JP2023140927A - Construction method of underground structure and underground structure - Google Patents

Abstract

To implement a reinforcing bar erection process that improves workability, safety, and quality using simple equipment.SOLUTION: A construction method of an underground structure is provided, and comprises a first excavation step of excavating the ground and forming a shaft, an earth retaining member installation step of installing an earth retaining member along a wall surface of the shaft, an initial reinforcing bar installing step of suspending and lowering the reinforcing bar into the shaft while fixing the horizontal position using a fixing jig attached to the earth retaining member, and a final excavation step in which the ground is further excavated and the shaft is excavated in the vertical direction, a final reinforcement step of suspending and lowering the reinforcing bar into the shaft excavated in the final excavation step while fixing the horizontal position using the fixing jig, and a concrete placing step of placing concrete inside the shaft including the reinforcing bars.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for constructing an underground structure and an underground structure.

Generally speaking, deep foundations are constructed by repeating the procedure of sequentially connecting the left and right and top and bottom edges of liner plates while excavating the ground until a specified depth is reached, constructing an earth retaining wall inside the shaft, and installing reinforcing bars inside the earth retaining wall. It is constructed by erecting the concrete and pouring concrete. Generally, reinforcing bars installed inside an earth retaining wall include main reinforcing bars and hoop bars, and various techniques for installing these reinforcing bars have been proposed.

For example, Patent Document 1 discloses that inside a cylindrical pile hole, trestle columns with trestles provided at predetermined intervals are installed vertically along the wall surface to temporarily hold hoop bars, and a suspended scaffold that can be moved up and down. A technique is described in which hoop reinforcement is arranged and tied using floating scaffolding, concrete is poured using floating scaffolding, and the reinforcing bars are connected using a mechanical joint method to form vertical main reinforcement.

In addition, Patent Document 2 discloses that a scaffold for assembling reinforcing bars is formed in an excavated shaft, and hoop reinforcements are divided into multiple stages and temporarily assembled in a ring shape using an assembly device on the ground around the shaft. A technique is described in which hoop reinforcements in multiple stages are sequentially carried into a shaft, then main reinforcements are inserted into the shaft, and the main reinforcements and hoop reinforcements are connected using scaffolding.

Furthermore, in Patent Document 3, a tower-shaped temporary pedestal is constructed above the ground at the entrance of a deep foundation shaft, a plurality of chain foil winches capable of synchronous operation are arranged to suspend and support a support ring, and the support ring is reinforced with reinforcing steel. Attach the vertical bars that make up the cage one by one, weld the tie bars around the vertical bars, and use a chain foil winch to lift the parts that have secured the rigidity of the cage into the deep foundation shaft one by one along with the support ring. The technique for lowering it is described.

Japanese Patent Application Publication No. 2002-038475 Japanese Patent Application Publication No. 2003-313860 Japanese Patent Application Publication No. 09-177070

However, there are several problems with the conventional reinforcing steel reinforcement technology as described above. First, the method of assembling reinforcing bars in a shaft as described in Patent Document 1 has high construction accuracy because it is possible to check the concrete cover thickness on the outside of the reinforcing bars while assembling, but the workability is poor because scaffolding is required for assembly. It is not very safe as it is low and requires a lot of work inside the shaft. As described in Patent Document 2, the method of assembling to some extent above ground and then joining in a shaft improves workability and safety, but requires a large hanging machine. In addition, work inside shafts still exists, although it is decreasing. The method of continuously feeding reinforcing bars while assembling them at the shaft entrance, as described in Patent Document 3, further improves workability and safety, but requires large-scale equipment and is difficult to install from outside the shaft. It is difficult to confirm the concrete cover thickness because it involves assembly work.

Therefore, the present invention provides a method for constructing an underground structure and an underground structure, which can perform a reinforcing bar erecting process with improved workability, safety, and quality using simple equipment. The purpose is to

[1] An initial excavation process in which a shaft is formed by excavating the ground, an earth retention member installation process in which an earth retention member is installed along the wall of the shaft, and a horizontal An initial reinforcing reinsertion step in which reinforcing bars are suspended inside the shaft while fixing the position, a final excavation step in which the ground is further excavated and the shaft is dug in the vertical direction, and the fixing jig is used. a final reinforcing step of lowering the reinforcing bars into the shaft dug in the last excavation step while fixing the horizontal position; and pouring concrete inside the shaft containing the reinforcing bars. A method for constructing an underground structure, including a concrete placement process.
[2] Between the first excavation process and the last excavation process, there is at least one intermediate excavation process in which the ground is excavated and the shaft is dug in the vertical direction, and the shaft is excavated horizontally using the fixing jig. The method for constructing an underground structure according to [1], further comprising an intermediate reinforcing bar installation step of suspending the reinforcing bars into the shaft dug in the intermediate excavation step while fixing the position.
[3] The method for constructing an underground structure according to [1] or [2], wherein the earth retaining member has a corrugated cross section in the height direction.
[4] According to any one of [1] to [3], further comprising a grouting step of applying grout between the wall surface of the shaft and the earth retaining member by spraying or filling, or both. How to construct underground structures.
[5] The reinforcing bars include at least a first main reinforcing bar and a second main reinforcing bar arranged in the vertical direction, each of which is constructed by connecting a plurality of reinforcing bars in the longitudinal direction, and When the tips of the first main reinforcing bar and the second main reinforcing bar reach the bottom surface of the excavation of the shaft in the loading process, the connection position of the first main reinforcing bar and the connection of the second main reinforcing bar. The method for constructing an underground structure according to any one of [1] to [4], wherein the underground structure is located at a different height from the above.
[6] The method includes a step of connecting a new reinforcing bar to the upper end of the already erected reinforcing steel among the plurality of reinforcing bars, and then suspending the already erected reinforcing bar and the new reinforcing bar together. 5], the method for constructing an underground structure.
[7] The reinforcing bars include main reinforcing bars arranged in the vertical direction, and after the first reinforcing step, the protruding parts of the main reinforcing bars are locked to the fixing jig to increase the height of the main reinforcing bars. The method for constructing an underground structure according to any one of [1] to [6], further comprising a fixing step of fixing the position of the underground structure.
[8] An earth retaining member installed along the wall of a shaft formed by excavating the ground, a fixing jig attached to the earth retaining member, and reinforcing bars arranged to engage with the fixing jig. and concrete placed inside the shaft including the reinforcing steel.
[9] The underground structure according to [8], wherein the reinforcing bars include main reinforcing bars extending in the vertical direction, and the fixing jig has a structure capable of locking a protrusion of the main reinforcing bars.
[10] The underground structure according to [9], wherein the fixing jig has a notch through which the main reinforcing bar can be inserted and removed.
[11] The underground structure according to [9], wherein the fixing jig has a curved portion that approaches and separates from the main reinforcing bars by rotating in a horizontal plane.

According to the above configuration, the reinforcing bar installation process is performed by sequentially lowering the reinforcing bars in parallel with the process of excavating the shaft in stages. This eliminates the need for scaffolding to erect reinforcing bars inside the shaft, improving workability and safety. Furthermore, since the horizontal position of the reinforcing bars is fixed by a fixture attached to the retaining member, the concrete cover thickness outside the reinforcing bars can be reliably set without having to work inside the shaft. Since the reinforcing bars need only be lowered in stages, it is possible to downsize the cranes and other machines used for lifting and lowering. As described above, according to the present invention, it is possible to perform a reinforcing bar erection process with improved workability, safety, and quality using simple equipment.

It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure showing the process of the construction method of the deep foundation which is an underground structure concerning one embodiment of the present invention. It is a figure which shows the modification of the construction method of the underground structure based on one Embodiment of this invention. It is a figure which shows the modification of the construction method of the underground structure based on one Embodiment of this invention. It is a figure which shows the modification of the construction method of the underground structure based on one Embodiment of this invention. It is a figure showing an example of the method of fixing the height position of reinforcing bars in one embodiment of the present invention. 14 is a diagram showing a first example of a fixing jig that can be used in the example shown in FIG. 13. FIG. 14 is a diagram showing a second example of a fixing jig that can be used in the example shown in FIG. 13. FIG. 14 is a diagram showing a third example of a fixing jig that can be used in the example shown in FIG. 13. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that, in this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals and redundant explanation will be omitted.

(Construction method of underground structure)
Below, with reference to FIGS. 1 to 9, a method for constructing a deep foundation, which is an underground structure according to an embodiment of the present invention, will be described. First, Figure 1 shows the first stage of the excavation process (initial excavation process) in which the ground is excavated to form the shaft 1, the process of installing the liner plate 2, which is an earth retaining member, along the wall of the shaft 1, and the shaft 1 shows a process of installing main reinforcing bars 4A inside the shaft 1 (first reinforcing bar installation process) after a process of installing grout 3 between the wall surface of FIG. 1 and liner plate 2. The main reinforcing bars 4A are reinforcing bars arranged in the vertical direction and arranged along the inner circumference of the shaft 1. In this erection process, the main reinforcing bars 4A are suspended into the inside of the shaft 1 from the shaft entrance 1A side while fixing the horizontal position of the main reinforcing bars 4A using a fixing jig 5 attached to the liner plate 2. . Although omitted to simplify the illustration, the main reinforcing bar 4A located at the back of the figure is also fixed in horizontal position using a fixing jig attached to the liner plate 2 at the back. .

Here, in this embodiment, the main reinforcing bars 4A (first main reinforcing bars) whose tips reach the excavated bottom surface 1B of the shaft 1 at the time shown in FIG. Main reinforcing bars 42A (second main reinforcing bars) whose height position is fixed without reaching the bottom surface 1B. In addition, there are advantages of making the heights of the main reinforcing bars 42A different from each other during the erection process, and a fixing method for fixing the height position of the main reinforcing bars 42A with the tips not reaching the excavation bottom surface 1B. An example of the structure of the tool 5 will be described later.

Next, as shown in Figure 2, the second stage of the excavation process (intermediate excavation process) in which the ground is excavated and the shaft 1 is dug in the vertical direction is performed, and as shown in Figure 3, the shaft 1 that has been dug is Shot grout 31 is applied to the wall surface, liner plate 2 is installed along the wall surface of shaft 1 that has been dug as shown in FIG. 4, and as shown in FIG. Filling grout 32 is applied in between. The construction method of the liner plate 2 and grout 3 is also described in Japanese Patent Application Laid-Open No. 2020-105806, and by adopting such a construction method, it is possible to achieve economical design and improve workability. be. However, the liner plate and grout construction method according to the embodiment of the present invention is not limited to this example. For example, the sprayed grout 31 may be omitted and only the filling grout 32 may be applied, or the grout 3 itself may be omitted and concrete is poured into the hole provided in the liner plate 2 to form the wall surface of the shaft 1 and the liner plate. It may be filled between 2 and 2. The same applies to excavations other than the second stage, and an appropriate grout 3 application method can be selected depending on the ground conditions and the like. The grout 3 may be applied all at once after installing only the liner plate 2 in a plurality of stages of excavation, or the method of applying the grout 3 may be different for each stage of excavation.

Next, as shown in FIGS. 6 and 7, a process of erecting main reinforcing bars inside the dug shaft 1 (intermediate reinforcing bar erecting process) is performed. First, as shown in Fig. 6, new main reinforcing bars 4B (main reinforcing bars 41B, 42B) are connected to the upper part of main reinforcing bars 4A (main reinforcing bars 41A, 42A) using couplers 61, 62, and the connections are made as shown in Fig. 7. Lower the main reinforcing bars 4A and 4B. Also here, the tip of the main reinforcing bar 41A is made to reach the excavation bottom surface 1B of the shaft 1, whereas the height position of the main reinforcing bar 42A is fixed in a state where the tip does not reach the excavation bottom surface 1B. In this embodiment, couplers are used to connect the reinforcing bars used for the main steel, but in other embodiments, the reinforcing bars are connected using mechanical joints other than couplers, lap joints, gas pressure welding joints, or welding joints. The connection method is not particularly limited.

In the example shown in FIG. 6 above, a new main reinforcing bar 4B is connected to the main reinforcing bar 4A using couplers 61, 62, etc. to the upper end of the main reinforcing bar 4A that has already been erected, and then the main reinforcing bar 4A, 4B are suspended together. As another example, after suspending the main reinforcing bar 4A first, a new main reinforcing bar 4B may be connected to the main reinforcing bar 4A using couplers 61, 62 or the like. In this case, the couplers 61 and 62 may be attached to the upper end of the main reinforcing bar 4A on the ground in advance and then the main reinforcing bar 4A may be suspended, or the couplers 61 and 62 may be attached to the upper end of the main reinforcing bar 4A when connecting the main reinforcing bar 4B inside the shaft 1. 61 and 62 may be attached. As another example, a new main reinforcing bar 4B may be connected to the lower end of the main reinforcing bar 4A using couplers 61, 62 or the like. In this case, the main reinforcing bars 4A are not suspended, but the couplers 61 and 62 are attached to the lower ends of the main reinforcing bars 4A in advance, and the main reinforcing bars 4B are then lowered and the couplers 61 and 62 are attached to the lower ends of the main reinforcing bars 4A. You can also connect via

Thereafter, the intermediate excavation process and intermediate reinforcing bar installation process are repeated in the same manner, the ground is further excavated, and the shaft 1 is dug in the vertical direction, and the main reinforcing bars are erected inside the shaft 1 that has been dug. Figure 8 shows that shaft 1 reaches the predetermined design depth at the final stage of the excavation process (last excavation process), and the process of erecting main reinforcing bars inside shaft 1 that has been dug at the final stage (last stage). This shows the state in which the reinforcing bar erection process) has been carried out. Note that since FIGS. 8 and 9 are separate examples from those up to FIG. 7, the positions of the couplers of each reinforcing bar do not necessarily match. As shown in the figure, in the final reinforcement step, the tips of all the main reinforcement bars 41 and 42 are made to reach the excavated bottom surface 1B of the shaft 1.

As described above, in this embodiment, the main reinforcing bars 41 and 42 are constructed by connecting a plurality of reinforcing bars in the length direction with couplers 61 and 62, respectively. As shown in the examples of FIGS. 6 and 7, during excavation, main reinforcing bars 41A and 41B forming main reinforcing bars 41 (first main reinforcing bars) and main reinforcing bars 42 (second main reinforcing bars) While the height positions of the couplers 61 and 62 were aligned with the main reinforcing bars 42A and 42B, the height positions of the tips of the main reinforcing bars were different from each other, so the tips of the main reinforcing bars 41 and 42 were When the excavation bottom surface 1B is reached, the connection position of the main reinforcing bar 41 by the coupler 61 and the connection position of the main reinforcing bar 42 by the coupler 62 are located at different heights. This prevents all the main reinforcing bars from having the same height at the connection position, which would be a weak point in the structure, and improves the strength of the entire deep foundation including the main reinforcing bars. In the illustrated example, two types of main reinforcing bars whose connection positions are located at different heights are arranged, but three or more types of main reinforcing bars whose connection positions are located at different heights may be arranged.

Finally, as shown in FIG. 9, concrete 7 is placed inside the shaft 1 including the main reinforcing bars 41 and 42, and the deep foundation is completed. Note that the deep foundation in the illustrated example has a solid structure in which concrete 7 is poured throughout the interior of the shaft 1, but in other examples, it has a hollow structure in which concrete is poured with a space left inside. There may be. Hollow underground structures can be used not only as deep foundations but also as shafts (as structures), water collection wells, and the like. It is also possible to fill the space inside the hollow structure with earth and sand, such as leftover soil from earth excavation, and then use it as a deep foundation. Further, the number of times the steps of the excavation process are repeated is not particularly limited. For example, the excavation process may be up to a second stage, or more stages may be repeated.

In addition, in this embodiment, the liner plate 2 having a corrugated cross section in the height direction is arranged as an earth retaining member. Since the liner plate 2 has a corrugated cross section, a slip-preventing effect similar to that of deformed reinforcing bars can be obtained between the grout 3 applied on the outside and the concrete 7 placed on the inside. In addition, since the liner plates 2 are connected to each other in the height and width directions using bolts, etc., the concrete 7 is reinforced in the height direction (substitute for main reinforcing bars) and in the width direction (substituted for hoop bars). It also functions as Therefore, in this embodiment, the reinforcing bars of the deep foundation include only main reinforcing bars 4A, 4B, and 4C arranged in the vertical direction, and hoop reinforcing bars arranged in the circumferential direction of the shaft 1 as in the illustrated example. They do not include or have a reduced number of hoops than in normal designs. The design of such a deep foundation is also described in, for example, Japanese Patent Application Publication No. 2021-080628. In another embodiment of the present invention, it is also possible to arrange hoop reinforcements, and in that case, the main reinforcing bars to which the hoop reinforcements are connected are suspended with their tips aligned. In this case, reinforcement of the coupler portion of the main reinforcing bar will be considered separately. In addition to what is called a liner plate, various members having similar functions can be used as earth retaining members.

According to the method for constructing an underground structure according to the present embodiment as described above, in parallel with the step of excavating the shaft 1 in stages, the main reinforcing bars 4A, 4B, 4C are The process of installing reinforcing bars is carried out by lowering them one after another. This eliminates the need for scaffolding to erect reinforcing bars inside the shaft 1, improving workability and safety. In addition, since the horizontal positions of the main reinforcing bars 4A, 4B, and 4C are fixed by the fixing jig 5 attached to the liner plate 2, the outside positions of the main reinforcing bars 4A, 4B, and 4C do not need to be worked inside the shaft 1. Concrete cover thickness can be set reliably. Furthermore, if the hoop reinforcements are omitted, the main reinforcing bars 4A, 4B, and 4C can be lifted down one by one (one set), so a machine such as a large crane is not required for the lifting down. When arranging hoop bars, if the number of hoop bars is reduced compared to the conventional method, machines such as cranes for lifting and lowering can be downsized.

10 to 12 are diagrams showing modified examples of the method for constructing an underground structure according to an embodiment of the present invention. As a method for finally locating the connection position of the first main reinforcing bar and the connection position of the second main reinforcing bar at different heights, in the examples shown in Figures 1 to 7, the height of the connection position during excavation is We have explained a method in which the main reinforcing bars are aligned at different heights, and the tip of the main reinforcing bar with the deeper tip reaches the bottom of the excavation, but other methods can also be applied as explained below. It is possible. Note that FIGS. 10 to 12 below correspond to the steps in FIG. 1 in the above example.

For example, as in the example shown in FIG. 10, the height positions of the tips of the main reinforcing bars 41A and 42A are alternated, and the main reinforcing bars 41A whose tip is deeper does not reach the excavation bottom surface 1B. may be fixed. Alternatively, as in the example shown in FIG. 11, the height positions of the tips of the main reinforcing bars 41A and 42A may be aligned and both may be caused to reach the excavation bottom surface 1B at a point in time during the excavation. In this case, the connecting positions of the main reinforcing bars 41 and 42 will be at different heights at some point during the excavation. In addition, as in the example shown in FIG. 12, while aligning the height positions of the tips of the main reinforcing bars 41A and 42A, the height positions are adjusted so that the tips of none of the main reinforcing bars 41A and 42A reach the excavation bottom surface 1B. It may be fixed.

(Method of fixing reinforcing bars)
FIG. 13 is a diagram illustrating an example of a method for fixing the height position of reinforcing bars in an embodiment of the present invention. In addition, in order to simplify the drawing, illustrations are omitted except for a pair of reinforcing bars located within the radial cross section of the shaft 1 and a fixing jig for fixing these reinforcing bars. In the illustrated example, the first stage of the excavation process for the shaft 1 has been completed and the main reinforcing bars have been erected, similar to the example shown in FIG. 1 above. In this example, the main reinforcing bar 4A is shorter than the example of FIG. 1, and the main reinforcing bar 4B is already connected to the upper part via the coupler 6A. Further, although no other reinforcing bars are connected to the upper end of the main reinforcing bar 4B, the coupler 6B is attached in advance. Here, the couplers 6A and 6B are, for example, cylindrical members through which threaded holes (female threads) pass through which threaded portions (male threads) formed at the respective ends of the main reinforcing bars 4A and 4B are screwed together. The couplers 6A, 6B attached to the main reinforcing bars 4A, 4B form protrusions having a larger outer diameter than the main reinforcing bars 4A, 4B. In the illustrated example, by arranging the fixing jig 5 according to the length of the main reinforcing bars 4A, 4B, and locking the couplers 6A, 6B, which are protruding parts, to the fixing jig 5, the main reinforcing bars 4A, 4B are The height position of is fixed. Therefore, the height positions of the main reinforcing bars 4A, 4B can be maintained during the second stage of excavation of the shaft 1, and the main reinforcing bars 4A, 4B can be lowered after the excavation is finished.

FIG. 14 is a diagram showing a first example of a fixing jig that can be used in the example shown in FIG. 13. In the illustrated example, the fixing jig 5A has a plate shape as a whole with one side forked, and a mounting hole 51 for attaching to the liner plate 2 is formed at the base of the two forks, and the two forks face each other. A notch 52 with parallel sides is formed. As shown in FIG. 14(a), with the coupler 6A attached to the upper end of the main reinforcing bar 4A, insert the main reinforcing bar 4A into the notch 52 of the fixing jig 5A, and insert the coupler 6A on both sides of the notch 52. By placing the coupler 6A on the upper surface of the fixing jig 5A, the coupler 6A can be locked and the height position of the main reinforcing bar 4A can be fixed. In order to enable the insertion of the main reinforcing bars 4A (and the main reinforcing bars 4B) and the locking of the couplers 6A (and the couplers 6B), the inner dimensions of the notches 52 are set to the outer diameter of the main reinforcing bars 4A (and the main reinforcing bars 4B). and smaller than the outer diameter of coupler 6A (and coupler 6B).

As shown in FIG. 14(b), attach the main reinforcing bars 4B to the coupler 6A from above to connect the main reinforcing bars 4A and 4B, and then attach the coupler 6B to the upper end of the main reinforcing bars 4B. As shown, the horizontal positions of the main reinforcing bars 4A and 4B are shifted away from the fixing jig 5A, that is, toward the center of the shaft 1 (not shown). As a result, the coupler 6A is removed from the notch 52, and the coupler 6A is released from the fixing jig 5A. In this state, the main reinforcing bars 4A and 4B are suspended as shown in FIG. 14(d), and the main reinforcing bar 4B is then inserted into the notch 52. Thereby, the height positions of the main reinforcing bars 4A, 4B after being suspended can be fixed by locking the coupler 6B to the fixing jig 5A.

FIG. 15 is a diagram showing a second example of a fixture that can be used in the example shown in FIG. 13. In the illustrated example, the fixing jig 5B has a plate shape with an attachment part and a curved part, and the attachment part has an attachment hole 51 to the liner plate 2, and the inside of the curved part has a C-shaped inner edge. 53 is formed. As shown in FIG. 15(a), with the coupler 6A attached to the upper end of the main reinforcing bar 4A, the inner edge 53 of the fixing jig 5B is aligned with the main reinforcing bar 4A, and the coupler 6A is attached to the fixing jig outside the inner edge 53. By placing the coupler 6A on the upper surface of the fixture 5B, the coupler 6A can be locked and the height position of the main reinforcing bar 4A can be fixed. In order to stably lock the coupler 6A, the inner edge 53 has a partially planar radius of curvature larger than the radius of curvature of the outer peripheral surface of the main reinforcing bar 4A (and main reinforcing bar 4B), and ) is preferably smaller than the radius of curvature of the outer peripheral surface.

As shown in FIG. 15(b), attach the main reinforcing bars 4B to the coupler 6A from above to connect the main reinforcing bars 4A and 4B, and then attach the coupler 6B to the upper end of the main reinforcing bars 4B. As shown, the fixing jig 5B is rotated in a horizontal plane around the attachment hole 51 to separate it from the main reinforcing bar 4A. As a result, the coupler 6A separates from the inner edge 53 of the fixing jig 5B, and the locking of the coupler 6A by the fixing jig 5B is released. In this state, as shown in FIG. 15(d), the main reinforcing bars 4A and 4B are suspended, and the fixing jig 5B is again rotated in a horizontal plane around the attachment hole 51 to approach the main reinforcing bars 4B. The inner edge 53 is aligned with the main reinforcing bar 4B. Thereby, the height positions of the main reinforcing bars 4A, 4B after being suspended can be fixed by locking the coupler 6B to the fixing jig 5B. Such a fixing jig 5B can switch between fixing and releasing the height positions of the main reinforcing bars 4A and 4B without moving the horizontal positions, so for example, when hoop bars are placed in addition to the main reinforcing bars 4A and 4B, , it can also be used when suspending the main reinforcing bars 4A, 4B and hoop bars in a joined state.

FIG. 16 is a diagram showing a third example of a fixing jig that can be used in the example shown in FIG. 13. In the illustrated example, the fixing jig 5C is an annular member fixed to the shaft entrance 1A (not shown) of the shaft 1 using a flat bar or an angle. A plurality of notches 54 are formed on the inner periphery of the fixing jig 5C. The cutout 54 is a portion into which the main reinforcing bar can be inserted, similar to the cutout in the example described above with reference to FIG. 14. Cutouts 54 are formed on the inner circumference of the fixing jig 5C at intervals corresponding to the reinforcement intervals of the main reinforcing bars in the circumferential direction of the shaft 1. By inserting the main reinforcing bars into each notch 54 and locking the couplers, the height position of the main reinforcing bars can be fixed in the same way as in the examples shown in FIGS. 14 and 15 above. Furthermore, by removing the main reinforcing bar from the notch 54 and releasing the coupler, the main reinforcing bar can be further suspended. Such a fixing jig 5C can be used even when it is difficult to attach the fixing jig to the liner plate, for example.

In the example explained above, the height positions of the main reinforcing bars 4A, 4B are fixed by locking the couplers 6A, 6B to the fixing jigs 5A, 5B, 5C, but in other examples, the height positions of the main reinforcing bars 4A, 4B are fixed. A protrusion may be formed by press-contacting a sleeve-like member or welding another member to the intermediate portion of the protrusion, and the protrusion may be secured to the fixing jigs 5A, 5B, and 5C. The fixing jigs 5A and 5B may be attached to multiple stages of the liner plate 2 including the uppermost stage using the mounting holes 51 as in the example shown in FIG. 13, or they may be attached only to the uppermost stage. It's okay.

Note that the embodiments of the present invention are not limited to the example in which the height position is fixed by locking the protruding portion of the main reinforcing bar to the fixing jig as described above, and the height position of the main reinforcing bar is fixed. A separately provided means such as a clamp may be used. In addition, there are fixing jigs that can fix the horizontal position and height position of the main reinforcing bars, such as the above fixing jigs 5A, 5B, and 5C, and fixing jigs that only fix the horizontal position of the main reinforcing bars. May be used in combination. The fixing jig for fixing the height position of the main reinforcing bars may be arranged at only one location, for example, at the top of each main reinforcing bar. In the example explained above, multiple fixing jigs are arranged in the height direction, but if the horizontal position is fixed with at least one fixing jig, for example, the tip of the main reinforcing bar can be fixed at the end of excavation. By bringing the reinforcing bars into contact with the bottom of the excavation, two-point support is constructed, and the horizontal position of the main reinforcing bars can be stabilized.

Although preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. It is understood that these also fall within the technical scope of the present invention.

1... Vertical shaft, 1A... Well mouth, 1B... Excavation bottom surface, 2... Liner plate, 3... Grout, 31... Shot grout, 32... Filling grout, 4A, 4B, 4C, 41, 41A, 41B, 42, 42A, 42B ...Main reinforcement, 5, 5A, 5B, 5C...Fixing jig, 51...Mounting hole, 52, 54...Notch, 53...Inner edge, 61, 62, 6A, 6B...Coupler, 7...Concrete.

Claims (11)

an initial excavation process in which the ground is excavated to form a shaft;
an earth retaining member installation step of installing an earth retaining member along the wall surface of the shaft;
an initial reinforcement step of lowering the reinforcing bars into the shaft while fixing the horizontal position using a fixing jig attached to the earth retaining member;
a final excavation step in which the ground is further excavated and the shaft is dug in a vertical direction;
a final reinforcement step of lowering the reinforcing bars into the shaft dug in the last excavation step while fixing the horizontal position using the fixing jig;
and a concrete placing step of placing concrete inside the shaft containing the reinforcing bars. Between the first excavation process and the last excavation process, at least one intermediate excavation process in which the ground is excavated and the shaft is dug in a vertical direction;
The ground construction according to claim 1, further comprising: an intermediate reinforcing bar erecting step of suspending the reinforcing bars into the shaft dug in the intermediate excavation step while fixing the horizontal position using the fixing jig. How to build medium structures. The method for constructing an underground structure according to claim 1 or 2, wherein the earth retaining member has a wave-shaped cross section in the height direction. The underground method according to any one of claims 1 to 3, further comprising a grouting step of applying grout between the wall surface of the shaft and the earth retaining member by spraying, filling, or both. How to build structures. The reinforcing bars include at least first main reinforcing bars and second main reinforcing bars arranged in the vertical direction, each of which is configured by connecting a plurality of reinforcing bars in the longitudinal direction,
When the tips of the first main reinforcing bar and the second main reinforcing bar reach the bottom surface of the excavation of the shaft in the last reinforcement step, the connection position of the first main reinforcing bar and the second main reinforcing bar are determined. The method for constructing an underground structure according to any one of claims 1 to 4, wherein the connecting position of the main reinforcing bars is located at a different height. 6. The method according to claim 5, further comprising the step of connecting a new reinforcing bar to the upper end of the already erected reinforcing bar among the plurality of reinforcing bars, and then suspending the already erected reinforcing bar and the new reinforcing bar together. Method of constructing the underground structure described. The reinforcing bars include main reinforcing bars arranged in the vertical direction,
7. The method according to claim 1, further comprising a fixing step of fixing the height position of the main reinforcing bars by locking the protruding parts of the main reinforcing bars to the fixing jig after the first reinforcing bar erecting step. A method for constructing an underground structure according to any one of the items. An earth retaining member installed along the wall of a shaft formed by excavating the ground,
a fixing jig attached to the earth retaining member;
reinforcing bars arranged to engage with the fixing jig;
and concrete placed inside the shaft containing the reinforcing steel. The reinforcing bars include main reinforcing bars extending in the vertical direction,
The underground structure according to claim 8, wherein the fixing jig has a structure capable of locking the protrusion of the main reinforcing bar. The underground structure according to claim 9, wherein the fixing jig has a notch through which the main reinforcing bar can be inserted and removed. The underground structure according to claim 9, wherein the fixing jig has a curved portion that approaches and separates from the main reinforcing bars by rotating in a horizontal plane.

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