JP5411076B2 - Tunnel construction method - Google Patents

Description

  The present invention relates to a tunnel construction method used for a NATOM method.

  Conventionally, there is JP, 2010-1633, A as a technique of such a field. In the tunnel construction method described in this publication, in order to prevent cracking of the lining concrete due to the cavity generated at the top of the lining concrete, the cushioning material is fixed over the entire surface of the shotcrete. . This cushioning material is disposed on the back surface of the waterproof sheet and is fixed to the shotcrete with concrete nails. By using the cushioning material in this way, it is difficult to transmit external force from the natural ground to the lining concrete, and it is difficult to generate cracks in the lining concrete.

JP 2010-1633 A

  However, the conventional tunnel construction method described above has a problem in that the cushioning material must be applied to the entire surface of the shotcrete, so that the workability is poor and the construction period is greatly extended.

  An object of the present invention is to provide a tunnel construction method that has good workability and does not require a significant extension of the construction period.

The present invention is a primary lining concrete formed in a natural ground by spraying concrete after excavation of the natural ground,
Rock bolts driven from primary lining concrete to natural ground,
A tarpaulin fixed to the surface of the primary lining concrete;
In a tunnel comprising concrete laid between the waterproof sheet and the formwork, and secondary lining concrete formed on the surface of the waterproof sheet,
A bag cement having a bag made of a material dissolved in alkaline water of PH of cement used for secondary lining concrete, and cement encapsulated in the bag, is fixed to the tunnel top of the waterproof sheet, Then, secondary lining concrete is cast.

  When constructing the tunnel, bleeding water collects at the top of the waterproof sheet when the secondary lining concrete is placed. When this bleeding water evaporates, a cavity is formed at this location, and this cavity tends to cause cracks in the secondary lining concrete. Since this secondary lining concrete contains more water than the primary lining concrete in order to improve fluidity, there is much generation of bleeding water and it is easy to make a cavity. Then, this invention is made | formed paying attention to bleeding water gathering on the top part of a waterproof sheet at the time of casting of secondary lining concrete, and is providing the bag cement in this place. This bag cement has a bag body made of a material that dissolves in alkaline water having a pH higher than that of cement used for secondary lining concrete, and cement enclosed in the bag body. When this occurs, the bag body of the bag cement is dissolved, whereby the cement and the bleeding water react with each other, and the portion where the bleeding water is likely to accumulate, that is, the portion where the cavity is likely to be formed, can be filled with concrete. The construction of such bag cement is not an entire construction on the waterproof sheet, but a partial construction on the top of the waterproof sheet is sufficient, so that the workability is good and it is not necessary to significantly extend the construction period. Has an effect.

In addition, the bag body is melted between the contact time with the bleeding water gathered on the top of the waterproof sheet at the time of placing the secondary lining concrete and before the hardening time of the secondary lining concrete, It is preferable that the cement in the body reacts with bleeding water.
The time when the bag is melted by the bleeding water and the cement starts to react with the bleeding water is a predetermined time after the contact between the cement and the bleeding water. This scheduled time is appropriate, for example, 2 to 3 hours when the cement for the secondary lining concrete starts to solidify and becomes semi-solidified. This is because the cement for the secondary lining concrete and the cement for the cavity are mixed. It is determined appropriately in consideration of the time that can be performed. Before the secondary lining concrete is solidified, the cement for the secondary lining concrete and the cement for the cavities are likely to mix with each other, making it difficult to form a boundary, thereby achieving a reliable cavity filling.

  According to the present invention, workability is good and it is not necessary to significantly extend the construction period.

It is sectional drawing which shows the state which installed the bag cement applied to this invention in the tunnel. FIG. 2 is a perspective view corresponding to FIG. 1. It is a perspective view which shows a bag cement. It is sectional drawing which shows the conventional tunnel.

  Hereinafter, preferred embodiments of a tunnel construction method according to the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, the tunnel 1 is constructed by a NATOM method. In this natom method, the natural ground 2 is excavated, and concrete is sprayed on the wall surface of the natural ground 2 to place primary sprayed concrete. After placing the primary shotcrete, set up a steel support in the tunnel 1 and install a wire mesh. Thereafter, concrete is sprayed onto the primary shotcrete to place the secondary shotcrete, and the primary lining concrete 3 is constructed in the tunnel 1 by the primary shotcrete and the secondary shotcrete.

  Thereafter, a lock bolt 4 is driven from the primary lining concrete 3 toward the natural ground 2 to form an arch-shaped structure around the tunnel 1. The waterproof sheet 5 is fixed to the surface of the primary lining concrete 3. After the construction of the waterproof sheet 5, a mold is set in the tunnel 1, concrete is placed between the waterproof sheet 5 and the mold, and the secondary lining concrete 6 is constructed on the surface of the waterproof sheet 5. .

  As shown in FIG. 4, when the secondary lining concrete 6 is placed in the tunnel 1 constructed by such a Natom method, bleeding water collects on the top portion 5 a of the waterproof sheet 5. When this bleeding water evaporates, a cavity S having a depth of about 5 to 20 mm is formed at this location, and the crack S is easily generated in the secondary lining concrete 6 by this cavity S. Since this secondary lining concrete 6 contains more moisture than the primary lining concrete 3 in order to improve fluidity, there is much generation of bleeding water and the cavity S is easily formed.

  Therefore, the invention is made by paying attention to the fact that bleeding water collects at the top 5a of the waterproof sheet 5 when the secondary lining concrete 6 is placed, and the bag cement 10 is disposed at this place. As shown in FIG. 3, the bag cement 10 is enclosed in a bag body 11 made of a material that dissolves in alkaline water of PH or higher of cement used for the secondary lining concrete 6, and the bag body 11. Cement 12.

  Note that sand, gravel, or the like may be included as aggregate in the cement 12. As the material of the bag body 11, hydrolytic paper made of wood pulp fiber, non-wood pulp fiber, rayon fiber, polyester fiber or the like is appropriate.

  As shown in FIGS. 1 and 2, the thickness and width of the bag cement 10 correspond to the depth and width of the cavity S, and the length of the bag cement 10 is a mold used for the construction of the secondary lining concrete 6. Corresponds to the length of the frame. Moreover, the bag cement 10 is affixed to the waterproof sheet 5 with a double-sided tape or a desired adhesive so as not to fall in the tunnel 1.

  When constructing the secondary lining concrete 6, if concrete is injected between the waterproof sheet 5 and the mold frame, bleeding water collects at the top 5 a of the waterproof sheet 5. The bag body 11 of the bag cement 10 is dissolved by the bleeding water, whereby the cement and the bleeding water react with each other, and the portion where the bleeding water is likely to accumulate, that is, the portion where the cavity S is easily formed can be filled with concrete.

  The construction of the bag cement 10 is not the entire construction on the waterproof sheet 5, but the partial construction of only the top part 5a of the waterproof sheet 5, so that the workability is good and the construction period is not significantly extended. It has an excellent effect of being able to finish.

  The time when the bag 11 is melted by the bleeding water and the cement 12 starts to react with the bleeding water is a predetermined time after the contact between the cement 12 and the bleeding water. This scheduled time is appropriate, for example, 2 to 3 hours when the cement for the secondary lining concrete 6 starts to solidify and becomes semi-solidified. This is because the secondary lining concrete cement and the cavity cement 12 are mixed. It is determined appropriately in consideration of the time that can be met. Before the secondary lining concrete 6 is solidified, the cement used for the secondary lining concrete 6 and the cement 12 used for embedding the cavities S are likely to mix with each other, making it difficult to create a boundary and achieving a reliable cavity filling. Is done.

  The melting time of the bag 11 is adjusted by adjusting the bonding force between fibers, surface treatment, and changing the thickness, but is determined based on the construction experiment using the model formwork that is performed before the tunnel construction. It is preferable to do this.

  DESCRIPTION OF SYMBOLS 1 ... Tunnel 2 ... Ground mountain 3 ... Primary lining concrete 4 ... Rock bolt 5 ... Waterproof sheet 5a ... Top part 6 ... Secondary lining concrete 10 ... Bag cement 11 ... Bag body 12 ... Cement S ... Cavity

Claims (2)

Primary lining concrete formed in the natural ground by spraying concrete after excavation of natural ground,
A rock bolt driven from the primary lining concrete toward the natural ground;
A waterproof sheet fixed to the surface of the primary lining concrete;
In a tunnel comprising concrete placed between the waterproof sheet and a formwork, and secondary lining concrete formed on the surface of the waterproof sheet,
A bag cement made of a material that is dissolved in alkaline water of PH of cement used for the secondary lining concrete, and cement encapsulated in the bag is fixed to the tunnel top of the waterproof sheet. And then laying the secondary lining concrete.   The bag body is melted between a predetermined time after contact with bleeding water gathered on the top of the waterproof sheet when the secondary lining concrete is placed, and until a time for hardening the secondary lining concrete. 2. The tunnel construction method according to claim 1, wherein the cement in the bag reacts with the bleeding water.

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