To increase bearing capacity of foundation, geosynthetic is laid beneath the foundation. In the previous research, the authors investigated the reinforcement mechanism by changing the length and the laying depth of the reinforcement (Nakai et al, 2009). In the present study, for getting more bearing capacity, reinforcing effect in the case that each edge of the reinforcement is fixed with the soil is investigated. For this purpose, 2D model tests and the corresponding non-linear finite element analysis are carried out. In these tests and simulation, the depth of the reinforcement is changed under two kinds of length of reinforcement. Reinforcing effects not only under concentric load but also under eccentric load are discussed. It is revealed that a significant increase of the bearing capacity is observed in the model tests when the reinforcement having mostly the same length as wide of the foundation or a slightly larger length is set up in the ground with an appropriate depth under both concentric and eccentric loads. The results of numerical simulation in which the stress-stain behavior of the soil and the frictional behavior between soil and reinforcement are properly taken into consideration shows a good agreement with the observed results.

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Geosynthetic mattress is different from Geosynthetic tubes as its horizontal dimension is much greater than the vertical one. When geosynthetic mattress is used for dyke construction, they are often laid on soft ground where large settlement may take place. In this paper, a two dimensional analysis of geosynthetic mattress resting on deformable foundation soil is presented. The foundation soil is assumed to be an elastic Winkler type represented by the modulus of subgrade reaction, K_f. The study shows that the smaller the modulus, the smaller the height of the geo-tube above the ground surface and the higher the tensile force in the geotextile or geomembrane given the other conditions the same. When the foundation soil has a modulus higher than 1000 kPa/m which is representative of soft clay, the foundation soil can be assumed to be rigid in the analysis. The results obtained from the method proposed in this paper are also compared with those from finite elements studies for verification. The differences between the solutions are also discussed.

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An experimental study of the strain behavior of high strength geogrids used to reinforce sandy soil under a 60 x 230 mm rectangular footing is conducted. The effect of two types of geogrids on the bearing capacity of the composite is investigated as well. Three layers of Netlon CE121 and Tensar SS2 geogrids were used. The first layer was positioned at 0.25B below the footing base while the third layer at a depth of B below the base where B is the footing width. The main aim of the study is to measure the strain and elongation occurring in the ribs of Tensar SS2 geogrid. The peak tensile strength of Tensar SS2 geogrid MD/XMD is 14.4/28.2 kN/m and it is 6.4 kN/m for Netlon CE121. TML strain gauges and other compatible accessories are used. The sand is statically loaded; the relative density was 71.8 % using a raining technique. It is found that the use of geogrids produces a bearing capacity ratio of reinforced to unreinforced sand of 2.35 and 2.9 for Netlon CE121 and Tensar SS2 respectively. The results revealed also that the measured strain and elongation in the ribs decrease as the depth of geogrid layers increases and as the horizontal distance from the footing centre increases as well. The strain in geogrid ribs practically diminishes at a depth of about the width of footing (B) and at a horizontal distance of about 2.33B from the centerline of footing. A maximum rib strain of about 0.0001 was measured corresponding to a maximum footing bearing stress of 363 kN/m².

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Over soft soil area the geosynthetic-reinforced and pile-supported subgrade was often used to reduce the post-construction settlement. But after operation it was found that the settlement sometimes was bigger than required. For settlement evaluation the stress concentration ratio between pile and soil is very important and the arching effect is often considered to solve this problem. There are some methods to analyze the sharing of fill load, but the dynamic train loads were often ignored. In this paper the finite element was used to simulate the stress concentration ratio during fill stage construction and dynamic load which were compared with the in-situ test. The results during fill stage also were compared with EBGEO and BS8006. They showed that the reliability of current methods is related to some factors including fill height, the stiffness ratio of pile and soil. There is a critical filling height whether the dynamic load decrease arching effect or not. According to FE results, the critical height is 3m. When the filling height is smaller than 3m, the stress concentration ratio should be re-evaluated by the reduction factor.

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This paper presents the experimental and numerical procedure for analyzing the shear load capacity of Geosynthetic Encased Stone Columns (GESC). Past studies have mainly focused to understand the vertical load capacity of GESC. However, these columns may also be subjected to significant amount of shear loading such as near the toe of high embankments and retaining walls, etc. The shear load capacity of the GESC depends on the diameter of the column, over burden pressure acting on the soil, geosynthetic strength properties etc. In order to analyze the shear load capacity of GESC laboratory tests were performed within a large shear box with GESC. The experimental results were validated using FLAC^3D software. The results showed that the geosynthetic encasement provides an additional confinement to the aggregates which leads to improvement in the performance of GESC.

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Asphalt pavements are layered structures designed to carry road traffic loads for a designed time period. The performance of this layered structure depends upon the bond interaction between the layers. Improper design due to the wrong interpretation of factors influencing the performance of pavements results in the development of distresses. The most common rehabilitation technique against these distresses is the placement of overlays. These overlays may suffer from a distress phenomenon called reflective cracking. The propagation of the cracks in the existing pavement onto and through the new overlay results in reflective cracking. Many interlayer systems are introduced to mitigate the effect of reflection cracking, out of which geosynthetic interlayer systems are gaining attention due to its ease of installation and cost effectiveness. The performance of the interlayer system depends upon the bonding with the existing layer as well as with the overlay. This paper focuses on the different type of bond test methods based on the stresses developed at the interface and to evaluate the factors that influence the bonding due to the presence of the geosynthetic interlayer in the performance of asphaltic pavement.

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In addition to vertical surcharges, geosynthetic-reinforced soil (GRS) structures have recently been used as barriers to resist lateral forces from natural disasters such as floods, tsunamis, rock falls, debris flows, and avalanches. The stability of such structures is often evaluated by conducting conventional external stability analyses with an assumption that the reinforced soil mass is a rigid body. However, this assumption contradicts the flexible nature of reinforced soil. In this study, finite element (FE) models of back-to-back GRS walls were developed to investigate the behavior of GRS barriers subjected to lateral loadings. The FE results indicate that GRS barriers subjected to lateral loadings fail internally. The failure model and the lateral bearing capacity depend on the aspect ratio (L/H: ratio of wall width to wall height) of GRS barriers. When 0.5 < L/H < 1.0, GRS barriers fail because of internal sliding along the soil–reinforcement interface at the side subjected to the lateral force and the active failure of the reinforced soil wedge at the opposite side. When L/H > 3.0, passive soil failure occurs within GRS barriers at the side subjected to the lateral force. As L/H increases, the lateral bearing capacity of GRS barriers increases to approximately three times the active lateral earth pressure at L/H = 0.7 to the passive lateral earth pressure at L/H = 3.0. In addition to the effect of L/H, the internal soil failure predicted by FE analyses suggests that the soil shear strength plays a major role in determining the lateral bearing capacity of GRS barriers. A hypothetical case study of a GRS barrier against a tsunami force is provided and an improved method is discussed.

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