JP7295610B2 - Method for removing concrete from the surface of a reinforced concrete building - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a method of removing concrete from the surface of a reinforced concrete skeleton, and more particularly to a method of removing concrete in a predetermined area by blasting to expose rebar.

As a method of dismantling a reinforced concrete frame, there is a method in which the surface concrete is destroyed, the exposed reinforcing bars are cut to reduce the strength, and a load is applied to the portion where the strength has decreased to collapse the reinforced concrete structure. For example, Patent Literature 1 describes an explosive demolition method for a reinforced concrete frame. In this method, a boundary groove is cut from the surface of the reinforced concrete structure at the boundary between the area to be crushed by blasting and the area to be left without crushing, the reinforcing bars are cut in the boundary groove, and the area to be crushed A charge hole is drilled in the hole, and an explosive is charged into the charge hole and exploded to dismantle the concrete frame. Boundary grooves are cut using water jets, breakers, or the like to expose rebar placed within the building.

As a method for dismantling a reinforced concrete frame, a wire saw method is also known, in which the reinforcing bars and the concrete portion of the reinforced concrete frame are cut and demolished at the same time. For example, Patent Literature 2 describes cutting an existing building with a wire saw to divide it into a plurality of blocks in a building reconstruction work.

Japanese Patent Application Laid-Open No. 2004-293260 JP 2010-248822 A

However, in order to cut the exposed reinforcing bar with a simple means such as acetylene gas or a cutter, it is necessary to expose the reinforcing bar by crushing the concrete portion existing in a wide range around the reinforcing bar. For this purpose, it is necessary to first crush the concrete portion with a breaker or the like, and then finely secondarily crush the concrete portion with a pick or the like to remove even minute concrete pieces. The labor and construction time required for this secondary crushing are excessive compared to the crushing volume, and are very uneconomical in terms of cost.

There is also a method of cutting reinforcing bars by an electrical method, but in this case, the number of exposed reinforcing bars is reduced compared to the above case, but in other respects the same work as the above is required. Become. Therefore, the labor and construction time could not be sufficiently reduced, and the cost-effectiveness could not be sufficiently improved in consideration of the loss of the equipment.

On the other hand, the wire saw construction method is limited in its application range depending on the shape and dimensions of the reinforced concrete frame, and is particularly unsuitable for floor slab structures. In addition, the cost-effectiveness was lower than that of the above method, considering the increase in the cutting process for cutting into a shape that can be transported, and the loss of facilities and equipment.

The present invention has been made in view of these problems, and an object thereof is to provide a method of removing concrete from the surface of a reinforced concrete frame in a short period of time with less labor to expose the reinforcing bars.

At least some embodiments of the present invention are a method of removing concrete from a surface (4) of a reinforced concrete structure (1) forming a plurality of charges (6) in which explosive charges (5) are to be placed. drilling a plurality of charge holes (7, 7a, 7b) containing the charge portion in the concrete portion (3) of the reinforced concrete frame and placing the explosive in each of the charge portions for Then, by blasting the explosive, the concrete existing on the surface side from the surface side reinforcing bars (2a) arranged in a lattice shape near the surface and along the surface is peeled off. and exposing a reinforcing bar, wherein the charging part is provided at a position deeper than the surface side reinforcing bar with respect to the surface, and the detonation distance at which the explosive can create cracks in the free surface is It is characterized by being equal to or greater than the distance from the center of the charging portion to the surface. When viewed from the surface, the surface-side reinforcing bars are arranged between the charge sections that are adjacent to each other. The surface-side reinforcing bars are arranged between the free surface of the reinforced concrete frame forming an angle with the surface and the charging section. Each surface-side reinforcing bar may be a whole or a part of one reinforcing bar.

According to this configuration, the stress wave due to the detonation and the reflected wave from the free surface are uniformly propagated to the target range, and the surface-side reinforcing bars propagate the stress wave and the reflected wave evenly, and the tensile strain is generated on the bar arrangement surface. Since it functions as a wave propagation guiding member that forms a surface, it is possible to efficiently expose the reinforcing bars.

In at least some embodiments of the present invention, in the above configuration, in the depth direction with respect to the surface, the distance from the side surface of the charging section to the side surface of the surface-side reinforcing bar having the largest cover among the surface-side reinforcing bars is 0.5 to 2 times the diameter of the surface reinforcing bars.

According to this configuration, the detonation force can be efficiently transmitted to the surface-side reinforcing bars, and the charge hole can be drilled while avoiding the reinforcing bars.

According to at least some embodiments of the present invention, in any of the above configurations, the charge hole is formed to extend along a direction parallel to the surface.

According to this configuration, it is possible to lengthen the arrangement section of the filling material (8) for blocking the charge hole, and increase the adhesive force of the filling material to the charge hole. The timber is retained within the charge hole and can transmit the detonating force to the concrete and rebar.

At least some embodiments of the present invention may modify the above configurations so that the charging holes are formed from the surface.

According to this configuration, since the drilling distance is shortened, the working time can be shortened.

At least some embodiments of the present invention are characterized in that in any of the above configurations , the center-to-center distance between adjacent charges is less than or equal to twice the detonation distance.

According to this configuration, the concrete can be removed over a wide range to expose the reinforcing bars.

According to the present invention, it is possible to remove concrete from the surface of reinforced concrete in a short period of time with less labor to expose the reinforcing bars.

Front view of a concrete frame to which the method according to the embodiment is applied A plan view of a concrete frame to which the method according to the embodiment is applied Side view of a concrete frame to which the method according to the embodiment is applied An enlarged view of a concrete skeleton to which the method according to the embodiment is applied The side view of the concrete frame to which the method according to the first modified example according to the embodiment is applied. Front view of a concrete skeleton to which the method according to the second modification of the embodiment is applied Front view of a concrete skeleton to which the method according to the third modification of the embodiment is applied Photographs showing examples (a: before drilling, b: after detonation (diagonally above), c: after detonation (front))

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 4 schematically show a reinforced concrete building 1 demolished by the method according to the embodiment. A reinforced concrete frame 1 includes reinforcing bars 2 and concrete portions 3 in which the reinforcing bars 2 are embedded. In the figure, only the outline of the concrete portion 3 of the reinforced concrete frame 1 is indicated by a solid line, and the reinforcing bars 2 arranged therein are shown as if the concrete portion 3 were seen through.

The reinforced concrete skeleton 1 is, for example, a floor slab of a concrete bridge, a floor and walls of a building, a mechanical foundation, a retaining wall, and the like. The surface-side concrete portion 3a to be removed extends from the surface 4 on the front side of the reinforced concrete frame 1 to the depth of the surface-side reinforcing bars 2a arranged on the front side. The surface-side reinforcing bars 2a are arranged along the surface 4 in a grid pattern.

The reinforced concrete frame 1 is demolished by crushing the surface-side concrete part 3a to expose the surface-side reinforcing bars 2a, cutting the surface-side reinforcing bars 2a, and applying a load to the reinforced concrete frame 1 so as to break at the cut parts. This embodiment relates to the step of removing the surface-side concrete portion 3a to expose the surface-side reinforcing bars 2a in the demolition work of the reinforced concrete frame 1. FIG.

First, the positions of the surface-side reinforcing bars 2a in the reinforced concrete frame 1 are grasped by known reinforcing bar searching means such as the electromagnetic radar method, the electromagnetic induction method, or the X-ray radiographic method.

A charge hole 7 is then drilled in the concrete portion 3 in order to form a charge section 6 in which the explosive charge 5 is to be placed. The charge hole 7 is preferably drilled from the upper surface of the reinforced concrete skeleton 1, which is the surface perpendicular to the surface 4. As shown in FIG. This is because the charging hole 7 is deepened to ensure the adhesion of the plugging material 8 packed in the charging hole 7 to the charging hole 7 .

The depth D from the surface 4 to the center of the charge portion 6 is greater than the depth from the surface 4 of the surface-side reinforcing bar 2a with the largest cover, and is less than or equal to the initiation distance L _max . The detonation distance L _max means the distance at which the used explosive material (the type and dose of the explosive 5) can generate cracks on the free surface. In the depth direction from the surface 4, the charging hole 7 is separated from the surface side reinforcing bar 2a with the largest cover (from the side surface of the charging hole 7 to the side surface side of the surface side reinforcing bar 2a with the largest cover) The shortest distance d of is larger than 0), more preferably, about 0.5 to 2 times the diameter of the surface side reinforcing bar 2a with the largest cover, so that it is spaced from the surface side reinforcing bar 2a (surface side reinforcing bar When the diameter of the charging hole 2a and the diameter of the charging hole 7 are close to each other, it is preferable that the center-to-center distance between the two is approximately 1.5 to 3 times that of the surface-side reinforcing bar 2a.

When viewed from the front, the distance from the charging portion 6 closest to the free surface forming an angle with the surface 4 to the free surface (for example, the distance L ₁ from the left charging portion 6 to the left side surface in FIG. 1, all The distance H ₁ from the charge section 6 to the top surface and the distance H ₂ from all charge sections 6 to the bottom surface) are less than or equal to twice the detonation distance L _max . In addition, the center-to-center distance _L2 of the charge portions 6 adjacent to each other is less than or equal to twice the detonation distance _Lmax . In addition, it is preferable that the charge part 6 is arranged in the center of two surface-side reinforcing bars 2a that are parallel and adjacent to each other in a front view, and that the stress wave due to the initiation is evenly transmitted to both surface-side reinforcing bars 2a (Fig. 1) may be displaced from the center (vertical direction in FIG. 1), or may be arranged so as to overlap the surface-side reinforcing bars 2a.

Next, the explosive 5 is placed in the charging portion 6, and the portion of the charging hole 7 above the charging portion 6 is filled with the plugging material 8. - 特許庁The center of the explosive charge 5 substantially coincides with the center of the charge section 6 . The filling material 8 is adhered to the charge hole 7 with a sufficient length so as not to jump out from the charge hole 7 even when the explosive 5 is detonated.

Next, the explosive charge 5 is detonated. It is preferable to detonate all the explosives 5 at the same time, and when the number of explosives is large, a plurality of explosives close to each other are regarded as one block, and the explosives in one block are detonated simultaneously, and the blocks are detonated sequentially. is preferred. Although not bound by theory, the stress wave due to the detonation of the explosive 5 and the reflected wave from the free surface propagate to the surface-side reinforcing bars 2a and the surface-side concrete portion 3a. At this time, the surface-side reinforcing bar 2a functions as a wave propagation guiding member that evenly propagates the stress wave due to the initiation and the reflected wave from the free surface, and forms a tensile strain surface on the surface of the surface-side reinforcing bar 2a. Therefore, the surface-side concrete portion 3a can be efficiently crushed, and the surface-side reinforcing bars 2a can be exposed with the concrete peeled off.

FIG. 5 shows a side view of a first modification of the above embodiment. In the above embodiment, the surface 4 to be removed is the front surface in order to ensure the adhesion of the plugging material 8 to the charging hole 7, whereas the charging hole 7 is drilled from the upper surface and charged. The length of the hole 7 is ensured. As long as the adhesion strength to withstand the detonation of the explosive charge 5 can be obtained, the hole may be drilled from other than the upper surface. In the first modification, the charge hole 7 is drilled from the surface 4 to be removed. In the illustrated example, the charging hole 7 is drilled obliquely with respect to the surface 4 in order to secure a length for attaching the plugging material 8 to the charging hole 7 . The charge hole 7 may be drilled so as to be perpendicular to the surface 4 as long as the adhesion to the charge hole 7 can be ensured.

6 and 7 show front views of second and third modifications of the above embodiment. These modifications show the case where two or more explosives 5 are required not only in the horizontal direction of the figure but also in the vertical direction, that is, the case where the height of the reinforced concrete skeleton 1 exceeds four times the detonation distance L _max . As shown in FIG. 5, two or more charging portions 6 may be provided in one charging hole 7 extending in the vertical direction. Also, as shown in FIG. 6, charging holes 7a and 7b having different depths may be provided, and one or more charging portions 6 may be provided in each.

In these modified examples, the mutual positional relationship of the charging portion 6, the charging holes 7, 7a, 7b, and the surface 4 in the front-rear direction (the direction perpendicular to the paper surface of FIGS. 6 and 7) is different from that of the above-described embodiment. It is the same. The distance H ₁ from the center of the charging section 6 arranged on the upper end side to the upper surface, the distance H ₂ from the center of the charging section 6 arranged on the lower end side to the lower surface, and two vertically adjacent charges The vertical distance _H3 between the parts 6 is respectively less than or equal to twice the detonation distance _Lmax .

In the modification shown in FIG. 7, the distance _L1H from the center of the upper charging section 6 arranged on the leftmost side to the left side surface and the distance from the center of the lower charging section 6 arranged on the leftmost side The distance _L1L to the left side is respectively less than twice the ignition distance _Lmax , and the same applies to the right end side. The center-to-center distance L _2H between the adjacent upper tier charging sections 6 and the center-to-center spacing L _2L between the mutually adjacent lower tier charging sections 6 are each less than or equal to twice the initiation distance L _max .

In the modification shown in FIG. 7, the shallow charging hole 7a is located in the center of the two deep charging holes 7b adjacent to each other, and the deep charging hole 7b is located between the two shallow charging holes 7a adjacent to each other. However, the position in the left-right direction may be shifted within a range that satisfies the above relationship with the detonation distance L _max .

FIG. 8 is a photograph showing the state before and after detonation of an example corresponding to the above embodiment. The test piece of the reinforced concrete frame 1 had a rectangular parallelepiped shape measuring 700 mm long, 1500 mm wide and 700 mm high, and rebars 2 made of deformed steel bars with the designation D19 were arranged in the same manner as the rebars 2 in FIGS. One of the planes parallel to the horizontal and vertical directions was taken as the surface 4 to be removed.

The detonation distance L _max was equal to the maximum crushable length determined by the explosive type and dose, and for explosive 5 L _max =400 mm. Three charging holes 7 are drilled vertically from the upper surface of the reinforced concrete frame 1, each having a diameter of 18 mm and a depth of 373.5 mm. The section was 47 mm long from the bottom. The center-to-center distance _L2 of the charging holes 7 adjacent to each other was 418.8 mm, and the distance _L1 from the center of the charging hole on the end side to the lateral free surface was 331.3 mm.

When the explosive 5 was detonated, the surface-side concrete portion 3a was crushed and the surface-side reinforcing bars 2a were exposed. Concrete was almost peeled off from the exposed surface-side reinforcing bars.

It took about 20 minutes to remove the surface-side concrete portion 3a of about 1 m ² to expose the surface-side reinforcing bars 2a. This was more than 20 times more efficient than manual work.

Although the specific embodiments have been described above, the present invention is not limited to the above embodiments and can be widely modified. For example, the present invention may be applied not only to demolition work of a reinforced concrete frame, but also to partial removal of concrete for repair, installation of equipment, or the like. Further, instead of drilling the charge hole so as to be orthogonal to the free surface such as the upper surface, the hole may be drilled obliquely to the free surface.

1: Concrete frame 2: Reinforcing bar 2a: Surface side reinforcing bar 3: Concrete part 3a: Surface side concrete part 4: Surface 5: Explosive 6: Charging part 7: Charging hole 7a: Shallow charging hole 7b: Deep charging hole 8: Filling material

Claims (3)

A method for removing concrete from the surface of a reinforced concrete frame, comprising:
drilling a plurality of charge holes including the charge section in the concrete portion of the reinforced concrete frame to form a plurality of charge sections in which the explosive is to be placed; and placing the explosive in each of the charge sections. placing;
Exploding the explosive to expose the surface-side reinforcing bars by exfoliating the concrete existing closer to the surface than the surface-side reinforcing bars arranged in a grid pattern near the surface and along the surface. and
The charge portion is provided at a position deeper than the surface-side reinforcing bars with respect to the surface, and the initiation distance at which the explosive can generate cracks on the free surface is from the center of the charge portion to the surface. is greater than or equal to the distance to
In the depth direction with respect to the surface, the distance from the side surface of the charging section to the side surface of the surface-side reinforcing bar with the largest cover among the surface-side reinforcing bars is 0.5 to 2 times the diameter of the surface-side reinforcing bar. , wherein the surface-side reinforcing bars are arranged between the charge sections adjacent to each other when viewed from the surface, and between the free surface of the reinforced concrete skeleton forming an angle with the surface and the charge section is arranged with the surface-side reinforcing bars,
A method, wherein the center-to-center distance between adjacent charges is less than or equal to twice the detonation distance. 2. The method of claim 1, wherein said charging holes are formed to extend along a direction parallel to said surface. 2. The method of claim 1, wherein said charge hole is formed from said surface.

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