The problem that occurs during open-ended steel pipe pile installation is that soil enters the pipe and develops frictional resistance that further prevents soil intrusion, causing plugging and increased piling resistance. The steel pipe pile with tapered tip (tapered tip pile) restrains plugging and piling resistance. To apply the tapered tip pile as end-supported piles, it is essential to clarify the bearing capacity mechanism suitable for tapered shapes. In addition, it is not possible to apply the bearing capacity mechanism of the flat tip pile (straight pile). The purpose of this paper is to reveal the piling performance and the bearing capacity by experiment and to propose the bearing capacity model based on the mechanism in a fully plugged mode. Experiments were conducted on model-tapered pipe piles installed in sands with different soil conditions to investigate the effects of the pile shape on piling performance and bearing capacity. Extending the combination theory of Prandtl and cavity expansion, bearing capacity model and formula incorporating shape parameters were derived. Theoretical values were good agreement with the experimental results.
Various Geogrids are widely utilized and contribute the improvement of stability of embankment. Material properties and pullout characteristics are investigated respectively. However the properties of those geogrids are rarely compared each other and little is known about the effects of different material properties on earth reinforcement. It has been recognized that pullout resistance is important when we examine a stability of reinforced embankment. So pull-out tests were conducted to investigate the effects of difference of material properties of geogrids on pullout characteristics. Special attention was directed to look at the effects of the shape, yield resistance and stiffness of geogrids in this research.
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