JP4386280B2 - Rapid setting concrete spraying method and spraying apparatus used therefor - Google Patents

Description

  The present invention relates to a rapid setting concrete spraying method and a spraying apparatus used therefor.

  Conventionally, concrete spraying methods have been used to reinforce natural ground in tunnel excavation work and stabilize the excavation surface. For example, it is sent from a compressor into a transport pipe that transports concrete sent by a piston pump or the like. A method is generally used in which compressed air is supplied and concrete is pneumatically transported, and a concrete is rapidly sprayed from a spray nozzle after the rapid-setting material is supplied and the concrete and the rapid-setting material are mixed.

  The concrete is then transported, for example, by a piston pump through a transport pipe to a joining pipe, and compressed air sent from a compressor is supplied to the branch pipe of the joining pipe, and the concrete is supplied to the joining pipe through the transport pipe. In addition to transporting, the quick-connecting material that is pneumatically transported from the quick-connecting material supply facility is supplied to the branch pipe of the merging pipe, and the concrete and the quick-setting material are mixed together. A method of spraying on the attachment surface has been proposed (see Patent Document 1).

  In addition, an annular quick setting material pressure adjustment tank is attached to the outer periphery of the material pressure feeding pipe connected to the middle of the material hose, which feeds dry mix concrete from the spraying machine to the spray nozzle, and the quick setting material pressure adjustment An air pressure adjustment tank is attached to the front part of the tank, and a plurality of quick-setting material addition pipes and air pressure feed pipes are branched from the outer side of the front side surface of each tank. In sprayed concrete, which is connected to the pressure feeding pipe in an inclined state, a spray nozzle is provided in the quick setting material addition pipe, and the quick setting material hose and air hose are connected to the quick setting material pressure adjustment tank and the air pressure adjustment tank, respectively. An apparatus for adding a liquid admixture has been proposed (see Patent Document 2).

  However, these spraying methods are methods in which only compressed air is supplied to the branch pipe of the first merging pipe, and further improvement in the dust reduction effect has been desired.

Furthermore, there has been proposed a sprayed concrete construction method in which water is supplied to the concrete and the quick setting material that are pumped in the pipe to mix the powder quick setting material and the concrete (see Patent Document 3).
However, this spraying method cannot obtain a sufficient dust reduction effect, and further improvement of the dust reduction effect has been desired.

JP 2000-297600 A Japanese Patent Publication No. 06-004981 Japanese Patent Laid-Open No. 2004-092211

  The problem to be solved by the present invention is to improve the dust reduction effect.

The present invention transports the kneaded concrete to the first junction pipe (1) through the first transport pipe (6), and supplies a mixture of compressed air and water from the branch pipe (2) of the first junction pipe. The concrete is pumped concrete, and the concrete is pumped to the second junction pipe (3) through the second transport pipe (7), and the calcium aluminate rapid setting material is supplied from the branch pipe (4) of the second junction pipe. A quick setting concrete spraying method characterized in that quick setting concrete is sprayed from a spray nozzle (5) through a third transport pipe (8), wherein the branch pipe (2 The pressure of the mixture of compressed air and water supplied from) is 0.8 to 2 MPa, and the total amount of compressed air supplied to the first merging pipe (1) and the second merging pipe (3) is an atmospheric pressure conversion value. in 10~13m ³ / min Ah is, as a second transport tube (7), an inner diameter of 55 to 105 m, is used as follows 12m length, as a third transport tube (8), inner diameter 55～105Mm, in spraying method rapid setting concrete in length which comprises using those 6m below Yes, a spraying device used in the spraying method.

  According to the method of the present invention, the dust reduction effect is improved, the mixing property between the quick setting material and the concrete is improved, and the initial strength is enhanced. The amount of water mixed with the compressed air is reduced. By adjusting, there is an effect of reducing troubles caused by blockage during spraying.

The present invention is a spraying method in which kneaded concrete is mixed with a quick setting material via a transport pipe or a merge pipe and sprayed, and a spraying apparatus used in the method.
Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

  FIG. 1 shows a configuration example of a concrete spraying apparatus used in the method of the present invention.

In the present invention, for example, the concrete is kneaded by a commercially available mixer, then supplied to the piston pump, transported through the first transport pipe 6 by the piston pump, and transported to the first junction pipe 1.
As the concrete used in the present invention, ordinary concrete can be used and is not particularly limited.
Also, concrete containing steel fibers can be used.
The amount of cement in the concrete is not particularly limited, but is usually 600 kg / m ³ or less in terms of cement unit.

  In the first merging pipe 1, the transported concrete and a mixture of compressed air and water are merged and mixed to form a pressure-feed concrete.

  The mixture of compressed air and water merges with concrete in the first merge pipe 1.

Although the supply amount of compressed air is not particularly limited, it is usually preferably 4 to 14 m ³ / min. If it is less than 4 m ³ / min, the pumpability of concrete may be poor and the workability may deteriorate, and if it exceeds 14 m ³ / min, dust generation by compressed air may increase and the amount of dust may increase.

  The amount of water supply varies depending on the amount of concrete pumped and cannot be uniquely determined, but is preferably 1 to 50 liters / minute. If it is less than 1 liter / minute, there may be no effect of using water together. If it exceeds 50 liter / minute, the water may be too much and the strength may decrease.

  In the concrete spraying method of the present invention, the pressure of the mixture of compressed air and water supplied to the branch pipe 2 of the first merge pipe is preferably 0.1 to 2 MPa, more preferably 0.3 to 0.8 MPa. If the pressure is less than 0.1 MPa, the pressure is too low and it is easy to add, so there may be a lot of air and dust will increase. If the pressure exceeds 20 MPa, the pressure is too high and it may be difficult to add and the effect may not be obtained.

  In the first merging pipe 1, the pressured concrete supplied with the mixture of compressed air and water is increased in speed in the second transport pipe 7 due to the expansion and flow of the compressed air and dispersed to the second merging pipe 3. Pump.

  In the second merging pipe 3, the pumped concrete that has been pumped and the quick-setting material that has been pumped are merged and mixed to form quick-setting concrete.

The quick setting material is pumped from the branch pipe 4 of the second merging pipe to the second merging pipe 3 through the quick setting material transport pipe by a quick setting material supply device (not shown).
For example, a hose having a diameter of 3 / 4B or 1B can be used as the quick setting material transport pipe.

As the quick setting material, a known powder, liquid or slurry, for example, calcium aluminate, aluminum salt such as sodium aluminate or aluminum sulfate, or these and carbonate as a main component. And a mixture thereof.
The amount of the quick setting material is preferably 15 parts or less with respect to 100 parts of cement in the concrete. Even if it exceeds 15 parts, the effect of addition may not be obtained.

  The quick setting concrete to which the quick setting material is added is pumped through the third transport pipe 8 while being mixed with the quick setting material by the expansion and flow of the compressed air, and is discharged from the spray nozzle 5, and on the spray surface. It is sprayed on a certain ground.

In the present invention, the total amount of compressed air supplied to the first merging pipe 1 and the second merging pipe 3 is preferably 8 to 18 m ³ / min, more preferably 9 to 13 m ³ / min in terms of atmospheric pressure. If it is less than 8 m ³ / min, the amount of air is insufficient, the concrete is insufficiently compacted against the sprayed surface, and it may be difficult to obtain the strength. Also, the pumpability of the concrete deteriorates and the concrete is blocked in the piping. In some cases, exceeding 18m ³ / min may result in excessive rebound and dust due to excessive air pressure.

The material of the transport pipe used in the present invention is not particularly limited, but usually rubber or iron is used.
The material of the junction pipe is not particularly limited, but usually iron is used.

  In the present invention, the second transport pipe 7 has an inner diameter of 55 to 105 mm and a length of 12 m or less, and the third transport pipe 8 has an inner diameter of 55 to 105 mm and a length of 6 m or less. Preferably, the second transport pipe 7 has a length of 7 m or less, and the third transport pipe 8 has a length of 3 m or less. If the inner diameter and length of the second transport pipe 7 and the third transport pipe 8 are outside this range, the pressure of the compressed air supplied to the branch pipe 2 of the first merge pipe and the total amount of compressed air are in an appropriate range. It may be difficult to make adjustments. For example, if the inner diameters of the second transport pipe 7 and the third transport pipe 8 are smaller than 55 mm, the transport resistance of the concrete is too large, and in particular, when concrete with low fluidity is used, the transport pipe may be blocked. In some cases, only soft and highly fluid concrete can be used. Conversely, if the inner diameter of the second transport pipe 7 or the third transport pipe 8 is larger than 105 mm, the volume ratio of air in the transport pipe increases. The loss of the quick setting material increases, and a large amount of compressed air is required, which necessitates an increase in the size of the compressor and increases the cost of the apparatus. In addition, if the length of the second transport pipe 7 exceeds 12 m, the transport resistance of the concrete increases, and in particular, if concrete with low fluidity is used, the concrete may be clogged in the transport pipe. However, if the length of the third transport pipe 8 exceeds 6 m, the transport resistance of the concrete increases and the time until the concrete is discharged from the spray nozzle 5 increases. As a result, the hardening of the concrete proceeds, and the concrete may be easily blocked in the spray nozzle 5.

  In addition, the 2nd transport pipe 7 and the 3rd transport pipe 8 can also be abbreviate | omitted depending on the case, and the 1st confluence | merging pipe 1, the 2nd confluence | merging pipe 3, and the spray nozzle 5 can also each be connected directly. It is.

As the piston pump used in the present invention, a commercially available one can be used. As a typical example, a concrete discharge capacity of about 25 m ³ / h at the maximum and a concrete discharge amount that can be adjusted by the piston speed is preferable. .

  The spray nozzle 5 is generally a tapered tube whose diameter is reduced as it goes to the outlet, and the taper angle may be about 0.5 degrees. The diameter of the outlet portion of the spray nozzle 5 is preferably about 50 mm.

  Hereinafter, the present invention will be described in detail by experimental examples.

Experimental example 1
The concrete spraying device shown in FIG. 1 was assembled.
The inner diameter of the second transport pipe 7 and the third transport pipe 8 is 65 mm, and the lengths of the first transport pipe 6 are 15 m, the second transport pipe 7 is 3 m, and the third transport pipe 8 is 1 m. did.
Further, the spray nozzle 5 was used which was narrowed from an inlet diameter of 65 mm to an outlet diameter of 50 mm.
For the concrete used for spraying, the unit amount of each material is 400 kg / m ³ cement, 200 kg / m ³ water, 63% fine aggregate, and 1.0 part of water reducing agent is used for 100 parts of cement. did.
The slump value of this concrete was 18 cm.
Nine parts of the quick setting material was used for 100 parts of cement in the concrete, and the amount of water supplied to the branch pipe 2 of the first merge pipe was 5 liters / minute.
Concrete was sprayed with the pressure of the mixture of compressed air and water shown in Table 1 and the total amount of compressed air, and the amount of dust, rebound rate, and compressive strength were measured, and the transportability and finished surface were evaluated. The results are also shown in Table 1.
For comparison, when only compressed air is supplied instead of a mixture of compressed air and water, a quick setting material is used instead of the mixture in the first joining pipe, and a quick setting material is used in the branch pipe of the second joining pipe. A comparative example in which water was supplied at 5 liters / minute was also performed in the same manner. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, Blaine specific surface area 3,200cm ² / g, specific gravity 3.16
Fine aggregate: River sand from Himekawa, Niigata Prefecture, surface water ratio 4.0%, specific gravity 2.61
Coarse aggregate: Gravel from Himekawa, Niigata Prefecture, surface dry state, specific gravity 2.65, maximum dimension 10mm
Quick setting material: Calcium aluminate type quick setting material, commercial water reducing agent: Polycarboxylic acid type high performance water reducing agent, commercial product

<Evaluation method>
Dust amount: Measured at a fixed position of 3 m after spraying 10 minutes after spraying Rebound rate: Spray 1m ^{3 of} prepared quick setting concrete at a spraying speed of 10m ³ / h, and adhere after finishing spraying Measure the amount of concrete dropped on the vinyl sheet placed on the floor without rebound rate = (mass of concrete dropped without sticking during spraying) / (total mass of concrete used for spraying) X Transportability calculated from the formula of 100 (%): The transport status of concrete was observed. The case where the merging pipe or the transport pipe is not clogged is marked as “◯”, the case where the concrete is discharged intermittently due to clogging, and the case where the merging pipe or the transport pipe is clogged and cannot be sprayed are marked as “X”.
Finished surface: The finish surface of shotcrete, the case where the concrete thickness is uniform and smooth, ○, and the case where the concrete finish surface is uneven are marked with ×.
Compressive strength: The compressive strength of 1 hour and 1 day of age is that the pin installed in the pullout formwork of width 25cm x length 25cm is covered with sprayed concrete from the pullout formwork surface, and the pin is applied from the back of the formwork Pull out, determine the pull-out strength at that time, calculate from the formula of compressive strength = (pull-out strength) x 4 / (test specimen contact area), and the compressive strength at 7 days and 28 days of age is 50 cm wide x length Concrete was sprayed on a 50cm x 20cm thick formwork, and the sampled specimen 5cm in diameter x 10cm in length was measured with a 20-ton pressure machine.

It is a schematic diagram which shows the example of 1 structure of the concrete spraying apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st merge pipe 2 1st merge pipe branch pipe 3 2nd merge pipe 4 2nd merge pipe branch pipe 5 Spray nozzle 6 1st transport pipe 7 2nd transport pipe 8 3rd transport pipe

Claims (2)

The kneaded concrete is transported to the first merge pipe (1) through the first transport pipe (6), and a mixture of compressed air and water is supplied from the branch pipe (2) of the first merge pipe to make a pressure-feed concrete. The concrete is pumped to the second merging pipe (3) through the second transport pipe (7), and the calcium aluminate quick setting material is supplied from the branch pipe (4) of the second merging pipe to rapidly set the concrete. And spraying from the spray nozzle (5) through the third transport pipe (8), the quick setting concrete spraying method, being supplied from the branch pipe (2) of the first merge pipe The pressure of the mixture of compressed air and water is 0.8 to 2 MPa, and the total amount of compressed air supplied to the first joining pipe (1) and the second joining pipe (3) is 10 to 13 m in terms of atmospheric pressure. ³ / min Ah is, as a second transport tube (7), an inner diameter of 55～105Mm, length Used as following 12m, as the third transport tube (8), an inner diameter of 55～105Mm, spraying method rapid setting concrete in length which comprises using those 6m below.   The spraying apparatus used with the spraying method of the quick setting concrete of Claim 1.

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