JP7179282B2 - Tunnel center joint formation structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a joint forming structure for a tunnel center, and more particularly to a joint forming structure capable of effectively preventing cracks in existing concrete.

The lining concrete of the tunnel is formed by successively moving the center, injecting concrete between the excavated inner circumference of the tunnel and the outer circumference of the center, and curing the concrete. At this time, joints are formed at the joints of adjacent concretes in order to prevent chipping of corner portions. When the center formwork is moved, it is once contracted and detached from the inner peripheral surface of the existing concrete. At this time, there is often a problem that the inner peripheral surface of the existing concrete is pushed up excessively, causing cracks in the concrete.

Therefore, in Patent Document 1, the formwork is positioned at a position that does not interfere with the existing concrete in the longitudinal direction, and at the end of the formwork, a receiving member having a structure in which a receiving plate is attached to the tip of the shaft body is provided. The joint material for forming the joint is moved along the outer periphery of the formwork toward the existing concrete, and the joint material is supported by the receiving plate, thereby avoiding interference between the formwork and the existing concrete. A joint forming structure has been proposed in which a projecting portion is formed following a concave cross-sectional shape.

JP 2015-151774

However, the above-described conventional structure has a problem that the structure of the receiving member is complicated and that such a receiving member needs to be provided at a plurality of positions in the circumferential direction of the end portion of the formwork, resulting in an increase in cost.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a tunnel center joint formation structure that can reliably prevent cracks from occurring in existing concrete when a formwork is deployed in a simple and inexpensive manner. do.

In order to achieve the above object, in the first invention, the rear end (11 ) is provided with a receiving member (2) extending to an inner position away from the front end portion inner peripheral surface of the lining concrete (Cr), and a joint material (3) is provided inside the front end portion of the lining concrete (Cr) It is mounted on the outer periphery of the formwork (1) so as to be movable back and forth along the outer peripheral surface of the formwork (1) independently of the formwork (1) toward the notch (Cc) formed in the periphery. At the same time, the bottom surface of the rear end of the joint material (3) is underlined , and the projecting end of the joint material (3) projects toward the receiving member (2) and contacts the outer peripheral surface of the receiving member (2). ) is moved back and forth, a support leg (31) is provided to maintain the posture of the joint material (3) during the back and forth movement, and the joint material (3) is moved backward to partially move the joint material (3). A protrusion (P) is formed following the concave cross-sectional shape of the joint of the new lining concrete while being inserted into the notch (Cc).

In the first aspect of the present invention, the formwork is placed at a position that does not interfere with the existing lining concrete in the longitudinal direction, and only the receiving member faces the notch space of the lining concrete. This avoids the formwork interfering with the lining concrete when the formwork is deployed. Therefore, the inner peripheral surface of the existing lining concrete is prevented from being pushed up excessively and causing cracks in the concrete.

In this state, the joint material located on the outer periphery of the frame is moved along the outer periphery in the direction of the existing lining concrete (rearward with respect to the direction of progress of formwork placement), and a part of it is moved into the notch. to form a protrusion that follows the concave cross-sectional shape of the joint of the new lining concrete.

During this movement, the joint material is always supported on the receiving member by the supporting legs, so that its posture does not change, and the joint material is properly inserted into the notch of the existing concrete. Even if the position of the formwork shifts toward or away from the existing lining concrete, since the supporting legs are always supported by the receiving members, the posture of the joint material does not change.

In the second aspect of the invention, the rear side surface of the joint material (3) is formed into an inclined surface following the notch (Cc).

According to the second aspect of the invention, even if the position of the formwork is displaced in the vertical direction with respect to the existing lining concrete, the joint material is displaced upward or downward in contact with the inclined surface while being supported by the receiving member. The posture of the joint material does not change. Therefore, in this case as well, the joint material is properly inserted into the notch of the existing concrete, and the protruding portion following the concave cross-sectional shape of the joint of the new lining concrete is formed satisfactorily.

In the third invention, a cushion body (5) having a predetermined thickness is provided on the outer peripheral surface of the receiving member (2) facing the inner peripheral surface of the lining concrete (Cr).

According to the third aspect of the present invention, the provision of the cushion body prevents the receiving member, which rises when the formwork is deployed, from directly colliding with the inner peripheral surface of the existing lining concrete, thereby further reducing the occurrence of cracks. can be reliably prevented. Also, by matching the top surface of the cushioning body with the height of the surface of the formwork, the height of the formwork set can be monitored by the operator, and the set state can be easily determined.

In the fourth invention, one end of a pull rope (4) for moving the joint material (3) backward is fixed to the support leg (31) .

The symbols in parentheses above refer to the corresponding relationship with specific means described in the embodiments described later.

As described above, according to the tunnel center joint formation structure of the present invention, it is possible to reliably prevent cracks from occurring in the existing concrete when the forms are unfolded in a simple and inexpensive manner.

It is a longitudinal cross-sectional view of a joint formation structure. FIG. 2 is a cross-sectional view of the joint forming structure, taken along the line II--II in FIG. 1; FIG. 4 is a vertical cross-sectional view of the joint forming structure when moving to approach the formwork; FIG. 4 is a vertical cross-sectional view of the joint forming structure when the formwork is moved apart; It is a vertical cross-sectional view of the joint forming structure during the downward movement of the formwork. It is a vertical cross-sectional view of the joint forming structure during the upward movement of the formwork.

The embodiments described below are merely examples, and various design improvements made by those skilled in the art are also included in the scope of the present invention without departing from the gist of the present invention.

FIG. 1 shows an example of the joint forming structure of the present invention. In FIG. 1, when the lining concrete Cr has been placed, the formwork 1 of the tunnel center is contracted and lowered, and the face from the inside of the placed existing lining concrete Cr (hereinafter referred to as "existing concrete"). After that, the formwork 1 is deployed and raised again so that the rear end 11 is positioned close to the front end of the existing concrete Cr as shown in FIG. Normally, the outer peripheral surface 1a of the formwork 1 is positioned substantially flush with the inner peripheral surface of the existing concrete Cr.

A plurality of stays 21 protrude from the end surface of the formwork 1 in the circumferential direction (FIG. 2). there is The receiving member 2 is located inside the outer periphery of the formwork 1 by a certain amount (Fig. 1), and its plate width direction (horizontal direction in Fig. 1) is inside away from the end inner peripheral surface of the existing concrete Cr. It extends in a predetermined length to the direction position.

A joint material 3 is arranged along the outer periphery of the end portion 11 of the formwork 1 . The joint material 3 is an elongated body having a substantially triangular cross section, and is obtained by extruding a rubber material or the like. The bottom of the triangular cross section of the joint material 3 is located on the outer periphery of the end 11 of the formwork 1, and can be moved back and forth (horizontal direction in FIG. 1) with respect to the front end of the existing concrete Cr along the outer peripheral surface.

On the bottom surface of the rear end portion of the joint material 3 protruding from the outer periphery of the end portion 11 of the formwork 1 in the direction of the existing concrete Cr in the casting progress direction, a constant thickness protruding toward the plate surface serving as the outer peripheral surface of the receiving member 2 is provided. A wall-shaped support leg portion 31 is formed, and the projecting end surface (lower end surface) of the support leg portion 31 abuts the plate surface of the receiving member 2 . By such support legs 31 , the joint material 3 protruding from the end portion 11 of the formwork is held substantially as an extension of the outer peripheral surface 1 a of the formwork 1 .

The supporting leg portion 31 of the joint material 3 is provided with a through hole 311 parallel to the plate surface of the receiving member 2 at an appropriate position in the circumferential direction. 311 and extends along the inside of the existing concrete Cr. A circular through hole 32 is formed in the center of the cross section of the joint material 3 in the longitudinal direction. By passing a fixing rope through the through hole 32 and tightening both ends of the fixing rope, the diameter of the joint material 3 is reduced and deformed. and fixed to the outer peripheral surface 1a of the formwork 1.

A plurality of cushion bodies 5 having a thickness approximately equal to the length of the support leg portion 31 are joined and fixed to the plate surface of the receiving member 2 at intervals in the circumferential direction (FIG. 2). Further, a limit switch 6 is installed on the receiving member 2 between the cushion bodies 5 located in the top region of the formwork 1, and its actuator 61, which moves back and forth, is directed toward the inner peripheral surface of the existing concrete Cr. Note that the actuator 61 is biased in the advancing direction.

In such a joint formation structure, when a new lining concrete is placed following the existing concrete Cr, as already explained, the formwork 1 of the tunnel center is moved from the inside of the existing concrete Cr to the face side. The drawer (FIG. 1) moves the rear end 11 of the formwork 1 to a position close to its front end so as not to interfere with the existing concrete Cr. The formwork 1, which was contracted and lowered by a known structure during movement, is deployed and raised again after movement.

At the time of this rise, the receiving member 2 is buffered by the cushion body 5 so that it does not directly collide with the inner peripheral surface of the existing concrete Cr. A formwork rise stop signal is output. In this state, the outer peripheral surface 1a of the formwork 1 is substantially flush with the inner peripheral surface of the existing concrete Cr as described above.

Subsequently, the joint material 3 positioned on the outer peripheral surface 1a of the formwork 1 as indicated by the chain line in FIG. 1 is pulled out toward the existing concrete Cr by pulling the rope 4 as indicated by the arrow in FIG. As shown by the solid line in FIG. 1, the inclined side surface of the joint material 3 is aligned with the slope of the notch Cc formed in the inner circumference of the end of the existing concrete Cr, and approximately half of the joint material 3 is placed in the notch Cc. insert into By pulling the rope 4 in this manner, the joint material 3 can be easily and reliably pulled out toward the existing concrete Cr.

During this movement, the joint material 3 is always supported on the receiving member 2 by the supporting legs 31, so that its posture does not change, and the joint material 3 is properly inserted into the notch Cc of the existing concrete Cr. be done. As a result, a new concrete placing space S continuous with the existing concrete Cr is formed between the outer periphery of the formwork 1 and the inner periphery of the tunnel. Protrusions P are formed for forming joints.

The moving position of the tunnel center and the rising position of the formwork 1 produce an error within a certain range. According to the structure of this embodiment, even when the formwork 1 is too close to the existing concrete Cr from the target position (Fig. 1) (Fig. 3) or too far apart (Fig. 4), the supporting legs Since the portion 31 is always on the plate surface of the receiving member 2 and is supported by it, the posture of the joint material 3 does not change. P is properly formed.

Further, even if the position of the formwork 1 deviates downward (FIG. 5) or upward (FIG. 6) from the target position (FIG. 1), the supporting legs 31 are always kept on the plate surface of the receiving member 2. Since the joint material 3 is supported by this, the posture of the joint material 3 does not change, and the joint material 3 is displaced downward or upward while being in contact with the slope of the notch Cc. At this time, the triangular concave cross-sectional shape of the joint formed by the protruding portion P is slightly deformed, but there is no practical problem.

According to the present embodiment, the joint material 3 having the support legs 31 can be integrally molded easily and inexpensively by extrusion molding or the like, and the receiving member 2 that receives the support legs 32 also extends circumferentially with a predetermined width. Since it is sufficient to use a simple elongated plate, the joint formation structure can be generally realized easily and inexpensively.

The formwork 1 is positioned so as not to interfere with the existing concrete Cr in the longitudinal direction, and the receiving member 2 is provided with a cushion body 5 to prevent the receiving member 2 from directly colliding with the inner peripheral surface of the existing concrete Cr. In addition, since the limit switch 6 is provided to reliably prevent the collision between the receiving member 2 and the inner peripheral surface of the existing concrete Cr, the inner peripheral surface of the existing concrete Cr is pushed up excessively and cracks occur in the concrete Cr. can be effectively prevented from occurring.

The cushion body 5 and the limit switch 6 are not necessarily required, and the cross-sectional shape of the joint material 3 is not limited to a triangular cross-section. In addition, it is not necessarily limited to the limit switch, and other proximity detection means such as a proximity switch can be used.

DESCRIPTION OF SYMBOLS 1... Form, 11... End, 2... Receiving member, 3... Joint material, 31... Support leg, 5... Cushion body, 6... Limit switch (approach detection means), Cr... Existing concrete (existing lining Concrete), Cc... Notch, P... Projection.

Claims (4)

A receiving member extending inwardly away from the inner peripheral surface of the front end portion of the existing lining concrete at the rear end portion of the formwork positioned close to the front end portion located on the face side of the existing lining concrete. is provided, and the joint material is movable back and forth along the outer peripheral surface of the formwork independently of the formwork toward the notch formed on the inner circumference of the front end of the lining concrete. and is mounted on the bottom surface of the rear end of the joint material, protruding toward the receiving member, and the projecting end thereof contacts the outer peripheral surface of the receiving member, and when the joint material is moved back and forth, the front and back A support leg is provided to maintain the posture of the joint material during movement, and the concave cross section of the joint of the new lining concrete is provided in a state where the joint material is moved backward and partly inserted into the notch. A tunnel center joint formation structure in which a protrusion is formed that follows the shape. 2. The tunnel center joint forming structure according to claim 1, wherein the rear side surface of the joint material is formed as an inclined surface following the notch. 3. The tunnel center joint formation structure according to claim 1, wherein a cushion body having a predetermined thickness is provided on the outer peripheral surface of the receiving member facing the inner peripheral surface of the lining concrete. 4. The tunnel center joint formation structure according to claim 1, wherein one end of a pull rope for moving said joint material backward is fixed to said support leg .

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