JP2004293260A - Explosive demolition method for reinforced concrete structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for safely and efficiently demolishing a structure by labor saving for work, and facilitating control of an area crushed by explosion in the method for demolishing the reinforced concrete structure by explosion. <P>SOLUTION: Boundary grooves 21, 22, 23, 24, and 25 are cut from a surface of the structure in a boundary part between an area 13 crushed by explosion and an area 14 left without crushing of the reinforced concrete structure 3. These grooves are formed in the depth for exposing a reinforcement arranged in the structure, and the reinforcement is cut in these grooves. A vertical directional groove 28 is cut at a prescribed interval in the crushing area, and a hoop is cut in these grooves. Charge holes 41 and 42 are bored in the crushing area 13 of the structure, and an explosive is charged and exploded in these charge holes. The reinforcement cut in the grooves may be the whole of the exposed reinforcement, and may be left without cutting a part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of dismantling a reinforced concrete structure by blasting, and provides a method of dismantling the structure safely and efficiently, while saving labor and facilitating control of a crushing region by blasting. .
[0002]
[Prior art]
When a reinforced concrete structure is aged or its usability and load resistance are reduced, it becomes necessary to dismantle and remove the structure. One of the dismantling methods is a blasting dismantling method. In this method, an explosive is loaded into a structure, the structure is crushed by blasting, and then removed.
[0003]
When the structure to be demolished is constructed higher than the ground surface, such as a pier, for example, it is an efficient dismantling method to collapse by blasting. At this time, the structure is to be overturned in a preset direction in response to requests for safety and workability, and it is necessary to crush a predetermined range of the structure accurately. For this reason, a charge hole is drilled at a predetermined location in the area to be crushed, a suitable portion of the structure is crushed by loading and exploding with an appropriate explosive, and the structure falls down in a predetermined direction due to its own weight. A technique is disclosed (Non-Patent Document 1).
[0004]
If such a dismantling method using blasting is employed, the structure can be overturned and disassembled in a short time, so that continuous noise and vibration can be avoided. Moreover, since it can fall over in a short time, not only work efficiency is good, but it is excellent in work safety by being able to carry out the removal work on the ground after the fall. This also leads to a reduction in construction costs. In view of such excellent points, a demolition method by blasting has attracted attention.
[0005]
[Non-Patent Document 1]
Nikkei Construction, 2003.1.10, p. 30-p. 34
[0006]
[Problems to be solved by the invention]
However, the disassembly method as described above has the following problems that are desired to be solved.
In general, reinforcing bars embedded in concrete structures are not easily cut by blasting, and piers and the like on which many reinforcing bars are arranged are less likely to be crushed by blasting. For this reason, it is necessary to cut or remove the reinforcing bars that become obstacles to crushing in advance. In the technique described in the above-mentioned document (Non-Patent Document 1), concrete is cut to the depth where the reinforcing bar is embedded, and the reinforcing bar is exposed and removed or cut.
[0007]
However, in such a method, it is necessary to cut the concrete of the so-called cover part in a wide range until the rebar embedded in the pier appears on the surface of the structure, which requires a lot of labor and cost. become. On the other hand, if an attempt is made to explode with rebars embedded, a large amount of explosives may be required, or as expected, crushing will not occur and subsequent operations may become difficult.
[0008]
In addition, in order to cause a high structure such as a bridge pier to fall in a predetermined direction, it is necessary to crush a predetermined range accurately. In other words, it is possible to reliably crush the area sufficient to cause a fall and to leave a part of the cross section of the structure without crushing, so that this part can serve as a fulcrum for a fall and control the fall in the correct direction. It becomes possible to do. Therefore, in the pier to be blasted, it is necessary to accurately distinguish the region where the concrete restraint by the reinforcing bars is released from the region where the reinforcing force of the reinforcing bars is maintained, and to cut or remove the reinforcing bars.
[0009]
Furthermore, considering the removal work efficiency after the pier falls due to blasting, it is desirable that the concrete block after blasting is crushed to an appropriate size, and it is better not to completely release the binding force of the reinforcing bars on the concrete In some cases. In other words, when the binding force of the reinforcing bars is completely released, much of the blasting energy is released to the outside, and the concrete is not finely crushed. Due to the moderate restraint by the reinforcing bars, the energy of the blasting is transmitted to the concrete, and the concrete is crushed small enough to facilitate later processing.
[0010]
The invention according to the present application has been made in view of the circumstances as described above, and its purpose is to increase work efficiency and shorten the work period, and to easily control the crushing area by blasting, and to improve work efficiency and work safety. It is to provide a method for blasting and dismantling reinforced concrete structures with high properties.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is to cut a boundary groove from the surface of the structure at the boundary between the region to be crushed by the explosion of the reinforced concrete structure and the region to be left without being crushed. The boundary groove has a depth at which a reinforcing bar disposed in the structure is exposed, the reinforcing bar is cut in the boundary groove, and a charge hole is formed in a region where the structure is to be crushed; Provided is a method for blasting and dismantling a reinforced concrete structure, wherein the charge hole is loaded with an explosive and blasted.
[0012]
In this dismantling method, the rebar is cut in a groove cut at the boundary between the area to be crushed by blasting and the area to be left unbroken, and the energy of blasting by the explosive loaded in the area to be crushed is Only the area to be crushed, released at the rebar cutting part, is crushed appropriately. Therefore, it is possible to accurately control the area to be left without being crushed and the area to be crushed.
Moreover, the concrete cutting forms a groove, and the depth of the cutting is sufficient to expose the reinforcing bar to be cut. Therefore, the predetermined region can be appropriately crushed with a small amount of cutting, and the labor for cutting the concrete can be greatly reduced.
Furthermore, since only a part of the region to be crushed is cut into a groove shape, the hole for the charge is made from a smooth surface that is not cut, and the depth of the hole can be accurately grasped. From this, it is possible to load the explosive at an accurate position, and to easily control the effect of the explosion.
[0013]
According to a second aspect of the present invention, in the method for blasting and dismantling a reinforced concrete structure according to the first aspect, an intermediate groove having a depth reaching the reinforcing bar is cut at a predetermined interval in the region to be crushed. The rebar is cut in the intermediate groove.
[0014]
In the above dismantling method, the reinforcing bars are cut in intermediate grooves cut at regular intervals in the region to be crushed of the structure, so that the reinforcement of the reinforcing bars is reduced and crushing due to blasting is likely to occur. By appropriately setting the interval between the intermediate grooves, it is possible to control the crushing state, and it is possible to appropriately crush only a predetermined region.
Further, the intermediate groove may be cut to a depth at which the reinforcing bar is exposed, and the restraint of the reinforcing bar can be appropriately released with a small amount of cutting.
[0015]
The invention according to claim 3 is the method for blasting and dismantling a reinforced concrete structure according to claim 1 or 2, wherein the intermediate grooves provided at predetermined intervals in the region to be crushed are disposed in the concrete. It is assumed that the outermost reinforcing bar is cut in such a direction that it can be cut.
[0016]
In a reinforced concrete structure, a main reinforcing bar and a distribution reinforcing bar or a band reinforcing bar are generally embedded. For example, a pier is embedded with a reinforcing bar embedded in the axial direction of the pier, that is, a main reinforcing bar, and a reinforcing bar horizontally disposed outside thereof, that is, a reinforcing bar. In such a structure, the outer reinforcing bar restrains the inner reinforcing bar from being pushed outward, and the outer reinforcing bar is cut at a predetermined interval, whereby the pressure of the explosion generated in the concrete at the time of blasting. On the other hand, the restraint of the reinforcing bars can be greatly released.
Further, in this dismantling method, the rebar restraint can be released in a wide range even if there are few intermediate grooves to be cut in the region to be crushed, and the cost of concrete cutting can be reduced.
[0017]
According to a fourth aspect of the present invention, in the method for blasting and dismantling a reinforced concrete structure according to the first, second, or third aspect, a part of the reinforcing bar exposed in the boundary groove or the intermediate groove is cut. The rest shall be left uncut.
[0018]
In this dismantling method, only a part of the reinforcing bar exposed in the groove is cut and the rest is maintained as it is, so that the restraining force of the reinforcing bar against the concrete can be adjusted. That is, by appropriately setting the amount of reinforcing bars to be cut and uncut, the level of crushing by blasting can be adjusted while taking into account the size of the structure to be dismantled and the amount of explosive to be loaded. Thereby, the magnitude | size of the concrete piece after a blast and the degree of the scattering can be adjusted, and the efficiency of the operation | work which removes the structure after falling by a blast can be improved.
[0019]
The invention according to claim 5 is the method for demolition of a reinforced concrete structure according to claim 1, claim 2, claim 3 or claim 4, wherein the charge is changed from a shallow layer close to the surface of the structure to a deep layer. The explosive loaded in the shallow layer should be detonated at a time lag from the explosive loaded in the shallow layer to the explosive loaded in the deep layer. , And explode with a time lag into the one loaded at a position away from the boundary groove or intermediate groove.
[0020]
In general, blasting deep in a structure is heavy and the concrete is difficult to crush, but this method creates a small time lag from the shallow layer close to the surface of the structure to explode. The concrete will be crushed and the load during the explosion of the deep explosive will be reduced. Therefore, the deep explosive can also effectively crush the concrete, and the entire structure can be reliably crushed. In addition, blasting in shallow layers is easily affected by reinforcing bars placed near the surface of the structure, but the blasting starts from a position close to the groove where the reinforcing bars are cut, and the blasting is performed at a distant position in sequence. Since the concrete is crushed from a position close to the point and the rebar restraint is released, the entire region can be crushed equally. In this way, the effect of blasting the structure can be ensured by loading the mixture with a time difference and exploding the explosive.
The time difference between explosions is preferably about 1/10 second to 1 second, but can be appropriately determined within the range of the ignition delay time that can be set for the detonator that induces the explosive.
[0021]
The invention which concerns on Claim 6 cuts the lower end groove | channel of the circumferential direction on the surrounding surface of the said crushing part of this pier by making a part of cross section of the pier which is a reinforced concrete structure into a non-crushing part, and making the remaining cross section a crushing part. An upper end groove is provided at a position obliquely above the crushing part side from the boundary between the non-crushing part and the crushing part, and the reinforcing bars are cut in the upper end groove and the lower end groove,
It is assumed that a charge hole is formed in a range below the upper end groove and above the lower end groove, and the charge hole is charged with an explosive to be blown up.
[0022]
In the above method, the crushing part of the pier is set in a wedge shape, and this part is crushed by blasting. And in the cross section near the lower end, a non-crushing part is provided near the tip of the wedge-shaped crushing part, and this part remains without crushing, so the pier is crushed in a wedge shape with this non-crushing part as a fulcrum. Toppling in the direction. Therefore, the pier can be reliably fallen in a predetermined direction.
[0023]
In addition, the groove is cut to a limited area, and the rebar is cut in this groove to release the restraint. Therefore, the area to be crushed and the area not to be crushed can be controlled accurately, and the tipping over is surely performed in a predetermined direction. Can be made. Further, the cutting amount of the groove is suppressed to a small amount, and the pier can be efficiently disassembled.
[0024]
The invention according to claim 7 is the disassembly method according to claim 6, wherein a vertical groove is provided at a predetermined interval in the circumferential direction between the upper end groove and the lower end groove, The rebars arranged in the horizontal direction shall be cut.
[0025]
A reinforced concrete pier is generally provided with a main reinforcing bar that resists a large bending moment in the vertical direction, and a band reinforcing bar is provided so as to surround the outside. The band reinforcing bars are arranged in a shape closed in the circumferential direction, and are arranged so as to restrain the main reinforcing bars from being pushed outward. Therefore, by cutting the horizontal bars arranged in the horizontal direction in the groove provided in the vertical direction, the restraint of the main reinforcing bars in the vertical direction is reduced, and by blasting inside the position where the reinforcing bars are arranged, The reinforcing bars are pushed out and the concrete is sufficiently crushed.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic side view of a bridge disassembled by a blast dismantling method according to an embodiment of the present invention.
In this bridge, a first abutment 1 and a second abutment 2 are provided on both sides of the bridge point, respectively, and a first pier 3 and a second pier 4 are provided between them. It is a bridge between three diameters with a girder having a hinge in between.
[0027]
The girder is spanned from the first abutment 1 to the first pier 3 and has a first concrete girder 5 having an overhang portion having a predetermined length between the center diameters, and the second abutment 2 to the second pier 4. It has the 2nd concrete girder 6 which continued above and overhanged between the center diameters, and the steel girder 7 spanned between the ends of the two concrete girders 5 and 6 overhanging to the center diameter. . Girder receiving portions 5a and 6a are provided at the ends of the concrete girders 5 and 6, and the steel girder 7 is placed on these and is simply supported via a support (not shown). The concrete girders 5 and 6 are supported by the abutments 1 and 2 and the piers 3 and 4, and are supported on the piers 3 and 4 through the support 8 so as to be rotatable around a horizontal axis perpendicular to the bridge axis. Yes. In addition, on the abutments 1 and 2, the abutments 1 and 2 and anchors (see FIG. 2) are supported via a support (not shown) and the overturning moment of the concrete girders 5 and 6 toward the center span side is suppressed. (Not shown).
[0028]
As shown in FIG. 1 (b), the first pier 3 is erected on a reinforced concrete footing 9 with two columns 3a and 3b arranged side by side in the width direction of the spar, and the upper part thereof is a beam 3c. Concatenated. These cylinders 3a and 3b are made of reinforced concrete. Vertical main reinforcing bars are embedded at a predetermined pitch in the vicinity of the circumferential surface of the cylinder, and strip reinforcing bars are horizontally arranged outside the cylinders. Yes. And the main reinforcing bar and the band reinforcing bar are arranged in two steps of the outer side and the inner side so that a large bending moment can be resisted.
[0029]
The dismantling of the bridge is started by first removing the steel girder 7 between the center spans. The steel girder 7 can be removed by lifting it with a crane and lowering it on the ground surface, cutting or dismantling it, or cutting it part by part while supporting it on a support. It may also be dropped by blasting.
The concrete girders 5 and 6 are supported on the abutments 1 and 2 and the piers 3 and 4 while the piers are toppled in the horizontal direction as shown in FIG. .
[0030]
Next, the step of causing the pier 3 to fall down together with the concrete girder 5 by blasting will be described in detail with reference to FIGS. 2, 3, 4, and 5.
In order to cause the pier 3 to collapse in the direction indicated by the arrow in FIG. 2B, a region 13 to be crushed (crushed portion) and a region 14 that is not crushed (non-crushed portion) are set. First, the lower reference line 11 in the region to be crushed near the lower end is set in the horizontal direction. The region 13 to be crushed on the reference line 11 is half of the column 3b on the side to be collapsed and the other column 3a among the two columns of the pier. And let the part 14 which is not crushed be the half of the remaining part, ie, the pillar on the opposite side to the side to collapse. The upper limit 15a, 15b of the region to be crushed is set in the vicinity of the upper reference line 12 (indicated by a one-dot chain line in FIGS. 2 and 3) set obliquely upward from the non-crushing part side to the region to be crushed. However, it does not necessarily have to be on the reference line 12, and can be set in the horizontal direction as shown in FIG. Further, it may be slightly above or below the reference line 12 or may be set to be inclined in the direction of the reference line 12.
[0031]
Since the range to be crushed is determined with reference to the upper reference line 12 and the lower reference line 11 set as described above, the region 13 to be crushed on the collapse side becomes wider in the height direction, and crushed. The area to be made is almost wedge-shaped.
[0032]
A groove to be cut in the region 13 to be crushed will be described with reference to FIGS.
Lower end grooves 21 and 22 (boundary grooves) are cut in the circumferential direction of the cross section along the reference line 11 near the lower ends of the two cylinders 3a and 3b. At this time, the lower end groove 22 is formed in the column 3b on the side to be collapsed over the entire circumference, and the lower end groove 21 to be cut in the lower end portion of the opposite side column 3a is a region on the opposite side to the direction in which the pier 3 is collapsed. Cut the part. Further, in the vicinity of the upper reference line 12, circumferential upper end grooves 23 and 24 are horizontally formed in the two cylinders 3a and 3b in the same manner as the lower end grooves.
[0033]
Further, a vertical groove is cut at a position where the strip reinforcing bars 35 arranged on the cylinders 3a and 3b can be cut, that is, on the peripheral surfaces of the cylinders 3a and 3b. Four vertical grooves 28, 29, 30, and 31 are cut at equal intervals in the circumferential direction on the cylinder 3b positioned in the collapse direction, and the other cylinder 11 has 3 at equal intervals near the collapse direction. The banquet grooves 25, 26, 27 of the book are cut. Two of them are provided at the boundary with the non-crushing part (boundary groove).
[0034]
The depth of the cutting of these grooves is set to such an extent that the reinforcing bars are exposed, and the width and depth of the grooves are set to such an extent that the reinforcing bars exposed in the grooves can be cut. These grooves are cut using a water jet, a breaker or the like. In particular, if a water jet is used, the width and depth of the groove can be easily adjusted to efficiently form a groove having a depth at which the reinforcing bars embedded in the cylinders 3a and 3b are exposed.
[0035]
Then, the reinforcing bars are cut in the groove as shown in FIG. In consideration of the cross-sectional shape of the pier, the dimensions, the strength of the concrete, the amount of reinforcing bars, the amount of explosives, etc., all the reinforcing bars exposed in the groove may be cut, or some of the reinforcing bars may be left behind. Can also be cut. In this embodiment, as shown in FIGS. 4 and 5, the main reinforcing bars 34 in the vertical direction and the horizontal reinforcing bars 35 surrounding the outside are arranged in two stages on the pier columns 3 a and 3 b, respectively. In the direction grooves 21, 22, 23, and 24, all the outer main reinforcing bars 34a are cut, and the inner main reinforcing bars 34b are cut in half, every other one. Further, in the vertical grooves 25, 26, 27, 28, 29, 30, 31, all of the rebars 35 arranged in two stages are cut.
[0036]
In determining the amount of reinforcing bars to be cut, it is necessary to appropriately set the degree of maintaining the binding force of the reinforcing bars to the concrete because it affects the crushing state at the time of blasting. In other words, if the rebar restraint is small, the cylinder is crushed into a large concrete lump when blown up, and workability in subsequent processing is deteriorated. Conversely, if the reinforcing bar's restraining force is maintained excessively, the column will not be sufficiently destroyed, and the entire pier may not collapse. For this reason, it is desirable to appropriately determine the rebar to be cut by performing a test blasting or the like in advance.
[0037]
The rebar cutting may be performed using a flame by jetting high-pressure gas, or a water jet containing an abrasive may be used. It can also be cut mechanically with a cutter or the like.
[0038]
Next, drilling of a charge hole for loading an explosive will be described with reference to FIGS. In the region divided by the grooves of the cylinders 3a and 3b, that is, in the crushing portion, the charge holes 41 and 42 are formed at predetermined positions. The charging hole is provided with a charging hole 41 extending from the surface of the cylinder to a shallow position and a charging hole 42 reaching a deep position, and has a plurality of depths. At this time, in order to drill the charge hole, the drill hole is drilled accurately using a rock drill for drilling holes in rock or concrete. The hole drilling is performed from the surface where the groove on the circumferential surface of the cylinder is not cut, and the depth from the surface is accurately set to a predetermined value. By performing the drilling at a position where the groove is not cut, it becomes easy to measure the depth of the charge holes 41 and 42 from the surface of the cylinder, and the work of accurately drilling the charge holes is efficiently performed. .
[0039]
Thereafter, the explosive is loaded into the charge holes 41 and 42. An electric detonator for ignition is added to the explosive. A detonator that is ignited by energization and explodes instantaneously or that explodes after a predetermined minute time delay is used. In other words, the detonator loaded in the deep hole 42 is used to explode with a delay of about 1/10 second from that loaded in the shallow hole 41. The detonators loaded in the plurality of shallow holes 41 may explode all at once, but are ignited first from the hole 41a near the groove from which the main reinforcing bar is cut, and sequentially to the hole 41b at a position away from the groove. Can be delayed. In other words, it will blow up sequentially from the place where the rebar restraint is small. By blasting in a delayed manner in this way, it becomes possible to make the load at the time of the explosion substantially uniform and to crush the whole properly.
[0040]
In the dismantling method as described above, the area around the part to be crushed is cut into a groove, and the reinforcing bar exposed in the boundary groove is cut to reduce the binding force between the reinforcing bar and the concrete, and the area to be crushed and the crushed Blasting can be done by distinguishing from areas that do not. Moreover, about the area | region to crush, by restraining a reinforcing bar by cutting an intermediate groove | channel suitably and cutting a reinforcing bar, it becomes possible to perform the crushing by blasting appropriately. For this reason, not only can the labor required for cutting be reduced, but also the amount of reinforcing bars to be cut within the cut boundary grooves and intermediate grooves can be set appropriately, leaving a small amount of reinforcing bars uncut and leaving the concrete. By maintaining the restraining force, it is also possible to control the concrete crushing state by blasting. That is, the concrete can be crushed to an appropriate size by effectively utilizing the effect of the explosive loaded in the area to be crushed by maintaining the restraining force to some extent.
[0041]
Next, another embodiment of the invention according to the present application will be described with reference to FIGS.
The concrete structure that is symmetrical to the dismantling method is a bridge pier 51 that supports a concrete girder 52 in the same manner as described above. This pier 51 is an oval as shown in FIG. It has a cross section. The bridge pier 51 together with the girder 52 is overturned to the side by blasting as shown by the arrow in FIG.
[0042]
The region 56 to be crushed by the blasting includes a lower reference line 53 set horizontally near the ground surface, and an upper reference line 54 in an oblique direction set so as to rise upward toward the overturning side. Is set in a wedge shape. And the part on the opposite side to the side to which it falls is made into the area | region 55 which is not crushed, and the whole pier is made to fall sideways by using this part as a fulcrum.
[0043]
On the peripheral surface of this pier, there are a lower end groove 61 provided in the horizontal direction along the lower reference line 53, and an upper end groove 62 set in the horizontal direction near the upper reference line 54 and formed on the stairs. The vertical groove 63 provided in the vertical direction so as to make the upper end groove 62 and the lower end groove 61 continuous is cut. The vertical grooves 63 are provided at predetermined intervals in the circumferential direction, and are continuous with the upper end grooves 62 that are stepped. Except for the non-crushing region 55, the lower groove 61, the upper groove 62, and the vertical groove 63 are formed so as to surround the peripheral surface of the region 56 to be crushed.
[0044]
These grooves are cut to a depth at which the vertical main bars 71 or the horizontal band bars 72 arranged in two steps below the surface of the pier 51 are exposed as shown in FIG. Then, all of the outer main reinforcing bars 71a are cut in the lower end groove 61 and the upper end groove 62, and half of the inner main reinforcing bars 71b are cut every other line. Further, in the vertical groove 63, all of the outer and inner belt reinforcing bars 72 are cut.
In the pier shown in FIGS. 6 and 7, an upper end groove 81 is provided obliquely along the upper reference line 54 as shown in FIG. The band reinforcing bar 72 may be cut.
[0045]
After the grooves 61, 62 and 63 are formed as described above, shallow charge holes 73 and deep charge holes 74 are provided at predetermined intervals as shown in FIG. A predetermined region can be crushed by blasting from a deeper layer to a deeper layer with a minute time difference, and the pier 51 can be turned sideways with the girder 52.
[0046]
【The invention's effect】
As described above, in the method of blasting and dismantling a reinforced concrete structure according to the present invention, a groove is cut from the surface at the boundary between a region to be crushed by blasting and a region to be left without being crushed. After cutting the rebars, the area to be crushed is charged and blasted, so the concrete structure can be crushed by accurately controlling the area. It is also possible to control the crushing state by selecting the degree of restraint of the reinforcing bars. Further, the work of lifting the reinforcing bars in order to reduce the restraint of the reinforcing bars is greatly reduced, and the efficiency of the work is improved.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a bridge that can be dismantled by applying a blast dismantling method according to the present invention.
FIG. 2 is a schematic view showing a direction in which a pier is toppled over in order to disassemble the bridge shown in FIG. 1 and a region to be crushed for that purpose.
FIG. 3 is a schematic view showing grooves and charge holes provided in the pier shown in FIG. 2;
4 is a cross-sectional view of the pier shown in FIG.
FIG. 5 is an enlarged cross-sectional view showing a groove cut in the pier shown in FIG. 3 and a reinforcing bar cut in the groove.
FIG. 6 is a front view and a plan sectional view showing another example of a pier to which the blasting dismantling method of the present invention is applied.
7 is a schematic view showing a region where the pier shown in FIG. 6 is crushed, a position of a groove to be cut, and a position of a charge hole.
8 is a cross-sectional view of the pier shown in FIG. 7 taken along the line BB.
FIG. 9 is a schematic view showing another example of the arrangement of grooves to be cut in the pier shown in FIG. 6;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st abutment 2 2nd abutment 3 1st pier 4 2nd pier 5 1st concrete girder 6 2nd concrete girder 7 Steel girder 8 Bearing 9, 10 Footing 11 Lower reference line 12 Upper side Reference line 13 Crushing area 14 Crushing area 15 Crushing area upper limit 21, 22, 23, 24 Horizontal groove 25, 26, 27, 28, 29, 30, 31 Vertical groove 34 Main reinforcing bar 35 Reinforcing bar 41 Shallow charge hole 42 Deep charge hole 51 Bridge pier 52 Concrete girder 53 Lower reference line 54 Upper reference line 55 Non-crushing area 56 Crushing area 61 Lower end groove 62 Upper end groove 63 Vertical groove 71 Main reinforcing bar 72 Reinforcing bar 73 Shallow charge hole 74 Charge hole

Claims (7)

Cutting a boundary groove from the surface of the structure at the boundary between the area to be crushed by blasting and the area to be left unbroken in the reinforced concrete structure,
The boundary groove has a depth at which a reinforcing bar disposed in the structure is exposed,
Cutting the rebar in the boundary groove,
Drilling a charge hole in the area to be crushed
A method for blasting and dismantling a reinforced concrete structure, wherein the charge hole is loaded with an explosive and blasted. 2. The reinforced concrete structure according to claim 1, wherein in the region to be crushed, an intermediate groove having a depth reaching the reinforcing bar is cut at a predetermined interval, and the reinforcing bar is cut in the intermediate groove. How to explode things. 3. The reinforced concrete structure according to claim 2, wherein intermediate grooves provided at predetermined intervals in a region to be crushed of the structure are cut in a direction in which an outermost reinforcing bar disposed in the concrete can be cut. Blasting dismantling method. 4. The reinforced concrete structure according to claim 1, wherein a part of the reinforcing bar exposed in the boundary groove or the intermediate groove is cut and the rest is left without being cut. 5. Blast dismantling method. Charging shall be performed over several layers, from a shallow layer close to the surface of the structure to a deep layer,
The explosive loaded in the shallow layer will explode from the explosive loaded in the deep layer with a time lag,
The shallow layer explosive explodes at a time difference from one loaded near the boundary groove or intermediate groove to one loaded away from the boundary groove or intermediate groove. Item 5. A method for blasting and dismantling a reinforced concrete structure according to item 2, claim 3 or claim 4. A part of the cross section of the pier that is a reinforced concrete structure is a non-crushing part, and the remaining cross section is a crushing part, cutting the circumferential lower end groove on the peripheral surface of the crushing part of the pier,
An upper end groove is provided at a position obliquely above the crushing part side from the boundary between the non-crushing part and the crushing part,
Cutting the reinforcing bars in the upper and lower grooves,
Drilling a charge hole in a range below the upper end groove and above the lower end groove,
A method for blasting and dismantling a reinforced concrete structure, wherein the charge hole is loaded with an explosive and blasted. The vertical groove is provided at a predetermined interval in the circumferential direction between the upper end groove and the lower end groove, and the horizontal bars arranged in the horizontal direction are cut in the vertical groove. 6. A method for demolition of reinforced concrete structures according to 6.

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