JP2016169516A - Back-filling material for segment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back-filling material for a segment, which makes viscosity and strength against freezing soil proper.SOLUTION: A back-filling material 1 for a segment is arranged between freezing soil 2 and the segment 3 from an injection pipe and the like provided in the segment 3 provided in a rear part of a shield machine. The back-filling material, in which cement, such a quantity of water as to be capable of securing viscosity enabling squeeze pumping by a pump, urea, and sodium silicate are blended together, presents a gel state, and presents the gel state by being further blended with sodium silicate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a segment backfill material.

  In general, in shield tunnel construction, a freezing method may be employed as a protective work for the underground widening portion or the like. In the freezing method, a coolant is supplied into the ground to freeze the underground water to create a frozen ground, thereby improving the water stoppage of the ground.

The segment constructed behind the shield excavator is subjected to freezing expansion pressure from the frozen ground. For this reason, a technique for reinforcing a segment or reducing a freezing expansion pressure by injecting a backfilling material between the frozen ground and the segment is known (see Patent Document 1 below).
As such a backfilling material, for example, a mixture of cement, water, an AE water reducing agent, and a thickener so that the water / cement ratio is 30 to 60% is used. .

Japanese Patent No. 2806213

  However, the backfill material as described in the above-mentioned Patent Document 1 has the strength of the backfill material because the surplus moisture generated by the hydration reaction of the cement freezes in the shape of an ice lens on a frozen ground of 0 ° C. or lower. There is a problem that it decreases. On the other hand, lowering the water / cement ratio to reduce excess water, which is a cause of strength reduction, increases the viscosity of the backfilling material, which makes it difficult to pump with the backfilling material. There is a problem.

  Accordingly, the present invention has been made in view of the above circumstances, and provides a segment backing material having a high strength against frozen soil while ensuring an appropriate viscosity.

In order to achieve the above object, the present invention employs the following means.
That is, the segment backing material according to the present invention is a backing material disposed between the frozen soil and the segment, and is characterized by mixing cement, water, and urea.

  The segment backing material of the present invention is disposed between the frozen soil and the segment, and is configured by mixing cement, water, and urea. Therefore, as compared with a general backfilling material to which no urea is added, in the present invention, by adding urea, the volume of water corresponding to the added urea can be reduced. That is, the strength of the backfilling material can be increased by replacing part of the water with urea. In addition, even when urea is added, the viscosity coefficient hardly changes compared to the case where urea is not added, so that appropriate viscosity can be ensured.

ただし、
Ｗ１：尿素を配合しない場合の裏込め材における水の容積
Ｃ１：セメントの容積
Ｗ２：本発明の裏込め材において、ポンプでの圧送可能な粘性を確保できる水の最低限の容積
Ｂ２：本発明の裏込め材における尿素の容積 In the segment backfill material according to the present invention, it is preferable that the volume of the urea is set so as to satisfy the following conditional expression (1).

However,
W1: Volume of water in the backfilling material when urea is not blended C1: Cement volume W2: Minimum volume of water B2 that can ensure viscosity that can be pumped by the pump in the backfilling material of the present invention B2: Present invention Volume of urea in backfill materials

  In the backfill material of the segment configured in this way, the volume of water is set to an amount that can ensure viscosity that can be pumped by the pump. Therefore, it is possible to increase the strength while securing viscosity by replacing a part of the general backfilling material to which urea is not added with urea.

  Moreover, it is preferable that the backfill material of the segment which concerns on this invention is further mix | blended with sodium silicate, and exhibits a gel form.

  By blending sodium silicate into the backfill material of the segment thus configured, the backfill material can be held in a gel state for a predetermined time immediately after injection, and the solidification time can be shortened. The workability can be improved.

  According to the segment backing material according to the present invention, it is possible to increase the strength against the frozen soil while ensuring an appropriate viscosity.

It is a figure which shows arrangement | positioning of the backfilling material of the segment which concerns on one Embodiment of this invention.

A segment backfill material according to an embodiment of the present invention will be described.
As shown in FIG. 1, a backfill material (segment backfill material) 1 is a gap S between a frozen soil 2 and a segment 3 constructed behind a shield machine (not shown; the same applies hereinafter). It is arranged by being injected. The backfill material 1 is injected into the gap S from an injection pipe (not shown) provided in the segment 3 provided at the rear of the shield machine.

The backfill material 1 is configured by mixing cement, water, and urea.
The amount of urea to be blended is calculated by the following method.
First, assuming that urea is not blended, the water / cement ratio that achieves the required strength is determined to be a predetermined value of, for example, 30 to 60%. Based on this, the amount of water (volume W1) and the amount of cement (volume C1) are respectively calculated.
Next, a minimum amount of water (volume W2) that can ensure viscosity that can be pumped by the pump is determined. The amount of cement in the backfill material 1 (containing urea) of the present embodiment is defined as the above (volume C1), and the amount of water is defined as the above (volume W2). Then, as shown in the following formula (2), the volume ratio of the sum of the water amount (volume W2) and the urea amount (volume B2) to the cement amount (volume C1) is (volume W1) to (volume C1). The urea amount (volume B2) to be blended is determined so as to be substantially the same as the volume ratio.

(Examples and comparative examples)
Table 1 shows an example of the blending example of the backfill material 1 shown above and a blending example of the backfilling material not containing urea as a comparative example.

As shown in Table 1, a typical back-filling material containing no urea, water 165 kg / ^{m 3,} cement 352 kg / ^{m 3,} fine aggregates 766kg / ^{m 3,} it is blended with coarse aggregate 1037kg / ^{m 3} where, back-filling material according to an embodiment of the present invention, e.g., water 150 kg / ^{m 3,} cement 352 kg / ^{m 3,} urea 20 kg / ^{m 3,} fine aggregates 766kg / ^{m 3,} with coarse aggregate 1037kg / ^{m 3} It is blended. Thus, the amount of water can be reduced by adding urea.

  Further, in order to shorten the solidification time or make the gel immediately after injection, sodium silicate having a concentration of 50% or less may be injected while mixing at the inlet (not shown) of the injection tube.

The segment back-filling material 1 configured as described above is disposed between the frozen soil 2 and the segment 3, and is configured by mixing cement, water, and urea. The volume of water is set to an amount that can secure viscosity that can be pumped by a pump. Therefore, as compared with a general backfilling material to which no urea is added, in the present invention, by adding urea, the volume of water corresponding to the added urea can be reduced. That is, the strength of the backfilling material 1 can be increased by replacing part of the water with urea. Further, even when urea is added, the viscosity coefficient hardly changes as compared with the case where urea is not added, so that a good viscosity can be maintained.
In general, when a high-performance AE water reducing agent is used instead of the AE water reducing agent, the amount of water to be blended can be reduced by about 7%, but the use of urea has a further water reducing effect.

  Moreover, since the segment back-filling material 1 in which sodium silicate is blended is gel-like for a predetermined time immediately after injection, the solidification time can be shortened and the workability can be improved.

  The above-described embodiment is an example, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

1 ... Backfilling material (segment backing material)
2 ... Frozen soil 3 ... Segment

Claims (3)

Backing material placed between the frozen soil and the segment,
A segment backing material characterized by a mixture of cement, water and urea. In the segment backing material according to claim 1,
The segment backfill material, wherein the volume of urea is set so as to satisfy the following conditional expression (1).

However,
W1: Volume of water in the backfilling material when urea is not blended C1: Cement volume W2: Minimum volume of water B2 that can ensure viscosity that can be pumped by the pump in the backfilling material of the present invention B2: Present invention Volume of urea in backfill materials   The segment back-filling material according to claim 1 or 2, wherein sodium silicate is further blended to form a gel.

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