2808
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
The problem which was showed concerning heat transient
transference in the soil is bi-dimensional (2D) and aximetric and
it can be solved analytically, for example, through finite
differences. However, Silva (2011) and Silva et al. (2012)
considering Hamilton's principle it is possible to determine the
variation of mechanical energy produced by the system,
assuming that the presented energy of the system is
conservative, that is, such energy cannot be created or
destroyed, simply transformed. Considering such principle,
Silva (2011) and Silva et al. (2012) applied the concept of work
done to the excavating process of a pile, achieving the
conclusion that the system of variable forces (
Fi)
produced by
the continuous flight auger equipment, showed in Figure 1,
applies to the boring device a movement from the initial
elevation (
ci
) to a final elevation (
cf
) through a path (
∆
xi
).
Accordingly, the work (
W
) done to excavate a pile is a pure
number defined by Silva (2011) as the pure product of such two
greatness,
Fi
e
∆
xi
given by:
= lim
∆
→
. ∆
=
.
(2)
Where:
W
= Work [J];
F
i
=
Force applied to the body [N];
∆x
i
=
body
path [m];
c
i
= initial elevation of the body [m];
c
f
= final elevation of the
body [m].
Similarly, he defined the work done by the friction and
adhesion present during the excavating process which
represents parts done by the non-conservative forces through
the same displacement, defined by:
= −lim
∆
→
. ∆
= −
.
(3)
Where:
W
c
=work done by non
-
conservative forces [J];
F
ci
=non
conservative forces applied to the body [N].
Figure 1. Boring system and forces.
Moreover according to Silva (2011), another type of energy
associated to the excavation of a pile is the potential energy
which basically depends on the position and system
configuration, in the case, the position of the helical device or of
the auger, is given by:
=
∆ = . .
−
(4)
where:
Wg
= work done by the gravity force [J];
Fg=Gravity force or
Weight Force
[N];
g
= gravity acceleration [m/s
2
];
m
= system mass
[kg];
(y
2
-
y
1
)
= variation of the geo
-
reference position [m].
Silva (2011) also considered that the conservation energy
principle summarized in Hamilton's principle is present in the
excavation of a pile. Similarly to the structural system dynamics
it can be simplified as mentioned by Clough and Penzien
(1975):
−
= 0
(5)
Where:
T
= total kinetic energy [J];
V
= potential energy including the
deformation energy of any external conservative force [J];
W
nc
= work
done by non
-
conservative forces that act in the system, including
cushion, friction and external forces [J].
Silva (2011) solved the problem considering Hamilton’s
principle represented by Equation 4, assuming that the total
thermal and sound energy of the system (
is equal to the
mechanical energy applied to the system or the work done by
external forces applied to the system (
W
R
), in the case, forces
applied to the helical device during the excavation of a pile
represented in Figure 1.
Then, knowing the torque applied to the helical device and the
lever arm, he measured the tangent force applied to the helical
device and knowing the angular and boring speed of the helical
device, the track can be determined and consequently, the work
of the tangent, which is the pure product of such force by the
displacement through depth. Finally, the total work done by the
external forces is the sum of the work done by the tangent force
to the helical device, plus the work done by the gravity force
and the work done by the downward force which is equal to the
mechanical energy applied to the helical device. Thereby, the
work is a pure greatness represented and defined by Silva
(2011) and Silva et al. (2012) as:
. .
.
. .
(6)
Where:
W
R
= work done or required energy to excavate a pile
[J]; Fi= force applied to the helical device [N];
m
hc
= mass of
the excating system [kg];
r
= radius of the CFA pile [m];
g
=
acceleration of gravity [m/s
2
];
z
b
= pile length [m]; Fdi=
downward force applied to the helical device [N];
m
= number
of turns of the helical device during excavation.
Silva (2011) and Silva et al. (2012) proved mathematically
that Equation 6 is consistent in terms of the physical point of
view and take to values close to the ones obtained by Van Impe
(1998) proposal, that considers in its approach mean values to
survey the required energy to excavate a pile type atlas.
3
SCCAP METHODOLOGY
In the traditional execution method, the pile depth is
previously set by the designer and is generally not modified
during the execution. However, in a profile with folded
structural geology, the current practice can take to mistakes,
mainly when the non-sampled soil, soil between boring tests
appear in the depression zone of the synclines, achieving low
resistance till the predicted design tip elevation.
To solve this problem, Silva (2011) proved that the work
done in each pile of the foundation piling executed by a fixed
process of the system machine/operator is proportional to the
pile bearing capacity. When put together in a data file, these
works make a population which fit in a normal probabilistic
distribution that allow the authors to establish acceptance
criteria related to the mean value and standard deviation of the
population from an extracted soil sample of the piling. The
methodology which is physically represented by Equation 6,
was introduced in the monitoring system of CFA piles, allowing
to quantify the work or required energy to excavate each pile of
the piling and, consequently to control the piling based on on
the required energy during the execution of the piling.
Therefore, the SCCAP routines introduce to the execution
monitoring software for CFA piles the excavation quality
