Performance of a Rigid Retaining Wall with Relief Shelves

Earth pressure on a retaining wall decides the sectional dimensions of the wall, and there have been several attempts in the literature to reduce the earth pressures on the retaining walls, by using techniques such as lightweight backfill and placement of compressible inclusions at the wall-backfill interface, to name a few. A retaining wall with pressure relief shelves, though discussed for several decades, is one of the least practiced techniques to reduce the earth pressure on retaining walls, mainly because of its complex behavior and lack of distinct provisions. One such wall was constructed in the populated area in Hyderabad, India, however, it failed after a few years. This failure has motivated the authors to study the behavior of these walls and to understand the associated mechanism involved in earth pressure reduction, as well as what caused the failure in the previously mentioned wall. The work reported in this study presents static force analysis and numerical analysis of rigid nonyielding retaining wall retaining a dry cohesionless backfill with pressure relief shelves performed using three-dimensional numerical analysis. A parametric study is conducted to understand the influence of width and position of relief shelves on the contact pressure below the base slab, surface settlement profile of backfill, deflection of relief shelves, and reduction in lateral earth pressure. The present study reveals that relief shelves can reduce lateral thrust on the wall up to 23%, compared to that of a retaining wall without a relief shelf. The static force analysis suggests that the width of relief shelves should be increased from top to bottom of the wall, for achieving maximum reduction of earth pressure. Moreover, it is also noted that maximum allowable width of the relief shelf at any height of the wall is a function of the width of the relief shelf lying above it.