JPS5856393B2 - Soil stabilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing soil quality with an improved silicate-based soil stabilizer.

Conventionally, grouting methods have been known in which various chemical solutions are injected into the soil and hardened in the soil in order to strengthen soft ground or stop leaking ground. So-called silicate-based grouts, which are made in combination with grouting agents, have the advantage of being inexpensive and less likely to cause pollution than other grouts, and are currently in widespread practical use.

Various substances have been proposed as hardening agents for silicate grout, but bicarbonates such as sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate are generally used because they are non-hazardous and easy to handle. There is.

However, conventional silicate grouts using bicarbonate as a hardening agent have the following drawbacks.

In other words, when curing a sodium silicate aqueous solution, the strength of the cured product generally increases as the sodium silicate concentration increases, but in conventional silicate grout using bicarbonate as a hardening agent, even if the sodium silicate concentration increases, the strength of the cured product increases. It is not possible to increase the strength of the cured product.

In addition, for silicate grouts, the curing time is usually adjusted by varying the amount of hardening agent used, but in conventional silicate grouts that use bicarbonate as a hardening agent, the amount of hardening agent used is Even if constant, the curing time will vary widely if the sodium silicate concentration changes slightly, making it difficult to adjust the curing time.

Furthermore, in this grout, the cured product exhibits a remarkable phenomenon of retardation (a phenomenon in which water separates and shrinks when the gel body is left unattended), and therefore cracks occur when the cured product is left unattended.

For these reasons, when the soil quality is stabilized with conventional chlorine silicate grout using bicarbonate as a hardening agent, (1) the soil strength after stabilization treatment cannot be sufficiently increased; The water-stopping properties of the soil cannot be said to be good either.

(2) Difficult to adjust grout curing time L.

There are problems such as:

The present inventors conducted various researches in an attempt to overcome the above-mentioned drawbacks that occur when soil quality is stabilized with conventional silicate-based grout using bicarbonate as a hardening agent. The molar ratio of Na2O/5i02, which is not used in salt grout, is 1/3.8.
The present invention was accomplished by finding that the objective could be achieved by using sodium silicate of No. 42.

That is, in the present invention, a chemical solution containing sodium silicate as a main ingredient containing 3.8 to 4.2 moles of Si02 per mole of Na and bicarbonate as a hardening agent is injected into soil. This is a soil stabilization method characterized by hardening.

Unlike conventional silicate-based grout (hereinafter referred to as conventional grout) that uses bicarbonate as a hardening agent, the grout used in the present invention has little variation in hardening time even when the sodium silicate concentration changes. Easy to adjust curing time.

Furthermore, when the concentration of sodium silicate in the grout used in the present invention is increased, the strength of the cured product increases.

Therefore, according to the present invention, the strength of treated soil can be made much higher than when the soil quality is conventionally stabilized by grouting.

Here, in order to clarify the above-mentioned advantages of the grout used in the present invention, the differences in effects between the grout and conventional grout will be explained using figures.

Figure 1 shows JI8 No. 3 sodium silicate (Na20/Si02 molar ratio = 1/3.4), which is commonly used in conventional silicate grouts, diluted with water to produce 400 l of chemical solutions with various sodium silicate concentrations. The relationship between the concentration of 5i02 in the chemical solution and the curing time is plotted when 13.5 kg of sodium bicarbonate is added to each of the chemical solutions and cured at a temperature of 15 to 16°C. The amount of S i02 present in the chemical solution 4001, and the vertical axis represents the hardening time of the chemical solution.

As shown in Fig. 1, in conventional grout, if 50 kg of Si02 is present in 400 J of chemical solution, the curing time is 5 minutes, whereas the amount of hardening agent used remains the same and the hardening time is 5 minutes. Increase by 5 kg and add 5 to the drug solution.
As is clear from the fact that when 5 kg of grout is present, the curing time is extended to 16 minutes, even if the amount of curing agent used is constant, the curing time of the grout will vary greatly even if the SiO2 concentration changes slightly. .

And if the curing time fluctuates greatly like this, when grout is mixed several times during actual construction, each time,
It is difficult to formulate grouts with the same cure time.

In contrast, Fig. 2 shows the Na2O/S used in the present invention.
Similarly to the above case, sodium silicate with an iO2 molar ratio of 1/4.0 was diluted with water to prepare 400 J of chemical solutions with various SiO2 concentrations, and 9.5 J of sodium bicarbonate was added to each of them.
This is a plot of the relationship between the 5i02 concentration in the chemical solution and the curing time when 5i02 kg is added and cured at a temperature of 15 to 16°C. The definitions of the horizontal and vertical axes in the figure are the same as in Figure 1. be.

As shown in Fig. 2, in the grout used in the present invention, the curing time is 3 minutes and 30 seconds when 50 kg of 5i02 min is present in the chemical solution 4001, whereas the curing time is 3 minutes and 30 seconds when the amount of curing agent used remains unchanged. The curing time when increasing the weight to 55 kg is between 3 minutes and 30 seconds and 4 minutes, which shows that the curing time for changes in the 5i02 concentration in the chemical solution is longer than that in the case of Fig. 1 (conventional grout). The fluctuation is much smaller.

Therefore, even when the grout used in the present invention is prepared in several batches, it is easy to obtain a grout with almost the same curing time each time.

Figure 3 shows the relationship between the strength of the cured grout and the SiO2 concentration in the grout as explained in Figure 1. The vertical axis of the figure shows the uniaxial compressive strength of the cured product, and the horizontal axis The definition of is the same as in the case of Figures 1 and 2.

As is clear from Figure 3, in conventional grout, Si
Even if the O2 concentration is increased, the strength of the cured product does not improve, but rather decreases.

On the other hand, Fig. 4 shows the relationship between the strength of the cured grout and the 5i02 concentration in the grout as explained in Fig. 2, and the definition of the vertical and horizontal axes in the figure is as shown in Fig. 3. Same as in case.

As is clear from Figure 4, when the Si02 concentration of the grout used in the present invention is increased, the strength of the cured product not only improves, but also the strength of the cured product rises to a much higher level compared to conventional grout. be.

Therefore, according to the present invention, treated soil can be made much stronger than when the soil quality is conventionally stabilized by grouting.

In the present invention, it is necessary to use sodium silicate containing 3.8 to 4.2 moles of 5i02 per 201 mole of Na as the sodium silicate source.

When sodium silicate with a SiO20 ratio of 3.8 mol or less per 1 mol of Na2O is used, the effect is insufficient and is not preferred.

The effect becomes better when using sodium silicate with a higher ratio of 5i02 (more than 3.8 mol per 201 mol of Na).
It is usually difficult to produce sodium silicate containing 42 mol or more of SiO2 per 201 mol of Na.

In the present invention, 5 to 6% Na2O by weight, 5i
An aqueous sodium silicate solution containing 19 to 25% of 02 is preferably used.

Sodium silicate is diluted with water before construction to make an aqueous solution with an appropriate concentration suitable for the purpose of construction, but the concentration of the active ingredient (3 parts Na2SiO) in the chemical solution injected into the soil is usually 15 to 30% by weight.

Types of bicarbonate used in the present invention include sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate.

Of course, it is possible to use sodium bicarbonate alone, but since sodium bicarbonate has a lower solubility in water than other bicarbonates, it is desirable to use it in combination with other bicarbonates when a large amount is used.

The amount of bicarbonate used varies depending on the desired curing time.

For example, Na2O, which is commonly used in the present invention, is
When a chemical solution prepared by diluting a sodium silicate aqueous solution containing 6% by weight and 19 to 25% by weight of SiO2 with an equal volume (volume) of water is cured in soil at room temperature in 1 to 10 minutes, the chemical solution is usually 1 to 2% of bicarbonate is used.

Conventionally, appropriate amounts of sodium sulfate, soda carbonate, potassium carbonate, potassium sulfate, potassium chloride, sodium chloride**, sodium thiosulfate, potassium iodide, sodium iodide, sodium tripolyphosphate, or magnesium sulfate are added to silicate grout. It is known that this makes it easier to adjust the curing time.

Therefore, such chemicals can be added to the grout used in the present invention as appropriate.

The construction method for soil stabilization is the same as before, and before construction, a chemical solution containing sodium silicate dissolved in water (solution A) and a chemical solution containing other ingredients dissolved in water (solution B) are mixed separately. There,
Both are mixed and injected into the soil using a pump.

Next, the present invention will be explained using comparative examples and examples.
In each example, all parts simply refer to weight.

Comparative Example JIS No. 3 sodium silicate (Na20/5i02 molar ratio = 1/3.4) is diluted with water to prepare four types of 200 cc of sodium silicate aqueous solutions (liquid A) each having a different SiO2 concentration.

(See Table 1) On the other hand, prepare four containers of a chemical solution (solution B) in which 13.5 S' of bicarbonate of soda was dissolved in water to make a total volume of 200 CC.

Liquid A and liquid B were mixed and cured at a temperature of 15°C.

Table 1 shows the results of measuring the curing time of the mixture, the unconfined compressive strength of the cured product, and the amount of water released from the cured product during 7 days of standing after curing.

As is clear from Table 1, even if the amount of curing agent used in conventional grouts is constant, the curing time varies widely when the 5i02 concentration changes.

Furthermore, even if the SiO2 concentration was increased in this grout, the strength of the cured product did not improve, and the amount of syneresis water was large.

Example I Aqueous solution of sodium silicate (Na 205.8% by weight, 5j0222) with a molar ratio of Na 2 / Si 02 of 1/40
．． 5% by weight, the remainder is water) and diluted with water to prepare 200CC of sodium silicate aqueous solutions (liquid A) with different 5/02 concentrations.
Mix 6 types of each.

(See Table 2) On the other hand, prepare 6 bottles of a chemical solution (solution B) made by dissolving 9.51 parts of bicarbonate of soda in water to make the total volume** 200CC.

Liquid A and liquid B were mixed and cured at a temperature of 15°C.

Table 2 shows the results of measuring the curing time of the mixture, the unconfined compressive strength of the cured product, and the amount of water released from the cured product during a period of 7 days after curing.

As is clear from the comparison between Table 2 and Table 1, the grout used in the present invention shows much less variation in curing time with respect to changes in SiO2 concentration than the conventional grout shown in the comparative example.

Furthermore, as the 5/02 concentration in the grout increases, the strength of the cured product increases, and the amount of syneresis water from the cured product is significantly smaller than in the comparative example.

Example 2 Using the same sodium silicate as used in Example 1, three 200 cc aqueous silicate solutions (Liquid A) each having a different 5/02 concentration are prepared in the same manner.

(See Table 3) On the other hand, prepare three chemical solutions (liquid B) in which potassium bicarbonate 82 and sodium sulfate 72 are dissolved in water to make a total volume of 200 cc.

Thereafter, both liquids A and B were mixed and cured in the same manner as in Example 1.

Table 3 shows the results of measuring the curing time of the mixture, the unconfined compressive strength of the cured product, and the syneresis water from the cured product.

Regarding the obtained results, the same can be said as in Example 1.

Example 3 Prepare the same sodium silicate aqueous solution as used in Example 2 (3 types) On the other hand, a chemical solution (liquid B) ※※ prepared by dissolving 82 g of sodium bicarbonate and 5 g of potassium carbonate in water to make a total volume of 200 cc. Prepare 3 pieces.

Thereafter, both liquids A and B were mixed and cured in the same manner as in Example 2.

Table 4 shows the results of measuring the curing time of the mixture, the unconfined compressive strength of the cured product, and the syneresis water from the cured product.

Regarding the obtained results, the same can be said as in Example 1.

[Brief explanation of drawings]

Figure 1 shows the relationship between the amount of Si02 contained in a conventional silicate grout using bicarbonate as a hardening agent and the hardening time of the grout. FIG. 2 is a diagram showing the relationship between the amount of 5iO2 contained in the grout and the hardening time of the grout. In both figures, the horizontal axis shows the amount of 5iO20 (kg) contained in the grout, and the vertical axis shows the hardening time (minutes) of the grout. Figure 3 shows the relationship between the unconfined compressive strength of the cured grout shown in Figure 1 and the amount of SiO2 contained in the grout, and Figure 4 shows the relationship between the cured grout shown in Figure 2. This is a diagram showing the relationship between unconfined compressive strength and the amount of SiO2 contained in grout. The definition of the horizontal axis in Figures 3 and 4 is the same as in Figures 1 and 2, and the vertical axis is The uniaxial compressive strength (kg/c4) of the cured product is shown.

Claims (1)

[Claims] 1 The main ingredient is sodium silicate containing 5i02 at a ratio of 3.8 to 4.2 moles per 201 moles of Na, and a chemical solution containing bicarbonate as a hardening agent is injected into the soil and hardened in the soil. A method for stabilizing soil quality.