The Influence of Thin Clay Layers on the Design and Performance of a Flexible Cantilever Retaining Wall

This case study presents the methods that were used successfully to redesign and monitor the performance of a flexible cantilever retaining wall, incorporating an in situ support berm, at a site where thin, weak clay layers were detected in the foundation during construction. A potential mode of failure termed berm-block sliding , where the retaining wall pushes out the entire support berm as a block along the clay layers, governed the design analysis. Evidence of presheared planes within the clay layers required that the design shear strength parameters be based on residual values. The clay had a significant cohesion component which was utilized in the design along with an observational method towards construction and post-construction behavior. The observational approach included a comprehensive instrumentation and monitoring program and the development of a remedial stabilization contingency plan to be implemented if necessary. This design methodology resulted in significant cost savings