Enhancement of reinforced soil wall performance under dynamic loading

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Reinforced soils have been widely used in a variety of applications because of their satisfactory performance and cost effectiveness. A number of investigations to determine the seismic deformation modes of reinforced soil walls with conventional horizontal inclusions have already been conducted, but only limited investigations with the partial inclusion of vertical elements have been conducted, and then they did not consider the performance of reinforced soil walls under dynamic loading. This research presents a new concept of soil reinforcement using vertical fortification designed to connect layers of conventional horizontal reinforcement together. For this proposed system, as with conventional reinforced soil, the selected granular material is compacted over the horizontal reinforcement up to a given height, and then subsequent layers of horizontal reinforcement are laid down. Afterwards, reinforcements are inserted vertically or at an inclined angle, as per the design requirements. Each layer is then tied to another so that it acts as one integrated system, reducing the total force at the back of the facing panels. This concept is modelled numerically using PLAXIS 2D version 9.0 using the Kobe earthquake loading. The convincing results from this numerical analysis encouraged me to conduct an experimental program that included shake table tests. The selections of materials were then tested to determine which materials were readily available on the market. Four reduced scale physical models, with and without vertical reinforcement, with angled reinforcement towards the facing and against the facing were tested on a shake table under stepped-up sinusoidal acceleration input. The results of the four models tested were then compared to evaluate the performance enhancement of a soil wall with vertical reinforcement. The results showed that the wall with vertical reinforcement improved its performance under dynamic loading remarkably. Finite element models based on the same parameters used in the shake table experiments and with a PLAXIS 2D program were developed, from which the numerical outcomes generated similar patterns of better performance when vertical fortification was included. Those results are matched against the experimental outcomes, and the results show a reasonable agreement between the measured and calculated displacements, backfill surface settlements and accelerations, albeit there were some discrepancies. These slight dissimilarities could be the result of implementing, to some extent, different physical properties in the numerical model and their variability within the measured data. An array of parametric studies with varying design parameters was also carried out, with the results indicating that the magnitude of dynamic response increases with a decreasing angle of friction and the extent of dynamic response decrease with an increasing Young’s modulus. It is also found that the vertical reinforcement with very close spacing (less than three times the spacing of horizontal reinforcement), adds no extra benefit for the wall system. According to the findings of this study, the proposed inclusion of vertical components to reinforced soil walls enhances the stability of the walls compare to the conventional reinforced soil systems under earthquake loading. The vertical components increase the integrity of the reinforced wall and create blocking actions, which reduce deformations at both facing wall and backfill surface. These outcomes point out the potential benefits of inserting vertical elements into a conventional soil reinforcement system under dynamic loads.
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