Study of Active Earth Pressure behind a Vertical Retaining Wall Subjected to Rotation about the Base

Retaining structures are often restrained in the case of cantilever in situ embedded walls, anchor, strutted, and bridge abutments and thus are subjected to rotation. The earth pressure distribution and point of application are affected by the mode of movement. This paper deals with an experimental investigation on the magnitude and stress distribution behind a rigid retaining wall subjected to rotation about its base with the incorporation of a nonintrusive image analysis method such as particle image velocimetry (PIV) to track the soil movement via the full-field displacement vectors. It enables us to observe the rupture propagation and establish the shape of the potential failure surface. The active stage is reached at a wall rotation of 10x10-4 rad. The nonlinear active pressure distribution along the depth of a wall is obtained, confirming the existence of the arching effect. A nonplanar failure surface observed from PIV analysis also indicates that the failure surface essentially does not develop up to the base of the wall even after application of sufficient wall rotation. With this knowledge, an analytical model using limit equilibrium has been developed by assuming a curvilinear failure surface as seen from the PIV results and including the wall yielding and arching phenomenon in it. The predicted earth pressure and its distribution establish a good agreement with the observed data. The predicted failure surface giving rise to maximum active force shows a close match with obtained shear strain contours. The estimated slip plane angles show higher values than the other existing theories. A detailed parametric study indicates that the shape of the arch does not incur appreciable changes in earth pressure for delta/phi<0.67. The size of the failure wedge shrinks with the increase of phi and becomes nonlinear as the wall friction strengthens. The point of application is also significantly influenced by the soil and wall parameters.