Numerical study of a new belled wedge pile type under different loading modes

A new pile type with tapered pile body and an enlarged pile tip, referred herein as belled wedge pile, has been developed to improve both side resistance and tip resistance of pile when compared to the conventional tapered or belled cross-section piles. The new pile shape, due to wedge shape, can also reduce the development of negative skin friction when the surrounding soils are deforming under the applied surcharge loads. The construction method, quality assurance and quality control of the belled wedge piles are described. A numerical modelling technique using FLAC3D is used to perform numerical simulations to gain insight on the load carrying capacity and the load transfer behaviour of the belled wedge piles, in comparison to other pile shapes including the conventional belled piles, the tapered piles and uniform cross-section circular piles. The comparison study of the performance of these four pile shapes under compression loads, uplift loads and surcharge loads indicates that the belled wedge pile would possess the best load carrying capability and would be subjected to less downdrag among the four pile shapes evaluated. A parametric study using the established numerical modelling technique reveals the effects of various influence factors, such as the relative stiffness between the pile and the surrounding soils, taper angle, the diameter of the enlarged pile tip and stiffness ratio between the bearing soil and the overburden soil. In addition, performance of belled wedge pile within a group is evaluated in terms of the influence of pile position and pile spacing. The numerical parametric study results reveal that belled wedge pile is one of the cost-effective pile systems, which can improve vertical load carrying capacities under both compression and uplift loads and reduce the amount of negative skin friction developed due to the surcharge loads at the ground surface.

[1]  Mahmoud Ghazavi,et al.  Analysis of kinematic seismic response of tapered piles , 2007 .

[2]  Jayantha Kodikara,et al.  Axial Response of Tapered Piles in Cohesive Frictional Ground , 1993 .

[3]  D. C. Sego,et al.  Enlarged Base (Belled) Piles for Use in Ice or Ice-Rich Permafrost , 2003 .

[4]  M. Hesham El Naggar,et al.  Experimental study of axial behaviour of tapered piles , 1998 .

[5]  M. Hesham El Naggar,et al.  Compression testing and analysis of drilled concrete tapered piles in cohesive-frictional soil , 2008 .

[6]  Kyu-Ho Paik,et al.  Estimation of Axial Load Capacity for Bored Tapered Piles Using CPT Results in Sand , 2009 .

[7]  A. M. Rybnikov.  Experimental investigations of bearing capacity of bored-cast-in-place tapered piles , 1990 .

[8]  John Tristan Spronken.  Bearing capacity of tapered piles , 1998 .

[9]  K. Ilamparuthi,et al.  The influence of soil reinforcement on the uplift behaviour of belled piles embedded in sand , 2001 .

[10]  沢口 正俊.  Model tests in relation to a method to reduce negative skin friction by tapering a pile. , 1982 .

[11]  Robert Y. Liang,et al.  Numerical analysis of balled wedge pile groups under uplift load , 2010 .

[12]  Chen Zheng.  Research on computation methods of uplift capacity of enlarged base pile in layered soils , 2008 .

[13]  E I Robinsky,et al.  Effect of Shape and Volume on the Capacity of Model Piles in Sand , 1964 .

[14]  K. Ilamparuthi.  Predictions of the uplift response of model belled piles in geogrid-cell-reinforced sand , 2001 .

[15]  M. Hesham El Naggar,et al.  Uplift behaviour of tapered piles established from model tests , 2000 .

[16]  M. Hesham El Naggar,et al.  Evaluation of axial performance of tapered piles from centrifuge tests , 2000 .

[17]  N. R. Morgenstern,et al.  Simple shear creep tests on frozen soils , 1981 .

[18]  D. P. Ghosh,et al.  Vertical Vibration of Tapered Piles , 1986 .

[19]  Hu Qing-chun.  Study of characteristics of compression capacity and negative skin friction for belled wedge pile , 2011 .

[20]  Huang Shao-ming.  Full-scale field tests on uplift behavior of piles with enlarged base , 2007 .

[21]  Nabil F. Ismael,et al.  Behavior of Step Tapered Bored Piles in Sand under Static Lateral Loading , 2010 .