JP2007217911A - Construction method of underground cavity and tunnel construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently construct a branch confluent part in an underground cavity and a tunnel. <P>SOLUTION: A plurality of roof shield tunnels 6 are constructed outside a construction expected position of the underground cavity in a state of being arranged at a predetermined interval. A shield roof forepoling 3 is constructed for surrounding the construction expected position. An improved zone is formed in a joining expected position between adjacent roof shield tunnels from the inside of the respective roof shield tunnels. The underground cavity is constructed by excavating its inside by precedently constructing a series of permanent lining walls 4 for joining the mutual adjacent roof shield tunnels between the respective roof shield tunnels and in the roof shield tunnels. The underground cavity being the branch confluence part in a road tunnel is constructed by the construction method. The improved zone is formed as a freezing zone 8 by a freezing construction method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a construction method for constructing cavities and tunnels in the ground, and more particularly to a construction method suitable for application to constructing a branching junction when constructing a road tunnel having a large depth and a large cross section.

As is well known, NATM (New Austrian Tunneling Method) or shield method is a typical tunneling method for constructing a tunnel, but when constructing road tunnels in urban areas with unconsolidated ground, In order to avoid adverse effects on existing structures inside, high support performance for ground is required, and water stoppage performance and groundwater conservation performance during construction and after completion are highly required. The most common.
In recent years, various new construction methods have been proposed. For example, Patent Document 1 proposes a whale bone construction method (WBR construction method) in which an artificial ground arch is pre-constructed from a guide shaft prior to excavation of a main mine.
JP-A-11-159275

By the way, when constructing a road tunnel by the shield method, it is necessary to install a ramp tunnel in addition to the main tunnel, and join both tunnels at important points to construct a branch junction. Construction of the part is not always easy.
In other words, the main tunnel and the ramp tunnel can be constructed without hindrance while maintaining stable ground and securing water sealing by the conventional shield method, but both shield tunnels are gradually changed in cross section at the branch junction. Since it is necessary to join each other, the conventional shield method cannot be applied as it is in the construction of the branch and junction part, and it is indispensable to adopt some kind of auxiliary method.

  For this reason, it is conceivable to apply, for example, the whale skeleton method disclosed in Patent Document 1 at the time of construction of the branch junction. It is also assumed that the full support effect cannot always be obtained only by creating it above.

  In view of the above circumstances, the present invention is not only capable of efficiently constructing the branch / merging portion in tunnel construction by the shield method, but also in the large-scale underground for various uses as well as such a branch / merging portion. An object of the present invention is to provide an effective and appropriate method that can be widely applied in general when constructing a cavity.

  In the underground cavity construction method according to the first aspect of the present invention, when excavating the underground and constructing the underground cavity, a plurality of roof shield tunnels are arranged at predetermined intervals outside the planned construction position of the underground cavity. Construction of a shield roof tip receiving construction that surrounds the planned construction position is performed, and an improvement zone is formed from the inside of the roof shield tunnel to a joint planned position between adjacent roof shield tunnels. After excavating between the matching roof shield tunnels, a series of permanent lining walls that join adjacent roof shield tunnels between each roof shield tunnel and in each roof shield tunnel are pre-constructed, and then the permanent lining It is characterized by excavating the inside of the wall to complete the underground cavity.

  The tunnel construction method of the invention of claim 2 applies the construction method of the above-mentioned underground cavity to the construction of the branching / merging portion between a plurality of shield tunnels by the shield construction method, and is provided outside the branching / merging portion to be constructed. The construction of a plurality of roof shield tunnels extending along the extension direction in a state of being arranged at predetermined intervals along the outline of the branch merge section, constructing a shield roof tip receiving work surrounding the planned construction position of the branch merge section, From the inside of the roof shield tunnel, an improved zone is formed at a position where the adjacent roof shield tunnels are to be joined, and the adjacent roof shield tunnels are excavated in the improved zone, between the roof shield tunnels and in each roof shield tunnel. Next, after constructing a series of permanent lining walls that join adjacent roof shield tunnels together, Characterized in that to complete the branching and joining portion by drilling inside the factory walls.

  The invention of claim 3 applies the above tunneling method to the construction of the branch junction in the road tunnel, and advances the lamp shield tunnel ahead of the main shield tunnel so that the lamp shield tunnel A number of roof shield tunnels extending along the extension direction outside the branching junction to be constructed by digging and stopping until reaching the planned construction position at least, starting the roof shield machine from the vicinity of the tip of the lamp shield tunnel Is constructed in a state of being arranged at predetermined intervals along the outline of the branch and merge section, thereby constructing a shield roof tip receiving work that surrounds the planned construction position of the branch and merge section, and the adjacent roof from the inside of the roof shield tunnel. A freezing zone is formed at a position where the shield tunnel is to be joined, and adjacent to each other in the freezing zone Excavation between roof shield tunnels, a series of permanent lining walls that join adjacent roof shield tunnels between each roof shield tunnel and in each roof shield tunnel are pre-established, and the main shield tunnel is excavated. And the inside of the permanent lining wall is excavated to complete the branching junction.

According to the underground cavity construction method of the first aspect of the present invention, prior to excavation of the underground cavity, the construction planned position is surrounded by the shield roof tip receiving work, and an improved zone is formed at the joint position between adjacent roof shield tunnels. Then, excavation was conducted between adjacent roof shield tunnels in the improved zone, and a series of main lining walls were joined in advance between each roof shield tunnel and in each roof shield tunnel. Later, the inside of the preceding lining wall is excavated to complete the underground cavity, so that the underground cavity can be excavated and constructed safely and efficiently while ensuring sufficient support performance and water stoppage performance for the natural ground. It is possible to prevent subsidence on the surface or existing structures in the ground and conserve the surrounding groundwater.
In particular, the shield roof tip construction has a structure in which a plurality of roof shield tunnels are arranged at a predetermined interval, so that the desired rigidity as a large-scale prior construction can be sufficiently secured, and the construction is a conventional shield construction method. The number of roof shield tunnels and their arrangement can be set according to the shape and scale of the underground cavity to be constructed. You can build your work freely.
Furthermore, after improving the surrounding ground from each roof shield tunnel to form an improved zone, the improved zone is excavated and the main lining wall is pre-constructed there, so when excavating the underground cavity With the shield roof tip construction and the whole lining wall, the full support effect can be obtained.

  According to the tunnel construction method of the invention of claim 2, the above construction method is applied to the case of constructing an underground cavity as a branch merging portion of the tunnel, so that the planned position of the branch merging portion is surrounded similarly to the above. Form a shield roof tip receiving construction, form an improvement zone at the planned joining position between adjacent roof shield tunnels, form an improvement zone at the end of the shield roof tip receiving construction, and then construct the main lining wall in advance And since the inside of the branch is excavated to complete the branch and merge part, it is possible to ensure the full support performance and water stop performance, and to construct the branch and merge part safely and efficiently.

  According to the tunnel construction method of the invention of claim 3, when the above tunnel construction method is applied to the construction of the road tunnel, the lamp shield tunnel is preceded by the main shield tunnel, and the lamp shield tunnel reaches the planned construction position of the branch junction. At that time, by starting construction of the shield roof tip construction from there, it is possible to dig the main shield tunnel by parallel work with it, so the most efficient construction is possible. Moreover, since the improvement zone is formed as a freezing zone by a freezing method, the ground improvement quality is stably improved, and therefore the improvement range can be reduced, which can contribute to cost reduction and shortening of the construction period. In addition, the main lining wall is pre-constructed prior to excavation of the junction and junction, so the overall construction period and construction cost for the junction and junction can be shortened. It is most suitable to be applied to construction.

One embodiment when the tunnel construction method of the present invention is applied to construction of a road tunnel having a large depth and a large section in an urban area of unconsolidated ground will be described with reference to FIGS.
In this embodiment, as shown in FIG. 1 to FIG. 2, the main shield tunnel 1 and the lamp shield tunnel 2 are both constructed by a conventional shield method, and shields are provided in advance at the junctions of these branches. After constructing the roof tip receiving work 3 and the freezing zone (improving zone) 8, constructing the main lining wall 4 in advance, and excavating the inside to excavate the underground cavity that becomes the branching junction Is the main focus.
In the present embodiment, it is assumed that the diameter of the main shield tunnel 1 is about 16 m, for example, and the diameter of the lamp shield tunnel 2 is about 11 m, for example. In addition, as shown in FIGS. 2 to 3, the overall cross-sectional shape of the branching / merging portion in the present embodiment is from the front side (see FIG. 3A) to the front side (see FIG. 3B). In this embodiment, as described above, the main lining wall 4 that matches the cross-sectional shape of such a branching / merging portion is preliminarily constructed prior to excavation inside. It is what.

  Specifically, in the present embodiment, the lamp shield tunnel 2 is advanced ahead of the main shield tunnel 1, and when the lamp shield tunnel 2 reaches the planned construction position of the branch and merge section as shown in FIG. 2 (or The excavation is stopped (when a predetermined distance has been entered into the junction). And the roof shield machine 5 is started from the side wall part near the front-end | tip part of the lamp shield tunnel 2, and plural (16 in the illustrated example) roof shield tunnels 6 are arranged outside the planned construction position of the branch joint part. Construction is carried out in a state of being arranged at predetermined intervals along the contour, and the shield roof tip receiving work 3 is constituted by the entirety of the plurality of roof shield tunnels 6.

  The interval between the roof shield tunnels 6 and the arrangement thereof are such that the freezing zone 8 (or the improvement zone by chemical solution) formed in the subsequent process effectively supports the surrounding natural ground between adjacent roof shield tunnels 6 and the water stop function. In this embodiment, the 16 roof shield tunnels 6 are sufficiently densely arranged along the contour of the branch / merging portion as shown in FIG. Arranged.

  Each of the roof shield tunnels 6 starts the roof shield machine 5 having a small diameter (for example, about 4 m in diameter) from the tunnel side wall near the tip of the lamp shield tunnel 2 as shown in FIG. However, in this embodiment, as described above, the cross-sectional shape of the branching / merging portion is gradually reduced toward the front as described above. As shown in FIG. 2 to FIG. 3, the mutual interval between the roof shield tunnels 6 is narrowed toward the front corresponding to the cross-sectional shape of the branch and merge part, and the overall shape of the shield roof tip receiver 3 as a whole is reduced. It has a tapered shape.

When constructing each roof shield tunnel 6, prepare one or several roof shield machines 5, start them sequentially from the lamp shield tunnel 2, and when they reach the tip of the branch junction, the skin plate and cutter Assembling a new roof shield machine 5 by leaving the outer shell device such as a device and collecting only the inner device, and incorporating the collected inner device into the new outer shell device in the lamp shield tunnel 2 or on the ground yard, Just start it again. For example, in this embodiment, since all 16 roof shield tunnels 6 are provided, it is conceivable that four roof shield machines 5 are prepared and diverted four times each.
Of course, if possible, all the roof shield tunnels 6 may be simultaneously constructed by independent roof shield machines 5, or the roof shield machine 5 that has reached the tip of the branching junction is U-turned from there. It is also conceivable to continuously construct another roof shield tunnel 6 in the opposite direction.
Further, as a method for starting the roof shield machine 5 from the side wall portion of the lamp shield tunnel 2, a method for starting the shield machine from the side wall portion of the conventional shield tunnel and a T-junction between the conventional shield tunnels are used. The technology can be used as it is.

After the construction of the shield roof tip receiver 3, a freezing pipe as a ground improvement means by a freezing method is installed around it including the position where the adjacent roof shield tunnel is to be joined as shown in FIGS. Freezing zone 8 is formed. The concrete formation time of the freezing zone 8 as the natural ground improvement means does not require that the construction of all 16 roof shield tunnels 6 is completed, but the roof shield tunnels 6 are constructed adjacent to each other. If there is, it should be formed sequentially from the place where it is constructed.
As a specific construction method thereof, a long radiation freezing tube 9a is obliquely rearward (or may be obliquely forward) from the inside of each roof shield tunnel 6 toward the upper and lower portions of the roof shield tunnel 6 adjacent thereto. For example, by installing a large number of buried freezing pipes 9b in each roof shield tunnel 6 and freezing the surrounding ground with these freezing pipes, A freezing zone 8 is formed so as to cover the entire inside and outside. The thickness of the freezing zone 8 may be set in consideration of ground conditions, the distance between the roof shield tunnels 6 and the like, but for example, about 1 m is sufficient.
Placing the freezing tube 9a in an oblique direction is longer in the length per one than in the case where it is placed in the direction orthogonal to the roof shield tunnel 6, but on the other hand, the roof shield tunnel 6a. This is because the number of placements is reduced because the distance between placements is increased, resulting in improved construction efficiency and cost reduction.

Then, as shown in FIG. 5, the end portion on the near side of the shield roof tip receiving work 3 is driven into the ground mountain on the inner side from the roof shield tunnel 6 by inserting the wife frozen tube 9c into the lamp shield tunnel 2 and By freezing the periphery of the main line shield tunnel 1, the end portion freezing zone 10 is formed integrally with the surrounding freezing zone 8 at the position of the end portion on the near side (large diameter side) of the branch and merge portion.
Note that it is sufficient to form the above-mentioned freezing zone 8 also around the main shield tunnel 1 as shown in FIG. However, if necessary, the wife frozen zone 10 may be further formed by driving the wife frozen tube 9c into the same as described above.
Further, instead of forming the freezing zone 8 by the freezing method as described above, an improved zone by ground improvement by chemical solution injection may be formed. In this case, if a chemical solution injection tube is driven instead of the freezing tube good.

  As described above, since the freezing zone 8 is formed at the joint position between the adjacent roof shields at the construction position of the branch joint part, the stability of the joint position is increased and the water stoppage is secured. Therefore, the main lining wall 4 of the branching / merging portion is preliminarily constructed in such a form that the roof shield tunnels 6 are connected to each other at a planned joining position.

That is, as shown in FIG. 1, by partially removing a segment of the roof shield tunnel 6 and excavating a natural ground outside thereof, a cavity is formed between the adjacent roof shield tunnels 6. As shown in FIGS. 6 to 7, the reinforcing bars 20 are assembled in the cavities, the stiffener (frames for preventing collapse of rocks such as columns, girders, and roofs) 21 is assembled as necessary, and the mold 22 is installed. The lining body 23 is constructed in such a manner that the adjacent roof shield tunnels 6 are connected to each other by placing and filling the lining concrete inside. Note that the stiffener 21 may have the function of the mold 22 and may also be used.
Such a covering body 23 is formed between all the roof shield tunnels 6, and the same is applied to the inside of each roof shield tunnel 6 in sequence from the point where the formation of the covering body 23 between the roof shield tunnels 6 is completed. By assembling the reinforcing bars 20 and assembling the stiffening material 21 as necessary and placing the lining concrete, the similar lining bodies 23 are formed while being connected to each other. As shown in FIG. 9, a series of permanent lining walls 4 having a ring-shaped cross section rigidly connected as a whole are constructed between the roof shield tunnels 6 and in each roof shield tunnel 6.

In order to efficiently construct the above-mentioned main lining wall 4, as shown in FIG. 1, as a segment of each roof shield tunnel 6, a steel made of a main girder and a horizontal girder assembled in a frame shape. By using the steel segment 30 with the steel plate made of steel plate attached to the frame, when excavating between the roof shield tunnels 6, leaving the steel frame and removing only the steel skin plate without impairing the support effect. good.
Further, the excavation between the roof shield tunnels 6 may be performed by excavating the side from the inside of the roof shield tunnel 6, but there is a sufficient interval between the roof shield tunnels 6 on the front side of the branching junction. As shown in FIG. 1, it is possible to install a simple roof shield 35 and excavate the inside thereof by an open shield method using an excavator 36 such as a small road header.
In any case, when excavating, the adjacent roof shield tunnel 6 itself can be effectively used as a work path to efficiently transport materials and excavated soil. The construction of the work body 23 may be carried out in sequence from the completion of the service as such a work passage.

After the main lining wall 4 is preliminarily constructed as described above, the main shield tunnel 1 is dug to pass the inside of the shield roof tip receiver 3. (In addition, the main shield tunnel 1 may be dug in parallel with the construction of the shield roof tip receiver 3 and the freezing zone 8 to pass the inside of the shield roof tip receiver 3).
Then, as shown in FIG. 8, the entire inside is excavated to complete a branching junction having a large cross section. The excavation may be performed by dismantling the segments of the main shield tunnel 1 passing through the inside of the branching junction and widening the surroundings, and in that case, it is necessary to perform a fine split split. Therefore, an efficient excavation work can be performed using a large heavy machine without any trouble.
In addition, although excavating the branch junction part, the segment of each roof shield tunnel 6 will be exposed to the inner surface side, but as shown in FIG. 8, the segment is removed and the main lining wall 4 is exposed. Therefore, the inner surface of the branching / merging portion can be naturally made flat. However, it is not always necessary to do so. For example, the roof shield tunnel 6 located in the invert portion may be buried in the invert portion as it is. In that case, the entire roof shield tunnel is filled with lining concrete. Just do it.
Finally, a lining wall that becomes a wife wall is provided inside the main lining wall 4 at both ends of the branching junction, and the main shield tunnel 1 and the lamp shield tunnel 2 are provided on the front wall. If the main shield tunnel 1 is joined to the front wall, the entire lining of the branching junction is completed.

  According to the construction method of the present embodiment, the shield roof tip receiving work 3 that surrounds the planned construction position of the branching / merging portion is constructed, and the freezing zone 8 is formed from the inside of the roof shield tunnel 6 to the planned joining position between adjacent roof shield tunnels. A series of permanent installations are made by excavating between adjacent roof shield tunnels 6 in the freezing zone 8 and joining adjacent roof shield tunnels 6 between the roof shield tunnels 6 and in each roof shield tunnel 6. Since the lining wall 4 is constructed in advance, it is possible to secure sufficient support performance and water stoppage performance for the ground in the construction of the branch and junction, and prevent the complete settlement of the ground surface or existing structures in the ground, and complete groundwater Conservation can be achieved.

In particular, since the shield roof tip receiver 3 is constructed by closely arranging a plurality of roof shield tunnels 6, not only can it be made sufficiently rigid, but also the optimum cross-sectional shape corresponding to the shape of the branching junction The shield roof tip receiving work 3 can be freely and highly accurately constructed.
Further, excavation is performed between the roof shield tunnels 6 within the range of the thickness of the freezing zone 8 to construct the lining body 23, and the same lining body 23 is also integrally connected to the roof shield tunnel 6. Then, since the main lining wall 4 made by the series of lining bodies 23 is preliminarily constructed, the inside thereof is excavated, so that a full support effect can be obtained when excavating a large underground cavity such as a large branch merging section. And the water stop effect is obtained.

  Although the freezing zone 8 will eventually disappear after the tunnel is completed, a part of the roof shield tunnel 6 is left behind and functions as a part of the main lining wall 4. It is far more rational than the provisional provision.

Moreover, in this embodiment, when the lamp shield tunnel 2 precedes the main line shield tunnel 1, when the lamp shield tunnel 2 reaches the construction planned position of the branch and merge section, the shield roof tip receiving work 3 is constructed therefrom. In addition, the main shield tunnel 1 can be excavated by parallel work therewith, and in this case, the most efficient construction is possible, and the entire construction period can be sufficiently shortened.
Furthermore, since the tunnel construction method of this embodiment is basically an organic combination of the well-proven conventional shield construction method, freezing construction method, and excavation construction method, it is not only excellent in safety and reliability. In addition, it can be constructed at a relatively low cost, and can be said to be an optimum construction method especially when constructing road tunnels with large depths and large sections in urban areas.

Although the embodiment of the present invention has been described above, the above embodiment is merely a preferred example, and the present invention is not limited to the above embodiment.
For example, the above embodiment is an application example to a road tunnel having a large depth and a large cross section in an urban area of unconsolidated ground, but the tunnel construction method of the present invention has various scales, uses, and so on as long as it has a branching junction. It can be widely applied to the construction of tunnels in various forms, and various design changes can be made depending on the size and form of the branching junction in the tunnel to be constructed and considering various conditions such as the surrounding environment. Is possible.
That is, the number of roof shield tunnels 6 and the size and form of the entire shield roof tip receiving work 3 may be appropriately changed within a range in which a desired receiving effect can be secured. What is necessary is just to design optimally in the range which does not deviate from the summary of this invention also about the range of the freezing zone 8 and the wife freezing zone 10 to form, the form of the permanent lining wall 4, the construction method, and other details of each process. Of course, an appropriate auxiliary method may be adopted as necessary.

  Further, although the freezing method is adopted in the above embodiment, a chemical injection method can be adopted instead of the freezing method under a condition where the groundwater pressure is not so high, and the selection of the construction method is appropriately adopted depending on the ground conditions and the like. Is. Of course, when an improved zone is formed by injecting a chemical solution, the improved zone remains as it is, so that a function as a permanent lining wall can be expected.

Further, in the above embodiment, the roof shield machine 5 is started from the lamp shield tunnel 2, but instead, the roof shield machine 5 is started from the main line shield tunnel 1, and the others are the same as in the above embodiment. Anyway. In this case, when the main shield tunnel 1 reaches the vicinity of the widening section of the branch merge section, the roof shield machine 5 is started from the side wall portion of the main shield tunnel 1 behind the main shield tunnel 1 and the main shield tunnel 1 is left as it is. You just need to advance. Then, a shield roof tip receiving work 3 is constructed, an improvement zone is formed around the roof shield tunnel 6 or inside the end portion of the shield roof tip receiving work 3 to form a permanent lining wall 4, and the lamp shield tunnel 2 After the arrival of the shield machine, the branching junction may be excavated. Of course, the roof shield machine may be started from both the main line shield tunnel 1 and the lamp shield tunnel 2.
Furthermore, instead of starting the roof shield machine 5 from the lamp shield tunnel 2 or the main line shield tunnel 1, a start room for starting the roof shield machine 5 or starting the roof shield machine 5 from a separate shaft if possible is provided. It is also conceivable that the roof shield machine 5 is started from the ground.

Furthermore, although the said embodiment is an application example in the case of constructing the underground cavity as the branch merge part at the time of tunnel construction, the construction method of the underground cavity of this invention is not only the construction of the branch merge part of a tunnel. For example, it can be widely applied to the construction of underground cavities of a desired form and scale in the construction of various underground structures such as large underground tanks and subway station buildings.
In this case, a plurality of roof shield tunnels similar to those of the above embodiment are arranged at predetermined intervals outside the planned construction position of the underground cavity forming portion, and the shield surrounding the planned construction position of the underground cavity forming portion. Construct a roof tip receiving construction, form an improvement zone at the planned joining position between adjacent roof shield tunnels from the inside of the roof shield tunnel, and excavate the improved zone between each roof shield tunnel and within each roof shield tunnel A series of main lining walls will be installed in advance. Then, the inside of the permanent lining wall is excavated to complete the underground cavity. The shield roof tip construction, improvement zone (freezing zone), and construction method of the main lining wall are optimally designed according to the size and form of underground cavities to be constructed, ground conditions, and other conditions. It goes without saying that it should be done.

It is a figure which shows the outline | summary of the tunnel construction method which is embodiment of this invention. It is a top view of a branch junction part. It is sectional drawing of each part of a branch merge part, (a) is a IIIa-IIIa part arrow view in FIG. 2, (b) is a IIIb-IIIb part arrow view in FIG. It is an enlarged view which shows the driving | running | working condition of the freezing pipe | tube for forming a freezing zone in a branch joint part. FIG. 5 is a cross-sectional view of the end portion of the branch merge section (a view taken along the line VV in FIG. 2). It is a figure which shows the construction status of this lining wall. It is an enlarged view of the same. It is a figure which shows the state which constructed the permanent lining wall. It is an enlarged view of the same.

Explanation of symbols

1 Main Line Shield Tunnel 2 Lamp Shield Tunnel 3 Shield Roof Tip Receipt 4 Main Lined Wall 5 Roof Shield Machine 6 Roof Shield Tunnel 8 Freezing Zone (Improvement Zone)
9a Radiation freezing tube 9b Embedded freezing tube 9c Tsumabyo freezing tube 10 Tsumabyo freezing zone (improved zone)
DESCRIPTION OF SYMBOLS 20 Reinforcement 21 Stiffening material 22 Formwork 23 Covering body 30 Steel segment 35 Roof shield 36 Excavator

Claims (3)

When excavating underground and constructing underground cavities,
Construction of a plurality of roof shield tunnels arranged at predetermined intervals outside the planned construction position of the underground cavity, building a shield roof tip receiving work surrounding the planned construction position,
From the inside of the roof shield tunnel, an improved zone is formed at the junction planned position between adjacent roof shield tunnels,
After excavating between adjacent roof shield tunnels in the improved zone, a series of main lining walls that join adjacent roof shield tunnels between each roof shield tunnel and each roof shield tunnel are pre-constructed. ,
An underground cavity construction method comprising excavating the inside of the permanent lining wall to complete an underground cavity. When constructing a branching junction between multiple shield tunnels constructed by the shield method,
Shield that surrounds the planned construction position of the branch merge section by constructing a plurality of roof shield tunnels along the extension direction along the contour of the branch merge section at predetermined intervals on the outside of the branch merge section to be constructed Build a roof receiving work,
From the inside of the roof shield tunnel, an improved zone is formed at the junction planned position between adjacent roof shield tunnels,
After excavating between adjacent roof shield tunnels in the improved zone, a series of main lining walls that join adjacent roof shield tunnels between each roof shield tunnel and each roof shield tunnel are pre-constructed. ,
A tunnel construction method characterized by excavating the inside of the permanent lining wall to complete a branching junction. When constructing the branching junction between the main shield tunnel and the lamp shield tunnel constructed by the shield method,
Advance the lamp shield tunnel ahead of the main line shield tunnel, dig up and stop until the lamp shield tunnel reaches at least the planned construction position of the branching junction,
A roof shield machine is started from the vicinity of the tip of the lamp shield tunnel, and a number of roof shield tunnels along the extension direction are arranged at predetermined intervals along the outline of the branch merge section outside the branch merge section to be constructed. By constructing in a state that has been done, we built a shield roof tip receiving work that surrounds the planned construction position of the branch and merge part,
From the inside of the roof shield tunnel, a freezing zone is formed at a position where the adjacent roof shield tunnel is to be joined,
Excavating between adjacent roof shield tunnels in the freezing zone, a series of main lining walls that join adjacent roof shield tunnels between each roof shield tunnel and in each roof shield tunnel are pre-constructed,
Excavate the main shield tunnel and let it pass inside,
A tunnel construction method characterized by excavating the inside of the permanent lining wall to complete a branching junction.

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