JP7701039B2 - Lining centre and lining concrete pouring method - Google Patents

Description

The present invention relates to a lining center and a method for pouring lining concrete.

In the construction of mountain tunnels, a construction direction may be applied in which lining concrete is poured into the pouring space between the ground and the center form (form) of the lining center (simply called center), which is a steel form that can be moved in the direction of tunnel excavation, and after the lining concrete has developed a predetermined strength, the lining center is moved and the same construction of pouring lining concrete is repeated in sequence.

The lining center is equipped with a gantry (carriage) and a center form supported by the gantry. Rails are laid on the tunnel roadbed for the lining center to move on, and the gantry is generally configured to move along the rails. After the lining concrete is poured between the center form and the ground, when the lining concrete has developed a certain strength, the center form is moved to the inside of the tunnel and removed from the form, a process known as center down, making the lining center movable.

However, in the method of sequentially laying the lining concrete in the direction of tunnel excavation using the above-mentioned lining centering, due to the balance with the overall tunnel construction process, centering down is often carried out at a stage when the poured lining concrete is still at a weak material age and has not yet developed sufficient strength. And when centering down is carried out at a stage when the concrete has not yet developed sufficient strength, the lining concrete displaces downwards due to its own weight, and this displacement causes cracks to form in the lining concrete, which is an issue.

There are various possible factors that can cause cracks in the lining concrete, but when centre-down is performed at a stage when strength development is insufficient, downward displacement of the lining concrete due to its own weight is one of the main factors. Therefore, in order to shorten the construction period, even when centre-down is performed at a stage when the lining concrete is still at a weak material age and has not yet developed sufficient strength, a method of pouring the lining centre and lining concrete that can suppress cracks that can occur in the lining concrete is desired.

Patent Document 1 proposes a centering system in which the outer periphery of a frame body that can be expanded or contracted is positioned inward along the inner periphery of an excavated tunnel, and lining concrete is poured into the closed space formed between the outer periphery of the frame body when expanded and the inner periphery of the excavated tunnel. This centering system is equipped with a pressure detection means for detecting the contact pressure with the lining concrete on the outer periphery of the end of the frame body on the side of the existing lining concrete.

JP 2019-44477 A

According to the centering technique described in Patent Document 1, the contact pressure of the frame body against the existing lining concrete can be directly detected and managed, so that excessive contact pressure is not applied to the lining concrete, and it is possible to prevent cracks in the construction joints. However, it is not possible to prevent the above-mentioned problem, i.e., the downward displacement of the lining concrete due to its own weight caused by centering down, which causes cracks in the lining concrete due to this displacement.

The present invention was made in consideration of the above problems, and aims to provide a method for pouring lining centering and lining concrete that can suppress cracks that may occur in the lining concrete, even when centering down is performed at a stage when the lining concrete is still at a weakened age and has not yet fully developed its strength.

In order to achieve the above object, one embodiment of the lining center according to the present invention is as follows:
A lining center applied when pouring lining concrete for a tunnel,
The lining center has a gantry and a center form supported by the gantry,
The central form includes a crown portion at the center, arch portions on the left and right sides of the crown portion, and side wall portions on the sides of the arch portions and below the left and right sides of the central form,
A prestress force is introduced into at least the crown portion of the center form, pulling it toward the inner space of the tunnel.

According to this embodiment, a prestress force is introduced to at least the crown portion of the center form, which pulls it toward the interior of the tunnel, and the circumferential alignment of the center form is approximated in advance to the displacement line when the weight of the lining concrete acts on it. By pouring the lining concrete into the center form that has been deformed in advance in this way to support it, even if centering down is performed at a stage when the lining concrete is still at a weak material age and has not yet fully developed its strength, downward displacement due to the weight of the lining concrete does not occur, or is unlikely to occur, and cracks caused by this downward displacement can be suppressed. This makes it possible to shorten the construction period of the tunnel while suppressing cracks that may occur in the lining concrete.

According to this embodiment, when the lining concrete is poured, the center form has already formed a displacement line that deforms due to the weight of the lining concrete, so the displacement of the center form is suppressed or prevented, and the poured lining concrete can gradually harden and develop strength without being affected by the displacement of the center form. As a result, when the center form is centered down at a weak material age when centering down is possible, the lining concrete is not affected by the displacement of the center form at the strength development stage up to that point, and cracks in the lining concrete are suppressed.

Here, "prestress force is introduced at least to the crown portion" means that in addition to prestress force being introduced only to the crown portion of the central form, it also includes a form in which prestress force is introduced to the crown portion and arch portion, a form in which prestress force is introduced to the crown portion and side wall portion, and a form in which prestress force is introduced to the crown portion, arch portion, and side wall portion.

In either form, by pulling downward (vertically or diagonally) the crown portion, where the displacement due to the weight of the lining concrete is greatest, it becomes easier to form a displacement line where the weight of the lining concrete deforms against the center form. Also, by pulling the crown portion downward, the arch portion may conversely deform so that it bulges toward the ground, but by pulling the arch portion toward the interior space of the tunnel, for example, it is possible to suppress excessive bulging of the arch portion toward the ground. In addition to directly pulling the arch portion, excessive bulging of the arch portion toward the ground can also be suppressed by pulling the side wall portion adjacent to the arch portion.

Another aspect of the lining centre according to the present invention is as follows:
The crown portion and the side wall portion of the center form are connected by a prestress force introducing means, and both the crown portion and the side wall portion are tensioned.

According to this aspect, the crown portion and the side wall portion are connected by a prestress force introduction means, and both the crown portion and the side wall portion are pulled by a common prestress force introduction means, so that it is possible to both achieve downward displacement of the crown portion and suppress the protrusion of the arch portion toward the ground with as few prestress force introduction means as possible.

Another aspect of the lining centre according to the present invention is as follows:
A prestress force introduction means is provided on both the crown portion and the arch portion of the central form, and the prestress force introduction means applies a reaction force of the prestress force to the gantry;
When the gantry rises due to the prestress force, a counterweight is attached to the gantry to prevent the gantry from rising, or the legs of the gantry grip the rails along which the gantry moves to prevent the gantry from rising.

According to this aspect, the prestress force introduction means provided on both the crown portion and the arch portion are attached to the gantry, respectively, and the reaction force of the prestress force can be easily absorbed by the heavy gantry. On the other hand, when the prestress force is large and the gantry rises due to the prestress force, a form in which a counterweight is attached to the gantry or a form in which the legs of the gantry grip the rails on which the gantry moves can be applied, thereby effectively preventing the gantry from rising due to the prestress force.

Another aspect of the lining centre according to the present invention is as follows:
The crown portion and the arch portion of the center form are connected by a prestress force introduction means, and the arch portion and the gantry are connected by a separate prestress force introduction means so that the gantry receives a reaction force of the prestress force,
When the gantry rises due to the prestress force, a counterweight is attached to the gantry to prevent the gantry from rising, or the legs of the gantry grip the rails along which the gantry moves to prevent the gantry from rising.

According to this aspect, the crown portion and the arch portion are connected by a prestress force introduction means, and the arch portion is attached to the gantry by a separate prestress force introduction means, and the reaction force of the prestress force is absorbed by the heavy gantry. On the other hand, when the prestress force is large and the gantry floats up due to the prestress force, a form in which a counterweight is attached to the gantry or a form in which the legs of the gantry grip the rails on which the gantry moves can be applied, thereby effectively preventing the gantry from floating up due to the prestress force.

Another aspect of the lining centre according to the present invention is as follows:
a prestress force introduction means is provided on each of the crown portion, the arch portion and the side wall portion of the central form, and the prestress force introduction means applies a reaction force of the prestress force to the gantry;
When the gantry rises due to the prestress force, a counterweight is attached to the gantry to prevent the gantry from rising, or the legs of the gantry grip the rails along which the gantry moves to prevent the gantry from rising.

According to this aspect, the prestress force introduction means provided on the crown portion, the arch portion, and the side wall portion are each attached to the gantry, and by taking up the reaction force of the prestress force, it becomes possible for the heavy gantry to easily take up the reaction force of the prestress force. On the other hand, when the prestress force is large and the gantry rises due to the prestress force, a form in which a counterweight is attached to the gantry or a form in which the legs of the gantry grip the rails on which the gantry moves can be applied, thereby effectively preventing the gantry from rising up due to the prestress force.

In another embodiment of the lining center according to the present invention,
The magnitude of the prestress force is such that it imparts to the crown portion a pre-pouring displacement amount corresponding to the downward displacement amount of the crown portion when the lining concrete is poured.

According to this embodiment, the magnitude of the prestress force is equivalent to the amount of downward displacement of the crown when the lining concrete is poured, so that the displacement of the crown of the center form when the lining concrete is poured can be eliminated, and cracks in the lining concrete caused by the displacement of the crown can be prevented.

Another aspect of the lining centre according to the present invention is as follows:
The prestress force introduction means is characterized in that the prestress force is gradually released from the pouring of the lining concrete until the pouring is completed.

According to this embodiment, the prestress force is gradually released from the time the lining concrete is poured until the pouring is completed, which gradually changes the amount of displacement of the central form as the lining concrete develops its strength, making it possible to keep the amount of displacement of the lining concrete, which may change as the concrete develops its strength, constant.

Another aspect of the lining centre according to the present invention is as follows:
The prestress force introducing means is characterized by being PC steel.

According to this embodiment, the prestress force introduction means is a PC steel material, which makes it easy to install it on a central form or gantry, and also makes it easy to manage the introduction of the prestress force. Here, PC steel materials include PC steel bars and PC steel wires, etc.

Another aspect of the lining centre according to the present invention is as follows:
The prestress force introducing means is a jack.

According to this aspect, the prestress force introduction means is a jack, which makes it easy to install it on a central form or gantry, and also makes it easy to manage the introduction of the prestress force. Here, examples of jacks include hydraulic jacks, air jacks, electric jacks, etc.

In addition, one aspect of the method for pouring lining concrete according to the present invention is to
A method for pouring lining concrete for a tunnel using a lining center having a gantry and a center form supported by the gantry, the center form having a central crown portion, left and right arch portions of the crown portion, and side wall portions on the sides of the arch portions and below the left and right of the center form, comprising:
A process in which, before pouring the lining concrete, a prestress force is introduced into at least the crown portion of the center form to pull it toward the inside of the tunnel, thereby imparting a pre-casting displacement to the crown portion that corresponds to a downward displacement of the crown portion when the lining concrete is poured; and
and step B of pouring the lining concrete between the ground and the centre form.

According to this embodiment, by introducing a prestress force into at least the crown part of the center form and pulling it toward the inside of the tunnel, the circumferential alignment of the center form is approximated in advance to the displacement line when the weight of the lining concrete acts on it, and the lining concrete is poured and supported on the center form thus deformed in advance. Even if centering down is performed at a stage when the lining concrete is still at a weak material age and has not yet fully developed its strength, downward displacement due to the weight of the lining concrete does not occur or is unlikely to occur, so cracks caused by this downward displacement can be suppressed. This makes it possible to shorten the construction period of the tunnel while suppressing cracks that may occur in the lining concrete.

Another aspect of the method for pouring lining concrete according to the present invention is as follows:
In the step B, the prestress force is adjusted so that the load is gradually released from the pouring of the lining concrete until the end of pouring.

According to this embodiment, the prestress force is gradually released from the time the lining concrete is poured until the pouring is completed, which gradually changes the amount of displacement of the central form as the lining concrete develops its strength, making it possible to keep the amount of displacement of the lining concrete, which may change as the concrete develops its strength, constant.

As can be understood from the above explanation, the lining centering and lining concrete pouring method of the present invention can suppress cracks that may occur in the lining concrete, even when centering down is performed at a stage when the lining concrete is still at a weakened age and has not yet fully developed its strength.

FIG. 2 is a front view of the lining center for the first embodiment, showing the bending moment acting on the center form when the lining concrete is poured, as well as the displacement in the crown and arch portions of the center form. FIG. 2 is a diagram showing a state in which prestress force is introduced into the prestress force introduction means in the lining center relating to the first embodiment. FIG. 11 is a front view of the lining center for the second embodiment, showing the state in which prestress force is introduced into the prestress force introduction means. FIG. 13 is a front view of the lining center for the third embodiment, showing the state in which prestress force is introduced into the prestress force introduction means. FIG. 13 is a front view of the lining center for the fourth embodiment, showing the state in which prestress force is introduced into the prestress force introduction means. FIG. 13 is a front view of the lining center for the fifth embodiment, showing the state in which prestress force is introduced into the prestress force introduction means.

Below, an example of a method for pouring the lining center and lining concrete according to each embodiment will be described with reference to the attached drawings. Note that in this specification and the drawings, substantially identical components may be designated by the same reference numerals to avoid redundant explanation.

[Linding center according to the first embodiment and lining concrete pouring method according to the embodiment]
First, an example of a lining center according to the first embodiment and an example of a method of pouring lining concrete according to the embodiment will be described with reference to Figures 1 and 2. Here, Figure 1 is a front view of the lining center according to the first embodiment, showing the bending moment acting on the center form when lining concrete is poured, and also showing the displacement in the crown part and the arch part of the center form. Also, Figure 2 is a view showing the state in which prestress force is introduced to the prestress force introduction means in the lining center according to the first embodiment.

The lining center 100 has a gate-shaped gantry 10 and a center form 20 supported by support members 25, 26, and 27 extending vertically, horizontally, and diagonally from the gantry 10. The gantry 10 is a gate-shaped mobile platform with wheels 12 at the lower ends of the left and right legs 11 (the legs 11 and wheels 12 form the legs 13), allowing the gantry 10 to move along rails R laid in the longitudinal direction of the tunnel T on the roadbed B of the tunnel T.

The center form 20 is formed by a group of forms consisting of multiple forms 21 arranged in the circumferential and longitudinal directions of the tunnel T. The center form 20 has a length of, for example, about 10 m in the longitudinal direction of the tunnel T, and a gable formwork (not shown) is provided at the end of the center form 20 in the longitudinal direction of the tunnel T.

The central form 20 can be formally divided into three main regions: a central crown portion, arch portions on the left and right of the crown portion, and side wall portions on the sides of the arch portions and below the left and right of the central form 20.

Inside the wall of a horseshoe-shaped or circular hole, as shown in the example shown, which is created in the natural ground G by blasting or mechanical excavation, lining rebar (not shown) is arranged in both the circumferential and longitudinal directions of the tunnel T before the lining center 100 arrives. Then, as shown in FIG. 1, when the lining center 100 arrives, a pouring space S is formed between the center form 20 and the hole wall, into which lining concrete is poured. Here, if sprayed concrete has been applied to the inner surface of the hole wall, a pouring space S is formed between the center form 20 and the shotcrete.

The central form 20 has multiple inspection hatches (not shown). These inspection hatches are openings through which the nozzle of a pouring hose (not shown) extending inside the tunnel T passes and faces the pouring space S, allowing concrete to be poured into the pouring space S, and also allow a vibrator to be inserted into the pouring space S, and are also openings for checking the pouring status of the concrete.

In the method of sequentially constructing lining concrete C in the direction of tunnel excavation using lining centering, due to the balance with the overall tunnel construction process, centering down is often carried out at a stage when the poured lining concrete C is still at a weak material age and has not yet developed sufficient strength. And when centering down is carried out at a stage when it has not yet developed sufficient strength, the lining concrete C displaces downwards due to its own weight, and this displacement causes the problem of cracks occurring in the lining concrete.

For example, as shown in FIG. 1, when lining concrete C is poured into the pouring opening S, a bending moment M is generated in the central form 20 due to the weight of the lining concrete C, and at the same time, each part is displaced due to the weight of the lining concrete C. In general, the maximum bending moment is generated in the crown part of the central form 20, and a maximum downward displacement δ1 is also generated.

As shown in Figure 1, the bending moment M may be reversed, for example, at the arch of the central form 20, and then a moment distribution may occur in which the bending moment converges to zero toward the lower end of the side wall. A maximum downward displacement δ1 may occur at the crown, and a displacement δ2 (< δ1) toward the natural ground may occur at the arch. However, the actual displacement δ2 at the arch is less than δ2 because the central form 20, which is about to be displaced, is pushed back toward the interior of the tunnel T by the poured lining concrete C.

In any case, cracks C1 may occur on the tunnel interior side of the crown part of the lining concrete C due to the maximum downward displacement δ1 occurring in the crown part of the central form 20. Also, in the arch part of the central form 20, cracks C2 may occur on the ground side of the arch part of the lining concrete C due to displacement towards the ground.

Even if centering down is performed when the poured lining concrete C is still at a weak age and has not yet fully developed its strength, the weak-age lining concrete C will also be displaced due to the displacement of the center form 20 after pouring, increasing the likelihood of cracks C1 and C2 occurring due to this displacement.

Therefore, in the lining center 100, before the lining concrete C is poured, a prestress force is introduced to at least the crown portion of the center form 20, pulling the crown portion of the center form 20 toward the interior of the tunnel T, and a displacement equivalent to the maximum downward displacement δ1 is given to the crown portion in advance. By then pouring the lining concrete C, the displacement of the center form 20 after the lining concrete C is poured is suppressed, and cracks that may occur due to the displacement of the lining concrete C following the displacement of the center form 20 are suppressed or prevented.

As shown in FIG. 1, the lining center 100 is configured so that the crown portion of the center form 20 and the left and right side wall portions are connected by PC steel materials 30 (an example of a means for introducing prestress force) such as PC steel bars or PC steel wires.

As shown in Figure 2, a prestress force P1 is introduced into the PC steel 30 to tension both the crown and side wall of the central form 20, and a displacement of approximately the expected downward displacement δ1 is applied to the crown of the central form 20 in advance. In other words, the magnitude of the prestress force P1 is set to a value that imparts to the crown a pre-casting displacement amount equivalent to the downward displacement δ1 of the crown when the lining concrete C is poured.

In addition, by introducing this prestress force P1, the arch portion adjacent to the side wall of the center form 20 is pulled toward the interior of the tunnel T by a load Q1, and this tensile load Q1 makes it possible to suppress excessive displacement δ2 toward the ground side shown in Figure 1.

Although not shown here, in addition to PC steel, a hydraulic jack (one example of a jack) or the like may be used as a means for introducing prestress force. When a hydraulic jack is used, a hydraulic jack that pulls the central form 20 toward the interior of the tunnel T is mounted on the gantry 10 at the crown of the central form 20, and a separate hydraulic jack is attached to the side of the leg 11 of the gantry 10. By pulling the side wall of the central form 20 with the separate hydraulic jack as in FIG. 2, it becomes possible to introduce prestress force P1 into the central form 20 in the same way as PC steel.

For example, in order to reduce deformation of the center form due to the weight of the lining concrete C, one method is to increase the cross-sectional size of the steel material used in the center to increase the rigidity of the center itself, but such an increase in the rigidity of the center increases the manufacturing cost of the center. In contrast, the lining center 100 uses PC steel material 30 to introduce prestress force into the desired location of the center form 20, thereby suppressing the displacement of the center form 20 due to the weight of the lining concrete C, and therefore can suppress cracks that may occur in the lining concrete C without increasing the manufacturing cost of the center. In particular, even if center down is performed at a stage when the lining concrete C is at a weak material age and does not have sufficient strength development, downward displacement due to the weight of the lining concrete C does not occur or is unlikely to occur, so cracks caused by this downward displacement can be suppressed, and it is possible to shorten the construction period of the tunnel while suppressing cracks that may occur in the lining concrete C.

Here, an example of a method for pouring lining concrete according to an embodiment will be outlined. This pouring method is a method for pouring lining concrete C into a pouring space S using a lining center 100 shown in Figures 1 and 2.

Before pouring the lining concrete C, a prestress force P1 is introduced into at least the crown portion of the central form 20, pulling the crown portion toward the interior of the tunnel T, and imparting a pre-pouring displacement to the crown portion that corresponds to the downward displacement δ1 of the crown portion when the lining concrete C is poured (Step A).

Next, lining concrete C is poured into the pouring space S between the ground G and the center form 20 (step B).

In this step B, it is preferable to adjust the prestress force so that the load is gradually released from the time the lining concrete is poured until the pouring is completed, thereby gradually changing the amount of displacement of the center form 20 during the strength development process of the lining concrete C and keeping the amount of displacement of the lining concrete C, which may change during the strength development process, constant.

[Lining center according to the second embodiment]
Next, an example of a lining center according to the second embodiment will be described with reference to Fig. 3. Here, Fig. 3 is a front view of the lining center according to the second embodiment, showing a state in which a prestress force is introduced into the prestress force introduction means.

The lining center 100A is provided with PC steel members 31, 32 on both the crown and arch portions of the center form 20, and is configured so that the PC steel members 31, 32 react to the prestress forces P2, P3 on the gantry 10. Although not shown in the figure, an example of the PC steel members 31, 32 is attached to the gantry 10 by fixing a truss structure extending in the longitudinal direction of the lining center 100A to the gantry 10 and using the PC steel members 31, 32 as the vertical members of this truss structure.

Furthermore, a counterweight 40 with a weight W is attached to the gantry 10 as a measure against the gantry 10 floating up due to the buoyancy F caused by the reaction force of the upward prestress force P2.

In this way, by taking the reaction forces of prestress forces P2 and P3 against the heavy gantry 10, it becomes possible to easily and stably take the reaction forces of prestress forces P2 and P3. On the other hand, the upward prestress force P2 is large, and as a measure against the gantry 10 floating up due to the prestress force P2, a counterweight 40 is attached to the gantry 10, which can effectively prevent the gantry 10 from floating up due to the upward prestress force P2.

[Centre for lining according to the third embodiment]
Next, an example of the lining center according to the second embodiment will be described with reference to Fig. 4. Here, Fig. 4 is a front view of the lining center according to the third embodiment, showing a state in which the prestress force is introduced into the prestress force introduction means.

The lining center 100B differs from the lining center 100A in that, instead of attaching a counterweight 40 to the gantry 10, the legs 13 of the gantry 10 grip the rail R along which the gantry 10 moves via a gripping member 50.

The legs 13 of the gantry 10 grip the rail R via the gripping members 50, which also effectively prevents the gantry 10 from floating up due to the prestress force P2.

[Lining center according to the fourth embodiment]
Next, an example of a lining center according to the third embodiment will be described with reference to Fig. 5. Here, Fig. 5 is a front view of the lining center according to the third embodiment, showing a state in which a prestress force is introduced into the prestress force introduction means.

The lining center 100C is configured such that the crown and arch parts of the center form 20 are connected by PC steel 33, and the arch part and the gantry 10 are connected by separate PC steel 34, so that the reaction force of the prestress force P5 introduced into the PC steel 34 is absorbed by the gantry 10.

The magnitude of the prestress force P4 is such that it imparts to the crown a pre-pouring displacement amount equivalent to the downward displacement δ1 of the crown when the lining concrete C is poured. In addition, the prestress forces P4 and P5 act directly on the arch portion, and the arch portion of the center form 20 is pulled toward the interior of the tunnel T by the load Q1, making it possible to suppress the excessive displacement δ2 toward the natural ground as shown in Figure 1.

In the lining center 100C, a counterweight 40 with a weight W is attached to the gantry 10 as a measure to prevent the gantry 10 from floating up due to buoyancy F caused by the reaction force of the upward prestress force P5. Here, instead of the counterweight 40, a floating measure may be taken in which the legs 13 of the gantry 10 grip the rail R via a gripping member 50 shown in FIG. 4.

The lining center 100C also makes it possible to easily and stably counter the prestress force P5 by countering the prestress force P5 against the heavy gantry 10.

[Lining center according to the fifth embodiment]
Next, an example of a lining center according to the fourth embodiment will be described with reference to Fig. 6. Here, Fig. 6 is a front view of the lining center according to the fourth embodiment, showing a state in which a prestress force is introduced into the prestress force introduction means.

The lining center 100D is configured such that PC steel members 35, 36, and 37 are provided in the crown, arch, and side wall portions of the center form 20, and each PC steel member 35, 36, and 37 is connected to the gantry 10, so that the reaction force of the prestress forces P6, P7, and P8 introduced into the PC steel member 33 is absorbed by the gantry 10.

The magnitude of the prestress force P6 is such that it imparts to the crown a pre-pouring displacement amount equivalent to the downward displacement δ1 of the crown when the lining concrete C is poured. In addition, the prestress force P7 acting directly on the arch portion and the prestress force P8 acting on the side wall portion pull the arch portion of the center form 20 toward the interior of the tunnel T with the load Q1, thereby making it possible to suppress the excessive displacement δ2 toward the natural ground side shown in Figure 1.

In the lining center 100D, a counterweight 40 with a weight W is attached to the gantry 10 as a measure to prevent the gantry 10 from floating up due to buoyancy F caused by the reaction force of the upward prestress forces P6 and P8. Here, instead of the counterweight 40, a floating measure may be taken in which the legs 13 of the gantry 10 grip the rail R via the gripping members 50 shown in FIG. 4.

The lining center 100D also makes it possible to easily and stably obtain the reaction forces of prestress forces P6, P7, and P8 by taking the reaction forces of prestress forces P6, P7, and P8 against the heavy gantry 10.

The present invention is not limited to the configuration shown here, and other embodiments may be possible in which other components are combined with the configurations described in the above embodiments. In this regard, changes can be made without departing from the spirit of the present invention, and can be determined appropriately according to the application form.

10: Gantry 11: Leg 12: Wheel 13: Leg 20: Center form 21: Form 25, 26, 27: Support member 30, 31, 32, 33, 34, 35, 36, 37: Prestress force introduction means (PC steel material)
40: Counterweight 50: Grip member 100, 100A, 100B, 100C, 100D: Lining center T: Tunnel G: Natural ground S: Pouring space B: Roadbed R: Rail C: Lining concrete C1, C2: Crack M: Bending moment

Claims (11)

A lining center applied when pouring lining concrete for a tunnel,
The lining center has a gantry and a center form supported by the gantry,
The central form includes a crown portion at the center, arch portions on the left and right sides of the crown portion, and side wall portions on the sides of the arch portions and below the left and right sides of the central form,
A center for lining, characterized in that a prestress force is introduced into at least the crown portion of the center form, pulling it toward the inner space of the tunnel. The lining center according to claim 1, characterized in that the crown portion and the side wall portion of the center form are connected by a prestress force introduction means, and both the crown portion and the side wall portion are tensioned. A prestress force introduction means is provided on both the crown portion and the arch portion of the central form, and the prestress force introduction means applies a reaction force of the prestress force to the gantry;
A lining centre as described in claim 1, characterized in that when the gantry rises due to the prestress force, a counterweight is attached to the gantry to prevent the rising, or the legs of the gantry grip the rails along which the gantry moves to prevent the rising. The crown portion and the arch portion of the center form are connected by a prestress force introduction means, and the arch portion and the gantry are connected by a separate prestress force introduction means so that the gantry receives a reaction force of the prestress force,
A lining centre as described in claim 1, characterized in that when the gantry rises due to the prestress force, a counterweight is attached to the gantry to prevent the rising, or the legs of the gantry grip the rails along which the gantry moves to prevent the rising. a prestress force introduction means is provided on each of the crown portion, the arch portion and the side wall portion of the central form, and the prestress force introduction means applies a reaction force of the prestress force to the gantry;
A lining centre as described in claim 1, characterized in that when the gantry rises due to the prestress force, a counterweight is attached to the gantry to prevent the rising, or the legs of the gantry grip the rails along which the gantry moves to prevent the rising. The lining center according to any one of claims 1 to 5, characterized in that the magnitude of the prestress force is such that a pre-casting displacement amount is imparted to the crown portion, which corresponds to the downward displacement amount of the crown portion when the lining concrete is cast. The lining center according to any one of claims 2 to 5 and claim 6 dependent on any one of claims 2 to 5, characterized in that the prestress force is gradually released from the time the lining concrete is poured until the pouring is completed by the prestress force introduction means. The lining center according to any one of claims 2 to 5, claims 6 and 7 depending on any one of claims 2 to 5, characterized in that the prestress force introduction means is a PC steel material. The lining centre according to any one of claims 2 to 5, claims 6 and 7 depending on any one of claims 2 to 5, characterized in that the prestress force introduction means is a jack. A method for pouring lining concrete for a tunnel using a lining center having a gantry and a center form supported by the gantry, the center form having a central crown portion, left and right arch portions of the crown portion, and side wall portions on the sides of the arch portions and below the left and right of the center form, comprising:
A process in which, before pouring the lining concrete, a prestress force is introduced into at least the crown portion of the center form to pull it toward the inside of the tunnel, thereby imparting a pre-casting displacement to the crown portion that corresponds to a downward displacement of the crown portion when the lining concrete is poured; and
A method for pouring lining concrete, comprising: a step B of pouring the lining concrete between the natural ground and the center form. The method for pouring lining concrete according to claim 10, characterized in that in step B, the prestress force is adjusted so that the load is gradually released from pouring the lining concrete until the end of pouring.

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