JPH0762398B2 - Blocking method of spray hose in wet concrete spraying method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for preventing clogging of a spray hose in a concrete spraying method.

[Conventional technology]

A so-called concrete spraying method is known in which mortar, concrete, steel fiber-mixed concrete, etc. are pressure-fed using compressed air and sprayed directly onto the placing surface.

As a general rule, this concrete spraying method requires no formwork for construction, can construct structures with complicated shapes, can place concrete in close contact with the construction surface, and is capable of placing work in narrow spaces. It has features such as being present.

Therefore, this method is often used for protection of rocky slopes and lining of underground cavities such as tunnels.

Among them, NATM method (New Austrian
Concrete spraying when the Tunneling Method) is adopted is a typical one. The NATM method is
After excavating the tunnel, the primary concrete is sprayed promptly, and a U-shaped shrinkable support structure is built.
A method of placing gold steel or rock bolts and spraying secondary concrete on top of them to prevent loosening of the surrounding rock mass after anti-conducting excavation as much as possible, and make full use of the bearing capacity of the rock mass. It is a tunnel construction method aimed at that.

By the way, in this concrete spraying method, the material, that is, cement and other kneading materials are mixed with water in advance, and the mixture is pumped with a concrete pump and sprayed with high-pressure compressed air (3.0 to 3.5 kgf / cm ² ). A so-called wet method and a dry method in which materials are mixed in a dry state, which is transported by compressed air through a hose or a pipe, and pressure water is added immediately before being jetted from a nozzle to mix the material and water and sprayed. There is.

In general, in the tunnel construction, it is usual to carry out the spray construction by a wet method which has no dust rebound and has high quality uniformity.

[Problems to be solved by the invention]

By the way, in the spraying by the wet method, if the control before and after the work is poor, there is a drawback that the tip of the hose or the nozzle is clogged with concrete and a so-called spraying hose is clogged.

In particular, this adverse effect is remarkable when concrete is mixed with a quick-setting agent and then sprayed.

For example, in tunnel construction using the NATM method, connect a mixing pipe near the exit of the transportation piping system that pumps fresh concrete with a concrete pump, mix the quick-setting agent with the concrete using this mixing pipe, and spray it from the nozzle. ing.

That is, since the quick-setting agent that hardens the concrete in 2 to 3 minutes is mixed in the concrete blown out from the nozzle, after the spraying work, the quick-setting agent is added to the nozzle and the pipe system near the nozzle. If the mixed concrete remains or flows backward and remains, it solidifies and causes a so-called blockage phenomenon.

In particular, as a quick-setting agent, concrete is added to 2-3 as described above.
Since it has a function of curing in minutes, if the spraying work is to be performed intermittently, it will cause blockage and interrupt the work each time.

[Means for solving problems]

Therefore, the present invention, in order to prevent such troubles,
In a wet concrete spraying method in which compressed air is blown into a mains for transporting concrete and concrete is sprayed from a nozzle, a bypass pipe line is provided in parallel in the compressed air supply pipe system to blow the concrete. When you start
At the end of spraying, close the valve of the compressed air supply pipe system and open the valve of the bypass conduit to supply high pressure compressed air to the concrete transport main system, and start spraying again. After that, when the work is stabilized, the valve of the pipe system for sending compressed air is opened and the valve of the bypass line is closed to spray concrete.

Especially when adding a quick-setting agent to concrete and placing it, as in the case of the NATM method, a valve was installed in the hose for pressure-feeding the quick-setting agent to prevent blockage due to reverse flow of concrete. It is characterized by.

[Action]

According to the wet concrete spraying method of the present invention, high-pressure compressed air is supplied from the bypass pipe to the concrete transport main system before and after the spraying work. The so-called mixing tube for the quick-setting admixture and the pressure-feeding hose for the quick-setting admixture are scavenged at a portion where so-called pipeline blockage occurs, and work interruptions due to blockage are eliminated.

〔Example〕

Next, a detailed description will be given based on an example in which the present invention is applied to blockage of a spray hose used for tunnel construction by the NATM method.

First of all, what is shown in the drawing is a front end portion of a main system A for concrete transportation used in a concrete spraying method, the base end of which is connected to a concrete pump 1, and the concrete pump 1 pumps the kneaded concrete. It will be done.

The concrete transport main system A includes a concrete pipe 2 and a taper pipe 3 connected to the concrete pump 1.
The concrete hose 4 and the mixing pipe 5 are sequentially connected, the tip hose 6 is further connected to the mixing pipe 5, and the spraying nozzle 7 is connected thereto.

The tip end hose 6 and the concrete hose 4 are provided in the middle of the concrete transportation main system A in order to maintain flexibility and maintain workability of the transportation main during spraying work. .

Next, in the compressed air supply piping system B for injecting compressed air into so-called green concrete that is pressure-fed from the concrete pump 1, the base end is connected to the compressor 8,
It is configured as a pipe system in which the tip portion is connected to the mixing pipe 5 of the main pipe A for concrete transportation.

A ball valve 9, a pressure reducing valve 10 and a pressure gauge 11 are provided in the compressed air supply piping system B for blowing compressed air (7 kgf / cm ² ) sent from the compressor 8. It is configured so that it can be adjusted to a suitable pressure (3.0 to 3.5 kgf / cm ² ).

According to the present invention, a bypass pipeline BP is provided in the compressed air supply piping system B as shown in the figure, so that high-pressure air (7 kgf / c) is applied from the compressor 8 at the start and end of the spraying work.
m ² ) is sent to the tip portion of the main system A for concrete transportation via the bypass pipe BP to be scavenged.

Reference numeral 9a is a ball valve provided in the bypass pipe BP and is used when switching between the spraying work and the scavenging work.

Next, C is a quick-setting admixture pressure-feeding hose for adding the quick-setting admixture to concrete, the base end of which is connected to the pressure-feeding machine 12 for pressurizing the fast-setting admixture, and the tip end is for feeding the compressed air. Piping system B
Connected to the main pipe A for mixing concrete for concrete transport 5
Then, the quick-setting agent is mixed with the concrete together with the compressed air and blown out from the nozzle 7.

The ball valve 9b provided on the hose C for pressure-feeding the quick-setting admixture
Is a valve for preventing backflow of concrete containing a quick-setting agent.

In the embodiment of the present invention, since the bypass pipeline BP is provided in the compressed air supply piping system B for spraying as described above, the ball valve 9 is first closed at the start of concrete spraying work. Open the ball valve 9a of the bypass line BP.

And compressed air of a higher pressure than the compressor 8 (7kgf / c
When m ² ) is sent to the main system A for concrete transportation, the tip side of the mixing pipe 5 is completely scavenged.

Next, when the scavenging is completed, the ball valve 9a of the bypass pipeline BP is closed, the ball valve 9 of the piping system B for supplying compressed air is opened, and the pressure reducing valve 10 is adjusted to give a predetermined concrete spraying pressure of 3.0 to Set to 3.5kgf / cm ² and perform spraying work.

Further, when the spraying work is completed, the ball valve 9a of the bypass pipeline BP is opened and high-pressure air is sent to scavenge.

In this case, if the opening / closing of the ball valve 9a of the bypass line BP is repeated 2 to 3 times, the scavenging effect becomes particularly reliable.

Of course, when the quick-setting agent is used, the ball valve 9b provided in the quick-setting agent pressure-feeding hose C is closed before sending the high-pressure air for scavenging to prevent the concrete from flowing backward.

〔The invention's effect〕

The present invention, as described above, sends high-pressure air to the concrete transportation main system immediately before and immediately after the spraying work,
Since it is scavenging air, it is inevitable that concrete stays in the nozzles of the main system for transportation, mixing pipes, etc. and hardens to cause a so-called blockage phenomenon as in the conventional case.

Therefore, the spraying work can be carried out efficiently without interruption, and the advantages and features of the spraying method can be further enhanced.

Further, regarding the apparatus configuration for carrying out the method, it is sufficient to simply provide the bypass pipe line in the compressed air aeration pipe system, which does not require a large amount of equipment cost and can be adopted very easily.

Of course, the features of the wet spraying method, such as the generation of dust and the prevention of rebound, can be fully exerted, and maintenance as a construction device is easy.

[Brief description of drawings]

The figure shows a piping system for carrying out the method for preventing blockage of a spray hose in the concrete spraying method according to the present invention. A: Main pipe system for concrete transportation B ... Piping system for sending compressed air BP ... Bypass line C ... Hose for pressure-feeding quick-setting adhesive 1 ... Concrete pump 1 ... Concrete pipe, 3 ... Taper Pipe 4 …… Concrete hose 5 …… Mixing pipe, 6 …… Tip hose 7 …… Nozzle, 8 …… Compressor 9,9a, 9b …… Ball valve 10 …… Reducing valve, 11 …… Pressure gauge 12 …… Pressing Machine

Front page continuation (72) Inventor Ryozo Miyazaki 2-8-30 Innai, Funabashi City, Chiba Taisei Construction Apart B-105 (72) Inventor Shinji Oda 15-14 Sakuragaoka Town, Tsuchiura City, Ibaraki Prefecture (72) Invention Mitsuaki Aoya Tsui, Kamiura-cho, Nankai-gun, Oita Prefecture (No address) (72) Inventor Masanori Ichikawa 97, Teranoshita, Ohashi, Matsudo-shi, Chiba Nariho Construction (56) Reference JP 63-201261 (JP, A) JP-A-58-143098 (JP, A)

Claims (2)

[Claims] 1. In a wet concrete spraying method in which compressed air is blown into a mains for transporting concrete and the concrete is sprayed by a nozzle, a bypass is provided in parallel with an air supply pipe system in which the compressed air is blown. A pipe is provided, and at the beginning and end of concrete spraying, the compressed air supply pipe system valve is closed, the bypass pipe valve is opened, and high pressure is applied to the concrete transport main system. After the compressed air has been sent and spraying has started, when the work is stable, open the valve of the compressed air supply pipe system and close the valve of the bypass pipe to spray concrete. A method for preventing clogging of a spray hose in a wet concrete spraying method, which is characterized in that 2. The method according to claim 1, wherein in the concrete spraying method of blowing a quick-setting agent into concrete, a valve is provided in a hose for pressure-feeding the quick-setting agent to prevent backflow of concrete. Blocking method for spray hose in wet concrete spraying method.