JPH06317095A - Tunnel constructing method - Google Patents

Abstract

PURPOSE:To allow constructing a railroad tunnel right under a railroad track under service by fitting by pressure a box-shaped pipe into a sheathing which is placed on each side face timbering, and performing excavation of the natural ground surrounded by upper floor plates substituted with them and the sheathing. CONSTITUTION:Sheathings 9, 9' are placed on both sides of a tunnel, and its over-part is used and provisional girder seats 14, 14' are built. A box-shaped pipe provided with a friction cut plate over the whole length of the oversurface of the opposing seats 14, 14' is fitted by pressure in a parallel condition approx. at a right angle in the tunnel. The oversurfaces of the foremost parts of upper floor plates 3. 3' fabricated in the pit 13 are put identical to the oversurface of the tail part of this pipe, and the upper floor plates 3. 3' are propelled by a jack, etc., while the friction cut plate is left in place and substituted with box-shaped pipes. The natural ground within the tunnel surrounded by these upper floor plates 3, 3' and sheathings 9, 9' is excavated, and thereby side walls 4..., intermediate walls 8, 8, lower floor plates 6, 6, etc. are built. Thus a transfer track 20 and an annex track 21 as desired are laid.

Description

Detailed Description of the Invention

[Industrial application] Traffic in large cities is extremely crowded,
Hell suffers for office workers who commute. To relieve people from this congestion, it is necessary to add railroads, construct new roads, and construct new grade separation at level crossings. However, it is difficult to obtain the track layout, which is newly necessary for the expansion / construction of this railway, in a small land like Japan,
The current situation is that construction work will not proceed late. The present invention is a new tunnel construction method that reduces the acquisition of this difficult track site, constructs a tunnel directly under a conventional railroad track while operating, and constructs an additional line at the same time.

2. Description of the Related Art Construction work for constructing a new tunnel directly under an operating track has been carried out variously to date. One of them is a tunnel by the shield method. FIG. 1 shows this cross section. It is sectional drawing which built the tunnel C in the ground B by the shield construction method with the track | line A on the ground. The disadvantage of this construction method is that the overburden D is generally required to be about 10 to 30 m in order to prevent the subsidence of the ground surface, and the construction cost of the station portion is enormous. In addition, there is an excavation method. FIG. 2 is a construction sectional view in the excavation method. Soil retaining works E are placed on both sides so as not to interfere with the track A, and construction girders F are installed to support the track. Next is track A
Excavate the bottom surface of the subway, place the subway frame G, put in the buried soil H, and remove the construction girder F. The drawback of this method is that it cannot prevent the subsidence of railway tracks.

[Problems to be Solved by the Invention] When constructing a tunnel directly below a railway line by an excavation method, the construction girder method is not taken first, the railway line is first moved to a vacant lot, and an underground structure is constructed by the excavation method. The general method is to take the method or stop the railroad business before digging. This method has drawbacks such as increasing traffic difficulty even temporarily or requiring a new track site, so if there is a method that can build a tunnel directly under the railroad track without any obstacles, The problem is solved.

[Means for Solving the Problem] FIG. 3 is a cross-sectional view when a rectangular railway tunnel is constructed immediately below a track. The railway tunnel structure can be disassembled into an upper floor slab 3, side walls 4, 4'which are ceiling portions, and a lower floor slab 6. In this figure, the underground tunnel cannot be excavated due to the track 1 on the ground, but the side wall 4,
If 4'is made of a continuous underground wall, it can be placed from above the side surface of the track. Next, the vertical shaft 13 is excavated and the upper floor slab is manufactured at the 3'position in this, and the heads of the already placed side walls 4, 4'are processed to form the girders 5, 5 ',
The upper floor slab 3'is horizontally propelled by a jack or other method and installed at the position of the upper floor slab 3 on the girders 5, 5 '. Since the tunnel ground 7 is surrounded by the upper floor slab 3, the side walls 4, 4'in three directions, it is possible to safely excavate, and if the lower floor slab 6 is placed after the excavation, the tunnel structure is completed. Details of the method for propelling the upper floor slab 3 will be described in the examples.

[Operation] The present invention is characterized in that it does not create a void in the ground 2 due to excavation, completely prevents subsidence of the ground, and excavates a tunnel. Therefore, even if the railway on the ground surface is open, it is possible to continue the construction without any problems. Therefore, a tunnel should be constructed in the same direction as the railway, just below the railway, in a place where there was little overburden, which was considered impossible until now. This is a new construction method that has achieved this.

EXAMPLE First, a box-shaped pipe used in this method will be described. Figure 4 shows a box-shaped pipe (a) is a vertical section,
(B) The figure is a cross section. A friction cut plate 11 is provided on the upper surface of the box-shaped pipe 10 over the entire length, and the tip portion 12 is bonded to the box-shaped pipe 10. In addition, joints 10 ', 10 "are provided on the sides so that they can be connected to each other.
There is. If this adhesive portion 12 is cut off, the box-shaped pipe and the friction cut plate 11 can be moved separately. FIG. 5 is a sectional view of the double-track railway tunnel to be constructed. Consider that there is a railroad track 1 on the ground surface. Generally, the ground 2 between the ground surface and the underground structure requires a space of 3 to 4 m for the buried object required in the urban area. Next, as shown in Fig. 5, the underground structure is the upper floor slab 3, the side walls 4, 4 ',
It can be divided into the intermediate wall 8, the lower floor slab 6, and the ground in the tunnel 7, 7 '. Since there is a line 1 on the ground surface, steel sheet piles and other earth retaining works 9 and 9'are first placed outside the side wall 4 so as not to interfere with this, as shown in the transverse sectional view of FIG. Next, work shafts 13 and 13 'are provided on both sides of the track, and the heads of earth retaining works 9 and 9'which are placed in parallel to the track are connected to connect the temporary girders 14 and 1'.
4'is provided. Next, the box-shaped pipe 10 equipped with the friction cut plate 11 is propelled in parallel with each other as shown in the side view of FIG. A group of box-shaped pipes having a width L, which is easy to work and is assembled into dozens of shaped pipes, is placed. As shown in FIG. 8, an upper floor slab 3 having the same width is manufactured in the vertical shaft 13 in accordance with the width L of the box-shaped pipe group, and the upper surface of the upper end of the upper floor slab 3 is matched with the upper surface of the rear end of the box-shaped pipe. The contact portion 12 between the box-shaped pipe 10 and the friction cut plate 11 is cut, and the friction cut plate 11 is fixed to the natural ground 2 so as not to move. Next, if the upper floor slab 3 is pressed out in the direction of the arrow by a jack or some other method, the box-shaped pipe 10 moves to the vertical shaft 13 'with the friction cut plate 11 left, and if this method is continued, a box of width L The group of shaped pipes 10 is squeezed out into the vertical shaft 13 ', the upper floor slab 3 is replaced with the box-shaped pipes 10 on the temporary girder seats 14 and 14', and the propulsion of the upper floor slab 3 is completed. (FIG. 9) In this case, since the friction cut plate 11 remains, the upper ground does not move. In FIG. 9, the floor slab 3 and the earth retaining work 9,
The load on the top of the tunnel is supported by 9 '.
7'is excavated, and the side walls 4, 4 ', the intermediate wall 8 and the lower floor slab 6 are placed, whereby the tunnel structure of extension L is completed. For soft ground, excavation will be easier if earth retaining works 9, 9'are used as continuous underground walls. In this way, when constructing a tunnel between a station and an intermediate part of the station, it can be constructed by the earth retaining method.
If the platform, etc. is built close to the track, a required space is required on both sides of the track. FIG. 10 is a cross-sectional view showing construction of a station portion that requires a space portion, FIG. 11 is a plan view, and FIG. 12 is a side view. This figure will be described. First of all, in order to support the upper railroad track 1, the ground 2, etc.
-1, 15-2, 15-3, 15-4 are laid from the ground by large-diameter cast-in-place piles or other methods, and temporary earth retaining works 22 are laid on both sides for tunnel excavation. Girders 16-1, 16-2, 16-3,
Place 16-4. Next, a vertical girder 17-1 is installed between the girders 16-1 and 16-2, and a vertical girder 17-2 is installed between the girders 16-3 and 16-4. Next vertical column 17
-1, 17-2, so as to be in contact with the upper surface of the friction cut plate 11, the box-shaped pipe group is press-fitted according to the example of FIGS. By replacing it with 3 ', the upper floor slab 3 is erected and 7,7' in the tunnel is excavated while constructing the support work and the intermediate pillar 1
8. If the lower floor slab 6 is placed and the temporary earth retaining work is removed, an extension L tunnel can be constructed. By repeating this method, a tunnel with the required extension can be constructed. In addition,
Even if the distance between stations is set to 2 km even in the construction of the middle part, there will be a lot of construction loss if the whole area is constructed by the earth retaining method. If the extension is long, transportation of earth and sand and materials will be costly in proportion to the distance, so it is advisable to install a shaft in the middle. For this reason, if a station-type support pillar is used, an entrance can be created on the side of the tunnel at the required position, and a vertical shaft can be installed by using this. Although the construction of the double-track railway tunnel has been described as an example in the embodiments, the underground construction of the railroad is often caused by the necessity of additional line construction. FIG. 13 is a sectional view in the case of double-track construction in the middle part. If the earth retaining works 9 and 9'are made long and a two-layer tunnel is constructed, four lines can be constructed at the same time. 14
In the construction example of the station section, if the supporting pillars 15-1, 15-3, etc. are driven in a length of two layers, a tunnel for four lines can be constructed at the same time.

Industrial Applicability The present invention is a new construction method that realizes a construction work which is considered impossible by excavating a tunnel just below a railroad track which is in operation and relocating the railroad. The main features of this feature are that it is possible to use all the existing railway land, so there is no need to acquire new land. In the shield method used in the non-cutting method, mortar injection is used to prevent voids generated outside the segment.
In the case of soft ground, it often subsides before the injection of mortar and cracks occur in the upper ground. Since this method replaces the upper floor slab and the box-shaped pipe, no void is created. In ordinary tunnel excavation, concrete placement at the top of the arch winding is the weakest point. There is a concern about leaving voids in the ground and problems with the quality of concrete. In this method, the tunnel floor slab is replaced by the floor slab that was manufactured with great care outside the light, that is, outside the tunnel, so the quality is good and the safety is high. Even in the station area, support pillars can be used for flexible planning, and if two-layer construction is used, the most desirable feature is the additional construction of tracks at the same time.
In addition, underground burial of railways on the ground has a large traffic benefit by removing noise from the railways, preventing accidents due to abolition of railroad crossings, and converting railway land to roads, and construction costs are low compared to other construction methods. It becomes cheaper. Considering these, the contribution of the present invention to society is great.

[Brief description of drawings]

[Fig. 1] Cross section of subway line by shield method

[Fig. 2] Construction cross-section by the open-cut method

FIG. 3 is a sectional view of a rectangular tunnel structure.

FIG. 4 (a) Vertical sectional view of box-shaped pipe

FIG. 4 (b) Box-shaped pipe cross-sectional view

[Fig. 5] Cross section of double-track railway tunnel

[Fig. 6] Cross section of earth retaining work and box pipe placement

[Fig.7] Side view of earth retaining work and box-shaped pipe placement

[Fig. 8] Diagram of replacement method for box-shaped pipe and upper deck

[Figure 9] Completion drawing of the construction of the intermediate subway tunnel

[Figure 10] Cross-section of the construction method for the station

[Figure 11] Plan view of the construction method for the station

[Fig. 12] Side view of construction method for station

[Fig. 13] Cross section of double-track construction in the middle section

[Figure 14] Station section double track construction cross section

[Explanation of symbols]

A …………… Railroad track B …………… Ground C …………… Shield tunnel D …………… Overburden E …………… Soil retaining work F …………… Construction girder H …………… Buried soil 1 ……………… Railroad track 2 ……………
Chisan 3 3 '……………… Upper floor version 4, 4' ……
… Side wall 5, 5 '……… Girder 6 ……
………… Understory version 7 ……………… Ground inside the tunnel 8 ………………
Middle wall 9,9 '………… Earth retaining work 10 ……
Box pipe 10 ', 10 "... Box pipe side joint 11 ... Friction cut plate 12 ......... Friction cut plate and box pipe joint 13, 13' ... Vertical shaft 14, 14 '......... Temporary Girder 15-1,1
5-2 ... Support pillar 15-3, 15-4 ... Support pillar 16-1, 16-2 ... Support pillar, girder seat 16-3, 16-4 ... Support pillar, girder seat 17-1, 1
7-2… Vertical girder 18 ………… Center pillar 19 ………
・ ・ ・ Boarding area 20 ………… Transfer line 21 ………
・ ・ ・ Extension track L ……………… 1 extension of construction 22 ………
・ ・ ・ Temporary earth retaining work

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 10, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

[Fig. 1] Cross section of subway line by shield method

[Fig. 2] Construction cross-section by the open-cut method

FIG. 3 is a sectional view of a rectangular tunnel structure.

[FIG. 4] (a) Vertical sectional view of box-shaped pipe (b) Horizontal sectional view of box-shaped pipe

[Fig. 5] Cross section of double-track railway tunnel

[Fig. 6] Cross section of earth retaining work and box pipe placement

[Fig.7] Side view of earth retaining work and box-shaped pipe placement

[Fig. 8] Diagram of replacement method for box-shaped pipe and upper deck

[Figure 9] Completion drawing of the construction of the intermediate subway tunnel

[Figure 10] Cross-section of the construction method for the station

[Figure 11] Plan view of the construction method for the station

[Fig. 12] Side view of construction method for station

[Fig. 13] Cross section of double-track construction in the middle section

[Figure 14] Station section double track construction cross section

[Procedure amendment]

[Submission date] May 18, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

[Industrial application] Traffic in large cities is extremely crowded,
Hell suffers for office workers who commute. To relieve people from this congestion, it is necessary to add railroads, construct new roads, and construct new grade separation at level crossings. However, it is difficult to obtain the track layout, which is newly necessary for the expansion / construction of this railway, in a small land like Japan,
The current situation is that construction work will not proceed late. The present invention is a new tunnel construction method that reduces the acquisition of this difficult track site, constructs a tunnel directly under a conventional railroad track while operating, and constructs an additional line at the same time.

[0002]

2. Description of the Related Art Construction work for constructing a new tunnel directly under an operating track has been carried out variously to date. One of them is a tunnel by the shield method. FIG. 1 shows this cross section. Is a sectional view of the construction of the tunnel C by shield method in line A is land mountain B on the ground. The disadvantage of this construction method is that the overburden D is generally required to be about 10 to 30 m in order to prevent the subsidence of the ground surface, and the construction cost of the station portion is enormous. In addition, there is an excavation method. FIG. 2 is a construction sectional view in the excavation method. Soil retaining works E are placed on both sides so as not to interfere with the track A, and construction girders F are installed to support the track. Next is track A
Excavate the bottom surface of the subway, place the subway frame G, put in the buried soil H, and remove the construction girder F. The drawback of this method is that it cannot prevent the subsidence of railway tracks.

[0003]

[Problems to be Solved by the Invention] When constructing a tunnel directly below a railway line by an excavation method, the construction girder method is not taken first, the railway line is first moved to a vacant lot, and an underground structure is constructed by the excavation method. The general method is to take the method or stop the railroad business before digging. This method has drawbacks such as increasing traffic difficulty even temporarily or requiring a new track site, so if there is a method that can build a tunnel directly under the railroad track without any obstacles, The problem is solved.

[0004]

[Means for Solving the Problem] FIG. 3 is a cross-sectional view when a rectangular railway tunnel is constructed immediately below a track. The railway tunnel structure can be disassembled into an upper floor slab 3, side walls 4, 4'which are ceiling portions, and a lower floor slab 6. In this figure, the underground tunnel cannot be excavated due to the track 1 on the ground, but the side wall 4,
If 4'is made of a continuous underground wall, it can be placed from above the side surface of the track. Next, the vertical shaft 13 is excavated and the upper floor slab is manufactured at the 3'position in this, and the heads of the already placed side walls 4, 4'are processed to form the girders 5, 5 ',
The upper floor slab 3'is horizontally propelled by a jack or other method and installed at the position of the upper floor slab 3 on the girders 5, 5 '. Since the tunnel ground 7 is surrounded by the upper floor slab 3, the side walls 4, 4'in three directions, it is possible to safely excavate, and if the lower floor slab 6 is placed after the excavation, the tunnel structure is completed. Details of the method for propelling the upper floor slab 3 will be described in the examples.

[0005]

[Operation] This invention is characterized by excavating the inside of the tunnel by completely preventing subsidence of the ground without forming a void in the ground 2 due to excavation. Therefore, even if the railway on the ground surface is open, it is possible to continue the construction without any problems. Therefore, a tunnel should be constructed in the same direction as the railway, just below the railway, in a place where there was little overburden, which was considered impossible until now. This is a new construction method that has achieved this.

[0006]

EXAMPLE First, a box-shaped pipe used in this method will be described. Figure 4 shows a box-shaped pipe (a) is a vertical section,
(B) The figure is a cross section. A friction cut plate 11 is provided on the upper surface of the box-shaped pipe 10 over the entire length, and the tip portion 12 is bonded to the box-shaped pipe 10. In addition, joints 10 ', 10 "are provided on the sides so that they can be connected to each other.
There is. The box-shaped pipe and the friction cut plate 11 can be moved separately by separating the adhesive portion 12.
FIG. 5 is a sectional view of the double-track railway tunnel to be constructed. Consider that there is a railroad track 1 on the ground surface. Generally, the ground 2 between the ground surface and the underground structure requires a space of 3 to 4 m for the buried object required in the urban area. Next, as shown in Fig. 5, the underground structure can be divided into an upper floor slab 3, side walls 4, 4 ', an intermediate wall 8, a lower floor slab 6, and a tunnel inner ground 7, 7'.
Since there is a line 1 on the ground surface, steel sheet piles and other earth retaining works 9 and 9'are first placed outside the side wall 4 so as not to interfere with this, as shown in the transverse sectional view of FIG. Next, working shafts 13 and 13 'are provided on both sides of the track, and heads of earth retaining works 9 and 9'which are cast in parallel to the track are connected to provide temporary girders 14 and 14'. Next, the box-shaped pipe 10 equipped with the friction cut plate 11 is propelled in parallel with each other as shown in the side view of FIG. A group of box-shaped pipes having a width L, which are easy to work and are assembled into several dozen shaped pipes, are placed.

As shown in FIG . 8, an upper floor slab 3 having the same width is manufactured in the vertical shaft 13 in accordance with the width L of the box-shaped pipe group.
The upper surface of the tip end of the box-shaped pipe is brought into contact with the upper surface of the rear end of the box-shaped pipe, and the adhesive portion 12 between the box-shaped pipe 10 and the friction cut plate 11 is cut to prevent the friction cut plate 11 from moving. Fixed to. Next, if the upper floor slab 3 is pressed out in the direction of the arrow by using a jack or some other method, the box-shaped pipe 10 is left in the vertical shaft 1 with the friction cut plate 11 left.
Moving to 3'and continuing this method, the group of box-shaped pipes 10 having a width L is squeezed out to the shaft 13 ', and the upper deck 3 is fixed to the temporary girder 14,
14 'is replaced by the box-shaped pipe 10, and the propulsion of the upper deck 3 is completed. (FIG. 9) In this case, since the friction cut plate 11 remains, the upper ground does not move.

[0008] 'Because the load of the tunnel top by being supported, earth retaining Engineering 9,9' top floor plate 3 and the earth retaining Engineering 9,9 9 within the tunnel while putting支保Engineering in natural ground 7, 7 '
By excavating, and placing the side walls 4, 4 ', the intermediate wall 8 and the lower floor slab 6, the tunnel structure of extension L is completed. For soft ground, excavation will be easier if earth retaining works 9, 9'are used as continuous underground walls. In this way, when constructing a tunnel between a station and a station, the earth retaining method can be used. However, if the passage, platform, etc. are built close to the railway like the station, the space required on both sides of the railway is required. is necessary.

FIG . 10 is a cross-sectional view showing construction of a station portion that requires a space portion, FIG. 11 is a plan view, and FIG. 12 is a side view. This figure will be described. Railway line 1 of the upper, first support columns 15-1 and 15-2 in order to support the land mountain 2, and the like,
15-3 and 15-4 were laid from the ground using large-diameter cast-in-place piles or other methods, and temporary earth retaining work for tunnel excavation 22
Are installed on both sides to provide vertical shafts 13 and 13 ', and girder seats 16-1, 16-2, 16-3 and 16-4 are installed on the supporting column heads. Next, a vertical girder 17-1 is installed between the girders 16-1 and 16-2, and a vertical girder 17-2 is installed between the girders 16-3 and 16-4.
Erection. Next, the vertical columns 17-1, 17-2,
The box-shaped pipes fitted with friction cut plates 11 are press-fitted according to the examples of FIGS. 6 and 7 so as to be in contact with the upper surfaces of the upper floors, and then replaced with the upper floor slab 3 ′ manufactured in the vertical shaft 13 A tunnel of extension L can be constructed by erection of the slab 3, excavating 7, 7'in the tunnel while supporting construction, placing the intermediate pillar 18, the lower floor slab 6 and removing the temporary earth retaining work. By repeating this method, a tunnel with the required extension can be constructed.

[0010] It should be noted, and even if the 2Km between stations in the construction of the intermediate portion, a large loss on the construction work if the entire interval and earth retaining application method. If the extension is long, transportation of earth and sand and materials will be costly in proportion to the distance, so it is advisable to install a shaft in the middle. For this reason, if a station-type support pillar is used, an entrance can be created on the side of the tunnel at the required position, and a vertical shaft can be installed by using this. Although the construction of the double-track railway tunnel has been described as an example in the embodiments, the underground construction of the railroad is often caused by the necessity of additional line construction. FIG. 13 is a sectional view in the case of double-track construction in the middle part. If the earth retaining works 9 and 9'are made long and a two-layer tunnel is constructed, four lines can be constructed at the same time. FIG. 14 shows an example of construction of a station section, supporting pillars 15-1,
If 15-3 etc. are cast in a length of two layers, a tunnel for four lines can be constructed at the same time.

[0011]

Industrial Applicability The present invention is a new construction method that realizes a construction work which is considered impossible by excavating a tunnel just below a railroad track which is in operation and relocating the railroad. The main features of this feature are that it is possible to use all the existing railway land, so there is no need to acquire new land. In the shield method used in the non-cutting method, mortar injection is used to prevent voids generated outside the segment.
In the case of soft ground, it often subsides before the injection of mortar and cracks occur in the upper ground. Since this method replaces the upper floor slab and the box-shaped pipe, no void is created. In ordinary tunnel excavation, concrete placement at the top of the arch winding is the weakest point. There is a concern about leaving voids in the ground and problems with the quality of concrete. In this method, the tunnel floor slab is replaced by the floor slab that was manufactured with great care outside the light, that is, outside the tunnel, so the quality is good and the safety is high. Even in the station area, support pillars can be used for flexible planning, and if two-layer construction is used, the most desirable feature is the additional construction of tracks at the same time.
In addition, underground burial of railways on the ground has a large traffic benefit by removing noise from the railways, preventing accidents due to abolition of railroad crossings, and converting railway land to roads, and construction costs are low compared to other construction methods. It becomes cheaper. Considering these, the contribution of the present invention to society is great.

Claims (2)

[Claims] 1. A box in which earth retaining works are placed on both sides of a tunnel, a temporary girder seat is constructed using the upper portion of the earth retaining work, and friction cut materials are arranged over the entire length on the upper surface of the opposing temporary girder seat. Shaped pipes are press-fitted into the tunnel at a substantially right angle and in parallel, and the upper surface of the upper deck produced in the vertical shaft is aligned with the upper surface of the rear end of the box-shaped pipe, and the friction cut material is left in the jack. In addition, promote the upper deck,
Replace the box-shaped pipe group with the upper deck, excavate the ground in the tunnel surrounded by the upper deck and earth retaining works, and place sidewalls, intermediate walls, lower deck, etc. to build a tunnel. Method 2. Support pillars are placed on both sides of the tunnel at required intervals, temporary earth retaining work required for excavation is also installed at the same time, and a girder seat is built on the head of the support pillar, and vertical girders are installed between the girder seats. A box-shaped pipe, in which a girder was erected and friction cut material was placed over the entire length of the opposing vertical girders, was press-fitted into the tunnel at a substantially right angle and in parallel, and the upper surface of the tip of the upper deck produced in the vertical shaft was Match the upper surface of the rear end of the box-shaped pipe and propel the upper deck with a jack or the like while leaving the friction cut material, replace the box-shaped pipe group with the upper deck, and enclose the upper deck with supporting columns and temporary earth retaining works. Tunnel excavation method in which the ground is excavated and the side walls, intermediate columns, and lower deck slabs are placed to form the tunnel.