JPH0791829B2 - Ground anchor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground anchor used for fixing a structure on the ground, and more particularly to a highly reliable ground anchor in which breakage of a tensile member is unlikely to occur.

[0002]

2. Description of the Related Art As a ground anchor, a tensile material such as a stranded steel wire is passed through an unbonded sheath, and the folded portion is hooked on a load bearing body such as a casting and inserted into the ground to inject a hardening material. A fixed C-turn type ground anchor has been developed. Such a ground anchor is called a compression anchor because a compressive force acts on the load bearing body. There is a type of this compression type anchor in which the tension material is fixed to the bearing plate, which is a load bearing body, by the compression grip, but the cost is significantly increased as a result of the implementation, and the load of multiple tension materials is It has been found that the C-turn type anchor described above is more advantageous because it is difficult to disperse in the body.

[0003]

The problem of the C-turn type anchor described above is that an extremely large load is concentrated on a portion which is folded back and hooked on a load-bearing body, so that the breaking strength of the folded-back portion is reduced by about 10%. In other words, 10 by design
Even a tensile material that can withstand a load of 0 tons is actually 9
Even if a tension of about 0 tons was applied, it sometimes broke.

Another problem to be solved by the present invention is
When C-turn processing is performed, the load is concentrated on the folded back portion, and the unbonded sheath covering that portion is broken. With the conventional C-turn type anchor, there is nothing to cover the tensile material other than the unbonded sheath, so the water that comes out of the ground touches the tensile material through the cracks in the hardened material, causing the tensile material to rust and causing breakage. It was.

Another problem to be solved by the present invention is
In the case of a load distribution type anchor using a plurality of load bearing bodies, it is to prevent the load from being concentrated only on the shorter tensile member. A load-dispersed anchor is divided into several groups, the length of the tensile member is changed for each group, and the anchors are hooked on the load-bearing bodies. It is a fixed thing. The tension applied to each tension material is
It works by being dispersed over a plurality of load bearing bodies. In this load-dispersion type anchor, the length of the tensile member is different for each group as described above, and the reason is that the elongation amount is also different. That is, since each tensile member is made of steel, elongation is caused by the application of a load.
This elongation is large when the length of the tensile member is long, and small when it is short. When tension members with different lengths are simultaneously tensioned with the same force, the shortest tension member reaches the elongation limit first. That is, only the shortest tensile material reaches the limit of elongation, and the other tensile materials have room for elongation. If the load is more than this, the load acting on the shortest tensile member becomes larger than the other loads. This is the same phenomenon as when a rubber rope that allows elongation and a steel rope that allows only small elongation are simultaneously tensioned, only the steel rope receives a large tension force and the rubber rope bears only a small amount of elongation. If the tension exceeds this limit, only the load acting on the shortest tensile member is significantly increased, and as a result, the load exceeds the breaking load and breaks.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly reliable ground anchor in which breakage of a tensile member is less likely to occur in the case of a C-turn type anchor. And

[0007]

In the ground anchor according to the present invention, not only the load-bearing body bears the load, but also the tension member is partially fixed to form an auxiliary fixing portion, and the auxiliary fixing portion also bears the load. Is. First, the case of using a single load bearing body will be described. A tensile material such as steel stranded wire is passed through an unbonded sheath made of polyethylene or the like, and a part of the tensile material is exposed without covering the unbonded sheath only in the middle portion of the entire length. This tensile member is folded back in the middle and C-turn processed, and the folded back portion is hooked on the load bearing body. A certain length is exposed from the load-bearing body, and this portion becomes the auxiliary fixing portion. The length of this auxiliary fixing unit is 0.5 to
1.5 m is preferred. The number of tensile materials is limited to one,
You may hang several pieces on one load-bearing body. As the load-bearing body, not only one made of a casting whose curved portion is processed into a curved surface but also one made of a synthetic resin having high yield strength can be used. The portion of the tensile member hooked on the load bearing body is passed through the fixing sheath. As the fixing sheath, a deformed stainless steel sheath having irregularities on its peripheral surface is used. The other part of the tensile member is passed through a synthetic resin straight sheath. In this state, it is inserted into the drilled hole in the ground, and a hardening material such as cement milk is injected and fixed. Then, tension is applied to the tension material.

When a plurality of load-bearing bodies are used, a plurality of tension members are divided into a plurality of tension member groups. This tensile material group may be composed of not only a plurality of tensile materials but also a single tensile material. The tensile member has different lengths for each group, and is hooked on the load bearing body for each group. The tensile member hooked on the load-bearing body is slid for each group, passed through the fixing sheath and the straight sheath, and inserted into the drilled hole. The hardening material is injected and fixed, and the tension material is tensioned. In tension, the tension can be changed for each group. Since the tensile members have different lengths depending on the groups, there is a difference in elongation when they are tensioned. Therefore, when tensioned together, a large load acts only on the shortest tensile member. For this reason, tension is performed separately for each tension material group to change the tension force applied to each group. The applied tension gives the greatest tension to the longest tension material, and the tension decreases in order as it becomes shorter. Tensile force of about 60% of breaking load is applied to the longest tension material as tension force, and for tension materials with shorter length than that, 5 to 1 in order of decreasing length.
It is preferable to reduce the tension by 0%. Further, it is preferable that the interval between the load bearing bodies is 1.5 to 3 m, and the length from the load bearing body closest to the ground to the ground surface is approximately 6 m.

[0009]

[Function] The auxiliary fixing portion of the tensile material that has been exfoliated in the hardening material adheres to the hardening material. When the tension force acts, the tension force is also taken up by the auxiliary fixing portion, so that the entire load does not return to act on the C-turn processed portion. That is, since the auxiliary fixing portion bears a part of the load in order to compensate for the decrease in the proof stress of the C-turn processed portion, the tensile member is not broken. This auxiliary fixing length part is 0.
Although the length is as short as 5 to 1.5m, even if the adhesive fixing breaks between the auxiliary fixing long part and the surrounding hardening material due to the tension force, the fixing sheath made of stainless steel restrains the hardening material and greatly reduces the adhesion strength. Do not cause. In other words, it is important to restrain the auxiliary fixing length portion and the hardening material with the stainless fixing sheath, and the synthetic resin sheath cannot obtain such a restraining adhesion effect.
Further, although the tension material is partially exposed, since it is covered with the fixing sheath, water does not reach the tension material.

In the case where the tension members having different lengths are hooked on separate load-bearing bodies to change the tension applied to the respective members, and if the load increases due to an unexpected situation, the tension members are dispersed and act on each tension member. To do. However, as described above, the tensile material having a short length has a smaller elongation than the tensile material having a long length, and therefore the rate of increase in load is larger than that of the long material. Due to an unforeseen situation, while the tension force of the longest tension material increases by 10%, for example, the second longest tension material has 10% or 3%.
The second longest tensile material would increase by 20%. In other words, the increase rate of the load is high due to the small elongation, and even if there is a difference in the tension force given in advance, the load that the shorter tensile member bears approaches the load that the longer tensile member bears as the load increases. Come on. When the load which the longest tensile member bears finally becomes 80% of the breaking load, the load acting on other tensile members also becomes close to 80% of the breaking load. In this way, a load that is nearly equal acts on all of the plurality of tension members. When a load larger than this is applied, as shown in FIG. 4, at 80% or more of the breaking load, there is no significant difference in elongation deformation between the short tensile member and the long tensile member, and there is substantially no problem.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on an embodiment shown in the drawings. FIG. 1 shows a first embodiment of the present invention, in which a plurality of ceramic fixing rods 2 are attached to a load-bearing body 1 made of cast metal and having an end surface curved. A tensile member 2 is hung on the load bearing body 1. A stranded steel wire is used as the tensile member 3, the unbonded sheath 4 is not covered only in the middle portion of the entire length thereof, and the tensile member 3 is exposed. The middle of the tensile member 3 is folded back and processed by C-turn, and is hooked on the load bearing body 1. At this time, a part of the tensile member 3 that has been stripped off is the auxiliary fixing long portion La, and the length thereof is 1.5 m. The auxiliary fixing long portion La of the tension member 3 is inserted into a stainless fixing sheath 5 having an uneven surface. Also, the fixing sheath 5
The tip portion is placed in a straight sheath 6 made of synthetic resin. The end of the fixing sheath 5 is covered with a cap 7.

Drilling holes 8 excavated in the ground in the above state
Cement milk as a hardening material 9 is inserted into the inside and outside of the sheaths 5 and 6 through the inner grout pipe and the outer grout pipe and fixed therein. When the tension member 3 is strained, the load is not only received by the load bearing body 1 but also by the fixing portion of the auxiliary fixing long portion La, and the total load is not applied to the C-turn processed portion, thus compensating for the decrease in the proof stress of the C-turn processed portion. Further, since the fixing sheath 5 is covered, the water coming out of the ground does not reach the tension member 3.

FIG. 2 shows a second embodiment of the present invention, in which six tension members 3 are divided into two and hung on three load bearing members 1. The tension members 3 divided into three each form a group, and each group has a different length. Load-bearing body 1
Are arranged in the fixing sheath 5 while being shifted according to the length of the tension member 3 being different. Interval L between each load bearing body 1
p is 3 m, and the length of the auxiliary fixing long portion La is 1.5 m. Further, the length Lf from the load bearing body 1 on which the shortest tension member 3 is applied to the ground is 6 m.

Drilling holes 8 excavated in the ground in the above state
, And the hardening material 9 is injected and fixed. When applying tension, tension each group and give 60% of the breaking load to the longest tensile member 3a and reduce the tension force to the second longest tensile member 3b by 10%. The tension member 3c having the shortest length is further reduced by 10%. As described above, since each load-bearing body 1 is fixed in the drilled hole 8 by shifting in the longitudinal direction, the load due to the tension force is dispersed,
It is possible to obtain a frictional resistance with the surrounding ground over a long interval in the drilled hole 8. If an unexpected situation occurs and the load increases, the short tensile member 3c has a small elongation rate, so that the load is large. However, the shorter tensile member 3c
The applied tension is smaller than that of the longer tensile members 3a and 3b, and the load that is undertaken gradually catches up, and eventually the loads acting on all the tensile members 3 become substantially equal. The numerical values obtained by the experiment in which this is performed are shown in Table 1 below.

[0015]

[Table 1]

According to the above table, when the distance Lp between the load bearing bodies 1 is set to 3 m and the length Lf from the load bearing body 1 closest to the ground to the ground surface is set to 6 m, the tension members 3a,
The load acting on b and c is evenly distributed to about 80% of the breaking load.

[0017]

Since the present invention has the above-mentioned structure, the following effects can be obtained. Since the folded-back portion of the tension member is peeled off to form the auxiliary fixing length portion, the auxiliary fixing length portion and the load bearing body separately bear the load, so that the load does not concentrate only on the C-turn processed portion where the proof stress has decreased, Hard to break the material. Since the auxiliary fixing length portion is inserted into the fixing sheath, the water that has come out of the ground does not reach the exposed tensile member, and the tensile member does not rust. Further, since the C-turn processed portion is protected by the fixing sheath instead of the unbonded sheath, an accident such as breakage of the unbonded sheath in the C-turn processed portion does not occur. Since the auxiliary fixing length part and the hardening material are constrained by the stainless steel sheath, even if there is a break in the adhesion between the short auxiliary fixing length part and the hardening material, the adhesion force does not decrease significantly due to the restraining effect. The decrease in yield strength can be sufficiently compensated by the adhesive force of the short auxiliary fixing long portion. By fixing multiple tension members using multiple load-bearing bodies, the load can be dispersed and widely fixed by the frictional resistance with the ground, and there is a risk that the ground and hardened material will be cut off. Get smaller. The tension force is applied to each tension material group having different lengths, and the tension force of the short tension material is made small in advance, so even if an unexpected situation occurs and the load increases, the load acting on each tension material remains Since they are almost equalized, the load is not concentrated on a part of the tensile member and the tensile member is not broken. With a simple structure in which the tension applied to the tensile material is changed for each different length, the design, calculation, and construction are simplified, its function is reliably exhibited, and the reliability of the anchor is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a ground anchor according to the present invention.

FIG. 2 is a cross-sectional view of another embodiment.

FIG. 3 is an overall view of an anchor.

FIG. 4 is a graph showing elongation and load of a tensile member.

[Explanation of symbols]

 1 Load-bearing body 2 Fixing rod 3 Tensile material 4 Unbonded sheath 5 Fixing sheath 6 Straight sheath 7 Cap 8 Drilling hole 9 Hardening material

Claims (7)

[Claims] 1. A tensile member, a part of which is exposed without covering the middle part with an unbonded sheath, is folded back in the middle, and the exposed part is hooked on a load-bearing body to give a predetermined length from the load-bearing body. This tension material was placed in a stainless steel fixing sheath as an auxiliary fixing length part, inserted into the drilling hole, and hardening material was injected into and out of the sheath to fix the tension material and to give tension to the tension material. A ground anchor characterized by. 2. The ground anchor according to claim 1, wherein the auxiliary fixing length portion has a length of 0.5 to 1.5 m. 3. A plurality of tensile members, a part of which is not exposed at the middle portion and which is not covered with an unbonded sheath, are divided into several groups, and the tensile members have different lengths. Hook the part that was folded back in the middle for each group and hooked on a separate load-bearing body to make a predetermined length from the load-bearing body as an auxiliary fixing long portion, and slide in the length direction for each tension material group A ground anchor characterized in that it is placed in a fixing sheath, and is inserted into a drilled hole to inject a hardening material into the inside and outside of the sheath to fix it and to give tension to each tension material. 4. The ground anchor according to claim 3, wherein the auxiliary fixing length portion is 0.5 to 1.5 m. 5. A tension member group having the longest length is given the largest tension force, and as the length member is shortened, the tension force given to each tension member group is decreased.
The listed ground anchor. 6. A tensile material group having the longest length is given a tension force of about 60% of the breaking load of the tensile material, and a tensile material having a length shorter than that is applied in the order of decreasing length. The ground anchor according to claim 5, wherein the tension force is sequentially reduced by 5 to 10% of the breaking load for each group. 7. The ground anchor according to claim 3, wherein the distance between the load bearing bodies is 1.5 to 3 m, and the length from the load bearing body closest to the ground to the ground surface is approximately 6 m.