JPS6313506B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing shotcrete to be layered on tunnel excavation surfaces and the like.

In recent years, in tunnel construction, shotcrete has been used instead of or in combination with the conventional steel arch shoring to prevent the surrounding ground from collapsing.

The role of this shotcrete is to prevent stress concentration by applying it immediately after excavation to smooth out unevenness on the surface of the surrounding rock, and to prevent the rock surface from being exposed to the outside air and weathering. Furthermore, as part of the shoring member, it can be used to prevent the collapse of the ground and to have resistance against earth pressure.

In addition, the desirable conditions for shotcrete construction in tunnels are that the dust associated with spraying does not affect the health or work motivation of workers;
Construction machinery must be as small as possible to avoid congestion in the tunnel, transportation of spraying materials and supply to the spraying machine must be carried out smoothly, and other considerations.
In particular, the quality of concrete after spraying must be ensured.

As the shotcrete construction method, the dry method has traditionally been mainly used, and the wet method has also been sometimes used.

The dry method is the one most commonly used in tunnel construction, and as shown in Figure 6, fine aggregate a, coarse aggregate a' and cement b are mixed in a mixer c.
A quick setting agent e is added when this is supplied to the spraying machine d via an agitator car, and then compressed air from the compressor f is introduced into the spraying machine d and into the material hose g. In this method, the dry mineral material is pumped, and on the way, water h is added to the rock surface by the operation of the nozzle man through the nozzle i at the end of the hose.

However, according to this method, the amount of water added is adjusted depending on the condition of the sprayed surface, so it is difficult to obtain concrete of uniform quality, and it is difficult to obtain concrete because it is in a dry mix condition. The material and cement may not adhere well, and the cement may be pumped in powder form. Furthermore, the water, aggregate, and cement are mixed only near the nozzle, so the mixing time is short. Therefore, when the mixture is insufficiently mixed and the spray collides with a rock wall, there is a problem in that there is a lot of rebounding and generation of dust, resulting in loss of material and poor working environment. On the other hand, since the material is in a dry mix state, it has the advantage that it is easy to pump with compressed air and can be pumped over long distances.

On the other hand, in the wet method, as shown in Figure 7, all materials such as fine and coarse aggregates a and a', cement b, and water h are mixed in a mixer c and then sprayed through an agitator. supply to machine d, compressor f
The quick setting agent e is supplied into the compressed air from the nozzle i and sprayed from the nozzle i.

According to this method, since the materials are thoroughly kneaded before being pumped, quality control is easy and there is almost no separation of materials, which reduces the generation of dust during spraying and the separation of materials. It has the advantage of less rebound, but the distance the material is pumped is short;
The inside of the spraying hose may become blocked by the material, the construction machinery becomes larger, and all materials such as aggregate, water, and cement are mixed in advance, so the time between mixing and spraying is It has drawbacks such as being subject to restrictions, and increasing material loss when spraying a small area in multiple doses.

For this reason, construction methods that incorporate the advantages of both the dry and wet construction methods have recently been developed.
As shown in the figure, fine and coarse aggregates a, a' and cement b
and is dry-mixed in a mixer c and then supplied to a spraying machine d, the required amount of water is added at the outlet thereof, and immediately after that, the required amount of water is pumped with compressed air from a compressor f, or the required amount of water is added to the compressed air. There is a method of adding it and pumping it through a hose as a material for dry mixes.

According to this method, the water and dry mixed material are sufficiently mixed during pressure feeding in the spraying hose, reducing the generation of dust, and the distance of pumping is somewhat longer, but when the spray hits the rock surface, The bounce has not improved. Therefore, a sticky material such as polyethylene oxide is dissolved in the added water, and
A construction method has been developed in which aggregate particles adhere to the wall surface with an adhesive when they collide with the rock surface by spraying, but the adhesive adheres to the inner wall of the hose while being pumped through the hose, and further damage occurs. The fine aggregate and cement adhere to the adhesive, causing the coarse aggregate to separate. Therefore, both aggregates are not ejected evenly from the nozzle, and only the coarse aggregate is ejected first, causing problems in the early stages of spraying. In particular, there are many bounces. In addition, the fine aggregate adhering to the inside of the hose may intermittently harden and eject, and the reaction may give a strong impact to the nozzle man.

This phenomenon occurs because the flow velocity distribution of air and other fluids flowing through tubes such as hoses is faster at the center of the tube and slower at the periphery, so coarse aggregate, which has a large cross-sectional area and is susceptible to pressure, flows toward the center. This occurs because fine aggregate and cement flow to the surrounding area.

In addition, when spraying concrete in tunnels, it is possible to prevent the concrete adhering to the wall surface from peeling off due to its own weight during upward construction, and in addition, in soft ground, it can be applied to ground pressure in a short period of time after spraying concrete. The use of quick setting agent e is essential because it is necessary to develop strength in a short time to make it strong enough to withstand resistance and prevent the ground from collapsing when blasting is performed for the next excavation even in hard rock. This is common to all of the above construction methods.

In order to eliminate the drawbacks of the conventional method described above, the present invention involves applying a sticky solution to fine aggregate and coarse aggregate, and then sprinkling a sufficient amount of cement to form a dry mix material. Thereafter, a method for producing shotcrete is provided, which is characterized by adding an appropriate amount of water and a quick-setting agent to this material.

An embodiment of the present invention will be described with reference to the drawings. First, fine aggregate 1 and coarse aggregate 2 are put into a mixer 3 and both aggregates 1 and 2 are sufficiently stirred and mixed. Next, an appropriate amount of a sticky solution 4 made of a thickener such as polyacrylamide as primary water is added into the mixer 3 and stirred and kneaded together with both aggregates 1 and 2.

In this solution 4, the sum of the surface water of aggregates 1 and 2 and the amount of water in which the thickener is dissolved is the unit water amount required for the desired concrete (the amount of water required to form the desired unit concrete). It is made by dissolving a thickener in an amount of water equal to 1/2 to 3/4 of the weight of the liquid.

When aggregates 1 and 2 and solution 4 are stirred and kneaded, solution 4 adheres to the surfaces of fine aggregate 1 and coarse aggregate 2 as shown in FIG. The aggregates 1 and 2 adhere to each other via the solution 4 to form a mass 5, or the fine aggregates 1 form a mass 6, so that the entire aggregate is bonded to each other.

Next, when the cement powder 7 is added to the aggregate in such a state while being stirred by the mixer 3, the entire unit amount required for the desired concrete is added at once or gradually. Cement 7 is placed in a sticky solution 4 that adheres to the surface of the aggregate.
are gradually mixed, and finally cement 7 appears on the outer surface of the layer of solution 4 adhering to the aggregate surface as shown in Figure 3, and the solution 4 disappears between the particles of aggregate adhering to each other, and the bone Each material has a solution film layer 19 containing cement on its surface, and is separated via the cement 7 attached to the surface of the solution film layer to form independent dry mixture aggregates 1',
2' or fine aggregate 1 around coarse aggregate 2.
Independent aggregates that have a solution coating layer 19 containing cement on their surfaces in a state in which fine aggregates or coarse aggregates are attached to each other, and cement 7 is attached to the surface of the coating layer. The state becomes 8 and 9.

Such a state is caused by the ratio of the amount of solution 4 to the amount of cement 7 and the stirring ability of mixer 3, and the former is preferable, that is, cement is mixed on the surface of individual aggregates 1 and 2. Solution coating layer 19
It is preferable to use a dry mixture with a cement layer attached to the surface of the coating layer, but even in the latter state, it can be used as long as the size of the agglomerated aggregate does not interfere with pressure feeding to the nozzle. .

In this way, after obtaining aggregates 1' and 2' in a dry mix state with solution 4 and cement 7 attached to their surfaces by the dry method, these aggregates 1' and 2' are then transported on a belt conveyor, etc. conveyed by the means 10 from the mixer 3 to the spray machine 11;
put it in. During transportation by this transportation means 10, a fixed amount of quick-setting agent 12 is added evenly to the amount of aggregate.

The spraying machine 11 is connected to and communicated with an air hose 14 to the aggregate outlet portion thereof, which transmits compressed air sent from a separately provided compressor 13, and also conveys the aggregate to the tunnel wall surface 15. A material hose 16 is connected to the sprayer 11 so that a predetermined amount of aggregate fed into the sprayer 11 can be continuously and quantitatively discharged from the outlet. Further, a spray nozzle 17 whose tip is open to the atmosphere is attached to the tip of the material hose 16.

The aggregates 1' and 2' charged into the spray machine 11 are quantitatively discharged from the outlet of the spray machine 11, and the compressed air from the compressor 13 is directed to the open end of the nozzle 17 through the material hose 16. The air flows at high speed, and aggregates 1' and 2' are introduced into this air flow, and the aggregates 1' and 2' are carried from the material hose 16 to the nozzle 17 by the air flow. be. During the flow, that is, the spraying machine 11
Water 18 in a unit amount of water (1/2 to 1/4, which is the remaining amount of the water amount described above) necessary for forming concrete is placed in an appropriate part of the material hose 16 between the nozzle 17 and the nozzle 17 by appropriate means as secondary water. supply
In FIG. 1, the secondary water 18 is supplied to the material hose 16 near the outlet of the sprayer 11.

This secondary water 18 serves to turn the cement 7 adhering to the surfaces of the aggregates 1' and 2' into a cement paste 20.

In this state, it is sprayed onto the tunnel wall surface 15 from the nozzle tip opening.

The fine aggregate 1' sprayed onto the wall surface 15 has a sticky solution 4 on its surface and a layer of cement 7 attached inside and on the solution,
In addition, since the cement is turned into a cement paste by the water 18 on the surface of the layer 19, the adhesiveness of the solution and cement paste and the fact that the solution coating layer 19 acts as a cushion ensure that it does not bounce back. It is attached to the wall surface 15.

In addition, the coarse aggregate 2' also loses repulsive energy in the same way as the fine aggregate, and furthermore, due to the adhesiveness of the solution on the surface of the fine aggregate that adheres to the wall surface 15, the rate of adhesion to each other and rebound from the wall surface is extremely low. Become.

In the above example, fine aggregate 1 and coarse aggregate 2 were both put into mixer 3 and mixed, but as shown in Fig. 5, these aggregates 1 and 2 were mixed separately. Add appropriate amounts of solution 4 and cement 7 to mixers 3a and 3b, respectively.
b, and after stirring and mixing to form fine aggregate 1' and coarse aggregate 2', these may be sent to the mixer 3c and stirred and mixed. Further, when spraying onto the wall surface 15 using only mortar, it is sufficient to form only the fine aggregate 1'.

As described above, in the present invention, a sticky liquid such as a polymer substance is added to the aggregate to be used as a concrete material, and the mixture is stirred and then cement powder is added. A shotcrete method that is characterized by forming a dry mix-like aggregate to which cement powder is attached via a liquid, and then adding an appropriate amount of water and a quick-setting agent to the aggregate to form ready-mixed concrete. Since it is related to the manufacturing method, a sticky solution coating layer containing cement is formed on the surface of the aggregate, and aggregates with a layer of cement powder attached to the surface of the coating layer are formed.
It is in the same state as dry mixed aggregate obtained by dry construction method, and can be smoothly flowed through the pressure hose without clogging it, and a long hose can be used to lengthen the aggregate pumping distance. It is something that can be done. Furthermore, since the cement is adhered in layers to the sticky solution film layer on the aggregate surface, fine and coarse aggregates do not separate, and aggregates do not adhere to the inner wall surface of the hose, which prevents shock from being applied to the nozzle man. Therefore, it is possible to form shotcrete of uniform quality.

In addition, as mentioned above, a sticky solution film layer is formed on the surface of the aggregate, and when the surface cement layer is converted into ready-mixed concrete, an appropriate amount of water is added to form a cement paste. It adheres well to the walls of tunnels, etc., significantly reducing the bounce rate, and in addition, since cement and extremely small fine aggregate are not sprayed independently, they eliminate the generation of dust. It is something that can be done.

Furthermore, the sum of the surface water of the aggregate, the moisture of the viscous liquid, and the amount of water for forming ready-mixed concrete is the amount of water required for the aggregate to be sprayed, and the amount of the surface water that is formed into the dry mixture aggregate. The amount of water for making ready-mixed concrete is automatically determined by adjusting the fluctuation in the unit water amount by the water content of the sticky liquid. Therefore, the quality is better than the conventional method of spraying while adjusting the water amount with a nozzle man It is possible to obtain concrete of good quality.

In addition, when fine aggregate and coarse aggregate are separately kneaded with viscous liquid and cement to form dry mix-like fine aggregate and coarse aggregate, and then both aggregates are mixed, Since dedicated mixers with different capacities can be used when kneading cement, efficient kneading can be achieved.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a block diagram from the manufacturing process to spraying; FIG. 2 is an explanatory diagram showing the sequence of forming the sprayed aggregate in the process of FIG. 3 is an enlarged sectional view of the aggregate in a dry mix state, FIG. 4 is a sectional view of the cement layer of the aggregate in a paste state, and FIG. 5 is a block diagram showing another embodiment of the present invention. 6 to 8 are block diagrams showing conventional construction methods. 1 is fine aggregate, 2 is coarse aggregate, 3 is mixer, 4 is solution, 7 is cement, 10 is conveyor, 11 is spraying machine, 12 is quick setting agent, 13 is compressor,
16 is a material hose, 17 is a nozzle, 1, 2
is dry mixed fine and coarse aggregate.

Claims (1)

[Claims] 1 Add a sticky liquid such as a polymer substance to the aggregate that will become the concrete material, stir and mix it, then add cement powder, stir and mix this, and apply the cement powder to the surface of the aggregate through the sticky liquid. A method for producing shotcrete, which comprises forming adhering dry mix-like aggregate, and then adding an appropriate amount of water and a quick-setting agent to the aggregate to form ready-mixed concrete.