JP3699885B2 - Tunnel leg reinforcement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
[0002]
The present invention relates to a tunnel leg reinforcement method, and more particularly to a steel reinforcement leg reinforcement method as an auxiliary construction method for preventing subsidence and deformation during excavation of an upper half section of a mountain tunnel.
[Prior art]
[0003]
Conventionally, in tunnel excavation in relatively soft ground such as earth and sand, soft clay, etc., in the upper half section excavation, loose load and uneven earth pressure accompanying excavation may be applied, and subsidence and displacement of the support work may occur. In order to prevent such subsidence and displacement of the support work, temporary inverting with sprayed concrete, etc. is applied to the upper half-section plate, concrete is laid on the support legs, or outside the tunnel cross section. Steel support with wing ribs that can take a large contact area at the nearest position is adopted, or lower half leg pile construction outside the lower half section tunnel is performed.
[0004]
[Problems to be solved by the invention]
However, with respect to such support measures for displacement, each of the measures described above is applied after excavation of the upper half section. For this reason, it cannot respond quickly to the deformation immediately after the support work is built. In addition, these countermeasures involve additional work immediately after excavation for each support construction work, so the process from excavation to shotcrete construction takes a lot of time, and the displacement increases during that time. There is also a problem. Moreover, in the steel support work with a wing rib and a leg pile, in order to support each support work, depending on the geological state of a lower half part, a ground support force shortage may arise. Therefore, the object of the present invention is to solve the problems of the conventional techniques described above, and in the tunnel excavation process, no additional reinforcement measures are required, and displacement can be reliably prevented immediately after excavation. The object is to provide a leg reinforcement method.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a receiving pipe by a propulsion excavator prior to excavation of the upper half section of the tunnel at a natural ground position below the legs of a steel support with a wing rib that supports the upper half section of the tunnel. Is embedded in a direction parallel to the longitudinal direction of the tunnel, and the leg portion of the steel support with a wing rib built during excavation of the upper half section of the tunnel is placed on the receiving beam pipe.
[0006]
The receiving pipe is preferably a steel pipe or a precast concrete pipe.
[0007]
At this time, the receiving beam pipe is preferably stiffened with reinforced concrete.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a method for reinforcing a leg portion of a tunnel according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 and FIG. 2 are construction explanatory views showing a series of tunnel construction steps in which a predetermined lining work is performed by excavating an earth and sand tunnel as an example using the method for reinforcing a leg portion of a tunnel of the present invention. FIG. 3 is a schematic cross-sectional view showing the steps of the tunnel leg reinforcing method and the structure of the leg reinforcing structure. FIG. 4 is a schematic perspective view showing the structure of the leg reinforcing structure.
[0009]
The construction work of the tunnel having the leg reinforcement structure will be described. First, as shown in FIGS. 1 (a), 3 (a) and 3 (b), a steel support with a wing rib built in the tunnel upper half section 1A prior to excavation of the tunnel upper half section 1A. The receiving beam pipe 10 is constructed at the lower end of the 15 leg portions 16. The receiving pipe 10 is provided so as to be positioned below the wing plate 18 that serves as a support surface of the steel support 15 with wing ribs in the cross-section outside ground 2 of the spring line (SL) of the tunnel 1. Moreover, in this Embodiment, it is embed | buried beforehand over all the lines of the longitudinal direction of the tunnel 1 (refer FIG.3 (b)).
[0010]
The installation of the receiving beam pipe 10 will be described with reference to FIG. As shown in the figure, the receiving beam 10 is buried from one side of the natural ground 2 to be excavated by the propulsion method. The receiving beam pipe 10 is an underground tubular body in which a plurality of unit steel pipes 4 continuously press-fitted are connected behind a propulsion excavator 3 having a known direction control function, and the connection between the unit steel pipes 4 is as follows. It is done by welding. The propulsion excavator 3 is excavated by a cutting mechanism (not shown) at the end by applying a reaction force to the reaction force wall 6 through a unit steel pipe 4 built in a starting pit 5 provided in the vicinity of the tunnel well 1a. It digs up so that the earth and sand in front of the machine 3 are broken down, and advances in the natural ground while discharging to the outside through the steel pipes 4, 4. As the cutting mechanism, for example, a cutter bit rotation method, an auger screw method, or the like can be adopted according to the natural ground. Although the diameter of the unit steel pipe 4 which comprises the receiving beam pipe 10 is based also on the load which acts on an upper half support arch, the steel pipe about (phi) 300-500mm is normally used. As steel pipes, pipes of various materials such as carbon steel pipes for piping (SGP) and cast iron pipes can be used in addition to general structural carbon steel pipes (STK). In order to maintain the rigidity in the extension direction, the pipe joint is in principle rigidly connected. In addition to the usual electric resistance welding, forge welding and arc welding, a connection method having a locking portion of each screw type structure can be used. In addition to the steel pipe, a precast concrete pipe can be used as the material of the receiving beam pipe 10. In this case, a collar that can rigidly join the pipe joint is provided at the pipe end. As will be described later, it is preferable to perform predetermined reinforcement and fill internal concrete or the like to enhance bending rigidity and bending tensile strength.
In addition, the propulsion excavator 3 for the propulsion method is operated by a command from the control unit C provided in the tunnel mine 1a. As a propulsion method, a method of press-fitting a tube body with a press-in jack installed in the start pit 5 into a natural ground, a method of sending out the pipe after the tip pipe while excavating and excavating the tip portion by rotating the auger screw It is preferable to set from a known propulsion method in consideration of the ground state, the diameter of the receiving pipe 10, the extension, and the like.
[0011]
Further, the propulsion excavator 3 incorporates a known direction control mechanism (not shown), and can control the state of excavation on the pit side. Prior to excavation of the upper half section of the tunnel, the tunnel excavation ground 2 The propulsion pipe (receiver pipe 10) can be embedded with high accuracy all the time (see FIG. 1B).
[0012]
Next, the upper half section of the tunnel is excavated (see FIGS. 2A and 3B). In the present embodiment, a steel support 15 with wing ribs is used for the support in the upper half section. The steel support 15 with wing ribs has a leg 16 projecting from the upper half of the tunnel to the ground 2 side, and a wing plate 18 is attached over the lower surface of the support column 17 that supports the projecting leg 16. A large ground contact area can be secured through the wing plate 18 (see FIG. 5A). Since the steel support 15 with wing ribs is schematically shown in FIG. 4, the leg portions 16 are placed on the two receiving beam pipes 10 that are previously installed in the tunnel longitudinal direction. The ground load can be borne reliably immediately after the support work is built. Further, since the receiving beam pipe 10 has a predetermined rigidity in the longitudinal direction of the tunnel, the receiving beam pipe 10 can be used as an elastic beam on the ground even when a large working earth pressure near the face acts on the support. This shows the behavior, and the applied load per unit is distributed in the longitudinal direction of the receiving beam pipe 10. In this way, the leg reinforcement method using the receiving pipe 10 can quickly cope with ground deformation and the like that occur during excavation of the upper half section of the tunnel, and the amount of displacement can be minimized.
[0013]
Following the excavation of the upper half section, excavation of the lower half 1B and invert 1C and construction of shotcrete are performed. In this case, subsidence in the upper half cross section 1A can be suppressed to a minimum by the leg reinforcing structure, so that the increase in subsidence can be suppressed slightly even in excavation of the lower half 1B and invert 1C. FIG. 2B and FIG. 3C show the completed state of the secondary lining 8.
[0014]
Each figure of FIG. 5 is the elements on larger scale which showed the leg part of the steel support work with a wing rib mounted on the receiving beam pipe 10 and the receiving beam pipe 10. FIG. As shown in FIG. 1A, a steel support 15 with wing ribs is built on the upper part of the receiving pipe 10 embedded in advance at a predetermined position so as to place the legs 16. . At this time, between the wing plate 18 on the lower surface of the support work and the receiving pipe 10, an interposing material 19 such as a camber having a bottom surface matching the outer diameter of the pipe or a pack material filled with quick setting mortar is disposed. Has been. The steel support 15 with wing ribs may be placed on the receiving beam pipe 10 while adjusting the level and angle of the wing plate 18 with the interposing material 19. As a result, the support work can be speeded up. Immediately after the steel support 15 with wing ribs is placed, the axial force transmitted from the legs of the steel support 15 with wing ribs via the interposition material 19 is reliably borne on the receiving pipe 10 side. Can be made.
[0015]
The receiving beam 10 may be slightly subsidized under the influence of the preceding settlement of the natural ground 2 behind the face, but it is covered with shotcrete behind the face and integrated with the natural ground. Even if it is exposed from the ground in the vicinity of the face, it hardly sinks. However, when the whole ground 2 is a particularly soft ground, as shown in FIG. 5 (b), a predetermined ground improvement 2B is performed from the lower half 1B side of the tunnel, thereby supporting the steel support with wing ribs. The sinking of the receiving beam pipe 10 that supports the work 15 can be reliably prevented.
[0016]
FIG. 6 is a cross-sectional view of the receiving pipe 10 showing a state in which a cylindrical reinforcing bar 21 is arranged in the pipe 10 and the inner concrete 22 is filled. In this case, any of the aforementioned steel pipes and precast concrete pipes can be used as the outer receiving beam pipe 10.
[0017]
In the above description, for example, as shown in FIG. 2 (b), the receiving pipe 10 is constructed over the entire length of the tunnel assuming that the tunnel 1 is an earth-and-sand tunnel penetrating the shallow ground 2 of the earth covering. However, in a relatively stable rock tunnel, when the part of rock quality and natural ground grade continues in the C to D class or when the fracture zone appears partially, these reinforcements It is also possible to construct a starting pit of a propulsion excavator on the side wall of the tunnel in front of an area requiring a long space, and to construct the receiving pipe 10 only in the target area. In addition, the present invention can also be effectively applied to a place where the ground such as a wellhead is unstable or a subsidence effect of a submerged underground object due to subsidence in an urban tunnel needs to be minimized.
[0018]
【The invention's effect】
As described above, according to the present invention, the ground load acting on the tunnel support of the upper half section of the tunnel constructed on the relatively soft ground is supported by the receiving pipe continuous in the longitudinal direction. Thus, there is an effect that the leg settling can be surely prevented by improving the supporting force by the continuous beam or expanding the ground contact area of the support work. In addition, the upper half-section leg can be reinforced before tunnel excavation, so that it is possible to reliably bear the ground load with the receiving pipe immediately after installing the steel support with wing rib near the face, minimizing displacement. Can be suppressed.
[Brief description of the drawings]
FIG. 1 is a construction sequence longitudinal sectional view showing one embodiment of a method for reinforcing a leg portion of a tunnel according to the present invention (part 1);
FIG. 2 is a longitudinal sectional view of a construction sequence (part 2) showing an embodiment of a method for reinforcing a leg portion of a tunnel according to the present invention.
FIG. 3 is a construction sequence cross-sectional view showing an embodiment of a tunnel leg reinforcing method according to the present invention.
FIG. 4 is a perspective view schematically showing an arrangement state of a receiving beam pipe and a steel support with a wing rib continuously built on the pipe.
FIG. 5 is a partially enlarged view showing a leg support state of a steel support with a wing rib by a receiving beam.
FIG. 6 is a cross-sectional view of a receiving beam pipe showing an example of a reinforcing state in the receiving beam pipe.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tunnel 1A Upper half cross-section 2 Ground mountain 3 Propulsion excavator 4 Unit steel pipe 10 Receiving pipe 15 Steel support 16 with a wing rib Leg 21 Reinforcement cage 22 Internal concrete

Claims (4)

Prior to excavation of the upper half-section of the tunnel, a receiving pipe was buried in the ground parallel to the longitudinal direction of the tunnel at a natural ground position below the leg of the steel support with a wing rib that supports the upper half-section of the tunnel. A method for reinforcing a leg portion of a tunnel, characterized in that the leg portion of the steel support with a wing rib built during excavation of the upper half section is placed on the receiving pipe. The tunnel leg reinforcing method according to claim 1, wherein the receiving beam pipe is a steel pipe. 2. The method for reinforcing a leg portion of a tunnel according to claim 1, wherein the receiving pipe is a precast concrete pipe. 4. The tunnel leg reinforcing method according to claim 2, wherein the receiving beam pipe is stiffened with reinforced concrete.

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