set of numerical analyses, we evaluated correlation between rainfall and earthquake in the damages of a lot of fill structures. In this paper, we introduce the outline of collapsed fills, laboratory tests of fill materials, methods of numerical analyses, and the results of infiltration analysis. We choose the fills in the vicinity Jouetsu Line 220k300m and 221k000m. Both of these fills were damaged severely and re-constructed with reinforced soil. A set of methods of numerical analyses consists of infiltration analysis, dynamic analysis and Newmark's method. Using infiltration analysis, we evaluated moisture-content state of the collapsed embankments and rainwater drainage of the reconstructed embankment.

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The 2004 Niigata-Ken Chuetsu Earthquake caused great damage to embankments and retaining walls. The possible primary factor relevant to the great damage is loosened ground induced by a rain of typhoon before the earthquake. This paper describes the investigation of the relevance of the earthquake and heavy rainfall to the structures' damage and mainly reports results of the dynamic analysis. The locations of the analytical model are 220km300m and 221km000m of Jouetsu line. Response accelerations and deformation of the damaged and restored embankments were compared based on the results by the dynamic analysis. It is clearly shown that the seismic stability of the restored embankments significantly improved as compared to that of the damaged embankment.

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In order to review the seriously damaged railway embankment due to the 2004 Niigata-ken Chuetsu Earthquake and evaluate the seismic performance of reconstructed embankment which is geosynthetic-reinforced soil wall with rigid facing, the seismic stability and residual deformation analyses were conducted. The method of seismic stability analysis was executed by the limit equilibrium method and the seismic residual deformation analysis was applied Newmark's sliding model to the slip circle. As a result, it is shown that the simulated residual deformation due to earthquake is corresponding to the actual magnitude of failure and predicted one become to the effective and practical index of the seismic performance of reconstructed embankment.

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Authors examine reinforcing effect of geogrid for stabilized soil. The influence of the shape of geogird is investigated by laboratory test. In this paper, numerical failure analysis method for reinforced stabilized soil based on micro mechanics concept. Periodical structure model is used for express the inflence of gegirid shapes. The proposed model can express tensile resitance behavior of reinforced stabilized soil.

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Authors examine reinforcing effect of geogrid for stabilized soil. In this research, the effects of drainage condition and strain rate condition were investigated in the laboratory test. In a series of the test, tensile strength of reinforced stabilized soil was measured in the pseudo-over or normal consolidation condition. As a test result, it was cleared that drainage condition does not affect on the reinforcing effects. And it was cleared that it becomes remarkable in the pseudo-normal consolidation condition.

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Proper estimation of soil reinforcement loads is key to accurate internal stability design of geogrid reinforces soil walls. In this paper the estimation model of soil reinforcement loads, called K-stiffness Method as proposed by Allen et al. (2003) is extended to the case of cohesive soils. Design methodology with the modified method also discussed. Modified K-stiffness Method can result in substantial cost saving.

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Cement-mixed gravel is often used for important soil structure allowing a limited amount of deformation. However, an undisturbed core of cement-mixed gravel recovered from the backfill of the newly constructed bridge abutment showed a variability of strength characteristic. This was mainly attributed to the uneven distribution of cement slurry in the gravel, but this did not become a critical problem because the horizontally arranged geogrid reinforcements prevents weak zone from forming a failure plane. Further, the reinforcements are expected to enhance the extension strength of the cement-mixed gravel. In this study, therefore, a series of bending tests were performed, and the effects of geogrid reinforcement on the bending deformation characteristic of cement-mixed gravel were evaluated.

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Construction of embankments on soft ground often causes the differential settlement. Then, deep mixing method of soil stabilization and reinforcement techniques are used to reduce this settlement. This combined method offers the low improvement rate of soil stabilization by using geotextile, because embankment load is transferred to geotextile and pile element. This load transfer results from an arching effect in the reinforced embankment over the pile element heads and a membrane effect of geotextile. And it is considered that a search for the load transfer mechanism in nondestructive and 3 dimensions is important for the performance-based design. However, an interaction between soil and geotextile over the pile element heads is going issue and the real behavior has not been observed precisely. Besides this behavior itself appears in the ground so that it is difficult to check such behavior. In this paper, a series of model test for several soils and geogrids was conducted using a settlement test apparatus. The effectiveness of geogrid for the load transfer mechanisms is confirmed based on all the results using X-ray CT method.

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Behavior mode of interaction between geosynthetic material and surrounding soil is seemed in the hyperbolic curve, however, dilatancy effect takes an important role on the pull out friction that leads to have a peak before failure. There behavior of pull out resistance are defined as gradually hardening type and hard to softening type. Two formulas are explained as the general form. Correcting factor is defined as the frictional coefficient adjusted by earth pressure to reveal at 100kN/m² of earth pressure. Two kinds of equations are presented at the base of experiment result using steal material. Characteristic of pullout force of geosynthetics tends to be classifies into the equation that is composed of internal friction angle mainly. And signification of pullout force of geosynthetics has a similar effect of with flat steal and steel rod with smoothed surface.

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Based on the results from 1g shaking table model tests on reinforced soil retaining walls with embedded sheetpile, analysis on the effect of the sheetpile is carried out. Chang's equation is used to extend the formerly developed procedures so as to consider the effects of flexural rigidity and embedded length of sheetpile. The amount of shear force shared by the sheetpile (i. e. effect of the sheetpile) was changed depending on the amounts of flexural rigidity and embedded length. It was found from the analysis by using this extended procedures that both sliding and tilting displacements can be effectively reduced with the increase of embedded length.

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In this study, proposed FEM analyses of pull-out tests ware conducted. This method was combined with joint element method. Frictional coefficient between water proof sheet and non-woven geotextile was identified by experimental analyses that water proof sheet was pulled out. Frictional coefficient between non-woven geotextile and soil was identified by the analyses of the test that non-woven geotextile was pulled out. Conclusively, FEM analyses of the tests that both water proof sheet and non-woven geotextile were pulled out were conducted by using identified frictional coefficients mentioned above. The calculated strains of water proof sheet and non-woven geotextile were compared with those of measured by tests. At the result, it was proved that we could evaluate quantitatively strains of water proof sheet and non-woven geotextile by proposed FEM analyses.

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In this study, we tried to examine the accuracy of estimation for stress-strain curve in biaxial extension condition which was calculated by strain energy density function of waterproof sheets laid on a seepage structure in a controlled waste disposal site. The partial differential value of the strain energy density function was determined by the pure shear test. After a comparison between calculated stress-strain curve and that from the biaxial extension test, calculated values were correspond with the testing data within 10% error for the range from 15 to 40% strain for PVC, 3 to 4% for HDPE and 6 to 15% for SMePE. The previous study says that the strain of waterproof sheet made of PVC laid on backfilling unevenness was at most 15%. Thus, we suggest that the application of strain energy density function for the evaluation of waterproof sheet deformation due to unevenness of backfilling slope in a controlled waste disposal site should be possible.

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It is important to evaluate the factor affecting the tensile forces creating in geosynthetics comprising the liner of waste landfill such as waste weight and working vehicle for designing anchor trench at side slope crest. In this research, FEM analysis was performed for the field test with 5m height waste landfill model for evaluating the tensile forces creating in geosynthetics of liner. In the FEM analysis, the stress-strain relationship of geotextile and geomembrane are modeled by linear elastic and the stress-strain relationship of ash and friction stress-relative displacement relationship of joint element are modeled by hyperbola. By the calculations, the effects of geomembrane stiffness, load and placement of working vehicle on the tensile force were evaluated. The tensile forces of geosynthetics for the liner with two layers of geomembrane are also estimated comparing with the liner with one layer.

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An indoor accelerated exposure experiments and immersion experiments were conducted to evaluate the durability of geomembrane liners. This study specifically examined mechanical properties and surface profile changes. In the indoor accelerated exposure experiments, mechanical properties declined little by little and cracks were observed on the surface of all evaluated geomembrane liners. But, the geomembrane liners' durability was determined to be more than sufficient, and surface change was improved greatly by the protective covering. In the immersion experiments, the influence of various liquids on each liner become clear.

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As capping materials of landfill site, hybrid geosynthetics which consist of porous sheet and nonwoven geotextiles have been developed. Characteristics on waterproof and gas permeability of these hybrid geosynthetics were examined by laboratory tests. Construction test was also conducted to evaluate construction durability of them under the real configuration of capping technology in landfill sites. As the results, the newly developed hybrid geosynthetics have very good characteristics on waterproof, gas permeability and construction durability, and are available to apply practically to landfill sites.

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Authors developed the repair method using geomembrane that have excellent waterproof performance. We examined the geomembrane by the accelerating tests that assumed deterioration in various exposure conditions of a accelerated weathering test, hydraulic resistance tests, chemical corrosion resistance tests, a heating deterioration examination, heat-proof and cold-proof examinations, etc., we executed the tensile test and the expansion and contraction repetition test of the geomembrane. As a result, we confirmed the following performance of the developed repair method is excellent.

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We have developed the large strain sensor used by BOTDR for monitoring of geomembrane sheet in coastal disposal site. The large strain sensor composes with the tight optical fiber and the slacked optical fiber to measure the small strain and large strain of the geomembrane sheet. We carried out the large size (3m length and 0.5m width) tension test and the middle size model loading tests to estimate the performance of the large strain sensor.
And we have recognized the basic performance of this sensor and we have investigated the specification of this strain sensor to use in the coastal disposal site.

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It is important to estimate the durability and the damage risk of the hydraulic barrier structure in the disposal site. But there are few example of the estimation about the damage risk for the geomembrane and the hydraulic barrier. We have developed the new type hydraulic barrier system (the triple liner system) which have high hydraulic barrier performance. In this paper, we have studied the durability against the damage of the triple liner system, and we have confirmed the high hydraulic barrier performance even if the several rods (diameter 5-10mm) stick into the TLS.

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Geosynthetic clay liners (GCLs) are increasingly used as a component of present bottom liner systems in waste containment facilities because of their relatively low cost, easy installation, and excellent barrier performance to water. In the design of the bottom liner system, it is necessary to consider the basic performance of GCLs and the factors affecting its performance. However, there are still so few reports regarding the performance evaluation of GCLs in consideration of a peculiar condition in waste containment facilities that sufficient foundations to design the bottom liner system with GCLs have yet to be aggregated. This study focused on the evaluation of the hydraulic condcutivity of GCLs under the following peculiar conditions: (1) Permeation with electrolytic chemical solutions such as waste leachates, (2) Prehydration with moisture in soil base layer, and (3) Confining pressure due to weight of buried wastes. Although the permeation of electrolytic chemical solutions significantly deteriorates the barrier performance of GCLs, the prehydration and confing pressure generated in waste containment facilities can adversely improve the barrier performance (≤1.0×10^-8cm/s as the hydraulic conductivity).

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For the purpose to clarify the required performance of fibers used in the geomaterial for barrier system of coastal landfill sites that improves toughness of the brittle cement treated clay by inclusion of fibrous materials, a series of laboratory mixing tests were conducted. The effects of fiber types on mechanical and hydraulic properties of the geomaterial were examined by comparing the results from unconfined compression tests and hydraulic conductivity tests. No major differences were observed in the results that were obtained from five types of fibers; PVA, PA, PP, recycled PP and PE.

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We have proposed a new reinforcement technique called Hybrid Sandwiched Reinforcement (HBS) where the thin sand layers are placed above and beneath the geosynthetics to increase the mechanical potentials of cohesive soil embankment and foundations. This reinforcement method has the advantages that reinforcement improvement as well as maintenance of hydraulic conductivity which is more marked than the cases without the sand layer. Successive to the previous works by the authors, in the present study, we performed small scaled-model tests on embankment with and without reinforcement with and without sand layer placed. The results from model tests are interpreted with a special emphasis on the improvement of toughness of embankment reinforced with HBS. It is made clear that HBS plays a role to improve the toughness more markedly than the case with conventionally-adopted placement geosyntheitcs in clay embankment. It is inferred from the results from direct-shear tests on investigation of the interaction between geosynthetics and sand that this improvement of toughness of embankments is caused by the increased frictional force exhibited between geosynthetics and sand.

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