JPS5840384A - Stabilization of soft soil - Google Patents

Abstract

PURPOSE:To efficiently coagulate and stabilize soft soil contg. a large amt. of an org. material with addition of a small amt. of a coagulating agent, by using as the coagulating agent a cement to which a hydrated alkali silicate has been added. CONSTITUTION:To a cement such as portland cement or blast furnace cement, is added 0.5-30wt%, based on the total solids in the composition to be prepd., finely divided hydrated alkali silicate such as sodium silicate of SiO2/Na2O ratio about 0.5-4 and moisture content of about 5-30wt%, to prepare a coagulating agent. It is possible to effectively coagulate and stabilize soft soil by mixing the coagulating agent as such or as an aq. slurry with the soil.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing soft soil using a cement-silicate solidifying agent.

Hitherto, as solidifying agents for soft soils with a wide range of water content ratios, lime-based, cement-based, or modified products in which various slags and gypsums are added to both have been commonly used. However, with lime-based solidifying agents, sufficient strength cannot be obtained even if the amount added is increased for soft soils with a high water content ratio, for example, a water content ratio of 150 or more. Solidifying agents are commonly used.

However, even if cement-based or modified cement-based assimilating agents are used, in soft soils with high water content, it is often necessary to add large amounts of water that are not economically desirable; The method of strengthening soft ground by injecting water solution (water glass solution) as the main ingredient and cement, etc. as a hardening agent by injecting it into the ground or forcing it to mix with the soil is inexpensive and can be used in place of other chemical agents. It has been widely used in recent years because it can increase the strength of treated soil compared to conventional methods. In this method, the strength of the gelled product increases as the mixing ratio of hardening agent to water glass increases. Therefore, when using such agents to stabilize soil quality, in order to sufficiently increase the strength of the treated soil, the mixing ratio of the hardening agent should be increased; however, if too much is added, the gel time may be extremely short.
This not only makes operation difficult, but also causes uneven soil assimilation.

This phenomenon can be alleviated by increasing the dilution of the alkali silicate, but this also increases the water content of the soft soil, making it impractical.

The present inventors have conducted various studies to solve the above-mentioned problems, and have found that a composition in which hydrated alkali silicate powder is added to cement can be used in soils with a wide range of moisture content, especially in soils with a wide range of moisture content. When large amounts of organic matter are contained in large soft soils, strength development is quick even at a low additive amount, and the final strength is high, and depending on the type of clay mineral, it produces a stable solidified product. This discovery has led to the completion of the present invention.

That is, the present invention is a method for stabilizing soft soil, which is characterized by using a composition obtained by adding hydrated alkali silicate powder to cement as a solidifying agent for soft soil.

In this way, when hydrated alkali silicate powder is used instead of aqueous aqueous silicate solution, it promotes gelation on the surface of cement particles, which is moderate in cement-water systems, forms non-settling cement milk, and causes a breathing phenomenon in soil. It is recognized that it has the effect of suppressing the

The hydrated alkali silicate powder used in the method of the present invention is a medium during the transition from anhydrous alkali silicate to liquid alkali silicate, and is usually obtained by drying a water glass solution.

When the water content is less than 5% by weight, the dissolution rate in water is i! <3
If it exceeds 0.011%, the adhesive force of the powder becomes large and blocking tends to occur. Appropriate moisture content ranges are 5 to 30% by weight for sodium silicic acid salts and 10 to 30% by weight for potassium salts.
, about 10 to 20% by weight of lithium salt, especially 15
A range of 23% by weight is preferred. Alkali silicate (S
101/&O) molar ratio is 0.5 for sodium salt
~4.01 1.0-4.0 for potassium salt, 1.0 for lithium salt. S~9.0. The average particle size of the powder may be less than the average IW in order to maintain solubility and miscibility with cement (K), but it is usually in the range of several microns to several hundred microns. In addition, the appropriate mixing ratio with cement is about 0.5 to 30% by weight based on the total amount of solid content of cement, preferably 1
~20% by weight.

The cements used in the present invention include general-purpose cements such as Portland cement, blast furnace cement, and fly ash cement, as well as modified cements to which gypsum, calcium oxide, and the like are added.

To carry out the present invention, it is sufficient to mix into soft soil a composition prepared by mixing hydrated alkaline silicate powder with cement at the above ratio depending on the moisture content of the soil. A composition consisting of clear aluminum powder and cement may be used in the form of a slurry in water or low-concentration muddy water.If a water glass solution is used as in the past, it may be used separately from the cement during soil demolition. Unless poured and stirred, caking will occur instantaneously, but in the present invention, the hydrated alkali silicate powder and cement are combined in the presence of moisture to produce milk with a moderate gelation rate, so it is a one-component product. It becomes possible to pour it directly into the ground. 1 In addition, if the water glass solution and cement are separately injected into the ground at different times in order to avoid solidification, there will be a lot of time loss due to the duplication of mechanical mixing. There is a drawback of uniformity, which is due to complicated operation,
In addition, this is probably because the surface hardening rate of the cement particles is high, making it impossible to mix completely and producing a coarse gelled product. However, the method of the present invention is able to produce cement milk with an appropriate gelling rate as described above. This kind of phenomenon can be avoided. The method of the present invention is not only effective for stabilizing such soft ground, but also for stabilizing soil failure such as peatlands with weak surfaces, or for turning peatlands containing organic matter such as lunarization. It can be used effectively.

All percentages in the practical examples shown below are based on weight.

1! Peng Example 1 38f solidifying agents of various compositions were added and mixed to 250 fields of muddy water (water content = 2501, organic matter content 25% in solid content) collected from Ina, Hyogo Prefecture, and a diameter of 501. ．． , height 10
After filling into a 0.0 mm mold and curing at 20° C., the l-axis compressive strength was measured. Table 1 shows the results.

In addition, the average particle size of the hydrated sodium silicate powder is iooμ
, water content zi%, 5lot/NarO molar ratio 3.2 was used! -7 Table 1 Example 1 Solidifying agents sOP having various compositions were added and mixed to muddy water (water content 470, organic matter content in solids 1'8%) collected from Otsu Shigeru, Himeji City (water content ratio 470, organic content 1'8%) Example 1 ．． The uniaxial compressive strength was measured in the same manner. Table 2)
Show the results.

Table 2 Example 3゜Portland cement, No. 3 water glass (solid content 399!
j) or hydrated sodium silicate powder (water content 22%, average particle size 100μ, SiO/Nm, 0 molar ratio 3.2) or hydrated potassium silicate powder (water content 18%, average particle size Zooμ, S
A solidifying agent was prepared by mixing iO, 0 molar ratio 158) and water in the formulation shown in Table 3.

This slurry solidifying agent was mixed with the same muddy water 21 as in Example 2. Mixed with Ice, diameter 50mm, height Zo.

The mixture was filled into the mold (2), and after curing at a constant temperature of 20°C, the uniaxial compressive strength was measured.

Further, when the slurry-like solidifying agent was filled into a mold with a diameter of 20 m and a height of 505 m, and the mold was removed after 30 minutes, the average diameter of the slurry that had spread to the bottom was measured and used as a flow value.

The gel time is the time during which a gelation reaction with cement occurs, but the cement does not become solidified and solidification begins.

The above results are shown in Table 3.

As shown in the Examples above in Table 3, according to the method of the present invention, cement, modified cement,
Alternatively, it is possible to obtain a soil with greater strength without causing a negative binding phenomenon than when using a cement-water glass solution based composition.

Applicant: Osaka Soda Co., Ltd. Agent: Patent attorney Toru Monda

Claims (1)

[Claims] 1. A method for stabilizing soft soil, comprising using a composition obtained by adding hydrated alkali silicate powder to cement as a solidifying agent for soft soil.