Predicting driving transferred energy: case studies of steel piles

ABSTRACT

This paper application of a method developed in Brazil for predicting driving transferred energy. The method was recently developed in Brazil and was used in short piles in 2019. In this more recent paper, it was sought to extend the application of the method to long piles (Pile length > 30 m) in soils of different characteristics. It is based on the pile measurements of permanent and elastic displacements during driving and calibration of the site-specific λ coefficient. The article validates the methodology in a case study of two sites with 159 dynamic tests of steel-driven piles in the cities of Santos (SP) and Itaguaí (RJ). Through calibration of λ, the energy predictions showed a good correlation to those obtained from the dynamic tests. There is an additional contribution to the original author’s analysis – increasing the previous testing database – about the correlation between λ and the pile length, as the study includes piles from 36 to 60 m in length – a range that was not included during the author’s first method evaluation. Its major advantage is allowing effective energy estimations in non‑instrumented piles as it is not practical to monitor every single pile of a construction driving site to assess the transferred energy. The presented method is useful in the practice of driven foundation and its quality control.

KEYWORDS:

• Effective energy
• efficiency
• steel piles
• dynamic load test
• PDA
• transferred energy
• deep foundation
• pile driving

List of symbols

$s$	=	set. Permanent (plastic) displacement per blow
$K$	=	full elastic displacement due to the blow
W	=	hammer weight
h	=	hammer drop height
R	=	pile-soil’s static resistance
W_p	=	pile weigth
C	=	coefficient for “additional losses” or elastic deformation account
e	=	impact efficiency
$\mu$	=	blow restitution coefficient
$K_{sp}$	=	coefficient of resistance reduction due to viscou /dynamic effects in soil.
$\eta$	=	driving system efficiency / impact efficiency
D	=	maximum pile displacement after blow (sum s+K)
C3	=	quake. Elastic displacement of the soil below pile tip.
$\lambda$	=	lambda. Site-specific adjustment coefficient (Querelli’s Method)
L	=	pile length
E	=	dynamic elastic modulus
A	=	pile cross-sectional area
$E_{ef}$	=	effective transferred energy to the pile (analogous to EMX)
$1/{\lambda }^2$	=	ratio - angular coefficient of the effective energy equation
$R^2$	=	coefficient of determination (linear regression; statistics)
${\lambda }_{ind}$	=	individualized lambda for each test record
$N_{60}$	=	normalized SPT N-value
EMX	=	maximum transferred energy to the pile calculated by the dynamic load test (analogous to ‘η.W.h’)
CV	=	coefficient of variation (statistics)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Some or all experimental data that support the findings of this study may be available from the corresponding author upon request.