JPS6050839B2 - Method for solidifying and stabilizing peat soil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for solidifying and stabilizing peat soil.

Conventionally, peat soil has an extremely high water content and therefore has almost no bearing capacity, so in order to improve the bearing capacity of peat soil, the only method used has been to replace the surface layer with soil.

However, this method is not a preferable method because it is rare for good quality soil to exist near peat soil, the cost of transporting quality soil is high, and it only improves the surface layer. Therefore, it is possible to improve the surface layer by mixing cement into peat soil, or by injecting cement milk deep into peat soil.
Because it contains a large amount of substances such as lignin, humic acid, and fatty acids that have an adverse effect on the solidification and hardening of cement, it cannot be solidified and stabilized. In view of these circumstances, the present inventors have conducted various studies on methods for solidifying and stabilizing peat soil, and have found that mixing cement and alkaline earth metal chlorides with peat soil solidifies and stabilizes the peat soil. Furthermore, it was found that the solidification and stabilization of So layer peat soil was promoted by mixing cement, alkaline earth metals, and alkaline earth metal oxides or hydroxides.

Hereinafter, two representative examples among the experimental examples conducted by the present inventors will be explained.

Experimental Example 1 The peat soil used in the experiment was from Sapporo, Hokkaido, with a water content of 950%, a pH of 5.5, and a composition of substances other than water: 12% lignin, 5% humic acid, and 5% fat. 21 fatty acids 5
%, 63% fibrous organic matter and 15% inorganic matter such as volcanic ash and mirt.

To this, as shown in column (a) of Table 1, 35% by weight of ordinary Bortland cement with calcium chloride added in various proportions (all 1% below are 1% by weight). ) and pour this mixture into a diameter
Filling and molding into a cylindrical mold of crrL x height 10CrrL 2
Column (b) of the same table shows the results of the uniaxial compressive strength test of the specimens which were demolded from the mold and then cured in water until the specified age.

Column (c) of the same table shows the test specimens obtained by mixing ordinary Bortland cement with calcium chloride added in various proportions and 10% quicklime added to the added amount of calcium chloride at 35%. The results of the uniaxial 7 compressive strength test are also shown.

From the results in column (b) of Table 1, when 5 to 50% of calcium chloride is added to cement and mixed into peat soil, the unconfined compressive strength of the solidified peat soil increases when the concentration exceeds 10%. This is especially true when calcium is added at 30% and 40%, and when 50% is added, the strength at 1 to 3 days of age is 1.
It is larger than 0% addition, but 1 at 28 and 90 days of wood age.
It can be seen that the amount is smaller than when 0% addition is made.

Also, from the results in column (c) of Table 1, 5 to 50% of calcium chloride was added to cement, and 10% of calcium chloride was added to cement.
It can be seen that when % of quicklime is mixed into peat soil, the unconfined compressive strength is greater at all ages than when calcium chloride is added to cement.

From the above, columns (b) and (c) of Table 1 show that when the amount of calcium chloride added to cement is 10% or more, the solidified solid strength of peat soil becomes high, but when the amount of calcium chloride added to cement is 10% or more, Not only does the strength of the long-term materials at 28 and 90 days decrease, but the amount of calcium chloride used also increases, which is uneconomical, so it is better to add 10 to 40%.

Experimental Example 2 In Experimental Example 1, ordinary Bortland cement with 10 to 50% calcium chloride added, and 10% quicklime added to the calcium chloride, had a strong effect on calcium chloride for solidification of peat soil. It was found that 40% calcium chloride was added to cement, and the same peat used in Experimental Example 1 was added with various amounts of quicklime to calcium chloride. The unconfined compressive strength when mixed with quality soil is as shown in Table 2.

From the results in Table 2, 40% calcium chloride was added to the cement.
Add quicklime to 10-20% of calcium chloride.
It has been observed that when a mixture of calcium chloride and calcium chloride added to peaty soil is mixed, it exhibits an even greater unconfined compressive strength than when only calcium chloride is added to cement.

In addition, the present inventors used alkaline earth metal chlorides such as magnesium chloride, chloride, and barium instead of calcium chloride used in Experimental Examples 1 and 2, and alkaline earth metals such as magnesium oxide and barium oxide instead of quicklime. One or more of oxides of similar metals or hydroxides of alkaline earth metals such as slaked lime, magnesium hydroxide, barium hydroxide, etc. are used to produce ordinary Boltland cement, early strength Boltland cement, and ultra early strength Boltland cement. It has been confirmed that when cements such as silica cement, blast furnace cement, and fly ash cement are mixed into peat soil, the same trends as shown in Table 1 or 2 are observed.

The present invention is based on the above findings, and the first invention is characterized in that cement and alkaline earth metal chlorides are mixed into peat soil, and the second invention is characterized in that: This is a method for solidifying and stabilizing peat soil, which is characterized by mixing cement, alkaline earth metal chloride, alkaline earth metal oxide or hydroxide into peat soil.

In the present invention, calcium chloride, magnesium chloride,
Alkaline earth metal chlorides such as barium chloride should be added in an amount of 10% or more, preferably 10 to 40%, based on the cement, and alkaline earth metal chlorides should be added in an amount of 10% or more, preferably 10% or more, based on the cement. In addition, oxides of alkaline earth metals such as quicklime, magnesium oxide, barium oxide, and hydroxides of alkaline earth metals such as slaked lime, magnesium hydroxide, barium hydroxide, etc. One or more of the following are added to peat soil in an amount of 10 to 20% based on CaQ relative to alkaline earth metal chloride.

In the present invention, the cement, alkaline earth metal chloride, oxide, or hydroxide used as a solidification stabilizer for peat soil is mixed in advance before being mixed into peat soil. Alternatively, they may be added and mixed separately at the time of mixing.

Examples of the method of the present invention are shown below, but the method of solidifying and stabilizing peat soil is not limited to the methods of the examples.

Example 1 In Sapporo City, Hokkaido, at a depth of 4 m. When building a road in a housing complex on a peat layer with an N value of 0 and an unconfined compressive strength of 0.03k9/Cltl water content of 950%, we added 30% calcium chloride to ordinary boltland cement and added water to improve the roadbed. This slurry was made into a 1:1 slurry, and this slurry was injected over the entire surface of the subgrade improvement section to a depth of 4 m at a ratio of 300 kg per 1 d of peat soil using a high-pressure jet.
7 days after injection, N value 10-12, unconfined compressive strength 2.0-2
．． I was able to improve it to 2k9/d.

In addition, when only cement was injected in the same manner as above, the N value was scuttling 7 days after injection.

Example 2 In Tomakomai City, Hokkaido, the water content is approximately 700%,
A peat layer with a single axial compressive strength of 0.04k9/Crl is used as a solidification stabilizer using ultra-early strength Bortland cement with 20% magnesium chloride added and 15% slaked lime as a solidification stabilizer. 3505k9 per 1d of peat soil using a high pressure jet of slurry with a stabilizer ratio of 1.0
When injected at a ratio of , the unconfined compressive strength 7 days after injection was 3.0k9/C! Improved to l.

Example 3 When burying a drain pipe in peat soil with a water content of 750% and an unconfined compressive strength of 0.05 kg/d in Nagareyama City, Chiba Prefecture,
2 parts of ordinary boltland cement, 5 parts by weight of calcium chloride, and 0.75 parts by weight of quicklime were each added individually to 10 parts of excavated peat soil and mixed with a forced stirring mixer to cover the drain pipe. It was used for

Claims (1)

[Scope of Claims] 1. A method for solidifying and stabilizing peat soil, which comprises mixing cement and an alkaline earth metal chloride in an amount of 10% by weight or more based on the cement. 2. Claim 1, in which cement is mixed with an alkaline earth metal chloride in an amount of 10 to 40% by weight based on the cement.
Method for solidifying and stabilizing peat soil as described in Section 1. 3 Claim 1 in which the alkaline earth metal chloride is calcium chloride, magnesium chloride, or barium chloride
Section 2 is the method for solidifying and stabilizing peat soil described in Section 2. 4 In peat soil, cement and alkaline earth metal chlorides of 10% by weight or more based on the cement, and alkaline earth metal oxides of 10 to 20% by weight calculated as CaO based on the alkaline earth metal chlorides, or A method for solidifying and stabilizing peat soil, characterized by mixing it with hydroxide. 5 Cement and cement with 10 to 40% by weight of alkaline earth metal chloride and alkaline earth metal chloride with 10 to 20% by weight of alkaline earth metal oxide or hydroxide in terms of CaO. A method for solidifying and stabilizing peat soil according to claim 4, which comprises mixing the following: 6 Claim 4, wherein the alkaline earth metal chloride is calcium chloride, magnesium chloride, or barium chloride.
The method for solidifying and stabilizing peat soil according to paragraph 5 or paragraph 5. 7. The method for solidifying and stabilizing peat soil according to claim 4 or 5, wherein the alkaline earth metal oxide is quicklime, magnesium oxide, or barium oxide. 8. The method for solidifying and stabilizing peat soil according to claim 4 or 5, wherein the alkaline earth metal hydroxide is slaked lime, magnesium hydroxide, or barium hydroxide.