Behaviour of model flexible piles under inclined loads in sand

The increasing use of fixed offshore platforms supported by pile foundations has encouraged the development of more rational methods of analysis of piles subjected combined axial and lateral loading. The combination of large lateral loads resulting from the action of wind, waves and currents in conjunction with vertical loads has created the need to analyze systems exposed to large inclined loads. -- The scope of this thesis is to study the pile-soil interaction of a vertical flexible pile under inclined loadings in dense sand. To study the interaction, model flexible piles of 25 mm, 42 mm and 60 mm diameters were jacked into sand with controlled density. These model piles were instrumented with load-cells and strain-gauge bridges to measure the bending moment distributions. The piles were tested under vertical, horizontal and inclined loads using a computerized data acquisition system. A suitable soil container and laboratory test frame were assembled to conduct the tests. -- The vertical load test results indicated that the value of the bearing capacity factor Nq was constant with depth and consistently smaller than that predicted by various existing theories. The results also indicated that the piles had a critical depth where the point resistance became constant with depth, at a pile diameter/depth ratio of about 20. -- Experimental p-y curves were compared with those proposed by Reese et al (1974), Matlock et al (1980), Scott (1980) and Parker (1970). The test data indicate that the semi-empirical methods underestimate the ultimate resistance near the pile head and overestimate it at depth. Computed response of piles under test conditions showed good agreement with the measured response. -- The ultimate load capacity under inclined load decreases with load inclination, with a rapid reduction for load inclinations between 45 and 90 degrees. Compared to a pile subjected to only lateral load, the vertical load on the pile increases the lateral deflections by about 4 to 15%, and the maximum moment in the pile section by about 8 to 16% for load inclinations from 60 to 30 degrees