2807
Energy and Reliability Applied to Continuous Flight Augern Pilings - The SCCAP
Methodology
Énergie et fiabilité appliquées à l'excavation des pieux forés en continu - La méthodologie SCCAP
Medeiros Silva C.
Embre Empresa Brasileira de Engenharia e Fundações Ltda
Camapum de Carvalho J., Brasil Cavalcante A.L.
Dept. of Civil & Environmental Engineering, University of Brasilia
ABSTRACT: The SCCAP methodology was developed to control the execution of Continuous Flight Auger (CFA) type foundation
works. The methodology SCCAP was based in the law of energy conservation, which is one of the basic fundaments from classical
physics and quantifies the required energy, or developed work, to excavate each of the piles from any particular foundation site. It
proposes formulations, routines and criteria for pile acceptance based on the statistical characteristics of the population or from an
energy sample taken from this one. It has been incorporated into the monitoring and execution software from CFA piles machines,
and it allows for local corrections on procedures and excavation depth at each executed pile from the site. Consequently it enhances
the reliability and mitigates involved risks to the geotechnical job. The SCCAP methodology has been validated through the
assessment that the necessary energy to excavate a particular pile is related to its bearing capacity, when the excavation process is
monitored.
RÉSUMÉ : La méthodologie SCCAP a été développée pour contrôler l'exécution des pieux forés en continu (CFA). La méthode
SCCAP est fondée sur la loi de conservation de l'énergie, qui est un des fondements de la physique classique et qui quantifie l'énergie
requise - ou le travail à fournir - pour excaver chacun des pieux dans n'importe quel sol de fondation. Elle propose des formulations,
des procédures et des critères pour définir la conformité des pieux, basés sur les caractéristiques statistiques de la population ou sur un
échantillon d’énergie pris dans celle-ci. Cette méthode a été incorporée au logiciel de suivi et d'exécution des machines foreuses de
pieux CFA et elle permet d’effectuer des corrections locales sur les procédures et la profondeur d'excavation de chaque pieu. Par
conséquent, elle améliore la fiabilité et réduit les risques encourus lors du travail d’excavation. La méthode SCCAP a été validée par
le fait que l'énergie nécessaire pour excaver un pieu particulier est en relation directe avec sa capacité portante, lorsque le processus
d'excavation est contrôlé par monitoring.
KEYWORDS: Energy, Methodology SCCAP, Continuous Flight Auger (CFA) and Reliability.
1 INTRODUCTION
Safety analyses in Foundation Engineering when are done,
are generally restricted to design and are deterministic, that is,
in theory certainty of the parameters involved in dimensioning
exists, accepting as precise the calculating methodology
adopted. However, it is known that the greatest source of
variability in Foundation Engineering is the geological-
geotechnical formation., which affects the performance of the
soil-foundation system that is strongly determined by the
stratum variability through the soil profile as a whole.
In pilings the aim is to reach the design assumptions in terms
of load capacity and deformability for them to be verified
during execution. Consequentially, Foundation Engineering
look for techniques that assure the good performance of the
foundations concerning resistance and/or deformability. The
ideal is to adopt procedures and routines during design phases
especially during the quality control of the execution to identify
the need of intervention during execution.
In this context, the SCCAP Methodology is presented for the
control and uniformity of the bored pilings, especially for the
continuous flight auger pile which is based on the interpretation
of the necessary energy or the work done during the excavation
of a pile. Such methodology was developed from the
understanding of the force system of the boring equipment and
the application of the universal energy conservation principle
which when applied to the excavation process of a pile allows
the enrgy quantification necessary for a pile. As a consequence
of the confirmation that the bearing capacity is related to the
necessary energy to excavate a pile, it was possible to
incorporate the statistical concepts as SCCAP routines allowing
to control the excavation process quality during the piling
excavation.
For the confirmation of the SCCAP Methodology efficiency
load tests and comparisons were used with predictions based on
SPT tests. The developed methodology was presented in details
in Silva (2011) and according to the author can be extended to
any type of bored or other rotating excavations such as the ones
for tunnels, only if it is possible to identify the force system to
quantify the spent energy in the process.
The SCCAP proposed routines do not substitute the
geotechnical engineer judgment but it can help him in the
identification and mitigation of involved risks in any type of
piling, especially for the ones that do don't have controls based
on scientific concepts, as the excavated pilings.
1 ENERGY AS BASE FOR THE CONTROL OF PILINGS
Silva (2011) and Silva et al. (2012) presented the
construction of the methodological structure that is the basis of
a thesis which says that the control of mechanical excavations,
especially for bored piles done by the determination of the
required energy during the pile excavation consists of an
element for technological control capable to offer a greater
security and less risks to the constructions that use them.
Coming from some hypothesis, Silva (2011) proposed an
analytical formulation to quantify the total transferred energy by
the system to the soil, which is obtained by the volumetric
integration as a function of the soil temperature. Consequently
the total energy of the system is obtained by:
=
, , −
, , 0
(1)
Where:
E
st
= total energy of the system [J];
ρ
s
= soil density [kg m
-3
];
C
ps
= specific soil heat [J m
-3 0
C
-1
];
V
= refering to volume [m
3
].
