JPH0216352B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a chemical injection method for uniformly and strongly consolidating or stopping water in soft or leaking ground. Soft ground is usually formed by a complex interposition of coarse-grained soil and fine-grained soil, and it is difficult to homogeneously solidify such ground by injecting an injection chemical into the ground. is necessary. In addition, due to the recent environmental conservation and water quality conservation issues in construction work, it is desired from the viewpoint of pollution prevention that the injected water glass grout solidify reliably at the point where it is injected without deviating from the injection target area. To achieve this objective, multiple tubes are used to fill the voids around the injection tube with low-permeability flash setting grout to form a packer, which prevents the injected grout from slipping out, and subsequently The grout with good permeability penetrates between the particles and solidifies in the thin areas where the grout with poor permeability could not penetrate, which is injected by overlapping the good grouts, thereby ensuring that the area to be injected is infiltrated and solidified. A construction method (composite injection method) is being developed. The present invention uses grout with poor permeability (hereinafter simply referred to as "instant setting grout") and grout with good permeability (hereinafter simply referred to as "permeable grout") in the above construction method.
), and the combination of the two makes the effects of the composite injection method even more pronounced. Both instant setting grout and permeable grout are based on a strongly acidic water glass solution (hereinafter simply referred to as "strongly acidic water glass solution") obtained by adding and mixing an aqueous water glass solution to an acidic reactant. PH by mixing the combined aqueous solutions together.
Grout that maintains a short gelation time by adjusting it to an alkaline range of 8.5 to 10.5 is used as flash-setting grout.
A grout whose pH is adjusted to a non-alkaline state, that is, an acidic range of 8 or less, preferably 5 or less, and more preferably 2.5 to 5.0, and which maintains a long gelation time, is referred to as a permeable grout. Instant setting grout has the following excellent properties. (1) Compared to conventional caking in the alkaline region using an inorganic curing agent, there is less syneresis water and the caking rate is good. Therefore, there is little alkali leaching and the solidification strength is also excellent. (2) Compared to the method of solidifying a strongly acidic water glass solution with water glass or an alkaline agent in a neutral or strong acid region, the instant solid state can be maintained over a wider range and preparation is easier. Since permeable grout is a chemical solution injected in a non-alkaline region, preferably an acidic region, it has low viscosity and excellent permeability until gelation occurs, and the gelation time ranges over a wide range from several minutes to several hours. Although the gelation time is long, there is little syneresis water, and therefore both the consolidation rate and consolidation strength are excellent. However, the instant setting grout itself exhibits weak alkalinity, and although it has excellent setting properties, it cannot be said with certainty that there is no leaching of alkaline components. In addition, the permeable grout itself is neutral to acidic, and although it will inevitably solidify sooner or later, if it is injected alone, it may deviate from rough areas or around the injection pipe before solidifying. There is a risk of In the so-called composite injection method in which instant setting grout and permeable grout are injected in the same injection area, for example, instant setting is performed mainly in the gap between the multiple pipes and the injection hole wall, or in weak or rough areas around the injection hole. Since the permeable grout is injected after filling with the permeable grout, the permeable grout becomes slightly alkaline due to the alkaline content of the permeable grout while the permeable grout and the permeable grout are in contact with each other. The PH shifts to the side, promoting gelation, or a neutralization reaction occurs with the acidic content of the permeable grout, and the alkaline content of instant-setting grout is consumed, so there is no concern about leaching of the alkaline content. It disappears. In addition, permeable grout continues to move from an acidic region to a neutral region or from a neutral region to a slightly alkaline region, shortening the gelation time and solidifying more firmly, so it can quickly set without deviation. It penetrates between particles and solidifies in the narrow areas where grout cannot penetrate. As described above, the instant setting grout and the permeable grout have excellent properties in themselves, and even more excellent effects can be exerted by the contact action between the two. Hereinafter, the present invention will be specifically explained in detail while showing examples. The consolidation rate indicates the percentage of the consolidated volume to the total volume. Table 1 shows the gelation time, consolidation rate, and homogel uniaxial compressive strength with respect to pH when a water glass aqueous solution (solution B) is added to a wide range of strongly acidic water glass solutions (solution A).

[Table] Here, the strongly acidic water glass solution of solution A was prepared by adding an aqueous solution of water glass to an aqueous sulfuric acid solution to have the final composition shown in the table. Table 1 shows that in experiments No. 5 to 10, 13, and 14, when the pH of the combined liquids of A and B is in the range of 8.5 to 10.5, almost instantaneous setting can be easily obtained, and there is little syneresis water. The solidification rate was good, the homogel strength was high, and an extremely stable solidified body was obtained. As the pH of the A/B combined solution becomes more acidic (Experiments Nos. 1 to 3 and 12), the gelation time becomes longer, and a solid in a constant instant solid state cannot be obtained. When the combined liquids of A and B in Experiment Nos. 11 and 15 become strongly alkaline (PH > 10.6), it is of course impossible to obtain an instant solid state, and both the solidification rate and homogel uniaxial compressive strength are extremely reduced. The instant setting grout used in the present invention is the grout in the range of Experiment Nos. 5 to 10, 13, 14, and 18 to 20 in Table 1. Table 2 shows experimental examples of the so-called permeable grout according to the present invention, in which the pH was adjusted to non-alkaline by combining the strongly acidic water glass solution (Liquid A) in Table 1 with water glass or an alkaline reactant (Liquid C). show. Examples of neutral range are shown in Table 1.
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[Table] In Table 2, any combined liquid of A and C with a pH of 5 or less shows an extremely low viscosity of 5C/P/S or less until just before it reaches gelation, and has excellent permeability. I found out that there was. Gelation time is PH 5
In the above cases (Experiments Nos. 22, 27, 32), gelation occurs rather quickly for a permeable grout in 1 to 2 minutes or less, and conversely, the pH is below 2.5 (Experiments Nos. 26, 31, 39). )
However, gelation tends to be too slow with gelation time of several hours or more, so the pH of permeable grout should be in the non-alkaline range, i.e. 8 or less, preferably 5 or less.
It can be seen that the pH is most preferably in the range of 5 to 2.5. A solidified body of the A-B combined liquid (instant setting grout) in Table-1 is made, and the solidified body is immersed in the same volume of the A-C combined liquid (permeable grout) in Table-2. Table 3 shows the results of measuring the physical properties of the solids and the penetrating liquid (A-C combined liquid) at that time.
Shown below.

[Table] Instant setting grout () and permeable grout ()
Although there are many combinations, some of them are listed in Table 3. After immersing the aggregate in () in the permeable grout in (), the pH changes from alkaline to neutral in the aggregate in (), and from acidic to neutral in the permeable grout in (). The strength of the aggregate () is strengthened and the gelation time of the permeable grout is shortened. In this way, the combination of instant setting grout and permeable grout is expected to solidify the ground to be poured more firmly and reliably. Therefore, there is a further reduction in the risk of deviation from the ground targeted for injection. Table 3 shows that the pH of instant setting grout () is 8.5 or less (Experiment No. 34, 35, 38, 40), 10.5 or more (Experiment No.
38, 43) also approaches neutrality by contact with permeable grout (), but depending on the combination with permeable grout (), there is a risk of leaving the neutral range (Practice No. 34, 38). , 39, 40, 43) or the permeable grout (2008), if the PH of the permeable grout (2000) deviates from the range of 2.5 to 5.0, the permeable grout itself cannot reach the neutral region. limited to a pH range that maintains This makes it possible to increase the strength more reliably, shorten the gelation time even if the gelation time is quite long for permeable grouts, and ensure sufficient permeation and consolidation. be able to. In the experimental example, water glass with a molar ratio of 3.5 was used as the water glass, and sodium bicarbonate was used as the alkaline reaction agent. In addition to sodium bicarbonate, common alkaline agents such as potassium bicarbonate, sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, caustic soda, and caustic potash can also be used as the agent. During actual construction, an injection pipe consisting of multiple pipes is inserted into the ground, and a strongly acidic water glass solution is constantly fed into the ground from one pipe, and when it is mixed with the strongly acidic water glass solution, the combined liquid pH of 8.5-10.5
A water glass aqueous solution adjusted so as to always maintain the above range is sent from another pipe, mixed with the strongly acidic water glass solution at the tip of the injection pipe, and then injected into the ground. The combined liquid is a so-called instant setting grout. Next, when the strongly acidic water glass solution is mixed with the water glass solution, a liquid made of a water glass solution, an alkaline reactant, or a combination of the two, which has been adjusted so that the pH of the combined liquid always remains in the non-alkaline range, is added from another tube. It is fed into the water, mixed with a strongly acidic water glass solution at the tip of the injection tube, and then injected into the ground. The combined liquid is a so-called permeable grout. In this way, using a strong acid water glass solution as a base, instant setting grout and permeable grout are first injected into the ground while moving the injection stage by moving the injection tube. to form a compact seal with a packer effect in the gap between the injection tube and the ground and in the gap around the injection tube resulting from moving the stage, thereby allowing the permeable grout to fill the gap around the injection tube. In addition to preventing leakage along the stage, instant setting grout is injected into rough areas, weak areas, and layer interfaces near the stage, and pretreatment is performed to prevent permeable grout from deviating outside the specified range. Then, the seal is broken into the area where the instant setting grout has been injected, and the permeable grout is injected in layers, and the permeable grout permeates between the particles and solidifies in the narrow areas where the instant setting grout could not penetrate. do. At this time, the PH of both grouts shifts to the neutral range due to mutual contact between the instant setting grout in the pH range of 8.5 to 10.5 and the permeable grout in the non-alkaline range, causing instant setting. The grout consolidates more firmly, and the permeable grout shortens the gelation time, prevents the grout from deviating outside the predetermined range, and makes the ground to be poured more solid and evenly consolidates the entire area.

Claims (1)

[Claims] 1 In the ground injection method of injecting a solidifying chemical into soft or leaking ground to solidify the ground, a water glass aqueous solution is mixed with an acidic reactant as the solidifying chemical, and the PH value of the mixed liquid is 2 or less, water Glass content is 20
Injection obtained by combining a water glass aqueous solution with a water glass content of 20 volume % or more with an acidic water glass aqueous solution obtained by adjusting the water glass content to 20 volume % or more, and adjusting the PH value of the combined solution to a range of 8.5 to 10.5. An injection drug solution obtained by mixing a water glass solution or an alkaline reactant with the acidic water glass solution, adjusting the PH value of the mixed solution to a non-alkaline range, and adjusting the gelation time to be longer than the injection drug solution. A chemical injection method characterized by injecting chemicals into the ground in combination with.