JP2024152058A - Excavation and support construction method for tunnel intersection - Google Patents

Abstract

To provide an excavation and timbering construction method which can efficiently conduct tunnel construction without executing widening more than necessary at a tunnel intersection part between a main pit and a working pit.SOLUTION: An excavation and timbering construction method includes the steps of: progressing the excavation of a working pit into a main pit and thereafter, in a main pit connection part of the working pit, forming a groove having a depth to bury intersection part timbering at a fixed width so that a bottom face of an upper side is located at a timbering installation position of the main pit; installing the intersection part timbering at the inside of the groove; burying the intersection part timbering into natural ground by concrete; and executing excavation as is a cross-section of the working pit into the main pit so as to be timbered and thereafter again excavating and timbering a section of the main pit connection part at a cross-section same as a normal cross-section of the main pit. The step of again excavating and timbering the section of the main pit connection part includes the steps of: in the intersection part timbering part, fixing edge parts on the working pit side of the timbering of the main pit are individually, or after connection with a connection member, to an upper face beam part of the intersection part timbering; fixing the upper face beam part or the connection member to the natural ground with rock bolts; and removing a pillar part of the intersection part timbering.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for excavating and constructing supports at tunnel intersections, and in particular to a method for excavating and constructing supports at tunnel intersections where a main tunnel and a work tunnel intersect, in which a trench is formed to embed an intersection support shaped to encompass the cross section of the work tunnel at the tunnel intersection, the intersection support is then installed in the ground with concrete, and underground beam supports are constructed, allowing tunnel construction to proceed efficiently without unnecessarily widening the intersection.

In long construction projects, such as the construction of new railway tunnels, excavation only from both ends, the starting and ending points, limits the amount of excavation work that can be done in a day, and it takes a very long time to complete. Therefore, a method is used in which a work tunnel is excavated from the side in the middle of the construction section, and excavation is then carried out toward the starting and ending points using this as a base.

In normal tunnel construction, shoring is installed immediately at the tunnel's excavation end, known as the face, to prevent the excavation surface from collapsing and ensure the safety of the work. The basic rule is to make the shoring roughly horseshoe-shaped to match the cross-sectional shape of the tunnel, but when a work tunnel is installed, the cross-section of the main tunnel becomes asymmetric at the tunnel intersection where the work tunnel and the main tunnel intersect, making it impossible to install shoring of a normal shape. Therefore, with conventional technology, the connection between the work tunnel and the main tunnel is widened and a portal-shaped shoring is constructed on the work tunnel side, and then shoring for the main tunnel is constructed that is specially manufactured to match the asymmetric cross-section of the main tunnel.

Patent Document 1 discloses a construction method for a work tunnel intersection, in which a steel support member for the work tunnel widening section, which has a height that exceeds the arch-shaped portion of the main tunnel tunnel, is created and constructed at the intersection of the work tunnel and the main tunnel to ensure the safety of the intersection, and then excavation of the intersection is continued. Ultimately, a gate-shaped support stand is installed on the near side of the excavation direction of the widening work tunnel, and a structure is created in which one end of the steel support member for the main tunnel intersection is supported.

Patent Document 2 discloses a tunnel junction structure in which an arch-shaped support structure is provided at the boundary of the tunnel junction with an adit that connects to the main tunnel from the direction that intersects with the main tunnel, and the end of the steel support structure for the main tunnel at the tunnel junction on the adit side is fixed to the arch-shaped support structure.

Whether it is the portal-shaped support in Patent Document 1 or the arch-shaped support in Patent Document 2, they are installed later in the widened space. The cross-sectional shape of the support for the main tunnel at the tunnel intersection is asymmetrical, and the end on the work tunnel side is formed to stop halfway in a horseshoe shape, so when pressure is applied from the surrounding ground, the end on the work tunnel side is subjected to a force that spreads outward. As a result, a moment is applied to the support base, such as the portal-shaped support base that fixes this end, causing it to collapse towards the work tunnel side. With conventional technology, in order to withstand this moment, the support base is required to have a highly rigid structure, such as by using steel sections with a large cross-sectional area, and there was also the issue that the base base must also be made large.

Furthermore, because such a support is installed outside the original horseshoe-shaped cross section of the main tunnel, the shape of the support on the work tunnel side deviates from the original horseshoe-shaped cross section and becomes an arch shape with a small curvature and a nearly flat shape. As a result, the left-right symmetry of the cross section of the main tunnel at the tunnel intersection is reduced, and the stability of the ground is also likely to decrease.
Therefore, a method is required for excavating tunnel intersections and constructing supports that does not widen the cross section of the main tunnel more than necessary and that allows the installation of supports in a shape that is close to the original horseshoe-shaped cross section.

JP 2020-159061 A JP 2017-008568 A

The present invention was made in consideration of the problems with the conventional tunnel intersection excavation and support construction methods described above, and the object of the present invention is to provide a method of excavating and constructing supports at tunnel intersections, which allows tunnel construction to proceed efficiently without unnecessarily widening the intersection by installing intersection supports in a trench formed to bury an intersection support shaped to encompass the cross section of the work tunnel at the tunnel intersection where the main tunnel and the work tunnel intersect, and then burying the intersection supports in the ground with concrete to construct underground beam supports.

The method of excavating and constructing supports at a tunnel intersection, which has been made to achieve the above-mentioned object, is a method of excavating and constructing supports at a tunnel intersection where the main tunnel and the work tunnel intersect, in a construction method in which the main tunnel is excavated based on the excavation of a preceding work tunnel, and includes the steps of forming a trench of a predetermined shape deep enough to embed an intersection support having a shape that encompasses the work tunnel cross section at a constant width from the inner surface of the main tunnel connection part of the work tunnel toward the ground, so that the top surface of the embedded intersection support is the support installation position of the main tunnel cross section, installing the intersection support in the trench of the predetermined shape, and attaching the intersection support to the ground with concrete. The method includes the steps of burying the tunnel in the mountain and constructing an underground beam support, excavating the tunnel into the main tunnel with the work tunnel cross section and supporting it, and then excavating and supporting the main tunnel connection section again with the same cross section as the normal cross section of the main tunnel. The step of excavating and supporting the main tunnel connection section again with the same cross section as the normal cross section of the main tunnel includes the steps of connecting and fixing the work tunnel side end of the main tunnel support to the upper beam part of the intersection support when the main tunnel is the intersection support part, connecting the work tunnel side ends or near the ends of the multiple supports of the main tunnel with connecting members if necessary, fixing the upper beam part or the connecting member to the ground with rock bolts, and removing the columns of the intersection support.

The intersection support is preferably a lattice structure.
It is preferable that the intersection support is a gate-type support, and the specified shape is a rectangular cross-sectional shape that matches the gate-type support.
The step of embedding the intersection support in the ground with concrete to construct an underground beam support preferably comprises constructing the underground beam support by applying sprayed concrete to the intersection support.

It is preferable to remove the upper beam portion of the intersection support after the step of fixing the connecting member to the ground with a rock bolt.
When the work tunnel is excavated diagonally in the horizontal direction relative to the main tunnel, it is preferable that the support structure of the work tunnel is installed in line with the extension direction of the main tunnel at its intersection with the main tunnel, and is installed in a direction perpendicular to the extension direction of the work tunnel at a certain distance from the intersection, and is installed so that the direction gradually changes between the extension direction of the main tunnel and the direction perpendicular to the extension direction of the work tunnel within a certain distance from the intersection.

According to the tunnel intersection excavation and support construction method of the present invention, the intersection support is installed in a trench formed to bury the intersection support, which is shaped to encompass the cross section of the working tunnel at the tunnel intersection, and then buried in the ground with concrete to construct the underground beam support, so the tunnel intersection does not need to be widened more than necessary. This prevents the stability of the ground from decreasing, and makes it possible to reduce construction costs and time.

In addition, according to the tunnel intersection excavation and support construction method of the present invention, the intersection support is constructed within the natural ground, making it possible to utilize the natural ground reaction force and to integrate it with the natural ground, thereby making it possible to reduce the size of the components and increase structural stability. By utilizing the natural ground in this way, it is possible to significantly reduce the risk of the intersection support collapsing in the weak axis direction or buckling due to concentrated loads.

Furthermore, according to the method of excavating and constructing supports at tunnel intersections of the present invention, the cross section of the main tunnel can be constructed with the same cross section at the connection section, so the excavation shape of the work tunnel does not spread outward and become flat, and excavation and support can be performed with a stable shape. This reduces construction costs and ensures the stability of the ground and the soundness of the supports.

FIG. 2 is a schematic diagram showing how tunnel construction is carried out using a tunnel intersection excavation and support construction method according to an embodiment of the present invention. FIG. 2 is a diagram showing the formation of a trench for supporting a tunnel intersection according to an embodiment of the present invention. FIG. 2 is a diagram showing the state of installing intersection support at a tunnel intersection according to an embodiment of the present invention. FIG. 2 is a diagram showing the state in which a tunnel intersection support according to an embodiment of the present invention is embedded in concrete. A diagram showing a schematic diagram of the support state of the main tunnel at the tunnel intersection according to an embodiment of the present invention. 1 is a flowchart illustrating a method for excavating a tunnel intersection and constructing a support structure according to an embodiment of the present invention. 1 is a flowchart illustrating a method for excavating a tunnel intersection and constructing a support structure according to an embodiment of the present invention.

Next, a specific example of an embodiment for carrying out the tunnel intersection excavation and support construction method according to the present invention will be described in detail with reference to the drawings.
Fig. 1 is a schematic diagram showing how to proceed with tunnel construction using a tunnel intersection excavation and support construction method according to an embodiment of the present invention. Fig. 1(a) shows a state where a work tunnel has advanced to an area where a main tunnel is to be excavated, Fig. 1(b) shows a state where the main tunnel has been excavated a certain distance in one direction and supports have been installed, and Fig. 1(c) shows a state where the main tunnel, including the tunnel intersection, has been excavated in the opposite direction to Fig. 1(b) and supports have been installed.

Referring to FIG. 1(a), in tunnel construction using the tunnel intersection excavation and support construction method according to an embodiment of the present invention, excavation is carried out from the side toward the planned excavation area of the main tunnel 10 of the tunnel to form a work tunnel (horizontal or inclined tunnel) 20. As the excavation progresses, work tunnel supports 21 are installed sequentially in the work tunnel 20. When the work tunnel 20 crosses the main tunnel 10 diagonally, in construction at a location more than a certain distance away from the main tunnel 10, the work tunnel supports 21 are installed so as to be perpendicular to the extension direction 22 of the work tunnel 20, but at the intersection with the main tunnel 10, they are installed in a direction along the extension direction 13 of the main tunnel 10, and within a certain distance from the intersection, they are installed so as to gradually change direction between the direction perpendicular to the extension direction 13 of the main tunnel 10 and the extension direction 22 of the work tunnel 20.

The work tunnel 20 here will be backfilled and sealed off after construction of the main tunnel 10 is completed, or left as is and used as a work passage for tunnel maintenance. As used in this specification, the work tunnel 20 is a general term for tunnels that cross the main tunnel 10 from the side, and includes those that are perpendicular to the main tunnel 10 and those that cross the main tunnel 10 at an angle other than 90°.

At the tunnel intersection 30 where the service tunnel 20 intersects with the main tunnel 10, the space expands in three directions, resulting in a wider and more complex cross-sectional shape than a normal cross-section. For this reason, in the conventional technology, the tunnel intersection 30 was excavated deeply, and support members were formed to support the main tunnel support, such as a sturdy gate-type support structure that stands independently in the space, and a specially shaped main tunnel support was formed that expands outward from the normal cross-section toward the support members.

As described in detail below with reference to Figures 2 to 4, a method of excavating a tunnel intersection 30 and constructing shoring according to an embodiment of the present invention involves forming a trench of a predetermined shape at the tunnel intersection 30 from the inner surface of the main tunnel connection part of the work tunnel 20 toward the natural ground, deep enough to embed an intersection shoring 31 of a shape that encompasses the cross section of the work tunnel at a certain width, installing the intersection shoring 31 in the trench, and then burying the intersection shoring 31 with concrete to form the intersection shoring 31 as an underground beam shoring. As it is only necessary to form a trench to embed the intersection shoring 31, there is no need to excavate the tunnel intersection 30 more than necessary.

The trench formed at this time is formed so that the top surface of the intersection support 31 in the upper trench is the support installation position for the main tunnel cross section, so even if the intersection support 31 is used as a support member for the main tunnel support, there is no need to give the main tunnel support a special shape that spreads outward. Furthermore, because it is formed as an underground beam support, the intersection support 31 can utilize the ground reaction force, and there is no need to create a support member with a strong structure that includes a foundation, as in conventional technology.

The intersection support 31 protects the passageway through which workers enter and exit during the excavation of the main tunnel 10, and serves as a support member for the main tunnel support when the main tunnel 10 is excavated at the tunnel intersection 30. The intersection support 31 is formed when the work tunnel 20 enters the planned excavation area of the main tunnel 10. Then, as shown in FIG. 1(a), after the work tunnel 20 enters the planned excavation area of the main tunnel 10, excavation continues with the work tunnel cross section, the excavation direction is changed from the extension direction 22 of the work tunnel 20 to the extension direction 13 of the main tunnel 10, and the cross section is widened to the cross-sectional shape of the main tunnel 10, preparing for the excavation of the main tunnel 10.

Next, as shown in Figure 1 (b), the planned excavation area of the main tunnel 10 is excavated in one direction along the extension direction 13 of the main tunnel 10, and main tunnel supports 11 are installed in the section where excavation has been completed.
Once excavation of a certain distance in one direction and installation of supports have been completed, return to the point where the tunnel has been widened to achieve the cross-sectional shape of the main tunnel 10 shown in Figure 1(a), and proceed with excavation and installation of supports for the main tunnel connection section 36, including the tunnel intersection 30, in the opposite direction to the excavation direction shown in Figure 1(b).
Here, the certain distance is a distance for ensuring at least the reinforcement range. The strength of the ground is likely to decrease at the tunnel intersection 30 where the work tunnel 20 intersects with the main tunnel 10 compared to a normal cross section. For this reason, it is required to firmly install the main tunnel support 11 as early as possible in a certain range of the main tunnel 10 on both sides of the tunnel intersection 30. This certain range is the reinforcement range. The reinforcement range is determined by the shape of the intersection between the work tunnel 20 and the main tunnel 10, and depending on the angle of intersection between the work tunnel 20 and the main tunnel 10, the certain range on both sides of the tunnel intersection 30 will be asymmetric.

In the main tunnel connection section 36, the work tunnel support 21 and the intersection support 31 are installed. In the section where only the work tunnel support 21 is installed, the excavation is carried out while removing the work tunnel support 21, and the main tunnel support 11 is installed according to the cross-sectional shape of the main tunnel 10 as the excavation proceeds. In the section where the intersection support 31 is installed, after excavation so that the upper beam of the intersection support 31 is exposed, the main tunnel support 11 is installed so that the end of the main tunnel support 11 on the work tunnel 20 side is fixed to the upper beam of the intersection support 31, and the upper beam of the intersection support 31 is fixed to the ground with a rock bolt (not shown), and then the column of the intersection support 31 is removed. This is because if the intersection support 31 is installed so that the cross-sectional shape of the main tunnel 10 is maintained even at the tunnel intersection 30, the column of the intersection support 31 will be located within the cross-sectional shape of the main tunnel 10. In this way, the cross-sectional shape of the main tunnel 10 is maintained even in the section where the intersection support 31 is installed, and as a result, the shape of the main tunnel support 11 basically does not change from the sections before and after it, but the side on the work tunnel 20 side ends halfway, and its end is supported by the upper beam of the intersection support 31, which is fixed with a rock bolt.
After the upper beam portion has been fixed to the ground with rock bolts in this manner, the pillar portion of the intersection support 31 can be removed at any time, but as mentioned above, reinforcement of the reinforcement area at the tunnel intersection 30 is required at an early stage, so in this embodiment, the main tunnel support 11 is maintained while excavation of the main tunnel 10 and installation of the main tunnel support 11 are carried out, and the pillar portion of the intersection support 31 is removed once reinforcement of the reinforcement area is completed.

In another embodiment, the ends of the main tunnel supports 11 on the working tunnel 20 side, which are installed in the section where the intersection supports 31 are installed, are connected to each other by a connecting member installed along the upper beam of the intersection supports 31 or a connecting member installed in the vicinity of the connecting member along the extension direction 13 of the main tunnel 10. The connecting member is a strong steel structure, and has a through hole for inserting a rock bolt when used by fixing to the ground with a rock bolt. The connecting member is used when strength is required from the upper beam of the intersection supports 31. When using the connecting member by fixing to the ground, the multiple ends or near ends of the main tunnel supports 11 on the working tunnel 20 side are connected from the inner space side of the main tunnel 10 by the connecting member, and the connecting member is fixed to the ground with a rock bolt, and the connecting member supports the ends or near ends of the main tunnel supports 11. At this time, by connecting the connecting members so that the through holes of the connecting members are located between the adjacent main tunnel supports 31, rock bolts can be installed without affecting the main tunnel supports 31. When the connecting members are used by fixing them to the natural ground, the upper beams of the intersection support 31 may be removed together with the columns. In this case, too, it is desirable to remove the upper beams and columns after excavating the main tunnel 10 in the reinforcement range and installing the main tunnel support 11, as described above.
Once the excavation and installation of supports for the main tunnel connection section 36 are completed, the excavation and installation of supports for the main tunnel 10 will proceed as shown in Figure 1 (c).

Figure 2 shows the formation of a trench for supporting a tunnel intersection according to an embodiment of the present invention. Figure 2(a) shows the state of the work tunnel 20 as viewed from the main tunnel 10 side at the tunnel intersection 30, and Figure 2(b) is a cross-sectional view of the work tunnel 20 including the trench.

To create the intersection support 31 at the tunnel intersection 30, excavation is performed toward the ground 60 in a specified shape on the side of the service tunnel 20 that has entered the planned excavation area of the main tunnel 10, forming a trench 34. The shape of the trench 34 at this time is the width and depth required to embed the intersection support 31. As an example, when embedding an intersection support 31 with an outermost dimension of 300 mm x 400 mm in cross section, the width and depth of the trench 34 are each 500 mm, taking into account the thickness of the concrete. These dimensions are just an example, and it goes without saying that the dimensions of the intersection support 31 and the associated dimensions of the trench 34 will be changed as appropriate depending on the purpose of the tunnel and the condition of the ground 60.

In Figure 2, the predetermined shape of the trench 34 is shown as a rectangle at the bottom 37 of the trench 34, but this is the case when the intersection support 31 is a portal support. When an arch-shaped support is used as the intersection support 31, the trench 34 is excavated so that the bottom 37 of the trench 34 has an arch shape to match the shape of the support.

Figure 3 is a diagram showing the state of installing intersection support at a tunnel intersection according to an embodiment of the present invention. Figure 3(a) shows the state of the work tunnel 20 seen from the main tunnel 10 side at the tunnel intersection 30, and Figure 3(b) is a cross-sectional view of the work tunnel 20 including the groove.

Referring to Fig. 3, an intersection support 31 is installed in the formed trench 34. The intersection support 31 shown in the figure is a gate-type support, and includes a column portion 33 and an upper beam portion 32 installed on the column portion 33. The intersection support 31 may be made of high-strength steel such as H-shaped steel or I-shaped steel, but when it is embedded in concrete later, there is a risk of cavities being generated on the side of the ground 60, which is the back side of the steel. Therefore, in one embodiment, a lattice-structure intersection support 31 is used. The lattice structure is a combination of reinforcing bars, which greatly reduces the influence on the flow of concrete and prevents cavities from being generated in the concrete.
When an arch-type support is used instead of a gate-type support as the intersection support 31, it is also preferable to use a lattice structure.

Figure 4 shows the state in which the intersection support of the tunnel intersection according to an embodiment of the present invention is embedded in concrete. Figure 4(a) shows the state in which the work tunnel 20 is viewed from the main tunnel side at the tunnel intersection, and Figure 4(b) is a cross-sectional view of the work tunnel including the groove.

Referring to FIG. 4, the intersection support 31 installed in the trench 34 is filled with concrete 40. The concrete 40 is filled into the trench 34 so that the surface is the same as the inner surface of the original work pit 20. The concrete 40 may be filled by creating a formwork to match the inner surface of the work pit 20 and pouring the concrete 40, but in one embodiment, the intersection support 31 is filled by spraying shotcrete 40. In the case of a gate-type support, thick concrete 40 is formed in an arch shape below the upper beam 32 as shown in FIG. 4(b), so a support strong enough to withstand pressure from the ground 60 is formed even without installing diagonal members supporting the upper beam 32.

When an arch-shaped support is used as the intersection support 31 instead of a gate-shaped support, the groove 34 is also formed in an arch shape, so the thick arch-shaped concrete 40 is not formed as with a gate-shaped support. However, since the arch-shaped upper beam 32 itself is shaped to be resistant to pressure from the ground 60, the combination of the arch-shaped upper beam 32 and the concrete 40 forms a support strong enough to withstand pressure from the ground 60.

FIG. 5 is a diagram showing a schematic diagram of the support state of the main tunnel at the tunnel intersection according to an embodiment of the present invention.
In the section where the intersection support 31 is installed, when the main tunnel 10 is excavated, excavation is continued around the intersection support 31 while leaving it in place, and after excavation so that the upper surface of the upper beam 32 of the intersection support 31 is exposed, the main tunnel support 11 is installed. At that time, the end 12 of the main tunnel support 11 on the work tunnel 20 side is installed so that it is supported by the upper beam 32 of the intersection support 31. Since the intersection support 31 is installed so that the upper beam 32 is located at the position where the main tunnel support 11 is installed, the shape of the main tunnel support 11 is only partially shortened and is not made into a special shape that spreads outward. However, if the intersection support 31 is installed under such conditions, at least the column 33 of the intersection support 31 will be installed within the cross section of the main tunnel 10, so it will eventually need to be removed.
In one embodiment, a rock bolt 50 is driven into the upper beam 32 of the intersection support 31 toward the ground 60 to fix the upper beam 32 to the ground 60, and then the column 33 of the intersection support 31 is removed.

If the lattice-structured intersection support 31 is used, it may not be strong enough to withstand the pressure from the ground 60, or if the upper beam 32 is large and remains protruding into the cross section of the main tunnel 10, a connecting member 35 is installed on the upper beam 32 along the upper beam 32 or in the vicinity thereof along the extension direction 13 of the main tunnel 10, and the ends 12 of the main tunnel supports 11 on the working tunnel 20 side are all fixed to the connecting member 35, and then the connecting member 35 is fixed to the ground 60 with a rock bolt 50. The connecting member 35 may be provided on the upper beam 32 and in its vicinity, and furthermore, multiple connecting members may be provided at intervals near the upper beam 32. The connecting member 35 provided near the upper beam 32 is installed from the inner space side of the main tunnel 10 to the main tunnel supports 11 as shown in FIG. 5, and the multiple main tunnel supports 11 are connected and then fixed to the ground 60 with a rock bolt 50.
After fixing with the lock bolts 50, the column portions 33 of the intersection support 31 are removed. Also, the upper beam portions 32 can be removed as necessary.
The pillars 33 of the intersection support 31 will be removed after the main tunnel support 11 is installed and the upper beams 32 or the connecting members 35 of the intersection support 31 are fixed to the natural ground 60 with rock bolts 50, so the main tunnel support 11 will be supported until then. During this time, it is necessary to maintain the strength of the intersection support 31 and to be integrated with the natural ground 60. Therefore, the part between the pillars 33 of the intersection support 31 shown by the dashed line in Figure 5 and the part of the natural ground 60 to the left of that which will eventually be excavated by the two-dot chain line is left integrated until the pillars 33 of the intersection support 31 are removed. If the natural ground 60 is not strong enough, the groove 34 shown in Figure 2 may be formed to include this part, and the groove 34 may be backfilled with concrete 40 to be integrated with the natural ground 60.

FIG. 6 is a flowchart illustrating a method for excavating a tunnel intersection and constructing a support structure according to an embodiment of the present invention.
6, in the tunnel intersection excavation and shoring construction method according to the embodiment of the present invention, in paragraph S600, a groove 34 in which the intersection shoring 31 is accommodated is formed at the main tunnel connection part of the work tunnel 20. The groove 34 is formed by excavating from the inner wall of the work tunnel 20 toward the natural ground 60 with an excavator so that the upper surface of the intersection shoring 31 embedded in the groove 34 is the installation position of the main tunnel shoring 11 in the main tunnel cross section. Since the groove 34 is formed according to the shape of the intersection shoring 31, when the intersection shoring 31 is a portal shoring, the groove 34 is excavated so that the shape of the bottom surface 37 of the groove 34 is rectangular according to the outer shape, and when the intersection shoring 31 is an arch-shaped shoring, the groove 34 is excavated so that the shape of the bottom surface 37 of the groove 34 is arch-shaped according to the outer shape.

Next, in step S610, the intersection support 31 is installed in the trench 34. The intersection support 31 is preferably formed with a lattice structure to ensure embeddability of the concrete 40. In the tunnel intersection excavation and support construction method according to an embodiment of the present invention, the intersection support 31 is embedded in the ground 60 to form an underground beam support, so there is no need to dig deep or large digging into the ground to form a robust foundation structure when installing the intersection support 31.

After the intersection support 31 has been installed in the trench 34, in step S620, the intersection support 31 is filled with concrete 40. The concrete 40 may be filled by forming a formwork and then pouring the concrete 40, but in this embodiment, the concrete 40 is filled by spraying the concrete 40 to fill the trench 34.

When the intersection support 31 is completed, excavation continues at the tip of the work tunnel 20 while keeping the work tunnel cross section, then the excavation direction is changed to the extension direction 13 of the main tunnel 10, and the tunnel is widened to match the cross-sectional shape of the main tunnel 10. Following this, the main tunnel 10 is excavated and the support is installed at the normal cross section of the main tunnel 10 (step S630). The normal cross section is the cross-sectional shape of the part of the tunnel that does not include the intersection.

After the main tunnel 10 is excavated and the main tunnel supports 11 are installed a certain distance, i.e., at least the distance required to ensure the reinforcement range, the direction of excavation is reversed, and the main tunnel connection section 36 is again excavated and supports are installed at the same cross section as the normal cross section of the main tunnel 10 (step S640). After this, although not shown, excavation and installation of supports are continued along the extension direction 13 of the main tunnel at the same cross section as the normal cross section of the main tunnel 10, following the main tunnel connection section 36.

FIG. 7 is a flowchart illustrating a method for excavating a tunnel intersection and constructing a support structure according to an embodiment of the present invention.
7, in the tunnel intersection shoring processing according to the embodiment of the present invention, in step S700, the main tunnel 10 is excavated while leaving the peripheral portion of the intersection shoring 31, and excavation is performed so as to expose the upper beam portion 32 of the intersection shoring 31. At this time, the natural ground portion that integrally supports the intersection shoring 31 is left together with the intersection shoring 31 as described above.

Next, in step S710, it is determined whether or not it is necessary to use a connecting member 35 to secure the end of the main tunnel support 11 from the standpoint of strength, size, etc., and if a connecting member 35 is to be used, in step S720, the end 12 of the main tunnel support 11 on the working tunnel 20 side, which will be installed sequentially in accordance with the excavation of the main tunnel 10, is fixed to the upper beam portion 32.

Thereafter, the multiple ends 12 or nearby parts of the main tunnel support 11 on the working tunnel 20 side are connected by connecting members 35 (step S730). The connecting members 35 collectively support the ends 12 of the main tunnel support 11 on the working tunnel 20 side in the installation section of the intersection support 31, so they are made of steel and have high rigidity. The intersection support 31 is provided in a size that encompasses the cross section of the working tunnel, so it is relatively long, and therefore the connecting members 35 may be provided in several pieces in the length direction rather than as a single unit.
Furthermore, in step S740, the connecting member 35 is fixed to the natural ground 60 by the rock bolts 50. When the connecting member 35 is divided into several pieces and installed as described above, each connecting member 35 is firmly connected to each other or each connecting member 35 is fixed by the rock bolts 50.

After the end 12 of the main tunnel support 11 on the working tunnel 20 side is securely fixed, the pillar 33 of the intersection support 31 is removed in step S750. In addition, if the upper beam 32 of the connection support 31 becomes unnecessary due to the use of the connecting member 35, the upper beam 32 may be removed together with the pillar 33.

Returning to step S710, if it is determined that a connecting member 35 will not be used to fix the end of the main tunnel support 11, in step S735, the end 12 of the main tunnel support 11 on the working tunnel 20 side, which will be installed sequentially in accordance with the excavation of the main tunnel 10, is fixed to the upper beam portion 32.
Next, the upper beam portion 32 is fixed to the ground 60 with a rock bolt 50 .
Finally, in step S750, the pillar portion 33 of the intersection support 31 is removed.
In addition, if the column portion 33 or the column portion 33 and the upper beam portion 32 of the intersection support 31 are removed together in step S750 after step S740 or after step S745, although not shown in the figure, after the excavation of the main tunnel 10 in the main tunnel connection section 36 and the installation of the main tunnel support 11, it is desirable to proceed with the excavation of the main tunnel 10 and the installation of the main tunnel support 11 as is, and to remove the column portion 33 or the column portion 33 and the upper beam portion 32 together after the installation of the main tunnel support 11 in at least the reinforcement range is completed.

The above describes in detail an embodiment of the present invention with reference to the drawings, but the present invention is not limited to the above-described embodiment and can be modified in various ways without departing from the technical scope of the present invention.

REFERENCE SIGNS LIST 10 Main tunnel 11 Main tunnel support 12 End of main tunnel support 13 Extension direction of main tunnel 20 Work tunnel 21 Work tunnel support 22 Extension direction of work tunnel 30 Tunnel intersection 31 Intersection support 32 Upper beam 33 Column 34 Groove 35 Connecting member 36 Main tunnel connection section 37 Bottom surface of groove 40 Concrete 50 Rock bolt 60 Natural ground

Claims (6)

A method for excavating and constructing supports at a tunnel intersection where a main tunnel and a work tunnel intersect in a construction method for excavating a main tunnel based on the excavation of a preceding work tunnel, comprising:
After the excavation of the work tunnel has progressed to the extent that it enters the excavation area of the main tunnel, a trench of a predetermined shape is formed so that an intersection support having a shape that encompasses the work tunnel cross section at a constant width from the inner surface of the main tunnel connection part of the work tunnel toward the natural ground, and the trench is formed so that the upper surface of the intersection support to be embedded is the support installation position of the main tunnel cross section;
Installing an intersection support in the trench of the predetermined shape;
A step of burying the intersection support in the ground with concrete to construct an underground beam support;
and after excavating and supporting the main tunnel with the work tunnel cross section, excavating and supporting the main tunnel connection section again with the same cross section as the normal cross section of the main tunnel.
The step of excavating and supporting the main tunnel connection section again with the same cross section as the normal cross section of the main tunnel,
A step of connecting and fixing the end of the support of the main tunnel on the working tunnel side to the upper beam part of the support of the intersection part at the intersection part of the main tunnel, and if deemed necessary, a step of connecting the ends or the vicinity of the ends of the support of the main tunnel on the working tunnel side with connecting members;
Fixing the upper beam portion or the connecting member to the ground with a rock bolt;
A method for excavating and constructing supports at a tunnel intersection, comprising the step of removing a column portion of the support at the intersection. The tunnel intersection excavation and support construction method described in claim 1, characterized in that the intersection support is a lattice structure. The tunnel intersection excavation and support construction method described in claim 1, characterized in that the intersection support is a portal support, and the specified shape is a rectangular cross-sectional shape that matches the portal support. The tunnel intersection excavation and support construction method according to claim 1, characterized in that the step of embedding the intersection support in the ground with concrete and constructing the underground beam support comprises constructing the underground beam support by applying sprayed concrete to the intersection support. The tunnel intersection excavation and support construction method according to claim 1 or 2, characterized in that the upper beam portion of the intersection support is removed after the step of fixing the connecting member to the ground with a rock bolt. A method for excavating and constructing supports at a tunnel intersection as described in claim 1, characterized in that when the work tunnel is excavated diagonally in the horizontal direction relative to the main tunnel, the supports of the work tunnel are installed in line with the extension direction of the main tunnel at the intersection with the main tunnel, installed in a direction perpendicular to the extension direction of the work tunnel at a certain distance from the intersection, and installed so that the direction gradually changes between the extension direction of the main tunnel and the direction perpendicular to the extension direction of the work tunnel within a certain distance from the intersection.

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