JPH03224999A - Construction of underground cavity having large section and tunnel - Google Patents

Abstract

PURPOSE:To construct a cavity having a large section in an area where the natural ground is weak in strength by a method wherein ceiling tunnels and wall surface tunnels are constructed, starting from top headings, in the direction traversing the axial line of a tunnel, and the inside of the cavity is excavated after ceilings and wall surfaces are constructed in the inside of the tunnel. CONSTITUTION:Top headings 12 in section large enough to secure stability of a tunnel are constructed first. Then ceiling tunnels 13 and wall surface tunnels 14 in sections equal to or smaller than the section of the top headings 12 are constructed, starting from the top headings 12, in the direction traversing the axial line of the tunnel. Ceilings and wall surfaces are then constructed to the inside of the tunnel and after this, the inside of the tunnel is excavated. By executing internal excavation after construction of the external wall to the tunnel, unconfined underground stress is mainly introduced to the external wall of the tunnel. Thereby a tunnel having a large section can be constructed in an area where natural ground is weak in strength.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention is applicable to the construction of branch sections of underground expressways and underground substations planned in urban areas where the ground strength is weak, such as soft rocks and earthy mountains. This paper relates to a method for constructing large-section underground cavities and tunnels that can be used for construction.

[Conventional technology] In recent years, NATM (New A
u5trian Tunneling Method
) is attracting attention. In contrast to the conventional tunnel construction method, which supports the loosening load of the ground after excavation with steel shoring and the supporting capacity of sheet piles, NATM supports the soil shogi that accompanies excavation, and spraying supports the tunnel support with concrete, etc. Based on the idea of keeping tunnel stability by effectively utilizing the strength of the ground, we construct a tunnel structure that is integrated with the ground.

[Problem to be solved by the invention] However, in the conventional NATM construction method, the earth pressure caused by excavation is shared between the tunnel support such as concrete and the ground ring, so it If the strength is weak, there are problems in that underground displacement increases or the face collapses, making construction impossible. For example, in a general tunnel, the -axial compressive strength is 0.5 kgf/c112, and the deformation coefficient is 50 kgf/cm.
2 is said to be the limit of NATM. If this were to be a tunnel with a larger cross-section, even greater ground strength would be required, making construction in urban areas almost impossible.

The present invention solves the above-mentioned problems, and aims to provide a large-section underground cavity and a method for constructing a tunnel, which can construct a large-section tunnel in an area with weak ground strength.

[Means for Solving the Problems] To this end, the method for constructing large cross-section underground cavities and tunnels of the present invention involves first constructing a preceding tunnel 12 having a cross section large enough to ensure stability of the tunnel; A ceiling tunnel 13 and a wall tunnel 14 having the same or smaller cross section as the preceding tunnel 12 are constructed in a direction transverse to the tunnel axis from the tunnel 12, a ceiling or a wall is constructed inside the tunnel, and then the interior is excavated.

Note that the ceiling tunnel 13 and wall tunnel 14 need to be constructed continuously (side walls are in contact with each other).
This is done by constructing the ceiling tunnel 13 immediately next to the ceiling tunnel 13 after constructing the ceiling tunnel 13 and the like. In addition, the construction of the wall tunnel 14 involves the underground continuous wall 1
1 or deep foundation work may be used.

Note that the numbers added to the above configurations are for comparison with the drawings to facilitate understanding, and the configurations of the present invention are not limited thereby.

[Function] In the present invention, if internal excavation is carried out after the outer walls (ceiling, wall surface) of the tunnel are constructed first, the released underground stress caused by the excavation is mainly introduced into the tunnel outer wall, which reduces the strength of the ground. It is possible to construct large-section tunnels in weak areas.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the method for constructing an underground cavity and large-section tunnel according to the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. ■−■
FIG. 4 is a cross-sectional view along the line showing an example of constructing a wall tunnel using an underground continuous wall from inside the preceding tunnel.

In the figure, 11 is an underground continuous wall, 12 is a preceding tunnel,
13 is a ceiling tunnel, 14 is a wall tunnel, 15 is a partition wall, and 16 is a reinforced wall surface.

First, the preceding tunnel 12 is constructed using a tunnel construction method such as NATM or shield. When using NATM,
Depending on the strength of the ground and the size of the preceding tunnel, special construction methods such as chemical injection or Rodinjet may also be employed.

Next, from the preceding tunnel 12, a ceiling tunnel 1 and a wall tunnel 14 are constructed in the cross-tunnel direction, and inside this, as shown in FIGS. 2 and 3, an RC or PC wall 1 is constructed.
Construct 3a. Construction of these tunnels is carried out by wall 13a
The method is to construct a tunnel on the side after construction. Note that the ceiling tunnel 13 is excavated by a mountain tunnel construction method such as NATM or by a shield method. Also,
The cross-sectional shape of the ceiling tunnel 13 may not be arched but may be constructed horizontally or downwardly convex.

In addition, for excavating the wall tunnel 14, there are methods such as applying a vertical shaft NATM, using a deep foundation, and using an excavator 17 to excavate from inside the preceding tunnel 12 using the underground continuous wall 11, as shown in FIG. is possible.

After constructing the ceiling tunnel 13 and wall tunnel 14, internal excavation is carried out. The bench method is generally used for internal excavation, but if it is necessary to reinforce the wall surface 11.14, the CD method is implemented and a strong wall surface 16 is constructed using a reverse winding method or the like.

When excavating the inside of the tunnel outer wall, as shown in the cross section on the left side of Figure 1, if it is necessary to reinforce the wall surface using the reverse winding method, etc., advance excavation near the wall surface while installing the partition wall 15 (■, ■,
■) and dig down while reinforcing it using the reverse winding method, etc., and then perform internal excavation (■, ■, ■). Note that the excavation of portions ■, ■, and ■ can also be carried out by applying the CD construction method or the CRD construction method.

〔Effect of the invention〕

As described above, according to the present invention, a ceiling tunnel and a wall tunnel are constructed from a preceding tunnel in a direction transverse to the tunnel axis, and the interior of the cavity is excavated after the ceiling and walls are constructed, so the outer wall of the tunnel is first constructed. If internal excavation is carried out after construction, the released underground stress caused by excavation will be mainly introduced into the tunnel outer wall, making it possible to construct large-section tunnels in areas where the ground strength is weak.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the method for constructing an underground cavity and large-section tunnel according to the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. ■−■
FIG. 4 is a cross-sectional view along the line showing an example of constructing a wall tunnel using an underground continuous wall from inside the preceding tunnel. 11... Underground continuous wall, 12... Leading tunnel, 13
... Ceiling tunnel, 14... Wall tunnel, 15.
...Partition wall, 16... is a reinforced wall surface. Applicant: Shimizu Corporation

Claims (1)

[Claims] (1) A method for constructing large cross-section underground cavities and tunnels, which is characterized by constructing a ceiling tunnel and a wall tunnel from a preceding tunnel in a direction transverse to the tunnel axis, and excavating the inside of the cavity after constructing the ceiling and walls. .