JPH0554519B2 - - Google Patents

Description

[Detailed Description of the Invention] "Field of Industrial Application" This invention relates to an air-based cement grout material (hereinafter referred to as "air grout") used for backfilling of tunnels, etc., and a backfilling method using the same. It is related to.

``Conventional technology'' Conventionally, one-component grout (a method in which air grout mixed in a mixer is pumped using a single pump) is inexpensive and easy to work with for backfilling mountain tunnels and filling cavities with large gaps. A type of air grout is used. However, one-component air grout (usually containing about 30 to 60% air) has the following defects when injected into the ground behind a tunnel.

(1) Because it is in a fluid state, it escapes to unnecessary distances.

(2) When it comes into contact with groundwater, etc., material separation and air reduction phenomena occur.

(3) If the grout is poured too high at once, the weight of the grout will cause a volume change (reduction of air).

Due to the above defects, it is difficult to obtain uniform consolidation strength of the grout, resulting in poor injection rate (yield).

Therefore, in order to solve these defects, two-component grout, which is made by adding water glass solution to one-component air grout and gelling (hardening) in a short period of time (usually about 10 to 30 seconds), has recently been put into practical use. has been done.

Compared to one-component grout, this two-component grout (1) has a shorter gelation time, so it can be injected into a limited range;

(2) After gelling, the grout is not affected by groundwater.

(3) There is no change in volume (reduction in air) due to the grout's own weight after gelling.

(4) Allows for a longer curing time.

(5) Can provide early strength if necessary.

The following points will be improved.

``Problems to be solved by the invention'' However, until it is injected into the ground, air grout itself is in a relatively stable fluid state with no material separation or breathing, but by adding liquid water glass to it, , the following new fatal problems arise.

(1) Even if the gelation time is short (about 10 to 30 seconds), the foaming of the grout becomes unstable due to a decrease in viscosity during the very short time it takes to gel. The phenomenon of material separation and bubble reduction takes place.

(2) Before it gels, it is diluted when it comes into contact with groundwater, and similar to one-component air grout, material separation and bubble reduction occur.

The phenomena (1) and (2) above are impossible unless the gelation time is instantaneous (0 seconds in terms of gelation time), but as long as water glass is used, it is not possible to make the gelation time instantaneous. .

For this reason, the two-component grout, in which water glass is added to air grout, has a very poor injection rate (yield) and is currently not being used much anymore.

"Means for Solving the Problems" In order to prevent the above-mentioned two-component phenomena (1) and (2), the present invention uses an aluminum salt solution instead of water glass and uses a one-solution fluid grout. It transforms into a plastic grout, prevents material separation and bubble reduction, and does not dilute into groundwater.
Furthermore, we propose a two-component air grout that can be injected into a limited range.

In addition, the grout exhibiting a plastic state as used in the present invention refers to a grout having thixotropic properties, which means that the grout stands on its own in a stationary state and becomes fluidized like a liquid when pressurized. It is usually called plastic grout.

The aluminum salts used in the present invention include aluminum sulfate, alum, aluminum chloride, polyaluminum chloride, and other acidic water-soluble aluminum salts.

These aluminum salts form a precipitate in the form of aluminum hydroxide Al(OH) ₃ instantly (zero gel time) when mixed with dissolved alkali (mainly calcium hydroxide) from cement.

The present invention utilizes the property of instantly producing aluminum hydroxide between an acidic aluminum salt and an alkaline cement suspension, etc., by adding an aluminum salt solution to fluidized air grout. , the grout instantly transforms into a plastic-like grout, and as a result, the air in the grout is confined within the grout, so even if it is a two-component type, the air bubbles are in a very stable state, resulting in material separation and air bubble formation. The decline phenomenon is prevented,
It also eliminates the effects of dilution into groundwater.

In addition, the present invention is a grout that eliminates the defects of conventional two-component water glass air grout, such as making it plastic, which makes it possible to inject into a limited area, and eliminates the phenomenon of air bubbles decreasing due to the grout's own weight. It is.

The air grout used in the present invention is mainly air milk, which is made by sufficiently stirring a foaming agent and water with a mixer to generate air bubbles, and adding cement to this.
Furthermore, there are air mortar, etc., which are made by adding aggregate to this.

The aggregate used in this air mortar is sand with a relatively small particle size or fine powder containing clay minerals.

Further, foaming agents include animal proteins and surfactants, and any foaming agent can be used in the present invention.

The aluminum salt used in the present invention is preferably as low in acidity (high in PH) as possible since it is not affected by cement.

Further, by using an alkaline agent such as lime in addition to cement, the influence of aluminum salt on cement can be prevented.

The injection method of the present invention is mainly a two-component type, in which liquid air grout containing a foaming agent and cement is used as liquid A, and an aluminum salt solution is used as liquid B.
Liquids A and B are pumped using separate pumps, and are combined in front of the grout hole to inject plasticized grout.

Furthermore, depending on the plastic state (relatively weak) or the performance of the pump, it is also possible to inject a single component.

The composition of the two-component air grout (liquid A + liquid B) used in the present invention is not particularly limited as long as it produces a plasticized grout, but the amount of water in the grout of liquid A is 300 to 4001/ ^m3 Below, the concentration of liquid B (aluminum salt) is 6 to 8 in terms of Al ₂ O ₃ .
% or more, and the amount of B liquid added to A liquid is preferably about 4 to 15%.

"Examples" The present invention will be described in detail below with further examples.

The materials used in the experiment were ordinary cement, sand (standard sand), clay mineral fine powder (trade name Minosoil), surfactant foaming agent (trade name Setstomics), and JIS3.
No. water glass and sulfuric acid band solution (8.1 in terms of Al ₂ O ₃
%) was used.

Experimental example: Put 790 c.c. of water and 4.4 cc of foaming agent into a mixer and stir to generate air bubbles.
Injecting 1200g, flow value (P funnel) 19.2 seconds,
Air amount 41.3%, raw capacity 997g/, grout amount
Obtained 2000c.c. of air milk.

Experimental example Similar to the experimental example, 562cc. of water and 2.0cc of foaming agent were placed in the mixer and stirred to generate bubbles, then 600g of cement and 1290g of sand were added, the flow value was 21.4 seconds, and the air bubbles were generated. Volume 37.4%, raw capacity 1227
g/g of air mortar was obtained.

Comparative example 500 c.c. of air milk obtained in the experimental example was placed in a polyethylene bag with a diameter of 7 cm and a length of 50 cm, and 100 c.c. of water glass solution (50% liquid) was poured into it, and at the same time it was vigorously heated for 2 to 3 seconds. After stirring, the mixture turned into a gel in 9 seconds when the mixture was stopped.

The amount of gelled grout was 522 c.c.

It can be seen that the reduction rate of air at this time was extremely large at 38%, indicating that the yield was poor.

Furthermore, when the gelled grout was examined, it was found that the lower part contained more cement and less air, while the upper part contained less cement and had more air, resulting in material separation.

On the other hand, the air mortar of Experimental Example 2 was mixed with 500 c.c. of the water glass solution in the same manner as the above air milk with 75 c.c.
When the grout was added, it gelled in 13 seconds, and the amount of gelled grout was 557 c.c.

At this time, the air reduction rate was extremely large at 23%, indicating that the yield was poor.

In addition, when the gelled grout was examined, it was confirmed that there was a large amount of sand and cement in the lower part, and less in the upper part, and complete material separation had occurred.

Example 500 c.c. of air milk obtained in the experimental example was placed in a polyethylene bag as in the comparative example, and 75 c.c.
It instantly lost its fluidity (it did not flow even when the bag was turned upside down).

The amount of grout that lost fluidity was 565 c.c.

It can be seen that the air reduction rate at this time is extremely small, 5%, and is within the error range.

Furthermore, when the grout that had lost its fluidity was pressed by hand at the bottom of the bag, the grout easily moved to the top. (This phenomenon causes grout to have a plastic appearance.) When we examined the plasticized grout, we found that cement and air bubbles were evenly distributed from the bottom to the top.
There was no material separation at all.

On the other hand, when the air mortar of Example 2 was added to 500 c.c. in an amount of 65 c.c. in the same manner as the air milk, it instantly became plastic.

The amount of grout that became plastic was 558 c.c.

It can be seen that the air reduction rate at this time is extremely small at 3%.

Furthermore, when the plasticized grout was examined, cement, sand, and air bubbles were uniformly dispersed from the bottom to the top, and there was no material separation at all.

In the comparative example, in the absence of the above water, adding water glass to the air grout lowers the viscosity of the grout and makes it unstable, causing cement and sand (aggregate) with heavy specific gravity to settle to the bottom. ,
It can be seen that the reduction rate of air was extremely large because most of the light air rose to the top and escaped to the outside of the grout.

It can also be seen that grouts with poor yields also have large material separation, resulting in non-uniform strength, which is a very problematic grout.

In contrast, in the present invention, when an aluminum salt solution is added to liquid air grout, the air in the grout is instantly changed into a plastic state, thereby trapping the air in the grout, causing almost no reduction in air, and material separation. It can be seen that uniform strength can be obtained because there is no

Example: After putting 95% of water and 0.55% of foaming agent into a mixer and stirring to generate bubbles, 75kg of cement and 75g of fine clay powder were added, resulting in a flow value of 20.7 seconds and air volume.
40.1% air mortar was used as liquid A.

Separately, sulfuric acid chloride 25 was prepared as B solution.

When both AB liquids were pumped with an injection pump at a ratio of 10:1 (discharge rate 10 per minute for both AB liquids, hose length 3 m after AB liquid combined) and discharged 100% into water,
The plasticized grout formed into a mountain shape (approximately 35 degrees of inclination angle) without being diluted with water.

When I later investigated the air reduction rate in the grout.
The amount was extremely low at 3.5%, and the caking rate (estimated) was 98%, meaning that almost all of the amount was caking, and there was no material separation at all.

Note that the inclination angle represents grout that exhibits a plastic shape, and fluid grout has almost no inclination angle and is flat.

Comparative Example Air mortar with the same composition as in the example (flow value 21.2 seconds, air amount 41.5%) was used as liquid A, and a water glass solution (70% liquid) 25 was separately prepared.

Injection was carried out under the same conditions as in the example (both AB solutions were mixed at 10:
When the grout was released into water (it had not yet gelled at the time of release) at a ratio of 1 and gelation time (12 seconds), the grout was diluted with water, and the air escaped into the water and rose to the surface of the water.

Furthermore, the shape of the injected grout was almost flat (angle of inclination of about 5 degrees).

Later, the reduction rate of air in the grout was extremely high at 40.8%, and the consolidation rate (estimated) was a very small value of 51% (the difference between the consolidation rate of grout and the decrease rate of air is Grout (excluding air) that has been diluted with water and not solidified).

Further, when examined after consolidation, it was found that there were many aggregates and cement parts at the bottom, and there was a large amount of air at the top, causing material separation and non-uniformity.

In the comparative example, when the above amount of water exists (in water), when air grout and water glass are combined, the viscosity of the grout decreases and becomes unstable, and if it is released into water without gelation, material separation may occur. , the cement and aggregate settle, the air escapes (reduces) into the water, and the grout, excluding the air, is further diluted with water.

As a result, the amount of air decreases and the solidification rate becomes extremely large, which is a fatal defect for air grout.

In contrast, in the present invention, when the air grout and the sodium sulfate solution are combined, the grout instantly transforms into a plastic-like grout, and the air in the grout is released into the water while being confined within the grout. It can be seen that there is no dilution, material separation does not occur, the air reduction rate and consolidation rate are extremely excellent, and furthermore, limited injection is possible.

``Effects of the Invention'' As described above, according to the present invention, an aluminum salt solution is added to fluidized air grout containing a foaming agent and cement to change the quality of the grout into a plastic-like grout. It is not affected by ground water, there is no volume change (reduction in air bubbles) due to the grout's own weight, and there is no material separation or air bubble reduction due to the two-component property.
We can provide grout that has excellent properties as a backfill grout material, cavity filling, and other injection materials, and by injecting this grout, you can perform reliable backfill construction. .

Claims (1)

[Claims] 1. Adding an aluminum salt solution to fluidized air grout containing a foaming agent and cement to instantly generate aluminum hydroxide, and grouting the air in the grout that has changed to a plastic state. Air grout material characterized by being sealed inside. 2. Fluid air grout containing a foaming agent and cement is used as liquid A, and an aluminum salt solution is used as liquid B. Liquid A and liquid B are pumped using separate pumps and merged in front of the grout hole. A backfill injection method that is characterized by instantly generating aluminum hydroxide and transforming it into a plastic grout to confine the air in the grout, and then injecting air grout that confines this air.