مهندسی عمران شریف (May 2024)
Investigation on the behavior of two-tiered MSE walls as bridge abutments
Abstract
Mechanically stabilized earth (MSE) walls are commonly used as bridge abutments to support bridge deck loads. In this type of abutment, the use of a tiered configuration can play a prominent role in reducing induced horizontal stress, reducing lateral deformation, and, consequently, improving the performance of bridge abutments. Despite the importance of this issue, the influence of various factors on the performance of tiered MSE abutments under deck loads is not yet fully understood. Therefore, by simulating a bridge deck on a tiered MSE abutment in the form of a strip footing, the effects of the reinforcement type, the connection type of the deck to the abutment, and the deck location were investigated. For this purpose, three two-tiered mechanically stabilized earth walls (T-TMSEWs) were constructed using three different reinforcements and then loaded with strip footings at three different distances from the wall crest. By preventing and allowing the footings to tilt, the influence of the degree of footing freedom was also examined as the third variable. Particle image velocimetry showed that the use of a two-tiered configuration in MSE abutments and a decrease in the soil–reinforcement interaction and stiffness changed the slip surface geometry and prevented the development of deep slip surfaces in the lower tier. It was found that although the decrease in reinforcement stiffness and its interaction with soil decreased the bearing capacity of the strip footings on two-tiered MSE abutments, they also reduced the lateral pressure induced in T-TMSEWs by strip footing. Also, allowing the footing to tilt was found to be an effective solution for minimizing the deformation of the backfill surface and the induced lateral pressure. Moreover, a comparison of the results with analytical methods showed that the construction of MSE abutments in a two-tiered configuration reduced the lateral pressure in the upper tier. This became more noticeable with a decrease in the soil–reinforcement interaction and reinforcement tensile stiffness and an increase in the distance from the footing to the wall crest.
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