JPH0765310B2 - anchor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anchor for fixing a structure or the like on the ground, and more particularly to an anchor that can obtain a large fixing force and does not cause a breakage of a tensile member.

[0002]

2. Description of the Related Art An anchor that uses a plurality of tension members, divides the tension members into a plurality of tension members, and anchors the tension members individually in a drilled hole. Being developed. For example, as shown in FIG. 1, even in a C-turn type anchor for the purpose of pulling out after use, a plurality of fixing bodies are arranged at appropriate intervals in the drilled hole, and a tension member is pulled by each tension member group. It hangs wood and fixes. this is,
Since a single fixing member has insufficient fixing force and cannot withstand the tension applied to a large number of tension members, it is an attempt to disperse the tension to a plurality of fixing members.

Problems with such a plurality of fixing members are as follows.
As shown in the figure, the length varies depending on the tension material group fixed to each fixing body.Therefore, when a larger load is applied after anchoring, a large load concentrates only on the tension material with a short length. Is to end up. That is, since each tensile member is made of steel, the tensile member expands each time a load is applied.
This elongation is large when the length of the tensile member is long, and small when it is short. When multiple fixing bodies are placed sequentially from the deep position to the shallow position in the drilling hole, the tension material applied to the fixing body located at the shallowest position is the shortest, and all tension materials are tensioned with the same force at the same time. It is the shortest tensile material that reaches the elongation limit. In other words, it means that only the shortest tensile material reaches the limit of elongation, and the other tensile materials have room for elongation. From now on, the load acting on the shortest tensile material will be larger than the others. This is when the rubber and steel ropes that allow elongation are tensioned at the same time,
This is the same phenomenon in which only steel ropes bear a large amount of tension, and rubber ropes bear only a small load for stretching. If tension is exceeded beyond this limit, only the load acting on the shortest tensile member will be significantly increased, resulting in exceeding the breaking load and breaking.

In order to solve such a problem, in order to compensate for the elongation of the tensile material, an elastic material such as rubber is interposed at the connecting portion of the tensile material to the fixing member, and the elastic material contracts to cause the tensile material to contract. A structure is adopted that reduces the burden of load even when the limit of elongation is reached.

[0005]

However, in the method of adopting the elastic material as described above, the thickness of the elastic material is changed depending on whether the tensile material is long or short. However, the workability of interposing the elastic material in the fixing portion is difficult and the workability is poor. Since the equipment used is complicated, the cost is high and the construction cost is high. Furthermore, the material and size of the elastic material must be calculated according to the magnitude of the tensile load and the elongation rate of the material of the tensile material, but even if a complicated calculation is performed, the function will be accurately performed in a complicated manner. I was worried.

An object of the present invention is to solve the above problems, and to provide an anchor having good workability, low construction cost, and high reliability that accurately exhibits its function.

[0007]

In the anchor according to the present invention, the tensile force applied to each tensile member having a different length is changed in advance, and even if an unexpected load is applied, the load acting on all the tensile members is The breaking load should not be exceeded.
The plurality of tension members form a plurality of tension members at different fixing positions. The number of lines may mean a plurality of lines, but may mean one line at a time. The tensile material groups are individually fixed in the drilled holes. Various fixing bodies can be used for fixing. For example, a permanent anchor in which a tension material is passed through a hard cylindrical fixing body having irregularities on its peripheral surface, and the tension material is held by a compression grip so as not to come off. However, various well-known fixing bodies such as a fixing body of a C-turn removing type anchor that has both ends reaching the ground as shown in the figure and hooks at a turn can be used.

Since fixing is performed separately for each group of tension members having different lengths, the fixing member is displaced in the depth direction and fixed in the drilled hole. The distance between the fixing positions of each tension member group is preferably 1.5 to 3 m. In addition, the length from the fixing position to the ground of the tensile member group fixed at the shallowest hole is preferably 6 m or more.
If the distance between the fixing positions of the tension members is too long, the difference in the tension force will be too large to effectively use the tension members to the limit, which is uneconomical. Further, even if the length from the tensile material group fixed at the shallowest to the ground is too short, it is uneconomical to similarly increase the difference in tension force.

The tensile force applied to each tensile material group is the largest applied to the tensile material group having the longest length, and the tensile force is close to the allowable design limit of the tensile material. As shown in FIG. 4, this is usually 60% of the breaking load of the tensile member, and the value is close to that. It is preferably 60% of the breaking load, and is adjusted in the range of 55% above and below 5%. In other tension material groups, the tension force is gradually reduced as the length becomes shorter,
The amount of reduction is about 10% of the breaking load. In other words, the tension force in the range of 45% up and down 5% of the breaking load is applied to the second tensile material group from the deepest, and the tension force in the range of 5% up and down 5% of the breaking load is applied to the third tensile group. give.

[0010]

[Action] For the anchor that has been given tension as described above,
When an increase in load occurs due to an unexpected situation, it acts in a dispersed manner on each tensile member. 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, the tension force of the longest tensile material increases by 10%, for example, the second longest tensile material increases by 10% and the third longest tensile material increases by 20%. become. 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 becomes the load that the longer tensile member bears as the load increases. Get closer. Finally, when the load carried by the longest tensile member reaches 80% of the breaking load, the load acting on other tensile members also becomes approximately 80%. As a result, a load that is nearly equal is distributed to all of the plurality of tension members. If the load is increased more than this, the short tensile members will receive a larger load, but at this point in time, each tensile member has already reached the yield load, so the elongation deformation will increase. , A large load difference does not occur for each tensile material,
There is practically 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. An example is a case where the present invention is implemented in a C-turn removing type anchor. In the figure, reference numeral 1 denotes a fixing body, which uses a semicircular hook portion 2 made of a casting and a plurality of fixing rods 3 made of deformed reinforcing bars protruding from the hooking portion 2. Three tension members a, b, c having different lengths are hooked on the three fixing members 1, respectively. In the embodiment, the tensile member group is composed of a single tensile member 4.
Is folded back at one place, and the folded back portion is hooked on the hook portion 2 of the fixing body 1. As the tensile member 4, a conventionally known tensile member can be used, but in the embodiment, the steel stranded wire is a tensile member 4.
Is used as. This steel stranded wire is passed through a sheath made of synthetic resin to enable free extension.

The anchor as described above is inserted into the drilled hole and fixed. Fixing body 1a with a longest tension material 4a
Is positioned deepest in the drilled hole 5, and the fixing member 1b to which the next longest tension member 4b is applied is positioned next deepest. The fixing member 1c to which the next longest tension member 4c is applied is positioned next deeper so that both ends of all the tension members 4a, 4b, and 4c reach the ground. At this time, the distance Lp between the folding positions of the tension members 4 is 3 m. Further, the length Lf from the folded position of the tension member 4c, which is the shallowest and fixed near the ground, to the ground is 6 m. In this state, a hardening material is injected into the drilled hole 5 to be hardened. In the example, cement milk 6 was injected as a hardening material.

Each tension member group is sequentially tensioned. The order of the tension may be arbitrary, but the tension member 4a having the longest length tensions at 60% of the breaking load. The tension force applied to the next longest tensile member 4b is 50% of the breaking load. The load applied to the shortest tensile member 4c is 40% of the breaking load. In such a state, the retaining wall 7 is fixed by the prestressing force.

When the load applied to the tensile member 4 is increased due to the bulging of the ground, the tensile members 4b and 4c having a shorter length have a smaller elongation than the tensile member 4a having a longer length, so that the rate of increase of the load is increased. high. This means that the originally applied loads are different, but the closer the loads are, the closer they are. When the load acting on the longest tensile member 4a reaches 80% of the breaking load, the other tensile members 4b and 4c
The loads acting on the two catch up and become almost equal. The following table 1 shows the numerical values obtained by the experiment in which this was performed.

[0015]

[Table 1]

According to the above table, when the distance Lp between the fixing positions for each tension member group is set to 3 m, and the length Lf from the fixing position of the shortest tension member 4c to the ground is 6 m, The load acting on the tensile members 4a, b, c is close to 80% of the breaking load.

FIG. 3 shows another embodiment of the present invention in which the tension members 4a, 4b, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4c, 4d, 4c, 4c, 4c, 4c, 4d, 4c, 4d, 4c, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4c, 4d, 4d, 4d, 4d, 4d, 6c, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6d, 6b, 6c, and 6d are shown. This is the case where the fixing units are arranged in a staggered manner. The tensile members 4a, 4b, and 4c are passed through the free length part sheath 8 and the fixing length part sheath 9 to form the drilled hole 5
The mortar 6 was inserted into the inside and outside of the sheaths 8 and 9 and fixed. Even in such anchors, the tension member 4
Since the lengths of a, b, and c are different, a tension force near the limit of the allowable design tension force is applied to the longest tension member 4a, and the tension force is gradually reduced and fixed to the other tension members 4b and 4c.

[0018]

The present invention has been made to solve the above problems, and the following effects can be obtained. The tension force is changed for each tension material group with different length, and the tension force of short tension material is made small beforehand, so even if an unexpected situation occurs after that and the load increases, the tension force acting on each tension material. Therefore, the load is not concentrated on a part of the tension material and the adhesion between the fixing body and the hardening material does not occur and the tension material does not break. It suffices to change the tension force for each tension material group having different lengths, and the same construction as that of the conventional anchor is sufficient, and its workability is extremely good. The construction can be the same as that of the conventional anchor, and since no extra member is required, it can be economically constructed. Although it seems uneconomical to apply a tension force smaller than the allowable design tension force to a tension material having a short length in advance, it is uneconomical, but because the workability is good, the construction is easy and economical. Since it is a simple and simple structure that only changes the tension applied, it can be expected that the design and calculation will be simplified and the functions will be surely exhibited.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an anchor according to the present invention.

FIG. 2 is an explanatory view showing a state in which a structure is fixed on a slope by an anchor.

FIG. 3 is a sectional view of an anchor of another embodiment.

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

[Explanation of symbols]

 1 Fixing body 2 Hooking part 3 Fixing rod 4 Tensile material 5 Drilling hole 6 Cement milk 7 Retaining wall 8 Free length sheath 9 Fixing length sheath

Claims (3)

[Claims] 1. A plurality of tensile members are divided into several groups, the length of the tensile members is made different for each group, and the tensile members having different lengths are slid in the drilling hole and separately. In the anchor anchored in, the tension force is applied to each tension material group, and the tension material group with the longest length is given a tension force near the limit of the allowable design tension force. Anchor characterized by sequentially reducing the tension applied to each. 2. The distance between the fixing positions of the tension members is 1.5.
The anchor according to claim 1, wherein the length from the fixing position of the tensile member group having the shortest length to the ground surface is 6 m or more. 3. A tensile member having the longest length is given a tension of about 60% of the breaking load of the tensile member, and a tensile member having a length shorter than that is applied in the order of decreasing length. The anchor according to claim 1 or 2, wherein the tension force is sequentially reduced by about 10% of the breaking load for each group.