JP7018614B2 - Method of forming induced joints in concrete structures - Google Patents

Description

The present invention relates to a method for forming an induced joint in a concrete structure, in particular, for forming an induced joint that induces cracks across a concrete structure constructed continuously in one direction to a predetermined thickness. The present invention relates to a method of forming an induced joint in a concrete structure.

As a concrete structure constructed continuously in one direction with a predetermined thickness, for example, tunnel lining concrete has a predetermined thickness on the inner peripheral surface of an excavated tunnel in a tunnel construction method such as a mountain tunnel construction method. It is a concrete structure that is covered with concrete and is continuously constructed in the direction of tunnel excavation. As a method for forming tunnel lining concrete, a construction method using a tunnel lining mold called centre is generally adopted. (See, for example, Patent Document 1 and Patent Document 2). As shown in FIG. 6, for example, the tunnel lining mold 50 extends from the side wall portion 55 of the tunnel 53 to the upper part along the inner peripheral surface of the tunnel 53 having a shape including an arch-shaped portion 52 such as a horseshoe shape. Unreinforced concrete is preferably used in the lining space 61 between the installed tunnel lining mold 50 and the ground covered by the sprayed concrete 54 on the inner peripheral surface of the tunnel 53. By casting and hardening, the lining concrete is formed by being integrated with the concrete of the invert portion 51 at the bottom of the tunnel.

Further, as the tunnel lining mold 50, for example, in addition to an assembly type tunnel lining mold called a ball centre, a mobile tunnel lining mold called a slide centre is known, and the tunnel 53. As the excavation work progresses, for example, while re-installing the tunnel lining mold 50 at predetermined construction spans of about 10.5 m, for tunnel lining from the rear to the front in the excavation direction of the tunnel 53. The lining concrete on the side and the upper part of the tunnel 53 is sequentially cast and formed by using the mold 50.

Then, in order to place the lining concrete on the side and top of the tunnel using the tunnel lining formwork 50, for example, as shown in FIGS. 7A to 7D, the installed tunnel lining concrete is used. As a height region where concrete can be placed from the inspection window 56 provided in the form 50, for example, the region from the side wall portion 55 of the tunnel 53 to the shoulder portion of the arch-shaped portion 52 is via the inspection window 56. The concrete 57 is supplied, and the vibrator 58 is inserted through the inspection window 56, and the concrete 57 is placed while compacting the supplied concrete 57 (see FIGS. 7A to 7C). After that, as a height region where it is difficult to compact by the vibrator 58 while supplying concrete 57 from the inspection window 56, the tunnel is provided for the region of the crown portion 59 (see FIG. 6) of the tunnel 53. A pattern in which concrete is press-fitted in by a blow-up method from a blow-up inlet 60 provided at the top end of the lining form 50 to form the concrete 57 of the crown portion 59 without compacting directly using a vibrator. Is adopted (see FIG. 7 (d)).

More specifically, after installing the tunnel lining formwork 50 at a predetermined position, for example, from the lower part of the side wall portion 55, the concrete 57 is poured through the lower inspection window 56 and compacted using the vibrator 58. (See FIG. 7A) and a step of compacting the concrete 57 with the vibrator 58 while pouring the concrete 57 toward the arch-shaped portion 52 at the upper part of the side wall portion 55 through the inspection window 56 in the middle stage (FIG. 7 (a)). b)) and the step of compacting using the vibrator 58 while pouring concrete 57 through the upper inspection window 56 and, if necessary, the blow-up inlet 60 to the front of the crown portion 59 of the arch-shaped portion 52. (See FIG. 7 (c)), concrete 57 is press-fitted from the existing lining concrete 62 side portion of the crown portion 59 through the blow-up inlet 60 by a blow-up method, and compaction is performed directly using a vibrator. Instead, the lining concrete is cast by the step of filling concrete up to the end formwork 63 (see FIG. 7D).

Japanese Unexamined Patent Publication No. 2001-2800094 Japanese Patent Application Laid-Open No. 2003-262906

In addition, in recent tunnel construction methods, the progress of the process for forming lining concrete, from concrete placement to curing and demolding of the tunnel lining formwork, is progressed by improving the excavation technology. It is not possible to keep up with the progress of the excavation process. For this reason, for example, the process from assembling the formwork for tunnel lining to placing concrete and the process from curing the placed concrete to removing the formwork for tunnel lining are separated. The process from demolding, moving, and assembling the formwork for tunnel lining to placing concrete was completed in one day, and the next day was exclusively for the concrete curing period. A long-span tunnel lining formwork 10 having an extension of about 18 m is preferable instead of the commonly used tunnel lining formwork having an extension of about 10.5 m. It is being studied to increase the construction span of the lining concrete in one cycle, shorten the construction period, and accelerate the progress of the process for forming the lining concrete.

On the other hand, the construction span of one cycle of tunnel lining concrete constructed continuously in the tunnel excavation direction with a predetermined thickness using a tunnel lining mold is, for example, an extension of about 10.5 m to about 18 m. For example, in a construction span of about 10.5 m, cracks due to drying shrinkage and temperature shrinkage are absorbed at the boundary between adjacent construction spans, and cracks are formed in the lining concrete between the construction spans. What could be effectively suppressed from occurring is that the extension of cracks due to drying shrinkage and temperature shrinkage becomes longer due to the increase in the construction span of one cycle of lining concrete using the tunnel lining mold. It tends to occur in the part between the concrete construction spans. For this reason, when extending the construction span of one cycle of tunnel lining concrete constructed continuously in the tunnel excavation direction using a tunnel lining formwork to a predetermined thickness, It is desirable to provide an induced joint that induces cracks due to drying shrinkage and temperature shrinkage in the middle part of the construction span.

As a method of providing an induced joint in the middle part of a concrete structure constructed continuously in one direction to a predetermined thickness, such as tunnel lining concrete, after the cast concrete is hardened and the mold is removed from the mold. For example, a method of forming an induced joint by cutting the intermediate portion of the hardened concrete in the extension direction with a concrete cutter into a groove shape can be considered, but especially when cutting the hardened concrete with a concrete cutter into a groove shape. For tunnel lining concrete, it is a lot of work to cut the concrete in a groove shape while moving the concrete cutter along the inner peripheral surface of the curved cross section including the arch-shaped part. Will be required.

The present invention has many induced joints that induce cracks due to drying shrinkage and temperature shrinkage of concrete in the middle part of the construction span of one cycle of a concrete structure constructed continuously in one direction to a predetermined thickness. It is an object of the present invention to provide a method for forming an induced joint in a concrete structure which can be easily provided without the trouble of the above.

The present invention is a method for forming an induced joint in a concrete structure for forming an induced joint that induces cracks across a concrete structure that is continuously constructed in a predetermined thickness in one direction. A plurality of plate members are connected in a state where they are adjacent to each other so as not to create a gap in the transverse direction of the concrete structure by projecting from the mold surface of the concrete mold that divides the concrete casting space toward the casting space. A letter "H" in which a part of the plurality of plate members that are arranged and arranged in a row is widened toward the drawing direction from the placing space at a distance between the side edges on both sides. As a shape plate member, it is attached to a concrete mold so that it can be pulled out, and when the concrete placed in the concrete placement space is hardened, the C-shaped plate member is pulled out from the concrete mold in advance and each The above-mentioned object is achieved by providing a method for forming an induced joint in a concrete structure for forming an induced joint extending in a transverse direction at a desired position of the concrete structure by pulling out the plate member. be.

The method for forming the induced joint in the concrete structure of the present invention is that the concrete structure is a tunnel lining concrete formed by using the tunnel lining formwork as the concrete formwork, and the plurality of plate members. Is projected outward from the formwork surface of the outer peripheral portion of the tunnel lining formwork, and is continuously arranged in a state of being adjacent to the tunnel lining formwork in the circumferential direction to form the tunnel lining formwork. It is preferable that it is attached so that it can be pulled out.

Further, in the method of forming the induced joint in the concrete structure of the present invention, the tunnel lining concrete is constructed with a thickness of 300 to 500 mm, and the plurality of plate members are formed of the tunnel lining. It is preferable that the outer peripheral portion of the formwork is continuously arranged so as to project outward at a height of 100 to 250 mm from the formwork surface.

Further, in the method for forming the induced joint in the concrete structure of the present invention, it is preferable that the plurality of plate members are metal plates made of aluminum or steel.

Furthermore, in the method for forming an induced joint in the concrete structure of the present invention, the plurality of plate members are covered with a friction reducing material on the surface, and the friction reducing material includes a material that absorbs water and swells. It is preferable to have.

Further, in the method for forming the induced joint in the concrete structure of the present invention, it is preferable that the friction reducing material contains a highly water-absorbent resin.

According to the method for forming induced joints in a concrete structure of the present invention, the dry shrinkage of concrete or the drying shrinkage of concrete in the middle part of the construction span of one cycle of the concrete structure constructed continuously in one direction to a predetermined thickness. Induced joints that induce cracks due to temperature shrinkage can be easily provided without much labor.

It is a schematic cross section illustrating the tunnel lining concrete formed by using the tunnel lining formwork which adopts the method of forming the induced joint in the concrete structure which concerns on one preferred embodiment of this invention. It is a schematic vertical cross section explaining the tunnel lining concrete constructed by using the tunnel lining formwork which adopts the method of forming the induced joint in the concrete structure which concerns on one preferred embodiment of this invention. It is a schematic cross-sectional view explaining a state in which a plurality of plate members whose surfaces are covered with the friction reducing material are projected into a lining space and are continuously arranged in the circumferential direction of a tunnel lining formwork. (A) is a front view of the plate member attached to the part A of FIG. 3, and (b) is a state in which the plate member of (a) is projected into the lining space and temporarily fixed to the tunnel lining form. It is a schematic vertical cross section along BB of FIG. 3 to be described. It is a schematic cross-sectional view explaining the state which installed the tunnel lining formwork along the inner peripheral surface of a tunnel in the conventional tunnel lining concrete placing method. (A) to (d) are schematic side views showing a part as a cross-sectional view explaining the work procedure of the conventional tunnel lining concrete placing method.

The method for forming the induced joint in the concrete structure according to the preferred embodiment of the present invention is as shown in FIGS. 1 and 2, for example, as a concrete structure constructed continuously in one direction with a predetermined thickness. The tunnel lining concrete (hereinafter referred to as "lining concrete") 20 constructed by covering the inner peripheral surface of the tunnel 40 is induced to crack due to the drying shrinkage and temperature shrinkage of the concrete, and the other parts are cracked. The induced joint 25 (see FIG. 2), which enables the formation of a high-quality concrete surface by preventing the occurrence of concrete, can be easily placed at the desired position of the lining concrete 20 without much effort. It was adopted as a method that makes it possible to provide it.

That is, in the recent tunnel construction method, the progress of the process for forming the lining concrete 20 from concrete placing to curing and demolding of the tunnel lining formwork 10 is progressed by improving the excavation technique. In this embodiment, it is for tunnel lining having an extension of about 10.5 m, which is generally used, because it is often not possible to keep up with the progress of the process of excavating the face surface of the concrete. By using a long-span tunnel lining formwork 10 having an extension of, for example, about 18 to 22 m, instead of the formwork, the construction span of the lining concrete 20 performed in one cycle is increased, and the lining is performed. It is possible to accelerate the progress of the process for forming the concrete 20. When the extension of the construction span of one cycle of the lining concrete 20 is increased by using the long-span tunnel lining mold 10, the drying shrinkage and temperature shrinkage of the concrete occur only at the boundary portion of the adjacent construction spans. Since cracks cannot be sufficiently absorbed and cracks due to drying shrinkage and temperature shrinkage are likely to occur in the middle part of the construction span, in this embodiment, the method of forming the induced joint described later is adopted and the middle part of the construction span is adopted. By providing an induced joint 25 that induces cracking due to drying shrinkage or temperature shrinkage in the portion, a concrete surface having good quality can be formed on the lining concrete 20.

Then, the method of forming the induced joint in the concrete structure of the present embodiment induces cracks across the lining concrete 20, which is a concrete structure constructed continuously in one direction with a predetermined thickness. A method for forming an induced joint 25 for forming the induced joint 25, which is a tunnel lining which is a concrete formwork for partitioning a lining space 21 which is a concrete placing space as shown in FIGS. 3 to 5. A plurality of plate members 26, which are projected from the formwork surface 15 on the outer peripheral portion of the formwork 10 toward the outer lining space 21 and whose surface is preferably covered with a friction reducing material containing a highly water-absorbent resin. The lining concrete 20 is continuously arranged in the circumferential direction, which is the transverse direction (see FIG. 3), and is attached to the tunnel lining formwork 10 so that it can be pulled out (see FIG. 4 (b)). When the concrete placed in the lining space 21 which is the concrete placing space is hardened, each plate member 26 is pulled out from the tunnel lining formwork 10 to obtain a desired position in the longitudinal direction of the lining concrete 20. Induction joints 25 (see FIG. 2) extending in the circumferential direction, which is the transverse direction, are formed.

In the present embodiment, the tunnel lining formwork 10 for forming the lining concrete 20 which is a concrete structure continuously constructed in one direction is a slide center movable in the excavation direction X of the tunnel 40. It is a long-span tunnel with an extension of about 18 to 22 m, for example. The tunnel lining formwork 10 has substantially the same configuration as the tunnel lining formwork described in, for example, Japanese Patent Application Laid-Open No. 2015-67749, except that the formwork 10 has a long span.

That is, as shown in FIGS. 1 and 2, the tunnel lining formwork 10 includes a gate type trolley 11 formed by connecting and integrating a plurality of gate type frames in the excavation direction X of the tunnel 40, and a gate type trolley. Formwork body supported by 11 and arranged along the inner peripheral surface of the tunnel 40 covered by, for example, a primary lining 23 with sprayed concrete, to form the formwork surface 15 inside the lining space 21. It is configured to include 12 and. The gate type carriage 11 includes a base portion 11a and a support column portion 11b that supports the base portion 11a. At the lower end of the column leg portion 11b, a traveling portion 11c that can travel along the rail 14 laid on the floor surface of the tunnel 40 is provided, whereby the tunnel lining formwork 10 is the tunnel 40. It is possible to move in the excavation direction X.

The formwork body 12 is assembled so as to have a shape along the inner peripheral surface of the tunnel 40 covered by the primary lining 23, and the formwork surface 15 of the outer peripheral portion is between the inner peripheral surface of the tunnel 40. By arranging the lining spaces 21 at predetermined intervals, a lining space 21 having a predetermined thickness is formed. Further, the formwork body 12 forms an upper formwork 12a that forms an upper lining space 21 of the arch-shaped portion 40b of the tunnel 40, and a lining space 21 of the lower portion of the arch-shaped portion 40b and the side wall portions 40a on both sides. A pair of side formwork 12b and a pair of lower end formwork 12c are included. The upper formwork 12a is supported so as to be able to move up and down in the vertical direction by a plurality of raising and lowering jacks 13a provided on the base portion 11a of the gate type carriage 11. The pair of side formwork 12b is rotatably connected to the lower ends of both sides of the upper formwork 12a, and the pair of lower end formwork 12c is rotatable to the lower end of each side formwork 12b. It is connected to the. The side formwork 12b and the lower end formwork 12c are connected to the other ends of the telescopic jacks 13b and 13c whose one end is connected to the gate type carriage 12, and these telescopic jacks 13b and 13c can be expanded and contracted. The side formwork 12b and the lower end formwork 12c can be rotated with respect to the upper formwork 12a and the side formwork 12b.

As a result, the formwork 10 for tunnel lining can expand and contract the formwork main body 12 by expanding and contracting the elevating jack 13a and the telescopic jacks 13b and 13c, so that the formwork body 12 can be expanded and put together inside the tunnel 40. The formwork body 12 can be assembled along the inner peripheral surface, or the formwork body 12 can be removed and then moved in the excavation direction X inside the tunnel 40.

In the present embodiment, the tunnel lining formwork 10 is a long-span formwork having an extension of, for example, about 18 to 22 m, so that the construction span can be increased and the construction period can be shortened. In addition to the above, it is preferably provided with a separable configuration so as to be in a state of being divided into two in the front-rear direction (tunnel excavation direction) X on one side and the other side. By making the tunnel lining formwork 10 separable to one side and the other side, the tunnel lining formwork 10 can be moved and set as a unit with a long span, and the time for moving and setting can be increased. While trying to shorten the length, when constructing the lining concrete 20 of different cross-section parts such as the wellhead part and the cross-section widening part of the tunnel 40, assembling the formwork of these different cross-section parts and curing the cast concrete. Even if it is necessary to hold the tunnel lining formwork 10 in the same position for a longer period than usual without moving it, for example, one part is held as it is and a different cross section is used. By separating the other part that is separated from the part, it becomes possible to proceed with the work of forming the lining concrete 20 by using the separated other part. This makes it possible to effectively avoid prolonging the process for forming the lining concrete 20 due to the influence of different cross-sectional portions.

Further, in the present embodiment, between the formwork surface 15 of the outer peripheral portion of the formwork body 12 formed by the formwork for tunnel lining 10 and the inner peripheral surface of 40 of the tunnel covered with the primary lining 23. Concrete is supplied to the lining space 21 of the above via two systems of concrete pumps (concrete pump trucks) 30 and pressure feed pipes 31. That is, in the present embodiment, as shown in FIG. 2, two concrete pumps 30 are arranged in front of and behind the tunnel excavation direction X sandwiching the set tunnel lining formwork 10. Concrete is poured into the hopper portion of each concrete pump 30 from the concrete mixer truck 32. A pressure feeding pipe 31 is connected to each of the two front and rear concrete pumps 30. Concrete can be simultaneously pumped and supplied from the two concrete pumps 30 to the lining space 21 via these two systems of pumping pipes 31. By using the two systems of the concrete pump 30 and the pumping pipe 31, it is possible to more effectively accelerate the progress of the process for forming the lining concrete 20. When two concrete pumps 30 are used, these two concrete pumps 30 shall be arranged side by side on one side (one side) in front of or behind the tunnel excavation direction X sandwiching the tunnel lining formwork 10. You can also.

Then, in the method of forming the induced joint of the present embodiment, as shown in FIGS. 3 and 4B, the lining space is formed from the formwork surface 15 of the outer peripheral portion of the formwork body 12 of the tunnel lining formwork 10. A plurality of plate members 26 whose surfaces are covered with a friction reducing material containing a highly water-absorbent resin, which is projected toward the 21 side and is preferably a friction reducing material, are formed in the front-rear direction (tunnel excavation) of the tunnel lining formwork 10. Direction) In the middle portion of X, the lining concrete 20 is continuously arranged in the circumferential direction and attached to the tunnel lining formwork 10 in a state where it can be pulled out from the inside of the tunnel lining formwork 10.

As shown in FIG. 4A, the plate member 26 is preferably made of aluminum or steel, for example, using a metal plate having a thickness of about 6 to 10 mm (in this embodiment, a thickness of about 9 mm). For example, a substantially rectangular shape having a vertical width of about 300 to 600 mm and a horizontal width of about 400 to 700 mm (in this embodiment, a vertical width of about 500 mm and a horizontal width of about 700 mm) and the upper and lower sides are slightly curved. It is formed to have a frontal shape. Further, the plate member 26 is substantially half of the outer side, which is arranged so as to project toward the lining space 21 outside the formwork surface 15 of the outer peripheral portion of the formwork body 12 of the tunnel lining formwork 10 with the formwork surface 15 interposed therebetween. The outer protrusion of the portion 26a and the formwork surface 15 of the outer peripheral portion of the formwork body 12 of the tunnel lining formwork 10 are sandwiched between the outer protrusion of the portion and the inner protrusion of the inner half portion arranged so as to project inward. It is configured to include the operation unit 26b.

As shown in FIG. 4B, the outer protruding buried portion 26a is inserted so as to extend in the circumferential direction on the formwork surface 15 of the outer peripheral portion of the formwork body 12 of the tunnel lining formwork 10. When the plate member 26 is inserted toward the lining space 21 through the slit 15a, the tunnel lining formwork 10 protrudes from the formwork surface 15 of the outer peripheral portion of the formwork body 12 by, for example, about 250 mm. Arranged so as to project outward at height. Further, the outer protruding buried portion 26a is a tapered portion 26c in which the thickness of the portion about 200 mm from the protruding tip portion is reduced from about 9 mm to about 2 mm toward the tip, whereby the lining concrete is formed. After the 20 is cured, the operation of pulling out the plate member 26 inside the tunnel lining formwork 10 can be performed more smoothly.

The inner protrusion operation portion 26b functions as a temporary fixing portion for fixing the plate member 26 to the tunnel lining formwork 10 until the concrete placed in the lining space 21 is hardened, and the concrete. The handle portion 26d for the handle is a portion that functions as a handle portion when the plate member 26 is pulled out to the inside of the tunnel lining formwork 10 after the concrete is hardened, and the handle portion 26d for the handle is located in a portion close to the lower side portion. It projects on both sides and is provided as a unit.

The outer protruding embedded portion 26a of the plate member 26 was inserted toward the lining space 21 via the insertion slit 15a extending in the circumferential direction on the formwork surface 15 of the outer peripheral portion of the formwork main body 12. In this state, as shown in FIG. 4B, for example, the back surface portion of the handle portion 26d is spot-welded to the support steel material 12d fixed to the inside of the formwork body 12 of the formwork 10 for tunnel lining by welding or the like. By equalizing, the plate member 26 can be joined to the support steel material 12d so as to be breakable. As a result, each of the plurality of plate members 26 that are continuously arranged in the circumferential direction of the lining concrete 20 in a state where the outer protruding buried portion 26a is projected toward the lining space 21 is provided with the tunnel lining formwork 10. In addition, it becomes possible to temporarily fix it in a stable state.

Further, when the plate member 26 is pulled out to the inside of the tunnel lining formwork 10 after the concrete placed in the lining space 21 is hardened, the back surface of the handle portion 26a to which the plate member 26 is fragilely spot-welded or the like is formed. By breaking the joint portion of the portion, the temporarily fixed state can be released, and the plate member 26 can be pulled out. The operation of pulling out the plate member 26 can be easily performed while gripping the handle portion 26d provided on the inward projecting operation portion 26b.

Further, in the present embodiment, as shown in FIG. 4, the outer protruding buried portion 26a is projected from the formwork surface 15 of the outer peripheral portion of the tunnel lining formwork 10 toward the lining space 21 side, and the tunnel lining formwork is formed. The plurality of plate members 26 which are continuously arranged in the circumferential direction of 10 are preferably arranged so as not to form a gap between the side edges of each pair of adjacent plate members 26. Further, a part of the plurality of plate members 26 arranged in a series thereof spreads inward, in which the distance between the side edges on both sides is widened from the outside to the inside of the lining space 21. It is a V-shaped plate member 26'having the front shape of.

A part of the plurality of plate members 26 arranged continuously in the circumferential direction has a C-shaped plate member 26'with a space between the side edges on both sides extending toward the inside of the lining space 21. By pulling out the C-shaped plate member 26'in advance, the plate members 26 serially arranged in the circumferential direction of the tunnel lining formwork 10 are adjacent to each other. It is possible to avoid difficulty in pulling out due to the side edges of 26 competing with each other, and to smoothly pull out each plate member 26.

Further, in the present embodiment, each of the plurality of plate members 26 serially arranged in the circumferential direction of the tunnel lining formwork 10 is arranged so as to project at least toward the lining space 21 side. The surface of the material is preferably covered with a friction reducing material containing, for example, a highly water-absorbent resin as a material that absorbs water and swells. As the friction reducing material containing a highly water-absorbent resin, a friction reducing material containing an acrylic resin having high water absorption can be preferably used. More specifically, in order to facilitate the extraction of steel materials such as H-shaped steel, which are buried in the ground as temporary earth retaining core materials in civil engineering work, for example, they are pre-coated or pasted on the surface of the steel materials. The trade name "friction cutter" (manufactured by Nippon Shokubai Co., Ltd.), which is known as a friction reducing material, can be used. The friction reducing material containing the highly water-absorbent resin covers at least the surface of the outer protruding embedded portion 26a by being coated as a coating agent or attached as a covering material, and is applied to each of the plurality of plate members 26. It can be easily attached.

The surface of the outer protruding embedded portion 26a of each of the plurality of plate members 26 sequentially arranged in the circumferential direction of the tunnel lining formwork 10 so as to project toward at least the lining space 21 side is preferably highly water-absorbent. By being covered with a friction reducing material containing a sex resin, the highly absorbent resin absorbs the moisture in the cast concrete, so that even after the concrete is hardened, the surface of the plate member 26 is surrounded by the surroundings. It will be possible to keep the hardened concrete and the edge cut. As a result, for example, the pulling action force that can be easily pulled out by a human hand of about 20 kN does not damage the hardened lining concrete 20 after a predetermined curing period, and each plate member. By smoothly pulling out 26 and sequentially removing it, it becomes possible to easily form the induced joint 25 extending in the circumferential direction of the lining concrete 20.

Therefore, according to the method for forming induced joints in the concrete structure of the present embodiment, the construction span of one cycle of the lining concrete 20 which is a concrete structure continuously constructed in one direction to a predetermined thickness Induced joints 25 that induce cracks due to drying shrinkage and temperature shrinkage of concrete can be easily provided in the intermediate portion without much labor.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, the concrete structure in which the induced joint is formed by the method for forming the induced joint of the present invention and is constructed continuously in one direction to a predetermined thickness does not necessarily have to be tunnel lining concrete, for example, a road. It may be various other concrete structures constructed continuously in one direction, such as a concrete slab forming a bridge. Further, the friction reducing material that covers the surface of the pullable plate member does not necessarily have to be a friction reducing material containing a highly water-absorbent resin, and is cured in addition to other friction reducing materials including a material that absorbs water and swells. Various known friction reducing materials may be used, which enable the plate member to be easily pulled out from the concrete after the work, for example, by the force of a human hand.

10 Formwork for tunnel lining 11 Gate type trolley 11a Base part 11b Strut leg part 11c Running part 12 Formwork body 12a Upper formwork 12b Lower formwork 12c Lower end formwork 13a Elevating jack 13b, 13c Telescopic jack 14 Rail 15 Formwork surface 15a Insertion slit 20 Tunnel lining concrete 21 lining space 23 Primary lining 25 Induced joint 26 Plate member 26'H-shaped plate member 26a Outer protrusion embedded part 26b Inner protrusion operation part 26c Tapered part 27a Hand hole 27b Overhang tightening rib 27c Locking hole 28a Fixing bolt 28b Nut 30 Concrete pump (concrete pump car)
31 Pumping pipe 32 Concrete mixer truck 40 Tunnel 40a Side wall part 40b Arch-shaped part X Tunnel digging direction (front-back direction of tunnel lining formwork)

Claims (6)

A method for forming induced joints in a concrete structure for forming induced joints that induce cracks across a concrete structure constructed continuously in one direction to a predetermined thickness.
A plurality of plate members are connected to each other so as not to create a gap in the transverse direction of the concrete structure by projecting from the formwork surface of the concrete formwork that divides the concrete placing space toward the placing space. A letter "H" in which a part of the plurality of plate members arranged in a row is spread out in the direction of pulling out from the casting space at a distance between the side edges on both sides. As a shaped plate member, it is attached to a concrete formwork so that it can be pulled out, and when the concrete placed in the concrete placing space is hardened, the U -shaped plate member is pulled out from the concrete formwork in advance, and each A method for forming an induced joint in a concrete structure, which forms an induced joint extending in a transverse direction at a desired position of the concrete structure by pulling out the plate member. The concrete structure is a tunnel lining concrete formed by using a tunnel lining formwork as the concrete formwork, and the plurality of plate members are formed from a formwork surface of an outer peripheral portion of the tunnel lining formwork. The induced joint in the concrete structure according to claim 1 , which is projected outward and is arranged in a continuous manner adjacent to the tunnel lining formwork in the circumferential direction and is removably attached to the tunnel lining formwork. Forming method . The tunnel lining concrete is constructed to have a thickness of 300 to 500 mm, and the plurality of plate members have a height of 100 to 250 mm from the formwork surface of the outer peripheral portion of the tunnel lining formwork. The method for forming an induced joint in the concrete structure according to claim 2, wherein the concrete structure is continuously arranged so as to project outward. The method for forming an induced joint in a concrete structure according to any one of claims 1 to 3, wherein the plurality of plate members are metal plates made of aluminum or steel. The concrete structure according to any one of claims 1 to 4 , wherein the surface of the plurality of plate members is covered with a friction reducing material, and the friction reducing material contains a material that absorbs water and swells. How to form a trigger joint. The method for forming an induced joint in a concrete structure according to claim 5, wherein the friction reducing material contains a highly water-absorbent resin.

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