• Journal of the Korean GEO-environmental Society
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• v.14 no.7
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• pp.13-18
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• 2013

As a new foundation treatment technology, long-short pile composite's design theory is still in primary phase, and there are no explicit settlement calculation methods in active codes. So it is necessary to study the working mechanism and the methods of settlement calculation. In this paper, the mechanics of long-short pile composite foundation are fully discussed. Meanwhile, based on the shear deformation method, the Mylonakis & Gazetas models about mutual action between two piles and the one between pile and soil are introduced, Considering the performance of cushion, the flexible factors of mutual actions are provided. Then the settlement calculation of long-short pile composite foundation which can consider the mutual actions between pile, soil and cap is deduced, and the correlated program is also developed. Finally, an engineering example is discussed with the method. A comparison shows that calculated results and measured data from a field test pile are in a good agreement, indicating that the presented approach is feasible and applicable in engineering practice.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.341-352
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• 2023

Long-short pile composite foundations bear both vertical and horizontal loads in many engineering applications. This study used indoor model tests to determine the horizontal bearing mechanism of a composite foundation with long and short piles under horizontal loads. A custom experimental device was developed to prevent excessive eccentricity of the vertical loading device caused by the horizontal displacement. ABAQUS software was used to analyze the influence of the load size and cushion thickness on the horizontal bearing mechanism. The results reveal that a large vertical load leads to soil densification and increases the horizontal bearing capacity of the composite foundation. The magnitude of the horizontal displacement of the pile and the horizontal load borne by the pile are related to the piles' positions. Due to different pile lengths, the long piles exhibit long pile effects and experience bending deformation, whereas the short piles rotate around a point (0.2 L from the pile bottom) as the horizontal load increases. Selecting a larger cushion thickness significantly improves the horizontal load sharing capacity of the soil and reduces the horizontal displacement of the pile top.