A set of crosswise-loaded flexible piles was tested in binder stabilised top sand layers embedded in lightly bonded residual soil. Slope indicators were used to measure horizontal displacements in free-headed flexible piles during all loading stages. The geometry of the cement stabilised top sand layer surrounding the piles varied from about 2 to 4 times the pile diameter and 0.1 to 0.3 times the pile length. Experimental outcomes present an important enhancement in the performance of the flexible piles under transverse load when a cement stabilised sand layer replaces top residual soil, increasing bearing capacity and reducing maximum horizontal displacements at any given working load. At large horizontal displacements (close to failure), a linear relation is observed between the lateral load and the total lateral area compressing the natural soil around the pile. This evidence helps identifying the pile-soil interaction mechanism and provides sound normalization for test results, both considered necessary steps towards the development of a design concept for predicting lateral pile response
