JPH0468429B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wet spraying method for concrete, etc.

(Prior Art) There are two methods for spraying hydraulic materials such as concrete and mortar: a dry method and a wet method. The latter generally produces less dust and rebound than the former,
It is widely used for construction work such as tunnels and slopes because it has the advantage of forming a coating layer with good strength.

Conventionally, this wet spraying method involves transporting a wet material made by kneading a mixture of cement, aggregate, and water in a concentrated manner through a hose using a pressure pump, and adding compressed air using a spray nozzle at the end of the hose. A method of spraying onto the surface was used.

(Problems to be Solved by the Present Invention) However, in this method, the wet material is affected by friction with the inner surface of the hose, and furthermore, a constriction phenomenon occurs due to expansion and contraction due to the elasticity of the hose. There was a problem that clogging easily occurred and the conveyance distance was greatly limited. In order to improve this, it is necessary to increase the ramp value or increase the amount of cement, resulting in the problem that a good quality coating layer cannot be formed.

In addition, since compressed air is added at the spray nozzle, the spray is applied to the wet material without sufficient speed, resulting in weak adhesion to the construction surface, which tends to cause flaking at tunnel arches and vertical sections. There was a problem.

As a wet spraying method, there is Japanese Patent Application Laid-Open No. 59-55370 proposed by the present applicant. In this prior art, wet material is continuously discharged from a pump into a pressurized container, where the wet material is constantly stored and stirred, and compressed air is supplied to the inside of the container and the container outlet, and the wet material is transferred with a hose. The quick-setting agent was added in front of the spray nozzle using air flow.

However, this prior art uses a pressure pump and a pressurized container type sprayer together as a wet material supply mechanism, and firstly, it uses a pressure container with an agitation function, which increases system costs and costs. Running costs are extremely high.Secondly, the system becomes larger and a large pressure vessel must be brought to the site each time, causing inconvenience during tunnel construction, etc., and the inside of the pressure vessel must be cleaned every time the spraying is completed. This makes the work complicated. Third, compressed air is added inside the pressure vessel and at the outlet of the pressure vessel, which tends to result in an excessive amount of air being added, and the aggregate and paste components tend to separate during the air flow from the pressure vessel to the spray nozzle. It was hot.

Furthermore, in wet spraying, quick-setting agents are often added to obtain initial strength, but in conventional methods, if they are added to other formulations and pumped, they react during conveyance, promoting clogging, and blowing When added at the attachment nozzle position, the spray is sprayed onto the wet material without being sufficiently mixed with it, leading to problems such as an increase in the amount of dust generated and deterioration of the working environment.

(Means for Solving the Problems) The present invention solves the problems of the conventional wet spraying method as described above, and can easily produce low-slump materials without causing clogging even when using a simple and inexpensive system. The objective is to provide a wet spraying method that allows spraying to be carried out over long distances, suppresses the generation of dust and rebound, and can apply a coating layer with good adhesion and strength. .

In order to achieve this object, the present invention pumps the wet material using a rigid pipe line from a spray nozzle to a predetermined distance upstream of the spray nozzle, and at that position compressed air is added to the pipe line from a dosing nozzle to blow the sample. The admixture is conveyed by air to a spray nozzle, and the admixture is added and sprayed at or near the spray nozzle.

According to the inventor's actual research, the above-mentioned position upstream of the spray nozzle by a required distance is approximately 20 m from the spray nozzle. The most effective method is to use a rubber hose to transport the air under pressure and after the air addition section.

Furthermore, according to the inventor's experiments, the addition of air to the admixture should be carried out in a certain relationship with the addition of intermediate air, and specifically, the addition pressure of the admixture P ₂
It is appropriate to set the intermediate air addition pressure to be higher than the intermediate air addition pressure _P1 , and to set the differential pressure between the pressures _P2 and _P1 to about 0.5 to 2.0 Kg/ ^cm2 .

(Function) When the above configuration is adopted, first,
By carrying out dense transportation using a rigid tube, there is no frictional resistance within the tube or constriction resistance due to expansion and contraction, so even if the slump and water-cement ratio are small, it can be smoothly conveyed over a long distance. Furthermore, since compressed air is added at a predetermined position behind the spray nozzle and the process shifts to airflow conveyance, wet materials can be sprayed at high speed and high pressure. A separation phenomenon, that is, a state in which the paste component and the aggregate component separate does not occur. Since the air flow is conveyed using a rubber hose, the swinging operation necessary for spraying can be easily performed.

Since the intermediate air addition pressure and the admixture addition pressure are defined as described above, the admixture can be mixed extremely well, and the admixture addition section can be smoothly mixed without adhesion or clogging. Can perform construction.

(Example) The wet spraying method according to the present invention will be described below with reference to the accompanying drawings.

Fig. 1 shows an embodiment of the present invention, in which 1 is a pressure pump for wet materials, 2 is a pump pressure feed path (dense conveyance path) connected to the pressure pump 1, and is connected to a metal connection pipe or a slider connected to this. It consists of steel pipes lined with face material, etc., connected in series by pipe joints 3 such as Victor joints.

Reference numeral 4 denotes an air flow conveyance path, which is made of a flexible tube such as a rubber hose, and has a spray nozzle 5 attached to its tip. It is preferable that the air flow conveying path 4 has a smaller path diameter than the pump pressure feeding path 2. 6 is the air flow conveyance path 4
This compressed air addition nozzle 6 is interposed and connected to the boundary between the pump pressure feed path 2 and the pump pressure feed path 2, and this compressed air addition nozzle 6 is provided at a required position behind the spray nozzle 5.

Specifically, approximately upstream from the spray nozzle.
The distance is up to 20m. The reason for limiting the air addition position in this way is the result of repeated practical studies by the present inventors. Even if air is added upstream from the above position, it is possible to shift from dense conveyance to air flow conveyance. This is because the wet material is completely separated into a paste component and an aggregate component, and even if sprayed, the desired coating layer will not be formed.

The compressed air addition nozzle 6 is connected to an air supply source 8 such as an air compressor or a receiver tank by an air line 9, and the pressure and flow rate are controlled by a pressure gauge 10 and a control valve 11 provided in the air line 9. Note that the air pipe line 9 may be connected to a pipe line 13 from a liquid supply source 12 such as water via a valve 14. According to this, the water and cement ratios can be easily adjusted depending on the construction situation.

Reference numeral 15 denotes an admixture addition nozzle installed at or near the spray nozzle 5 (in normal cases, up to a maximum of about 4 m behind), which is connected to an admixture supply device 17 via a supply hose 16, and is mixed using compressed air. In other words, the quick-setting agent is usually pneumatically delivered.

As the pressure pump 1, various types can be used as long as they are capable of conveying wet materials in a concentrated manner, that is, without adding compressed air or dispersing the materials. That is, it may be of any type, such as a squeeze type, a screw type, or a piston type.

In the illustrated example, a bottomed hopper 19 with a discharge port 18 provided on the front wall, two piston cylinders 20 and 20' provided on the back wall side of the bottomed hopper 19,
A double valve consisting of a cylindrical switching valve 22 supported by a swinging arm 23 so that one end is always in communication with the back port of the discharge port and the other end is alternately connected to the open grooves 21, 21' of the piston cylinders 20, 20'. A piston-type pressure pump is used.

When the admixture is a liquid, the admixture supply device 17 is a pump, and the admixture is pneumatically fed to the addition nozzle 15 by compressed air from a compressed air supply source 8' connected to the supply hose 16.

Since the one shown uses granules as an admixture, the admixture supply device 17 consists of a tank 24 containing the admixture, a rotor 25 rotatably provided at the bottom of the tank, and one side of the rotor 25. A fixed-quantity cutting type is used, which is composed of a discharge part 26 facing the discharge part 26 and an air blowing member 27 disposed near the discharge part 26.

Although the structure of the compressed air addition nozzle 6 does not matter, in this embodiment, as shown in FIGS. 2 and 3, the main body 29 is composed of a straight cylindrical portion 30 and a tapered cylindrical portion 31,
It consists of an annular pipe 32 surrounding the main body 29, and a plurality of oblique blowing pipes 33 connected from the annular pipe 32 to a position close to the boundary with a straight cylindrical portion of the main body 29, preferably a tapered cylindrical portion.

Each oblique blow pipe 33 has a diameter of about 25
It has an inclination of ~35°, and has an inclination of about 10 to 20° from the center of the nozzle when viewed in plan, so that the blowing direction is not centripetal but close to the tangential direction.

When using a device with this structure, the compressed air forms a spiral high-speed airflow in the conveyance path of the wet material, resulting in layered development that occurs due to dense conveyance, in other words, the paste collects on the tube wall. This effectively loosens the situation in which aggregates with small particle diameters collect in the inner layer and aggregates with large particle diameters in the center of the tube, allowing paste and fine aggregates to adhere around the coarse aggregates using this as a core. It becomes possible to remix.

Thus, according to the present invention, the kneaded wet material is put into the pressure pump 1, and is thereby delivered to the pump pressure path 2 at a predetermined amount and pressure. Since the pump pressure feed path 2 is a rigid pipe, even if the wet material has a small slump value, it can be transported smoothly and densely.

When the dense conveyance is performed to the required position behind the spray nozzle 5 in this way, compressed air is added from the compressed air addition nozzle 6. As a result, the wet material is given buoyancy and is transported in a thin flow at high speed through the flexible airflow transport path 4. In the case of the present invention, a wet material with a small slump value can be used, so that good conveyance conditions can be obtained.

Then, the admixture is added with air by the admixture addition nozzle 15 at or near the spray nozzle 5 . The addition conditions at this time are that if the intermediate addition air pressure is P ₁ and the air addition pressure of the admixture is P ₂ , it is necessary that P ₂ > P ₁ , and P ₂
- It is necessary to control P ₁ to be in the range of about 0.5 to 2.0 Kg/cm ² .

This is a result of the inventor's findings from experiments; if the differential pressure between P ₂ and P ₁ is too small, the admixture will adhere to the inside of the pipe at the admixture addition nozzle 15, and this will grow over time and cause blockage. wake up Conversely, P ₂
If the _differential pressure between When the differential pressure is set within the above range, sufficient mixing is achieved and no adhesion or clogging occurs in the addition region.

The wet material to which the admixture has been added as described above is sprayed at high pressure by the spray nozzle 5, and as a result, under the condition that the pressure pump 1 is placed far from the site, high quality wet material with small slump can be produced. can be sprayed with less dust and rebound and better adhesion.

Next, specific examples of the present invention will be shown.

Concrete was sprayed on a tunnel face approximately 20 m in diameter using the present invention. The mixture is cement 380
Kg/ ^m3 , S/a: 60%, W/c: 53%, Ad: 0.9
%, S1: 8±2cm, maximum aggregate 15m/m, FM:
It was set at 2.85.

The above wet material was pumped using a double piston pump at a discharge rate of 6 m ³ /h and a discharge pressure of 30 to 40 kg/cm ² .

The pump pressure line is a steel pipe with a diameter of 100 mmφ and a total length of 30 m, which is connected in multiple stages.A compressed air addition nozzle is connected to this end, and a rubber hose with a hose diameter of 62.5 mmφ and a length of 10 m is connected from the front end of the nozzle. An airflow conveyance path was created, an admixture addition nozzle made of a Y-shaped tube was connected to the end of this airflow conveyance path, and a spray nozzle was connected at a position 2.5 m from the nozzle.

The compressed air addition nozzle has a total length of 600 mm and a straight cylindrical part of 200 mm.
mm, the tapered cylinder part was 400mm, and there were four oblique blowing pipes, each having an inclination of 30° with respect to the straight cylinder part and 15° with respect to the center line.

Air addition with the compressed air addition nozzle is at a pressure of 1.8
~2.0Kg/cm ² and a flow rate of 9 to 10Nm ³ /min, and controlled the powdered quick setting agent from the admixture addition nozzle to a pressure of 3.0Kg/cm ² and a blowing rate of 6.8% (relative to the amount of cement). I blew it.

As a result, despite the low slump as before, the amount of dust was 4 to 5 kg/kg near the face.
m ³ was extremely low at 2 mg/m ³ at a position 10 m from the face, and the amount of rebound was also extremely low at approximately 25% at the arch and approximately 14% at the side wall, resulting in a lining layer with good strength and adhesion. .

Furthermore, when the differential pressure between the intermediate addition air pressure and the admixture addition pressure was set to less than 0.5Kg/m ² , clogging occurred first at the admixture addition section, and when the pressure difference was increased to a value exceeding 2.0Kg/cm ² . The amount of dust and rebound increased rapidly. The best results were obtained when the admixture addition nozzle was located within about 4 m from the spray nozzle.

The present invention is suitable for spraying concrete and mortar, and can of course also be applied to wet spraying of monolithic refractories.

(Effects) According to the present invention described above, when spraying a wet material, the wet material is pumped from the pump using a rigid pipe line up to a maximum of 20 m upstream from the spray nozzle. Compressed air is added to the wet material from an addition nozzle installed in the pipe line up to 20m upstream, and the airflow is conveyed to the spray nozzle.
Admixture at or near the spray nozzle
The admixture addition pressure P ₂ is added to the compressed air pressure P ₁ at the addition nozzle so that P ₂ > P ₁ and P ₂ - P ₁ is 0.5 to 2.0 Kg/cm ² and sprayed. and
The wet material is pumped up to 20m upstream from the spray nozzle using a rigid pipe, so it can be transported smoothly even if the slump or water/cement ratio is small. Since compressed air is added from the addition nozzle, the paste and aggregate components can be transported by airflow without being separated, and the admixture can be added to the wet material under the above specific conditions while being transported by airflow. This does not cause blockage of the hose or greatly disturbs the conveying flow, and since the paste and aggregate components are not separated due to the setting of the air addition position as described above, they can be mixed reliably and sufficiently. Therefore, high-quality wet materials with low slump can be transported over long distances and sprayed at high pressure without clogging and with less dust and rebound. In addition, since a two-stage supply method of a pump and a pressure vessel is not required for supplying wet materials, the system configuration can be made simple, compact, and inexpensive. Excellent effects such as being able to provide a practical spraying method suitable for spraying etc. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an embodiment of the wet spraying method according to the present invention, and FIG. 2 is a partially cutaway side view showing an example of the intermediate air addition nozzle in the present invention.
FIG. 3 is also a longitudinal sectional view. 1...Pressure pump, 2...Pump pressure feed path, 4...
...Air flow conveyance path, 5...Blowing nozzle, 6...Compressed air addition nozzle, 15...Admixture addition nozzle.

Claims (1)

[Claims] 1. When spraying wet material, the wet material is transferred from the pump to the spray nozzle using a steel pipe.
Compressed air is pumped to a position upstream of 20 m, and compressed air is added to the wet material from an addition nozzle installed in a pipe line at a maximum of 20 m upstream from the spray nozzle, and airflow conveys the material to the spray nozzle. In the vicinity, the admixture is added under compressed air pressure at the dosing nozzle.
The admixture addition pressure P ₂ for P ₁ is P ₂ > P ₁ and P ₂ −P _1.
A wet spraying method characterized by adding and spraying at a relationship of 0.5 to 2.0Kg/cm ² .