JPS5844103B2 - Soil stabilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing soil quality using a water glass grout using carbon dioxide as a gelling 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. So-called water glass grout, which is a main ingredient in which this is combined with a gelling agent, has been widely put into practical use.

Many substances have been proposed as gelling agents for water glass grout, such as acids, acid salts, water-soluble polyvalent metal salts, organic esters, and aldehydes. When gelling glass, many methods have drawbacks, such as producing non-uniform gels, being dangerous, and being expensive.

The present invention attempts to stabilize the soil quality with various advantages by using carbon dioxide gas as a gelling agent when stabilizing the soil quality with a water glass grout.

The technique of gelling water glass with carbon dioxide gas is known in the field of producing mold sand for metal casting.

This technology mixes water glass with molding sand, molds it, then blows carbon dioxide gas into it, and the next reaction causes Na2SiO3+XH2
O+CO2→Na2CO3+SiO2.xl (20 Silicic acid is liberated, and sand particles are bonded to it with soda carbonate to harden it. This is a method that is widely used as a simple method for producing mold sand.

The present inventors believe that carbon dioxide gas is harmless and cheaper than the conventional gelling agent for water glass grout, and that carbon dioxide gas is simply sprayed onto a molded body of water glass and sand in order to use the above technology. I learned that carbon dioxide gas is suitable as a gelling agent for water glass grout because it produces molding sand strong enough to withstand the weight of molten metal and is highly effective as a gelling agent. Various studies have been conducted regarding its practical application, but since carbon dioxide gas is a gas and has low solubility in water, when using it as a gelling agent for water glass grout, it is difficult to combine the main agent and gelling agent as in the conventional method. It has been found that the method of preparing grout by mixing under normal pressure is inappropriate.

In other words, conventionally, as a construction method for water glass grout,
This is called a two-component systematic chemical injection method, in which the base agent and gelling agent are mixed into aqueous solutions with appropriate concentrations suitable for the construction in separate mixing tanks (normal pressure open tanks) before construction, and both are mixed at the time of construction. The most common method is to mix using a Y-tube and inject into the soil with a pump, but when carbon dioxide is used as a gelling agent, the solubility of carbon dioxide in water is small and l'(0
, 145gCO2/100gH2O, normal pressure, 25℃),
This method cannot be applied because it is not possible to prepare an aqueous gelling agent solution with a practical concentration.

Another method is to make the base agent and gelling agent into an aqueous solution in the same tank (normal pressure open tank) and then immediately inject it into the soil.

There is a method called the so-called one-liquid chemical injection method, and according to this method, a practical grout can be obtained even when carbon dioxide gas is used as a gelling agent.
When carbon dioxide gas is blown into water glass at room temperature and pressure, the dissolution of carbon dioxide gas into water glass is poor, and the gel time most often used in actual construction is difficult to prepare grout. takes quite a long time.

For example, JISa No. Sodium silicate: Water = 1:3 (volume)
When carbon dioxide gas is blown into a normal water glass for soil stabilization at a ratio of It takes more than 60 minutes.

For this reason, the inventors of the present invention conducted various studies in order to find a method to obtain grout with a short gel time in a short period of time. If water glass is supplied to the liquid supply position at the same time as carbon dioxide gas at a certain pressure, and the water glass is atomized by the carbon dioxide gas ejected at high speed from the nozzle outlet, the carbon dioxide gas will be quickly absorbed into the water glass. It was discovered that a grout with a short gel time can be obtained almost instantaneously, and the present invention was developed.

That is, the present invention stabilizes soil quality with a grout that uses water glass as a main ingredient and carbon dioxide as a gelling agent.
Water glass and carbon dioxide gas are each supplied to a two-fluid nozzle to atomize the p water glass with high-speed carbon dioxide gas, thereby causing the carbon dioxide gas to be quickly absorbed into the water glass, and then the fine particles that have absorbed carbon dioxide gas are The grouting liquid is collected in a receiving tank to form a liquid, and the grouting liquid thus obtained is injected into the soil.
This is a soil stabilization method characterized by gelation in the soil.

FIG. 1 is a flow sheet showing an embodiment of the present invention.

The present invention will be explained below with reference to FIG.

Carbon dioxide at a higher pressure is supplied from a carbon dioxide storage tank 1 (usually a liquefied carbon dioxide cylinder) to a gas supply position of a two-fluid nozzle 2, and is ejected from the nozzle outlet at high speed.

As is well known, a two-fluid nozzle is a so-called atomizing nozzle in which liquid flows out from a pore to obtain minute droplets, and the liquid is atomized by flowing high-speed gas around it (Chemical Industry Dictionary, Chemical Edited by Engineering Society, published by Maruzen Co., Ltd., No. 3
(See page 27) Usually, it has a structure as shown in FIGS. 2, 3, and 4.

The one shown in FIG. 2 is usually called an orifice type, and the ones shown in FIGS. 3 and 4 are usually called a venturi type. Each is commercially available and easy to obtain, but it is also possible to make one yourself.

At the same time that carbon dioxide gas is supplied to the two-fluid nozzle 2, water glass adjusted to a concentration suitable for soil treatment is supplied to the liquid supply position of the nozzle.

The water glass supplied to the two-fluid nozzle 2 is atomized by the pressure of the carbon dioxide gas flowing at high speed inside the nozzle, and is ejected from the nozzle outlet together with the carbon dioxide gas.

Therefore, the gas-liquid contact between the carbon dioxide gas and the water glass becomes very good, and the carbon dioxide gas is quickly absorbed into the water glass.

The water glass supplied to the two-fluid nozzle 2 is supplied from the raw water glass storage tank 3 and the water storage tank 4 by pumps 3' and 4' dedicated to each of the raw water glass and water at predetermined ratios.
is supplied to the line mixer (pipe mixer) 5 by
It is mixed into a uniform liquid in a mixer.

As the raw water glass, water glass conventionally used for soil stabilization is used, but usually JI No. 83 sodium silicate is most often used.

The size of the water glass droplets ejected from the outlet of the two-fluid nozzle 2 is related to the flow rate of carbon dioxide gas flowing through the nozzle and the amount of water glass supplied to the nozzle. The smaller the amount of water glass supplied, the finer the particles are obtained.

In order to make normal water glass for soil stabilization into light and heavy droplets, the flow rate of carbon dioxide gas flowing through the slot part (pore part) of the two-fluid nozzle 2 should be 50 rr for 1.7 seconds or more. It is necessary to adjust the supply amount and to make sure that the ratio of carbon dioxide gas and water glass supplied to the two-fluid nozzle 2 is usually less than or equal to water glass/carbon dioxide (volume ratio) -0.1.

It is difficult to adjust the amount of carbon dioxide gas and the amount of water glass supplied to the two-fluid nozzle 2 so as to obtain droplets having a particle size of about 10 to about 100 microns.

The water glass droplets ejected from the outlet of the two-fluid nozzle 2 are collected in a receiving tank 6, which has an opening 7 for exhausting carbon dioxide gas at the top, to form a uniform grout solution, and are then turned into gravel by a pump 8. It is injected and gelled in the soil to stabilize the soil quality.

The gel time of grout is usually adjusted using two-fluid nozzle 2.
This is done by keeping the amount of water glass supplied (supply rate) constant and varying the supply rate of carbon dioxide gas.

As the carbon dioxide gas supply rate increases, a grout with a shorter gel time can be obtained.

By appropriately selecting and combining production conditions such as the supply rate of water glass and the supply rate of carbon dioxide gas, it is possible to produce grout with an arbitrary long or short gel time almost instantaneously.

The inventor of the present invention is of course capable of carrying out not only a batch method but also a continuous method.

That is, water glass and carbon dioxide gas are each continuously supplied to the two-fluid nozzle 2, and the grout mixed to achieve the desired gel time is continuously discharged from the receiving tank 6 by the pump 8 and into the soil. inject.

According to this continuous method, a large amount of grout used in large-scale construction can be produced and injected into gravel using a simple device consisting of a small two-fluid nozzle and a small-capacity receiving tank.

The present invention has various advantages, including the use of carbon dioxide, which is cheaper than conventional gelling agents such as phosphoric acid and aluminic acid, which makes it possible to produce grout more economically than before. can.

Further, according to the present invention, it is extremely easy to adjust the gel time of grout. For example, when changing the gel time of grout during continuous injection, the desired value can be easily achieved by simply adjusting the flow rate of carbon dioxide gas as appropriate by operating a valve. It can be made into gel time grout.

Furthermore, in conventional injection, the base agent and gelling agent are often mixed into aqueous solutions in separate tanks, which usually requires at least two mixing tanks with agitators and a pump for each liquid delivery. The invention does not require such a mixing tank, and only requires one receiving tank and one grout injection pump.

In addition, various other benefits can be expected according to the present invention, such as the ability to greatly reduce the labor involved in grout production.

As already explained, in the present invention, water glass droplets that have absorbed carbon dioxide ejected from a two-fluid nozzle are collected in a receiving tank to form a uniform liquid, and then this liquid is pumped with an appropriate pump. Although this is a method of injecting the liquid into the soil, it is also possible to use the ejection pressure to inject the droplets ejected from the two-fluid nozzle into the soil without collecting them in a receiving tank.

Examples of this method include, for example, attaching the outlet of a two-fluid nozzle directly to the upper end of a grout injection pipe (single pipe) buried in the soil, and injecting droplets ejected from the nozzle into the soil of the casing 1; The inlet of a two-fluid nozzle is attached to one end of the double pipe, the outlet of the nozzle is buried in the soil, water glass and carbon dioxide are supplied from the other end of the double pipe, and droplets are ejected from the nozzle outlet. Examples include a method of diffusing it into the soil.

Next, the present invention will be explained in more detail using Example 1c, but the present invention is not limited to the following example.

Example A fluid nozzle having the structure shown in FIG. 4 was used.

(However, A=17.3wItφ, B=4[φ.0=5[
φ, D=20wIl, E (slot)=3 φ, F=2
1.7 [φ] Carbon dioxide gas is continuously supplied from a carbon dioxide gas cylinder to the gas supply position of the two-fluid nozzle, and at the same time, it is jetted out at high speed from the outlet of the nozzle, and at the same time, JI83 Sodium silicate: Water = 14 :86 (weight ratio) of water glass was supplied and sprayed continuously.

Next, the spray is collected in a cylindrical receiver tank with an opening at the top, and the resulting grout liquid is injected into Toyoura standard sand using a pump to gel. After gelation, the unconfined compressive strength of the resulting sand gel is calculated. It was measured.

The experimental conditions and results obtained are shown in Table 1.

As is clear from Table 1, by keeping the amount of water glass supplied to the binary nozzle constant and varying the amount of carbon dioxide gas supplied, it is possible to produce grout with an arbitrary long or short gel time. .

Example 2 The structure shown in Fig. 4 was used as a binary nozzle (
However, A=17.3Wφ, B=4Wφ, C=511Il
lφ, D=2 o, m, E, (slot part) knee 4.5Mφ, F=21.7mφ) Using the above binary nozzle, Example 1. A grout solution was produced in the same manner as in the above.

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

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention. 1... Carbon dioxide gas storage tank, 2... Two-fluid nozzle, 3... Raw water glass storage tank, 3'...
... Pump for raw water glass, 4 ... Water storage tank, 4
'...Water pump, 5...Line mixer 6...Receiving tank, 7...Opening hole for carbon dioxide gas exhaust, 8... Pump for grouting. 2, 3 and 4 are cross-sectional views of the two-fluid nozzle used in the present invention.

Claims (1)

[Claims] 1. In order to stabilize the soil quality with grout that uses water glass as the main ingredient and carbon dioxide gas as the gelling agent, water glass and carbon dioxide gas are each supplied to a two-fluid nozzle, and the water glass is atomized by high-speed carbon dioxide gas. As a result, carbon dioxide gas is quickly absorbed into the water glass, and then the fine particles that have absorbed carbon dioxide gas are collected in a receiving tank to form a liquid. A soil stabilization method characterized by gelation.