JP2001198915A - Method for manufacturing sprayed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To largely decrease an amount of splashes. SOLUTION: In a manufacturing method, cemente c, fine aggregate s, coarse aggregate S and mixing water W which are components of concrete are prepared according to the proportional ratio, the mixing water W is divided into two parts of primary mixing water W1 and secondary mixing water W2, and they are primarily kneaded. The primary kneading is carried out by adding the mixing water W1 to the cement c and the fine aggregate s. When the primary kneading is ended, then secondary kneading is carried out. In the secondary kneading, the coarse aggregate S, the secondary mixing water W2 and starch based thickener X are additively casted into a mixture containing the cement c and the fine aggregate s which are kneaded in the primary kneading, and the secondary kneading is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing shotcrete to be sprayed on a tunnel excavation surface.

[0002]

2. Description of the Related Art In recent years, the NATM method using rock bolts and shotcrete as a support has become the mainstream for tunnel construction. In this type of construction method, concrete is sprayed on the excavated wall at an early stage in order to restrain the excavated ground from loosening.

[0003] However, in the spraying of concrete, it is a great technical problem to reduce the increase in the amount of rebound during spraying and to reduce the deterioration of the working environment due to the generation of dust accompanying the spraying. Conventional shotcrete has the following problems.

[0004]

That is, the conventional shotcrete is prepared by adding a cellulosic or acrylic thickener during the production of concrete in order to reduce the rebound during spraying. By increasing the viscosity of the concrete, the rebound was reduced.

However, even if such a thickener is added, it is difficult to sufficiently reduce the amount of rebound, and the effect of improving the working environment is insufficient.

[0006] The present invention has been made in view of such a conventional problem, and has been made to sufficiently reduce the amount of rebound,
It is an object of the present invention to provide a method for producing sprayed concrete capable of obtaining a remarkable working environment improvement effect.

[0007]

In order to achieve the above object, the present invention relates to a method for producing concrete to be sprayed on a wall of a tunnel excavation, wherein the mixing water for the concrete is mixed twice with primary and secondary mixing water. And kneading with the secondary kneading water, a starch-based thickener was added. According to the sprayed concrete manufacturing method configured as described above, first,
Concrete kneading water is divided into primary and secondary kneading water twice and kneaded, so at the time of primary kneading, a cement film is formed on the surface of fine aggregate to reduce aggregate separation. Therefore, the workability of concrete is improved. In addition, when kneading with secondary kneading water, since a starch-based thickener is added, the viscosity of the shotcrete increases, the amount of rebound when sprayed is reduced, and the construction time can be shortened In addition, the working environment can be significantly improved. The starch-based thickener can be added in an amount of about 2% by weight based on the total weight of the primary and secondary mixing waters. By adding a starch-based thickener in such an amount, the above-described effects can be exerted without impairing economic efficiency.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG.
FIG. 2 is an explanatory view showing a manufacturing process of the shotcrete production method according to one embodiment of the present invention over time.

In the method for manufacturing shotcrete shown in FIG. 1, first, cement c, fine aggregate s, coarse aggregate S, which are constituent materials of concrete, are set according to a set mixing ratio.
Kneading water W is prepared, and kneading water W is divided into two parts, primary kneading water W1 and secondary kneading water W2,
Primary kneading is performed.

The primary kneading is performed by adding the primary kneading water W1 to the cement c and the fine aggregate s. When the primary kneading is completed, the secondary kneading is performed next. In secondary kneading,
This is performed by adding the coarse aggregate S, the secondary mixing water W2, and the starch-based thickener X to a mixture containing the cement c and the fine aggregate s kneaded in the primary kneading.

Then, by performing kneading for a predetermined time, the sprayed concrete C of this embodiment is manufactured. Shotcrete C produced in this manner is, for example,
In the vicinity of the spray nozzle, a liquid or powdery quick setting agent is added to the excavation wall of the tunnel by using compressed air while being sprayed.

[0012] The sprayed concrete produced in this manner is first kneaded by mixing the kneading water of the concrete twice into primary and secondary kneading waters W1 and W2. Since the cement film is formed on the surface of the fine aggregate s to reduce the separation of the aggregate, the workability of the concrete is improved.

Further, when kneading with the secondary kneading water W2, the starch-based thickener X is added, so that the viscosity of the shotcrete C is increased and the amount of rebound when sprayed is reduced. The time can be reduced, and the working environment can be significantly improved.

The following table shows that shotcrete (Example 1) was manufactured by the manufacturing method according to the present invention in order to confirm the above-mentioned effects of the present invention.
Shotcrete with two mixing ratios (Comparative Examples 1 and 2) were produced.

[0015]

【table】

In Example 1, a starch-based thickener (Elfresh K-200, trade name, manufactured by Nisse Chemical Co., Ltd.) was used as a thickener, and the weight ratio of the thickener to water was 2.0%.
% Was added.

In Comparative Example 1, a cellulose-based thickener (Natom Clean, trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was used, and 0.36% by weight of water was added.

In Comparative Example 2, no thickener was added. In the production of each shotcrete of Example 1 and Comparative Examples 1 and 2, kneading water was kneaded in two divided portions, and a thickener was added during secondary kneading.

Obtained. The same quick-setting agent was added in the same amount to each of the shotcrete of Example 1 and Comparative Examples 1 and 2, and the shotgun was sprayed on the excavated surface of the tunnel, and the rebound amount (rebound amount) at that time was measured.

As a result, the rebound amount of the first embodiment is 1
0.7%, the rebound amount of Comparative Example 1 was 15.3%, and the rebound amount of Comparative Example 2 was 20.6%.

As is apparent from the measurement results, in Example 1, the rebound amount was reduced to about half as compared with Comparative Example 2 in which no thickener was added, and Comparative Example 1 in which a cellulosic thickener was added was used. Again, it was confirmed that the rebound amount could be reduced by about 1/3.

In this case, the starch-based thickener is added only by about 2% by weight based on the total weight of water.
Even if a relatively expensive starch-based thickener is used, the above-mentioned effects can be exerted without impairing economic efficiency.

[0023]

As described in detail above, according to the method for producing shotcrete according to the present invention, the amount of rebound can be sufficiently reduced and a remarkable effect of improving the working environment can be obtained.

[Brief description of the drawings]

FIG. 1 is a process explanatory view showing one example of a method for producing shotcrete according to the present invention.

[Explanation of symbols]

 c Cement s Fine aggregate S Coarse aggregate W Water W1 Primary mixing water W2 Secondary mixing water X Starch thickener C Shotcrete

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masatomo Nakajima 2-15-2 Konan, Minato-ku, Tokyo F-term (reference) 4G012 PB39 PC08 PD01 PE01 4G056 AA07 CB32 CB34 CB35

Claims (2)

[Claims] 1. A method for producing concrete to be sprayed on a tunnel excavation wall surface, wherein the mixing water for the concrete is kneaded by dividing the mixing water into primary and secondary mixing water twice, and kneading with the secondary mixing water. A method for producing shotcrete, wherein a starch-based thickener is added. 2. The shotcrete according to claim 1, wherein the starch-based thickener is added in an amount of about 2% by weight based on the total weight of the primary and secondary mixing waters. Manufacturing method.