JPH0432911B2 - - Google Patents

Description

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

(Conventional techniques and their problems) Dry and wet spraying methods are available as construction methods for hydraulic materials such as concrete and mortar.
In particular, the latter is widely used as a lining method for cavities, slopes, etc., including NATM, which has become popular in recent years.

There are various methods for this wet spraying method, such as a method in which a mixture of cement, aggregate, and water is pumped through a hose from a pump to a spray nozzle in a concentrated state, and then compressed air is attached and sprayed near the spray nozzle. .

However, in any case, the spraying method requires implementation conditions such as the type of material, composition, type of spraying machine, amount of compressed air, pressure, structure and dimensions of piping and nozzles, distance from the spraying surface, etc. It involves a wide variety of complex factors such as the spray angle, and these factors also change during operation.

Therefore, it is not easy to perform good construction, and in particular,
Major problems include dust generated from the spray nozzle, splashing from the construction surface, quality of the spray layer, and surface condition.

Until now, almost no effective method has been found to counter this problem, and only some of the various factors mentioned above have been appropriately selected and adjusted based on the experience of highly skilled workers.

(Means for Solving the Problem) The present invention was devised to solve the above-mentioned problems, and its purpose is to always provide optimal blowing without requiring a high degree of skill or experience. It is an object of the present invention to provide a wet spraying method that can maintain the applied state and form a stable sprayed layer with little dust and splashing, good quality and properties.

In order to achieve this objective, the present inventors conducted various spraying experiments. As a result, the conventional method of transporting material from a pump to a hose in a concentrated manner and adding air at the spray nozzle is not preferable due to the problems of dust and splashing mentioned above, as well as clogging and adhesion. However, Japanese Patent Application No. 59-149066 (Japanese Unexamined Patent Publication No. 61-28670) was filed by one of the present applicants.
It has been found that a method of transporting densely through a pipe to a certain distance from the pump, adding compressed air at the end of the pipe, and then transporting the air stream to the spray nozzle for injection is basically suitable. Ta.

In implementing this spraying method, there is a strong correlation between the above factors and the amount of air consumed. Specifically, the amount of air consumed and the dust concentration are
We found that the relationship shown in Figure 4 generally holds.

The present invention focuses on this and uses a constant flow rate control valve to automatically control the amount of air consumption to a target value.

That is, the feature of the present invention is that the material is pressure-fed from the pump to a predetermined distance through a rigid pipe, air for pressure is added at the terminal position of this rigid pipe, and airflow is conveyed to the spray nozzle using a flexible pipe. When spraying, a constant flow rate control valve is provided upstream of the on-off valve of the pressure air circuit, and the constant flow rate control valve provides sufficient buoyancy to the wet material and admixture to carry the airflow. The purpose is to set an amount of air to be blown to keep the dust concentration low, and to blow while controlling the amount of air to be blown to a constant value in accordance with fluctuations in the discharge pressure of the supply source.

In conventional spraying, including the case of the earlier application mentioned above, the spraying state was controlled by adjusting the opening of the on-off valve while looking at the pressure gauge using the air pressure as a parameter, but with this method, The actual amount of air supplied varies depending on the pressure on the compressor side, the condition (load) of the sprayed material, the position of the pressure gauge in the circuit, etc., and the degree of opening and closing of the valve depends on the operator's experience and intuition, so it may not be constant. However, large variations occur. In order to cope with pressure changes during spraying, it was necessary to have workers on duty at all times.

According to the present invention, all of these difficulties are solved, and by simply setting a desired value in advance, it is possible to always maintain an optimal spraying condition regardless of pressure fluctuations.

(Example) Examples of the present invention will be described below with reference to the accompanying drawings.

Figures 1 to 3 show an embodiment of the wet spraying method according to the present invention, in which 1 is a pump for pumping wet material, 2 is a rigid pipe connected to the pump 1 for pumping, and a steel pipe is used. Alternatively, rigid tubes 2a, 2a made of a material lined with a smooth surface material are connected in multiple stages by a joint 3 such as a victory joint.

4 is a flexible conduit made of a rubber hose, etc., and a spray nozzle 5 is connected to the tip thereof. Reference numeral 6 denotes a compressed air addition section that is connected to the boundary between the rigid pipe 2 and the flexible pipe 4, and this addition section 6 is generally connected from the spray nozzle in order to prevent separation of the wet material. It is preferable that the distance be approximately 20m to the rear.

The compressed air adding section 6 is connected to an air supply source 8 such as an air compressor through an air line 7, and the air line 7 has a pressure gauge 12 and an on-off valve 11 incorporated therein.

In the present invention, a constant flow rate control valve 9 is connected to the air pipe line 7 before the on-off valve 11. Although the structure of the constant flow rate control valve 9 is arbitrary, in this embodiment, the structure shown in FIG. Examples are used.
That is, a valve plate 29 to which a diaphragm 34 is attached and a spring 3 that pulls the valve plate 29 are attached to the secondary body.
A pressure compensating valve 31 having a pressure compensation valve 31 with a variable throttle structure is disposed on the primary side body, and a desired flow rate value is set by rotating an operating section 280 manually or by a motor or the like. It's becoming like that.

A displacement tank 32 communicates with the cylindrical chamber containing the spring 30, and an air supply pipe 33 communicating with the outlet side of the flow rate setting valve 28 communicates with the upper space of the displacement tank 32.

The air conduit on the inlet side of the constant flow rate control valve 9 is preferably equipped with a regulator in order to absorb fluctuations in the source pressure of the air supply source 8 and to ensure that compressed air at a constant pressure always acts on the constant flow rate control valve 9. A pressure valve 10 is interposed. Instead of this pressure regulating valve 10, two compressors may be used in series.

FIG. 2 shows another embodiment of the invention,
For example, the pressure gauge 1 on the outlet side of the constant flow rate control valve 9
A pressure sensor 13 is installed near 2, and this pressure sensor 13 detects pressure fluctuations in the pressure air addition section 6, and the flow rate setting valve operating section 280 of the constant flow rate control valve 9 is set to increase or decrease via the converter 14. The set flow rate is automatically controlled by operating the pump on the side.

Various types of pumps can be used as the pressure pump 1 as long as they can discharge the wet material in a concentrated manner. That is, it may be of any type, such as a squeeze type, a screw type, or a piston type.

What is shown in the figure includes a bottomed hopper 19 with a discharge port 18 provided on the front wall 18, and two piston cylinders 20, 2 provided on the back wall side of the bottomed hopper 19.
0', one end is always in communication with the back of the discharge port, and the other end is connected to the openings 21, 2 of the piston cylinders 20, 20.
A double-piston type pressure pump is used, which includes a cylindrical switching valve 22 supported by a swing arm 23 so as to be alternately connected to the valve 1'.

In addition, in this embodiment, the spray nozzle 5 or its vicinity (in normal cases, up to a maximum of about 4 m)
An admixture addition nozzle 15 is attached to the admixture, and this admixture addition nozzle 15 is connected to an admixture supply device 17 through a supply hose 16, and the admixture, that is, an accelerating agent in normal cases, is pneumatically fed by compressed air. It's getting old.

When the admixture is a liquid, the admixture supply device 17 uses 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.

In the illustrated example, since a powder is used as the admixture, the admixture supply device 17 includes a tank 24 containing the admixture and a pocket 250 rotatably provided at the bottom of the tank. A quantitative cutting machine consisting of a rotor 25 arranged at intervals, a discharge part 26 provided on one side of the rotor 25 so as to communicate with a pocket 250, and an air blowing nozzle 27 arranged near the discharge part 26. I am using the method.

The air blowing nozzle 27 is connected to an air supply source 8' by an air conduit 7'. As shown in FIG. 1, this air line 7' is also preferably provided with a constant flow rate control valve 9' or a pressure regulating valve 10', similar to the air line 7 for the wet material. It goes without saying that the circuit configuration shown in FIG. 2 may be adopted.

Even when a liquid is used as the admixture, the illustrated constant flow rate control valves 9' are incorporated in the air circuit for pressure feeding.

Note that the compressed air adding section 6 may have any configuration such as a ring nozzle. The illustrated one consists of a main body 60 in which a straight cylinder and a tapered cylinder are connected, an annular pipe 61 surrounding the main body 60, and a plurality of oblique blowing pipes 62 connected from the annular pipe 61 to the boundary position of the tapered part of the main body 60. The admixture is blown in as a swirling flow from the tangential direction of the main body.

According to the present invention, when spraying, the first
In the illustrated embodiment, the flow rate constant value control valves 9, 9' of the air circuits 7, 7' are set to the optimum amount of air for the construction conditions. This amount of air is sufficient to give buoyancy to the wet materials and admixtures and carry them through airflow, and to keep the dust concentration low within the range that satisfies the conditions. Specifically, it is 4.5Nm ³ / Select from the range of min to 7Nm ³ /min.

In this state, the kneaded wet material is put into the pressure pump 1 and started at a predetermined pressure, and the on-off valves 11, 11' of the air circuits 7, 7' are opened to supply compressed air from the supply sources 8, 8' to the air circuit. Send to.

Wet materials are conveyed smoothly and densely, even if the slump value is small, because the pressure path is a rigid tube.
When this dense conveyance is performed from the spray nozzle 5 to a predetermined rear position, a fixed amount of compressed air is added from the compressed air adding section 6. As a result, the wet material is given buoyancy and is transported through the flexible conduit 4 by airflow at high speed. Then, at or near the spray nozzle 5, the air-borne admixture is added from the addition nozzle 15 to the wet material being conveyed by the air stream, and the mixture is stirred and sprayed from the spray nozzle onto the construction surface. .

In the case of the present invention, as before, the air circuit 7,
Set the air amount to the fixed flow rate control valve 9, 9' at 7',
This valve automatically adds pressurized air at the optimum amount of air for the construction process, so there is less dust and rebound, and there is no separation of materials due to variations in the amount of air, which is included per unit amount of air. Since the amount of material to be loaded is accurately controlled, there is less variation in layer thickness and the surface quality is also good.

Simply controlling the air circuits 7, 7' with pressure gauges 12, 12' and opening/closing 11, 11' will not allow the supply source 8,
When the discharge pressure of 8' fluctuates, the actual amount of air fluctuates greatly, making it impossible to perform stable spraying.

In the present invention, if the optimum air amount is set in advance for the flow rate constant value control valves 9, 9', the supply source 8,
When the flow rate tends to increase or decrease from the set value due to fluctuations in the discharge pressure of the valve 8', for example, the diaphragm 34 of the pressure compensating valve 31
via which the valve plate 29 is raised or lowered, thereby reducing or increasing the passage cross-sectional area and returning the flow rate to the set value. Therefore, the set amount of air is always accurately supplied to the compressed air addition section 6 and the addition nozzle 15.

When the pressure regulating valves 10 and 10' are installed on the inlet side of the constant flow rate control valves 9 and 9', air at a constant pressure can always be supplied to the constant flow rate control valves 9 and 9', thereby improving flow control. This can be performed stably and accurately, and failure of the constant flow rate control valves 9, 9' can be prevented.

Furthermore, when the circuit configuration shown in FIG. 2 is adopted, the internal pressure of the pipe increases due to fluctuations in the slump value of the material passing through the rigid pipe 2 and the flexible pipe 4, and fluctuations in the amount of wet material pumped from the pressure pump 1. Even when the pressure changes, the pressure sensor 13 detects this, and the converter 14 corrects the flow rate setting of the operating section 280 of the constant flow rate control valves 9, 9', so that the optimum air amount is automatically set.
controlled and can always maintain the best spraying conditions.

Next, the results of actual spraying according to the present invention will be shown.

Concrete was sprayed on the tunnel face with a diameter of 10m. The composition is cement 360Kg/ ^m3 , S/a:
60%, W/c: 53%, Ad: 0.9%, Sl: 8±2
cm, maximum aggregate 15m/m, FM: 2.85. Discharge amount of the above material by double piston pump is 8
It was pumped at a rate of m ³ /h and a discharge pressure of 60 to 80 Kg/cm ² .

The rigid conduit has a total length of 60 m, which is made by connecting steel pipes with a pipe diameter of 80 mmφ in multiple stages. A compressed air addition section is connected to this end, and the hose diameter is connected to the front end of the addition section.
A flexible conduit was made of a rubber hose with a diameter of 62.5 mm and a length of 10 m, and an admixture addition nozzle made of a Y-shaped tube was connected to the end of the conduit, and a spray nozzle was connected at a position 2.5 m from the nozzle.

The compressed air addition section has a total length of 600 mm (straight cylindrical section 200 mm,
The tapered part is 400mm), and there are four oblique blowing pipes, each with an angle of 30 degrees to the straight cylinder part and 15 degrees to the center line.
It was a degree.

The air circuit has the configuration shown in Figure 1, with the constant flow rate control valve on the compressed air addition section set to 5Nm ³ /min, and the constant flow rate control valve on the quick setting agent side set to 2Nm ³ /min.
The pressure regulating valves of each air circuit corresponding to the constant flow rate control valve were set to 5 kg/cm ² and 4 kg/cm ² , respectively.

As a result of continuous construction for 0.5 hours in this condition,
Despite being in a low slump as before,
The amount of dust is always less than 7cm ² /m ³ near the face, and from the face
The amount of rebound is extremely low, less than 4 mg/m ³ at a position of 10 m and less than 4 mg/m ³ at a position of 20 m from the face, and the amount of rebound is always less than 23% at the arch and 12% at the side wall. A lining layer with good adhesion was obtained.

For comparison, the pressure at the compressed air addition section was 3.5 kg/cm using a pressure gauge and an on-off valve without using a fixed flow rate control valve.
cm ² , and the pressure of the addition nozzle was controlled to be 4 kg/cm ² . Despite the presence of 4 personnel, the amount of dust was 14 kg/cm 2 near the face.
mg/m ³ or more, 10 mg/m ³ or more at a position 10 m from the face, and 8 mg/m ³ or more even at a position 20 m from the face, which is very high, and the variation is also large, and the amount of rebound is about 27% at the arch part. , the spraying thickness was high at about 17% on the side walls, and there were large variations in the spraying thickness.

(Effects of the Invention) According to the present invention as described above, the material is pressure-fed from the pump to a predetermined distance through a rigid conduit, air for pressure is added at the terminal position of the rigid conduit, and a flexible conduit is used to reach the spray nozzle. When conveying and blowing with airflow, a constant flow rate control valve is provided upstream of the on-off valve of the pressure-feeding air circuit, and the constant flow rate control valve gives buoyancy to the wet material and admixture, and conveys the wet material and admixture with airflow. The amount of air to be blown is set to be sufficient to keep the dust concentration low, and the amount of air to be blown is controlled to be kept constant according to fluctuations in the discharge pressure of the supply source. Pressurized air is added at the optimum amount of air for the construction. As a result, there is less dust and rebound, and the phenomenon of material separation caused by variations in air volume is prevented, and the amount of material contained per unit air volume is accurately controlled, thereby reducing variations in layer thickness. I can do it. In addition, since it is possible to form the optimal spraying condition and maintain it stably without any skill or experience, the spraying work becomes extremely simple, the number of personnel can be reduced, and unnecessary Since there is no need to consume a large amount of air during construction, the excellent effect of reducing construction costs can be obtained.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing one embodiment of the present invention, Figure 2 is an explanatory diagram showing one embodiment of the present invention.
The figure is a circuit diagram showing another air circuit used in the present invention,
FIG. 3 is a sectional view showing an example of a constant flow rate control valve used in the present invention, and FIG. 4 is a graph showing the correlation between air consumption and dust concentration. 1...Pump for pressure feeding, 2...Rigid pipe line, 4...
Flexible pipe line, 5...Blow nozzle, 6...Compressed air addition section, 7, 7'...Air circuit, 8, 8'...Compressed air supply source, 9, 9'...Fixed flow rate control valve,
10, 10'...pressure regulating valve, 13...pressure sensor.

Claims (1)

[Claims] 1. Materials are pressure-fed from the pump to a predetermined distance through a rigid conduit, pressure-feeding air is added at the end position of this rigid conduit, and when airflow is conveyed to the spray nozzle through a flexible conduit and sprayed, the pressure-feeding air is A fixed flow rate control valve is provided upstream of the on-off valve in the circuit, and the fixed flow rate control valve provides sufficient buoyancy to the wet material and admixture to carry it through the airflow, while also keeping the dust concentration low. A wet spraying method characterized by setting an amount of air and spraying while controlling the amount of air to be kept constant according to fluctuations in the discharge pressure of a supply source.