Geosynthetic-reinforced soil (GRS) integral bridge was developed to overcome several inherent serious problems with conventional type bridges typically comprising a simple-supported girder (or girders), RC abutments and approaches of unreinforced backfill: i.e. high construction/maintenance cost while bumps immediately behind the abutments; a low stability of the bearings and backfill against seismic and tsunami loads; massive abutment structures; needs for piles etc. A GRS integral bridge is constructed by constructing firstly a pair of GRS walls and an intermediate pier (or piers) if necessary; secondly lightly steel-reinforced full-height-rigid (FHR) facings by casting-in-place concrete on the wall face wrapped-around with the geogrid reinforcement; and finally a continuous girder with both ends integrated to the top of the FHR facings. The background of the development of GRS integral bridge is explained. The first four case histories, completed in 2012 and 2014, are reported.

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The girders of a great number of bridges were washed away and/or their approach fills were significantly eroded by the great tsunami of the 2011 Great East Japan Earthquake. Many of the bridges close to coastal lines are required to have high resistance against not only seismic load but also tsunami load. The geosynthetic-reinforced soil integral bridge (GRS-IB), has been developed and it has been verified that this new type bridge has high seismic stability. Results from small scale hydraulic model tests showed that the stability against tsunami load of GRS-IB is substantially higher than the conventional type bridge, having a girder supported by bearings. This high performance can be attributed to the fact that the girder, the abutments (i.e., facings) and the approach fills of GRS-IB are structurally integrated to each other and accordingly the resistance of the backfill against erosion is very high.

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This paper focuses on the numerical analysis of reinforced soil retaining walls using finite difference programme, FLAC. In the analysis, behaviour of soil-wall interaction, soil-reinforcement interaction has been considered. Dynamic loadings were applied in the form of sinusoidal waves at the base of the foundation soil. Analyses were conducted using different backfill conditions and loading conditions. The lateral displacement and earth pressure were analyzed in order to evaluate the effect of reinforcement on the retaining wall. Comparisons were made between unreinforced (conventional) and reinforced soil retaining wall. It was observed that the reinforcement affects the earth pressure as well as lateral displacement of the retaining wall significantly. Parametric studies were also performed to understand the mechanism of reinforced soil retaining wall. The results of this study reveal the advantages of reinforcement in order to reduce the damages caused by the earthquake.

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The authors have developed a specific geosynthetic for reduction of differential settlement, composed of woven textile sheet and lattice frame of mortar injected fabric hoses, providing high bending rigidity. To examine the reinforcement effect of this geosynthetic system, called the lattice-frame reinforced (LFR) sheet, a series of dynamic centrifugal model tests and finite element analyses were carried out. The results showed that the LFR sheet was capable of reducing differential settlement due to seismic liquefaction and effective to reduce horizontal deformation of liquefiable layer as well as the case in which the improved zone was totally set under the embankment.

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Over the world Terre Armée retaining walls have demonstrated impressively high performances after being submitted to very strong earthquakes. Sites investigations on 1,423 Terre Armée structures in Japan after the Great East Japan Earthquake of 2011 revealed that they present an impressive robustness and efficiency. Only 4 failures were observed, either caused by a lack of protection against scouring induced by the passage of the strong tsunami wave or caused by a general sliding. In Japan, the majority of Terre Armée retaining walls are built using High Adherence steel reinforcements. However, steel reinforcement cannot be used in marine areas or highly corrosive environments. For such aggressive environments synthetic reinforcements made of high tenacity fibers with a high stiffness are preferred. Our feedback on such structure exposed to earthquake motions is very positive, but not as well reference as for structures reinforced with steel. Nevertheless efforts are still needed to assess their performance under very strong motions. This paper introduces a numerical dynamic analysis to study Terre Armée retaining walls response to seismic loads. An overview of the modelling aspects will be given and the impacts of the reinforcement stiffness on the seismic performance will be shown. The paper will bring a relative comparison between the behavior of a wall reinforced with non-extensible reinforcements and a wall reinforced with relatively more extensible ones.

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This study focuses on accumulation of basic data on deformation and energy absorbing characteristics of geosynthetics (recycled tire chips and geogrid), which are used as liquefaction prevention materials for shallow foundations. Because tire chips have high compressibility, decrease of bearing capacity and excessive differential settlement of the foundation ground may arise. A new reinforcement method, using gravel mixed tire chips layer and layers of geogrid, was proposed to compensate for the inadequate bearing capacity and suppress differential settlement. In this study, the deformation and energy absorbing characteristics of tire chips and gravel mixed tire chips were made clear by performing direct shear test under dynamic loading using a large scale shearing device. Based on the results, it was found that the vibration-absorbing energy of tire chips decreases as the gravel fraction increases. Considering the pros and cons, we could arrive at the conclusion that the sample with 50% gravel mixture was the most effective. It was also confirmed that the rigidity of gravel mixed tire chips was improved through reinforcement by geogrid.

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This paper presents the response of unreinforced and geosynthetic reinforced dry sand under static and dynamic loading conditions. A large scale triaxial apparatus, capable of testing specimens having a maximum size of 300 mm in diameter and 600 mm in height was used for the study. Large specimen size used in this study allowed to overcome the boundary effects present in triaxial testing of reinforced sands. A series of triaxial compression tests were performed on unreinforced and reinforced sand specimens to investigate the effect of the quantity of geotextile reinforcement on the mechanical behavior of sand. A woven geotextile was used in layers to reinforce the sand. Number of reinforcing layers was varied from one to six in different tests. It was observed that under static conditions the peak shear strength and stiffness increased with the inclusion of geotextile layers. Reinforcement benefit ratio increased with the number of layers but decreased with the increase in confining pressure, indicating that the reinforcement layers are more effective at low confining pressures. Cyclic triaxial tests were carried out at 1 Hz frequency and 4 kN cyclic load. Reinforced specimens exhibited substantially higher dynamic moduli compared to the unreinforced sand.

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