Field tests using an instrumented model pipe pile in sand

Recent design methods for displacement piles have been developed based on the results of field tests using highly instrumented, closed-ended model piles which were able to measure the radial effective stress at a number of locations along the pile shaft. The measured σ' _r were then directly related to in-situ soil properties such as CPT cone resistance. Many design methods have been extended to consider the shaft resistance developed along open-ended (pipe) piles by adopting various assumptions with regard to differences between the radial stress regimes set up by closed and open-ended piles. However, no comparable measurements of σ'r from pipe piles were available to assess the validity of these assumptions. This paper presents the results of radial stress measurements made on an instrumented open-ended pile during installation into loose sand. These measurements are used to investigate the validity of some of the assumptions underlying a number of popular design methods.