Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
REINFORCING MEMBER FOR EARTH ANCHORING
AND METHOD OF USING THE SAME
TECHNICAL FIELD
The present invention relates to a reinforcing
member having a fixing portion against grout used in
earth anchoring methods such as ground anchoring method,
earth reinforcing method and NATM method, and more
particularly, to a reinforcing member composed of FRP and
a method of using the reinforcing member.
BACKGROUND ART
In recent years, as a reinforcing member for
concrete, a reinforcing member composed of FRP (herein
after referred to as "FRP reinforcement") which is
excellent in corrosion resistance has started to be used
in place of a steel member (hereinafter referred to as
"PC steel member"). In the same way, this FRP
reinforcement has been used as a reinforcing member for
earth anchoring methods such as ground anchoring or the
like.
Among the various reinforcing members used in
earth anchoring methods described above, the reinforcing
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member to be used for the ground anchoring method
comprises a front fixing portion to be fixed in ground
by grout (for example, concrete), an anchor free length
portion as an intermediate portion of the member and an
anchor head portion to which a frame structure is fixed
at the ground surface by an anchor nut or the like.
In this reinforcing member, as a matter of
course, the front fixing portion is required to be firmly
bonded to the grout and the anchor free length portion is
required to have both corrosion resistance and
non-adhesive property against the grout.
Therefore, in a case where the conventional
reinforcing member composed of PC steel is used, the
anchor free length portion of the reinforcing member is
covered with a smooth sheath. Further, even in a case
where the FRP reinforcement is used in place of the
covered PC steel member, there is not posed a problem of
corrosion resistance. However, in order to secure the
sufficient non-adhesive property against the grout, as in
the same manner as in the case of the PC steel member,
the reinforcement is executed in such a manner that the
smooth sheath is provided to the anchor free length
portion under present circumstances.
Further, in a case where the smooth sheath is
not used, an edge-separation for separating the anchor
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free length portion from the fixing portion is
performed, for example, by winding a non-adhesive tape
(vinyl tape) around the anchor free length portion.
In order to secure both the adhesive property
against grout for the front fixing portion of the FRP
reinforcement and non-adhesive property against the grout
for the intermediate portion of the FRP reinforcer, each
FRP reinforcement for the earth anchoring method is
required to be provided with the smooth sheath at the
intermediate portion as the anchor free length portion.
Therefore, the construction of the FRP reinforcement will
become complicated.
Furthermore, since the reinforcement has a
construction in which the smooth sheath is attached, each
of the FRP reinforcement for the earth anchoring method
is required to be manufactured one by one at a factory,
and a mass-production of the FRP reinforcement was
difficult.
As the result, there were posed problems such
that each of the FRP reinforcement for the earth
anchoring method requires an increased cost and that
since a length of the reinforcement was limited or fixed
to a predetermined length, an anchoring length could not
arbitrarily be selected or determined at a construction
site.
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Further, in a case where the separation is
performed by winding vinyl tape around the anchor free
length portion, each of the vinyl tapes is required to be
carefully or minutely wound around the free length
portion by a handwork, so that the winding operation
would become remarkably troublesome or complicated at a
construction site.
The present invention is achieved for solving
the aforementioned problems and an object of the present
invention is to provide a reinforcing member for an earth
anchoring method and a method of using the reinforcing
member which is not required to provide a smooth sheath
or tape for imparting non-adhesive property against grout
to the anchor free length portion and capable of easily
imparting an adhesive property against the grout to only
a front fixing portion of the member at the construction
site.
DISCLOSURE OF THE INVENTION
In order to achieve the aforementioned object,
the reinforcing member for an earth anchoring method
according to the present invention is constructed such
that a rod, which is composed of FRP and has a surface
on which irregularities are formed, is covered with a
cover film.
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Further, the reinforcing member for an earth
anchoring method according to the present invention is
constructed such that a string body such as tape or the
like is wound in a spiral shape around a surface of a rod
composed of FRP so that a surface of the string body is
almost flush with the surface of the rod.
Thus formed reinforcing member is used in a
manner such that the cover film or the string body is
partially removed and the removed portion is used as a
fixing portion against the grout.
In the construction described above, when the
cover film or the string body which is attached on the
surface of the rod is peeled off, the irregularities
formed on the rod surface of the peeled portion appear
and the peeled portion having the irregularities will
perform a function as a fixing portion against the
grout, while another portion will perform a function as
a non-fixing portion.
In particular, in a case where the cover film
or string body is composed of a material which is
dissolved or gelled through a reaction with an uncured
grout, a non-fixing portion from which the cover film or
string body is not peeled acts such that the cover film
or the string body is dissolved or gelled through a
reaction with the grout so as to form a void space having
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a thickness corresponding to that of the cover film or
the string body, the void space being formed between the
reinforcing member and the grout. Therefore, a
non-adhesive proper-ty between the reinforcing member and
the grout can be further improved.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more apparent
and more easily be understood from the following detailed
description when taken in conjunction with the
accompanying drawings in which preferred embodiments of
the present invention are shown by way of illustrative
examples.
Further, the embodiments shown in the
accompanying drawings are not for specifying or limiting
the scope of this invention, but for merely making the
explanation and understanding of this invention more
easily.
In the accompanying drawings:
FIG. 1 is a perspective view showing a
reinforcing member of a first embodiment according to the
present invention;
FIG. 2 is an explanatory view showing a state
where the reinforcing member according to the first
embodiment is used;
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FIGs. 3 and 4 are explanatory views
respectively showing a sample for pull-out test;
FIG. 5 is a side view showing a reinforcing
member of a second embodiment according to the present
invention; and
FIG. 6 is an explanatory view showing a state
where the reinforcing member of the second embodiment is
used.
BEST MODE FOR CARRYING OUT THE INVENTION
The preferred embodiment of the reinforcing
member for an earth anchoring method, a method of
manufacturing the same and method of using the same
according to the present invention will now be described
hereunder with reference to the accompanying drawings.
In the drawings, a reference numeral 1 denotes
a reinforcing member. The reinforcing member 1 has a
construction comprising a rod 2 composed of FRP and a
tubular cover film 3 formed of a resin for covering the
rod 2. In addition, irregularities 4 are formed on a
surface of the rod 2 in overall length.
When the reinforcing member 1 is used as a
reinforcement for the earth anchoring methods such as
ground anchoring or the like, the cover film 3 formed to
the front portion requiring a sufficient adhesion
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strength is peeled off in a desired length by means of
a cutter or the like.
As the results, as shown in FIG. 2, the portion
from which the cover film 3 is peeled off performs as a
front fixing portion 5, while the remaining portion
performs as the anchor free length portion 6. Then, the
reinforcing member 1 is cut in a desired length.
Subsequently, an anchor head portion (not shown) is
formed at another end portion, i.e., an end portion of
the anchor free length portion side of the member.
These operations and works can be easily
performed at the construction site by executing the earth
anchoring method.
The thus formed reinforcing member 1 is
inserted with its front fixing portion into an anchor box
or hole formed in an anchoring ground. Thereafter, the
grout is injected into the anchor box and then cured.
At this time, the grout is injected into whole
of the anchor box and the reinforcing member 1 contacts
to the grout at full length of the anchor length
portion. However, the top fixing portion 5 from which
the cover film 3 is removed is bonded to the grout,
thereby to be firmly fixed to the ground side. On the
other hand, at the anchor free length portion 6 having
the cover film 3 thereon, since the cover film 3 is
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interposed between the reinforcing member 1 and the
grout, the reinforcing member 1 and the grout are
remained in a non-bonded state, so that the frictional
resistance against the cured grout hardly occur. As
described above, the cover film 3 attains a substitute
function alternative to that of the smooth sheath used in
the prior art.
In the FRP materials constituting the
reinforcing member, as the example of the reinforcing
fiber, inorganic fibers such as carbon fiber, glass
fiber, or organic fibers such as aramid fiber or the
like are preferably used. In addition, as the examples of
the matrix resin, thermo-setting resins such as epoxy
resin, unsaturated polyester resin, phenolic resin,
vinyl ester or the like, and thermoplastic resins such
as nylon, polyester or the like are preferably used.
The material constituting the cover film 3 is
not limited as far as the materials can be easily peeled
off from FRP. In particular, it is preferable to use the
material having an extremely small shearing strength or
a large extension under a small stressed condition. As
the example of the material, in addition to soft vinyl
chloride, polyethylene, polypropylene, nylon or the like,
rubber and elastomer are also generally used. However,
the material is not limited to these ones.
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Even if the shearing strength of the material
is not small as described above, such material can
satisfy the above conditions by lowering a thickness of
the material. Further, a foam material having bubbles
therein can be also used.
In addition, as a material for covering the
aforementioned rod 2, the material having a small
friction resistance is preferable. Such examples may
include polyethylene, polypropylene, polyacetal,
fluorine resin, silicon resin or the like. However, the
materials are not limited to these ones.
As a material for constituting the cover film
3, it is preferable to use materials that contact and
react with the uncured grout so as to be dissolved or to
form a gelatine-like swelling-gel. In this case, during
a time when the grout injected into the anchor box is
cured, the cover film 3 is dissolved or swelling-gelled
so as to form a void space between the rod 2 and the
cured grout. Therefore, the friction resistance against
the grout at the anchor free length portion 6 can be
eliminated.
In this case, the materials for the cover film
3 may include crosslinked polyacrylamide, acrylic acid or
the like. However, in consideration of that the concrete
which is one example of the material for the grout has
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strong alkaline property, it is more preferable to use
cellulose type or starch type materials such as
crosslinked polyvinyl alcohol, agar each having no ion
group therein. Further, as the material for the cover
film 3, there can also be used a material in a form of
non-woven fabric cloth bonded to the rod 2 through an
adhesion agent which is soluble into water contained in
the concrete.
The covering operation of the cover film 3 onto
the rod 2 is performed in accordance with well-known
methods such as coating a material in a molten state onto
the rod or inserting the rod into a tubular member on the
way of forming the rod 2 or after the completion of the
rod forming.
FIGs. 1 and 2 respectively show an example of
the reinforcing member which is formed in a manner such
that the rod 2 is formed by winding a tape 11 around the
surface of the rod so as to form irregularities 4
thereon, and a tubular cover film 3 is covered on the rod
2. Hereinafter, concrete examples will be shown.
Rod portion
Reinforcing Fiber: carbon fiber, T700S, mfd. by
Toray Co., Ltd.
Matrix Resin: Epicoat No.6003 System, mfd. by
Yuka Shell Co., Ltd.
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Vf (Volume Fraction): 65%
Diameter: 10 mm
Shape of Groove: groove width 4mm
groove depth 0.5mm
groove pitch 10mm
Covering portion
Material: soft vinyl chloride EX512B, mfd. by
Shinetsu Polymer Co., Ltd.
Thickness: lmm
A part of the cover film 3 ranging 100mm from
the top end of thus formed reinforcing member 1 was
peeled off to thereby prepare two samples of A and B.
Then, as shown in FIG. 3, a mortar body 15 having a
diameter of 100 mm was bonded to only a portion of one
sample of A from which the cover film 3 had been peeled
off. While, as shown in FIG. 4, regarding the other
sample of B, a mortar body 16 having a diameter of 100
mm was bonded to a portion in a total length of 300 mm
including the portion of the cover film 3 having been
peeled off and a portion adjacent to the peeled portion.
Then, with respect to each bonded sample, a
pull-out test was conducted and repeated for three times.
The test results are shown in Table 1 hereunder. Further,
the mortar bodies 15 and 16 were composed of a mortar
material of which trade name is Denka-Pletascon T-1 (mfd.
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by Denki-Kagaku Co., Ltd.), and a compressive strength of
the respective mortar body 15 or 16 at the pull-out test
was 482 kg/cmZ.
Table 1
Samples 1 2 3 Average Pull-out Load
A 3.18 3.05 3.47 3.23
B 3.82 3.54 3.88 3.74
Unit: ton
As is clear from the results shown in Table 1,
the pull-out loads in both the samples of A and B were
almost the same to each other in an average value. This
means that, in the case of sample B, the bonding to the
mortar body was accomplished only at the portion of the
cover film 3 having been peeled off. From this fact, it
was confirmed that the edge-separation of the fixing
portion from the non-fixing portion was securely
accomplished in accordance with the presence or absence
of the cover film 3.
In the above example, there is shown a
reinforcing member comprising a rod 2 having the
irregularities thereon and the cover film 3 covering the
rod 2. In this regard, the cover film 3 is provided in
order to lower the friction resistance against the grout.
Therefore, if the surface of the rod 2 per se as a small
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friction resistance against the grout, the cover film 3
will not be required.
FIG. 5 shows an example of such structure, in
which, in order to form a helical or spiral groove, the
tape which had been wound around the rod 2 at the time of
forming the rod 2 remains as it is even after the rod 2
has been cured. Then, the surface of the rod 2 is
smoothly finished so that the surface of the rod 2
provides a small friction coefficient.
The thus formed reinforcing member 1 is cut in
a desired length. Thereafter, as shown in FIG. 6, the
tape 11 wound around the front fixing portion 5 is
peeled off to thereby form a spiral groove 4a on the
peeled portion.
In this case, the tape 11 wound around a
portion except the front fixing portion 5 remains as it
is, so that the friction resistance of the remaining
portion against the grout can be reduced.
Hereunder, an explanation will be started with
respect to the concrete example of the reinforcing member
1 which is used in a manner such that only the tape 11
having been wound around the front fixing portion 5 of
the rod 2 is peeled off.
The specifications of the rod portion are the
same as those of aforementioned example.
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A part of the tape 11 ranging 100mm in the
front fixing portion 5 of the thus formed rod 2 was
peeled off so as to prepare two samples of a and b.
Then, as in the same conditions as those applied to the
case of the samples A and B from which the cover film 3
had been peeled off, the pull-out test was conducted and
repeated for three times with respect to each of the
peeled samples of a and b.The test results are shown in
the following Table 2.
As is clear from the results shown in Table 2,
and as the same as the aforementioned example, it was
confirmed in both samples of a and b that the bonding to
the mortar was accomplished only at the portion of the
tape 11 having been peeled off. From this fact, it was
also confirmed that the edge-separation of the fixing
portion from the non-fixing portion was securely
accomplished in accordance with the presence or absence
of the tape 11.
Table 2
Samples 1 2 3 Average Pull-out Load
a 3.18 3.05 3.47 3.23
b 3.62 3.74 3.17 3.50
Unit: ton
According to the present invention as described
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above, the reinforcing member 1 for the earth anchoring
method has a construction comprising a rod 2 composed of
FRP and having irregularities formed thereon and a cover
film 3 covered around the rod 2. Due to this
construction, when the cover film 3 is peeled off in a
desired length, only such peeled portion can perform a
function as a fixing portion for bonding to the grout,
while the remaining portion covered with the cover film
3 performs a function as a non-fixing portion against
the grout.
Accordingly, the construction of the
reinforcing member for the earth anchoring method having
both the fixing portion and non-fixing portion against
the grout can be remarkably simplified without requiring
a smooth sheath or a partially tape-winding. In addition,
since the rod 2 is composed of FRP, the reinforcing
member is free from a problem of corrosion.
Furthermore, when the reinforcing member 1 has
a construction comprising a rod 2 composed of FRP and a
string body such as tape 11 or the like for forming
irregularities on a surface of the rod 2, the string body
being spirally wound around the surface of the FRP rod 2
so that a surface of the string body is almost flush
with the surface of the rod 2, then the string body is
peeled off in a desired length, the peeled portion can
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perform a function as a fixing portion against the
grout. Accordingly, the construction of the reinforcing
member 1 requiring both the fixing portion and
non-fixing portion can be simplified.
In addition, when the cover film 3 and the
string body are composed of a material which is
dissolved or gelled through the reaction with an uncured
grout, it becomes unnecessary to peel off the cover film
3 and the string body, whereby the reinforcing member can
be easily available.
Furthermore, the aforementioned reinforcing
member 1 can be manufactured in accordance with the same
procedures as those of the ordinary reinforcing member
composed of FRP.
In addition, in the reinforcing member 1
according to the present invention, when the cover film
3 or the string body is removed, the removed portion can
perform as a fixing portion against the grout. Therefore,
an adhesive property against the grout can be easily
imparted to only the front fixing portion of the member
even at the construction site, whereby the reinforcing
member can be easily executed or applied.
Although the present invention has been
described with reference to the exemplified embodiments,
it will be apparent to those skilled in the art that
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various modifications, changes, omissions, additions and
other variations can be made in the disclosed embodiments
of the present invention without departing from the scope
or spirit of the present invention. Accordingly, it
should be understood that the present invention is not
limited to the described embodiments, and shall include
the scope specified by the elements defined in the
appended claims and range of equivalency of the claims.
