JP2631864B2 - Construction method of flat tunnel - Google Patents

Description

The present invention relates to a method for constructing a shield tunnel having a flat cross section.

<Prior Art> Conventionally, there is a method of constructing a flat tunnel of a type in which segments are assembled in a shield tunnel having a flat cross-sectional shape, a ring is formed, and then prestress is introduced to obtain ring strength of the segment.

<Problems to be Solved by the Present Invention> Compared with a tunnel having a normal circular cross section, a tunnel having a flat cross section has a disadvantage that the ring shape is easily deformed under the influence of surrounding ground pressure.

In the case of the above-described conventional technology, the ring strength of the segment until the introduction of the prestress is low due to the bolt connection or the like, so that the strength of the joint is low.

If ground pressure acts in this state, the segment cannot maintain a predetermined ring shape.

Therefore, a prestress is introduced in the shield tail where the ground pressure does not act, the ring strength of the segment is developed, and the shield machine can move forward only after the state where the ground pressure can be resisted.

As a result, the introduction of the prestress of the segment causes a decrease in the efficiency of shield excavation.

<Object of the present invention> The present invention has been made in order to solve the above-described problems. The shield excavation work and the segment prestress introduction work are independently performed, and the segment prestress introduction work is performed. An object of the present invention is to provide a method of constructing a flat tunnel capable of improving the shield excavation efficiency without being affected.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In this embodiment, as shown in FIG. 1, a case will be described in which three temporary columns 2 are installed at substantially equal intervals in the vertical direction in the ring.

<A> Segment assembly First, as in the conventional method, a ring of the segment 1 is assembled in the shield tail portion while excavating a tunnel having a flat cross-sectional shape with a shield machine.

At this time, a tapered shoe 11 is previously provided on the inner surface of the segment 1 on which the temporary support 2 to be described later is installed.

The tapered shoe 11 is a protrusion provided in parallel with the tunnel axis, and is formed in a tapered shape by gradually increasing the length of the tapered shoe 11 in the protruding direction toward the face of the tunnel.

The tapered surface of the tapered shoe 11 is processed with a low-friction material such as Teflon, so that the temporary support column 2 is easily slid.

<B> Installation of temporary strut After assembling the ring of segment 1, before introducing prestress, temporary strut 2 is installed in the ring.

The required number of temporary columns 2 is determined by calculation so as to sufficiently resist the surrounding ground pressure acting on the ring.

As shown in FIG. 2, the temporary support 2 has a structure in which grooves 21 having the same taper angle as the above-described taper shoe 11 are formed on both upper and lower end surfaces of a plate-like body or the like.

Then, the groove of the temporary support 2 is fitted to the taper shoe 11 provided on the segment 1 near the upper and lower ends of the temporary support 2 and is slid toward the face as shown in FIG. To lock.

A jack (not shown) for sliding the temporary support 2
And the like, and a stopper (not shown) or the like may be provided for fixedly installing the temporary support 2.

Further, the temporary support 2 has a pressure sensor 22 and a sink amount sensor.
It is good to attach 23.

<C> Introduction of Prestress After the installation of all the temporary columns 2 is completed, the shield machine is excavated, and the assembly of the segment 1 and the installation of the temporary columns 2 are advanced in the same procedure as described above.

At the same time as the excavation of the shield machine, a prestress introduction operation is performed in a ring of the segment 1 behind the shield machine by a known method.

<D> Removal of Temporary Props After prestress is introduced and the ring of the segment 1 exhibits a predetermined strength, all the temporary supports 2 are removed by sliding the tapered shoe 11 to the side opposite to the face.

The above operation is repeated to complete the construction of the flat tunnel.

<Operation> The present invention can sufficiently resist the surrounding ground pressure acting on the ring by the supporting force of the temporary support column 2 installed in the ring.

Therefore, even if the shield machine is dug before the prestress is introduced into the ring and the ring is left in the ground behind the shield machine, the required cross-sectional shape of the ring can be secured.

<Other Embodiments> In addition to the above embodiments, in the case of a small-diameter tunnel as shown in FIG. 3, it may be sufficient to install the temporary strut 2 at one location in the center. In a vertically long flat tunnel as shown in FIG. 4, good construction can be performed in the same manner as described above.

In addition, since the temporary support 2 is provided to support the space between the inner peripheral surfaces of the ring and resist the surrounding ground pressure, it is naturally conceivable to install the temporary support 2 in the horizontal direction.

For example, as shown in FIG. 5, there may be a case where temporary columns 2 are installed in the vertical and horizontal directions.

Further, as another structure of the temporary support 2, a structure in which the length of the temporary support 2 can be extended and contracted by a jack or the like so that the provisional support 2 can be easily installed and removed can be considered.

<Effects of the Present Invention> Since the present invention has been described above, the following effects can be expected.

<B> In the case of the conventional technology, the pre-stress is introduced into the shield tail where the ground pressure does not act, the ring strength of the segment is developed, and the shield machine moves forward only after it is in a state where it can resist the ground pressure. Because of this, the introduction of prestressing of the segments has reduced the efficiency of shield excavation.

On the other hand, the present invention is a method of supporting the inner circumference of the ring with a temporary support after assembling the segments and before introducing the prestress.

Therefore, even when the segments are assembled behind the shield tail, it is possible to sufficiently resist the surrounding ground pressure by the supporting force of the temporary support, and to perform the prestress while securing the required cross-sectional shape of the ring.

Therefore, the shield excavation work and the segment prestress introduction work can be performed independently, and the shield excavation efficiency can be improved without being affected by the segment prestress introduction work.

<B> Since the pre-stress introduction work of the segment can be performed independently behind the shield machine, sufficient work time can be taken for the pre-stress introduction work.

For this reason, it is advantageous in terms of quality control of the ring of the segment or work safety as compared with the related art.

<C> Prestress can be introduced while the required cross-sectional shape of the segment ring is maintained by the temporary support.

Therefore, it is possible to construct a tunnel having a sectional shape without deformation.

<D> Even if an abnormal load is applied to the segment ring other than when the prestress is introduced, the load can be supported by the temporary support, so that deformation of the ring can be prevented.

[Brief description of the drawings]

 Fig. 1: Explanatory drawing of one embodiment of the present invention Fig. 2: Explanatory drawing of installation of temporary supports Fig. 3-5: Explanatory drawing of other embodiments

Claims (1)

(57) [Claims] 1. A method for constructing a flat tunnel in which a segment is assembled in a shield tunnel having a flat cross-sectional shape, a ring is formed, and then a prestress is introduced. After assembling, a temporary support provided with a groove to be fitted with the tapered shoe is arranged by fitting the groove to the tapered shoe, and then a prestress is introduced, and after a predetermined ring strength is generated, the temporary support is temporarily provided. A method for constructing a flat tunnel, comprising removing a support post.