How to install invert blocks

Abstract

To provide an invert-block installation method capable of easily preventing plate swelling in a tunnel in a short construction period at low cost.SOLUTION: The invert-block includes a support member 11 that connects elements 10e of a connection opening 10ea for communicating with the internal spaces of both elements 10e and supports loads from above. The invert-block installation method includes the steps of: preparing multiple long elements 10e for forming an invert-block 10 with a box-shaped hollow structure constituted of an upper plate 10ts, a lower plate 10us, and side plates 10sf; arranging the elements 10e parallel to each other along the axial direction of a tunnel with the longitudinal direction of the elements oriented in the circumferential direction of the tunnel according to the order of forming the invert-block 10: forming the invert-block 10 by aligning the height of the installed element 10e and connecting the elements 10e with the same height; injecting grout G between the bottom of the formed invert-block 10 and the installation ground; and backfilling the invert-block 10 with subgrade material to form the subgrade after injecting the grout.SELECTED DRAWING: Figure 21

Description

Technical Field

[0001] The present invention relates to a construction technique for preventing ground heave in a tunnel.

Background Art

[0002] Depending on the stress state around the tunnel, due to the pressure pushing up from the lower bottom, ground heave locations may occur due to road surface uplift, deformation, etc., and the soundness of the tunnel structure may be reduced.

[0003] Therefore, in order to withstand the pressure pushing up from the lower bottom, a construction is carried out to install an invert that is in an inverted arch shape with respect to the tunnel on the bottom ground of the tunnel.

[0004] Regarding the technique of constructing an invert in a tunnel, for example, the one described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2020-041381) is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, the installation of an invert in a tunnel generally uses a construction method with cast-in-place concrete. However, for cast-in-place concrete, it takes time for the installation of formwork for placing the concrete, the curing of the concrete, etc., and the construction period becomes long. In particular, when applying this construction method to a tunnel on an expressway in service, the lane regulation period becomes long, so the impact becomes large.

[0007] Another construction method involves manufacturing precast inverts, transporting them into the tunnel, and installing them. However, this method is not only costly, but also difficult because the construction takes place inside the tunnel, limiting the size of the heavy machinery that can be used, and making it challenging to rotate the crane used to lift and install the inverts.

[0008] This invention was made in light of the above-mentioned technical background, and aims to provide a technology that enables tunnel bulging prevention construction to be carried out in a short period of time, at low cost, and easily. [Means for solving the problem]

[0009] To solve the above problems, the method for installing an invert block according to claim 1 of the present invention is a method for installing an invert block in the ground at the bottom of a tunnel by restricting traffic in one of two lanes and connecting a plurality of steel elements, wherein a support member is installed at a connecting opening where the elements are connected to each other, and a support member is installed to support an upward load, and a plurality of elongated elements are prepared to form an invert block with a box-shaped hollow structure consisting of an upper plate, a lower plate and a side plate, and the ground at the bottom of the tunnel is excavated, The method is characterized by comprising: a second step of aligning the longitudinal direction of the elements with the circumferential direction of the tunnel and installing the elements in parallel in the axial direction of the tunnel in the order of forming the invert block; a third step of aligning the heights of the installed elements; a fourth step of connecting the elements of the aligned heights to form the invert block; a fifth step of injecting backfill material between the bottom surface of the formed invert block and the installation ground; and a sixth step of backfilling the invert block with subgrade material after injecting the backfill material to form the subgrade.

[0010] The method for installing an invert block according to claim 2 of the present invention is characterized in that, in the invention described in claim 1, the second step, the third step, and the fourth step are integrated steps, and the invert block is formed by repeatedly installing the elements one by one, aligning their heights, and connecting them.

[0011] The method for installing an invert block according to claim 3 of the present invention is characterized in that, in the invention described in claim 1, the second step and the third step are integral steps, the work of installing the elements constituting the invert block one by one and leveling their heights is repeated, and in the fourth step, all the elements are connected together to form the invert block.

[0012] The method for installing an invert block according to claim 4 of the present invention is characterized in that, in the invention according to claim 1, in the second step, all the elements constituting the invert block are installed together; in the third step, the heights of all the elements constituting the invert block are aligned together; and in the fourth step, all the elements constituting the invert block are connected together to form the invert block.

[0013] The method for installing an invert block according to claim 5 of the present invention is characterized in that, prior to the injection of backfill material, an outflow prevention wall is erected on the side surface of the element on the tunnel axial end side of the invert block and on the side surface of the invert block on the tunnel side wall side to prevent the backfill material from flowing out, and the outflow prevention wall is removed after the injection of backfill material and before backfilling the invert block.

[0014] The method for installing invert blocks according to claim 6 of the present invention is characterized in that, in the invention described in any one of claims 1 to 4 above, the elements are installed in the same number as the number of invert blocks.

[0015] The method for installing invert blocks according to claim 7 of the present invention is characterized in that, in the invention according to any one of claims 1 to 4, a seventh step is to repeatedly perform the second to sixth steps over a predetermined period of time, and then laminate a base layer and an asphalt layer on the subgrade.

[0016] The method for installing invert blocks according to claim 8 of the present invention is characterized in that, in the invention according to claim 7, an eighth step of peeling off the roadbed layer and the asphalt layer is performed, and after performing the eighth step, the second to seventh steps are performed. [Effects of the Invention]

[0017] According to the method for installing invert blocks of the present invention, an invert block can be constructed by setting up multiple steel elements on site and connecting them to each other, and then backfilling the area. Therefore, by using the method for installing invert blocks of the present invention, it becomes possible to perform tunnel bulging prevention work in a short period of time, at low cost, and easily. [Brief explanation of the drawing]

[0018] [Figure 1] This is a plan view showing an invert block, which is one embodiment of the present invention, installed on the ground at the bottom of a tunnel by connecting two blocks along the circumferential direction of the tunnel through which vehicles pass. [Figure 2] This is a cross-sectional view of the invert block embedded in the ground at the bottom of the tunnel (Figure 1) and the lower half of the tunnel, taken from the circumferential direction of the tunnel. [Figure 3] This is a cross-sectional view of the end portion in the installation direction and the element other than both ends of the invert block, which is one embodiment of the present invention. [Figure 4]It is a cross-sectional view along the short side direction of the element at the rear end in the installation direction of one end of the two ends constituting the block for inversion according to an embodiment of the present invention. [Figure 5] It is an explanatory view showing the short-side side plates of adjacent elements. [Figure 6] (a) is an explanatory view showing the relationship between the short-side side plate and the closing plate before connecting adjacent elements, and (b) is an explanatory view showing the relationship between the short-side side plate and the closing plate after connecting adjacent elements. [Figure 7] It is a plan view showing the flow direction of the concrete placed in the block for inversion of FIG. 1. [Figure 8] It is the cross-sectional view of FIG. 7. [Figure 9] It is a drawing showing the boring machine loading process, which is a process for continuously installing the block for inversion of FIG. 1 along the axial direction of the tunnel. (a) is an explanatory view seen from the plane, and (b) is an explanatory view seen from the axial cross-section of the tunnel. [Figure 10] It is a drawing showing the initial excavation process following FIG. 9. (a) is an explanatory view seen from the plane, and (b) is an explanatory view seen from the axial cross-section of the tunnel. [Figure 11] It is a drawing showing the floor laying machine loading process following FIG. 10. (a) is an explanatory view seen from the plane, and (b) is an explanatory view seen from the axial cross-section of the tunnel. [Figure 12] It is a drawing showing the excavation and floor laying process following FIG. 11. (a) is an explanatory view seen from the plane, and (b) is an explanatory view seen from the axial cross-section of the tunnel. [Figure 13] It is a drawing showing the unloading and transport machine loading process following FIG. 12. (a) is an explanatory view seen from the plane, and (b) is an explanatory view seen from the axial cross-section of the tunnel. [Figure 14] It is a drawing showing the entry and reverse process of the member transport vehicle following FIG. 13. (a) is an explanatory view seen from the plane, and (b) is an explanatory view seen from the axial cross-section of the tunnel. [Figure 15] It is a drawing showing the member unloading process following FIG. 14. (a) is an explanatory view seen from the plane, and (b) is an explanatory view seen from the axial cross-section of the tunnel. [Figure 16] The following diagram shows the temporary placement process of the components, following Figure 15. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 17] The following diagrams show the component installation process, with (a) being an explanatory diagram viewed from above and (b) being an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 18] The following diagram shows the backfill injection process, as shown in Figure 17. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 19] The following diagram shows the backfilling machine delivery process, with (a) being an explanatory diagram viewed from above and (b) being an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 20] The following diagram shows the backfilling process, with (a) being an explanatory diagram viewed from above and (b) being an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 21] The following diagram shows the compaction process, with (a) being an explanatory diagram viewed from above and (b) being an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 22] The following diagrams show the process of removing heavy machinery and bringing in paving machinery, following Figure 21. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 23] The following diagram shows the temporary paving process, as shown in Figure 22. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 24] The following diagrams show the temporary pavement removal and excavation process, with (a) being an explanatory diagram viewed from above and (b) being an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 25] This diagram shows the temporary pavement removal process, which is one step in pouring concrete into the buried invert blocks. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross section of the tunnel. [Figure 26] The following diagram shows the concrete pouring commencement process, following Figure 25. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 27] The following diagram shows the concrete pouring process, following Figure 26. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel. [Figure 28] The following diagram shows the temporary repaving process, which follows Figure 27. (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel. [Modes for carrying out the invention]

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings used to illustrate the embodiments, the same reference numerals are generally used for identical components, and repeated descriptions of such components will be omitted.

[0020] Figure 1 is a plan view showing two invert blocks, one embodiment of the present invention, connected together along the circumferential direction of a tunnel through which vehicles pass, and installed in the ground at the bottom of the tunnel. Figure 2 is a cross-sectional view showing the invert blocks of Figure 1 embedded in the ground at the bottom of the tunnel and the lower half of the tunnel, viewed from the circumferential direction of the tunnel. Figure 3 is a cross-sectional view of the front end in the installation direction and the elements other than the front end in the installation direction among the ends of the invert block, one embodiment of the present invention, along the short direction. Figure 4 is a cross-sectional view of the element at the rear end in the installation direction among the ends of the invert block, one embodiment of the present invention, along the short direction.

[0021] As shown in Figures 1 and 2, the invert blocks 10 of this embodiment are installed and buried in the ground at the bottom of the tunnel T, with two blocks connected in the circumferential direction of the tunnel T to form an inverted arch shape. In this embodiment, the width of one invert block 10 corresponds to the width of one lane. Therefore, the invert blocks 10 of this embodiment are laid in the ground at the bottom of a tunnel T that has two lanes (one-way traffic with two lanes on each side or two-way traffic with one lane on each side).

[0022] In the actual installation process, the invert blocks 10 are installed across the entire width of one lane, and then the invert blocks 10 are installed across the entire width of the other lane, connecting them to the existing invert blocks 10. In some tunnels, three or more invert blocks may be connected in the circumferential direction of the tunnel T to form an inverted arch.

[0023] As shown in Figure 1, the invert block 10 has an elongated shape that extends in the circumferential direction of the tunnel T in which it is installed, and is composed of four steel elements 10e that are interconnected in the axial direction along their longitudinal side. These elongated elements 10e are installed over a long distance in the circumferential direction of the tunnel T. That is, elements 10e-1 and 10e-4 located at both ends, and two elements 10e-2 and 10e-3 located between these elements 10e-1 and 10e-4, are installed over a long distance in the circumferential direction of the tunnel T and are connected in parallel to each other in the axial direction (installation direction) of the tunnel T. Note that the number of elements 10e does not necessarily have to be four; two or more, i.e., any number of elements 10e is acceptable.

[0024] The invert block 10 comprises an upper plate 10ts, a lower plate 10us, and a side plate 10sf, each separated into elements 10e. In other words, the invert block 10, when these elements 10e are integrated, forms a box-shaped hollow structure consisting of an upper plate 10ts, a lower plate 10us, and a side plate 10sf. The side plate 10sf consists of a longitudinal side plate 10sf-1, which is a side plate 10sf oriented in the longitudinal direction (a side plate 10sf located in the axial direction of the tunnel), and a short-direction side plate 10sf-2, which is a side plate 10sf oriented in the short direction (a side plate 10sf located in the circumferential direction of the tunnel). The elements 10e-1 and 10e-4 at both ends are comprised of an upper plate 10ts, a lower plate 10us, a longitudinal side plate 10sf-1, and a short-direction side plate 10sf-2. Furthermore, elements 10e-2 and 10e-3 are equipped with an upper plate 10ts, a lower plate 10us, and a short-side plate 10sf-2. These upper plate 10ts, lower plate 10us, and side plate 10sf are welded to each other for each element 10e.

[0025] Figures 2 and 8 (described later) show the invert blocks 10 embedded in temporary pavement. Details leading up to the temporary pavement will be described later, but in this embodiment, the temporary pavement is formed by creating a subgrade RB on the invert blocks 10, and then forming a pavement layer L (a layer in which the lower subbase L1 (crushed stone (crusher run)), upper subbase L2 (graded crushed stone), base layer L3 (coarse-graded asphalt concrete), and surface layer L4 (dense-graded asphalt concrete) are sequentially stacked) on top of the subgrade RB.

[0026] Here, as shown in Figures 3 and 4, inside the connecting opening 10ea of ​​the element 10e, which is formed on the longitudinal side where the elements 10e are connected to each other, ribs 10eb are welded perpendicular to the upper and lower plates 10ts and 10us, facing each other and extending along the longitudinal direction. A support member 11 for supporting loads from above is installed on this rib 10eb. As shown in Figure 2, the support member 11 is truss-shaped, so that a compressive force is generated when a load is applied from above, but it is less susceptible to bending moments. In addition, the truss shape creates gaps between the support members 11, thereby connecting the internal spaces of each element 10e that constitute the hollow invert block 10.

[0027] Furthermore, the support member 11 does not need to be truss-shaped; it is sufficient if it is structured in a way that supports loads from above and creates a space where the insides of the elements 10e are interconnected (more specifically, a space large enough for concrete to be poured in a later process to flow from one element 10e to the other).

[0028] Furthermore, connecting plates 10ed and 10ef are provided at the points where the elements 10e are connected, so as to span both elements 10e. Specifically, a connecting plate 10ed, which has an elongated hole (through hole) (not shown) that is elongated in the axial direction (installation direction) of the tunnel formed on the lower surface of the upper plate 10ts of one element 10e, is attached to the upper plate 10ts so as to protrude from the upper plate 10ts and to the entire length of the longitudinal side of the upper plate 10ts. Also, a connecting plate 10ef, which has a sponge-type sealing material 10ee attached to its upper surface, is attached to the lower plate 10us of one element 10e so as to protrude from the lower plate 10us and to the entire length of the longitudinal side of the lower plate 10us. Therefore, the protruding portions of the connecting plates 10ed and 10ef overlap with the upper plate 10ts and lower plate 10us of the other element 10e, so that the connecting plates 10ed and 10ef are positioned so as to span both elements 10e. Furthermore, a connecting bolt 10eg is attached to the upper plate 10ts of the other element 10e so that it can be tightened from above, passing through the aforementioned elongated hole formed in the connecting plate 10ed and screwing into a nut 10ec.

[0029] Thus, the connecting bolt 10eg passes through an elongated hole formed in the connecting plate 10ed, which is elongated in the axial direction (installation direction) of the tunnel. This elongated hole acts as an adjustment allowance, allowing the connecting bolt 10eg to be screwed into the nut 10ec without being affected by the misalignment in the installation direction when connecting the elements 10e. In other words, since the fastening position of the connecting bolt 10eg and the nut 10ec with respect to the elongated hole can be adjusted, depending on the ground conditions in which the elements 10e are installed, when they can be installed in close contact, the connecting bolt 10eg and the nut 10ec can be screwed into the elongated hole at the position in the close contact state. When the elements 10e cannot be installed in close contact and are misaligned in the installation direction, the connecting bolt 10eg and the nut 10ec can be screwed into the elongated hole at the position in the misaligned state. However, if it is not necessary to consider the misalignment in the installation direction when connecting the elements 10e, the through hole formed in the connecting plate 10ed may be a round hole with a diameter through which the connecting bolt 10eg can pass, rather than an elongated hole.

[0030] When the elements 10e are installed in close contact with each other, only small gaps are formed between the upper plates 10ts, lower plates 10us, and short-side plates 10sf-2 of both elements 10e. However, when the elements 10e are installed offset from each other in the installation direction, gaps equal to the offset are formed between the upper plates 10ts, lower plates 10us, and short-side plates 10sf-2. These gaps (the small gap formed when the elements 10e are installed in close contact with each other, and the gap corresponding to the offset formed when the elements 10e are installed offset from each other in the installation direction) are closed by the connecting plate 10ed between the upper plates 10ts, by the connecting plate 10ef between the lower plates 10us, and by the closing plate 10eh (described later) between the short-side plates 10sf-2.

[0031] Furthermore, the sealing material 10ee is sealed when the elements 10e are connected to each other and are pressed down from above by the lower plate 10us of the other element 10e, causing it to be compressed (for example, compressed to less than 1 mm).

[0032] Therefore, by screwing the connecting bolt 10eg and nut 10ec together, the two adjacent elements 10e are connected to each other via the upper connecting plate 10ed, and the sealing material 10ee of the lower connecting plate 10ef is crushed and sealed, making it difficult for soil and sand to enter the hollow invert block 10 from the outside.

[0033] The sealing material 10ee may also be provided along its entire length on the upper surface of the connecting plate 10ed, which is provided on the upper plate 10ts.

[0034] Support bolts 15 are attached to the lower plate 10us of element 10e, protruding downwards. These support bolts 15 adjust the height of element 10e by inserting a base 16 between the lower end of the support bolt 15 and the ground when element 10e is installed on the ground, and are provided at both ends in the longitudinal direction of element 10e.

[0035] Furthermore, nuts 17 that engage with the support bolts 15 are fixed by welding to the holes through which each support bolt 15 passes in the lower plate 10us of element 10e.

[0036] Element 10e-1 (starting end element), located at the end of the invert block 10 and the first element installed when the invert block 10 is formed, is provided with a total of four support bolts 15, two at each of its longitudinal ends. The other elements 10e-2, 10e-3, and 10e-4 are provided with a total of two support bolts 15, one at each of their longitudinal ends. This is because element 10e-1 needs to be stabilized with four support bolts 15 because it is the first element to be installed, whereas elements 10e-2, 10e-3, and 10e-4 are connected sequentially to the existing elements 10e-1, 10e-2, and 10e-3, respectively, and can be stabilized with two support bolts 15. However, the number of support bolts 15 is not limited to the four or two mentioned above, and any number greater than or equal to that shown in this embodiment is acceptable. In the illustration, the support bolts 15 provided on elements 10e-2, 10e-3, and 10e-4 are shown at both ends in the longitudinal direction, on the side facing the element installation direction. However, they do not necessarily have to be in this position; for example, they could be on the opposite side from the element installation direction.

[0037] As shown in Figure 3, the support bolt 15 on the opposite side of the element installation direction of the first element 10e-1 (the support bolt 15 shown on the left side of element 10e-1 in Figure 3) is located at the back, making it difficult for a worker to reach it by reaching through the connection opening 10ea. Therefore, the support bolt 15 at this position is housed in a bolt hole H4 that penetrates the element 10e vertically, and a wrench hole (such as a hexagonal wrench hole) is formed in its head. Then, a long rod wrench (such as a hexagonal rod wrench) is inserted from the top of the bolt hole H4 to rotate the support bolt 15 and adjust the height of element 10e-1.

[0038] Furthermore, as also shown in Figure 3, the support bolt 15 located on the element installation side of element 10e-1 (the support bolt 15 shown to the right of element 10e-1 in Figure 3), and the support bolts 15 of elements 10e-2 and 10e-3 located between element 10e-1 and element 10e-4 (the element located at the end of the invert block 10 and the last element installed when the invert block 10 is formed: the terminal element) (the support bolts 15 shown for elements 10e-2 and 10e-3 in Figure 3) are located in a position that allows them to rotate from the connection opening 10ea, as they are within reach of an operator by reaching their hand through the connection opening 10ea.

[0039] Furthermore, as shown in Figure 4, the support bolt 15 of element 10e-4 is positioned to rotate from the gap between element 10e-4 and the ground, because when element 10e-4 is connected to the adjacent element 10e-3, it becomes impossible for a worker to reach through the connection opening 10ea. In this case, as shown in the figure, the support bolt 15 is screwed into the lower plate 10us from below upward so that the head 15a of the support bolt 15 (i.e., the part that rotates the support bolt) is between element 10e-4 and the ground.

[0040] Here, the structure of the side plate 10sf of the invert block 10 will be explained using Figures 5 and 6. Figure 5 is an explanatory diagram showing the short-direction side plate of adjacent elements, and Figure 6 is an explanatory diagram showing the relationship between the short-direction side plate and the closing plate of adjacent elements, where (a) shows the adjacent elements before connection and (b) shows the adjacent elements after connection.

[0041] The invert block 10 is equipped with separate side plates 10sf (longitudinal side plate 10sf-1, transverse side plate 10sf-2) for each element 10e. As mentioned above, a gap is formed between the transverse side plates 10sf-2 of adjacent elements 10e, corresponding to the fastening positions of the connecting bolts 10eg and nuts 10ec to the elongated holes formed in the connecting plate 10ed (see Figure 6(a)).

[0042] If this gap is left as is, soil and sand will enter the hollow invert block 10, or concrete will leak out through the gap when concrete is poured in a later step. Therefore, as shown in Figures 5 and 6(a), a closing plate 10eh is provided to close the gap formed between the two short-side plates 10sf-2 when the elements 10e (in this case, element 10e-1 and element 10e-2) are connected.

[0043] The closing plate 10eh is welded to the outer surface of the side end of the short-side plate 10sf-2 of one element 10e (element 10e-2 in the illustration), with a portion of it overlapping the short-side plate 10sf of the adjacent element (element 10e-1 in the illustration) in the tunnel axial direction. As a result, the aforementioned gap formed when two elements 10e (in this case, element 10e-1 and element 10e-2) are connected is closed by the closing plate 10eh. It is desirable that, once two elements 10e are connected, the gap between the other element 10e (in this case, element 10e-1) and the closing plate 10eh be welded or sealed with a pre-installed sealant.

[0044] Now, in Figure 1, multiple (two in this case) H-shaped steel piles 12 are erected. These piles 12 serve as both support posts for guardrails that separate the two lanes and main piles for sheet piles used during ground excavation (sheet piles used as retaining walls when excavating the ground for the installation of invert blocks 10). Therefore, the elements 10e that make up the invert blocks 10 have recesses formed to avoid interference with the piles 12.

[0045] Furthermore, as shown in Figure 1, elements 10e-1 and 10e-4 located at both ends of the invert block 10 in the installation direction (tunnel axis direction) have connecting holes 13 formed in the upper plate 10ts, with nuts fixed to the inside. These connecting holes 13 are for connecting adjacent invert blocks 10 via connecting plates (not shown). That is, the connecting plate is fixed to the invert block 10 by screwing a bolt through a through hole formed in the connecting plate into the nut in the connecting hole 13. Then, by bolting the same connecting plate to the adjacent invert block 10, the adjacent invert blocks 10 are connected to each other via the connecting plates. Note that the connecting holes 13 may be one or two, rather than multiple as in this embodiment.

[0046] Furthermore, as shown in Figure 2, each element 10e has two lifting fittings 14 at two locations along its longitudinal direction on the upper plate 10ts, which can engage with a hook attached to the end of a wire for lifting the element 10e with a wire from a crane (such as a crawler crane) and installing it on the ground at the bottom of the tunnel T.

[0047] Furthermore, as shown in Figures 1, 3, and 4, each element 10e is provided with a grout injection hole H3 for injecting grout between the element 10e and the ground when installed in the ground at the bottom of the tunnel, thereby filling the void between the element 10e and the ground. This grout injection hole H3 is cylindrical, penetrating the element 10e vertically (i.e., it is isolated from the hollow internal space). Therefore, the grout injected from the upper grout injection hole H3 passes through the cylindrical grout injection hole H3 and fills the space between the element 10e and the ground.

[0048] As shown in Figure 1, the upper plate 10ts of the invert block 10 has concrete pouring holes H1 for pouring concrete into the hollow interior in a later process, and concrete blowing holes H2 for blowing out the poured concrete.

[0049] As shown in the figure, the concrete placement hole H1 is formed at one location on the lower part of the upper plate 10ts of the invert block 10 when it is installed in the ground at the bottom of the tunnel T (near the center on the side opposite the side wall of the tunnel T where it is installed), and the concrete blowout holes H2 are formed at two locations on the higher part of the upper plate 10ts of the invert block 10 when it is installed in the ground at the bottom of the tunnel T (at the corner on the side wall side of the tunnel T where it is installed). Note that the number and position of the concrete placement holes H1 and concrete blowout holes H2 are not limited to the case shown in this embodiment. However, it is desirable that the concrete blowout holes H2 be formed at the corner on the side wall side of the tunnel T where it is installed so that the air inside can be smoothly discharged when concrete is placed.

[0050] In this embodiment, the invert block 10, which is composed of four (even) elements 10e, has a concrete placement hole H1 formed in element 10e-2, one of the two elements 10e (10e-2, 10e-3) located in the center. However, if there is an even number of elements 10e and these elements 10e are installed with a slope in the axial direction of the tunnel T, it is desirable to form the concrete placement hole H1 in the element 10e located at the lower position among the two elements 10e located in the center. In the case of an invert block 10 composed of an odd number of elements 10e, the concrete placement hole H1 is formed in the element 10e located in the center.

[0051] Furthermore, concrete pouring holes H1 may be formed in two or more locations (i.e., at least one on the side opposite the side wall of the tunnel T in which it is installed), and concrete blowout holes H2 may be formed in three or more locations (i.e., at least two on both sides of the side wall of the tunnel T in which it is installed).

[0052] Furthermore, in a later step, concrete is poured with the invert block 10 embedded in the ground at the bottom of the tunnel T. As shown in Figure 2, connecting pipes P are attached upwards to the concrete pouring hole H1 and the concrete blowing hole H2. This allows concrete to be poured into the invert block 10 and concrete to be blown out from the invert block 10 simply by exposing the connecting pipes P from the ground in which the invert block 10 is embedded. A detachable cap (not shown) is attached to the tip of the connecting pipe P to prevent soil and sand from entering the interior when concrete is not being poured.

[0053] In this embodiment, the connecting pipe P is a steel pipe with a diameter of approximately 6 inches, and has the same diameter as the pumping pipe (a pipe attached to a concrete pump truck for pumping concrete) which is connected via a joint when concrete is poured in a later process. However, the diameter of the connecting pipe P is determined according to the diameters of the concrete pouring hole H1 and the concrete blowing hole H2 and the diameter of the pumping pipe, and is not limited to 6 inches in this embodiment.

[0054] Here, the flow of concrete when pouring concrete into the invert block 10 in the subsequent process (the process after installing the invert block 10) will be explained using Figures 7 and 8. Figure 7 is a plan view showing the flow direction of the concrete poured into the invert block in Figure 1, and Figure 8 is a cross-sectional view of Figure 7.

[0055] As described above, the concrete pouring hole H1 is formed at a lower position on the upper plate 10ts of the invert block 10 when it is installed in the ground at the bottom of the tunnel T, and the concrete blowout hole H2 is formed at a higher position on the upper plate 10ts of the invert block 10 when it is installed in the ground at the bottom of the tunnel T.

[0056] Therefore, as shown in Figures 7 and 8, when concrete C is poured into the invert block 10 from the concrete pouring hole H1 formed in element 10e-2 (more specifically, the connecting pipe P attached to the concrete pouring hole H1), the concrete C flows from directly below the concrete pouring hole H1 through the gap in the support member 11 to the other elements 10e-1, 10e-3, and 10e-4, and fills the hollow structure by pushing out the air inside through the concrete blowing hole H2. Then, when the concrete C is blown out from the concrete blowing hole H2 formed at the highest position (more specifically, the connecting pipe P attached to the concrete blowing hole H2), it can be inferred that the entire interior of the invert block 10 has been filled with concrete C.

[0057] As shown in Figure 8, the tips of the connecting pipes P attached to the concrete pouring hole H1 and the connecting pipes P attached to the concrete blowing hole H2 are located at the boundary between the base layer L3 and the upper subbase L2 that constitute the pavement subgrade L (that is, the boundary between the subbase layer (lower subbase L1, upper subbase L2) and the asphalt layer (base layer L3, surface layer L4)). Therefore, when pouring concrete C into the embedded invert block 10 in a later process, the two layers of surface layer L4 and base layer L3 (that is, the asphalt layer) can be peeled off to expose the tips of the connecting pipes P, the lid can be removed, and the connecting pipe P attached to the concrete pouring hole H1 can be connected to the pumping pipe from the pump truck via a joint (not shown).

[0058] In this way, by attaching connecting pipes P to the concrete pouring holes H1 and concrete blowout holes H2, when pouring concrete into the invert block 10, it is only necessary to peel off the base layer L3 and surface layer L4, which are asphalt layers, to expose the tip of the connecting pipe P. There is no need to remove the subgrade RB to expose the invert block 10 itself, making it possible to pour concrete easily.

[0059] In this embodiment, the lower subbase L1, upper subbase L2, base layer L3, and surface layer L4 are sequentially stacked to form the pavement subbase layer L, and the tip of the connecting pipe P is located at the boundary between the base layer L3 and the upper subbase L2. However, the composition of the pavement subbase layer L and the position of the tip of the connecting pipe P are not limited to this. In other words, the pavement subbase layer L is formed of a subbase layer and an asphalt layer stacked on the subbase layer, and the position of the tip of the connecting pipe P is at or below the boundary between the subbase layer and the asphalt layer (i.e., below the asphalt layer). If the position of the tip of the connecting pipe P is below the boundary between the subbase layer and the asphalt layer, when pouring concrete C into the invert block 10, the two layers of the surface layer L4 and base layer L3 (i.e., the asphalt layer) and a part of the subbase layer are peeled off to expose the tip of the connecting pipe P.

[0060] Here, the area to be stripped of the temporary pavement may be the entire area where the invert blocks 10 for concrete placement are embedded, or it may be just the area around the connecting pipe P. However, when constructing a highway, it is desirable to strip the temporary pavement over the entire area where the invert blocks 10 for concrete placement are embedded. Also, when constructing a general road, it may be sufficient to strip only the temporary pavement around the connecting pipe P.

[0061] As described above, the invert block 10 of this embodiment is composed of four elongated steel elements 10e that are interconnected in the axial direction along their longitudinal side, and has a hollow structure with an upper plate 10ts, a lower plate 10us, and a side plate 10sf. Inside the connection opening 10ea of ​​the elements 10e formed on the longitudinal side where the elements 10e are connected, a support member 11 is installed to connect the internal spaces of both elements 10e and to support loads from above.

[0062] Therefore, by simply installing four steel elements 10e on site and connecting them to each other, the invert block 10 is constructed and installed in the ground at the bottom of the tunnel. Furthermore, this avoids the length of construction time that would occur if the invert were installed using cast-in-place concrete, and the increased costs and difficult installation work that would occur if a precast invert were transported into the tunnel and installed.

[0063] Therefore, by using the invert block 10 of this embodiment, it becomes possible to perform tunnel bulging prevention work in a short construction period, at low cost, and easily.

[0064] Next, the process for installing the invert block 10 described above into tunnel T will be explained using Figures 9 to 24. Here, as an example, we will explain the case where the invert block 10 is installed under one lane in tunnel T, which is a one-way tunnel with two lanes in each direction.

[0065] Figure 9 is an explanatory diagram showing the excavation machine delivery process, which is one step in the continuous installation of the invert blocks shown in Figure 1 along the axial direction of the tunnel; Figure 10 is an explanatory diagram showing the initial excavation process following Figure 9; Figure 11 is an explanatory diagram showing the floor-laying machine delivery process following Figure 10; Figure 12 is an explanatory diagram showing the excavation and floor-laying process following Figure 11; Figure 13 is an explanatory diagram showing the unloading and transport machine delivery process following Figure 12; Figure 14 is an explanatory diagram showing the entry and withdrawal process of the material transport vehicle following Figure 13; Figure 15 is an explanatory diagram showing the material unloading process following Figure 14; Figure 16 Figure 15 is an explanatory diagram showing the temporary placement of members, Figure 17 is an explanatory diagram showing the member installation process, Figure 18 is an explanatory diagram showing the backfill injection process, Figure 19 is an explanatory diagram showing the backfilling machinery delivery process, Figure 20 is an explanatory diagram showing the backfilling process, Figure 21 is an explanatory diagram showing the compaction process, Figure 22 is an explanatory diagram showing the heavy equipment removal and paving machinery delivery process, Figure 23 is an explanatory diagram showing the temporary paving process, Figure 24 is an explanatory diagram showing the temporary pavement removal and excavation process, Figure 23. In these drawings, (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel.

[0066] First, as shown in Figure 9, one lane is designated as a restricted zone where general vehicle traffic is restricted in order to lay the invert blocks 10, while the other lane is designated as a traffic lane where general vehicle traffic is permitted. Then, a trailer 21 equipped with a backhoe (for example, a 0.45 class backhoe) 20, which will be used as an excavating machine, is brought in from the traffic lane to the restricted zone, and the backhoe 20 is unloaded and brought into the restricted zone (excavating machine delivery process). The trailer 21 then exits the tunnel from the end of the restricted zone (the end opposite the entrance).

[0067] In this embodiment, a backhoe is used as the heavy machine for excavating the ground, but a hydraulic excavator other than a backhoe may also be used.

[0068] Next, as shown in Figure 10, a dump truck (for example, a 10-ton dump truck) 22 is moved from the traffic lane into the restricted zone and then backed up to the loading position for the excavated soil. Then, the backhoe 20 is used to excavate the soil in the restricted zone and load it onto the dump truck 22 (initial excavation process). Once the dump truck 22 has loaded the soil up to the specified weight, it exits the tunnel from the end of the restricted zone.

[0069] Next, as shown in Figure 11, a trailer 21 equipped with a small backhoe (for example, a 0.1 class backhoe) 23 as a floor-setting machine is brought in from the traffic lane into the restricted area, and the backhoe 23 is lowered between the backhoe 20 and the excavated area (the area excavated by the backhoe 20) S (floor-setting machine delivery process). Note that because the backhoe 20 is in front of the trailer 21 and it cannot proceed through the restricted area, safety is ensured by a speed control vehicle (not shown) introduced into the traffic lane, which controls the speed of following general vehicles. The trailer 21 then exits the restricted area into the traffic lane and out of the tunnel when it is ahead of the speed control vehicle.

[0070] Next, as shown in Figure 12, the backhoe 20 excavates the soil in the restricted zone and loads it onto the dump truck 22, while a small backhoe 23 levels the ground surface of the excavated area S (excavation and ground leveling process). Once the dump truck 22 has loaded the soil up to the specified weight, it exits the tunnel from the end of the restricted zone.

[0071] Next, as shown in Figure 13, a trailer (not shown) equipped with a crawler crane (e.g., a 4.9t lifting crawler crane) 24, which will be used as unloading and transporting machinery, is brought in from the traffic lane into the restricted area, and the crawler crane 24 is lowered in front of the excavated area S (on the opposite side of the direction in which excavation and bed preparation will be carried out in the excavated area S) (unloading and transporting machinery installation process). Note that the trailer cannot proceed through the restricted area because the excavated area S is ahead of it. Therefore, safety is ensured by a speed control vehicle (not shown) introduced into the traffic lane, which controls the speed of following general vehicles. The trailer then exits the restricted area into the traffic lane and leaves the tunnel when it is ahead of the speed control vehicle. During this time, the excavation and bed preparation process (see Figure 12) continues.

[0072] Next, as shown in Figure 14, a dump truck (e.g., a 4-ton dump truck) 25, which serves as a material transport vehicle loaded with element 10e, is moved from the traffic lane between the excavated area S of the restricted zone and the crawler crane 24, and then reversed to a position close to the crawler crane 24 (material transport vehicle entry and reversal process). During this time, the excavation and bed preparation process (see Figure 12) continues.

[0073] Next, as shown in Figure 15, the elements 10e loaded onto the dump truck 25 are unloaded using the crawler crane 24 (component unloading process). During this time, the excavation and bed preparation process (see Figure 12) continues.

[0074] Next, as shown in Figure 16, the unloaded elements 10e are temporarily placed in front of the excavated area S (temporary placement of components). During this time, the excavation and bed preparation process (see Figure 12) continues. The dump truck 25 carrying the elements 10e cannot proceed through the restricted zone because the excavated area S is ahead of it. Therefore, safety is ensured by a speed control vehicle (not shown) introduced into the traffic lane, which regulates the speed of following general vehicles. The dump truck then exits the restricted zone into the traffic lane and leaves the tunnel when it is ahead of the speed control vehicle. During this time, the excavation and bed preparation process (see Figure 12) continues.

[0075] Next, as shown in Figure 17, the crawler crane 24 is used to install the unloaded elements 10e into the excavated area S (member installation process). That is, as shown in the figure, the longitudinal direction of the elements 10e is oriented in the direction of the tunnel circumference, and the crawler crane 24 installs the elements 10e along the axial direction (installation direction) of the tunnel T. Then, the amount of expansion and contraction of the support bolts 15 is adjusted to align the heights between the four elements 10e, and the connecting bolts 10eg are screwed into nuts 10ec to connect the elements 10e, thereby forming an invert block 10 that integrates these elements 10e (see Figures 3 and 4).

[0076] As mentioned above, in this embodiment, four elements 10e are installed to form one invert block 10. The axial length of the tunnel T formed by these elements 10e is, for example, 3m. However, this length varies depending on the number of elements 10e installed and the width of the elements 10e, and is not limited to the value of 3m. During this time, the excavation and bed preparation process (see Figure 12) continues.

[0077] Here, the work of installing (setting up) the elements 10e, the work of aligning the heights of the installed elements 10e, and the work of connecting the elements 10e with aligned heights to form the invert block 10 may be performed on an element 10e-by-element basis, or it may be performed all at once on all the elements 10e that make up the invert block 10.

[0078] More specifically, the invert block 10 may be formed by repeatedly installing each element 10e one by one, aligning their heights, and connecting them. Alternatively, the invert block 10 may be formed by repeatedly installing each element 10e that make up the invert block 10, aligning their heights, and then connecting all the elements 10e at once. Alternatively, the invert block 10 may be formed by installing all the elements 10e that make up the invert block 10 at once, aligning the heights of all the elements 10e that make up the invert block 10 at once, and then connecting all the elements 10e that make up the invert block 10 at once.

[0079] Next, once one invert block 10 has been formed, grout (backfill material) G is injected between the invert block 10 and the installation ground, as shown in Figure 18 (backfill injection process). In this embodiment, a rapid-strength type grout G is used, which has excellent rapid strength development properties and reaches high strength in a short time. However, grout other than the rapid-strength type may also be used.

[0080] In this process, first, to prevent the injected grout G from flowing out, a spill-prevention wall W made of concrete panels (plywood) or the like is erected on the sides of the invert block 10 (specifically, the sides of element 10e-4 on the tunnel axial end side and the tunnel sidewall side of the invert block 10), and sandbags D are placed outside the spill-prevention wall W to prevent it from collapsing. Then, a dump truck (for example, a 2-ton dump truck) 26 loaded with grout G and grout pumping equipment GE for pumping the grout G is brought into the restricted zone, and grout G is injected between the bottom surface of the invert block 10 and the installation ground through the grout injection holes H3 (see Figures 1, 3, and 4) provided in each element 10e. In this embodiment, the grout is injected after one day's worth of construction. However, the timing of grout injection is not limited to after one day's worth of construction, and other injection timings are also possible. Furthermore, the components used to prevent the overturning of the runoff prevention wall W may be other than the sandbags D.

[0081] Furthermore, between the backfill material injection process and the backfilling process described later, connecting pipes P (see Figures 2 and 8) are attached to the concrete pouring holes H1 and concrete blowout holes H2 formed in each element 10e. In addition, a cap (not shown) is placed over the tip of the connecting pipe P to prevent soil from entering. However, the connecting pipes P are not shown in Figures 18 to 24. During this time, the excavation and base preparation process (see Figure 12) continues.

[0082] Next, once the grout has hardened, the runoff prevention wall W and sandbags D are removed, and as shown in Figure 19, a backhoe (for example, a 0.45 class backhoe) 27 for backfilling with subgrade material and a compaction roller 28 for compacting the backfilled subgrade material are brought into the restricted area (backfilling machine delivery process). During this time, the excavation and subgrade preparation process (see Figure 12) continues.

[0083] Next, as shown in Figure 20, a dump truck (e.g., a 4-ton dump truck) 29 loaded with backfill soil (subgrade material) is brought from the traffic lane into the restricted area and introduced between the backhoe 27 and the compaction roller 28. Then, the backhoe 27 transfers the subgrade material from the dump truck 29 onto the invert block 10 (i.e., interconnected and integrated elements 10e) to backfill that area (backfilling process). In Figure 20 and the following Figure 21, the symbol ES indicates the subgrade material, which is the backfill soil. After the subgrade material has been transferred and the dump truck 29 is empty, it moves from the restricted area into the traffic lane and exits the tunnel. During this time, the excavation and subgrade preparation process (see Figure 12) continues. Furthermore, although the illustration shows backfilling after installing the number of elements 10e required to form one invert block 10, it is of course possible to backfill after installing the number of elements 10e required to form multiple invert blocks 10.

[0084] Next, as shown in Figure 21, the subgrade material ES is compacted with a compaction roller 28 to form the subgrade RB (Figure 22) (compaction process). In this compaction process, the subgrade material ES is compacted, so the surface of the formed subgrade RB is lower than the surrounding road surface (see Figure 22). During this time, the excavation and subgrade preparation process (see Figure 12) continues.

[0085] For example, if Monday to Friday is considered one work unit in order to open the restricted zone to general vehicles on Saturdays and Sundays, then each process from the excavation and bed preparation process (Figure 12) to the compaction process (Figure 21) described above is repeated sequentially from Monday to Thursday to form a continuous invert block structure in which invert blocks 10 are continuously installed along the axial direction of the tunnel, and these are embedded in the roadbed RB, which is made of compacted roadbed material ES. Here, as mentioned above, adjacent invert blocks 10 are connected by screwing bolts through through holes formed in the connecting plates into nuts in the connecting holes 13, so that their heights are aligned.

[0086] It should be noted that the work unit and the process within each work unit are not limited to those described in this embodiment and can be freely configured.

[0087] After the final compaction process on Thursday (Figure 21) is completed, as shown in Figure 22, various excavation equipment other than the compaction roller 28 is removed from the tunnel, and paving equipment such as the asphalt finisher 33 is brought in (excavation equipment removal and paving equipment arrival process). Depending on the progress of the work, as shown in Figure 22, the backfilled excavated area S may contain areas where invert blocks 10 are embedded and areas where they are not.

[0088] Next (on Friday in this embodiment), as shown in Figure 23, temporary paving is carried out on the excavated area S that was excavated from Monday to Thursday (temporary paving process). This is done to minimize the impact on general traffic caused by one-way traffic for construction, as the restricted zone is opened to general traffic on Saturday and Sunday, as mentioned above. In this embodiment, temporary paving is carried out by forming a pavement layer L on top of the subgrade RB by sequentially stacking the lower subgrade L1, upper subgrade L2, base layer L3, and surface layer L4. After the temporary paving is completed, the paving heavy machinery that was brought in is removed and the restricted zone is opened.

[0089] Next (in this embodiment, on the following Monday), as shown in Figure 24, the temporary pavement in the excavated area S where the invert blocks 10 are not embedded is removed with a backhoe 20 (temporary pavement removal process). Then, each of the processes described above, from the excavation and base preparation process (Figure 12) to the compaction process (Figure 21), is repeated sequentially from Monday to Thursday. Furthermore, after the completion of the final compaction process (Figure 21) on Thursday, the excavation heavy equipment removal and paving heavy equipment delivery process (Figure 22) is carried out, and on Friday, the temporary paving process (Figure 23) is carried out.

[0090] Once multiple consecutive invert blocks 10 (continuous invert block structure) have been embedded in part or throughout one lane of tunnel T as described above, the next process involves pouring concrete into the embedded invert blocks 10. Next, the process of pouring concrete into the invert blocks 10 will be explained using Figures 25 to 28.

[0091] Figure 25 is an explanatory diagram showing the temporary pavement removal process, which is one step in pouring concrete into the buried invert block; Figure 26 is an explanatory diagram showing the concrete pouring commencement process, which follows Figure 25; Figure 27 is an explanatory diagram showing the concrete pouring execution process, which follows Figure 26; and Figure 28 is an explanatory diagram showing the re-temporary pavement process, which follows Figure 27. In these drawings, (a) is an explanatory diagram viewed from above, and (b) is an explanatory diagram viewed from the axial cross-section of the tunnel.

[0092] First, as shown in Figure 25, the temporary pavement is removed using a backhoe (for example, a 0.45 class backhoe) 30 as an excavation machine to expose the tips of the connecting pipes P attached to the concrete pouring holes H1 and concrete blowout holes H2 (temporary pavement removal process). As mentioned above, in this embodiment, the tip of the connecting pipe P is located at the boundary between the base layer L3 and the upper subbase layer L2 that constitute the pavement road layer L, so the two layers (asphalt layers) of the surface layer L4 and base layer L3 are removed, but the two layers (subbase layers) of the upper subbase layer L2 and lower subbase layer L1 are not removed. However, in Figures 25 to 27, the surface layer L4, base layer L3, upper subbase layer L2, and lower subbase layer L1 are not shown.

[0093] As mentioned above, the area of ​​the temporary pavement to be peeled off in order to expose the tip of the connecting pipe P may be limited to the area around the connecting pipe P, or it may be the entire area where the invert block 10 into which the concrete will be poured is embedded, but here we are using the latter peeling area.

[0094] Furthermore, in this embodiment, when pouring concrete into the existing invert block 10, each of the processes from the excavation and base preparation process (Figure 12) to the compaction process (Figure 21) described above is carried out in parallel within different ranges, as shown in Figure 25 and Figures 26 and 27 described below. In this way, by carrying out the pouring of concrete into the buried existing invert block 10 and the installation and burying of the invert block 10 in the unexcavated area in parallel within different ranges, it becomes possible to complete the series of operations in a shorter construction period.

[0095] Now, once the tip of the connecting pipe P is exposed in the temporary pavement removal process shown in Figure 25, the mixer truck 31, which transports ready-mix concrete, and the concrete pump truck 32, which docks with the mixer truck 31 to receive the ready-mix concrete into a hopper and pumps the concrete through a pumping pipe 32a using an equipped pump (not shown), are introduced into the restricted zone, as shown in Figure 26. The caps on the tips of the connecting pipes P attached to the concrete placement holes H1 and concrete discharge holes H2 are removed, and the pumping pipe 32a of the concrete pump truck 32 is connected to the connecting pipe P attached to the concrete placement hole H1 (in this case, the connecting pipe P of the invert block 10 buried closest to the concrete pump truck 32) using a joint. Then, concrete placement into the invert block 10 is started (concrete placement start process). After the mixer truck 31 has loaded the required amount of ready-mix concrete into the hopper of the concrete pump truck 32, it moves out into the traffic lane and exits the tunnel.

[0096] In this embodiment, high-flow concrete is used as the concrete to be poured. High-flow concrete uses less water than ordinary concrete and has high fluidity, so it can be reliably filled to every corner of the invert block 10 without the need for vibration or compaction. However, it is also possible to use concrete other than high-flow concrete, such as ordinary concrete or fluidized concrete, as the concrete to be poured.

[0097] Once concrete placement has begun as shown in Figure 26, the concrete pumping pipe 32a of the concrete pump truck 32 is sequentially connected to the connecting pipes P attached to the concrete placement holes H1 of each embedded invert block 10, and the concrete is pumped and placed.

[0098] When pouring concrete into each invert block 10, the connecting pipe P attached to the two concrete discharge holes H2 from which concrete is discharged first is sealed to prevent leakage as soon as it starts to discharge. The other connecting pipe P attached to the concrete discharge hole H2 is also sealed as soon as concrete starts to discharge. After sealing both connecting pipes P attached to the concrete discharge holes H2, the connecting pipe P attached to the concrete pouring hole H1 is also sealed.

[0099] In this way, as shown in Figure 27, concrete is poured into the buried invert blocks 10 (concrete pouring process) to create the invert. Here, as mentioned above, the installation and burial of the invert blocks 10 and the pouring of concrete into the buried existing invert blocks 10 are carried out in parallel. However, since the invert is created by pouring concrete into the invert blocks 10, in the final stage, these processes are not carried out in parallel, and only the pouring of concrete into the existing invert blocks 10 is performed.

[0100] Then, after the invert is constructed by pouring concrete into all the embedded invert blocks 10, the peeled base layer L3 and surface layer L4 are sequentially stacked on top of the upper subgrade L2, as shown in Figure 28, and temporary paving is performed (temporary paving process). Here, if the temporary pavement is peeled only in the area around the connecting pipe P, in the temporary paving, instead of sequentially stacking the base layer L3 and surface layer L4, for example, coarse-grained asphalt concrete may be used to fill the peeled area. Note that the connecting pipe P is not shown in Figure 28. Also, temporary paving is performed in the excavated area S where the invert blocks 10 were buried (see Figure 23).

[0101] In this way, concrete is poured into the invert blocks 10 embedded in one lane of tunnel T, thereby creating an invert. Once the invert is created by embedding the invert blocks 10 (Figures 9 to 24) and pouring concrete (Figures 25 to 28) throughout one lane of tunnel T, the same process is carried out for the other lane to create an invert. Therefore, a continuous invert block structure, which consists of multiple invert blocks 10 connected in the axial direction of the tunnel, is installed in multiple rows (two rows in this embodiment) along the axial direction of the tunnel. Then, two invert blocks 10 (two inverts) facing each other in the circumferential direction of tunnel T form an inverted arch shape along the circumferential direction of tunnel T (see Figure 2). When installing the invert blocks 10 in the other lane, they are fastened with bolts to the opposing invert blocks 10 in the first lane, where concrete has already been poured.

[0102] Finally, the entire area of ​​tunnel T, which has been temporarily repaved, is stripped, and the final finishing step, permanent paving (paving with the original thickness), is carried out, completing the entire process.

[0103] Although the invention made by the present inventors has been specifically described above based on embodiments, the embodiments disclosed herein are illustrative in all respects and are not limited to the disclosed art. That is, the technical scope of the present invention should not be interpreted restrictively based on the description in the embodiments above, but rather should be interpreted in accordance with the claims, and includes art equivalent to the art described in the claims and all modifications that do not depart from the gist of the claims. [Industrial applicability]

[0104] The above description has focused on the installation of the invert block of the present invention in a tunnel that is already in use, but it can also be installed in a newly constructed tunnel. [Explanation of symbols]

[0105] 10 Invert Blocks 10e element 10ea connection opening 10eb Rib 10ec nut 10ed connection board 10ee sealant 10ef connection plate 10eg connecting bolt 10eh occlusion plate 10sf side plate 10sf-1 Longitudinal side plate 10sf-2 Short side side plate 10ts top plate 10us lower board 11 Support member 12 stakes 13 Connection hole 14 Hanging hardware 15 Support bolts 16 bases 17 Nuts 20 Backhoe 21 Trailer 22 Dump trucks 23 Backhoe 24 Crawler Cranes 25 Dump trucks 26 Dump trucks 27 Backhoe 28 Compaction roller 29 Dump trucks 30 Backhoe 31 Mixer car 32 Concrete pump trucks 32a Pressure pipe 33 Asphalt finisher C Concrete D Sandbags ES subgrade material G Grout (backfill material) GE Grout Pumping Equipment H1 Concrete pouring hole H2 Concrete discharge hole H3 Grout injection hole H4 bolt hole L Pavement layer L1 Lower subgrade L2 Upper Subgrade L3 base layer L4 surface layer P connecting pipe RB roadbed S Excavated area T Tunnel W Leakage prevention wall

Claims

1. A method of restricting traffic to one of the two lanes and installing invert blocks in the ground at the bottom of the tunnel by connecting multiple steel elements, A first step is to prepare a plurality of elongated elements, which form a box-shaped hollow invert block consisting of an upper plate, a lower plate, and side plates, by installing a support member in a connecting opening through which the elements are connected, which connects the internal spaces of both elements and supports the load from above, A second step involves excavating the ground at the bottom of the tunnel, orienting the longitudinal direction of the elements in the direction of the tunnel circumference, and installing the elements in parallel in the axial direction of the tunnel in order to form the invert block, A third step is to align the heights of the installed elements, A fourth step is to connect the elements of the same height to form the invert block, A fifth step involves injecting backfill material between the bottom surface of the formed invert block and the installation ground, A sixth step involves backfilling the invert blocks with subgrade material after injecting backfill material to form the subgrade, A method for installing invert blocks, characterized by having [a certain feature].

2. The second, third, and fourth steps described above are considered as a single integrated process, and the invert block is formed by repeatedly installing the elements one by one, aligning their heights, and connecting them. The method for installing invert blocks according to claim 1, characterized in that it is a method for installing invert blocks as described in claim 1.

3. The second and third steps described above are considered as a single integrated process, and the work of installing the elements constituting the invert block one by one and aligning their heights is repeated. In the fourth step described above, all the elements are connected together to form the invert block. The method for installing invert blocks according to claim 1, characterized in that it is a method for installing invert blocks as described in claim 1.

4. In the second step described above, all the elements constituting the invert block are installed together. In the third step described above, the heights of all the elements constituting the invert block are aligned at once. In the fourth step described above, all the elements constituting the invert block are connected together to form the invert block. The method for installing invert blocks according to claim 1, characterized in that it is a method for installing invert blocks as described in claim 1.

5. Prior to injecting the backfill material, an outflow prevention wall is erected on the side of the element on the tunnel axial end side of the invert block and on the side of the invert block on the tunnel side wall side to prevent the backfill material from flowing out. After the backfill material has been injected and before the invert blocks have been backfilled, the spill-prevention wall is removed. A method for installing an invert block according to any one of claims 1 to 4.

6. The elements are installed in quantities equal to the number of blocks that form the invert block. A method for installing an invert block according to any one of claims 1 to 4. Installation method.

7. After repeating steps 2 to 6 over a predetermined period, a seventh step is performed in which a subgrade layer and an asphalt layer are laminated on the subgrade, A method for installing an invert block according to any one of claims 1 to 4, characterized by having the following:

8. An eighth step of peeling off the roadbed layer and the asphalt layer, It has, After performing the eighth step, perform the second to seventh steps. The method for installing invert blocks according to claim 7, characterized in that it is as follows.

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