JP7712066B2 - How to build an underground structure - Google Patents

Description

The present invention relates to a method for constructing underground structures and a support structure used therefor.

One method for constructing underground structures in the ground beneath roads and other structures is the open cut method, in which the ground is excavated from the surface and an underground structure is constructed in the excavated portion. With the open cut method, retaining walls are installed on both sides of the planned excavation point in the ground, and the ground is excavated between the retaining walls. At this time, struts are installed between the retaining walls so that the lateral pressure of the ground acting on the retaining walls can be supported by the struts.

In this state, the base plate and side walls of the underground structure are constructed in the excavation section from the bottom up. The struts are removed as the underground structure is constructed, but if lateral pressure from the ground becomes a problem, replacement beams are installed between the already constructed side walls, and the lateral pressure from the ground acting on the side walls via retaining walls, etc. is supported by the replacement beams (see, for example, Patent Document 1).

Patent No. 6543176

When using replacement beams, temporary anchors are driven into the side wall of the underground structure, a bracket is attached, a wale is placed on the bracket, and the tip of the replacement beam is fixed to the wale. However, this type of work is time-consuming. In addition, forming holes in the side wall to drive anchors into can cause problems such as a loss of quality and aesthetics of the underground structure.

The present invention was made in consideration of the above problems, and its purpose is to provide a method for constructing an underground structure that allows for easy construction of an underground structure.

In order to achieve the above-mentioned object, the present invention includes a step (a) of constructing a pair of earth retaining walls on both sides of a planned excavation location of the ground, excavating the ground between the pair of earth retaining walls, and supporting the lateral pressure of the ground acting on the earth retaining walls by a strut spanning between the pair of earth retaining walls; a step (b) of removing the struts and constructing side walls on both sides of a main body of a skeleton of an underground structure, which is a tunnel , on the bottom slab of the main body of the skeleton in order from bottom to top in the height direction at positions along the pair of earth retaining walls in the excavation portion between the pair of earth retaining walls; and a step (c) of supporting a formwork for constructing the top slab with a formwork support having a configuration in which a horizontal member is connected midway in the height direction of a vertical member, the formwork being provided between the side walls on both sides up to the height of the top slab of the main body of the skeleton of the underground structure, which is the upper part of the side walls, and constructing the top slab with concrete using the formwork, and in the step (b), a horizontal temporary beam is provided on the horizontal member of the formwork support between the side walls on both sides. a contact member extending in the extension direction of the side walls is fixed to a tip end of one of the side walls of the temporary beam, and an expansion member provided midway in the longitudinal direction of the temporary beam is extended to bring the contact member into contact with a head of a constructed portion of one of the side walls, and an axial force is introduced into the temporary beam by taking a reaction force against the constructed portion of the other side wall or a constructed portion of a partition wall constructed between the side walls on both sides, the lateral pressure of the ground acting on the constructed portion of one of the side walls via the retaining wall is supported by the temporary beam , the top slab is constructed using the formwork shoring, and then the formwork shoring is moved on the bottom slab in the extension direction of the tunnel to a next construction section of the tunnel, and the lateral pressure of the ground acting on the side walls of the construction section is supported by the temporary beam .

In this invention, the lateral pressure of the ground acting on the side walls of the underground structure is supported by a temporary beam with an abutment member attached to its tip, which extends in the extension direction of the side walls of the underground structure. The temporary beam is placed on the formwork support and the abutment member is fixed to the tip of the temporary beam, so that the temporary beam and the abutment member can be installed without attaching a bracket or the like to the side walls, making it easier to build the underground structure and without compromising the quality or aesthetics.

It is desirable that the temporary beam be separable in the longitudinal direction.
This allows each divided part of the temporary beam to be stored in the formwork support, and the temporary beam can be easily dismantled and reassembled on the formwork support.

It is desirable that a plurality of the temporary beams are provided at intervals in the extension direction of the side wall, and the abutment member is provided for each of the temporary beams.
By using short abutment members for each temporary beam, excessive unbalanced load is not placed on the formwork support when the temporary beams are stored, preventing the formwork support from collapsing.

In the present invention, after the top plate is constructed using the formwork support, the formwork support is moved to the next construction section of the underground structure and the lateral pressure of the ground acting on the side walls of that construction section is supported by the temporary beams, so that the temporary beams, abutment members and formwork support can be moved together to the next construction section and reused.

The present invention provides a method for constructing an underground structure that allows for easy construction of an underground structure.

Diagram showing how the tunnel is constructed. Diagram showing how the tunnel is constructed. Diagram showing how the tunnel is constructed. A diagram showing the replacement beam 12 and the abutment member 13. Diagram showing how the tunnel is constructed. A diagram showing the replacement beam 12a and the abutment member 13a. Another example of a tunnel.

The following describes in detail a preferred embodiment of the present invention with reference to the drawings.

In this embodiment, an example will be described in which the ground beneath a road or the like is excavated, and a concrete tunnel is constructed as an underground structure. First, as shown in FIG. 1(a), a pair of retaining walls 2 are constructed on both sides of the planned excavation location of the ground 1, and intermediate piles 3 are driven into the ground 1 between the retaining walls 2. The retaining walls 2 are, for example, soil cement walls, but are not limited to this and various known wall structures can be used.

The ground 1 between the retaining walls 2 is shallowly excavated, and the upper wales 4 are installed inside both retaining walls 2. Steel materials such as H-shaped steel are used for the wales 4. The wales 4 are installed on brackets 21 fixed to the inside of the retaining walls 2, and are positioned along the extension direction of the retaining walls 2 (corresponding to the direction normal to the paper surface in Figure 1(a)).

Furthermore, a support girder 6 is placed between the tops of both retaining walls 2, and a lining plate 7 is installed on the support girder 6. The lining plate 7 is provided to ensure access over the excavation section 15.

In this embodiment, a reaction force receiving member 17 is fixed to the underside of the support girder 6, and the reaction force receiving member 17 and the rib 4 are connected via a jack 18. This allows the lateral pressure of the ground 1 acting on the retaining wall 2 to be transmitted to the support girder 6 via the reaction force receiving member 17, and the support girder 6 functions as an upper strut that supports the lateral pressure. For example, steel such as H-shaped steel is used for the support girder 6.

After that, as shown in FIG. 1(b), excavation of the ground 1 between the retaining walls 2 is continued, and the lower wale 4 is installed inside both retaining walls 2 in the same manner as described above. Then, struts 5 are installed between the lower wale 4. For the struts 5, steel materials such as H-shaped steel are used.

Next, the tunnel base slab 8 is constructed on the bottom of the excavation 15 between the two retaining walls 2, as shown in Figure 2(a). After the concrete of the base slab 8 has sufficiently hardened, the lower wale 4, strut 5, etc. are removed.

Then, as shown in FIG. 2(b), the tunnel side walls 9 are constructed on the bottom slab 8 at positions along the two retaining walls 2 on both sides of the bottom slab 8. In addition, the tunnel bulkheads 10 are constructed on the bottom slab 8 between the two side walls 9.

In this embodiment, to construct the top slab of the tunnel, which is the upper part of these walls, formwork supports 11 are assembled on the bottom slab 8 of the excavation section 15 as shown in FIG. 3(a). The formwork supports 11 are for supporting the formwork (not shown) when constructing the top slab, and are installed separately on both sides between each side wall 9 and the bulkhead 10, avoiding the position of the intermediate piles 3.

In addition, replacement beams 12 (temporary beams) are assembled in the tunnel width direction (corresponding to the left and right direction in Figure 3(a)) between each side wall 9 and the partition wall 10 so that they are positioned across the formwork supports 11, 11 on both sides of the intermediate pile 3.

The replacement beam 12 is made of steel material such as H-shaped steel, and can be divided in the longitudinal direction at the dividing section 121. The replacement beam 12 is constructed by connecting each part divided at the dividing section 121, and a jack 122 is provided midway along the longitudinal direction of the replacement beam 12. The jack 122 is an expandable member that expands and contracts in the longitudinal direction of the replacement beam 12. The replacement beam 12 is transported into the formwork support 11 in a state divided at the dividing section 121, and assembled on the formwork support 11.

In this embodiment, as shown in FIG. 3(b), abutment members 13 that abut against the side walls 9 and the partition walls 10 are fixed to both ends of the replacement beam 12.

When the concrete in the side walls 9 and bulkheads 10 has sufficiently hardened, the jacks 122 are extended, and the abutment members 13 at both ends are brought into contact with the side walls 9 and bulkheads 10, respectively, to introduce axial force into the replacement beams 12.

Figure 4 is a diagram showing a horizontal cross section along line A-A in Figure 3(b). As shown in Figure 4, the abutment member 13 is a short member extending in the extension direction of the side wall 9 (corresponding to the up-down direction in Figure 4), and is made of steel such as an H-shaped steel. A plurality of replacement beams 12 are provided at intervals in the extension direction of the side wall 9, and the center of the abutment member 13 is fixed to the tip of each replacement beam 12.

This forms a support structure in which the I-shaped replacement beam 12 and the abutment member 13 are placed on the formwork support 11. The lateral pressure of the ground 1 acts on the side wall 9 via the retaining wall 2, and the replacement beam 12 functions as a strut that supports this lateral pressure. The replacement beam 12 is placed on the formwork support 11, and the weight of the replacement beam 12 is supported by the formwork support 11.

Then, the lining plate 7, the support beam 6, the upper wale 4, the jacks 18, etc. are removed, and the top slab 14 of the tunnel is constructed using the formwork support 11 as shown in Figure 5 (a) while the lateral pressure of the ground 1 is supported by the replacement beam 12.

After the concrete of the top slab 14 has sufficiently hardened, the jack 122 is contracted to release the axial force of the replacement beam 12. The replacement beam 12 is then divided at the dividing section 121 and placed on the formwork support 11, which is then moved to the next construction section (see symbol B in Figure 4) where construction of the bottom slab 8 and side walls 9 has been completed. Then, as shown in Figure 5 (b), the ground 1 on the top slab 14 is backfilled.

The tunnel is constructed by dividing it into multiple construction sections, and in the next construction section, each process described in Figures 2 to 5 is carried out with a time lag. Therefore, by moving the formwork support 11 on the base slab 8, the installation of the formwork support 11 in the next construction section is completed, and the replacement beam 12 and the abutment member 13 can be reused for construction in the next construction section, and the lateral pressure of the ground 1 acting on the side wall 9 of that construction section can be supported by the replacement beam 12.

In this way, in this embodiment, the lateral pressure of the ground 1 acting on the side wall 9 is supported by the replacement beam 12, which has an abutment member 13 attached to its tip, extending in the extension direction of the tunnel side wall 9. The replacement beam 12 is placed on the formwork support 11, and the abutment member 13 is fixed to the tip of the replacement beam 12, so that the replacement beam 12 and the abutment member 13 can be installed without attaching a bracket or the like to the side wall 9, making it easier to construct the tunnel and without compromising the quality or aesthetics.

In addition, in this embodiment, since the replacement beam 12 can be divided at the dividing section 121, each part of the divided replacement beam 12 can be stored in the formwork support 11, and the replacement beam 12 can be easily disassembled and assembled on the formwork support 11.

After the replacement beam 12 is used, the formwork support 11 can be moved to the next construction section, and the replacement beam 12, abutment member 13, and formwork support 11 can be moved together to the next construction section and reused. By dividing the replacement beam 12 on the formwork support 11 in advance, the replacement beam 12 will not interfere with the intermediate pile 3 when the formwork support 11 is moved.

In addition, in this embodiment, the abutment members 13 are short and provided for each replacement beam 12. If the abutment members 13 were long and the tip of each replacement beam 12 was connected to a single abutment member 13, a large unbalanced load would be generated on the abutment member 13 side of the formwork supports 11, 11 on both sides of the intermediate pile 3 when the replacement beam 12 was stored, and there is a risk that the formwork supports 11 would tip over. However, in this embodiment, by making the abutment members 13 short, it is possible to prevent such a large unbalanced load from occurring when the replacement beam 12 is stored.

However, the present invention is not limited to the above embodiment. For example, in the above embodiment, the support girder 6 functions as an upper strut, but this is not essential, and an upper strut may be installed separately below the support girder 6.

Also, as shown in FIG. 6 in a horizontal cross section similar to that of FIG. 4, the intermediate piles 3 may be omitted, in which case there is no need to divide and arrange the formwork support 11 between each side wall 9 and the partition wall 10 to avoid the position of the intermediate piles 3. Also, the abutment members 13a may be long, and multiple replacement beams 12a may be connected to one abutment member 13a. The replacement beams 12a do not have the above-mentioned division section 121, and after the replacement beams 12a are used, the jacks 122 are contracted to move the formwork support 11 to the next construction section B, and the integrated replacement beams 12a and abutment members 13a move together with the formwork support 11.

In addition, the cross section of the tunnel is not limited to that shown in FIG. 5(a) etc. For example, as shown in FIG. 7, it may have no bulkhead 10, or it may have two or more bulkheads 10. The configuration of the support is also not particularly limited, as long as the abutment member at the tip of the replacement beam abuts against the side wall 9 of the tunnel on which the lateral pressure of the ground 1 acts, and the lateral pressure of the ground 1 acting on the side wall 9 is supported by the replacement beam. For example, in the example of FIG. 7, the abutment members 13 at both ends of the replacement beam 12 abut against each of the side walls 9 on both sides of the tunnel on which the lateral pressure acts.

Furthermore, the side wall 9 is not limited to being in contact with the retaining wall 2 as shown in FIG. 5(a) etc. For example, as shown in Patent Document 1, the side wall 9 may be provided at a distance from the retaining wall 2, and concrete or the like may be provided between the retaining wall 2 and the side wall 9 to transmit the lateral pressure of the ground 1 to the side wall 9.

Furthermore, the underground structures constructed using the method of this embodiment are not limited to tunnels, and the same method can be applied when constructing other underground structures.

The above describes preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to these examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas disclosed in this application, and it is understood that these also naturally fall within the technical scope of the present invention.

1: Ground 2: Retaining wall 3: Intermediate pile 4: Wale 5: Beam 6: Support girder 7: Covering plate 8: Bottom slab 9: Side wall 10: Partition wall 11: Formwork support 12, 12a: Relay beam 13, 13a: Abutment member 14: Top slab 15: Excavation section 17: Reaction receiving member 18, 122: Jack 21: Bracket 121: Division section

Claims (3)

(a) constructing a pair of retaining walls on both sides of a planned excavation location of the ground, excavating the ground between the pair of retaining walls, and supporting the lateral pressure of the ground acting on the retaining walls with a strut bridge spanning the pair of retaining walls;
(b) removing the struts and constructing side walls on both sides of the main body of the underground structure, which is a tunnel , in the excavation between the pair of earth retaining walls, in a height direction from bottom to top on the bottom slab of the main body of the underground structure, in a position along the pair of earth retaining walls;
A step (c) of supporting the formwork for constructing the top plate with a formwork support having a configuration in which a horizontal member is connected to the middle of the vertical member in the height direction, the formwork being provided between the side walls on both sides up to the height of the top plate of the main body of the underground structure, which is the upper part of the side walls, and constructing the top plate with concrete using the formwork;
having
In the step (b),
Between the side walls on both sides, a horizontal temporary beam is placed on the horizontal member of the formwork support in a direction connecting the side walls on both sides in a vertical plane, and the temporary beam is supported in the vertical direction by the formwork support;
abutment members extending in the extension direction of the side walls are fixed to the tip of one of the side walls of the temporary beam, and an expandable member provided midway in the longitudinal direction of the temporary beam is extended to bring the abutment members into contact with the head of the constructed portion of one of the side walls, and an axial force is introduced into the temporary beam by taking a reaction force from the constructed portion of the other side wall or the constructed portion of the partition wall constructed between the side walls on both sides, and the lateral pressure of the ground acting on the constructed portion of one of the side walls via the retaining wall is supported by the temporary beam ;
A method for constructing an underground structure, characterized in that after constructing the top slab using the formwork support, the formwork support is moved on the bottom slab in the extension direction of the tunnel to the next construction section of the tunnel, and the lateral pressure of the ground acting on the side walls of that construction section is supported by the temporary beams . The method for constructing an underground structure according to claim 1, characterized in that the temporary beam can be divided in the longitudinal direction. The temporary beams are provided at intervals in the extension direction of the side wall,
3. The method for constructing an underground structure according to claim 2, wherein the abutment member is provided for each of the temporary beams.