JPH0617633B2 - Wet spraying method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a concrete spraying method, and more particularly to a wet spraying method in which concrete is kneaded and sprayed in advance.

<< Background of the Invention >> As is well known, in recent tunnel excavation, rock bolts,
The so-called NATM method, which uses shotcrete as a support, is becoming mainstream.

In this type of construction method, concrete is sprayed at an early stage in order not to loosen the excavated ground, but the problems at that time are the deterioration of the working environment due to dust and the increase in the amount of rebound during spraying.

Generally, the concrete spraying method is a dry method in which the constituent materials of concrete are individually transferred by air or the like, and these and water are simultaneously supplied to the jet nozzle, and the constituent material of concrete is previously kneaded with water, There is a wet method in which this is discharged by a jet nozzle.

The dry method has the advantage that it is easy to install, but it produces more dust and rebounds than the wet method, and
Since it cannot be said that the ATM construction method is very advantageous, the number of construction examples of the wet construction method is increasing.

However, even in the wet method, the amount of dust and the amount of rebound are smaller than those in the dry method, and the deterioration of the work environment and the increase in the amount of rebound due to the generation of dust have not yet been solved.

The present invention has been made in view of the background described above, and an object of the present invention is to provide a wet spraying method capable of significantly reducing the amount of dust and rebound.

<< Means for Solving the Problems >> In order to achieve the above object, the present invention relates to a wet spraying method of spraying concrete obtained by kneading aggregate, cement and water onto a wall surface of a tunnel or the like, in a cellulosic system. The thickening agent is mixed in the powder or liquid in the cement or the water in advance, and then the mixture is sprayed.

<< Working >> The thickener added before kneading increases the viscosity of the shotcrete, prevents diffusion when sprayed from the nozzle, reduces dust generation, and reduces the amount of dust when adhering to the excavated wall surface. However, since the adhesiveness increases due to thickening, the amount of rebound also decreases.

Further, the cellulosic thickener is not kneaded at the same time with the aggregate, cement, water, etc., but is mixed in advance with cement or water having a volume significantly smaller than the total amount of concrete, so the kneading time The homogeneity of the thickener is ensured without lengthening. When the thickener is mixed with the bone agent, cement, water, etc. at the same time, the viscosity of the concrete gradually increases during the kneading.Therefore, in order to ensure homogenous mixing of the thickener in high-viscosity concrete, the mixing time Need to be long. Even when a powdery thickener is mixed in water, the cellulosic thickener is water-soluble and easily dissolves in a short time.

<< Examples >> Hereinafter, preferred examples of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory view showing a first embodiment of a wet spraying method according to the present invention.

In the spraying method shown in the figure, a predetermined amount of a cellulosic thickener 4 is added to the cement 1 in a powder state before the cement 1, the aggregate 2 and the water 3 are added and kneaded.

Then, the concrete mixed by a concrete mixer or the like is pumped to a spray nozzle together with a liquid or powder quick-setting agent by a pump, compressed air, or the like, and jetted from the nozzle toward the excavated wall surface.

Here, when the thickener 4 is mixed, the amount of air increases, and when pumpability is impaired, a predetermined amount of the defoaming agent 5 should be added to the thickener 4 in advance. Good.

FIG. 2 is an explanatory view of the second embodiment of the present invention. In this embodiment, the cement 1, the aggregate 2 and the water 3 to be kneaded are mixed with the thickener 4 in advance and, in some cases, the defoaming agent. Add 5,
After making the solution 6, cement 1, aggregate 2,
Dissolve liquid 6 is poured and used as a kneading concrete for the spraying work together with a quick-setting agent.

FIG. 3 shows the dust of the first example of the above-described examples of the present invention and the wet method which is conventionally performed for comparison without the addition of the thickener 4, when the same is applied under the same conditions. The results of actual measurement of the concentration and the rebound rate are displayed in a graph.

In this measurement, a liquid and a powder were used as the quick-setting admixture, respectively, and concrete having the following composition was used.

The amount of the quick-setting admixture is 6 for the liquid when the amount of cement is
%, And 4% in the case of powder.

As is clear from the measurement results, in the conventional wet method,
Both the dust concentration and the bounce rate show large values, and there are large variations in these values, whereas the method of the present invention greatly reduces the dust concentration and the bounce rate, and the variations are small.

This is because the viscosity of the sprayed concrete is increased by the thickener 4 added before the kneading, and as a result, when sprayed from the spraying nozzle, diffusion in a wide range is prevented and dust is restricted, and it also reaches the excavated wall surface. Since the adhesive force of is also increased, the rebound rate is also reduced.

Further, the thickener is not kneaded at the same time with cement, aggregate, water, etc., but is premixed in cement or water whose volume is significantly smaller than the total amount of concrete, so the homogeneity of the thickener is In addition to being assured, the cellulosic thickener is water-soluble and mixes well with other concrete components during kneading, resulting in a homogeneous thickened concrete and stable spraying with little dispersion. It can be performed.

<< Effects of the Invention >> As described in detail in the above, according to the wet spraying method according to the present invention, a relatively simple configuration in which a thickener is premixed with cement or water before kneading is added. By virtue of this, without increasing the kneading time, the viscosity of concrete is increased uniformly, and in a stable state, it is possible to obtain the excellent effect of significantly reducing the amount of dust generation and the amount of rebound and preventing the deterioration of the work environment. .

[Brief description of drawings]

FIG. 1 is a block diagram of the first embodiment of the method of the present invention, FIG. 2 is a block diagram of the same second embodiment, and FIG. 3 is a graph of measured results of dust concentration and rebound rate. 1 ... Cement, 2 ... Aggregate, 3 ... Water, 4 ... Thickener, 5 ... Defoaming agent

Claims (1)

[Claims] 1. In a wet spraying method of spraying concrete obtained by kneading aggregate, cement and water onto a wall surface of a tunnel or the like, the cellulosic thickening agent is in the form of powder or liquid in advance as the cement or the above. A wet spraying method characterized by mixing and spraying after mixing in water.