JPH0138431B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for improving peat (peat, black mud) ground. Conventionally, as a ground improvement method for the purpose of increasing the strength of soft, water-containing ground, a method of mixing dihydrite, finely quenched blast furnace slag, and cement with water-containing soft ground has been known (e.g., Japanese Patent Application Laid-Open No. 1983-1999) 102677, etc.). Certainly, this method is effective for improving water-containing soft ground such as clayey sludge deposited in the sea, ports, rivers, lakes, etc. However, it was found that this method could not be advantageously applied to the peat ground, which is the target of this treatment and has an extremely high amount of organic matter. The soil quality of the peat ground, which is the target of the ground improvement of the present invention, belongs to high organic soil according to the Japan Unified Classification. High organic soils in this engineering category include peat and black mud. Peat is the result of natural deposits of wet plants such as sphagnum moss, reeds, sedges, and sedges that wither and are not fully decomposed due to poor drainage, and contains plant fibers. In addition, black mud has more decomposition of organic matter than peat and is rich in amorphous humus. Peat ground, which is a highly organic soil, has the characteristics of extremely high compressibility and low shear strength, and its physical characteristics are completely different from clayey sludge and soft soil deposited in the sea, ports, rivers, lakes, etc. are different. Therefore, when constructing embankments for railways, roads, river embankments, housing development, etc. on such peat ground, it is necessary to perform some kind of ground improvement. Various methods have been proposed for improving peat ground. For example, the removal and replacement method, preloading, sand drain, sand compaction, quicklime pile method, deep mixing method, etc. are used, but the construction period is long, the noise and vibration are large, and the consolidation effect cannot be expected. It has drawbacks such as being uneconomical, and there is nothing to be satisfied with. Currently, the cheapest hydrous soil improvement technology is the method using dihydrite, rapidly cooled blast furnace slag, and cement, but even this method can economically improve peat ground. It's difficult to improve. As mentioned above, peat is an aggregate of fibers of dead plants or aggregates thereof, and has an apparent solidity mainly due to the intertwining of the fibers. Therefore, strength cannot be maintained only by intertwining the fibers. In order to improve peat soil so that it retains its strength, strength-increasing materials are evenly distributed within the pores of its intertwined fibers, where long-term stable and strong formations and adhesive substances are formed. It is necessary to carry out the production smoothly and to connect the formed skeletons to each other and the fibers either primarily or secondarily. However, because peat contains a large amount of humus and has a low PH value, the setting reaction of cement and the like is extremely inhibited, making it difficult to achieve this goal using known methods. Therefore, special techniques must be used to improve peat soil smoothly and economically. As a result of intensive research to develop these techniques, the inventors applied a pre-treatment agent made of red mud and a ground improvement agent made of dihydrate, finely quenched blast furnace slag, and Portland cement to peat ground. By adding and mixing, we succeeded in achieving this objective. That is, according to the present invention, to peat ground; a pre-treatment agent consisting of red mud and a ground improvement agent composed of three materials in the weight ratio range shown below, the total of which is 100 parts, is added.・Consists of mixing; the weight ratio of the pretreatment agent used is that of the ground improvement agent.
A method for improving peat soil is provided, characterized in that the amount is at least 15 parts per 100 parts. Soil improvement agent: 5 to 40 parts of dihydrite 15 to 65 parts of quenched blast furnace slag with a particle size of 100 to 1 μm 30 to 65 parts of Portland cement In the present invention, the filling of voids in peat ground and the peat ground improvement reaction are performed. In order to carry out the process smoothly, red mud is used as a pre-treatment agent. Since this red mud is composed of fine particles, it is easily dispersed evenly into the voids of the intertwined fibers, and also acts effectively as one of the raw materials for the soil improvement reaction. Red mud contains sodalite (3Na ₂ O・
3Al ₂ O ₃・5SiO ₂・nH ₂ O) and sodium aluminate, which are used to adjust the pH of the target peat ground.
It acts as a regulating agent and further contributes to various reactions with slaked lime, which is a by-product of the setting reaction of Portland cement, and other material components of ground improvement agents. Ground improvement reactions include (a) cation exchange reactions such as corrosion and fine soil particles, and (b) etrin guide (3CaO・Al ₂ O ₃・
3CaSO ₄・28~34H ₂ O) formation reaction, (c) formation reaction of tobermolite mineral-like phase (3CaO ・2SiO ₂・3H ₂ O), (d) formation of amorphous gel-like substance by various reactions, etc. The ethrine guide generation reaction (b), which uses an aluminum compound as the reaction raw material, reacts smoothly in peat soil without being affected by the harmful effects of humic acid contained in humus, and has the characteristic of forming the skeleton necessary for soil improvement. There is. Peat ground is highly organic soil containing plant fibers, so it has (a) low shear strength, (b) extremely high compressibility, (c) large porosity, and (d) water content ratio (weight) of 100.
The engineering properties are significantly different from clay soils, such as ~1200%. In order to understand this, the first example is a comparison between high organic soil and clay soil.
Shown in the table.

[Table] Furthermore, peat soil contains a large amount of organic components, and even when the amount is small, the content is more than 20% by weight. Therefore, it inevitably contains a large amount of humus, and its chemical characteristics are also significantly different from clayey soil. The cation exchange capacity is large (30-280meq/100g of humus) and the PH value is low. The pH value varies depending on the organic components of the peat ground, but is between 3.5 and 3.5.
It's in the 5.5 range. When improving soft soil using a known ground improvement agent, if the PH value of the target soil is low or contains a lot of humus, the setting reaction (hydration reaction) of cement will be prevented, and it will not be used as a ground improvement agent. functions will be weakened and it will be difficult to achieve its objectives. In the present invention, a pre-treatment agent made of red mud and a ground improvement agent made of dihydrate, blast furnace slag, and Portland cement are added and mixed with peat ground. As mentioned above, materials made of dihydrate, blast furnace slag, and portland cement are known as strength-increasing agents for hydrated soft soil, but the present inventors' research has shown that such strength-increasing agents It was confirmed that it was still insufficient as an improving agent. As a result of various studies aimed at improving this point, the present inventors have found that, as mentioned above, a pre-treatment agent consisting of red mud;
By adding a soil improvement agent consisting of three materials: water stone, blast furnace slag, and portland cement; it is possible to improve peat ground efficiently and extremely economically, and the resulting improved soil is of extremely high quality. I found that. Red mud, which is a pre-processing agent, is a large amount of by-product when alumina is extracted from bauxite, and is currently treated as industrial waste and disposed of by landfilling or dumping into the ocean. However, as environmental regulations become stricter, such red mud treatment becomes not only impossible, but also undesirable from the standpoint of effective resource utilization. According to the present invention, since a large amount of red mud, which is regarded as a nuisance as industrial waste, can be effectively utilized, the present invention has extremely great industrial significance. In the present invention, since the peat ground to be treated is acidic, it is most preferable to use alkaline red mud that is directly discharged from the Bayer process or the alumina production process. It is also used when the free alkali is neutralized to a pH of 8. Moreover, the state can be applied in any state such as a slurry state or a dehydrated state. The red mud itself, which is a by-product when extracting alumina from bauxite, contains free alkali and is therefore highly alkaline (PH
12 or more); its chemical composition varies depending on the type of raw bauxite and its processing conditions, but its physical composition is almost constant. The chemical composition of the dried one is Fe ₂ O ₃ 29-40%, Al ₂ O ₃ 17-24%,
_SiO2 13-19%, _Na2O6-10 %, _TiO2 2-8%,
CaO 1-4%, bound water 9-13%, and attached sodium hydroxide _Na2O 0.2-0.6%. In terms of mineral composition,
Sodium aluminosilicate (Na ₂ O・Al ₂ O ₃・
mSiO ₂・nH ₂ O) or sodalite compound [3
(Na ₂ O・Al ₂ O ₃・2SiO ₂ )2NaX〕(X: Cl, SO ₄
) is 50±4%, hematite and goethite (hematite: αFe ₂ O ₃ , goethite: αFe ₂ O ₃・H ₂ O) is 32±
3%, quartz (SiO ₂ ) 4±1%, anatase (TiO ₂ ) 6±1%, corundum (Al ₂ O ₃ ) 5
±1%, calcite 3±1%. The physical properties when wet and dry are shown in Table 2. When red mud (aluminum smelting residue) is transported via pipes, it is usually handled as a slurry with a solid concentration of 500 to 600 g/dil by diluting a cake-like product with a water content of 35 to 45% with water. Table 2 Moisture content when wet Approximately 40% Single particle <1μm Apparent viscosity 50~100cp When dry over PH 12 True specific gravity 2.90~2.95 Filled bulk specific gravity Lightly loaded 0.52 Heavy loaded 1.05 Apparent particle size (JIS A1204) 10~30μ Ratio Surface area (BET) method 20 to 40 m ² /g In the present invention, the red mud can be used in the form of slurry as described above, but if necessary, it can also be used after being dried. If the filtered cake-like red mud is dried using a flash dryer or the like, a dry powder with an attached water content of 1% or less can be easily obtained. In addition, in order to handle the red mud in the same way as general earth and sand during transportation and deposition, the red mud slurry discharged during the red mud separation process in the alumina manufacturing method is processed by removing water in a conventional manner. Agglomerated products with a void ratio of 1.5 or less have also been produced, but in this case, when using this as an additive, it is preferable to use it by pulverizing it or dispersing it in water. The particle size of the dihydrite used in the present invention is not particularly limited, and it can be used in powder or granular form.
In the case of the present invention, various by-product minerals including dihydrate mineral by-produced in the flue gas desulfurization process can be used in their recovered form. The present invention effectively utilizes such industrial waste or industrial by-products (including blast furnace slag, which will be described later) as a resource, and has excellent features in terms of ecology and economy. It is. In the present invention, dihydrite, finely quenched blast furnace slag, and portland cement, which are the soil improvement agent components, can be added and mixed simultaneously to peat ground, but it is more preferable to improve peat ground. It is also important to appropriately classify these components and specify the order of addition. According to the present invention, the following ground improvement agent is provided. Soil improvement agent [ ] (Additive 1) Additive A 2-water stone (Additive 2) Additive B Portland cement (B ₁ ) 40~
Mixture or non-mixture of 75% by weight and 60-25% by weight of fine blast furnace slag (B ₂ ) with a particle size of 100-1 μm Weight ratio of additives A and B Additive A/Additive B = 5/95-40/ 60 Soil improvement agent [] (Additive 1) Additive A' 10-65% by weight of 2-water stone (A ₁ ') and fine blast furnace slag (A ₂ ') with a particle size of 100-1 μm90-45
Mixed or unmixed (additive 2) in weight percent Additive B' Portland cement Weight ratio of additives A' and B' Additive A'/Additive B' = 70/30 to 35/65 Soil improvement of the present invention Fine quenched blast furnace slag, which is one of the materials for the agent, is made by quenching blast furnace slag (slag), a by-product from iron blast furnaces.
It is ground to 100μ or less. Rapid cooling of blast furnace slag is carried out by a wet method in which granulation is rapidly cooled with water, a semi-dry method using a small amount of water and air, and a dry method using only air. Generally, so-called blast furnace slag produced by a wet method is suitable as a raw material. This is slag, which is made by quenching slag, a byproduct of iron-making blast furnaces, with water and crushing it into sand or granules about 1 to 5 mm in size. This composition varies slightly depending on the composition of the iron ore, its blast furnace, and operating policy, but it is approximately as follows. _SiO2 30~35
%, _Al2O3 13 _~ 18%, CaO38~45%, _{Fe2O3 0.5} ~
1.0%, MgO3~6%, S0.5~1.0%, MnO0.5~
1.5%, _TiO2 0.5-1.0%. The finely quenched blast furnace slag used in the present invention has latent hydraulic properties that can exhibit hydraulic properties due to the stimulating action of alkali, sulfate, and the like. Such latent hydraulic properties can be obtained by rapidly cooling the blast furnace slag, avoiding its crystallization, and making it amorphous (glass-like) in which crystallization energy is stored internally. The crystalline material obtained by slowly cooling blast furnace slag is melilite (Gehlenite Ca ₂ Al ₂ SiO ₇
It is a dense crystalline material whose main constituent minerals are okermanite (Ca ₂ MgSi ₂ O ₇ solid solution) and calcium orthosilicate, and it is unsuitable because it has no latent hydraulic properties. In addition, this rapidly cooled blast furnace slag needs to be used in as fine a state as possible in order to be used as a reactant by uniformly dispersing it in the gaps between the intertwined fibers of the peat ground. Normally, coarse-grained quenched blast furnace slag of 1 to 5 mm is insufficiently dispersed into the intertwined fiber gaps that make up peat soil, and the surface area that contributes to soil strength-increasing reactions is too small, resulting in poor reactivity. This is inappropriate as it significantly lowers the temperature. In the case of the present invention,
It is preferable to use finely quenched blast furnace slag of 100 to 1 μm. In the present invention, by using such finely quenched blast furnace slag, advantageous ground improvement can be achieved. The Portland cement used in the present invention conforms to the Japanese Industrial Standard JIS R5210, and generally, among these, those conforming to ordinary Portland cement are used. However, depending on the ground treatment conditions, Portland cements conforming to standards such as moderate heat Portland cement, early strength Portland cement, and ultra early strength cement may be used alone or in combination. In the present invention, the composition ratios of additives 1 and 2 and their weight proportions in the above-mentioned soil improvement agents [] and [] were comprehensively found through experiments. Under conditions other than these, a comprehensive optimal balance ratio of the components cannot be obtained, the effect of increasing strength becomes small, and other problems occur. For example, if the proportion of Portland cement is too small, there will be too little Ca(OH) ₂ produced by its hydration reaction (solidification reaction), and this will trigger a reaction.The soil improvement method using finely quenched blast furnace slag is insufficient. Since it does not occur, the purpose cannot be achieved. In addition, if there is a shortage of dihydrate, not only will it be impossible to prevent the harmful effects of humus on the hydration reaction of Portland cement, but also the CaSO ₄ min. Because there is a shortage of
The purpose of ground improvement cannot be fully achieved. In the present invention, it is necessary to use a relatively large amount of red mud used as a pre-treatment agent, and the solid content in the peat ground (dry weight after drying the peat ground at 110°C) is 100 parts by weight. against at least 30
parts by weight, preferably 50 to 300 parts by weight. As mentioned above, peat ground has pores of entangled fibers, but when treating this peat ground with a pre-treatment agent made of red mud, it is necessary to add and mix it into the peat ground prior to Additive 2. As a result, the red mud particles fill the pores of the fibers, suppressing the negative effects of humus, etc., which are harmful to the setting reaction of the cement that is added later, and also improving the pH value of the peat ground. Therefore, the reaction of the additives added later occurs smoothly, and the peat ground is solidified while containing the fibers in the ground.
As a result, an efficient strength increase is achieved. It is also important to specify the amount of red mud, which is the pretreatment agent used in the present invention, relative to the amount of additives 1 and 2. Generally speaking, in order to increase the strength of peat ground, Expressed by solid weight, additive 1
It is used in a proportion of at least 15 parts, preferably 40 parts or more, and usually 60 to 200 parts based on 100 parts of the total weight of the two. Generally speaking, the higher the proportion of red mud used, the more preferable it is, but if it is too high, the soil improvement effect when Additives 1 and 2 are added will decrease. Therefore, if an excessive amount of red mud is used than necessary, it becomes necessary to increase the total amount of soil improving agent added in order to achieve the purpose, which is not economical. Therefore, the amount of red mud to be added is determined depending on the quality of the peat ground and the desired purpose of ground improvement, but the upper limit ratio should be 300 parts or less per 100 parts of the total weight of Additives 1 and 2. good. Furthermore, if the proportion of red mud used is too small, it will not be possible to achieve effective ground improvement, just as if the proportion is excessive. Therefore, the proportion of red mud needs to be at least 15 parts by weight, preferably 40 parts by weight or more, based on 100 parts of the total weight of Additives 1 and 2. In the present invention, the ground improvement agent [] or []
To effectively improve peat ground using
It is very important to add and mix red mud, which is a pre-treatment agent, to the peat ground before Additive 2 (Additive B or Additive B'), and add and mix Additive 2 to the peat ground last. is important. Preferred addition orders of the pre-treatment agent and additives 1 and 2 are as shown in (a) to (d) below. (a) After pre-treating the peat ground with red mud, additive 1 (additive A or additive A') and additive 2 (additive B or additive B') are sequentially added and mixed. (b) Additive 1 after pre-treatment of peat ground with red mud
and 2 are added and mixed at the same time. (c) Red mud, which is a pre-treatment agent, is added and mixed into the peat ground at the same time as Additive 1, and then Additive 2 is added and mixed.
Mix. (d) After adding and mixing Additive 1 to peat ground,
The pre-treatment agent and additive 2 are sequentially added and mixed. In this way, treating peat ground before adding and mixing Additive 2 not only prevents the harmful effects of humus and other harmful effects on the cement setting reaction, but also improves the PH value of the target soil. Peat ground becomes highly responsive to ground improvement. Therefore,
Next, when Additive 2 is added and mixed, Additive 1,
Various reactions occur in parallel between the components of 2, the red mud component, and the fine soil clay, and the skeleton necessary for ground improvement and the sticky amorphous gel-like substance that adheres it are created in the treated soil. It is formed. Therefore, the strength of the peat ground is increased and the desired ground improvement is achieved. As mentioned above, the reaction of the ground improvement according to the present invention is as follows.
(a) Ion exchange reaction of humus and fine soil particles, (b) Ettringite (3CaO・Al ₂ O ₃・3CaSO ₄・28～
32H ₂ O), (c) a pozzolanic reaction that produces a tobermolite mineral-like phase (3CaO 2SiO ₂ 3H ₂ O), and (d) the production of an amorphous gel substance through various reactions. In the method of the present invention, by subjecting peat ground to red mud treatment, it is possible to obtain a peat ground improvement effect that is significantly higher than that obtained by adding only Additives 1 and 2. As can be understood from the above description, it is not very desirable to add Additive 2 first or before adding red mud as a pre-treatment agent in terms of workability and soil improvement effect. Since Additive 2 contains Portland cement (Additive B') or Portland cement (Additive B), it is in a state that has an adverse effect on the hydration reaction of Portland cement, which triggers the various reactions necessary for soil improvement as described above. If handled, the soil improvement effect will be significantly reduced. As mentioned above, the peat ground to be improved is the following (a) which significantly inhibits the hydration reaction of Portland cement.
The situation is as shown in (b). Therefore, it is very important to add and mix Additive 2 to the peat ground in the preliminary treatment prior to Additive 2. (a) It is in an acidic state with a PH value of 3.5 to 5.5. (b) Contains a large amount of humus, which is undesirable as a contaminant. In addition, additive 2 (additive B) of soil improvement agent []
The B ₁ and B ₂ materials that make up the B 1 and B 2 materials, and the A ₁ ′ and A ₂ ′ materials that make up the Additive 1 (Additive A) of the soil improvement agent [] are from the beginning a mixture of these materials (B ₁ ′+B ₂ ′) and (A ₁ ′+A ₂ ′), but in some cases, each material may be added to the target ground in unmixed form.
They can also be mixed. In the present invention, additives 1 and 2 can be handled in the form of powder or slurry and added to peat ground. When improving peat soil, it is necessary to determine the blend or addition rate of the soil improvement agent necessary to obtain a predetermined strength. The strength of soil improvement is determined depending on the purpose, but the general required strength is uniaxial compressive strength, which is as low as 0.5 to 4 Kgf/cm ² ;
It is often in the range of 0.5 to 2 kgf/cm ² . The addition rate of the soil improver will vary depending on the type of peat ground to be improved and its water content, but the uniaxial compressive strength will be 0.5-2.
When improving the soil to Kgf/ ^cm2 , the total amount of additives 1 and 2 per 100 parts by weight of peat ground (solid content equivalent) is usually
Approximately 80 to 160 parts by weight may be added. The method of the present invention is not particularly limited by the water content ratio of peat ground, and the water content ratio is low
Not only 200% but also 500-1200 with high water content
It can also be advantageously applied to %. The present invention can be applied to any peat ground, and in this case, it can be applied regardless of whether the peat ground is near the surface of the land or in a deep layer.
For example, if peat soil is located near the surface of the land,
Peat soil and additives can be mixed using a bucket hoe, clam shell, propeller agitator, or the like as a mixing means. In addition, if the layer is deep, use an auger or the like to drill holes in the ground up to the peat layer, and at the same time send each additive through the holes into the peat layer to mix the additives and the surrounding peat.
Mixing can be done mechanically underground using a stirring blade attached to the bottom of the auger. The peat ground targeted for improvement is often covered with volcanic ash and other deposits, with a sandy silt layer underneath, but in such cases, if construction work permits, For example, it is preferable to mix this surface layer volcanic ash and a part of the lower sandy silt layer with peat and treat it by the method of the present invention. By performing such ground treatment, peat ground can be improved more effectively. When peat soil is improved according to the present invention, the resulting improved soil has the desired compressive strength, but more advantageously, it has some elasticity and even tensile strength etc. It will be an improved one. In other words, peat ground contains a large amount of undecomposed plant fiber as a component, and this fiber acts as a fiber reinforcing agent or filler during ground improvement, increasing the elasticity of the resulting improved ground. and provides increased tensile strength. Next, the present invention will be explained in detail with reference to examples. In the examples described later, the red mud to be added and mixed with peat is a cake-like product obtained by collecting aluminum smelting residue diluted with water and transported through piping at an aluminum smelting factory, and passing it through a vacuum. there was. The properties of this red mud are as follows. Average particle size 0.55μ Water content 66.2% Density 1.85g/cm ² PH 13.05 Composition SiO ₂ 26.8%, Al ₂ O ₃ 17.2% Fe ₂ O ₃ 36.9%, Na ₂ O 9.6% Also, as dihydrate , dihydrite powder (average particle size 53μ, water content 9) produced as a by-product in the flue gas desulfurization process
%, composition: CaO3 1.2%, SO ₃ 44.1%). In addition, material B ₂ that constitutes additive 2 (additive B) of finely quenched blast furnace slag [soil improvement agent], and material that constitutes additive 1 (additive A') of soil improvement agent []
A ₂ ′] was a commercially available fine blast furnace water slag (specific surface area 3600 to 4000 cm ² /g, i.e., average particle size approximately 4 μm, as measured by the Blaine method, composition: 32 to 35% SiO ₂ , 15 to 16% Al ₂ O _{3 )} . ,
CaO41~44%, MgO4~6%, Fe ₂ O ₃ 0.5~1.2%,
(S0.8-1.0%, which was glassy with almost no fine crystal material when observed under a polarizing microscope) was used.
In addition, material B ₁ constituting additive 2 (additive B) of ordinary Portland cement [soil improvement agent],
Additive 2 (additive B') of soil conditioner [] is a commercially available product (specific surface area 3300 cm ² /
g) was used. In addition, additive B and additive
A′ was used by uniformly mixing each predetermined material and amount. The peat sample used was peat (organic soil) from Omiya City, Saitama Prefecture, which had the following characteristics. Moisture content ratio 756% Apparent specific gravity (moisture content ratio 756%) 1.038 gf/cm ² PH value 4.5 Loss on ignition (organic content) 57.4% Example 1 For 1 m ³ of test peat (121 kg as solid content),
Red mud 150 (94Kg as dry red mud), 2 water stone 45
85 kg of finely quenched blast furnace water slag, and 85 kg of Portland cement were added and mixed to the test peat in various combinations and addition orders shown in Table 4. Next, this mixed sample was poured into a cylindrical mold with an inner diameter of 50 mm and a height of 100 mm, and after being cured for a predetermined period in a constant temperature and humidity incubator at 20 ± 1°C saturated humidity, the mold was removed and its uniaxial compressive strength The strength was measured according to JIS A1216T, 1979 (uniaxial compression test method for soil). The results are shown in Table 4. In addition, in order to compare the influence of the particle size of finely quenched blast furnace slag on the effectiveness of peat ground improvement, a similar test was conducted using coarse-grained blast furnace water slag. As a result, the uniaxial compressive strength of the improved soil was 20 to 15% of the strength when fine high water slag was used as the material. The particle size distribution of fine and coarse particles of the blast furnace water slag used is shown in Table 3.

【table】

[Table] Example 2 Applying red mud RM to the test peat using soil conditioner []
In the treatment method of Example 1, in which Additive B is added after Additive A and A are added at the same time, the total amount of Additives A and B added is
215Kg, Additive A and Additive B (Material B ₁ /Material
The test was conducted under the same conditions as in Example 1, except that the weight ratio of B ₂ (weight ratio = 50/50) was changed. As a result, the uniaxial compressive strength of the improved soil on the 7th day of age was 5th
It was as shown in the table.

【table】

[Table] Example 3 Weight ratio of material B ₁ (Portland cement) and material B ₂ (fine blast furnace water slag) constituting additive B in 45 kg of additive A and 170 kg of additive B in Example 2 B ₁ /B A test was conducted in the same manner as in Example 1 by changing ₂ . As a result, 1 of the improved soil on the 7th day of age.
The axial compressive strength was as shown in Table 6.

[Table] Example 4 Applying red mud RM to the test peat using soil conditioner []
Using the treatment method of Example 1 in which additive B' is added after adding A' and A' simultaneously, 130 kg of additive A'
The test was conducted in the same manner as in Example 1, with B'85 kg and varying the weight ratio of material _A1 ' (dihydrite) and material _A2 ' (fine blast furnace slag) that constitute additive A'. .
As a result, the uniaxial compressive strength of the improved soil on the 7th day of age was as shown in Table 7.

【table】

[Table] Example 5 Using soil improvement agent [], additive A' (material
The weight ratio of A ₁ ′ and material A ₂ ′ (A ₁ ′/A ₂ ′ = 30/70) and the total amount of additive B′ added was 180 kg, and the weight ratio of additives A′ and B′ was varied. The test was conducted in the same manner as in Example 4. As a result, the uniaxial compressive strength of the improved soil on the 7th day of age was as shown in Table 8.

[Table] Example 6 Additive A 45Kg, Additive B 170Kg in Example
(B ₁ /B ₂ = 50/50), a test was conducted using the method of Example 2 in which the amount of red mud RM added was varied from 0 to 300 with respect to 1 m ³ of test peat. As a result, the unconfined compressive strengths at 3 and 7 days of age were as shown in Table 9.

【table】

Claims (1)

[Claims] 1. For peat ground; consisting of a pre-treatment agent made of red mud and three materials in the weight ratio range shown below,
Peat is characterized by adding and mixing a specified soil improvement agent so that the total amount is 100 parts; the weight ratio of the pretreatment agent used is at least 15 parts to 100 parts of the soil improvement agent. Ground improvement method. Soil improvement agent: 5 to 40 parts of quartz stone 15 to 65 parts of quenched blast furnace slag with a particle size of 100 to 1 μm 30 to 65 parts of Portland cement 2 After adding and mixing the pre-treatment agent consisting of red mud to the peat ground Additive A consisting of dihydrite, Portland cement B ₁ , and particle size 100 to 1μ
It consists of adding and mixing additive B consisting of finely quenched blast furnace slag B ₂ and additive B at the same time or after additive A; materials B ₁ and B ₂ constituting additive B. The weight ratio of B ₁ /B ₂ is 40/60 to 75/25
within the range, the weight ratio A/B of additives A and B is 5/
The method of claim 1 in the range of 95 to 40/60. 3 For peat ground: Add and mix the pre-treatment agent consisting of red mud and Additive A consisting of dihydrite at the same time, or after Additive A; then add and mix the pre-treatment agent consisting of Portland cement B ₁ . Particle size 100~1μm
Additive B composed of finely quenched blast furnace slag _B2 is added and mixed; the weight ratio _B1 / _B2 of materials _B1 and _B2 constituting additive B is 40/60 to 75/
25, and the weight ratio A/B of additives A and B is in the range of 5/95 to 40/60.
Section method. 4 After adding and mixing _the pretreatment agent consisting of red mud to the peat ground;
Additive A′ consisting of ~1 μm fine quenched blast furnace slag A ₂ ′ and additive consisting of Portland cement.
It consists of adding and mixing additive B′ at the same time or after additive A′; the weight ratio of materials A ₁ ′ and A ₂ ′ constituting additive A′ is A ₁ ′/A ₂ ′ is from 10/90
The weight ratio of additives A′ and B′ is A′/ in the range 65/35.
The method of claim 1, wherein B' is in the range 70/30 to 35/65. 5 For peat ground: At the same time, a pre-treatment agent consisting of red mud and additive A' consisting of dihydrite slag _A1 ' and finely quenched blast furnace slag _A2 ' with a particle size of 100 to 1 μm, or additive A Add and mix the pre-treatment agent after '';
Then an additive consisting of portland cement
It consists of adding and mixing additive A′; the weight ratio of materials A ₁ ′ and A ₂ ′ that make _up additive A _′ is 10/
The method of claim 1, wherein the weight ratio A'/B' of additive A' and additive B' is in the range 70/30 to 35/65.