JPH044028Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to an earth anchor removal device.

``Conventional technology'' As a conventional removable earth anchor, a wedge with cutting blades on the outer periphery is fixed to the tip of a drawing steel material inserted into a sheath, and multiple tensile steel members are arranged around this wedge. When removing the anchor, the wedge is pulled up and the anchor body is crushed by the spreading action and the cutting action of the cutting blade, and then the tensile steel material is pulled out. An anchor that is arranged around a heating sheath, and when removing the anchor, oil and a heating wire are filled and inserted into the heating sheath, and the synthetic resin around the tensile steel material is melted by heating the oil, and then the tensile steel material is pulled out. Thermo-crusher anchors and the like are known in which a sheath is disposed within the anchor body, and when the anchor is removed, thermite is inserted into the sheath and ignited, causing the anchor body to be thermally fractured by the heat generated.

``Problems to be solved by the invention'' However, the anchor requires a special wedge and a jack with a considerable pulling force to pull it out, and the anchor also requires a synthetic resin coating, heated oil, and a special electric wire. Both methods required expensive equipment and materials for removal, such as hot wires, etc., and thermite and its igniter for anchors, and the installation and operation of these devices was time-consuming. .

``Means for solving the problem'' This invention aims to solve the above-mentioned conventional problem.
A plurality of tensile steel members are buried in an anchor body made of mortar or concrete at a distance from each other with their surfaces in contact with the anchor body, and the tensile steel members are connected to the tips of the tension steel members so as to be separated by a small tensile force. The present invention proposes an earth anchor removal device characterized by comprising a conductor, and a power supply device that connects an electrode terminal to the base end of an anchoring part of a tensile steel member connected by the conductor to supply electricity. .

"Effect of the invention" When electricity is applied to the electrode terminal connected to the base end of the anchoring part of each tensile steel material, the tensile steel material generates heat, and the surface layer of the surrounding mortar etc. is heated and becomes brittle, almost losing its adhesion to the tensile steel material. With,
A rapid temperature gradient occurs in the mortar around each tensile steel member, causing cracks and weakening the anchor body over a wide range.

Therefore, if a tensile load is applied to the tensile steel material by jacking or the like when removing the anchor, the tensile load will be extremely small (approximately 1 ton to 2 ton).
The anchor body can be easily pulled out and separated from the conductor, and the weakened anchor body can be easily destroyed.

``Example'' Below, an example of this invention shown in the drawings will be described. In an anchor body 1 made of mortar or concrete, a tensile steel material 2 made of stranded steel wire, a PC steel bar, etc. is in contact with the anchor body 1 with its surface. Several of them are buried.

Each tensile steel material 2 is arranged in an annular shape with a required spacing so as not to come into contact with each other by an annular separator 3 made of an insulating material such as synthetic resin and having an engaging recess on the outer periphery, and between the tip of each tensile steel material 2. is connected to the conductor 4, and by connecting the power terminals 6, 6 of the power supply device 5 to the base end of the anchoring part of the tensile steel material 2, a current can be passed between the two without having a lead wire. It's summery.

In order to ensure electrical connection with the tensile steel material 2 and ensure smooth flow of current, the conductor 4 is
It is preferable that at least the contact portion be made of a metal such as copper that is a good electrical conductor, but it does not necessarily have to be a good conductor as long as the connection is made well, and any material that can conduct electricity may be used.

The conductor 4 is configured to be easily separated from the tensile steel material 2 when it is drawn out.

As this detachable structure, for example, as shown in FIGS. 2 to 4, a conductive annular plate 4a is used.
A fixed piece 4 has a plurality of connecting terminals 4b formed by bending a conductive strip plate into a substantially cylindrical shape and protrudes between the connecting terminals 4b.
Fix by welding etc. at c, and connect each connecting terminal 4b.
Insert the tip of the tensile steel material 2 into the connecting terminal 4.
By caulking both ends of b and fastening them with relatively light frictional engagement, the tensile steel material 2 is configured to be pulled out from the connecting terminal 4b with a small tensile load.

In addition, as another means for making it possible to separate the conductor 4 from the tensile steel material 2, in addition to the above, a copper wire or the like is used as the conductor 4, and this is connected to the tip of each tensile steel material 2. The material itself may be cut by a small tensile load, or may be cut off by being melted by heat generated by energization after a required period of time has elapsed.

If necessary, a tapered cap 7 made of plastic or the like is attached to the tip of the second group of tensile steel materials to facilitate insertion of the assembled tensile steel material 2 and to protect the tips. Good too.

When removing the anchor configured as described above after use, connect the power terminals 6, 6 of the power supply device 5 to the base end of the anchoring part of each tensile steel member 2 connected by the conductor 4, and A predetermined current (for example, voltage 20 to 50 V, current 500 to 1000 A), preferably a high frequency current, is applied to the tensile steel material 2 with high electrical resistance.
generates heat.

In this state, the temperature is relatively high (e.g. 400℃~500℃)
By heating for approximately 30 to 40 minutes until it reaches a temperature of approximately It can be eliminated and each tensile steel material 2
A sharp temperature gradient is generated in the mortar, etc. around the anchor body 1, causing cracks, and the anchor body 1 is weakened over a wide range.

Therefore, if a tensile load is then applied to the tensile steel material 2 by jacking or the like, it can be easily pulled out with an extremely small tensile load (approximately 1 ton to 2 tons), and it can also be easily separated from the conductor 4. I can do it.

In addition, in order to pull out the tensile steel material 2 with a small load, it is sufficient that the surrounding mortar becomes brittle and the adhesion strength decreases, and it is not necessarily necessary for cracks to occur, but these cracks can be removed by removing the anchor. This is useful for facilitating the destruction of the anchor body 1 during the process.

Experimental example: Two PC steel bars with a diameter of 9 mm and a length of 1 m, 60 mm from the center.
An anchor specimen was created by placing the anchor specimens at intervals of
When a current of 20V and 500A was applied to the PC steel rod,
After 15 minutes had elapsed, the PC steel bar was heated to 400°C, at which point the current was turned off and a tensile load was applied to the PC steel bar.

As a result, the PC steel bar could be pulled out with a tensile load of 0.2 tons. Furthermore, when we examined the cross-sectional properties of the specimen, we found that numerous cracks had occurred in the mortar around the PC steel rod, and the mortar on the surface layer in contact with the PC steel rod had become brittle to the extent that it could be easily peeled off with an iron spatula. It was confirmed that

``Effects of the invention'' As described above, according to this invention, tensile steel is used as an electrical resistor to generate heat by passing an electric current through it, and the high temperature heating caused by this causes the mortar around the tensile steel to become brittle in a short period of time. In addition, since the conductor and the tensile steel material can be easily separated, the tensile steel material can be easily pulled out with an extremely small pulling force, and the removal work can be performed quickly and efficiently.

Further, since only a separator and a conductor are required as equipment attached to the tensile steel material, the structure can be extremely simple and inexpensive, and the processing cost and material cost are low, making it possible to reduce the construction cost.

In addition, in the anchor body left buried in the adjacent land, only conductors such as electric wires that were separated from the tensile steel members remain, and the mortar etc. around each of the multiple tensile steel members placed at intervals is brittle. Since it is weakened over a wide area by causing cracking and cracking, it can be easily destroyed when excavating adjacent land, etc., and can also be removed after destruction, without causing any hindrance to construction.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional side view showing an embodiment of this invention;
FIG. 2 is a front view showing an example of the conductor according to this invention, FIG. 3 is a side view of the same, and FIG. 4 is a partially enlarged front view showing a connected state of the conductor according to this invention. 1... Anchor body, 2... Tensile steel material, 3...
Separator, 4... Conductor, 5... Power supply device, 6
...Electrode terminal.

Claims (1)

[Scope of utility model registration request] A plurality of tensile steel members are buried in an anchor body made of mortar or concrete at a distance from each other with their surfaces in contact with the anchor body, and the tensile steel members are connected to the tips of the tension steel members so as to be separated by a small tensile force. 1. An earth anchor removal device comprising: a conductor; and a power supply device configured to connect an electrode terminal to a base end of a fixing portion of a tensile steel material connected by the conductor to supply electricity.