Effects of interface connections on narrowed mechanically stabilized earth walls

In cases where the space available for the mechanically stabilized earth (MSE) walls is less than required, the “narrowed mechanically stabilized earth walls” are usually designed and constructed next to the existing stable slopes/walls. Although such walls have already been used and studied in some projects, the effects of different interface connections on complicated narrowed MSE walls are still not clear. The performance and mechanism of narrowed MSE walls still need further exploration, especially those with complex boundaries. Accordingly, two centrifuge model tests of narrowed MSE walls with thick soil mass above (like having an inside bench) were designed and carried out with full instrumentations. One of the models had mechanical interface connections to the boundary/stable slope and the other one without connections. The authors analyzed the experimental data including settlement, lateral displacement of the facing and earth pressure in the narrowed MSE walls and used limit equilibrium method to help locate critical failure planes. The results indicated that narrowed MSE walls had obvious differential settlement on crest, and around the inside bench the vertical earth pressure was observed to have concentrated and reduced distributions. The analyses indicated that the critical failure plane was bilinear, also different from conventional MSE walls. Mechanically connecting the narrowed MSE wall to the stable slope/wall is an efficient measure to help control the deformation and improve stability of the system, whereas the unconnected wall would experience larger displacement and was prone to collapse. Furthermore, the rupture of model reinforcements suggested that the extension of the upper reinforcements beyond the stable wall/slope face was not enough to ensure external stability.