JPS5817516B2 - Doshitsu Antei Kahou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing soil quality using a silicate grout using carbon dioxide gas as a hardening agent.

Conventionally, grouting methods have been known in which various chemical solutions are injected into the soil and gelled in the soil in order to strengthen soft ground or stop leaking ground. is the main ingredient, and this and a hardening agent are combined.
So-called silicate-based grouts have the advantage of being inexpensive and less likely to cause pollution than other chemical grouts, so they are widely put into practical use.

Various substances belonging to acids, acid salts, or water-soluble polyvalent metal salts have been proposed as hardening agents for silicate grout, but conventional hardening agents are difficult to handle due to strong acidity or are expensive. There are many things that have shortcomings.

The present invention attempts to stabilize the soil quality using a silicate grout using a hardening agent different from the conventional one.

The technology of gelling a sodium silicate aqueous solution with carbon dioxide gas is well known in the field of manufacturing molding sand for metal casting, and this technology involves mixing a sodium silicate aqueous solution with molding sand, molding it, and then blowing carbon dioxide gas into it. By reaction, Na2SIO3+XH2O+C02→Na2CO3+5
102. This is not an economical way to use carbon dioxide as there is a lot of escape loss.

The present inventors believe that carbon dioxide gas is harmless and cheaper than conventional silicate-based cloud curing agents, and that carbon dioxide gas is simply sprayed onto a molded body made of sodium silicate aqueous solution and sand as in the above technology. However, since mold sand is strong enough to withstand the weight of molten metal and has great effectiveness as a hardening agent, it was discovered that it is suitable as a hardening agent for silicate grout, and various studies are being conducted on its practical application. However,
Carbon dioxide gas is a gas and has low solubility in water, so when it is used as a hardening agent for silicate grout, the grout is prepared by mixing the main agent and hardening agent under normal pressure as in the past. I realized that this method was inappropriate.

In other words, the conventional method for applying silicate grout in O-hole is the so-called two-component system chemical injection method, in which the main agent and hardening agent are mixed in separate mixing tanks (normal pressure open tanks) before construction. The most common method is to prepare an aqueous solution with an appropriate concentration suitable for In this case, this method is applied because the solubility of carbon dioxide gas in water is small (0,145, F CO2/100 gH20, normal pressure, 25°C), and it is not possible to create an aqueous hardening agent solution with a practical concentration. I can't.

Another construction method is the so-called one-liquid chemical injection method, in which the base agent and curing agent are made into an aqueous solution in the same tank (normal pressure open tank) and then immediately injected into the soil. According to this method, a practical grout can be obtained even when carbon dioxide gas is used as a curing agent, but if carbon dioxide gas is blown into a silicate sorter aqueous solution at room temperature and pressure, carbon dioxide gas It takes a long time to prepare a grout with a short gel time (several minutes), which is slow to dissolve in an aqueous sodium silicate solution and requires a large amount of carbon dioxide gas.

Note that the gel time refers to the time from the end of blowing carbon dioxide gas until the grout gels.

For example, JTS No. 3 Sodium silicate: Water = 1:3 (
When carbon dioxide gas is blown into a normal silicate sorter aqueous solution for soil stabilization at a ratio of 100% by volume at room temperature and under normal pressure, there is no continuous loss of carbon dioxide gas into the atmosphere in order to obtain grout with a gel time of several minutes. It takes more than 60 minutes to slowly blow in the water.

In this case, if the amount of carbon dioxide gas blown is increased, the desired grout can be obtained in a shorter time, but in such a case, the loss of carbon dioxide gas escaping into the atmosphere is large, which is uneconomical.

For example, the same aqueous sodium silicate solution as above. If you try to obtain a grout with a gel time of several minutes by injecting carbonate scum for a few minutes, most of the carbonate scum (80%)
(above) will escape into the atmosphere without being dissolved in the liquid.

In view of this, the present inventors conducted various research in order to find a method to obtain grout with a short gel time without loss of carbon dioxide gas in a short period of time. When an aqueous solution and carbon dioxide gas are supplied and the liquid phase is stirred while the tank is being pressurized from the supplied carbon dioxide gas Q, the carbon dioxide gas quickly dissolves in the liquid phase of the sodium silicate aqueous solution, and for a short period of time. It is possible to obtain a grout with a short gel time in a short period of time, and by following this formulation method, it is possible to utilize the increased pressure in the tank when injecting the grout adjusted to the desired gel time into the soil. We have discovered that soil quality can be advantageously stabilized without the need for an injection pump as in the conventional method, leading to the present invention.

That is, the present invention provides an aqueous solution of sodium silicate and carbon dioxide gas in a sealed pressure-resistant tank equipped with a stirrer, and maintains the inside of the tank in a low pressure state with the supplied carbon dioxide gas and stirs the liquid phase. A grout is prepared by dissolving carbon dioxide gas in an aqueous solution of sodium silicate as a phase, and then the resulting grout is discharged from the tank using increased pressure inside the tank and injected into the soil, where it forms a gel. Soil stabilization method using silicate grout using carbon dioxide as a hardening agent
The main points are as follows.

The drawings are flow sheets showing embodiments of the present invention, and the present invention will be described below with reference to the drawings.

First, a sodium silicate aqueous solution (water glass) and water for further diluting it (accordingly) are pumped into grout mixing tank 3 (hereinafter abbreviated as mixing tank 3) Q using dedicated pumps 1' and 2', respectively. supply

Water is used as appropriate depending on the construction conditions, and water is used in normal construction (for example, if JT83 sodium silicate is used as an aqueous solution of sodium silicate, JT
S No. 3 sodium silicate is diluted with 2 to 3 times the volume of water, but depending on the construction, it may not be diluted.

The amount of sodium silicate and water to be charged may be arbitrary, but it is usually preferable to charge 50 to 80% of the effective internal capacity of the mixing tank 3.

The mixing tank 3 is equipped with an agitator, a pressure gauge, a raw material supply hole, a product (grout) discharge hole, and other automatic control devices to facilitate operations such as supplying raw materials, mixing grout, and discharging products as necessary. It is preferable that the tank has a sealed pressure-resistant structure and that the speed of the attached stirrer can be changed, and that the stirring blades can be any type of stirrer that allows the raw materials (sodium silicate aqueous solution and carbon dioxide gas) in the tank to be well mixed. Any shape is fine, but for example 1
A paddle-shaped blade with tiers or more, a 45-degree twisted three-way propeller blade, etc. are suitable.

After charging the aqueous sodium silicate solution (and water) into the mixing tank 3ζ, carbon dioxide gas is supplied to the mixing tank 3 from the carbon dioxide gas storage tank 4 (usually a liquefied carbon dioxide cylinder) (or at the same time as the charging).

The flow rate of carbon dioxide gas is regulated by a flow rate (pressure) control valve 4'.

Usually, when mixing gas and liquid, a method is adopted in which gas is blown into the liquid using a suitable blowing pipe, but in the carbon dioxide gas-sodium silicate aqueous solution mixing system in the present invention, especially It is not necessary to blow carbon dioxide gas into the aqueous sodium silicate solution, and simply supplying carbon dioxide gas to the gaseous phase while stirring the liquid phase in the mixing tank 3 is sufficient to achieve the purpose.

%, the latter case is advantageous in terms of operation because there is no risk of grout gelling and clogging in the blowing pipe, as occurs in the former case.

As is clear from the fact that the solubility of gas in liquid increases as the pressure increases, as the amount of carbon dioxide gas supplied increases and the pressure within the mixing tank 3 increases, the solubility of carbon dioxide gas in the sodium silicate aqueous solution increases. Dissolution into the medium is accelerated.

Furthermore, the dissolution of carbon dioxide into the sodium silicate aqueous solution may be accelerated even if the stirring state in the mixing tank 3 is set such that the carbon dioxide gas and the sodium silicate aqueous solution are mixed better, for example, when the rotational speed of the stirrer is increased. It will be done.

For this reason, adjusting the grout gel time is
Usually, it is appropriate to carry out the reaction by varying the amount of carbon dioxide gas supplied (the internal pressure of the tank) and the stirring rotation speed.

For example, an autoclave with a capacity of 21 and equipped with a stirrer is charged with 11 of a sodium silicate aqueous solution at a ratio of 1:3 (volume) using a JT83 silicate sorter, and while the liquid phase is stirred, 22 carbon dioxide gas is added to the gas phase. When mixing the grout by supplying it for a minute,
Table 1 shows the results when the internal pressure of the tank and the stirring rotation speed were varied.

As shown in Table 1, grout with any long or short gel time can be prepared in a short time by appropriately selecting and combining the internal pressure in the mixing tank and the stirring rotation speed.

The time for supplying carbon dioxide gas to the mixing tank 3 (time for mixing the sodium silicate aqueous solution and carbon dioxide gas) is usually 1 to 2 minutes.

The grout, which has been adjusted to the desired gel time, is discharged from the tank by the increased pressure within the tank and injected into the soil before it gels.

Note that it takes some time to drain the grout, depending on the speed, so the grout injection into the soil should be completed in a time shorter than the gel time so that the grout does not gel in the tank and injection pipe during draining. Kokichi is necessary.

Grout injected into the soil gels in the soil and stabilizes the soil.

The present invention can be carried out not only in a diagonal batch mode but also in a continuous manner.

In other words, the raw materials (sodium silicate aqueous solution) and carbon dioxide gas are continuously supplied from their respective storage tanks to the mixing tank, and are allowed to remain in the tank for an appropriate time to form a grout with the desired gel time.
After this is mixed, it is continuously discharged outside the tank and injected into the soil.

Needless to say, the amount of each raw material supplied, residence time, etc. at this time should be set appropriately so that a grout with the desired gel time can be obtained.

This continuous method allows large amounts of grout for large-scale construction work to be mixed in a small-capacity mixing tank and then injected into the soil.

In addition, in the implementation work ζ, the mixing tank 3 has an internal capacity of 50 to 10
0 l, pressure resistant within 50 kg/i (gauge pressure) is usually used.

There are various advantages of the present invention, such as phosphoric acid,
One point is that grout can be provided at a lower cost than conventional methods because carbon dioxide gas, which is cheaper than conventional hardening agents such as sodium aluminate, is used as a hardening agent.

Further, according to the present invention, it is extremely easy to adjust the gel time of the grout. For example, when changing the gel time of the grout for some reason during continuous operation, the flow rate of carbon dioxide gas can be controlled by valve operation. You can easily change the grout to the desired gel time by adjusting the amount as appropriate.

Furthermore, in conventional grouting, the base agent and curing agent are often mixed into an aqueous solution in separate tanks, requiring two or more mixing tanks and a pump to inject the grout into the soil. There is only one mixing tank and no grout injection pump is required.

In addition, various advantages can be expected according to the present invention.

Next, the present invention will be explained from Example Q.

Example: Inner diameter 1 equipped with a stirrer (a star-shaped stirrer equipped with stainless steel blades with a width of 20 rnrrt and a length of 60 mm)
In a cylindrical stainless steel autoclave with a diameter of 0.00 mm and a length of 170 mm, JISB No. 250 ml of sodium silicate and 750 ml of water.
I prepared m1.

Next, while stirring the liquid phase, carbon dioxide gas was supplied from a liquefied carbon dioxide gas cylinder to the gas phase portion of the autoclave at room temperature.

Note that the internal pressure of the autoclave is increased to the fourth level by the supplied carbon dioxide gas.
The pressure was maintained as shown in the table below, and carbon dioxide gas was supplied for 2 minutes.

Next, the obtained grout was discharged from the bottom of the tank using the pressure inside the autoclave, poured into Toyoura standard sand, gelled, and then its unconfined compressive strength was measured.

The experimental conditions and the results obtained are shown in Table 2.

Reference Example The autoclave used in the example was equipped with a carbon dioxide gas blowing pipe and a cutout hole was provided in the upper part to form an open tank.

Next, this tank was charged with the same sodium silicate and water as in the example, and while stirring the liquid phase, carbon dioxide gas was blown into the aqueous sodium silicate solution at room temperature and pressure.

Table 3 shows the results when grouts were prepared in which the amount of carbon dioxide gas blown was varied and the time required for the liquid to gel (gel time) after the end of the blown carbon dioxide gas was several minutes.

As shown in Table 5, when carbon dioxide gas is blown into a sodium silicate aqueous solution under normal pressure, the desired grout can be obtained in a short time by increasing the amount of carbon dioxide gas blown into the solution. Most of the carbon dioxide gas is lost.

(Table 3, example of Storm 1) On the other hand, if the grout is gradually blown in so as not to cause loss of carbon dioxide, it will take a long time to prepare the grout.

(Example of Table 3, Flat 2) Moreover, in this case, the carbon dioxide gas blowing time becomes longer and the viscosity of the liquid becomes higher. It becomes unstable and becomes a gel.

Therefore, if you use this method to prepare a grout that gels in a short time after the carbon dioxide gas is blown for a long time, there is a risk that the grout will gel during the carbon dioxide gas injection, making it impractical. Not.

[Brief explanation of the drawing]

The drawing is a flow sheet illustrating one embodiment of the invention. 1... Sodium silicate aqueous solution (water glass) storage tank, 1
'・・・Pump for sodium silicate aqueous solution, 2...
...Water storage tank, 2'...Water pump, 3...
...Grout mixing tank, 3'...Agitator, 4...
... Carbon dioxide storage tank, 4' ... Flow rate (pressure) control valve, 5 ... Grout flow control valve.

Claims (1)

[Claims] 1. A sodium silicate aqueous solution and carbon dioxide gas are supplied into a tank with a sealed pressure-resistant structure equipped with a stirrer, and the inside of the tank is kept under pressure by the supplied carbon dioxide gas, and the liquid phase is stirred to dissolve the liquid phase in the sodium silicate aqueous solution. Carbon dioxide is characterized in that grout is prepared by dissolving carbon dioxide gas in water, and then the resulting grout is discharged outside the tank by increased pressure inside the tank and injected into the soil, where it gels in the soil. Soil stabilization method using silicic acid cloud using gas as a hardening agent.