[0001] The invention primarily relates to a method for fitting a grouted anchor in order
to anchor revetment walls, buildings, bank protection works, quay walls and the like.
[0002] A method of this type is known. With this method, a pipe which has a leave-in-place
foot is pushed, screwed or struck into the ground, a tension member is worked into
the pipe, the pipe is filled with grout, a screw cap is screwed onto the top of the
pipe, the pipe is pulled back step by step and, at the same time, grout under high
pressure (about 20 bar) is introduced via the pipe into the ground. The pipe is thus
removed and the tension member with grouted anchor and the leave-in-place foot remain
behind.
[0003] A significant disadvantage of this method is that introduction of the pipe into the
ground and its subsequent withdrawal are time-consuming.
[0004] The aim of the invention is to overcome this disadvantage and to provide a method
by means of which a grouted anchor can be fitted rapidly and at relatively low cost.
To this end, the method according to the invention comprises the following steps:
- introducing into the ground a solid or hollow anchor rod made of high-grade steel,
- via a cavity in the rod, a pipe fitted around the rod and/or one or more small tubes
which are fixed to the outside of the rod and at least one of which terminates in
the vicinity of the lower end of the rod, feeding liquid into the hole around the
rod while the rod is introduced into the ground,
- feeding grout via said rod cavity, pipe and/or small tubes as soon as the lower end
of the rod has reached the desired level from the top of the grout body,
- introducing grout under a pressure of at least 15 bar into the ground via said small
tubes, pipe and/or cavity,
- bringing the lower end of the rod to the desired depth while the grout is fed in under
high pressure and
- allowing the grout to set.
[0005] Before introducing grout under a pressure of at least 15 bar into the ground, it
is preferable that the lower end of the rod is brought to the desired depth while
grout is fed in under normal pressure and the rod is then withdrawn from the ground
over the desired length of the grout body.
[0006] The rod can have a drill bit at its lower end and can be introduced into the ground
by pushing and turning.
[0007] The drill bit can be provided with a propeller blade which has 0.2 to 5 screw turns.
In order to join anchor rod and drill bit, the rod can be provided with helically
arranged ridges and the drill bit can be screwed to the lower end of the rod with
the aid of a nut welded to the bit. It is possible to drive the rod into the ground,
in which case a number of small tubes or hoses for supplying liquid and grout have
their outlets at various heights above the lower end of the rod.
[0008] The invention also relates to a grouted anchor consisting of a solid or hollow rod
which, at least at the lower end, is provided with a screw thread or helically arranged
ridges.
[0009] According to the invention, a drill bit is screwed onto the lower end of the rod.
[0010] The element connecting the drill bit to the rod is preferably a nut.
[0011] In the case of a drill bit which is simple to produce, said bit comprises one or
more triangular plates which on one side are connected to the connecting element.
[0012] A core rod can be fixed to the connecting element, such as the nut, and a propeller
blade which has 0.2 to 5 screw turns and a minimum diameter which is greater than
the diameter of the connecting element can be located around said core rod.
[0013] The diameter of the propeller blade preferably tapers.
[0014] It is also possible to arrange one or more small tubes along the anchor rod, said
small tubes being fixed to the anchor rod and at least one of said tubes terminating
in the vicinity of the lower end of the anchor rod or in the drill bit.
[0015] Very long rods can be composed of sections which are coupled to one another by means
of couplings.
[0016] In order to supply the grout, a pipe can be arranged around the tension member, which
pipe is fixed to the drill bit, for example by making slots in the lower end of the
pipe, into which slots the top edge of the drill bit projects. The end section of
the pipe intended for adhesion of grout will be roughened to provide better adhesion.
[0017] In yet another variant, a small tube is arranged at least around the lowermost section
of the tension member, which tube has its outlet in the vicinity of the drill bit,
a pipe section enclosing the lower end of the tension member and said small tube over
the length of the grout body to be introduced and a force-transmitting medium (for
example grout) being introduced into the gap between the pipe section and the tension
member.
[0018] The upper end of said pipe section can be connected to a pipe arranged around the
tension member. The closed lower end of said pipe can be connected to a union to which
the small tube positioned in the gap between pipe section and tension member is connected.
[0019] The invention will now be explained in more detail with reference to the figures.
Figure 1 shows a perspective view of the lowermost section of a tension member to
be introduced into the ground.
Figures 2, 3 and 4 show a longitudinal section of the drilled hole in various stages
of fitting of the grouted anchor.
Figures 5 and 6 show views of two parts of a particular embodiment of a drill bit,
which parts can be joined to one another.
Figure 7 shows a perspective view of the lowermost section of one variant of a tension
member to be introduced into the ground.
Figure 8 shows a view of a tension anchor according to Figure 7, of substantial length.
Figure 9 shows a view of the lowermost section of yet another variant of a tension
member.
[0020] The tension member 1 shown in Figure 1 is made of high-grade steel onto which ridges
2 have been rolled which run in a helical pattern with respect to one another. A drill
bit 3 is composed of a triangular steel plate onto which a nut 4 has been welded.
Said nut is screwed onto the lower end of the tension member 1. A small tube 5 runs
along the entire rod 1 and is fixed to the rod with the aid of clamps 6 and has its
outlet in the vicinity of the drill bit 3.
[0021] Figure 2 shows the first stage of production, in which the rod 1 is introduced into
the ground by pushing and turning and, during this operation, water or bore flushing
liquid is introduced into the hole via the tube 5.
[0022] In the stage shown in Figure 3, the rod has reached the desired depth and during
the last part of drilling, instead of water, grout has been supplied via the tube
5. Said grout is indicated by 7. The lowermost section of the rod with drill bit now
extends into a firm layer of ground, such as a layer of sand.
[0023] The rod is then withdrawn from the ground over the desired length of the grout body
(see section shown in broken lines in Figure 3) and grout under high pressure (greater
than 15 bar, preferably about 20 bar) is then injected into the borehole via the tube
5 and, at the same time, the lower end of the rod is pushed back down to the desired
depth.
[0024] The grout under high pressure displaces ground around the bottom of the drilled hole
and the grout body 8 forms from grout and any soil (sand) mixed therewith, which grout
body 8 is allowed to set.
[0025] It would be possible to introduce the rod, which can be solid or hollow, into the
ground by driving, and there is a possibility of using five different tubes, which
have their outlets at different heights above the lower end of the rod, instead of
a single tube.
[0026] A somewhat longer rod will be composed of sections which are coupled to one another
by means of couplings.
[0027] Diverse embodiments of the drill bit are possible. Figure 5 shows an essentially
triangular plate 10 which is welded to a nut 11. An incision 12 has been cut out at
the lower end of the triangular plate and a rectangular opening 13 has also been cut
into the plate. The triangular plate 14 according to Figure 6 has an incision comprising
a tapering section 15, a section 16 which has a width smaller than the thickness of
the plate 10 and a section 17 which has a width equal to the thickness of the plate
10. Two projections 18 protrude from the top surface of the plate 14. Said projections
have a sloping face on the outside.
[0028] The plate 14 is slid over the plate 10 into a position perpendicular to the plate
10 - as soon as the section 16 of the incision in the plate 14 is opposite the opening
13 in the plate 10, the plate 14 is clicked home with respect to the plate 10, the
projections 18 protruding into the nut 11. The resulting union between the plates
10 and 14 is strong without welding work having to be carried out. As can be seen
from the dash-and-dot lines between Figures 5 and 6, the height of the section 16
of the incision is somewhat smaller than the height of the opening 13, that is to
say the walls of the tapering section 15 end beneath the top edge of the opening 13.
As a result, and as a consequence of the fact that the sloping faces of the projections
18 lead to the opening 15 becoming narrower when they are slid with respect to the
bottom inside rim of the nut 11, a firm clap joint is produced between the plates
10 and 14.
[0029] In another possible embodiment, a core rod, around which a half to two turn(s) of
a propeller blade are fixed, is welded to the nut 4. The diameter of the propeller
blade can taper.
[0030] Because the grout sets fairly rapidly, said grout is able to exert such great forces
on the tube 5, for example during introduction of the grout body, that said tube 5,
possibly having clamps 6, is destroyed by torsion during rotation of the tension member
1. It is possible that the grout introduced already starts to set within a few minutes
of its introduction. In order to prevent this problem as shown in Figures 7 and 8
and also to obtain better corrosion resistance of the tension member, a pipe 19 can
be arranged, instead of the tube 5, around the tension member 1, which pipe 19 is
able to withstand at least a pressure of 25 bar and is preferably made of plastic
instead of metal. By making slots 22 in the pipe, for example at the lower end of
the pipe 19, in the vicinity of the drill bit 3, so that the pipe 19 is fitted over
a plate of the drill bit 3, it is possible to transmit the moment of torsion, acting
on the pipe 19 and caused by the setting grout, to the drill bit and thus to the tension
member 1. Other methods are also possible for connecting the pipe 19 to the drill
bit 3 or tension member 1, so that the pipe 19 also turns as the tension member 1
rotates.
[0031] The pipe 19 has an internal diameter such that sufficient gap remains between the
pipe 19 and the nut 4 to allow the requisite liquid and/or grout to pass.
[0032] After the anchor has been prepared, grout is present between the pipe 19 and the
tension member 1, as a result of which the tension member 1 is also protected against
corrosion, which is important in connection with the alkaline medium of the grout
in which the tension member 1 is encased.
[0033] Preferably, grout of high quality is present between the tension member 1 and the
pipe 19 at the lower end of the anchor, in the area of the grout body. Towards the
top, grout of lower to very low strength, or another anti-corrosion medium, which
can also be a liquid, can be present in the gap between the tension member 1 and the
pipe 19.
[0034] In this case, the pipe 19 ensures that any aggressive medium present in the ground
is not able to reach the tension member 1, or can do so only with difficulty. In order
to obtain better adhesion of the grout to the pipe 19, both the inside and outside
of the pipe 19 can be roughened in the region of the grout body to be formed.
[0035] As can be seen from Figure 8, if a tension anchor of this type is very long, for
example longer than 8 metres, it is made up of various tension members 1. The tension
members are coupled to one another by means of nut bushes 20, which are provided with
a screw thread. When the pipe 19 is used around the tension member 1, said pipe also
consists of various lengths which are connected to one another by couplings 21. It
is also pointed out that the pipe 19 is closed off at the top of the tension anchor
during injection with grout or water.
[0036] Another embodiment is illustrated in Figure 9. The important feature is the fitting
of a pipe section 23, specifically over the length of the grout body in the vicinity
of the lower section of the tension member. With this arrangement, the pipe section
23 is a smooth tube which optionally has been roughened or, for example, a ribbed
tube made of plastic. Said pipe section 23 encloses the tension member 1 and the tube
5 and has an internal diameter of a size such that the tube 5 can pass between the
pipe section 23 and the nut. Before the anchor is used on site, grout or another force-transmitting
medium is introduced under controlled conditions, for example in the factory, between
the pipe section 23 and the tension member 1, over the section where the grout body
is to be produced. The tube 5 is fitted around the tension member 1 beforehand, optionally
with clamps 6, at least for the section where grout has been introduced in the factory.
After the grout has set, the tube 5 is embedded and firmly joined over said section
to the tension member 1. The pipe section 23 is now also firmly joined to the tension
member 1 and can also terminate before or at the drill bit 3.
[0037] During work on site it is possible that the tube 5 is placed along the entire tension
member 1, without a pipe being fitted around the tension member 1. It is also possible
that a tube 5 is fitted around the entire tension member 1 and that a smooth pipe
19 is positioned starting from the pipe section 23 in the manner shown in Figure 8,
the pipe section 23 being connected to the pipe 19 by means of known connecting means.
Another possibility is that the pipe 19 is closed at the bottom in the vicinity of
the pipe section 23 and has a connector to which the tube 5, emerging from the gap
between the pipe section 23 and the tension member 1, can be connected. The pipe 19
can then be connected to the pipe section 23 in order to prevent rotation of the pipe
19 with respect to the tension member 1. In this case, during the injection of grout,
grout first flows through the gap between the pipe 19 and the tension member 1 and
then through the tube 5 to the injection locations in the vicinity of the drill bit
or elsewhere at locations in the pipe section 23, which may or may not be ribbed.
[0038] In order to prevent penetration of soil, the ends of a tube 5 or pipe 19 can be provided
beforehand with screening or sealing means, which are dislodged, as soon as grout
injection is started, by the high internal pressure then prevailing.
1. Method for fitting a grouted anchor for anchoring revetment walls, buildings, bank
protection works, quay walls and the like and grouted anchor which can be used for
carrying out this method, characterised by the following steps:
- introducing into the ground a solid or hollow anchor rod made of high-grade steel,
- via a cavity in the rod, a pipe fitted around the rod and/or one or more small tubes
which are fixed to the outside of the rod and at least one of which terminates in
the vicinity of the lower end of the rod, feeding liquid into the hole around the
rod while the rod is introduced into the ground,
- feeding grout via said rod cavity, pipe and/or small tubes as soon as the lower
end of the rod has reached the desired level from the top of the grout body,
- introducing grout under a pressure of at least 15 bar into the ground via said pipe,
small tubes and/or cavity,
- bringing the lower end of the rod to the desired depth while the grout is fed in
under high pressure and
- allowing the grout to set.
2. Method according to Claim 1, characterised in that before introducing grout under
a pressure of at least 15 bar into the ground, the lower end of the rod is brought
to the desired depth while feeding in grout under normal pressure and the rod is then
withdrawn from the ground over the desired length of the grout body.
3. Method according to Claim 1 or 2, characterised in that the rod is provided with a
drill bit at its lower end and can be introduced into the ground by pushing and turning.
4. Method according to Claim 3, characterised in that the drill bit is provided with
a propeller blade which has 0.2 to 5 screw turns.
5. Method according to Claim 3 or 4, characterised in that the rod is provided with helically
arranged ridges and the drill bit is screwed to the lower end of the rod with the
aid of a nut welded to the bit.
6. Method according to one of the preceding claims, characterised in that a number of
small tubes for supplying liquid and grout have their outlets at various heights above
the lower end of the rod.
7. Method according to one of the preceding claims, characterised in that the rod consists
of sections which are coupled to one another by means of couplings.
8. Grouted anchor consisting of a solid or hollow rod which, at least at the lower end,
is provided with a screw thread or helically arranged ridges, characterised in that
a drill bit (3) is screwed onto the lower end of the rod.
9. Grouted anchor according to Claim 8, characterised in that the connecting element
between drill bit and rod is a nut (4).
10. Grouted anchor according to Claim 8, characterised in that the drill bit comprises
one or more triangular plates which on one side are connected to the connecting element.
11. Grouted anchor according to Claim 8, characterised in that a core rod is fixed to
the connecting element, and a propeller blade which has 0.2 to 5 screw turns and a
minimum diameter which is greater than the diameter of the connecting element is located
around said core rod.
12. Grouted anchor according to Claim 11, characterised in that the diameter of the propeller
blade tapers.
13. Grouted anchor according to one of Claims 8 to 12, characterised in that one or more
small tubes (5) are arranged along the anchor rod (1), said small tubes (5) being
fixed to the anchor rod and at least one of said tubes terminating in the vicinity
of the lower end of the anchor rod or in the drill bit (3).
14. Grouted anchor according to one of Claims 8 - 12, characterised in that a pipe (19)
is arranged around the tension member (1), which pipe is fixed to the drill bit (3).
15. Grouted anchor according to Claim 14, characterised in that slots (22) are made in
the lower end of the pipe, into which slots the top edge of the drill bit (3) projects.
16. Grouted anchor according to either of Claims 14 or 15, characterised in that the end
section of the pipe (19) intended for adhesion of grout is roughened.
17. Grouted anchor according to Claim 16, characterised in that a small tube (5) is arranged
at least around the lowermost section of the tension member (1), which tube (5) has
its outlet in the vicinity of the drill bit, in that a pipe section (23) encloses
the lower end of the tension member (1) and said small tube (5) over the length of
the grout body to be introduced and in that a force-transmitting medium is introduced
into the gap between the pipe section (23) and the tension member (1).
18. Grouted anchor according to Claim 17, characterised in that the upper end of said
pipe section (23) is connected to a pipe (19) arranged around the tension member.
19. Grouted anchor according to Claim 18, characterised in that the closed lower end of
the pipe (19) is connected to a union to which the small tube (5) positioned in the
gap between pipe section and tension member is connected.