An embankment failure often occurs in the events of earthquake and/or rainfall attacks. When seepage water flows into a partly-saturated embankment, the loss of matrix suction is seen involved with saturation, which in turn reduces the stiffness as well as the strengths of the fill material. Conversely, many aspects of the mechanical behaviour of partly saturated soil are still unknown. In this lecture, laboratory devices for measuring deformation/strength characteristics of partly saturated soils are in detail described. Effects of matrix suction on the mechanical behaviour of unsaturated sandy soils are discussed. Based on case study into the stability of a dune, site-investigation practice with in-situ and laboratory tests is newly proposed for estimating the stability of embankment. Theory and practical implications involved with "watertight embankment using L-shaped geosynthetic drain", which has recently been developed by research group at Kobe University are described in depth, together with some applications in practice..

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Tensile force of reinforcement in the direct shear test are mobilized by two factors; 1) a dilation of a specimen and, 2) a discontinuous displacement between upper and lower shear boxes. The tensile force, which mobilized a discontinuous displacement, equilibrates not only a frictional force along the reinforcement, but also a normal force to the reinforcement. This concept conflicts with the conventional assumption, in which a tensile force is equivalent to a frictional force along the reinforcement (e.g., Jewell & Wroth 1987). In this study, the force equilibrium model, taken into account a frictional and normal force on the reinforcement, was proposed. The shear strength obtained by a large-size direct shear test on a reinforced sand specimen were predicted by the newly proposed equation and the conventional one. The results showed that the conventional method overestimated the experimental value at large shear displacement. On the other hand, the newly method had a good agreement with the experimental results.

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To achieve a high seismic stability of a newly proposed bridge type, called the GRS integral bridge, a high tensile resistance of reinforcement layers at the back of the facing is crucial. This resistance is the minimum of the connection strength between the reinforcement and the facing, the tensile rupture strength of reinforcement and the pull-out resistance of reinforcement. To evaluate the pull-out resistance of a rough phosphor bronze grid used in the model shaking table tests performed to evaluate the seismic stability of GRS bridge in comparison with those of other types of grid reinforcements including polymer grids, a series of pull-out tests were performed on these various types of reinforcement embedded in Toyoura sand under different vertical confining pressures. The pull-out resistance increases with an increase in: 1) the covering ratio and surface roughness of the longitudinal members of grid; and 2) the thickness of transversal members of grid. The peak resistance by the surface friction (factor 1) tends to be mobilized earlier than the passive pressure resistance (factor 2). For this examination, we considered a reciprocal effect of this both and made an expression to express influence to give the drawing resistance of the reinforcing structure. According to this expression, the frictional resistance of the reinforcing structure surface and the passive pressure resistance of the cross piece front were added to a certain constant value linearly, but it did not almost increase after it.

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Heavy rainfall is considered to be the main cause of the slope failures that cause collapse catastrophically without prior warning. Therefore in order to investigate the effect of rainfall on the stability of geogrid reinforced soil structures, this paper presents the result from a series of pullout tests for investigating interface behavior between soil and geogrid. By varying the water content of soil sample, the interaction behavior is determined by carrying out pullout tests in a displacement-rate controlled manner. The main test results obtained are presented, followed by discussion on the shear behavior of the soil-geogrid interface considering the effect of moisture content. It is shown that the normal stress level and interface water presence dominate the shear behavior of the soil-geogrid interface in the pullout tests.

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It is considered that the pullout resistance is more affected by the transverse elements than the longitudinal elements. In this study a square and a circle opening type and a plate are tested of pullout resistance in Toyoura sand during the unloading-reloading process through a series of laboratory model tests. The results show that unloading-reloading process reduces the pullout resistance of both two types of geogrid and a plate at peak value and at the residual part. But the pullout resistance of the square geogrid type in this study is decreased more as well as less stable than that of the other two. Moreover, the square geogrid type takes larger displacement to reach to the peak values of pullout resistance than the circle and plate ones do. To discuss the effects, all of the deformation of soil around geogrid is observed while it is pulled out. The PIV analysis shows the mechanism and effects of transverse ribs on the pullout resistance.

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The apparent opening size (O₉₅) of geotextile is a physical parameter closely related to the permeability property and/or amount of clogging of geotextile. In this paper, the various methods for apparent opening size of geotextile are discussed. The apparent opening size tests of geotextile on the wet and hydrodynamic method were performed, and the apparent opening size of each test method was evaluated. Based on test results, an improvement of each test method was proposed. It was found that the value of apparent opening size of geotextile obtained from wet and hydrodynamic methods were near to a theory value proposed by J.P. Giroud.

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In an attempt to reduce the risk for embankment failures induced by recent heavy rainfalls, geotechnical engineers are increasingly concerned with proper method for geosynthetic drains in an embankment. In such case, the in-plane hydraulic transmissivity could be deteriorated implying that clogging of the geosynthetic drains and/or the cross sectional area of the geosynthetic drains could be decreased by the compressive overburden stress. In engineering practice, thus it is great importance to evaluating the performance of geosynthetic drains in soil. In so doing, the insoil hydraulic transmissivity of geosynthetics drains should be properly measured in the laboratory. In this study, the hydraulic transmissivity evaluated under different overburden pressures is focused on the variation of the cross sectional area of drainage material. Modified in-soil test apparatus after JGS(plan) is used with or without three kinds of soils showing different soil particle grading. In this study, the hydraulic transmissivity under different overburden pressures is evaluated. The tests focused on the variation of the cross sectional area of drainage material. Modified insoil test apparatus after JGS(plan) is used with or without three kinds of soils showing different soil particle grading.

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Authors examine reinforcing effect of stabilized soil. Two kinds of consolidation conditions were compared based on the idea that curing and consolidation are advancing simultaneously in the reinforced-stabilized ground. Compared one is a case where an underwater curing period is long and consolidation time is short, the other is a case where an underwater curing period is short and consolidation time is long. Reinforcing effect was evaluated as apparent cohesion regardless of consolidation condition. In a case where underwater curing period is short and consolidation time is long, the higher strength was observed.

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Up to now, hard wall of concrete structure has been used for Geosynthetics reinforced soil retaining wall of structures. However, recently cost reduction and decrease of negative environmental impact have come to be required strongly. Furthermore there is a problem of harmony with the ambient landscape, and the demand for tree planning is high. To comply with these requests, the application of long fiber mixture reinforced soil that uses the vinylon having large strength and high adhesion with cement was examined, with consideration of improvement of easier of construction. In this paper, to understand strength and the deformation characteristic of wall structure by long fiber mixture reinforced soil, pulling out examination for material strength evaluation and load examination with full-scale Geosynthetics reinforced soil retaining wall were executed and the examination result are presented.

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To build up continuous fiber reinforced soil retaining wall, the uniformity of the continuous fiber effects to its performance. In this experimental study, continuous vinylon fiber was examined in scope of spraying processability. For spraying process of cement reinforced soil, continuous fiber is used to mix at the nozzle part. In the properties of the thickness and rigidity of the continuous fiber, there was insufficient dispersion in mixing. Accordingly, suitable range of the fiber properties should exist and they will enable better mixing. Processability was not satisfied in this experimental study, however, vinylon continuous fiber will be able to apply to the geosynthetics for fiber reinforced soil.

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Recently, new geomaterials such as tire chips which is one of recycle materials from used tires has been developed as a reduction method of earth pressure behind caisson or wall structures. However, the mechanical property of tire chips has not been clarified yet. The objective of this paper is to investigate the shear behavior of tire chips. Here, a series of direct shear test with X-ray CT scanning were conducted for the material of tire chips, and the case on sand and two layers of sand and tire chips were also examined in order to compare with the behavior of tire chips. A PIV technique is used to visualize the deformation property in the CT image and the distributions of the displacement vectors and shear strain were measured at each displacement level. Finally, the mechanical property of tire chips was verified based on all the results.

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Model shaking table tests under the 1g gravitational condition on a caisson type quay wall were conducted on a liquefaction prevention measures for backfill sand reinforced with tire chips (tire derived geo-material). The test results have demonstrated that, despite the fact that the tire chips reinforced composite backfill has a very low relative density, there was no liquefaction in the backfill. Also, the earth pressure on the wall and its residual displacement could be substantially reduced, implying a good performance of the soil-structure system during earthquake loading.

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An earth pressure acting on quay wall structures can be reduced if a tire chip is used for the backfill. But, it is a problem that tire chips have high compressibility and it is easy to deform. To prevent this problem, tire chips are considered to be used with mixing with sand. In this paper, a series of triaxial compression tests of rubber sphere specimen was conducted, and investigations of its shear strength and compressibility of rubber sphere specimen and deformation of rubber sphere particles were conducted with X ray CT scanning. Relationship between shear strength characteristics and change of internal structure and deformation of the particles were discussed.

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The geo-cell reinforced wall method that attempts the stabilization of the slope is developed, and it has come to be used domestically in recent years. The usage is to make the retaining wall structure that puts the filling in the honeycomb cell frame made of the high density polyethylene resin and piles it up. In this study, we carried out the shaking table tests to discuss the dynamic stability of the geocell-reinforced soil wall at the earthquake. As the results, we can understand the dynamic failure mechanisms and stability of geo-cell reinforced soil walls.

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Since Kumamoto railcar depot for Kyushu Shinkansen is under construction on a soft clay layer, it was necessary to adopt an accelerated consolidation method for its construction. Therefore, considering various aspects i.e. construction schedule, cost factor, and possible adverse effects susceptible to adjacent structures in this area, adoption of pre-loading method and vacuum consolidation method for the construction anticipated. In addition, an experimental embankment applying the accelerated consolidation method was constructed, and effects and adverse effects at the subject environment have been evaluated according to the method.
In this study, we evaluated soil parameters as obtained previously and the feasibility of modeling of the vacuumconsolidation method by feedback analysis based on substantial data.

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Temporary road was constructed using a Lattice-Frame-Reinforced (LFR) sheet. We confirmed effect of stability of LFR sheet on the soft ground. The N-value of this soft ground is under 10, which depth is 30m. We explored settlement of the road surface and cone penetration resistance after 100 days and 190 days. As a result max settlement of the road surface was 10cm dulling 90 days, and the cone penetration resistance of this point was lower than others. This temporary road is using until 6 months later; we will explore this road when it will remove from the soft ground.

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Many types of countermeasure are applied to prevent rock fall or landslide. While any countermeasures using nets and ropes are made from metal, the fiber material is little used for the rock fence and slope protection work. The construction work becomes difficult in slope using the metal material because of heavyweight of the member. Meanwhile the fiber material is lightweight and flexible, so that it seems that the construction work becomes easy. Because the performance of the countermeasure using fiber material is not clear, the impact resistance test is carried out. This paper shows that it is effective in preventing rock fall.

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In order to purify the water quality of the close nature water area in which water containment has caused due to eutrophication, the artificial beach which used geotextile and natural zeolite is proposed. In the proposed method, the purification effect of natural zeolite is expected. Using permeable sheets and largesize sandbags made from geotextile filled up with natural zeolite or pea gravel, dikes are built on lakeside and an enclosure is made. And natural zeolite is laid inside the enclosure. Actual proof test conducted on lakeside of Lake Suwa was discussed, and the purification effect was confirmed based on results of field survey and water survey which were carried out periodically.

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Thrust forces can be generated at the bend of a pipeline due to internal water pressure. Commonly, the thrust force is resisted by passive resistance acting on the bend. A concrete block can be installed at the bend when the thrust force is larger than the passive resistance. However, the heavy concrete block can become a weak point during an earthquake, because the concrete block moves largely due to inertia force. Therefore, new methods for thrust restraint are required.
In this paper, new backfill methods for thrust restraint using geogrids are proposed. The new method comprised geogrids, installed in the passive area to improve the strength of the ground. In addition, gravel was used as backfill material in the passive area of the bend. In order to verify the effect of the proposed methods, lateral loading experiments were carried out using a model pipe with a diameter of 114 mm. The model pipe was backfilled with dry sand. After backfilling, the model pipe was laterally loaded at 0.5 mm/min. using a jack. The lateral resistance and lateral displacement acting on the model pipe were both measured. It was confirmed that the lateral resistance increased when using the proposed methods.
In addition, numerical analyses (DEM) were performed to assess the resistance mechanism of the proposed methods. It was concluded that the lateral resistance was generated by the tensile force of the geogrid of the vertical side below the rupture surface.

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At a bend in a pressure pipeline, thrust force is generated by the bending angle and internal pressure. Generally a concrete block is installed around a bend. However, the concrete block is a weak point for an earthquake. Therefore, in our previous study, the lightweight thrust restrain using geogrids was suggested. Lateral loading tests, large scale tests and numerical analysis were conducted, and it is verified that the proposed restraint was effective against thrust force. In this study, four shaking table tests were conducted in order to verify the dynamic behavior of the proposed restraint. From the result, in case of the proposed restraint, the movement of the bend was restrained. In addition, using gravel around the geogrid, the lateral movement was extremely small.

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In recent years, the embankment failure due to heavy rainfalls has frequently been taking place in Japan. Such embankment failures may often be induced by ground water seepage flow into the embankment, which in turn weakens the embankment itself involved with a complete loss of the soil suction. Accordingly, it is crucially important to avoid seepage flow into the embankment as well as the accumulation of rainfall behind the embankment. In this paper, a countermeasure named "watertight embankment using L-shaped geosynthetic drain" for protecting embankment against heavy rainfalls is proposed. A design method for the proposed technique is also described. A numerical simulation was carried out to examine the efficiency of the L-shaped geosynthetic drain. The numerical technique was evaluated based on the results of a seepage flow model test performed using a decomposed granite soil.

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"Watertight embankment using L-shaped geosynthetic" is a counter-measure to prevent the embankment failure in the event of heavy rainfall. The significance of this technique in reducing the water level in the embankment has been corroborated in seepage flow model test coupled with numerical simulation (Shibuya et al, 2008). In this paper, the engineering significance of "watertight embankment using L-shaped geosynthetic" is carefully examined in seepage flow test performed using a full-scale, and fully instrumented, embankment with 2.5m high. In the full-scale test, seepage characteristics as well as the deformation characteristics were measured, and also simulated numerically, for a couple of embankments with and without the L-shaped geosynthetic drain.

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In this study, we examined the overall stability of reinforced soil wall using the high strength geotextiles. At first, we carried out the centrifuge model tests to discuss the static stability of the wall. We verified that the reinforced soil wall improves in the stability by using the high strength geotextiles. Next, we carried out the shaking table tests to confirm the dynamic stability of the wall at the earthquake. As the results, we confirmed that the dynamic stability also improves by using the high strength geotextiles.

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Geosynthetic-Reinforced Soil Integral Bridge (GRS-IB) consists of an integral bridge comprising a girder unified to a pair of abutment and the backfill reinforced with geosynthetic-reinforcement layers connected to the back of the facing. It is shown that, cement-mixing the backfill zone immediately behind the abutment, GRS-IB becomes more stable against seismic load as well as cyclic displacements at the top of the abutment due to seasonal thermal deformation of the girder. Failure of GRS-IB is triggered by passive failure at the top of backfill, which results into a pushing out of the bottom of the abutment. It is effective for an increase in the stability of GRS-IB against both seismic and static loading to increase the passive resistance by cement-mixing a relevant zone of the backfill. The above was validated by performing a series of shaking table tests and static cyclic lateral loading tests on scaled models of GRS-IB.

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The effects of pile foundation on the stability of GRS integral bridge were investigated by performing the followings two model loading tests; a) lateral loading model wall tests that was simulated to the thermal lateral cyclic displacements at the top of the facing caused by seasonal thermal expansion and contraction of the bridge girder, and b) 1g shaking table tests. From the results of the lateral loading wall tests, the residual settlement of backfill due to the thermal cyclic displacement of the girder were fully alleviated by not only reinforcing the backfill but also fixing the lateral displacement of bottom of the facing by using of pile foundations. On the other hand, it was confirmed that the seismic stability of GRS integral bridge without pile foundation is sufficiently high. The seismic stability of GRS integral bridge does not increase when pile group with short piles were applied. It is necessary to apply group pile with short piles to ensure sufficiently high stability of GRS integral bridge.

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This paper presents a simple model that is aimed to be utilized as a measurement for predicting a surface stability of stone wall and also to evaluate an adhesion effect of vine developing along the surface of stone wall. The stability model of stone blocks pile is constructed based on Coulomb friction that acts between contacted blocks. Also, in this paper, pulling out test applied for trunk of vein is contained. It is expected that this amount of strength is affected by adhesion of trunks as well as the morphological properties of vine. This study leads to the new model for measuring the stability of geo-synthetic blocks pile. Parametric study based on the presented model indicates that the slope of surface of blocks pile have more effect on the stability comparing with the slant of wall surface itself. Furthermore, although the equivalent cohesion derived from the adhesion of vine remarkably affects the stability of sliding, it is concluded that it doesn't affect the stability of rotation.

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A reinforced soil wall which has double wall system is applied to construct a highway junction. The type of the reinforced soil wall is back-to-back walls in which maximum height is 10.2m and width is 6.5m. To construct integral structure and improve the procedure of construction, the geotextile is installed overall to two opposing wall facing. To assess the stability of the wall during and after construction work, the optical fiber sensor geotextile is applied to monitor the strain of geotextile. This paper reports the outline of construction and result of stability assessment based on the strain monitoring.

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Performance evaluation of railway retaining walls is conventionally conducted by visual inspection. This is because there is no quantified evaluation of the railway retaining walls in the present. Therefore, to evaluate the performance of the retaining walls, the performance evaluation test by using a small shaking devise was proposed with reference to the conventionally used percussion test for the performance evaluation of bridge piers. From results of the L-shaped retaining wall and full-scaled reinforced retaining wall model tests, a natural frequency of the retaining walls depends on earth pressure and bearing capacity. Consequently, the natural frequency of the rigid facing can be used for the performance evaluation of the L-shaped and reinforced retaining walls.

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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 facing battered walls. Design methodology with the modified method also discussed. Modified K-stiffness Method can result in substantial cost saving.

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A displacement evaluation method of geosynthetics reinforced soil retaining walls was developed based on results from series of shaking table model tests. Proposed method can simulate nonlinear increments of the wall displacement, which were observed from low acceleration level in the shaking table model tests, by considering deformations of subsoil layer and reinforced backfill. Accumulations of displacement increments after failure plane formation in backfill layer was also taken into account by considering effects of strain softening behaviors of backfill soils. Computed displacements using the proposed method corresponded well with the measured ones in the shaking table model tests while the effects of the pullout resistance should be considered for further improvements. The applicability of the proposed method to prototype scale retaining wall was also examined based on an analysis on the case history in the 1995 Hyogo ken Nanbu-earthquake, Japan.

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An application of a shallow width reinforced soil structure with pile foundation to a construction site of widening road embankment as the measure with respect to the site conditions that differed from the design ones, which were confirmed during the construction, is introduced in this paper. Background of the application of the structure to the site and conducted studies, such as 3D FEM analysis of tension stress occurring in the reinforcement at the bottom of the structure as well as the stability of the shallow width reinforced soil structure, for the application are described.

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In order to reduce deformation of ballasted tracks during large earthquakes, a new method to reinforce ballasted tracks with stacked geosynthetic bags that are filled with ballast was proposed. In this study, based on results of shaking table model tests, it is confirmed that the reinforced ballasted tracks have a sufficient resistance against a seismic wave that is larger than the so-called Level 2 earthquake motions. Moreover, it is confirmed that improved versions of the reinforced ballasted tracks, such as piling bags with inclination and driving in a reinforcing bar with inclination, have a sufficient seismic resistance under a condition of the wide tracks on which a larger inertia force acts during earthquakes.

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Countermeasures such as an increase in soil density, dissipation of pore water pressures leading to increased solidifaction and reductions in the level of the water table are commonly used techniques when embankments are constructed over ground which is subjected to liquefaction. On the other hand, it is effective to develop the economical reinforcing technique that can restrain the deformation of soil structure within allowable range. In this study degrees of deformation are examined when basal mattresses using high strength geosynthetic reinforcement are used on artificial ground which is subjected to liquefaction. And its behavior was simulated by 2-D FEM called ALID. Moreover, effect of reinforce due to high strength geosynthetic was evaluated under the various conditions. As a result, several conditions that the geosynthetic works efficiently to limit deformation of embankment on liquefied ground were pointed out.

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When a road embankment fails due to earthquake, it influences a road network by cutting off traffic at many places. Especially, the failure of trunk road must be prevented against any earthquakes. Therefore, it is necessary to develop an effective countermeasure which restrains a deformation of sliding of the road embankment due to earthquake. This paper proposes a new reinforcement method for existing embankment in which the upper part of embankment is reinforced by a geosynthetics. This method prevents the failure of road embankment by installing the geosynthetics in a shoulder of road embankment. At first, we carried out a full scale model test of the reinforcement method. To apply the reinforcement method to actual embankment, the procedure of construction for the reinforcement method is proposed. Secondary, we carried out a centrifuge model test to verify an effect of this reinforcement method against earthquake. As a result, it was confirmed that the embankment reinforced by the geosynthetics has high earthquake-resistance.

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A geomembrane installed at the bottom of the landfill is sometimes damaged because of local cyclic loads due to the installing process of the liner system, the process of dumping waste; eventually, leachate starts to leak to the ground. Leakage flow of leachate is affected with the configration of defects on geomembrane and the property of soil material used for the liner. The objective of this research is to visualize the leakage flow in the ground through the defects on geomembranes performing the leakage model test and to evaluate the relationship between the leakage rate and defect configuration.

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Hybrid Clay barrier (HCB) is the cement treated clay developed for the barrier system in coastal landfill sites with improved toughness by inclusion of fibrous materials while keeping sufficient impermeability. For the purpose to use HCB for tight anchorage of the geomembrane extended to the impervious ground, it is required to verify the interface transimissivity between HCB and geomembrane. Then a series of hydraulic conductivity tests were conducted on the HCB specimens in that pieces of geomembrane were inserted. The test results showed that the interface transimissivity was sufficiently small.

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As landfill cap covers with waterproof, gas permeability and construction durability, we have developed geocomposites (GCs) that nonwoven geotextiles are laminated to the both surfaces of the porous sheet and their basic performances have been investigated by laboratory and field tests. In this study, interface friction characteristics between soil and GCs, which indicate slope stability when GCs are practically applied as landfill cap cover, were evaluated by interface shear tests. Results show that interface shear strength and friction characteristics are increased by improving surface roughness and rigidity of nonwoven geotextiles. It was also found that compaction degree of soil affects interface shear strength between soil and GCs.

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Recently, the decrease in the hydraulics function by deterioration becomes a problem in hydraulics facilities for agriculture. Authors are developing the repairing method that uses the geomembrane for the joint in the reservoir made of concrete. Unlike a past method of facing, this repairing method constructs the geomembrane only in the joint part, and it excels by decreasing the use material in the economy. However, there is a problem in performance that prevents water leak because the boundary of the geomembrane and the structure is continuously resulted in the both ends of the joint part. To solve this problem, the seal material is arranged between surface of structure and geomembranes. This paper reports on outline and result of various performance evaluations that assume demanded performance, and result of verifying influence on geomembrane by difference of seal material.

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Working report submitted by The Japan Geosynthetics Technologies Association, JGTA (the working group of protection mat). Comparison work of various protection mats with light blocking effect for final waste disposal sites was conducted for two year and the problems at site was investigated by questionnaires for the members of JGTA. For the first year, each specimen with free load was exposed outdoor and the dimensional stability was evaluated. Most of the dimensional changes were proved to be less than 3%. For the second year, outdoor exposure test for the specimens with anticipated tensile force load of the actual waste site was conducted and the results showed the dimensional changes were drastically increased by the necking effect due to the longitudinal tensile load. The specimens tailored with high light stabilization formula only showed the better dimensional change of approximately 3% shrinkage in width. This value shows good correspondence with the actual field data obtained by the questionnaires. Hereafter, by means of the data from this experiment, we will establish the installation standard procedure and the construction method to prevent from the occurrences of the breakage of joint parts by strain, one of the major reasons of problems.

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The Eco-tube is a geosynthetic container developed for reusing low quality surplus soil such as dredged soil and improving its quality. The calculation assumed to be a saturated condition is done in a present design method, and the design method has not established it enough though the soil packed into the tube is expected to decrease water content ratio by drain and by evaporation from the surface of the bag and to enter the state of unsaturated. This paper describes the change in the saturation level of the soil by dehydration in the experiment and examines the piling design method of Eco-tube.

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Eco-tube method in a bag filled with sediment and dehydration, and the effective use of soil in the embankment construction materials. The construction of PWRI and developed by private companies, and this method has already been put to practical use. We ability to improve the construction, construction and the development of the system. We fill the river bottom sediment was used as construction materials because of the construction and construction system to report cases.

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