JPS58174489A - Stabilization method of soil - Google Patents

Abstract

PURPOSE:To cause stable gelation of soil, by injecting water glass and a gelling agent containing an alkali bicarbonate, a magnesium salt and citrate in a specific proportion into the soil for stopping water from the ground where water is welling out, etc. CONSTITUTION:(A) A solution of sodium silicate with 10-40wt% solid content and (B) a gelling agent prepared by dissolving (i) 100pts.wt. sodium bicarbonate and/or potassium bicarbonate, (ii) 5-100pts.wt. sulfate and/or chloride of magnesium and (iii) 3-200pts.wt. citrate and/or potassium salt in water to give 60- 350g/l concentration are usually prepared separately, and the resultant solutions (A) and (B) are injected into a soil through a double-pipe, etc. by a pump. EFFECT:The stable gelation can be carried out through all seasons, and the shrinkability of the gelled material and the deterioration of strength in water can be retarded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing soil quality using an improved water glass grout.

Conventionally, chemical injection methods have been known in which various chemical solutions are injected into the ground and gelled in the ground in order to strengthen soft ground or stop water from spring water. Water glass grout, which has a gelling agent added to it as a main ingredient, has been widely put into practical use. In the chemical injection method, there has recently been a demand for instant setting type grout with a gel time of several seconds to several seconds.This means that conventional grouts with a gel time of several minutes to several tens of minutes are difficult to install in places with a lot of underground water flow or in strata with a lot of sand and gravel. This is because when used, the chemical solution may be diluted and flowed out before gelatinization, or the chemical solution may penetrate into unnecessary areas, resulting in incomplete ground improvement and adverse effects on pollution. However, instant setting type grout has an unstable gel time and tends to partially gel, resulting in an uneven gel that often causes cloudiness and gel-liquid separation. Therefore, it becomes difficult to adjust the gel time, which causes a decrease in the strength of the injection ground. This tendency is particularly strong in the summer as the water temperature rises. In short, it is necessary not only to have a short gel time, but also to be able to form a uniform gel with a stable gel time throughout the year in order to improve the quality.

When only alkali bicarbonate is used as a gelling agent for soil stabilization, the infiltrated gelatinized material shrinks to less than 80% of its original volume overnight after gelation, and to less than 50% a few days later. Since the volume of the soil layer does not change, the soil layer becomes porous, reducing its water-stopping properties, and the gel component dissolves in the water that permeates, causing it to become brittle, and its underwater strength rapidly decreases.

The present invention uses water glass and its gelling agent to stabilize soil quality, uses alkali bicarbonate as the main agent, and uses this together with magnesium salt and citrate to achieve stable gelation. The object of the present invention is to provide a method for improving the above-mentioned decrease in shrinkage and strength in water.

That is, the present invention uses a sodium silicate solution having a solid content of 10 to 40% by weight, 100 parts by weight of sodium bicarbonate and/or potassium bicarbonate as a gelling agent, and magnesium sulfate or chloride alone or as a mixture (anhydrous chloride). Specialty) 5-100
60 to 350 parts by weight, consisting of 3 to 200 parts by weight of soda salt of citric acid, kali rum salt alone or in a mixture
This is a soil stabilization method characterized by injecting a chemical solution containing 1 g/l into the soil and hardening it. In an attempt to improve shrinkage when alkali bicarbonate is used as a gelling agent, a two-component system using a magnesium salt in combination is known (Japanese Patent Publication No. 53'-43247, Japanese Patent Publication No. 56-21).
No. 778). However, magnesium salt alone tends to cause uneven gelation and is not suitable for use at high liquid temperatures in summer. Therefore, when magnesium salt is incorporated in a large enough amount to be effective in improving shrinkage, cooling is required or use is limited to special regions such as cold regions. On the other hand, there is a known method that uses oxyacids such as citric acid, tartaric acid, and lactic acid together with aluminum salts and magnesium salts, without using alkali bicarbonate, to utilize the chelating effect of binding with other metal ions ( Special Publication No. 53-24724). However, it is difficult to adjust the gel time of this type of gelling agent, and it is difficult to obtain a stable instant-setting type drug. Phosphate-based chelating agents are known, but when used as instant-setting type gelling stabilizers, the chemical solution may become cloudy before being mixed with water glass, making it difficult to put it into practical use. Much consideration is required.

In the present invention, alkali citrate is used as a stabilizer for gelation, but citric acid itself cannot be used because it foams when dissolved, and other alkali salts of oxycarboxylic acids, such as sodium tartrate or sodium gluconate, are not uniformly used. It is unsuitable because it produces a gel. The compounding ratio of the chemical solution used is within the range of DEFG shown in Figure 1; within the range of The strength of the gel is also low. Further, within the range of Z, the gel shrinks significantly and its strength in water becomes low, and within the range of W, a non-uniform gel is likely to be formed. Particularly preferable from the economic point of view is H in Figure 1.
Magnesium chloride and/or fi7AF per 100 parts by weight of alkali bicarbonate within the range of IJK
IJ salt 10-40 parts, alkali citrate 5-12
It is a 0 heavy bomb.

The soil stabilization work is the same as before; before construction, a sodium silicate aqueous solution and the above-mentioned chemical solution are prepared separately, and both solutions are injected into the soil with a pump using a double pipe, etc. - Also, the component concentration of this drug solution is 60 to 350 in drug solution 11.
g is particularly preferably 80 to 250 g; if it is less than 60 g, it will be difficult to precipitate a strong silicic acid gel, and if it exceeds 350 g, the solubility will deteriorate and it is also unsuitable from an economical point of view. Sodium silicate concentration is Ha20 and SL O2 solid content is 10-40% by weight
is preferable, and if it is less than 10% by weight, the consolidation strength is sufficient and 40
If it exceeds % by weight, the viscosity will increase and there will be problems in terms of permeability into the ground. Also, the 5LO2/Na2O molar ratio is 1
．． It can be used as long as it is within the range of 5 to 4.0, but especially JIS3
No. water glass is preferred because it is easily available.

As described above, according to the method of the present invention, an instant setting type grout using alkali bicarbonate as a gelling agent for water glass is produced, and its shrinkage is improved with a specific range of magnesium sulfate and chloride. By using alkali citrate in combination, the stability during gelation can be significantly improved throughout the seasons, and the strength in water is also improved, so it has great industrial value.

The effects of the present invention will be illustrated below with reference to Examples and Comparative Examples.

In the examples, all drug amounts are calculated on an anhydride basis.

Examples, comparative examples JIsa No. Sodium Silicate (Ha209.5%.

Add 50 parts of water to 5L0229%) 50■C to prepare solution A.

In addition, the chemicals listed in the table below were dissolved in water to make 100C and this was used as Solution B. Table 1 shows the results of mixing equal volumes of liquids A and B and measuring the gelation temperature, gelation status, and gel time. In addition, a mixture of equal volumes of liquids A and B was prepared at 15°C.
The volume and unconfined compressive strength of the small mogels after being left overnight are shown in Table 2. '1': Table 1 Note: In Table 1, KHCO3 and/or Ha
The composition of other chemicals with respect to 100 parts by weight of HCO3 is as follows.

Table 2 *The volume immediately after gelation is taken as 100%, and the volume shrunk after overnight is shown.

Next AI 100m#: vs./KHCO36g, 1
Solution B and K were prepared by dissolving 2g of IaHQ)s, 42g of rbsO, and 2g of sodium citrate in water to make 100■C.
HQ] 3 6g.

Dissolve 32g of HaHC in water and 100mL of NLT! :Liquid B-solution was prepared, and both AB solutions or AB-solutions were mixed and infiltrated into compacted Toyoura standard sand soog to prepare a sand gel. This was cured in water and in the air (without drying), and the change in -axial compressive strength over time was measured at a constant temperature of 20°C. The results are shown in Figure 2 (
Compression speed is 1%/min). In FIG. 2, when the sand gel using AB-both liquids was cured in water, the end face could not be formed after 7 days, making it impossible to measure the strength.

From FIG. 2, it can be seen that the comparative example using both AB'' liquids has a higher initial strength and the decrease in underwater strength is significantly smaller than the Example using both AB liquids.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the composition of the gelling agent used in the present invention, and FIG. 2 is a diagram showing changes in underwater curing strength and air curing strength in Examples and Comparative Examples of the present invention. The symbols for the middle platform measurement points in Figure 2 are as follows. ○: Atmospheric curing of sand gel using both A and B liquids:
Same water curing Δ: AB-atmospheric curing of sand gel using both liquids: Same
Underwater! 1 Applicant Osaka Soda Co., Ltd. Agent Patent Attorney Toru Monda

Claims (1)

[Claims] Sodium silicate solution with a solid content of 10 to 40% by weight and sodium bicarbonate and/or bicarbonate strength as a gelling agent 10
5 to 10051 parts by weight of magnesium sulfate or chloride or a mixture (calculated as anhydride) per 0 parts by weight, 3 to 2 parts of sodium citric acid or potassium salt alone or as a mixture
A method for stabilizing soil quality, which comprises injecting a chemical solution containing 60 to 350 g/l of a component consisting of 0.00 parts by weight into soil and hardening it.