The design of drilled displacement system piles using the cavity expansion theory

Drilled Displacement System (DDS) piles are an innovative technology for pile foundations. These DDS piles are created by rotary drilling with a simultaneous full displacement of the soil in a horizontal direction. The optimal design of DDS piles can be obtained in sandy soils and fine-grained soils that allow for a horizontal displacement, which causes an increase in the shaft’s resistance. This article deals with the use of Cavity Expansion Theory (CET) for a complex analysis of DDS piles. This method makes it possible to take into account the impact of the technology in pile design. A general view of the CET is presented and is described step by step for the solution of the present problem. The results of the calculations are compared and analysed with the results of three instrumented static load tests. The analyses include a comparison of the load-settlement curve as well as the load distribution over the pile’s length, which was measured using strain gauges. The results of the analyses show very good agreement between the calculations and the measurements. The difference between the calculated and measured load-settlement curves did not exceed a 10% degree of accuracy. The possibilities for the future use of CET are also discussed. J. Stacho: The design of drilled displacement system piles using the cavity expansion theory