JP2013053494A - Electric-discharge fracturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to unfailingly create wide-gap cracks continuously extending in specific directions in a to-be-crushed object like a base concrete of an architectural structure by use of electric discharge so that the to-be-crushed object can be easily fractured.SOLUTION: A plurality of electrode-insertion holes 11 are drilled into a to-be-crushed object 10, and coaxial electrodes arranged with insulators are inserted into the electrode-insertion holes for electric discharge. Before fracturing the to-be-crushed object 10 by shock waves produced by the electric discharge, the plurality of electrode-insertion holes 11 are linearly positioned, and at least two vertical grooves 13 are formed on the side face of an upper face 10a on which the electrode-insertion holes 11 have been drilled, in such a way that the grooves' cutting depths are less than the distance L between a side face 10b and the electrode-insertion hole 11, and that the vertical grooves 13 are perpendicular to both the side face and the upper face 10a, in order to induce cracks along the vertical grooves 13 so that the to-be-crushed object 10 is fractured.

Description

  The present invention relates to a method of crushing an object to be crushed, such as foundation concrete of a building, by a shock wave due to electric discharge, and in particular, to induce a crack continuously extending in a specific direction on the object to be crushed. It is related with the method of crushing.

Conventionally, a discharge crushing method using a discharge crushing device is known as a method for dismantling a concrete structure such as a foundation concrete or a pier of a building (see, for example, Patent Document 1).
As shown in FIG. 10 (a), the electric discharge crusher includes a rod-shaped center electrode 21a, a cylindrical insulator 21k covering the outer periphery of the center electrode 21a, and an outer peripheral electrode 21b provided on the outer periphery of the insulator 21k. The provided coaxial electrode 21, a power source 22a and a large-capacitance capacitor 22b, a pulse power source 22 that supplies a large current to the coaxial electrode 21, a coaxial cable 23 that connects the coaxial electrode 21 and the pulse power source 22, and a connector 24 With. The central electrode 21a and the outer peripheral electrode 21b of the coaxial electrode 21 of the discharge crushing device 20 are connected to one electrode plate and the other electrode plate of the large-capacitance capacitor 22b via the switch 22p, respectively, and the large-capacitance capacitor 22b is connected by the switch 22p. And the coaxial electrode 21 are electrically connected to discharge the charge charged in the large-capacitance capacitor 22b between the center electrode 21a and the outer peripheral electrode 21b of the coaxial electrode 21 with the switch 22q closed. A shock wave is generated in the vicinity, and a crack is generated in the concrete around the coaxial electrode 21.

Next, a method for crushing a crushing object 50 such as a foundation concrete of a building will be described with reference to FIGS.
First, a deep groove 51 is formed on the upper surface 50a of the crushing object 50 using a wire saw or the like, and the crushing object 50 is divided into a plurality of regions as indicated by R1, R2, R3,. A plurality of electrode insertion holes 52 are drilled in each region, an electrolytic solution 53 such as water is poured into the electrode insertion holes 52, and then the coaxial electrode 21 disposed through an insulator is inserted into the electrode insertion holes 52. A large current is applied to the coaxial electrode 21 to discharge it, and the concrete between the electrode insertion hole 52 and the groove surface of the deep groove 51 is cracked, and then the cracked portion is removed from a rock drill such as a small breaker. Crush using Thereby, compared with the case where it crushes using crushers, such as the conventional breakers, and rock drills, such as a call pick hammer (pick), the crushing object 50 can be crushed efficiently. Note that some concrete such as concrete near the electrode insertion hole 52 and concrete near the deep groove 51 is directly crushed by impact (for example, see Patent Document 2).
In addition, when the object to be crushed is a reinforced concrete structure, an incision groove deeper than the position where the reinforcing bar on the outer peripheral surface is arranged is formed, and an electrode insertion hole is provided in a region surrounded by the deep groove and the incision groove. A coaxial electrode is inserted for discharge. In this way, by dividing the reinforcing bar with the cut groove, the reinforcing bar also vibrates and a part of the reinforcing bar is broken by the shock wave, so that even if the object to be crushed is a reinforced concrete structure, it can be easily crushed ( For example, see Patent Document 3).
In addition, as a method of cutting the object to be crushed into a predetermined size, a method is known in which a wire saw is inserted through a wire insertion hole formed by a boring device or the like and the wire saw is driven to cut the object to be crushed. (For example, see Patent Document 4).

JP 2003-320268 A Japanese Patent No. 4727256 JP 2006-207322 A Japanese Patent Laid-Open No. 5-19697

However, since the conventional electric discharge crushing method aims to crush the crushing object 50 finely, the number of electrode insertion holes 52 must be increased. As a result, formation of deep grooves 51 and electrode insertion holes It took time to drill 52 holes.
In addition, when the size of the crushed material is small, not only is the generated dust increased and the storage rate of the crushed material is lowered, but it is also difficult to collect and store or transport the crushed material.
Therefore, it is conceivable to increase the size of the crushed material by reducing the number of the electrode insertion holes 52. However, if the number of the electrode insertion holes 52 is reduced, the occurrence of cracks due to discharge is reduced. It was difficult to sufficiently crush the object 50.
On the other hand, the method using a wire saw not only requires a number of wire insertion holes to be drilled in advance, but also has a problem that there are many secondary wastes such as waste liquid and sludge during cutting.

  The present invention has been made in view of conventional problems, and reliably generates a large crack in a crushing object such as a foundation concrete of a building, which is continuously extended in a specific direction by electric discharge. It aims at providing the method of crushing a crushing object easily.

The present invention provides a wire in which a plurality of electrode insertion holes are drilled in an object to be crushed, and a coaxial electrode disposed via an insulator or a pair of electrodes are disposed to face each other in the electrode insertion hole. An electric discharge crushing method for inserting and discharging an electrode and crushing the object to be crushed by a shock wave generated by the discharge, wherein the plurality of electrode insertion holes are linearly arranged and the electrode insertion holes are drilled At least two vertical grooves are formed on the side surface of the object to be crushed perpendicular to the side surface and the surface where the electrode insertion hole is cut, and the depth of cut is shorter than the distance from the side surface to the electrode insertion hole. Thus, cracks along the longitudinal groove are induced.
In this manner, the side surface of the surface of the object to be crushed with the electrode insertion hole is provided with a vertical groove extending from the side surface in a direction perpendicular to the arrangement direction of the electrode insertion hole, and the electrode insertion holes arranged linearly Since the coaxial electrode is inserted and discharged, a linear crack with a large gap along the longitudinal groove can be generated. Therefore, compared with the case of forming a deep groove for forming a conventional free surface, the work of forming the groove is less and the region surrounded by the electrode insertion hole and the vertical groove can be reliably crushed in a short period of time. Work efficiency can be greatly improved. Moreover, in this method, since the direction of cracking can be controlled, a large lump of crushed material can be obtained, so that the crushed material can be easily transported. In addition, since the grooves to be formed are shallow and narrow, not only the amount of dust generated is small and the working environment is improved, but the size of the crushed material can be freely determined, so a larger mass than in the past can be formed. It is also possible to obtain the crushed material.
Further, the present invention is characterized in that the electrode insertion hole is positioned on an extension line in the depth direction of each longitudinal groove.
Thereby, since the crack of the direction perpendicular | vertical to the arrangement direction of an electrode insertion hole can be induced reliably, the substantially rectangular parallelepiped crushed material can be obtained reliably. Therefore, the collection | recovery operation | work and conveyance operation | work of a crushed material become still easier.

In the present invention, a shallow groove that is 1/3 or less of the depth of the electrode insertion hole connecting the opening of the electrode insertion hole is formed to induce cracks along the shallow groove. Features.
In this way, by inserting a coaxial electrode into a plurality of electrode insertion holes whose openings are connected by shallow grooves and discharging them, in addition to cracks in the depth direction of the vertical grooves, the arrangement direction of the electrode insertion holes is also increased. Since it is possible to generate a linear crack with a large gap along the shallow groove, it is possible to easily obtain a block-shaped crushed material having a uniform size, and to more easily store and transport the crushed material. be able to.

Further, the present invention is parallel to the surface where the electrode insertion hole is drilled, below the hole bottom of the electrode insertion hole on the side surface of the surface of the object to be crushed in which the electrode insertion hole is drilled, and A lateral groove is formed in which the cutting depth reaches just below the bottom of the electrode insertion hole.
By providing such a lateral groove, it is possible to efficiently crush a thick crushing object with a thickness (distance between the surface where the electrode insertion hole of the crushing object is drilled and the opposite surface) and a substantially rectangular parallelepiped shape. Since it is possible to obtain a crushed material, it becomes easier to store and transport the crushed material.

  The summary of the invention does not list all necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

It is a perspective view which shows the electric discharge crushing method which concerns on this Embodiment 1. FIG. It is a top view which shows the electric discharge crushing method which concerns on this Embodiment 1. FIG. It is a figure which shows the discharge state by a coaxial electrode. It is a figure which shows the outline | summary of the generation | occurrence | production state of a crack. It is a figure which shows an example of the peeling method of a crushed material. It is a figure which shows the electric discharge crushing method which concerns on this Embodiment 2. FIG. It is a figure which shows the outline | summary of the generation | occurrence | production state of a crack. It is a figure which shows an example of the biological body shielding wall of a nuclear power station, and the conventional dismantling method of the biological body shielding wall. It is a figure which shows the dismantling method of the biological shielding wall by this invention. It is a figure which shows the conventional electric discharge crushing method.

  Hereinafter, the present invention will be described in detail through embodiments, but the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing a discharge crushing method according to Embodiment 1, and FIG. 2 is a plan view.
In this example, a rectangular parallelepiped concrete body (hereinafter referred to as a crushing object) 10 having a length a of 5500 mm, a width b of 2000 mm, and a thickness c of 1500 mm is used as the coaxial electrode 21 shown in FIG. A method for crushing using the provided electric discharge crushing apparatus 20 will be described.
First, a plurality of electrode insertion holes 11 for inserting coaxial electrodes of a discharge crushing device are drilled at a pitch of 400 mm at a position L = 500 mm away from the side surface 10b on one side of the upper surface 10a of the crushing object 10. Thereby, the electrode insertion hole 11 can be arrange | positioned along the ridgeline which the upper surface 10a and the side surface 10b make in the position spaced apart from the side surface 10b of the upper surface 10a.
In this example, because the discharge is performed using the coaxial electrode 21 having an outer diameter of 50 mmφ, the diameter of each electrode insertion hole 11 is about 75 mmφ and the depth D is about 1000 mm. The electrode insertion hole 11 can be drilled using, for example, a well-known core drill.
Next, the lateral groove 12 is formed in the side surface 10b.
The lateral groove 12 is a groove parallel to the upper surface 10a of the object 10 to be crushed. In this example, a wall saw is used, and the distance from the upper surface 10a is longer than the depth D of the electrode insertion hole 11 (for example, from the upper surface 10a). A slit-like lateral groove 12 having a width of 5 mm and a depth of L = 500 mm was formed at a position (h = 1200 mm). The wall saw forms a slit by cutting an object while rotating a disk-shaped rotary blade, and can form a lateral groove 12 having a narrow groove width compared to the case of using a wire saw. .
The horizontal groove 12 regulates the thickness of the crushed object, and when the object 10 to be crushed is a reinforced concrete structure, the vertical groove is cut by the horizontal groove 12, so Stripping can be easily performed.

On the other hand, the vertical groove 13 is a slit-shaped groove having a width of 5 mm and a depth of 150 mm provided on the side surface 10b in which the horizontal groove 12 is formed so as to extend in a direction perpendicular to the horizontal groove 12, and one end is formed on the upper surface 10a. Open and the other end opens into the lateral groove 12. The vertical groove 13 is also formed by using a wall saw similarly to the horizontal groove 12. Since the depth of the vertical groove 13 is k = 150 mm, the end (groove bottom) of the vertical groove 13 does not reach the electrode insertion hole 11 when viewed from the upper surface of the object 10 to be crushed.
In this example, each vertical groove 13 is formed so that the electrode insertion hole 11 is positioned on an extension line in the depth direction of each vertical groove 13. Therefore, the interval P between the longitudinal grooves is an integral multiple (here, 3 times) the pitch of the electrode insertion holes 11.
In this example, the vertical groove 13 is formed after the step of forming the horizontal groove 12.
Hereinafter, a region surrounded by the upper surface 10a, a surface parallel to the side surface 10b and including the arrangement direction of the electrode insertion holes 11, and the side surface 10b (free surface) is referred to as a crushing scheduled region R.
After the formation of the drill holes of the electrode insertion holes 11 and the horizontal grooves 12 and the vertical grooves 13 is finished, an electrolyte solution 14 such as water is injected into each electrode insertion hole 11 as shown in FIG. The coaxial electrode 21 is inserted and discharged, and the object 10 to be crushed is cracked.
The discharge may be performed sequentially for each electrode insertion hole 11 or simultaneously.
Further, the number of discharges may be one or more. In addition, when the discharge is performed a plurality of times, the second and subsequent discharges may be performed at the bottom of the electrode insertion hole 11 or at a position higher than the bottom of the hole as shown by the broken line in FIG. May be.

When the vertical groove 13 is formed such that the electrode insertion hole 11 is on the extension line in the depth direction of the vertical groove 13 as in this example, the electrode insertion holes 11 are connected to each other as shown in FIG. In addition to the broken line-shaped crack C _k generated in FIG. 2, a linear crack C _m having a large gap connecting the longitudinal groove 13 and the electrode insertion hole 11 is generated, so that the shape of the crushed material can be easily aligned in a substantially rectangular parallelepiped shape. Therefore, a block-shaped crushed material having a uniform size can be obtained with certainty.
In addition, when the object 10 to be crushed is a reinforced concrete structure, the horizontal bars are cut by the vertical groove 13, so that the object 10 to be crushed and the crushed object can be peeled off easily.
Even if the electrode insertion hole 11 is not on the extension line of the vertical groove 13, the vertical groove 13 is a linear crack extending in a direction perpendicular to the extension direction of the electrode insertion hole 11, as shown in FIG. It is possible to induce C _j . When there is no vertical groove 13, this crack C _j often does not reach the electrode insertion hole 11, but a broken line crack C C is also formed between the end of the crack C _j and the electrode insertion hole 11 due to discharge. _{Since k} is generated, a crack connecting the vertical groove 13 and the electrode insertion hole 11 can be induced without the electrode insertion hole 11 on the extension line of the vertical groove 13. However, the gap between the crack C _{j and} the crack C _k is smaller than the straight crack gap connecting the vertical groove 13 and the electrode insertion hole 11 in this example, so that the crushed material can be easily peeled off. As in this example, each vertical groove 13 is preferably formed so that the electrode insertion hole 11 is positioned on the extension line in the depth direction of each vertical groove 13.
In order to simplify the description, the cracks C _k , C _n , and C _j in FIGS. 4A and 4B and the forms of the cracks C _m and C _n in FIG. This is shown schematically.

After the cracks C _k and C _n are generated in the object 10 to be crushed, as shown in FIG. 5, a crack C _{k in the} crushed area R is used by using a heavy machine 29 such as a breaker or a hammer type hydraulic crusher. , strip the crushed material G to a portion surrounded by C _n is crushed to beat on the side surface 10b side.
In the planned crushing region R after the discharge, it is surrounded by a broken line crack C _k generated so as to connect the electrode insertion holes 11 and a linear crack C _m having a large gap connecting the vertical groove 13 and the electrode insertion hole 11. Since the bonded concrete is extremely weakly bonded to the surrounding concrete, the crushed material G made of concrete blocks surrounded by the cracks C _k and C _m can be easily peeled off from the object 10 to be crushed.
The stripped crushed material G has a thickness equal to the depth h of the lateral groove 12, a length equal to the distance P between the vertical grooves 13, and a width substantially equal to the distance L from the side surface 10 b to the electrode insertion hole 11. Because it is a large block of almost the same size, for example, if the crushed crushed material G is lifted and stored in a rectangular container and transported, the crushed material can be collected and transported easily. it can.
After all the crushed material G in the planned crushing region R has been peeled off, the peeled surface is defined as a new side surface 10b ′ (see FIG. 5), and the crushed material G is removed from the step of drilling the electrode insertion hole. By repeating the operations up to the step of taking, the operation of crushing the concrete between the newly excavated electrode insertion holes 11 and the new side surface 10b ′ is repeated. In addition, you may provide the electrode insertion hole 11 of parts other than the crushing plan area | region R previously at the beginning of a process.

In the first embodiment, the crushed object 10 is a rectangular parallelepiped concrete body. However, the shape of the crushed object 10 is not limited to this, and other shapes such as an L-shaped concrete body in a top view are used. There may be. In this case, it is preferable that the arrangement direction of the electrode insertion holes 11 is the same as the direction of the side surface to be crushed and peeled off.
In the above example, the electrode insertion holes 11 having a diameter of about 72 mmφ and a depth of about 100 mm are drilled at a pitch of 400 mm at a position 500 mm away from the side surface 10 b side of the crushing object 10. The dimensions, position, pitch, and the like are not limited thereto, and may be set as appropriate according to the type of the coaxial electrode 21 to be inserted, the strength and thickness of the crushing object 10 to be disassembled, and the like.
In the above example, the electrode insertion holes 11 are arranged in a straight line, but may be arranged in a polygonal line or a curved line.
Further, the lateral groove 12 may be omitted when the object 10 to be crushed is thin, but the concrete on the lower end surface of the object 10 to be crushed is edged with the surrounding concrete by the lateral groove 12 and the crushed object is peeled off. Therefore, it is preferable to provide the lateral groove 12.
In addition, since the generation amount of dust increases when the width of the horizontal groove 12 or the vertical groove 13 is increased, it is preferably 15 mm or less, and more preferably 10 mm or less.
In the above example, the interval between the vertical grooves 13 is larger than the distance between the adjacent electrode insertion holes 11, but a larger number may be provided smaller than the distance between the electrode insertion holes 11. However, if the pitch of the vertical grooves 13 is reduced, the strain is dispersed and cracks cannot be efficiently guided to the vertical grooves 13. Therefore, the pitch of the vertical grooves 13 is set to 1/2 or more of the distance between the adjacent electrode insertion holes 11. It is preferable.
Moreover, in the said example, although the discharge crushing apparatus 20 provided with the coaxial electrode 21 was used, you may use the discharge crushing apparatus provided with the wire electrode which has arrange | positioned so that a pair of electrode may mutually oppose as a discharge electrode.

Embodiment 2. FIG.
FIG. 6 is a diagram showing the second embodiment.
In the electric discharge crushing method of this example, in addition to the horizontal groove 12 and the vertical groove 13 of the first embodiment, a shallow groove 15 that connects the openings of the electrode insertion holes 11 is formed in the crushing object 10, thereby inserting an electrode. A crack having a large gap is also generated in the arrangement direction of the holes 11, and thereby, a block-like crushed material having a substantially rectangular parallelepiped shape can be obtained.
The shallow groove 15 is a slit-like groove whose width is 1/4 or less of the diameter of the electrode insertion hole 11 and whose depth is 1/3 or less of the depth of the electrode insertion hole, and is formed using a wall saw. .
In this example, the shallow groove 15 has a width of 5 mm and a depth of 150 mm. The shallow groove 15 may be terminated in the upper surface 10a, or may be opened in the side surface 10c on the side orthogonal to the side surface 10b.
In this example, since the shallow groove 15 that connects the opening of the electrode insertion hole 11 is formed, the crushing object 10 after discharge has an electrode insertion hole as shown in FIGS. 4 (a) and 4 (b). A plurality of broken line cracks C _k from 11 to the side surface 10 b where the lateral groove 12 is provided, and a linear crack C _n having a gap larger than the crack C _k along the shallow groove 15 are generated.
By the way, in place of the shallow groove 15, it may be possible to induce a crack by providing a guide hole having the same shape as the electrode insert hole 11 between the adjacent electrode insert holes 11, 11. Even if it is discharged, a broken line-shaped crack C _k similar to that shown in FIGS. 4A and 4B is generated, but a linear crack with a large gap as in this example could not be induced.
Therefore, it can be seen that in order to generate cracks in a large gap along the arrangement direction of the electrode insertion holes 11, it is necessary to form the shallow grooves 15 that connect the openings of the electrode insertion holes 11 as in this example. .

Moreover, in the electric discharge crushing method of the present invention, the crushing boundary can be regulated by the drilling position of the electrode insertion hole 11 or the formation position of the vertical groove 13, so that it is suitably used for dismantling the biological shielding wall of a nuclear power plant. be able to.
Conventionally, as shown in FIG. 8, the dismantling of the biological shielding wall is performed along a boundary K between the portion considered to be activated and the portion assumed not to be activated of the side wall portion 30 of the biological shielding wall. A vertical hole 31 is formed in a boring device or the like, a cut surface Z is formed by a wire saw (not shown) using the vertical hole 31, and the activated portion 30A is cut into blocks of a predetermined size. The wire saw method was used.
By the way, the dismantling of the biological shielding wall, for example, has an extremely large outer diameter of 25000 mm and an inner diameter of 21000 mm. Therefore, as shown in FIG. The portion 30A is divided into a plurality of regions 30N such that the divided region becomes a substantially trapezoidal prism as viewed from above, for example, the circumferential direction is divided into 12 parts. If the crushing method at the time of discharge is applied, each region 30N can be easily crushed as in the first and second embodiments.
Specifically, as shown in FIG. 9 (b), a region 30N that is supposed to be activated divided into a substantially trapezoidal shape when viewed from above, and a portion 30B that is not activated that is the outer peripheral portion thereof. A plurality of electrode insertion holes 11 are arranged along a boundary K between the electrode insertion holes 11, shallow grooves 15 connecting the openings of the electrode insertion holes 11 are formed, and further, lateral grooves 12 and vertical grooves 13 are formed to be crushed. Determine the area. Note that the vertical groove 13 is provided along the boundary of the adjacent region 30N that is supposed to be activated.
Then, if the coaxial electrode 21 is inserted into the drilled electrode insertion hole 11 to generate cracks along the shallow groove 15 and the longitudinal groove 13, the region 30N that is supposed to be activated is defined as the boundary 30N. K can be reliably separated and crushed by K, and the activated region 30N can be crushed into blocks of substantially the same size and recovered.
As described above, when the electric discharge crushing method of the present invention is applied to the dismantling of the biological shielding wall, it can be disassembled earlier than the wire saw method, and the waste liquid at the time of cutting, which was a drawback of the wire saw method. And secondary waste such as sludge can be greatly reduced.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the embodiment. It is apparent from the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  According to the present invention, since large cracks can be reliably generated in an object to be crushed such as foundation concrete of a building, it is possible to easily dismantle the foundation concrete or the like of a building. In addition, since a large crushed crushed material can be obtained, the crushed material can be collected and transported easily.

10 object to be crushed, 11 electrode insertion hole, 12 transverse groove, 13 longitudinal groove, 14 electrolyte,
15 shallow groove, 20 discharge crushing device, 21 coaxial electrode, 22 pulse power source,
23 Coaxial cable, 24 connectors, 29 heavy machinery.

Claims (4)

A plurality of electrode insertion holes are drilled in the object to be crushed, and a coaxial electrode arranged via an insulator or a wire electrode arranged with a pair of electrodes facing each other is inserted into the electrode insertion hole. A discharge crushing method of crushing the crushing object by a shock wave caused by the discharge,
The plurality of electrode insertion holes are arranged in a line, and the side surface of the object to be crushed in which the electrode insertion holes are drilled are orthogonal to the side in which the side surfaces and the electrode insertion holes are drilled. A discharge crushing method, wherein at least two vertical grooves shorter than the distance from the side surface to the electrode insertion hole are formed to induce cracks along the vertical grooves.   The discharge crushing method according to claim 1, wherein the electrode insertion hole is located on an extension line in a depth direction of each vertical groove.   The shallow groove which is 1/3 or less of the depth of the said electrode insertion hole which connects the opening part of the said electrode insertion hole was formed, and the crack along the said shallow groove was induced. Or the electric discharge crushing method of Claim 2. Below the hole bottom of the electrode insertion hole on the side of the surface of the object to be crushed in which the electrode insertion hole has been drilled, parallel to the surface in which the electrode insertion hole has been drilled, and the depth of cut is The discharge crushing method according to any one of claims 1 to 3, wherein a lateral groove reaching just below the bottom of the electrode insertion hole is formed.

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