Experimental study of axial behaviour of tapered piles

Abstract

Tapered piles, which have greater top cross sections than bottom ones, have the potential for substantial cost advantages for static loading conditions. However, tapered piles have not often been considered a design option because of the lack of design tools and knowledge about the behaviour of these piles. The objectives of this study are to explore and better understand the operating characteristics of the axial response of tapered piles. A large laboratory facility for testing model piles was developed. In this facility, the soil was contained in a steel soil chamber and pressurized using an air bladder to model the confining pressure. Three instrumented steel piles with different degrees of taper were used in this study. As expected, it was found that as the taper angle increased, the shaft resistance increased. It was found that the shaft resistance of the tapered pile was up to 40% larger than that of the cylindrical pile. The difference in the shaft resistance of the two types decreased for higher values of confining pressure. It was also found that the load distribution along the pile shaft for both pile types had the same pattern. However, this pattern varied as the confining pressure increased. Furthermore, the unit load transfer was significantly affected by the initial sand density for both pile types at low confining pressure, but as the confining pressure increased, this effect diminished. It is concluded that the tapered piles offer a larger resistance than the cylindrical piles. However, for longer piles, it is suggested that the taper be limited to the top length corresponding to 20 diameters.Key words: tapered piles, shaft friction, axial response, load transfer, model testing.

Field behaviour of screw micropiles subjected to axial loading in cohesive soils

“…There is no acceptable design guideline for this pile type or similar in the literature. Current literature suggests that pile shape (tapered versus straight shaft, Wei and El Naggar 1998), shaft roughness (smooth versus threaded shaft, Cuthbertson-Black 2001), and installation methods (drilled, driven or screwed-in, Salgado 2008) have significant impacts on the pile axial behaviour. Due to their unique characteristics, screw micropiles may perform differently from conventional piles.…”

A Comparative Study of Vertical and Batter Piles under Lateral Loading Conditions: A Review

“…Several investigators have given well-established theories for evaluating piles and pile groups behavior under different independent loading conditions viz. lateral, vertical and uplift loading [3][4], [8][9][10][11][12][13][14][15][16][17][18][19][20][21], [23][24][25][26][27], [29], [34][35][36], [42]. Various authors have conducted studies on combined lateral-uplift loading, lateral-vertical loading [18,41].…”

New design of a tapered bored pile For installation in structurally unstable soils

“…The issues of the development of negative friction forces in pile foundations have been addressed in works of national and foreign researchers: Dalmatov B.I., Lapshin F.K., Rossikhin Yu.V., Grigorian A.A., Zaretskii Yu.K., Morozov V.N., Broma Beng B., Fellenius B.H., Crawford C.B., Endo M., Bjerrum L., Johannessen I.J., Kerisel J., Lee C.J., Bolton M.D. [14,15] et al…”