مهندسی عمران شریف (Aug 2024)
Analytical and experimental study on two-tiered MSE walls
Abstract
A pseudo-static coefficient is required for pseudo-static analysis of mechanically stabilized earth (MSE) walls, but there are no clear criteria for its selection. The current study assessed the horizontal pseudo-static coefficient (kh) for MSE walls by considering the effects of a tiered configuration and reinforcement type. For this purpose, by selecting two reinforcement types (steel strip and geogrid), six two-tiered MSE walls with three different offset distances and two integrated MSE walls (without tier) were prepared and then were shaken using shaking table tests to determine the geometry of the slip surfaces and the force distribution along the reinforcements at the failure stage. The physical models then were simulated using the limit-equilibrium horizontal slice method to estimate the value of kh required to establish slip surfaces and reinforcement forces similar to those observed in shaking table tests. Because the equivalent pseudo-static coefficients obtained were the corresponding to failure stage, they were considered as the upper bound values. The analytical models used a new formulation of the horizontal slice method (HSM) based on the slip surfaces observed in the shaking table tests. This formulation made it possible to determine the distribution of kh along the wall height as a function of the reinforcement type, offset distance, and PGA. It was found that, as the offset distance increased, the pseudo-static coefficient required for the upper and lower halves of the tiered wall models increased and decreased, respectively. This was observed in both types of reinforcement, but was more prominent in walls reinforced with metal strips. Moreover, the distribution of kh along the wall height showed that a lower pseudo-static coefficient was required for the upper layers of the integrated walls, but the reverse was true when using a tiered configuration. This change in the trend of the kh distribution, which was due to the increase in the dimensions of wedge failure in the lower half and a decrease in dimensions in the upper half of the wall required a larger coefficient in the upper layers of the tiered walls.
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