Note: Descriptions are shown in the official language in which they were submitted.
Ground anchors
This invention concerns ground anchors for use in the
civil engineering, construction and mining industries for
example.
There is a requirement for ground anchors to have
at least a double corrosion protection about the central
anchor element, such ~as that p~ovided by a waterproof
sleeve~which is grouted on to t:he element. Such anchors
are known, but the sleeves are applied to the anchor
element in a factory and each anchor must be purpose-
lQ built. This makes it expensive to manufacture and
- transport a small number of anchors for a specific
application, and there is often a long delay before
the anchors can be delivered to the site of use. There
is therefore a need for a simple and cheap way of corro-
sion proofing an anchor element on site to specificrequirements, and this invention fulfills that need~
` According to one aspect of the invention there is
provided a method of at least double corrosion proofing
an anchor element on site, comprising (i) locating a
plurality of lengths of corrosion proof sleeve in end-
to-end relation about an end portion of the anchor
element to cover the length of the element to be corro-
sion proofed, said sleeve comprising three layers wherein
the outer layers are corrosion-proof and at least one is
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plastic, and the intermediate layer is of a set filler,
(ii) applying a cap to the sleeve at the end o~ the anchor
element, the cap having an inlet for self-setting compo-
sition, and (iii) supplying a self-setting composition
through the inlet, via the cap, into an annular clearance
between the element and the sleeve there to set to secure
the sleeve to the element.
According to another aspect of the invention there
is provided an anchor, comprising an anchor element, a
10 plurality of sleeve lengths being located in end-to-end
relation about an end portion of the element, the sleeve
lengths being secured to the element by means of a self-
setting c~omposition located between the element and the
sleeve, the sleeve comprising an outer layer of plastics
15 having external castellations, an intermediate layer of
set filler and an inner layer of metal being internally
threaded, and a cap being secured to an end of the anchor
by means of the self-setting composition.
Preferably the cap is secured to the anchor element by
20 means of the self-setting composition to seal the end of
the anchor against ingress of moisture and to protect the
leading end of the anchor during insertion into a borehole.
he sleeve lengths will usually be connected together
such that the sleeve is sealed against escape of self-
25 setting composition during introduction of the compositioninto the sleeve.
Preferably the sleeved anchor element is upwardly
inclined away from the cap for best escape of air whilst
the self-setting composition is supplied into the sleeve.
The inlet is preferably located in the side of the cap.
When the anchor is upwardly inclined for introduction of
self-setting composition, the inlet is less liable to
damage in this location, and the inlet is less likely
~` to become blocked by dirt.
The sleeve preferably has at least two corrosion~proof
layers. It is especially preferred for the sleeve to
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comprise three layers, the intermediate layer being of set
filler such as a resinous or a cementitious grout and at
least one of the other two layers being of plastics. Most
preferably the sleeve comprises an outer layer of plastics,
an intermediate layer of set filler and an inner layer of
metal. The metal inner layer serves to strengthen the
sleeve for handling purposes.
The anchor element may be a bar such as Macalloy*
or Dividag* bar having either a plain or a ribbed pro-
file. Plain bars may be used with threaded nuts andplain washers, the nuts being screw-threaded on to a
co-operatively threaded end portion of the bar.
* Trade Mark
.d>~
- ~ - GBP 102
Ribbed bars do not require the use of a nut and washer, but rely
instead upon the ribs to transfer load from the tendon to the sleeve.
The method is particularly useful for corrosion proof-
ing strand tendons. Known factor~J methods require "nodin~" of
~5 each strand to transfer the stress from the strands to the sleeve,
This noding involves removal of a polypropylene coating from the
length of the tendon to be corrosion proofed, followed by
untwlsting of the strands and thorough~cleaning off of any grease
from the strands. A node is then applied to each strand whereupon
the strands are re-twisted and secured inside the sleeve. rne
nodes serve to lock the strands to the sleeve.
When the method of the invention is used to corrosion
proof a strand tendon on site, the plastics sheathing is stripped
off the tendon and the tendon surface is wiped free OL srease
/~5 without untwisting the strands. A metal ferrule is then compressed
onto the end of the tendon for best transfer of tendon load to ~he
sleeve. me sleeve ls then secured to the end portion of the
tendon by the method of the invention~
The sleeve should have longitudinally spaoed apart
0~ external circumlerential ribs and should be internally threaded
to respectively provide a good ke~ between the sleeve and the grout
used to secure the element in the hole,and between ~he sleeve and
the sel~ setting composition which is used to secure the sleeve to -
the anchor element.
~5 The invention includes a ground anchor made by the
method, ard further includes the sleeve lengths themselves as new
items of commerce,
The invention is described below by way of example with
- reference to the accompanying diagrammatic drawings in which
Figure 1 is a side view, partly ln section, of a length
of sleeve for use in the method~
Figure 2 is a sectional view showing the sleeve being
secured to an anchor element by the method of the invention, ~nd
_ h _ CBP 102
Figure ~ is a sectional view of an alternative method
of securing together two sleeve lengths.
The sleeve 1 of ~lgure 1 comprises an outer tube 2 of
p~astics, the tube hav~ng spaced-apart castellations ~, an inner
steel tube 4 having a thread 5, and an intermedia~e layer of set
polyester resin 6. Both ends of the sleeve 1J only one end being
shown for convenience in Figure 1, have two diametricall~J opposite
recesses 7. Towards each end of the sleeve, an 0-ring 8 is located
about the tube between the cas~ellations ~. -
~O In use, a ribbed steel bar 9, Figure 2, to be corrosion
proofed ~or use as a ground anchor, is mounted on a trestleJ not
shown, at a construction site. A suitable number o~ sleeve lengths
1 are ~itted over one end o~ the rod 9 in end-to-end relation. For
convenience only two sleeve lengths are shotm in Figure 2. A
~5 connecting tube 10 is fitted over the adjacent 0-rings 8 o~ adjacent
sleeve lengths. An end cap 11 comprising a mouth oortion 12 and a s~de
inlet 13, is fittad over the end of the sleeve. The clearance
between the mouth 12 of the end cap 11 and the sleeve 1 is sealed
by the adJacent 0-ring 8.
: a ~ A polyester resin grout 14 is then pumped through the
inlet 13 of the cap 11 into the annular clearance 15 between the
sleeve and the rod. The anchoris upwardly inclined a~y from
the end cap for best escape of air during introduction of the grout.
Tne grout is forced into the clearance between adjacent ends of
~1 S the sleeve lengths there to provide a molsture-proof seal. The
recesses 7 facilitate passage of the grout between the sleeve ends
and also act as Xeys more firmly to secure the sleeve lengths to-
gether ~ means of the grout within the recesses.
Af-ter sufficient time to allow the polyester grout to
harden~ the inlet 1~ is sawn off and the anohor located in a hole
in a substrate in known manner. The cap 11 serves as a guide for
the anchor and protects the leading end of the anchor during inser-
tion into a hole. The grout ~ thin the end cap 11 seals the end of
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the anchor against penetration of moisture.
A strand tendon may be used in place of the rod 9.
In this case, the tendon is prepared by removing the protective
sheath along the length of the tendon to be corrosion proofed.
The bared tendon is then thoro~hly degreased and a ferrule is
compressed on to the end of the tendon. The tendon is then
sleeved as described, the ferrule being located within the cap 11.
Figure 3 shoNs an alternative way of joi~lng together
adjacent sleeve lengths. The ex~ernal ~lastics layer 2 of one
sleeve length la has a female extension 16, and the same layer of
the adjacent sleeve length lb has a male extension 17. The extensions
16, 17 are screw-threaded one into the other.
The method o~ the invention allows corrosion-proof
anchors to be made quickly and cheaply on site to meet individual
requirements. The sleeve is capable of transferring the maximum
load of the anchor element to the borehole grout, provided a
sufficient length of sleeve is used. The minimum length of sleeve
for full load trans~er ranges ~rom 4 m ~or a 110 mm external dia-
meter sleeve, to 1.5 m for a 65 mm external diameter slee~e,
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