JPH0721186B2 - 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, and more particularly to an anchor capable of obtaining a large fixing force.

[0002]

2. Description of the Related Art A tension member such as a PC steel wire is passed through an unbonded sheath, a portion passed through the unbonded sheath is used as a free length portion, and an exposed portion is used as a fixing length portion. Place a modified sheath. An anchor has been developed in which the tensile material is fixed by filling the inside and outside of the deformed sheath with the hardening material in the drill hole. The fixing long portion is fixed in the excavation hole by the hardening material, and the tension force applied to the tensile member acts as a tensile force on the fixing sheath as it is. The fixing sheath receives this tensile force due to the frictional resistance with the surrounding hardened material. Such anchors are called pull-type anchors.

[0003]

A problem with such an anchor is that the frictional resistance of the fixing portion does not actually work as designed. FIG. 6 shows the distribution of frictional resistance in the conventional anchor. When a tensile force is applied to a tensile member, an adhesive stress is generated in the tensile member, and a frictional resistance force is generated around the fixing sheath, which tends to increase in accordance with the tensile force. Actually, the resistance force does not increase, and the stress simply moves toward the bottom of the drill hole as shown in A to C of the figure. That is, in the case of C, the resistance force on the ground side of the fixing portion is substantially equal to 0, and a large resistance force τu is generated on the bottom side of the drill hole. At this time, a large amount of elongation concentrates on the portion where the resistance is gradually increasing, that is, the middle portion of the fixing sheath a in the figure. If this elongation increases, cracks b will occur in the fixing sheath.
May occur, permitting the ingress of water, and the tensile member may rust and break. As a result, the tensile member sometimes pulled out from the portion.

As described above, the fact that the frictional resistance force τu does not change regardless of the increase in the pulling force means that when the pulling force acts and the fixing sheath extends, the adhesion with the hardening material is cut off, and that portion is no longer present. It means that the resisting force does not act and the resisting force is obtained at the next adhesion part. This means that the fixing force does not increase even if the length of the fixing unit is increased. If the frictional resistance τu can be uniformly obtained from the entire length of the fixing portion, the fixing force becomes large and the anchor has higher reliability.

Further, the anchor considers the sliding surface of the natural ground in the design and positions the fixing portion deeper than the sliding surface.
The structure fixed to the anchor on the ground surface prevents the ground from collapsing due to this slip, but if the slip occurs deeper than the anchor anchorage, the anchor can no longer prevent collapse. Can not. For this reason, it is conceivable to bury the anchor deeper than the design, just in case, but generally at such a depth, the surrounding ground is hard rock, and the drilling hole is further dug into such ground. Is not an easy task, and construction costs will rise.

The present invention has been made in order to solve the above problems, and an anchor capable of obtaining a large fixing force without damaging the fixing portion and suppressing the construction cost at a low cost. The purpose is to provide.

[0007]

The anchor according to the present invention employs a deformed sheath made of synthetic resin which allows a certain degree of elongation as a fixing sheath. Polyethylene or the like can be adopted as the synthetic resin. The irregular shape means to have irregularities on the peripheral surface, and the frictional force is obtained by the irregularities. A plurality of tension members are arranged in the fixing sheath, and some of the tension members are offset from each other in the length direction of the fixing sheath. That is, the tension members displaced in the length direction are adapted to transmit the fixing force to different portions of the fixing sheath. In other words, the frictional resistance force of each tension member is not concentrated in one place, but is dispersed in the length direction of the fixing sheath to act. As a result, a large fixing force can be obtained from almost the entire length of the fixing sheath, and the fixing sheath is not damaged due to concentration of elongation.

The tension members that are displaced from each other in the lengthwise direction of the fixing sheath sometimes form a gap between the fixing long portions to allow the fixing sheath to extend. As a result, the fixing force of each tensile member displaced in the length direction is completely dispersed, and a better fixing force distribution can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on an embodiment shown in the drawings. First, in FIG. 1, 1 is a tensile material, and PC strands are used in the embodiment. The free length part of this tensile member 1 is an unbonded type,
It passes through the polyethylene sheath 2. The free length portions of the plurality of tension members 1 are passed through a free length sheath 3 made of synthetic resin. The fixing long portion of the tension member 1 is passed through the fixing sheath 4 while being exposed. Such an anchor is inserted into the excavation hole 5, and the curing material 6 is filled in the excavation hole 5 to fix the anchor.

As the fixing sheath 4, a deformed sheath made of synthetic resin is adopted. Polyethylene or the like can be used as the synthetic resin. Such a synthetic resin sheath has a property of allowing a certain degree of elongation when a prestressing force is applied to the tensile member 1. The irregular shape means that irregularities are formed on the peripheral surface.

FIG. 1 shows that some of the plurality of tension members 1 are exposed on the outermost surface side and fixed in the fixing sheath 4, and some other fixing members are exposed. The long portions are successively slid and fixed to the bottom side of the drilled hole 5. Assuming that the fixing length portions of the fixing sheath 4 in which the tension member 1 is exposed in the lengthwise direction are X, Y, and Z, respectively, tensile forces act individually and become the fixing force. In the embodiment shown in FIG. 1, as a method of applying a tension force, the longer tension member 1 which is the Z portion is first tensioned, and then the shorter tension member corresponding to Y · Z is tensioned sequentially. On the contrary, since the fixing sheath 4 allows a certain amount of elongation when a tensile force is applied, the tension force acting on one part of the fixing sheath 4 is not transmitted to the other part, and there is no particular structural problem. . With such a configuration, even when the anchor sheath 4 is actually used, the tensile forces of the respective portions X, Y, and Z are not transmitted to each other due to the anchor sheath 4 being stretched to some extent, and the anchor sheath functions as separate anchor sheaths. To do. This means that the fixed tensile member 1 is fixed by the frictional resistance force τu around it, and the frictional force distribution is as shown in the figure. That is, the frictional resistance τu of the fixing portion can be dispersed over a wide area over substantially the entire length of the fixing sheath. In other words, the magnitude of the stress τu does not change, but the area under stress is widened. The fixing power is remarkably increased. This makes it possible to realize a distribution of frictional resistance force that is close to ideal.

As shown in FIG. 2, a space α is provided between the portions X, Y and Z on which the tension members 1 are slid and fixed. The fixing sheath 4 allows a certain degree of extension, but the extension of the spacing α prevents the fixing forces of the respective portions X, Y, and Z from being transmitted to each other, so that the fixing force can be more reliably obtained from almost the entire length. . With such an anchor, when a prestressing force is applied, the prestressing forces acting on the respective portions X, Y, and Z will surely act separately. This spacing α prevents the elongation of the fixing portion from being absorbed and the elongation to be concentrated in any of the fixing portions.

FIG. 3 shows that a plurality of tension members 1 are slid and fixed in the longitudinal direction of the fixing sheath 4 one by one, and the diameter of the fixing sheath 4 on the bottom side of the excavation hole is more than on the ground side. Is a smaller one. With such an anchor,
It is possible to reduce the diameter of the excavation hole 5 on the bottom side.
For example, as shown in FIG. 4, when an anchor is buried deeper than a normal design to ensure safety, it is necessary to drill a deeper hole in hard rock, but the diameter of the anchoring sheath 4 becomes smaller. Therefore, the diameter of the excavation hole 5 can be reduced. Increasing the diameter of the excavation hole 5 leads to an increase in construction costs, and it is extremely advantageous in terms of cost to reduce the diameter when excavating into hard rock.

[0014]

The present invention has the above-mentioned structure and can obtain the following effects. In the fixing sheath, a plurality of tension members are slid and fixed in the lengthwise direction. Since the fixing sheath is made of a synthetic resin and is allowed to extend to some extent, the fixing force extends following the tensile force of each fixing portion, and the elongation does not concentrate at one point. Therefore, the fixing sheath will not be cracked or broken. Even when the deformed portion and the joint portion are integrally formed of synthetic resin, the attachment of the joint portion is broken and the joint portion is stretched to absorb the stretch of the fixing portion. The fixing sheath is made of synthetic resin that allows some elongation,
Since some of the tension materials are slid and fixed in the fixing sheath, the tension force applied to the tension material is transmitted to each part on the outer circumference separately, and the area where the frictional resistance works is increased. It becomes bigger and the fixing power becomes much larger. Therefore, it is possible to obtain a frictional force distribution close to the ideal. If the diameter of the anchoring sheath on the bottom side of the drill hole is made smaller than that on the ground side, the diameter can be reduced at the deep position of the drill hole, the cost for drilling the drill hole can be reduced, and the construction can be performed at low cost.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an anchor according to the present invention.

FIG. 2 is a partial cross-sectional view of another anchor.

FIG. 3 is a partial cross-sectional view of another anchor.

FIG. 4 is a cross-sectional view showing a state in which the construction is performed on a slope.

FIG. 5 is an overall view of an anchor.

FIG. 6 is an explanatory diagram of a conventional anchor.

[Explanation of symbols]

 1 Tensile material 2 Unbonded sheath 3 Free length sheath 4 Fixing sheath 5 Drilling hole 6 Hardened material

Claims (3)

[Claims] 1. An anchor in which a fixing sheath is disposed outside a fixing length portion of a plurality of tension members each having a free length portion and a fixing length portion, and a hardening material is filled inside and outside the fixing sheath, the fixing sheath is A deformed sheath made of synthetic resin that allows a certain amount of elongation in the length direction, and how many of the tension members in the fixing sheath are slid and fixed in the length direction of the fixing sheath. Characterized anchor. 2. The anchor according to claim 1, wherein the tension members that are displaced from each other in the lengthwise direction of the fixing sheath form a gap between the fixing long portions that allows the fixing sheath to extend. 3. The anchor according to claim 1, wherein a polyethylene sheath is adopted as the fixing sheath.