Analysis of reduced modulus action in U-section steel sheet piles

Recent concern surrounding the potential of RMA has provided an inclusion of strength and stiffness reduction factors in the forthcoming Eurocode 3 Part 5. The aims of this research are to increase the understanding of RMA. It aims to accurately model realistic loading conditions present in practical pile walls, accurately predict the amount of friction developed in the interlock of a steel sheet pile and develop a series of reduction factors dependant on the situation in which the retaining structure is used. This thesis presents tests carried out using miniature piles loaded for the first time in a manner that closely replicates that of a steel sheet pile (SSP) wall. Tests show that friction between piles can in certain circumstances largely prevent the development of RMA. Investigations prior to this research have found that interlock friction causes only mild increase in strength. The present investigation provided a more realistic simulation of ground conditions, adopting span to depth ratios similar to those found in real life pile walls. A numerical model simulating the behaviour of realistic pile wall conditions has been developed and validated using the results from scale piles. Use of the numerical model has demonstrated that restrained SSP walls with capping beams are unlikely to exhibit RMA. However, cofferdams propped at their tops and bottoms are likely to exhibit the full effects of RMA and should be strengthened as a result to ensure safe design. This numerical model has produced a series of curves that can be used to estimate the effects of RMA on strength and stiffness of U-section piles.