Field tests on single piles subjected to lateral and combined axial and lateral loads

Abstract

This thesis describes the results of full-scale instrumented field studies on laterally loaded piles embedded in a layered soil. The research centred around tests on (i) 350mm square reinforced concrete piles driven through a surface layer of granular fill into a deep deposit. The p-y response is also compared with the recommendations of the American Petroleum Institute (API). The research illustrates the importance of accurate interpretation of instrumentation data particularly in the case of piles that experience a reduction in flexural rigidity as the pile bending moment develops under increasing lateral load. The results emphasise the need to determine the structural response of the pile from first principles rather than the design approach customarily used by structural engineers. The load tests revealed that the presence of an axial load had no significant effect on the soil’s lateral response although axial load eccentricity should be given careful consideration. The degree of pile head restraint was also shown to have minimal effect on the lateral soil response. Although the p-y approach to lateral pile design has its limitations, these are shown to be second order effects - even in a strongly layered soil stratigraphy. Retesting the piles nineteen months after the initial tests revealed that soil ageing did not enhance lateral performance of the piles at the test site. The use of CPM and CPT in-situ testing techniques were shown to provide useful correlations with the measured pile response and with proper calibration, these techniques can be applied in the design of laterally loaded piles. From a practical standpoint, the benefit to be gained from the densification of a relatively shallow depth of the near surface soils may lead to considerable economies in the design of laterally loaded piles.