Behavior of Back-to-Back MSE Walls: Interaction Analysis Using Finite Element Modeling

Back-to-back mechanically stabilized earth (BBMSE) wall is a specific case of modern earth retention technique, where the design of the wall system depends on the spacing between two walls as the limited space behind the wall controls the interaction between them as well as their stability and lateral earth pressure distribution along the wall height (H). In view of the above, this study comprehensively analyzes geogrid reinforced BBMSE walls using finite element numerical modeling to examine the stability and interaction behavior by varying the distance between two interacting MSE walls and investigating the possible mode of failure using the strength reduction method. To attain the aim set for the present study, the width to height (W/H) ratio of the wall is varied, and its consequent effect on the lateral earth pressure (sigma(h)/gamma H) of the wall is investigated. Based on the findings, a correction factor for active earth pressure coefficient (i.e., K*) is proposed, facilitating geotechnicians to design a safer and optimized structure with due consideration of the lateral earth pressure on the wall. The factor of safety (FOS) of the wall is evaluated, which indicates that FOS is significantly increased when W/H is reduced. It is also noted that the maximum tension mobilized in the geogrid layers (T-m(ax)) reduces when the two interacting MSE walls are in close proximity. This study also analyzes the critical angle of the failure wedge (beta), which significantly reduces with the decreasing D/H ratio of the wall (where D is the distance between two interacting MSE walls). A nonlinear regression analysis is implemented to obtain a generalized equation for predicting the normalized distance of failure peak from the wall facing (x/H) for various W/H ratios along the wall height. This study recommends an optimum overlap length of 0.3H to utilize the reinforced infill and save space during the BBMSE wall construction.