Hydraulic and earth engineering – Foundation – Columnar structure
Reexamination Certificate
2001-04-10
2002-11-12
Shackelford, Heather (Department: 3673)
Hydraulic and earth engineering
Foundation
Columnar structure
C405S233000, C405S240000, C405S256000, C175S323000
Reexamination Certificate
active
06478512
ABSTRACT:
The present invention relates to an auger type machine for making bored piles.
More precisely, the invention relates to a machine capable both of boring a cylindrical excavation in the ground and of filling said excavation with grout or concrete so as to end up by defining a cast pile in the excavated ground.
BACKGROUND OF THE INVENTION
Accompanying
FIG. 1
shows an auger type boring machine for making cast piles. The machine comprises a platform
10
which is preferably mounted on crawler tracks
12
and which has a guide mast
14
hinged thereto, which mast is vertical when in the working position. The mast
14
carries vertical slideways
16
on one of its faces to guide a carriage
18
in translation. The carriage
18
carries a rotary drive head
20
which co-operates with a hollow auger
22
constituted by a hollow core
24
and at least one helical blade
26
. The rotary drive head
20
serves to rotate the auger
22
, thereby causing it to dig into the ground by screw action, and thus making the borehole. Since the auger
22
is hollow, once the borehole has been made, it is possible to inject grout or concrete into it so as to constitute the pile progressively as the auger is extracted from the borehole.
For reasons both of structure and of acceptable bulk for a moving machine, the height of the mast
14
and the height H of the auger
22
are always restricted to a value of no more than about 20 meters (m). Unfortunately, on some sites, it is desirable to be able to bore boreholes and to cast piles to a depth of about 25 m.
In order to enable such piles to be made, proposals have already been put forward to add an extender tube
28
to the top portion of the auger
22
, which tube has subsequently become known as a “Kelly”. A Kelly
28
of length
h
is secured to move in rotation and translation with the top end of the auger, and the top end
28
b
of the Kelly
28
is connected via a rotary joint
30
to a concrete feed pipe
32
. It will be understood that this makes it possible to bore a pile to a depth equal to H+h, which amounts to about 25 m. It should be understood that the rotary drive head
20
can co-operate equally well with the core
24
of the auger and with the Kelly
28
.
A major drawback of such a system lies in the way in which the concrete is introduced into the borehole in order to make the pile. The concrete flows out directly from the open bottom end
24
a
of the hollow core of the auger. Moving this bottom end
24
a
by means of the carriage
18
is difficult and there is a risk of the bottom end being pulled out above the fill of concrete while the tool is being withdrawn. Such a discontinuity is accompanied by a risk of the terrain in which the borehole has been drilled caving in locally and severely harming the mechanical strength of the pile made in this way.
French patent No. 2 566 813 in the name of Soletanche discloses an auger type boring machine which makes it possible to avoid the above-mentioned drawback. That hollow-core auger is fitted with a tube that is slidably mounted in the hollow core of the auger, said tube usually being referred to as a “dip” tube. This tube is in a retracted position inside the auger while the borehole is being bored and its bottom end is moved so as to project from the bottom end of the auger while the auger is being raised so as to enable concrete to be injected into the borehole. That technique makes it possible to ensure that the pile made is of good quality and in particular to ensure that concrete injection is continuous over the full height of the borehole.
It will be understood that there exists a real need for an auger type boring machine for making cast piles which makes it possible both to make piles to greater depth and to obtain piles of good quality, and in particular piles that have good continuity in their concrete structure.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide such a boring machine that satisfies those two requirements simultaneously.
According to the invention, this object is achieved by a machine for making bored piles, the machine comprising:
vertical guide means;
a rotary drive head that is movable relative to said vertical guide means;
an auger having a hollow core and at least one helical blade, said core having open top and bottom ends;
an extender tube whose bottom end is secured to the top end of the core of the auger, said rotary drive head co-operating with said extender tube to rotate the assembly constituted by the auger and the extender tube;
a dip tube slidably mounted in the hollow core of the auger and in the extender tube, the dip tube having a top end connected to a concrete feed pipe;
actuator-forming means having a first end constrained in translation relative to the top end of said extender tube and a second end constrained in translation relative to the top end of said dip tube; and
means for controlling the actuator-forming means to modify the position of the bottom end of said dip tube relative to the position of the bottom end of the core of said auger.
It will be understood that because the hollow core of the auger is extended by an extender tube or Kelly, it is possible to make piles down to a depth which is extended substantially by the length of the Kelly. It can also be seen that installing a moving dip tube in the assembly constituted by the hollow core of the auger and the Kelly it is possible to benefit from all of the advantages of a dip tube concerning control over injecting concrete or grout into the borehole so as to obtain a pile.
Preferably, said actuator forming means comprise an annular body surrounding the dip tube and constrained in translation relative to the top end of the extender tube, and an annular moving portion surrounding the dip tube and constrained in translation relative to the top end of the dip tube.
It will be understood that because of the presence of the annular actuator, it is possible to control the position of the bottom end of the dip tube accurately relative to the bottom end of the hollow core of the auger, thus making it possible to obtain high quality injection of concrete into the borehole as the auger and the Kelly are raised progressively, and in spite of the presence of the Kelly. In addition, using an annular actuator surrounding the dip tube makes it possible to avoid creating any axial offset between the dip tube and the assembly comprised by the Kelly and the auger.
REFERENCES:
patent: 3300988 (1967-01-01), Phrares et al.
patent: 3303656 (1967-02-01), Landau
patent: 3470701 (1969-10-01), Turzillo
patent: 3485052 (1969-12-01), Turzillo
patent: 3604214 (1971-09-01), Turzillo
patent: 3690109 (1972-09-01), Turzillo
patent: 3707848 (1973-01-01), Chelminski
patent: 3886754 (1975-06-01), Turzillo
patent: 4269544 (1981-05-01), Rusche
patent: 4433943 (1984-02-01), Pao Chen
patent: 5256003 (1993-10-01), Ito et al.
patent: 5919005 (1999-07-01), Rupiper
patent: 6238142 (2001-05-01), Harsch
patent: 37 38 420 (1987-11-01), None
patent: 2 566 813 (1986-01-01), None
patent: 2566813 (1986-01-01), None
patent: 2070668 (1981-09-01), None
Compagnie du Sol
Lee Jong-Suk
Shackelford Heather
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