JPH0567730B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a ground injection method using water glass, and more particularly to a ground injection method capable of forming an integrated and strong foundation. [Conventional technology and its problems] Conventionally, as a ground injection method using water glass,
A construction method is known in which cement grout or cement-water glass grout is firstly injected, and then water glass grout is secondarily injected. However, in this construction method, the primary injection material penetrates only into the rough parts of the ground and cannot penetrate into the thin parts, so it can only be effective as a rough filler to restrain the ground, and only into the fine parts. A chemical reaction with the secondary injection material cannot be expected in the granular soil area. Also known is a construction method in which instant setting grout is injected as a primary injection material and then slow setting grout is secondarily injected. This primary injection material is injected in veins into the rough parts of the ground and cannot penetrate into the thin parts.
Therefore, the chemical reaction of both grouts in the ground could not be expected. Furthermore, a method is also known in which a reactive agent is injected into the ground in advance, and then a neutral water glass grout is injected into the injection area. However, in this method, because the gelation time of the neutral water glass grout is short, it is difficult for the grout to penetrate between the soil particles, and therefore, the reaction between the grout and the reactant is difficult to occur in the fine-grained soil parts of the ground. Improvement of the granular ground is insufficient. Furthermore, there is also known a construction method in which a strainer injection pipe is driven in when water glass is injected, and calcium chloride is injected through the injection pipe while the injection pipe is pulled up to cause the water glass and calcium chloride to react in the ground. However, with this method, highly viscous water glass is pushed outward when calcium chloride is injected, resulting in non-uniform solidification of water glass and calcium chloride in a certain area around the injection pipe. [Object of the Invention] Therefore, the object of the present invention is to provide a ground injection method that forms an integrated and strong ground and improves the drawbacks of the above-mentioned known techniques. [Summary of the Invention] In order to achieve the above-mentioned object, according to the present invention,
First, a grout with poor permeability is injected into the ground, then a non-cement reaction agent mixture is injected into this injection area, and then a water glass grout with good permeability with a pH of 9 or higher is injected into the injection area. It is characterized by injecting. [Specific Description of the Invention] The circumstances leading to the completion of the present invention are as follows. (1) If sand gel solidified with non-cement water glass grout in the alkaline region is immersed in curing water, the silica content of the water glass will leach out over time and its strength will decrease significantly over time. In particular, if the amount of reactant is reduced in order to prolong the gelation time, the gel will collapse within several tens of days. However, even with this type of sand gel, no decrease in strength is observed in curing water made of a non-cement-based reactant mixture, but rather the strength increases over time. (2) Even if the above-mentioned sand gel is cured in cement cement or cement-water glass gel, no improvement in strength can be obtained. (3) Infiltrate a water tank filled with sand with a non-cement reaction agent mixture in advance, and then add non-cement neutral water glass grout and alkaline non-cement water glass grout with a pH of 9 or higher (both are the same). When water glass concentration and gel time) were injected at the same injection pressure, the latter had a significantly larger penetration range. (4) A non-cement reaction agent mixture solution was infiltrated in advance into a water tank filled with sand, and then a water glass solution and an alkaline non-cement water glass grout with a pH of 9 or higher were injected under the same conditions as in (3) above. However, the latter was more homogeneous and had a sufficiently large solidification strength. (5) Water glass solution and
When non-cement water glass grout with a pH of 9 or higher was infiltrated and then a reactant aqueous solution was injected before the grout gelled, a homogeneous solid could not be obtained depending on the injection area and the strength was insufficient. I couldn't even get it. (6) Infiltrate the non-cement reaction agent mixture into a water tank filled with sand, and then adjust the pH to 9.
When the above alkaline non-cement water glass grout was injected under the same conditions as above, a homogeneous solid with significantly improved strength over time was obtained. (7) When cement grout or cement-water glass grout was injected in advance into a water tank filled with sand, and then non-cement water glass grout, which is alkaline with a pH of 9 or higher, was injected under the same conditions as above, solidification was observed. No improvement in the strength of the body over time was achieved. (8) When a non-cement based reactant aqueous solution was pre-infiltrated into a water tank filled with sand, and then cement based grout or cement-water glass grout was injected under the same conditions as above.
Only vein-like solids were obtained, and almost no sand gel was obtained. (9) In actual construction, when a non-cement reactant aqueous solution is injected into the ground, which consists of complex alternating layers with different permeability, and water glass grout with a pH of 9 or higher is injected, almost no improvement in durability is obtained. Nakatsuta. (10) Inject cement grout, cement-water glass grout, or instant setting water glass grout into the actual ground as the primary injection, then inject the non-cement reactant aqueous solution, and then
When the above water glass grout was injected secondarily, a significant improvement in durability was observed. Based on the circumstances described in (1) to (10) above, the above-mentioned objects of the present invention are achieved as follows. (b) As the primary injection, grout with poor permeability is first injected into the ground. This type of grout also includes suspended grout. This injection first fills the rough areas in the ground, thereby sealing up areas where the grout is likely to deviate and homogenizing the ground. (b) Next, a non-cement based reactant mixture is injected into the area where the first injection was performed, and is allowed to penetrate between the soil particles up to the fine-grained soil portion. Although the non-cement based reactant mixture has extremely good permeability, the parts that are likely to escape are already confined by the primary injection, so the injected reactant mixture is retained without escaping. (c) As a secondary injection, water glass grout with good permeability and a pH of 9 or more is injected in a manner overlapping the area into which the reactive agent mixture has been injected. At this time, the water glass grout pushes out the reactant mixture liquid to the periphery by the injection pressure, and permeates between the soil particles to replace it. At this time, the peripheral part of the water glass grout permeation area is first rapidly gelled by the reactant mixture, and then the inside is gelled, and as a result, the solidified part due to the secondary injection is immersed in the reactant mixture. It becomes infiltrated. after that,
The reactant mixture gradually penetrates into the solidified portion over time and reacts with unreacted water glass in the solidified portion,
All the silica in the water glass is precipitated, the reaction progresses, and an increase in strength is achieved. Furthermore, the reactant mixture also acts on the primary injection material, thereby increasing the strength or improving the durability of the primary injection material, thereby forming a solid foundation that is integrated as a whole. Hereinafter, the present invention will be specifically explained in detail through experiments. Experiment-1 The pH and gelation time of the mixed solution of No. 3 glass and the reactant were measured, and the results are shown in Table-1.

【table】

[Table] Experiment 2 Standard sand was consolidated using samples of composition Nos. 6, 10, 13, 16, and 23 in Table 1, and the resulting specimens (diameter 5 cm, length 10 cm) were soaked in water. The SiO ₂ content in the curing water was measured after curing in water introduction 1, and the cumulative amount of leached SiO ₂ relative to the total amount of SiO ₂ in the solidification chemical solution was measured, and changes over time in the leaching rate were investigated. (Table-2)
The numbers in Table 2 are leaching rate (%)/uniaxial compressive strength (Kg/cm ² ). Moreover, in Table-2, "-" represents collapse.

[Table] Experiment 3 A similar experiment was conducted using a 20% by weight solution of aluminum chloride as the curing water in Experiment 2, and the results are shown in Table 3.

[Table] Experiment-4 Sand gel (consolidated standard sand) consolidated using formulation No. 10 in the same manner as in Experiment-2 was mixed with various reactants.
After curing with a 20% by weight solution, the SiO ₂ leaching rate and strength were measured after 28 days, and the results are shown in Table 4.

【table】

[Table] Experiment-5 100g of Portland cement was mixed into the curing water in the same manner as in Experiment-2, and then the sand gel of composition No. 10 was cured, and the unconfined compressive strength after 28 days was measured to be 1.6Kg/cm ² showed that. This shows that no improvement effect regarding durability can be obtained. Experiment 6 Using the same direction as Experiment 5, 100 cm ³ of the gelled material of formulation No. 11 was crushed and mixed into the curing water. In addition, 100 cm ³ of cement-water glass gel was crushed and mixed into the curing water. Cement - water glass gel
The composition per 100 ^cm3 is: No. 3 water glass 25 c.c. Cement 50 g Water The rest. When the unconfined compressive strength of these was measured after 28 days, Blend No. 11 showed 1.5 Kg/ ^cm2 , and cement-water glass gelatinized product showed 1.6 Kg/ ^cm2 .
None of these had any effect of improving durability. Experiment 7 After saturating the sand in the aquarium with a 20% calcium chloride solution, grouts of formulations No. 15 and 16 were injected with a water head difference of 30 cm until no longer penetrated, and the size of the solids was examined one week later. However, in formulation No. 15, the diameter is approximately 20
cm, and with formulation No. 16, a solidification diameter of approximately 45 cm was obtained.
Formulation No. 16 shows a more significant penetration effect. A similar experiment was conducted using Formulation Nos. 19 and 20, and the diameter of Formulation No. 19 was approximately 15 cm, and the diameter of Formulation No. 20 was approximately 23 cm. From the above, it was found that under the same conditions, when the pH is neutral, the permeation range is narrow, but when the pH is alkaline, 9 or higher, the permeation range is extremely wide. This is because if the injection liquid is a water glass mixture containing a gelling reactant and the pH is alkaline, the reaction between the reactant in the ground and the injection liquid will occur due to the presence of alkali in the injection liquid. This seems to be because it becomes more gradual. Experiment 8 In the same manner as Experiment 7, a 20% by volume aqueous solution of No. 3 water glass and grout of formulation No. 21 were injected. In the former case, a heterogeneous solid body with a diameter of 10 to 25 cm was obtained, whereas in the latter case, a nearly spherical solid body with a diameter of 30 cm was obtained. In addition, the unconfined compressive strength of the former is 5Kg/
^cm2 , while that of the latter was 9.5Kg/ ^cm2 . From the above, it can be seen that it is necessary for the injection liquid to be a compounded liquid having a pH of 9 or higher and containing a gelling reactant in order to achieve homogeneous and strong solidification. Experiment-9 After saturating the sand in the aquarium with a 20% by volume aqueous No. 3 water glass solution and injecting a 20% calcium chloride solution with a water head difference of 30 cm, the strength of the solids around the injection hole was measured one week later. When measured, it showed an unconfined compressive strength of 2 Kg/cm ² . Also, mix the sand in the aquarium in the same way.
After being saturated with the No. 21 mixture, a 20% calcium chloride solution was injected before the mixture gelled, and the strength of the solids around the injection hole was measured one week later, and the result was 2.6Kg/cm. It showed an unconfined compressive strength of ² . If you inject the water glass mixture and then inject the reactant, the reactant will push the water glass mixture outward, which will dilute the water glass concentration around the injection tube and reduce its strength. On the other hand, in the opposite case as in Experiment 8, the reactant located in the periphery gradually penetrates into the solidified body of the water glass mixture around the injection tube over time, and the reaction progresses. Recognize. Experiment-10 Cement grout (100
50 g of cement per cc, remaining water) or 500 g of cement-water glass grout (same as Experiment 6)
After injecting cc, one grout of composition No. 10 was injected in the same place, excavated one week later, and the unconfined compressive strength was measured 28 days after the injection, and the results are shown in Table 5. .

[Table] Table 5 shows that even if cement grout or cement-water glass grout is used as the primary injection material, the aging strength of the secondary injection material will not be improved. Experiment-11 After saturating the sand in the water tank with a 20% calcium chloride solution, 500 c.c. of the cement grout and cement-water glass grout from Experiment-10 were injected, and excavation was carried out one week later, but the results solidified in veins. However, it was not possible to obtain an overall solidified body due to infiltration between soil particles. In other words, it was found that this method does not improve the consolidation effect due to penetration between soil particles. Experiment-12 Add 20% aluminum chloride solution to the sand in the aquarium.
After pouring, add 50% of water glass grout with formulation No. 10.
A comparative experiment was conducted in which the water glass grout of composition No. 10 was injected (experiment-A), and after gelling, 20% aluminum chloride solution was injected five times (experiment-B). . In addition, when 5 injections of 20% aluminum chloride solution and then 5 injections of water glass grout of formulation No. 21 were made (Experiment-C), and after injection of 5 water glass grouts of formulation No. 21 without gelation. to 20
A test was also conducted in which 5% aluminum chloride solution was injected (Experiment-D). Seven days, 28 days, and three months after injection, excavations were made around the injection pipe, samples were taken, and the unconfined compressive strength and pH were measured. The results are shown in Table 6.

[Table] From Table 6, it can be seen that the increase in strength over time, that is, durability, is largely related to the injection order, the pH of the solidified material, the atmosphere, etc. In other words, if you inject the reactant in advance and then inject the water glass grout, the polymerization of water glass will be promoted in an alkaline atmosphere even if the reactant's pH is acidic, which will improve durability and increase strength. make a big impact. On the other hand, when water glass grout is injected and then an acidic reactant is injected, the PH value of the solidified material becomes acidic or neutral, and the strength does not increase significantly.
For comparison, in Experiment B, the strength was measured for 7 days without injecting the reactant later, and the result was 2.8.
It showed 1.5. From this, in Experiment B, when water glass grout was injected and the reactant was injected after gelling, the solidified material became a neutral atmosphere, but the solidified material was destroyed, and the broken part was difficult to repair after that. It seems that the strength will be lower. In addition, in Experiment D, when the acidic reactant was injected before the water glass grout gelled, the water glass grout was pushed outward and the area around the injection tube was made up mainly of the reactant rather than the water glass grout, resulting in a medium to acidic state. This indicates that the atmosphere becomes more stable, making it difficult for hard caking to form around the injection tube. Experiment-13 Cement grout (same as Experiment-10), cement-water glass grout (same as Experiment-6), and the formulation in Table-1 as the primary injection material in a water tank filled with sand.
After injecting 500 c.c. of Nos. 2, 11, and 22, 500 c.c. of the 20% by weight solution of the reactant shown in Table 4 was injected, and then as secondary injection materials, the mixture No. 6 shown in Table 1, One grout of No. 10, 13, 16, or 21 was injected, and the unconfined compressive strength qu (Kg/cm ² ) was measured one week, 28 days, and three months later, and the results are shown in Table 7.

〔Effect of the invention〕

The present invention described above can have the following effects. (1) The long-term strength of water glass grout in the alkaline region, which has a long gelation time, is significantly improved, and the durability of the solid body is improved. (2) Obtain a sufficiently wide range of penetration and consolidation effects. (3) Preventing the secondary injection material from deviating outside the injection range,
Obtain a homogeneous solid within a predetermined range.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 both show a specific example of an injection pipe for carrying out the construction method of the present invention. 1... Outer pipe, 2... Inner pipe, 3... Upper discharge port,
4... lower discharge port, 7... valve, 8... spring.

Claims (1)

[Claims] 1 First, a grout with poor permeability is injected into the ground, then a non-cement based reactant mixture is injected into this injection area, and then water glass grout with good permeability with a pH of 9 or higher is added into this injection area. A ground injection method characterized by injection.