JP3402374B2 - How to improve soft soil - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for improving soft soil. Specifically, it relates to a method for improving the soil quality of the surface layer of a soft soil layer at the site where the surface layer is generated.

[0002]

2. Description of the Related Art Conventionally, soft soil generated in various places is discarded as industrial waste. Most of the waste disposal is landfill, but on the other hand, there is a constant social problem as there are many illegal dumpers out of the disposal costs of industrial waste. Further, depending on the type of soft soil, the fluidity is large, and therefore it may not be possible to carry it out by a normal dump truck. In Japanese Patent Laid-Open Publication No. 2-194891, a fluid showing a slump value of 5 cm or more generated from a tunnel construction site or the like. There is described a method of adding and kneading an anionic acrylic polymer dispersion liquid and lime or cement to a water-containing excavated residual soil, which has the property of eliminating fluidity.

However, the main purpose of the method is to reform the residual soil and enable it to be carried out to a dumping place by a dump truck, which is not sufficient for improving the strength of soft soil. On the other hand, in many residential land development sites and road construction sites, the soil layer may become weak like groundwater during work, like a paddy field, and it may be difficult to continue the work. In such cases, drying in the sun usually requires a few days off. Further, as a means for continuing the work, a method of adding lime, cement, etc. to the surface layer of the soil layer to increase the strength of the soil is also implemented, but the effect is not sufficient. Therefore, in general, most of the soft soil is replaced with good quality soil, and most of the carried soft soil is discarded as industrial waste as described above.

[0004]

SUMMARY OF THE INVENTION In view of the above situation, the problem to be solved by the present invention is to improve the soil quality of soft soil at the site where it is generated, and to remove the soft soil which has been largely discarded in the past. The point is to use it effectively and to improve the efficiency of field work.

[0005]

Means for Solving the Problems The inventors of the present invention have diligently studied the solution to the above problems, and as a result, by adding and mixing a specific component to soft soil, the strength of the soil layer is developed in a short time. The inventors have reached the present invention by discovering that soil can be reused without replacement. That is, the gist of the present invention is that the carboxyl group-containing water-soluble polymer powder is added and mixed to the surface layer of soft soil having a slump value of more than 4 cm at the site where the surface layer is generated, and then lime is added and mixed. There is a method for improving soft soil.

The present invention will be described in detail below. The improvement of the soft soil in the present invention is to improve the penetration strength of the soft soil so that it can be reused and to carry out a solidification treatment so as not to swell in water. The soft soil to be improved by the present invention is a soft soil having a slump value of more than 4 cm, especially a slump value of 5 to 25 cm, which is rich in fluidity and has a high water content ratio, which causes a hindrance to the construction as it is. It is such soil. The soil usually has a water content of 40 to 200.
%, Especially about 60 to 150%, but the water content varies depending on the soil quality even for the same soft soil. For example, sandy soil is soft even at a relatively low water content ratio of 40 to 60%, and even in the pure Kanto loam layer, it varies depending on the region and place.
Some of them become soft at ~ 150%. In addition, there is also 150% or more soft soil in the case of silty material containing a large amount of corrosive soil and rotten mud.

Here, the slump value means JIS A11.
It is a scale of fluidity measured by 01 (concrete slump test method). Actually, "slump cone" with a bottom surface of 20φcm, a top surface of 10φcm, a height of 30cm and an empty top and bottom is placed on a flat plate, and soil is applied from above. Is tampered with and the slump cone is pulled out upward, and the change in height from the upper surface (30 cm) is expressed in cm. The water content ratio is a value representing the ratio of the mass of soil water lost by oven drying at 110 ° C. to the oven dry mass of soil in percentage, and is measured by JIS A1203 (water content test method). It is a value.

As the soft soil to which the present invention is applied, general civil engineering such as water supply and sewerage construction, road construction and residential land development construction, and soft soil generated in construction construction are generally used. Also,
Landfill soil of cohesive mud generated by dredging work and shield excavation work is also included. The water-soluble polymer used in the present invention is usually a polymer capable of dissolving 1 g or more in at least 100 ml of water. The polymer has a carboxyl group as a hydrophilic group, and the monomer having a carboxyl group is usually 1 to 8 among all the monomer units constituting the polymer.
It is contained in an amount of 0% by mol, preferably 5 to 60% by mol. In addition, the carboxyl group may be present in either free acid or salt form.

Examples of salts include salts of alkali metals such as sodium and potassium, salts of alkaline earth metals such as calcium and magnesium, ammonium salts, amine salts such as alkylamines having 1 to 18 carbon atoms and alkanolamines. , And a mixture of two or more thereof, but an alkali metal salt is preferable. Examples of the water-soluble polymer include (meth) acrylic acid or a salt thereof and a (meth) acrylamide copolymer, maleic acid or a salt thereof and a vinyl acetate copolymer, itaconic acid or a salt thereof and (meth) Although there are copolymers with acrylamide, etc., a copolymer of (meth) acrylic acid or a salt thereof and (meth) acrylamide is preferable. Examples of the (meth) acrylamide-based polymer containing (meth) acrylic acid or a salt thereof include those obtained by copolymerizing (meth) acrylic acid or a salt thereof with (meth) acrylamide, and homopolymers of (meth) acrylamide. It may be partially hydrolyzed. Further, a copolymer obtained by combining the above-mentioned monomers may be used.

Further, in the above polymer, a monomer containing a sulfonic acid group as a hydrophilic group, such as vinyl sulfonic acid,
It may be a copolymer including allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid and salts thereof. Further, a hydrophobic monomer such as an olefin, an acrylic ester, or a vinyl ester may be contained so long as it does not impair the water solubility.

The molecular weight of the water-soluble polymer used in the present invention is usually 1,000,000 or more, preferably 5,000,000 or more. Although the production method is not particularly limited, it is generally a radical polymerization method, and solution polymerization using water or a lower alcohol as a solvent is adopted. The concentration of the monomer is usually 10% by weight or more, preferably 15 to 60% by weight. When a polymerization initiator is polymerized in an aqueous solvent, peroxides such as potassium persulfate and ammonium persulfate, and redox type initiators using them, N, N′-azobis- (2-amidinopropane) dihydrochloride Water-soluble radical polymerization initiators such as 4,4'-azobis- (4-cyanovalerate) -2-sodium are preferred. The amount of the radical polymerization initiator used is usually 0.00 based on the weight of the copolymerizable monomer mixture.
It is 5 to 5% by weight, preferably 0.05 to 0.5% by weight.

The method of polymerization is not particularly limited, but in aqueous solution polymerization, polymerization is carried out with stirring, polymerization is carried out in an adiabatic state by leaving it in a container, polymerization is carried out while removing heat in a sheet form,
A method of polymerizing in a water-in-oil emulsion or dispersion state is exemplified. As a method of standing and polymerizing, after removing oxygen from a predetermined monomer aqueous solution through nitrogen gas, the mixture is brought to a predetermined temperature, and a radical polymerization initiator is added and uniformly mixed. A holding method is exemplified.
The polymerization temperature is usually selected in the range of 10 to 150 ° C. according to the molecular weight of the desired polymer, but is preferably 40 to 90.
℃.

The polymer thus obtained is dried in a dryer as it is, or treated with a dehydrating agent, dried and pulverized,
Use powdered ones. In general, many products obtained by making a polymer into an emulsion or a liquid dispersion are commercially available. However, compared to powder products, such products do not show sufficient improvement effect on soft soil. Further, in the present invention, the average particle diameter of the above water-soluble polymer powder is 0.
05-0.4 mm, preferably 0.1-0.3 mm is used. Further, in consideration of operability, etc., the particle size distribution is such that particles having a particle size of more than 0.4 mm and particles having a particle size of less than 0.05 mm each have a total particle content of 15% by weight or less, preferably 10% by weight or less. It is recommended to use a well-equipped one. In order to obtain powder within such a range, sieving, mixing, etc. are carried out as necessary. If the particle size exceeds 0.4 mm, it takes time to develop the improvement effect, while if the particle size is less than 0.05 mm, particles tend to adhere to each other due to moisture absorption and become lumpy. Therefore, it is not preferable.

The lime used in the present invention is quick lime or slaked lime, preferably quick lime. As the quicklime, a commercially available product may be usually used, but it is obtained by baking and crushing bone shells of fish and shellfish generated from general food industry and households, and shells attached to cooling pipes such as power plants. The thing can also be used as quicklime. As described above, the amount of the additive to be used for the water-containing soil in the present invention is not particularly limited because it depends on the water content ratio of the water-containing soil (remaining soil) to be improved, but the carboxyl group-containing aqueous solution is used for the remaining soil. The content of the volatile polymer is usually 0.001 to 1% by weight, preferably 0.01 to 0.5% by weight. The amount of lime added is usually 0.2 to 20% by weight, preferably 0.5 to 10% by weight, based on the soft soil.

The mixing weight ratio of the water-soluble polymer and lime is usually 1: 1 to 1: 500, preferably 1: 2 to 1:
250. Further, if necessary, by adding and mixing fine aggregate or fly ash in soft soil first as the soft soil to be treated, when the method of the present invention is adopted, the strength of the soil or the soil bearing capacity is synergistic. It is particularly preferable because it is improved.

The fine aggregate which can be used in the present invention has an average particle size of usually 0.02 to 10 mm, preferably 0.1 to 5 m.
It is an aggregate of m. Examples of the fine aggregate include granular materials such as crushed concrete, sand, gravel, and crushed stone. As natural aggregates, those obtained from andesite, basalt, sandstone, etc. are preferable in addition to plutonic rocks. These fine aggregates are
Specific gravity is usually 2.0-3.0 g / cm ³ , JIS
The unit volume weight according to the standard test of A 1104 is usually 1500-2000 kg / cm ² .

The fly ash which can be used in the present invention is generally defined fly ash extracted from smoke-conducting gas of a pulverized coal combustion boiler, but it is usually generated in a coal-fired power plant. Coal ash is used. The composition of fly ash varies somewhat depending on the raw material coal, but as constituent components, it is usually 50 to 70% by weight of Sio ₂ , 10 to 40% by weight of Al ₂ O ₃ , and other Fe.
₂ O ₃ , CaO, MgO, etc. are contained.

When the above fine aggregate or fly ash is used, the amount used is usually 0.5 to 50% by weight, preferably 1 to 30% by weight, based on the soft soil. The additives to the soft soil used in the present invention are basically those described above, but as other optional components, hydraulic cement, gypsum and superabsorbent resin are used in combination to improve. The effect can be adjusted.

Next, a specific method of using the above-described soft soil improving component in the present invention will be described. In the present invention, in the soft soil layer to be treated, at the surface generation site,
First, add and mix the carboxyl group-containing water-soluble polymer,
Next, it is characterized by mixing lime. As the soft soil to be treated, as described above, fine aggregate or fly ash added and mixed may be used.

Further, in the addition and mixing treatment of the improving component to the soft soil, it is not necessary to carry out the soft soil from the site where the surface layer is generated, and the polymer may be directly sprayed on the surface layer of the soft soil at the site. Here, the surface layer in the layer of the soft soil is not particularly understood, but it usually means a portion at a depth of 1 to 5 m. The device used in the addition and mixing treatment is not particularly limited as long as the mixing efficiency is excellent.

For example, a normal backhoe can be used, but if the attachment at the tip is in the form of a plow, mixing and granulation are more efficient, and if necessary, a rotary stirrer may be attached. It is valid. Besides, an ordinary cultivator or the like can be used. In any case, if the polymer can be sufficiently mixed at the beginning, mud will be gradually granulated and the clod will disappear. If granulation is sufficient, the next step of adding and mixing lime will be efficient and can be processed in a very short time. Further, the strength of the improved soil after the above-mentioned treatment develops immediately after the treatment, but the strength is improved with time, and it is usually preferable to cure the soil for half a day or longer, particularly 3 days or longer.

[0022]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

(Evaluation Method) The penetration strength of the soil sample was measured by a Pken-type penetration tester devised by the Civil Engineering Research Institute of the Ministry of Construction. A tripod with a leg length of 200 cm, a cone bottom diameter of 30 mm, and a tip angle of 60 degrees with a tip cone of 25 mmφ is 100.
5 kg from a height of 50 cm on top of the cm penetration rod
The hammer was dropped, and the number of drops that penetrated 10 cm was measured. The higher the number of hits, the higher the ground strength. In addition, the condition of the improved soil was visually observed daily.

(Polymer used) The polymer used is shown in Table 1. The polymers used were all powders. In addition,
The reduced viscosity ηSP / C in the table is a value measured by an Ostwald viscometer at 25 ° C. in a solution of the polymer dissolved in 1N saline at a concentration of 0.1 g / dl.

[0025]

[Table 1]

Example 1 and Comparative Examples 1 to 3 On-site construction tests using a backhoe were carried out at a residential land development site in Aihara, Sagamihara City, Kanagawa Prefecture. Vertical width of 3m
We dug a 12m wide and 0.5m deep gravel and carried in soft soil mainly from the Kanto Loam layer that occurred from the adjacent site. It is divided into 4 parts in the width direction, one section is 9 m ² and soft soil is 4.5 m ^3.
Soil improvement treatment was performed as (about 6 t). The soft soil had a slump value of 19 cm and a water content of 92%.

The improved method was a mixing treatment using a 0.7 m ³ backhoe. In Example 1, 6 kg of Polymer A was sprayed for about ⅓, mixed for 10 minutes, and further ⅓ was repeated. At the end of mixing, the soil particles were associated and granulated, resulting in a free-flowing state. In the untreated area, the boots sink to the bottom when the boots are put in, but in this area, it does not sink, and it has been modified so that people can walk sufficiently. Next, 180 kg of quick lime was sprinkled on the surface, further mixed for 15 minutes with a backhoe, and the surface was lightly pressed with a bucket at the tip.

Comparative Example 1 is the result of mixing with quick lime alone for 30 minutes, and Comparative Example 2 is an example of the simple treatment with polymer A, which is the same as Example 1 except that quick lime is not added. I went. In addition, as Comparative Example 3, physical properties of the section of the raw material soil are also shown. The penetration strength was measured immediately after the test and after 4 days, and then after compacting the whole with a 0.7 m ³ backhoe and rolling. Although it rained in the early morning the day after the test,
The compartment of Example 1 had better drainage than the others.

The test results are summarized in Table 2. The numbers in the table represent the number of hammer hits required to penetrate 10 cm. The larger the number, the higher the ground strength and the better the improvement effect. Also, looking at the results after compaction, Example 1 shows that the number of impacts of 20 cm penetration from the surface of the ground is about twice that of 10 cm penetration, indicating that the compaction is evenly applied downward. On the other hand, in the case of the quick lime treatment of Comparative Example 1, only the surface is rolled,
It shows that the inside does not become solid.

[0030]

[Table 2]

Using the improved soil after 7 days of Example 1, JI
According to S A1210 (method for compaction of soil by tamping), improved soil was divided into 3 layers in a mold having an inner diameter of 15 cm, and each tamped with a 4.5 kg rammer 92 times to perform a tamping test. Next, JIS A1211
According to (CBR test method), CBR (California Bea
Ring ratio) A load-penetration amount curve was obtained with a tester, and a load (penetration strength) at a penetration amount of 2.5 mm was obtained, which was 11.5 kg / cm ² .

Examples 2 to 5 and Comparative Examples 4 to 9 An improvement test using a backhoe was conducted in the same way as in Example 1 at a construction site for landfilling paddy fields to construct a road in Ozaki Town, Hachioji City. did. The raw soil had a slump value of 5 cm and a water content ratio of 95.2%, and the soil was a highly viscous soil mixed with the Kanto loam layer of paddy soil.

The improvement test was carried out directly by making the scale of one section of the test the same as in Example 1. Example 2 is the result of the test using the polymer A, and Examples 3 to 5 are the polymers B, C, and
It is a test result using D. Comparative Examples 4 and 5 are polymer E,
It is a test result when F is used. Comparative Example 6 is Example 1
In place of Polymer A in Example 3, "Acofloc LAE-130E" 30% by weight emulsion polymer manufactured by Mitsui Cyanamid Co., Ltd., acrylamide / sodium acrylate = 70.
A sample having a 6 / 29.4 molar ratio and a reduced viscosity of 27.2.
This is the result of the same improvement treatment except that g was used.
Comparative Examples 7 and 8 are the results of the quicklime-only treatment and the polymer A-only treatment. Comparative Example 9 is the physical property of untreated soil. The penetration test was performed immediately after, 3 days after, and 7 days after, and the measurement was also performed by applying a rolling pressure. The test results are summarized in Table 3.

[0034]

[Table 3]

Example 6 and Comparative Examples 10 and 11 Example 6 was carried out except that 1.2 t of fine aggregate having an average particle size of 1.7 mm was premixed in the test section of Example 2 (about 6 t). It is a result of performing an improvement test with Polymer A and quick lime as in Example 2, and Comparative Example 10 is a case where the same treatment as in Example 6 was conducted except that Polymer A was not used. Example 11 is the untreated result of simply mixing fine aggregate.
The penetration test was performed immediately after and 3 days later, and the measurement was also performed by applying a rolling pressure. The test results are summarized in Table-4.

[0036]

[Table 4]

Example 7 and Comparative Examples 12 and 13 Example 7 was the same as Example 6 except that 600 kg of fly ash was premixed as in Example 6, except that polymer A was used.
And the result of an improvement test with quick lime, and Comparative Example 12 is a case where the treatment was performed in the same manner as in Example 7 except that the polymer A was not used. Comparative Example 13 is an untreated result obtained by only mixing fly ash. Penetration test immediately after and 3
The measurement was performed after a day, and the measurement was performed by applying a rolling pressure. The test results are summarized in Table-5.

[0038]

[Table 5]

[0039]

In the prior art, since the construction is difficult, the soft soil is replaced with good quality soil, and the soft soil is disposed of as industrial waste by landfill or partially unusable soft soil that has been subject to illegal dumping. Soil, by using the improved method of the present invention,
It can be improved on the spot without being taken out, and can be reused as a resource, and the work efficiency is greatly improved. In addition, fine aggregates that are currently in trouble, pottery, and fly ash generated in thermal power plants can also be used as resources.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09K 103: 00 C09K 103: 00 (72) Inventor Satoshi Nishijima 336 Ozaki-cho, Hachioji-shi, Tokyo Tokyo Environment Service Co., Ltd. (56 ) Reference JP 63-44097 (JP, A) JP 2-194891 (JP, A) JP 63-139973 (JP, A) JP 1-139198 (JP, A) JP 64-51198 (JP, A) JP 61-227899 (JP, A) JP 6-17054 (JP, A) JP 1-315400 (JP, A) JP 51-8250 (JP, B1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C09K 17 / 20,17 / 22 C09K 17 / 42,17 / 48 E02D 3/00

Claims (3)

(57) [Claims] 1. A soft soil characterized by adding a carboxyl group-containing water-soluble polymer powder to the surface layer of soft soil having a slump value exceeding 4 cm at the site where the surface layer is generated, and then adding and mixing lime. How to improve the soil. 2. A fine aggregate or fly ash is added to and mixed with the surface layer of soft soil having a slump value of more than 4 cm, and then a carboxyl group-containing water-soluble polymer powder is added and mixed, Furthermore, a method for improving soft soil, which comprises adding and mixing lime. 3. Soft soil having a slump value of 5 to 25 cm
The soft soil according to claim 1 or 2, characterized in that
Improvement method.