JPH0643582B2 - Ground injection chemical - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a chemical solution for soil injection using an acidic silicic acid aqueous solution used for consolidation of soft or leaking soil or stopping of water, and particularly, the gelation time is adjusted. The present invention relates to a ground injection drug solution which is easy, has a neutral solidified substance, and exhibits high strength.

[Conventional technology]

The acidic silicic acid aqueous solution is obtained by mixing water glass and an acid to remove the alkali in the water glass, and is usually prepared by jetting or forcibly stirring and mixing the acidic liquid and the water glass aqueous solution, and pH 1 to It is a strongly acidic silicic acid aqueous solution of 3.

When this acidic silicic acid aqueous solution is used as a ground injection chemical, it has a long gelation time, and therefore, an alkaline promoter is usually added to and mixed with this aqueous solution to promote gelation. As the alkalinity accelerator, water glass liquid, caustic alkali, carbonate, bicarbonate and the like have been conventionally used.

Also known is a method of using a sparingly soluble alkaline agent such as calcium carbonate, magnesium carbonate, calcium hydroxide or magnesium hydroxide in order to make the gelation time gentle.

[Problems to be solved by the invention]

However, in the former method, the gelling time is greatly changed with respect to such a slight quantitative change of the conventional alkaline promoter, so that it is very difficult to adjust the gelling time.

Further, the latter method has a drawback that the gelling time is greatly shortened when the amount of the hardly soluble alkaline agent added is increased, and the gelled product exhibits alkalinity. When carbonate is used, carbon dioxide is generated and the solidified substance becomes porous,
There was a drawback that the strength became weak.

The object of the present invention is to improve the drawbacks existing in the above-mentioned known technology, and particularly to provide a ground injection chemical solution in which the long solidification time is easily adjusted and the solidified body exhibits high strength in the neutral region. To provide.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention is characterized in that a calcium salt or magnesium salt of phosphoric acid is mixed with an acidic silicic acid aqueous solution having a pH of 3 or less obtained by treating water glass with an acid. .

The aqueous solution of acidic silicic acid used in the present invention is obtained by mixing an aqueous solution of water glass and an acid to remove the alkali in the water glass, and usually exhibits a strong acidity of pH 1 to 3.

The phosphate used in the present invention must be a calcium salt or a magnesium salt of phosphoric acid such as primary, secondary, tertiary, etc. Other salts such as primary, secondary, tertiary The effect of the present invention cannot be obtained with an alkali metal phosphate such as sodium phosphate.

Sodium triphosphate and dibasic sodium phosphate are alkaline, and the gelation time curve of addition amount is gentler than that of other alkaline agents, but the gelation time is within tens of seconds when the addition amount is large. Will end up.

Further, monobasic sodium phosphate is acidic, and even if it is added to an acidic silicic acid aqueous solution, gelation promoting action does not occur so much.

On the other hand, the calcium or magnesium phosphate according to the present invention, particularly the dibasic calcium phosphate and the dibasic magnesium phosphate, are slightly water-soluble and exhibit a gelation promoting effect on the acidic silicic acid aqueous solution, although they are neutral to slightly acidic. In addition, the gelling time does not decrease more than tens of minutes or tens of minutes or less even when added in a large amount.

The reason for this is that calcium ions or magnesium ions have a gelation-promoting action, and the pH value of the aqueous solution is neutral to slightly acidic, so the slope of the gelation curve is extremely gentle, and the gelation time is a certain time. It is considered that the effect of not shortening is produced within the range, and furthermore, the pH value of the gelled product is kept from weakly acidic to neutral and cannot reach the alkaline region, which is an extremely unique effect. It was first discovered by the applicant.

〔Example〕

Hereinafter, the present invention will be described using dicalcium phosphate.

Experiment-1 An acidic silicic acid aqueous solution was prepared according to the formulation shown in Table-1.

Experiment-2 50 cc of each of the acidic silicic acid aqueous solutions (1) and (2) of Experiment-1 was prepared and used as solution A.

Furthermore, the amount of dicalcium phosphate was changed to make 50 cc suspensions with water, and this was designated as solution B.

The solutions A and B were combined, and the gelation time and pH of the combined solution were measured. The results are shown in the graphs of FIGS. 1 and 2.

In the figure, curve A shows the pH immediately after the confluence, and curve B shows the gelled 1
The pH of the solidified body after a lapse of days is shown.

From FIG. 1 and FIG. 2, it can be seen that a stable gelation time is obtained in the range of several tens of minutes to several minutes which is the most suitable gelling time for injection. Immediately after merging, the combined solution exhibits an acidic to weakly acidic pH value as shown by the curve A, but after gelation it has a pH of 5 to neutral as shown by the curve B, and the chemical solution of the present invention is a substantially harmless grout. I understand.

From this result, in the present invention, it is possible to adjust a very stable long gelation time, and even if there is an error in the injection operation or a compounding error due to the variation in the discharge amounts of the liquids A and B, the change in the gelation time can be suppressed. It turns out that a small amount of injection is possible.

Experiment-3 An example of an experiment using various additives is shown in Table 2 for comparison.

From the results of Table-2, dicalcium phosphate according to the present invention,
In the case of dibasic magnesium phosphate (formulation No. 15-20)
It can be seen that, compared with the other additives, the gelling time with respect to the addition amount has a very small variation and is stabilized.

Experiment-4 Table 3 shows the uniaxial compressive strength of the consolidated standard sand obtained by mixing and consolidating the compounded liquids of Table-2 with standard sand.

From the results of Table-3, it can be seen that the dibasic calcium phosphate and the dibasic magnesium phosphate having the compounding numbers 16 and 19 (invention) of Table-2 show higher strength than other cases.

The calcium salt and magnesium salt of phosphoric acid according to the present invention are not limited to the dibasic phosphate, and almost the same results can be obtained with the dibasic phosphate and the tribasic phosphate.

Further, the primary, secondary and tertiary phosphates may be used in combination with each other.

In addition, in actually injecting the chemical solution according to the present invention into the ground, for example, by adding and mixing the phosphate to an acidic silicic acid aqueous solution having a pH of 3 or less obtained by mixing water glass and acid,
Of course, injecting this mixture into the ground,
It is also possible to join and inject the phosphate aqueous solution with the acidic silicic acid aqueous solution. (The pH value of the combined solution may be acidic, alkaline, or neutral.) Further, for example, using a double injection tube, the acidic silicic acid aqueous solution or the mixture containing phosphate is fed from one of the channels. , Water glass, alkaline salt, cement, and other alkalis are sent from the other pipe, and they are joined at the tip of the injection pipe to inject them as a quick-melting grout, and then a phosphate aqueous solution or salt is added to this. Or an alkaline accelerator is added, and the mixed solution is joined at any point of the injection system of the acidic silicic acid aqueous solution, and injected as a permeable grout having a long gelation time, and the chemical solution of the present invention is used as a chemical solution for a composite injection method. It can also be used.

〔The invention's effect〕

As described above, since the ground injection chemical according to the present invention contains an acidic silicic acid aqueous solution having a pH of 3 or less and a calcium salt or magnesium salt of phosphoric acid, it is easy to adjust the gelation time region for a long time and to consolidate. It is a chemical solution that is practically useful because it has high strength and the pH of groundwater does not change significantly.

[Brief description of drawings]

1 and 2 are graphs showing the addition amount of dicalcium phosphate to the acidic silicic acid aqueous solution and the corresponding changes in pH and gelation time.

Claims (1)

[Claims] 1. A chemical liquid for ground injection, which comprises mixing a calcium salt or magnesium salt of phosphoric acid with an acidic silicic acid aqueous solution having a pH of 3 or less obtained by treating water glass with an acid.