Print Email Facebook Twitter Experimental modelling of lateral loads on large diameter mono-pile foundations in sand Title Experimental modelling of lateral loads on large diameter mono-pile foundations in sand Author Alderlieste, E.A. Contributor Van Tol, A.F. (mentor) Broere, W. (mentor) Dijkstra, J. (mentor) Heeres, O. (mentor) Faculty Civil Engineering and Geosciences Department Geotechnology Programme Geo-Engineering Date 2011-04-01 Abstract The last years several offshore wind farms have been completed. Such farms typically consist of a few dozen wind turbines. The majority of these wind turbines is founded on mono-piles with a diameter of 4–5 m and is designed according to standards that use the p-y method for lateral loading conditions. However, this p-y method is not validated for such diameter piles. Full-scale field tests and model pile tests with properly scaled stress conditions subjected to lateral loads are scarce. This Thesis investigates the effect of a diameter increase on the lateral bearing capacity of 2.2 m and 4.4 m diameter mono-piles in dry sand. Static displacement controlled and one-way cyclic force controlled model pile load tests were performed using the Delft University of Technology geotechnical centrifuge. Results show that the smaller 2.2 m diameter pile has a lower secant and tangent soil- pile stiffness when compared to the 4.4 m diameter pile. In all cases the tangent stiffness is about 50% higher than the secant stiffness. Also, a force acting higher above soil surface yields a lower initial system stiffness. Results furthermore show that an increase in pile diameter with a constant slenderness or L/D-ratio, relative density Id and load excentricity e, leads to a significant increase in static lateral capacity. The secant and tangent stiffness also significantly increase with increasing diameter. The accumulation of lateral pile displacements as function of the number of applied one-way cyclic lateral loads has been investigated using 500 force controlled cycles. For an increasing number of load cycles the pile head displacements increase whilst the rate of accumulation decreases. However, additional loading cycles, up to e.g. 100000, are recommended. For static loading conditions experimental results have been compared to the default API formulation for laterally loaded piles. This default formulation shows a significant overestimation of the initial stiffness. However, after incorporating a stress dependent secant stiffness E50, which has been derived from triaxial compression tests on model sand, good agreement is found between the experimental results and the modified API formulation for pile displacements <0.1D. For displacements of about 0.05D the modified p-y method underestimates the lateral bearing capacity of the 4.4 m diameter pile by up to 25. Further research with loading conditions that mimic field loading conditions and a sample with a higher initial density are recommended. It is also recommended to im- prove the current set-up using better load control and a larger strongbox and to perform additional model pile tests on saturated samples. Subject lateral loadsp-y method To reference this document use: http://resolver.tudelft.nl/uuid:2dc40e3f-d333-4d23-ad4f-24187aeae03d Part of collection Student theses Document type master thesis Rights (c) 2011 Alderlieste, E.A. Files PDF msc_thesis_e_alderlieste.pdf 7.42 MB Close viewer /islandora/object/uuid:2dc40e3f-d333-4d23-ad4f-24187aeae03d/datastream/OBJ/view