JP2001241032A - Ground improving material, and ground improving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ground improving materials which restrict material separation due to breeding while improving the workability, in addition, various ground improving materials are available such as those preventing flow and loss to adjacent area after grouting to loose ground or those proving similar effects when sea water is used instead of fresh water for improving the ground. SOLUTION: A means of solving the troubles by this ground improving material comprises dry objects of the scale recovered by hot water from geothermal energy and a ground improving material made from a cement-based solidifying material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground improvement material which is added to and mixed with ground soil when improving soft ground, and a ground improvement method for improving soft ground.

[0002]

2. Description of the Related Art Among the ground improvement methods, there is a method of increasing the strength of the ground by injecting a slurry into the ground and stirring and mixing the same as in various deep-layer mixing processing methods. The composition of the slurry, that is, the weight ratio of water to the weight of the soil improvement material (hereinafter referred to as “water soil improvement material ratio”) depends on the performance of the pump for pumping the slurry. It must be high. In view of the above, a material whose flowability is ensured by setting the water ground improvement material ratio to 50 to 300% is used, and among them, a material whose flowability is improved to 100 to 250% is often used. Also,
Depending on the method of construction, the standard of the water ground improvement material ratio is determined. For example, the standard is 100% for the CDM method and 250% for the SMW method.

[0003] However, the slurry has a problem that if the ratio of the water ground improvement material is large, material separation occurs due to bleeding. In particular, when the water ground improvement material ratio is 80% or more,
Bleeding is likely to occur. If material separation due to bleeding occurs, construction failures such as a blockage of a pump that sends slurry into the ground, and construction failures such as insufficient strength and unevenness in strength due to the inability to supply a homogeneous slurry into the ground may occur. Cheap.

In the ground improvement method, if the ratio of the water ground improvement material is large, the viscosity of the slurry decreases, so that on a loose ground such as sand ground, the slurry mixed in the soft ground does not stay at a predetermined position. It becomes easy to be washed away to the surroundings. However, if the slurry flows to the surroundings, the strength of the soft ground cannot be improved, and a predetermined ground strength cannot be obtained.

Conventionally, bentonite is often used to solve the above problems. Bentonite, when kneaded with water, absorbs water and swells, and thus has the effect of suppressing bleeding.

[0006]

However, since bentonite is not only kneaded with water but also swells sufficiently to achieve the above-mentioned effects, it is difficult to mix bentonite and a cement-based solidification material at the same time. Is
Bentonite does not swell due to calcium ions and the like eluted from the cement-based solidifying material, and the above-described effects cannot be exhibited. Therefore, when using bentonite, before mixing with cement-based solidifying material,
Water and bentonite must be kneaded in advance to sufficiently swell the bentonite, and the slurry production process becomes two-stage, which complicates the entire ground improvement work. In addition, seawater is often used as water for slurry production due to on-site constraints, and there is a problem that even when seawater is used, bentonite does not swell sufficiently.

In a geothermal power plant, since scale in hot water spouting together with steam causes power generation efficiency to decrease, the scale is removed by means such as adding alkali to the spouted hot water. I have. However, no effective use method has been found for the scale recovered from the hot water at present, and its treatment is problematic.

In view of the above, the present invention provides a soil improvement material which suppresses material separation due to bleeding while improving workability, and which does not flow to the surroundings even when injected into a loose ground. It is an object of the present invention to provide a ground improvement material and a ground improvement method that have the same effect when using seawater instead of water.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and found that the scale is:
Focusing on the characteristic that amorphous silica is a main component and that a very bulky aggregate can be formed with fine particles, and as a result of further intensive studies to utilize this, it is possible to solve the above problem. I found it.

[0010] That is, a solution of the present invention is a ground improvement material characterized by containing a scale dried product recovered from geothermal hot water and a cement-based solidified material. Cement-based solidifying material is intended to be mixed with soil or similar material to harden it, and to reinforce a specific component of cement, or to add an active ingredient according to particle size adjustment or soil quality It is.

[0011] Further, the solution of the present invention is to mix a dried scale material recovered from geothermal hot water with a cement-based solidifying material, add water to form a slurry, and inject the slurry into the ground. It is in the characteristic ground improvement method.

[0012] Further, after mixing the scale recovered from geothermal hot water or a dried product of the scale with water, a cement-based solidifying material is mixed to form a slurry, and the slurry is injected into the ground. It is in the improved construction method.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The ground improvement material of the present invention is obtained by mixing a scale-dried product obtained from geothermal hot water with a cement-based solidified material.

The scale is mainly composed of amorphous silica, and is contained, for example, in hot water spouting together with steam in a geothermal power plant.

As the cement-based solidification material, a mixture of cement with gypsum (dihydrate, hemihydrate, anhydrous), slag, lime, etc. can be used. Examples include a mixture of gypsum, a mixture of cement, gypsum, and slag, and a mixture of cement, lime, and gypsum.

The bleeding can be effectively suppressed by adding 4 to 50% by weight of the scale based on the total amount of the ground improvement material on a dry matter basis. The amount of scale to be added may be appropriately determined in consideration of the ratio of the water ground improvement material. When the amount of the added scale is 4% by weight or less, the bleeding suppressing performance is small, and when the amount is 50% by weight or more, the fluidity of the slurry at the time of pouring decreases, and further, the strength of the improved ground decreases, which is not preferable.

Next, an embodiment of the soil improvement method according to the present invention will be described. In the soil improvement method, a slurry is prepared by mixing the scale, the cement-based solidifying material and water, and It is intended to improve the strength of the soft ground by injecting it into the ground soil, which is the object of the ground improvement, and mixing it by stirring.

Here, the slurry may be prepared by using a mixture of a dry scale and a cement-based solidifying material, such as the ground improvement material according to the present invention, using a dry scale, or wetting before drying. When a scale in a state (hereinafter, referred to as a wet scale) is used, a slurry can be prepared by various methods depending on the situation.

More specifically, a soil improvement material in which a dry scale and a cement-based solidification material are mixed in advance is prepared, and a method of adding water to the soil improvement material at the site to form a slurry is described. The slurry can be prepared by a method in which the dried scale and the cement-based solidification material are mixed on site, and water is further added to form a slurry. Further, as a method other than the above and other methods, a slurry can be prepared by a method similar to that of conventional bentonite, that is, a method of adding water to a dry or wet scale and further adding a cement-based solidifying material to form a slurry.

By injecting such a slurry (ground improvement material) into the ground and stirring and mixing it with the ground soil, the ground improvement material hardens together with the ground soil, so that the strength of the soft ground can be improved.

According to the soil improvement material and the soil improvement method according to the present invention, bleeding when the soil improvement material is made into a slurry can be prevented by mixing the scale, so that the construction such as blockage of the pump can be prevented. Trouble can be prevented. Further, by preventing material separation due to bleeding, variation in strength can be suppressed.

Further, since the slurry can be prepared by the above method or the above method, it is not necessary to swell the scale in advance like bentonite, and the production process can be simplified to one step. In addition, when a scale is used, seawater can be used instead of water, which makes it less likely to be affected by site restrictions. Also,
Also when preparing a slurry by the method described above, the scale does not need to be swollen in advance as compared with bentonite, and the time for preparing the slurry can be shortened.

Further, the addition of scale to the ground improvement material increases the viscosity of the slurry when the slurry is prepared. Therefore, even when the slurry is injected into a loose ground such as a sand ground, the slurry hardly flows to the surroundings, and remains at the injected position and hardens, so that the soft ground is surely hardened without sinking the ground. be able to.

Further, the present invention has a more remarkable effect in a method of improving a deep ground on a loose ground such as a sand ground. That is, when improving the deep ground, it is necessary to form the columnar body in a substantially vertical direction from the deep ground. However, if the slurry flows to the periphery, a solid columnar body cannot be formed. Therefore, since the viscosity of the slurry is increased as described above, the slurry does not flow out to the surroundings, and a solid columnar body can be formed.

Further, the strength of the ground after the ground improvement is not reduced, but rather improved.

[0026]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples.

<Example of Scale Production> Organic water was separated from the steam well of the geothermal power plant (location: production well No. 134, Onikobe Geothermal Power Station, Miyagi Prefecture, produced from a depth of 1455 m) through a wellhead separator. 20 mg / l of a precipitation accelerator ("Daidol EC" manufactured by Daido Kasei Kogyo Co., Ltd.) as an active ingredient
The scale added and precipitated in the precipitation tank was collected by filtration with a filter cloth.

<Test Example 1> Example A commercially available cement-based solidifying material ("Tuffloc Type 4" manufactured by Sumitomo Osaka Cement Co., Ltd.) was mixed with a dry scale at the following weight ratio to the total amount of the ground improvement material (hereinafter referred to as "scale mixing"). The mixture was mixed to obtain a ground improvement material, and the following amount of tap water was further added to each, and the mixture was stirred for 1 minute with a mixer to obtain a slurry of an example. Scale mixing ratio: 5%, 10%, 15%, 20% Water ground improvement material ratio: 50%, 100%, 150%, 2
00%, 250% Comparative Example The same amount of tap water was added to the above cement-based solidified material,
A slurry stirred for 1 minute with a mixer was used as a slurry of a comparative example. Test method A test was performed in accordance with JSCE-F522 "Testing method for bleeding rate and expansion rate of pre-packed concrete mortar (polyethylene bag method)". That is, immediately after stirring for 1 minute performed when preparing the samples of Examples and Comparative Examples, immediately poured into a polyethylene bag of 50 mmφ to a height of about 200 mm, and bleeding water generated after standing for 24 hours was collected and measured. The bleeding rate was a percentage of the total amount. Table 1 shows the results.

[0029]

[Table 1]

As shown in Table 1, it was found that bleeding hardly occurred in the slurries of Examples, and that bleeding was effectively suppressed by the addition of scale.

<Test Example 2> Example After kneading a scale in a wet state and water in advance,
Further, a commercially available cement-based solidifying material ("Tuffloc 3" manufactured by Sumisaka Cement Co., Ltd.) was mixed at the following ratio, and the mixture was stirred and kneaded for 1 minute with a mixer to obtain a slurry of an example. Scale mixing ratio: 5%, 10%, 15% Water ground improvement material ratio: 50%, 100%, 150%, 2
Comparative Example: The same amount of tap water was added to the cement-based solidified material, and the mixture was stirred for 1 minute with a mixer to obtain a slurry of the comparative example. Test method Table 2 shows the results of measuring the bleeding rate after 3 hours and 1 day in the same manner as in the above test method.

[0032]

[Table 2]

As shown in Table 2, even when the wet scale and the cement-based solidifying material are mixed in advance, adding 5% or more of the scale has an effect of preventing bleeding.

[0034] <Test Example 3> and soil improvement materials of Examples by mixing the following proportions of dry scales in example commercial cement solidifying material (Sumitomo Osaka Cement Co., Ltd. "Tafurokku type 3"), scale A material to which no was added was used as a ground improvement material of a comparative example. Scale mixing ratio: 5%, 10% Test method Using the ground improvement materials of the above Examples and Comparative Examples, a test piece was prepared according to the JGSST 823 “Method of preparing a test piece without compaction”, Geotechnical Society Standard
A strength test was carried out according to JGS T 511 “Method of uniaxial compression test of soil”. Here, the following was used as the sample soil. The results are shown in Table 3, FIGS. Sample soil: Silt from Osaka City, Osaka Prefecture, Sandy soil from Inba-gun, Chiba Prefecture Ground improvement material addition amount: 200 kg / sample soil m ³ (both sample soils) Water ground improvement material ratio: 200%

[0035]

[Table 3]

From Table 3 and FIGS. 1 and 2, it is clear that the use of the ground improvement material according to the present invention increases the strength as compared with the conventional ground improvement material.

[0037]

As described above, according to the ground improvement material or the ground improvement method according to the present invention, bleeding can be prevented when slurry is prepared, and workability can be improved. . Furthermore, since the viscosity of the slurry increases due to the scale, even when the slurry is injected into the ground, it does not easily flow away to the surroundings, and the ground can be surely improved,
This is particularly effective in improving the deep ground. In addition, there is an advantage that the scale generated by geothermal power generation can be effectively used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change over time in uniaxial compressive strength of a sample soil after addition of a ground improvement material.

FIG. 2 is a diagram showing a change with time of a uniaxial compressive strength of a sample soil after addition of a ground improvement material.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jun Shimizu 7-55 Minamionkajima, Taisho-ku, Osaka City F-term in the Cement Concrete Research Laboratory, Sumitomo Osaka Cement Co., Ltd. 2D040 AA01 AB01 CA01 CA10 CB03 4H026 CA01 CA06

Claims (3)

[Claims] 1. A ground improvement material comprising a scale dried product recovered from geothermal hot water and a cement-based solidifying material. 2. A ground improvement method comprising: mixing a dried scale material recovered from geothermal hot water with a cement-based solidifying material; adding water to form a slurry; and injecting the slurry into the ground. 3. A ground characterized by mixing a scale recovered from geothermal hot water or a dried product of the scale with water, mixing a cement-based solidifying material to form a slurry, and injecting the slurry into the ground. Improved construction method.