Note: Descriptions are shown in the official language in which they were submitted.
CA 02815739 2013-04-24
Method for the underground installation of a pipe
The invention relates to a method for the underground
installation of a pipe, which is suitable in particular
for pipeline construction.
In the known HDD ("Horizontal Directional Drilling")
method, a pilot hole is created from a start side to a
target side by way of drill rods. Once the target side
has been reached, what is known as a reamer is mounted
on the drill head or the drill bit. This reamer is then
pulled, rotating, to the start side, with a suitable
drilling fluid (for example bentonite) emerging at the
tip of the rods, said drilling fluid both detaching the
soil that is present and supporting the drilled hole
that is produced against collapse. The reamer passes
are repeated with increasingly large reamers until the
drilled hole has been produced with the desired size.
In this case, the established drilled-hole diameter is
considerably larger than the diameter of the product
pipe run to be subsequently installed. The considerable
excess diameter is necessary in order to reduce the
frictional forces during the installation process. The
lubricating effect of a bentonite suspension on the one
hand and the floating of the product pipe run with low
casing friction against the wall of the drilled hole on
the other hand require an ample distance from the pipe
wall to the wall of the drilled hole.
The success of the HDD method depends on particular
geological conditions and the ultimate size of the
drilled hole. In the case of a product pipe having a
diameter of 56" (1.42 m), a drilled hole having a
diameter of 1.80 m is produced. In the event of
failure, the drilled hole has to be abandoned.
The method described in EP 1 802 844 Bl ("easy long")
is a microtunneling method for pipeline construction,
in which steel support pipes are advanced in the
CA 02815739 2013-04-24
- 2 -
microtunneling method from a start side to a target
side. Once the support pipe run has reached the target
side, the product pipe run provided in the region of
the target side (that is to say the pipe) is connected
to the support pipe run and is pulled or pushed into
the drilled hole created with support. This method is
reliable in any geology, since the wall of the drilled
hole cannot collapse on account of the support pipes,
but is slower and more expensive than the HDD method on
account of the advancement of the microtunnel. The
borehole produced has a slightly larger diameter than
the installed product pipe. Less soil is excavated and
less bentonite is used than in the HDD method. The
"easy long" method is thus more ecological than the HDD
method.
It is the object of the invention to create a method
for the underground installation of a pipe, which can
be carried out at a similar speed to the HDD method but
is fundamentally more reliable and ecological.
This object is achieved by a method for the underground
installation of a pipe having the features of claim 1.
Advantageous embodiments of the invention can be found
in the dependent claims.
In the method according to the invention, a pipe having
a given diameter is installed underground between a
start side and a target side. First - in a similar way
to the HDD method - a pilot hole is created, wherein a
drill head (preferably having a drill bit) is advanced
from the start side to the target side by means of
drill rods. In order to drive the drill rods, use can
be made of what is known as an HDD rig, as is known
from the HDD method and is constructed at the start
side. By way of the HDD rig, the drill rods can be
rotated, advanced in the direction of the target side
CA 02815739 2013-04-24
- 3 -
and, if required, moved back in the direction of the
start side.
The next method steps take place optionally,
specifically when the pilot hole is not intended to be
widened to the desired final diameter (which is at
least as large as the diameter of the pipe) in a single
step. In these optional method steps, the pilot hole is
enlarged in one or more steps, by means of a reamer
that is moved from the target side to the start side
using the drill rods, to a diameter of the drilled hole
which is smaller than the final diameter of the drilled
hole, as is explained in more detail below.
Once the pilot hole has been produced or after the
optional method steps have been carried out, the drill
rods extend as far as the target side. A reamer
configured for the final diameter of the drilled hole
is now mounted at the target side, for example at the
drill head or at the end of the drill rods. The pipe
provided at the target side beforehand or in parallel
with the previous method steps is coupled to the reamer
or to the end of the drill rods or the drill head. To
this end, use is made of a coupling device between the
reamer and the end of the pipe. Subsequently, the
reamer and the pipe are moved from the target side to
the start side. In the process, the reamer enlarges the
drilled hole to the final diameter and the pipe comes
to rest in the drilled hole.
Reamers are also used in the HDD method. With the aid
of a reamer, soil which is not too hard can be cleared
away. Preferably, the reamer is rotated while it is
being moved from the target side to the start side
using the drill rods. Furthermore, the procedure is
generally made considerably easier if a drilling fluid
is introduced into the drilled hole, for example via
nozzles arranged on the reamer, while the reamer is
CA 02815739 2013-04-24
- 4 -
being moved from the target side to the start side. The
drilling fluid preferably includes a bentonite
suspension.
If, during the optional method steps, the pilot hole is
enlarged to a drilled-hole diameter which is still less
than the final diameter, the previously indicated
intermediate steps can be carried out. To this end, a
reamer is pulled from the target side to the start side
by means of the drill rods, wherein the reamer enlarges
the pilot hole. This reamer creates a drilled-hole
diameter which is less than the final diameter. If the
drilled hole needs to be enlarged further in a stepwise
manner, for example on account of the size of the final
diameter or the nature of the soil, the drilled rods
are advanced to the target side again and then a larger
reamer is pulled from the target side to the start side
by means of the drill rods, wherein the larger reamer
further enlarges the previously created hole. If
appropriate, this step is repeated once or more than
once with increasingly large reamers. Finally, the
drilled rods are advanced to the target side again in
order to take up the starting position which is
necessary for the previously explained steps for
producing the final diameter of the drilled hole and
introducing the pipe into the drilled hole.
In order to enlarge the reamer, a larger reamer is
preferably mounted each time. In principle, it is also
conceivable to use an adjustable reamer which can if
necessary be adjusted to such an extent that it is
configured for the final diameter. If a reamer is
configured for a particular diameter, this does not
necessarily mean that it itself has to have this
diameter. On account of the effect of the drilling
fluid, the reamer may also be smaller.
= CA 02815739 2013-04-24
- 5 -
As a rule, the drilled hole will have a smaller
diameter than the pipe prior to the employment of the
reamer configured for the final diameter. However,
applications in which the drilled hole is widened to
such an extent that its diameter is already larger
beforehand are also conceivable in principle.
In preferred embodiments of the method according to the
invention, the pipe is advanced from the target side to
the start side using a pushing apparatus arranged at
the target side. Pushing apparatuses that are suitable
for such a purpose (for example "pipe thrusters") are
known and can in principle exert large pushing forces,
for example when a hydraulic apparatus acts on the
outer wall of the prepared pipe by means of a sheath-
like collar. If the pipe is strong under tension and
can be moved relatively easily through the drilled
hole, it is also conceivable, however, to pull the pipe
from the target side to the start side with the aid of
the drill rods.
If a pushing apparatus is used, the moving of the
reamer configured for the final diameter to the start
side using the drill rods and the activity of the
pushing apparatus are preferably synchronized with one
another such that the movements take place as far as
possible at the same basic speeds and do not have to be
adapted to one another by forces transmitted from the
pipe and from the drill rods.
The coupling device advantageously has a rotary
coupling and also a device for acting on the end of the
pipe. The pipe is not intended to rotate about its
longitudinal axis as it is being introduced into the
ground, while the reamer rotates. The rotary coupling
serves for compensation.
= . CA 02815739 2013-04-24
- 6 -
Since, during the installation of the pipe, the
distance between the reamer and the end of the pipe is
small, the drilled hole does not as a rule collapse.
However, depending on the local geology, a support
casing may if necessary be carried along in the
intermediate space between the reamer and the end of
the pipe while the reamer and the pipe are being moved
from the target side to the start side, said support
casing preventing the drilled hole from collapsing. In
this case, the diameter of the support casing is
matched to the diameter of the pipe, i.e. for example
is the same size or somewhat larger.
As already mentioned, the pipe is prepared prior to
being moved into the drilled hole at the target side.
To this end it may already be fully prepared, for
example welded together from individual pipes and if
necessary provided with corrosion protection, and also
checked. The pipe may be mounted for example on a
roller track on the target side. The pipe may be used
for transporting media, but may also be in the form of
an empty pipe, for example for the subsequent pulling
in of cables.
The method according to the invention, which may be
known as the HDJ ("Horizontal Directional Jacking")
method, combines the advantages of the HDD method and
of the "easy long" method. The drilled-hole diameter
needs to be only slightly larger than the diameter of
the pipe to be installed, since as a rule a lubricating
film (for example composed of bentonite suspension)
suffices to reduce the casing friction. The HDJ method
is more economical than the "easy long" method and more
reliable and ecological than the HDD method.
The invention is explained in more detail in the
following text by way of exemplary embodiments. In the
drawings:
= CA 02815739 2013-04-24
- 7 -
Figure 1 shows a schematic longitudinal section
through a construction site at which the
method according to the invention is used, in
a first phase,
Figure 2 shows a schematic longitudinal section
through the construction site according to
figure 1 in a second phase,
Figure 3 shows a schematic longitudinal section
through the construction site according to
figure 1 in a third phase, and
15 Figure 4 shows a schematic longitudinal section
through an embodiment of a reamer which is
connected to drill rods and to which the end
of a pipe is coupled by means of a coupling
device, during the construction phase
according to figure 3.
Figures 1 to 3 illustrate in schematic longitudinal
section various phases during the execution of an
exemplary embodiment for a method for the underground
installation of a pipe.
The arrangement of the construction site can be seen in
figure 1. A pipe is intended to be laid under a body of
water 6 between a start side 2 and a target side 4. An
HDD rig 10 is constructed and anchored on the start
side 2. HDD rigs are used in HDD methods and are
familiar to a person skilled in the art. With the aid
of an HDD rig, drilled rods can be rotated and advanced
and also pulled back under force exertion. In the
exemplary embodiment, a pilot hole 16 which leads to
the target side 4 and sets the subsequent course of the
pipe to be installed is created with the aid of the HDD
rig 10, drilled rods 12 driven thereby and a drill head
CA 02815739 2013-04-24
-8--
14 mounted at the end of the drill rods 12. The drill
head 14 is controllable such that the pilot bore 16 can
be guided along a curved and previously defined path.
In the view shown in figure 1, the drill head 14 has
just arrived underneath the body of water 6.
While the pilot hole 16 is being created, the pipe to
be installed, which is designated 20, is prepared on
the target side 4. In the exemplary embodiment, the
pipe 20 is welded together from steel pipe sections,
the region of the weld seams is provided with corrosion
protection, and a leak-tightness check is carried out.
A liquid or gaseous medium can subsequently be
transported through the pipe 20. Other configurations,
for example in the form of an empty pipe or a pipe made
of some other material, are likewise conceivable.
As can be seen in figure 1, the pipe 20 is mounted on a
roller track 22. Furthermore, what is known as a pipe
thruster has already been moved into position. The pipe
thruster has a pipe clamping device 24 which acts on
the outer side of the pipe 20 via a type of collar and
in the process can exert large forces. The pipe
clamping device 24 is connected to an anchoring means
28, schematically shown in figure 1, via advancing
cylinders 26. By actuating the advancing cylinders 26,
the pipe 20 can subsequently be advanced in the
direction of the start side 2.
Figure 2 illustrates a state in which the pilot hole 16
has been finished and after the drill head 14 has
arrived at the target side 4. The drill head 14 is then
removed from the drill rods 12 and a reamer 30 is
mounted instead at the front end of the drill rods 12.
The reamer 30 is subsequently connected to the end of
the pipe 20 by means of a coupling device. The reamer
30 and the coupling device are illustrated in figure 4
in an enlarged view (wherein the coupling device is
= = CA 02815739 2013-04-24
- 9 -
configured in a slightly different manner than in
figures 1 to 3).
Reamers such as the reamer 30 are known in the prior
art from HDD methods. The reamer 30 has a larger
diameter than the drill head 14. In the exemplary
embodiment, the reamer 30 is fitted on the end of the
drill rods 12 instead of the drill head 14. However, it
is also conceivable for the drill head 14 to be left on
the drill rods 12 and for the reamer 30 to be fastened
to the drill head 14. With the aid of an attack side
32, which is configured in a conical manner in the
exemplary embodiment, the reamer 30 can widen the
drilled hole, when it is rotated with the aid of the
drill rods 12 and pulled toward the start side 2. In
the process, a drilling fluid, a bentonite suspension
in the exemplary embodiment, emerges on the attack side
32, said drilling fluid making it easier to widen the
drilled hole, strengthening the wall of the drilled
hole and simultaneously acting as a lubricating film.
The reamer 30 is connected to the pipe 20 via the
coupling device. As figure 4 shows, this coupling
device has a joint part 34, a rotary coupling 36, a
further joint part 38 and also a strain-relief means
40. The strain-relief means 40 is mounted on the end of
the pipe 20 and is subsequently removed when the pipe
has 20 has been finally laid.
Figure 2 therefore shows the state of the construction
site immediately after the mounting of the reamer 30
and the coupling device 34, 36, 38, 40. The reamer 30
is now pulled in the direction of the start side 2 via
the drilled rods 12 with the aid of the HDD rig 10,
while the pipe thruster is set into action and
simultaneously advances the pipe 20 with the aid of the
advancing cylinders 26. In the exemplary embodiment,
the movements of the drill rods 12 and the advancing
= CA 02815739 2013-04-24
- 10 -
cylinders 26 are synchronized in order to avoid
unnecessary tensile or compressive forces in the drill
rods 12 and the pipe 20. Figure 3 shows a state in
which the reamer 30 has arrived under the body of water
6. The region of the reamer 30 having the end of the
pipe 20 is, as already explained, illustrated in figure
4 in an enlarged view.
While the reamer 30 is being rotated by the drill rods
12 and the drilling fluid is emerging on the attack
side 32 of the reamer 30, the reamer 30 widens the
drilled hole 50 which is generally designated 50. As a
result, the pilot hole 16, the wall 52 of which has a
first diameter, is enlarged in the exemplary embodiment
to a drilled hole having a wall 54 which already has
the desired final diameter. The reamer acts in
particular at a transition zone 56. The rotary coupling
36 ensures that the reamer 30 can rotate without
problems, while the pipe 20 executes no rotary
movement. The drilling fluid also passes into an
intermediate space 58 between the pipe 20 and the wall
54 of the drilled hole 50 and forms there a type of
lubricating film which considerably reduces the
frictional forces between the pipe 20 and the wall 54
of the drilled hole 50.
The reamer 30 is pulled back as far as the start side
2, while the pipe 20 is advanced, such that the pipe 20
comes to rest along the desired route in the final
state.
It is assumed in the exemplary embodiment that the
soil, in particular after the drilling fluid has acted,
is so firm that the drilled hole 50 does not collapse
in the region between the reamer 30 and the strain-
relief means 40 of the pipe 20. If the soil is
problematic, a support casing can be arranged in this
zone, the outside diameter of said support casing
CA 02815739 2013-04-24
- 11 -
corresponding to the final diameter of the drilled hole
50 or having a slightly smaller diameter. The support
casing prevents the drilled hole 50 from collapsing in
this critical region and is moved together with the
pipe 20 toward the start side 2.
In the exemplary embodiment, the pilot hole 16 is
widened in one step with the aid of the reamer 30 to
the final diameter (wall 54) necessary for the pipe 20.
Depending on the nature of the soil and the diameter of
the pipe to be introduced, however, intermediate steps
can also be carried out. To this end, first of all a
reamer having a smaller diameter than that of the
reamer 30 is mounted after the pilot hole 16 has been
produced and is pulled without the pipe 20 toward the
start side 2, with the drilled hole 50 being widened.
Subsequently, the drilled rods 12 are moved back to the
target side 4 with the aid of the HDD rig 10. There, if
required, a larger reamer can be attached, said larger
reamer still being smaller than the reamer 30, in order
to carry out a further intermediate step for widening
the drilled hole 50. If necessary, this process is
repeated once again or more than once, until finally
the reamer 30, which creates the desired final diameter
of the drilled hole 50, can be mounted.
