JPS5940181B2 - Soil stabilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a soil stabilization method using polyurethane.

A chemical solution containing acrylamide-based, water-glass-based, chromium lignin-based, polyamine-based, urea-based, etc. as main ingredients, with addition of auxiliary agents, hardening agents, stabilizers, etc., is injected into soil such as leaky ground or soft ground to improve soil quality. In the method of stabilizing water, the chemical solution to be injected is a two-component type, which has a large number of components, and the procedure for preparing the chemical solution at the construction site is complicated. Since there were drawbacks such as the chemical solution being washed away, we used a polyethylene oxide compound having two or more hydroxyl groups at the end and a molecular weight of 1,000 to 20,000, and an organic incyanate having two or more incyanate groups at the end. A ground stabilization method (Tokuko Showa) in which a water-soluble urethane prepolymer with terminal isocyanate groups obtained by reacting with a compound is injected into the ground to form a solidified substance mainly composed of water. 4
8-25205) is known.

However, in the above-mentioned known method, a water-soluble urethane prepolymer mixed with a large amount of water is injected into the soil, so the urethane prepolymer necessary to solidify even the excess water is injected into the soil. In addition, there was the trouble of having to transport water to the work site.In order to solve the problems of the above-mentioned known construction methods, powdered urethane prepolymer was used instead of liquid urethane prepolymer. It has been proposed to use a prepolymer, for example, a powdered urethane prepolymer made by uniformly mixing powdered additives with a liquid water-soluble urethane prepolymer (Japanese Patent Publication No. 53-129184, Japanese Patent Publication No. 53-129184, 53-293
49) is known.

The powdered additives include carbon black,
Examples include erosil, aluminum hydroxide, silica, cement, etc., and mixtures of two or more thereof. However, the above-mentioned known powder additive has a specific surface area of 20
When mixed with the above-mentioned polymer, it tends to settle and is difficult to disperse uniformly even by stirring.
There was a drawback. This invention eliminates the above drawbacks by using hollow inorganic powder as the powder additive.

That is, in this invention, after uniformly mixing a hollow inorganic powder with a specific surface area of 3/7 or less into a small amount of liquid urethane prepolymer, an organic incyanate compound and a polyol are further added, and the mixture is stirred and mixed. 80 parts by weight of hollow inorganic powder per 100 parts by weight of the total urethane prepolymer.
This soil stabilization method is characterized by mixing powdered polyurethane containing ~160 parts by weight into moist soil.

The hollow inorganic powder used in this invention (hereinafter abbreviated as hollow powder) is a light powder containing single air bubbles, and examples thereof include glass balloons, foamed glass spheres, and fly-ash spheres. Shirasu balloons are particularly suitable.

The above-mentioned hollow inorganic powder has a specific surface area of 3rrI/7 or less, on average in the range of 0.4 to 2.0 m2/7, and the size of the powder is non-uniform in the range of 5 to 200μ. The average particle size is preferably 60 to 80μ. Further, the liquid urethane prepolymer in this invention is an initial reaction product of an organic isocyanate compound and a polyol, and has an isocyanate group at the end.

As the organic isocyanate compound, tolylene diisocyanate and 1,4-bisphenylmethane diisocyanate are used, but generally when tolylene diisocyanate is used, it has excellent hydrophilicity, and 1,4-bisphenylmethane diisocyanate is used. When diisocyanates are used, the compressive strength of the hardened soil tends to be higher than that of the soil. Therefore, it is preferable to use a mixture of the above two types of isocyanate compounds. The polyol, which is another raw material for the urethane prepolymer, is a polyether polyol mainly composed of oxyethylene chains, and its average molecular weight is 1000.
Above, preferably 2,000 to 6,000 is preferred in order to make the urethane prepolymer water-soluble. The polyol is preferably a copolymer of ethylene oxide and another alkylene oxide, containing 60% or more of ethylene oxide. The organic isocyanate compound and polyol are mixed and reacted at room temperature to 100°C or lower to produce a liquid urethane prepolymer with a viscosity of 1000 to 3000 cps, and the hollow powder is added to the liquid urethane prepolymer. Mix. When the hollow powder is a shirasu balloon, its specific gravity is 0.8 to 1.2, which is similar to that of the urethane prepolymer, so the hollow powder does not settle in the prepolymer and is uniformly distributed. The urethane prepolymer is then mixed with the urethane prepolymer. The amount of hollow powder mixed with 100 parts by weight of the above urethane prepolymer is 80 to 80 parts by weight.
160 parts by weight, and if the mixed amount is less than 80 parts by weight, the urethane prepolymer will not be sufficiently powdered, and if it exceeds 160 parts by weight, a large amount of powdered urethane prepolymer will be used. Therefore, it is not economically advisable.

When mixing the hollow powder into the liquid urethane prepolymer, the viscosity of the liquid urethane prepolymer is relatively high.
In addition, the smaller the amount of prepolymer, the more uniform the mixing will be, so after uniformly mixing the hollow powder with a relatively small amount of urethane prepolymer, the above-mentioned organic isocyanate compound and polyol are further added. It is necessary to cause the reaction to reach a predetermined mixing amount of hollow powder. The amount of the urethane prepolymer with which the hollow powder is mixed is appropriately adjusted depending on the amount of the hollow powder mixed in the powdered urethane prepolymer and the specific surface area of the hollow powder. It is preferably in the range of 10 to 30% by weight based on the amount of the polymer, and the remaining 70 to 90% by weight of the urethane prepolymer is added with a low viscosity organic isocyanate compound and polyol, which are raw materials for producing the urethane prepolymer. The reaction is carried out while mixing. The amount of hollow powder mixed with 100 parts by weight of the above-mentioned whole urethane prepolymer is 80 to 16
If the amount is 0 parts by weight and the amount mixed is less than 80 parts by weight, the urethane prepolymer will not be sufficiently powdered.
If it exceeds 0 parts by weight, the amount of powdered urethane prepolymer used will increase, which is not economically advisable.

Generally, when coating the surface of a hollow powder with a liquid, if the viscosity of the liquid is low, the liquid will penetrate into the interior of the hollow powder. When mixed with the liquid urethane prepolymer, the liquid urethane prepolymer does not penetrate into the interior of the hollow powder.
It is sprinkled on the surface of the hollow powder to coat it.

After that, a low-viscosity organic isocyanate compound and a polyol are added and reacted with stirring, so that the urethane prepolymer produced by the reaction is uniformly coated on the surface of the hollow powder, and is coated with a relatively small amount of hollow powder. A powdered urethane prepolymer is thus obtained. If the surface of the powdered prepolymer is slightly sticky, adding finely divided silica and mixing will quickly lose the stickiness and make it a smooth powder in a short time.
When the above-mentioned powdered urethane prepolymer 1 is mixed into soil containing a large amount of water and pressurized, some of the water in the soil reacts with the isocyanate groups of the urethane prepolymer 1, causing the urethane prepolymer 1 to become highly concentrated. It is molecularized and solidifies the soil, and the excess water is hydrated within the urethane resin to form an integrated solidified product.

As a result, soil structures such as roadbeds and embankments are stably strengthened,
This prevents erosion and weakening of the cells. In addition, by adjusting the mixing ratio of the powdered urethane prepolymer and the degree of pressurization, it is possible to change the density of the solidified material, imparting impermeability to water and preventing water leakage and groundwater rise. It can be prevented. Furthermore, when the solidified material is porous, the heat retention effect increases and freezing can be prevented. The ratio of mixing powdered urethane prepolymer into moist soil is as follows:
It is appropriately set depending on the moisture content of the soil, the content rate of the urethane prepolymer in the powdered urethane prepolymer, and the like.
For example, soil moisture content is 20%, urethane prepolymer is
If the amount of hollow powder is 125 parts by weight to 00 parts by weight, even 12 parts by weight of powdered urethane prepolymer will solidify to 100 parts by weight of wet soil, but if the amount is 5 parts by weight, the solidified material will be solidified. The compressive strength increases, and up to 20 parts by weight, the compressive strength increases in proportion to the amount mixed. If the amount of powdered urethane prepolymer 1 mixed with 100 parts by weight of wet soil exceeds 20 parts by weight, carbon dioxide gas is generated due to the reaction between the isocyanate groups of urethane prepolymer 1 and water, resulting in a decrease in the density of the solidified material. , the compressive strength also tends to decrease slightly. According to this invention, since hollow inorganic powder is used when producing the powdered urethane prepolymer, the hollow powder and the prepolymer are uniformly mixed,
Furthermore, the urethane prepolymer can be pulverized by mixing a relatively small amount of hollow powder.

Furthermore, since the hollow inorganic powder has a wide particle size distribution, the cured product is densely consolidated and has a high compressive strength. Furthermore, secondary aggregation during storage of the powdered urethane prepolymer is reduced. Examples of the present invention will be described below.

In addition, in the examples, "parts" indicates "parts by weight." Example 1 (a) Production of liquid urethane prepolymer The ratio of ethylene oxide to propylene oxide is 90
:10, 75 parts of polyether polyol with an average molecular weight of 3000, and tolylene diisocyanate (TDI
-80) into a three-necked separable flask equipped with a stirrer, thermometer, and inert gas inlet, and reacted at 90 to 100°C for 3 hours while passing inert gas to form a liquid urethane. A polymer was produced.

The free NCO content of this urethane prepolymer is 10%.
The viscosity was 1600 cpS (25°C). (b) Production of powdered urethane prepolymer In the same separable flask as above, 14 parts of the liquid urethane prepolymer of above (a) and a previously dehydrated Shirasu balloon (specific surface area: 0.6C7, apparent specific gravity: 0.30 , average particle size 70μ) and thoroughly stirred and mixed. Next, 21 parts of the above TDI-80 and 32 parts of polyethylene glycol having an average molecular weight of 4000 were added with vigorous stirring.
Mix for 1 hour at ~30°C, then store at 45°C in a sealed container.
A smooth powdered urethane prepolymer was obtained by aging at ~50°C for 10 to 18 hours.

The free NCO content of this powdered urethane prepolymer is about 7%, and the shirasu balloon content is 120 parts per 100 parts of the urethane prepolymer. When 5 parts of water was added to 1 part of this powdered urethane prepolymer and mixed, the urethane prepolymer quickly dispersed in the water, formed a hydrogel and hardened in about 3 minutes. (
c) Soil stabilization test A spray of water was uniformly sprinkled on Toyoura standard sand and left to stand for several days to obtain wet sand with a moisture content of 20%.

To 100 parts of this wet sand, 15 parts of the powdered urethane prepolymer of (b) above was quickly and uniformly mixed, and JlS-A-
The mixture was packed by hand into a sampler specified in 1216, the sides and the bottom surface of the soil were fixed using a hand vise, and the mixture was left to stand for 24 hours to obtain a solidified material. The unconfined compressive strength of this sample is 4.3k
9/CrfL and 9.8 kg/Cd after being left for 7 days.
It was hot. Note that even when this solidified material was immersed in water, its shape did not collapse. Example 2 To 15 parts of (a) liquid urethane prepolymer in Example 1 above, 100 parts of the same Shirasu balloon as in Example 1 was added and mixed thoroughly in the same manner as in Example 1, and then TDI-
80 and 43 parts of the same ethylene oxide/propylene oxide copolymer polyol used in the production of the liquid prepolymer of Example 1 above were added, and the mixture was heated at 30°C.
Stir vigorously for 30 minutes, then transfer to a sealed container and heat at 40°C.
After aging for 5 hours, 20 parts of fine silica powder was added and uniformly dispersed to obtain a smooth powdered urethane prepolymer with small particle size.

Claims (1)

[Claims] 1. After uniformly mixing a hollow inorganic powder with a specific surface area of 3 m^2/g or less into a small amount of liquid urethane prepolymer, an organic isocyanate compound and a polyol are further added, and the mixture is stirred and reacted. 1. A method for stabilizing soil quality, which comprises mixing into moist soil a powdered urethane prepolymer containing 80 to 160 parts by weight of hollow inorganic powder based on 100 parts by weight of the total urethane prepolymer. 2. The soil stabilization method according to claim 1, wherein the polyol that is a raw material for the liquid urethane prepolymer is a polyether polyol containing ethylene oxide as a main component.