[in Japanese]

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The paper describes a series of reliability analyses that were carried out to determine the reliability index of mechanically stabilized earth (MSE) walls. Sensitivity analysis results giving reliability index as a function of soil parameters were carried out and compared to conventional factor of safety approaches. Variables investigated in the reliability analyses included wall height and average and coefficient of variation (COV) of input soil parameters and seismic coefficient. Results of sensitivity analyses conducted with different average and COV values for the soil showed that the sensitivity of results to friction angle and seismic coefficient was much higher than for unit weight of the backfill.

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Authors compared and examined the limits state design methods for reinforced soil wall in British, Hong Kong and Nordic. Additionally, possible problems in switching to limit state design method are discussed. In this paper, contents of each method are introduced and these are compared on the item such as application field, ultimate and serviceability, and partial safety factor. These results will contribute for the development of limit state design method for geosynthetics reinforced soil wall.

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The method of determining the confining effect parameter defined in the shear test of geogrid reinforced soil is discussed. The mechanism of increase in normal stress on sliding surface in the shear test of reinforced soil and increase in vertical stress in pull-out test of reinforcement in soil is examined. The ratio of the increase in vertical stress is calculated from previous pull-out test results, and its comparison with the confining effect parameter is carried out. Consequently, it is shown that both values are almost equal each other and that the confining effect parameter can be determined by pull-out test results.

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Unconfined compression tests of an urethane-foam in geosynthetics that was cut out from the vertical and the horuizontal directions were conducted to investigate anisotropic elastic behaviour. The urethane-foam exhibits a conspicuous anistropy in elastic modulus and Poisson's ratio, depending on the direction from which the specimen is cut out. Anisotropic mechanical parameters of elastic modulus and Poisson's ratio have been evaluated based on the experimental results. Subsequently, to investigate the effect of the anisotropy on horizontal earth pressure degradation, a model test and finite element analysis with two kinds of the isotropic elastic model and anisotropic one have been carried out. Comparing the experimental and analytical results, it was made clear that it is important for evaluating horizontal earth pressure of the urethane-foam to take into consideration of the mechanical anisotropy.

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This study focus on the erosion control method with filling soil into geosynthetics and planting. Authors conducted laboratory test to investigate the effect of compaction condition on the filling of sandy soil into geosynthetics. Results of the laboratory test were discussed by using new parameter to show the degree of filling. These results will be contributed for the developing of construction control for the erosion control method with geosynthetics

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Although the iron bedding basket is conventionally used widely as an antierosion works or a bed protection work, use of a geotextile bedding basket which became recent years. However, there are many portions which are not solved about the mechanism of the deformation and destruction, the method of a design. About a geotextile bedding basket, the purpose of this research verifies he deformation, destruction, and the hydraulic characteristic, and proposes the method of a unsettled design. This paper reports focusing on each experiment result as the first step for solving these.

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In a start-arrival shaft of a shield tunnel, the construction method is developed and is spreading gradually, in which a shield excavator can pass through while cutting the underground continuation wall by attaching to the wall the fiber-reinforced structure, such as CFRP (carbon fiber reinforced plastics) and glass-fiber-reinforced urethane foam.
However, there still remain many problems, such that pipe work gets clogged with chips, and that it is difficult to design the strength of a fiber-reinforced structure, etc.
Writers have been studying about the cuttable structure made from the fiber-reinforced concrete, for example, the stake using the bag.
This paper describes basic performances, such as the intensity, the cutting performance and water-tightness, which are required for the structure made from the glass-fiber-reinforced resin.

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Cement stabilized soil reinforced by geogrid for sea wall called SG-wall has already been found its efficiency based on the model test results to increase the strength of the reinforced soil block and to resist separating. This reinforced block is aimed to apply for construction of sea wall encountered with deepening sea bed and as a countermeasure against earthquake. This paper presents the applicability of three numerical models to predict deformation and ultimate strength for reasonable designing procedure. Three types of modeling are Winkler model, crack models that extend in the surface zone and develop in the vertical direction. As result, vertical crack model is found to give a approximate value corresponding to the test results.

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The thrust force generated by the action of internal pressure tends to move the bend of underground pipeline to the back side. This thrust force is supported by the passive earth pressure that affects the back of ground. The concrete block is commonly used at the bend to minimize the thrust.
However, the earth pressure distribution is not readily known when the pipe moves laterally in the ground. In addition, such heavy concrete block becomes a weak point during earthquake, since it is different from the behavior of the pipeline.
In this paper, model tests were carried out using a steel pit having length of 2m and the model pipes having a diameter of 90mm that was equipped with geosynthetics as the lateral anchors in order to clarify the effectiveness of this new method. In addition, similar tests were conducted using a model piece of square on the assumption of the concrete block, to compare with present design method.
As the result, it was found that the weight saving new protecting method with geosynthetics was extremely effective against thrust force. Furthermore, using results of tests having different depth of cover, the equation for estimate was suggested, considering the resistance generated by geogrid.

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The method of construction “expanded nailing method” which reinforces a natural ground with pouring in mortar into the jacket inserted in the natural ground was developed. The nailing is mainly used for reinforcement of the natural ground in a narrow place. However, in the case of the weak viscous cohesive soil like the Kanto loam layer, by the conventional method of constuction, skin frictional resistance becomes small and sufficient pull-out resistance is not acquired.
Then, the method of construction which develops the large reinforcement material of skin frictional resistance by carrying out high-pressure pouring of the mortar in the pipe-like textiles inserted in the foundation was devised.
The result of the model foundation experiment for searching for the form optimal as reinforcement material is described. Moreover, the influence of consolidation the foundation is also considered.

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The Controlled-muck-deposit (landfill) of Hakkoda Tunnel is filled the deposit muck containing the sulfur compound. The sulfur compound gives acidity water into contact with air and water.
Then this controlled-muck-deposit was constructed by lining and capping of geomembanes. And the leachate-tank is setting water treating system. This paper states the case of applying the geomembane floating cover to the leachate-tank.

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A leakage of water in concrete waterway is a serious problem for a waterway administrator, and its radical solution is being searched for. However, the present situation is that no fully satisfactory method has been yet. So, we have newly developed a surface repairing method to prevent a leakage by installing a flexible geomembrane on the wall of the waterway made of concrete blocks, and to lead rear water (arising from the concrete blocks joints) into the waterway smoothly not by fixing geomembrane on the whole surfaces but by dispersing geomembrane, and by using a back flow checking valve on the bottom. In this paper, the outline of the experimental construction conducted with this geomembrane in a waterway in the Kinki Region was described.

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Strains induced in a geosynthetics liner sheet that was installed in the slope of a controlled coastal disposal site were measured in the construction stage of filling the protective soil layer. Also, laboratory tensile tests and the corresponding FEM were conducted to obtain the relationships between the measured values by means of strain gauges and the actually induced strains in the liner sheet since the former becomes smaller than the latter that is made of very flexible materials. It was observed that the strains were induced both in the downward and horizontal directions due to the shear forces by the self weight of the protective soil and the deformation caused by the uneven surface on which the liner sheet was placed under the sea level.

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To develop an on-site non-destructive testing method for detecting the degradation of the geomembrane at a landfill site, the authors have been studying the applicability of Visible/Near-infrared spectroscopy. In the past studies, the authors showed that the reflectance spectrum of a geomembrane changed at some particular wavelengths after that the geomembrane had been soaked in chemicals, and that there was the correlation between the change of reflectance spectrum and the change of strength, stretch and weight of the geomembrane. However, there were some problems in the soaking test. One was that the test has little reality that both side of the testing samples were soaked. Another was that there was large dispersion of the reflectance change among the samples. In this study, the authors confirmed the usefulness of Visible/Near-infrared spectroscopy again by carrying out “one-side” soaking test. They also attempted to improve the accuracy of this method by adopting new indices such as the spectrums of 2nd order differential coefficient.

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The geomembranes used as a component of a liner system in waste landfill are occasionally deformed and occurred a tensile strain by non-uniform settlement and machine working. In this paper, the tensile strain of geomembranes is measured by the simple tensile loading test using optical fiber sensing in order to build a monitoring system to check extreme deformation. From the experimental results, it is confirmed that the tensile strain of sheets can be measured using optical fiber sensing.

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This paper summarizes the mechanisms related to the hydraulic bursting behaviors of waterproof sheets, applied at a seepage control structure in a coastal confined waste disposal site. The waterproof sheet, used in this study, is made of Polyvinyl Chloride (PVC), which is mainly installed in a coastal waste disposal site. Deformation behaviors of waterproof sheets were addressed in terms of strain distribution obtained from experiments. We also developed an evaluation method of the deformation and strength characteristics of waterproof sheets based on transforming the experimental data into stress-strain curves. The reliability of transformed strain data was checked to compare with the experimental strain data.

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Results of direct shear strength tests on various lining sheets, i. e. PVC, LLDPE and TPO-PP with nonwoven geotextile are shown. The results show that angle of shear resistances is PVC>TOP-PP>LLDPE with nonwoven geotextile in wetted condition. It is considered due to the difference of their elasticity affects the results. Also the angle of shear resistance is smaller on the backside of geotextile compare to its front side. Further it is suggested that even lower shear resistance of LLDPE could be got higher resistance by improving surface roughness.

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The geomembranes are frequently used in barrier system for landfill site. According to a recent research, Volatile Organic Compounds (VOCs) can permeate the geomembrane. In this research, immersion/sorption tests were carried out to examine four kinds of VOCs. Chemical compatibility and the mechanical property of the TCE treated geomembranes were examined by using tensile and puncture resistance test. Consequently, rapidly degradation of rubber type sheets and excellent durability of HDPE sheet was confirmed. Though, the tensile strength of HDPE sheet was decreased by TCE solution treatment. Moreover, the change of the penetration resistance value was clarified. When the geomembrane in the landfill site and the polluted soil containment design applies in the future, it can propose the condition of an effective hydraulic barrier system.

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The authors have studied outdoor exposure durability about 10 years. They checked tensile and adhesion many times continuously. They also evaluated surface of the geomembrane liners with microscope. Then it becomes clear that the geomembrane liners which they have tested have good performance for durability. But the thin surface of the geomembrane have damaged, so they have tried to cover the geomembrane liners with geosynthetics to get more durability. They have checked the surface of the geomembrane which have covered with geosynthetics for ten years by using the surface analysis method of FT-IR and confirmed the effect on ultraviolet rays protection.

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It is very important for the design of the waste landfill liner to determine the tensile force induced in the liner sheet, specially on the slope of landfill with the reclamation of waste. In this research, centrifugal model experiments and FEM analysis were conducted to study the change of tensile force of landfill liner with the reclamation of waste. The result of the change of tensile force in fixed end was obtained and the effect of the stiffness of geosynthetics on the induced tensile force was also analyzed.

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The shape of the bottom liner systems is complicated in Japan, since the landfill sites are often constructed on a valley in a mountainous region. The bottom liner system of landfill sites is influenced by some environmental stresses, such as leachate, groundwater, temperature and load, during a long period. Durability is thus required to the liner, and the environmental stresses should be monitored. This paper describes the monitoring results of an operating landfill site, and suggests the landfill monitoring methods suitable for maintaining the liner performance. The monitoring of the groundwater quality, as well as the stress monitoring, can observe the health of the liner system, and both of these would provide an effective risk communication.

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The characteristics of vacuum consolidation are discussed first. Then, the effect of geosynthetics drains (GDs) installation depth and middle sand layer under vacuum consolidation are investigated. For two-way drainage ground condition, an equation for calculating the optimum GD installation depth has been derived. In case there is a middle sand layer within a clayey deposit, to prevent the leakage of vacuum pressure from the sand layer, one of the methods is to put air-tighten seals on the GD passing the sand layer. An equation for determining the penetration length of the seal into the adjacent clayey layers has been provided also. Finally, two-dimensional (2D) finite element analyses were conducted to investigate the effects of GD installation depth and the middle sand layer.

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Advantageous aspects of sandwich-type reinforced earth structures combined with geosynthetics and sand mat are highlighted in this report. Those aspects were elucidated by two kinds of laboratory tests: (1) model footing tests on improvement of bearing capacity and deformation for reinforced earth structures; and (2) large consolidation tests for improvement of hydraulic conductivity, including both vertical permeability and horizontal transmissibility characteristics of geosynthetics. Results from both laboratory tests indicated the following:
i) Sandwich-type reinforcement combined with geosynthetics and sand mats increases stability and decreases deformation of earth structures. In particular, the sandwich structure is effective for providing toughness, which has remained an important issue for reducing infrastructural maintenance and costs.
ii) Hydraulic conductivity of geosynthetics used for this type of earth reinforcement can be maintained for a long period. Such conductivity sometimes disappears, particularly because of clogging when geosynthetics are adopted in embankment construction using fine-grained soils. This fact indicates that the sand mats which are laid above and beneath geosynthetics play a salient role in preventing clogging of geosynthetics that occurs by intrusion of fines from cohesive soils.

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This paper presents an experimental investigation of the ultrasonic removal of clogging of six commercially available geotextiles. The clogged specimens were exhumed from two fine-grained soils, which were previously consolidated from slurry stage under a consolidation pressure of 400kPa. The mechanism of ultrasound and formation of micro-bubbles in a sort of “cold boiling” or “cavitation” within liquid medium have been explained. The in-plane and cross-plane flow capacities of the clogged geotextile specimen have been evaluated before and after ultrasonic cleaning and results are presented in a design chart signifying the beneficial effect of ultrasonic cleaning. With increasing confining pressure clogging caused more reduction in the cross-plane flow capacity than the in-plane flow capacity. Ultrasonic cleaning efficiency for all clogged geotextiles was more than 80% @ 5 minutes washing time. The thinnest (2.2mm) geotextile was severely affected by clogging, however, after ultrasonic cleaning the clogging potential reduced to unity, which was not affected by increasing normal pressure.

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There are a variety of soil remediation methods at present. In this study the effects of geotextile drain on soil remediation were investigated in the case of reuse of surplus soil for embankment. A laboratory model test was carried out using both cohesive and sand soils. It was found from the experiment that drainage and soil remediation effects were affected by overburden pressure, gradation of soil particles and placing condition of geotextile.

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The new type of geogrid-reinforced soil wall combined with soil cement has been developed in recent years and the details are reported in IGS Symposium and Geosynthetics Technical Information. This method was applied at more than 20 construction sites until now. In this paper some of them were introduced and measurement data obtained in situ were reported. Moreover, the pullout tests of geogrid were conducted and results of it were described.

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In the construction of upper reservoir in KYOGOKU hydroelectric plant, it is obligated to build some co-reservoirs for prevention the flowing-out of muddy water into the protected forest around the site. To secure the place for co-reservoirs in the restricted area, construction of the embankment with inclines of 1:0.3 was necessary in some places. For this purpose, soil reinforcement with geogrid was employed. The total execution area of geogrid was approximately 160, 000m², and steep (1:0.3) embankment with height of 20m was constructed within only about three months. Although, allowed period for construction of the embankment was relatively short, stabilization of the slope must be maintained. In order to control the stability of embankment during construction term, execution management with in-situ monitoring and numerical prediction were conducted. Especially, numerical prediction with finite element analyses was considered to be also useful to estimate the behavior of embankment in the future.
This paper describes the observed behavior of embankment during the construction term, results of numerical analyses and important matter for constructions of embankment using geogrid.

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Due to high percentage elongation fracture (approximately 15∼20%), high density polyethylene is suitable for following to deformation of reinforced soil wall. It has reported that under confining effect the strain of geo-textile is less and strength is larger than under no confining effect. It is technically difficult to measure the strain at the break point in the fill. We are considering that it is safer to afford the elongation fracture for flexible structure of which wall is deformed to a few percentages. We report that we have done the measurement of behavior of 10m fill, the demolition test of reinforced soil wall, and the FEM simulation of large scale earthquake, in order to verify of reliability of reinforced soil wall being used high density polyethylene geo-grid and thin concrete panel

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This paper is intended as an investigation of effects of input wave properties on seismic stability of reinforced soil wall. For that purpose, the centrifuge shaking table test series was conducted with regular sin wave or irregular wave and behavior and residual deformation of reinforced soil wall during earthquake were compared. If the inertia force of active direction exceeding about 20G was applied to the wall, it began to deform. Moreover it did not depend on the regular or irregular wave. Furthermore, it was found that the wave which was applied at first was much effective and deformation mode was influenced.

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The new type of geogrid-reinforced soil wall combined with soil cement was developed in recent years. Regarding the seismic tability, it was studied by the centrifuge shaking table test and very high seismic stability could be shown as compared with conventional geogrid reinforced soil wall although the tension crack was induced in the soil cement wall. The purpose of this study is to cut down the construction cost. For that purpose, narrow width of wall was devised and the centrifuge shaking table tests were conducted in order to check the seismic stability. As the result, the high seismic stability was shown even if the wall width was narrow.

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Results from an analysis of model shaking test data conducted under normal gravity field are presented. The relationships between the wall top displacement and the resultant normal force of earth pressure are completely different between reinforced-soil and gravity type retaining walls. At high seismic loads, the rate of increase in the wall top displacement is reduced significantly with the reinforced-soil retaining wall, resulting into ductile behavior. Such responses reflect possibly the different displacement mechanisms of these retaining walls.

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Soil stabilization combined with earth reinforcement has shown considerable advanced. Authors investigated the effects of geotextile-reinforcement combined with advanced stabilization to reduce the compressibility of soil with high water content. Compression tests were carried out on the stabilized soil specimens prepared in CBR mold. The tests indicates that one layer of geotextile laid horizontally in the specimen could reduce the compressibility and thereby the amount of the stabilizer.

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A series of model tests of geosynthetics-reinforced soil retaining wall with full-height rigid facing were performed by loading at the crest with a strip footing. It was confirmed that the following three deformation mechanisms control the deformation of the structure: a) the bearing capacity mechanism for a strip footing; b) the reinforced soil retaining wall mechanism; and c) interactions between the backfill and the reinforcement. Due to effects of the viscous properties of backfill and geotextile reinforcement on these mechanisms (mechanism c in particular), the reinforcement tensile stress, and therefore the earth pressure on the back of facing, decreased with time when the reinforced soil retaining wall was remote from the failure condition.

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The reinforcing effects of geogrid-reinforced soil are generally evaluated by the tensile effect due to the tensile force of a geogrid. However, we have experimentally examined the existence of the confining effect, which is one component of the reinforcing effects and is independent on the tensile force of a geogrid. An evaluation method in which the reinforcing effect can be divided into tensile effect and confining effect is proposed related to the dilatancy rate of reinforced soil mass. The mobilized confining effect is given by a function of the dilatancy rate, in which the basic idea is in the assumption of the dissipated energy done by unit volume of the reinforced soil mass. This submission formula is proved by result of two-dimensional compressive test and plane strain compressive test.

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Reinforce a soil wall with geogrids has a soft structure characteristic. Therefore, bearing capacity is not really needed when you compare it to a concrete wall, such as a gravity retaining wall and a concrete L-shape retaining wall. However, constructing embankments on unstable soft ground is increasing for effective land use in recent years.
Moreover, there are also many cases that the embankment materials cannot keep friction such as cohesive soil and loam. Then, the writers thought it could be expected to get bearing capacity, and increase the friction with mixing foamed scrap glass, which is a lightweight granular object, into foundation soil material.
In this research, it has inspected the influence of the frictional resistance between geogrids and soil constant by changing the rate of mixture of the scrap glass.
In the experiment, it has examined that the more you increase the rate of mixture of the scrap glass, the more it increases the angle of shear resistance. Furthermore, it turned out that the friction characteristic between geogrids is the same as the mixed soil.

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Earth reinforcement technigue has been widely used around the world and so far, many research projects for both experimental and analytical aspects such as model testing and numerical analysis have been conducted. However, an interaction mechanism between soil and geogrid is still on going issues and the real behavior has not been observed precisely. Recently, an X-ray CT scanner became a useful tool even for geotechnical engineering as a nondestructive testing apparatus. It is well known that the results from CT scanning can be realized as the change of the density in the material. This apparatus produces visual images in three demension. The objective of this paper is to visualize the interaction mechanism between soil and reinforcement under pull-out test using industrial X-ray CT scanner.

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A number of previous experimental studies showed that polymer geogrid alone as well as sand alone exhibit significantly viscous behaviour. It is shown that the viscous response of geogrid-reinforced sand is also significant due to the viscous properties of both geogrid and sand. Due to their extremely complicated interaction, the investigation of this issue only by experimental study is insufficient. A non-linear three-component model that is known to be able to simulate very well the viscous behaviour of soil was implemented into a non-linear elasto-plastic FE code. The viscous behaviour of geogrid observed in tensile tests and that of sand and geogrid-reinforced sand observed in plane strain compression tests were successfully simulated by the FEM analysis. The FEM analysis showed that the tensile force of geogrid during sustained loading of reinforced sand decreases with time.

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The use of the reproduction material to the main part of a ground structure of a railroad on which train load acts directly is not general because of the influence of the run stability which displacement brings and the difficulty of exchange and repair by material degradation. In order to use it generally positive examination about its application possibility is required. So we tried to apply the recycled crushed stone to the reinforced embankment material, and made it available for the business route over about one year and seven months.

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It was possible to predict the deformation of reinforced soil walls. Then, as the next step, we estimated the strain distribution on geotextiles put wall panels by using the mechanical models we proposed.

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To measure the deformation of sand near the geotextiles, we have carried out research using magnetic force and the hole sensor that we developed as new equipment. These results could utilize for prediction of deformation distributions of the geotextiles.

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The design tensile strength of geosynthetic reinforcement is one of the basic factors in the design of geosynthetic-reinforced soil structures. Although a creep reduction factor has the significant effects on the determined design tensile strength, it is not used in a relevant way, usually resulting in an overly conservative design. A new method is proposed, in which the design rupture strength of geosynthetic reinforcement is first determined without taking into account a creep reduction factor and then the possibility of creep rupture is examined separately. A working example of this new method is presented.

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This construction place is planning the high embankment that used high water content clay (All height 24m). The construction nature, the economical efficiency, etc. of a method of construction were synthetically examined in it. And having used high-strength geowoven as embankment reinforcement material was determined. Now, reinforcement of the embankment using the geotexile has many actual results. But the geotexile used has many grid products with which the restricted effect is expected. The example introduced here is related with the pull out test in the embankment of geowoven carried out in the original position in advance of construction.

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When a reinforced soil structure is used for supporting a heavy important structure with a severe limit of deformation, it is quite essential to restrain its deformation against cyclic live load as well as heavy dead load. In cases of reinforced soil pier and abutments supporting bridges for railway or highway, a huge number of cyclic loads with relatively small amplitude is applied, and the residual deformation may accumulate to a harmful level.
In this study, scaled models of reinforced soil pier were tested with cyclic loading. The total amount of the reinforcement was changed to see its effects on the deformation of the structure due to small-amplitude cyclic loading. The elastic modulus of a reinforced soil structure against cyclic loading with a small amplitude is not clearly affected by the total stiffness of the reinforcement. The stress level dependency of the elastic modulus of the backfill material is much more effective. Most of the residual deformation during cyclic loading is due to creep deformation which is caused by high average stress level during the cyclic loading procedures, rather than accumulation of plastic strain generated by each loading cycle. The residual deformation can be restrained to a smaller level when the total stiffness of the reinforcement is higher.

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