JPH051834B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to an artificial ground material made of flyash suitable for use as backfilling material, filler material, reclamation material, etc. to be put into reclaimed land such as artificial islands, sea walls, etc. "Conventional technology and its problems" Conventionally, sand has been mainly used as such an artificial ground material. However, artificial ground using sand has the following problems, and solutions to these problems have been awaited. The reclaimed sand deposited naturally on the reclaimed land of the artificial islands, seawalls, etc. has a specific gravity of 1.8 to 1.85.
Because of this, if the original ground beneath the artificial ground is soft, there is a high risk of large subsidence of the original ground or landslide destruction. Therefore, it will be necessary to significantly improve the original ground before adding landfill sand. It is virtually impossible to perform compaction and compaction at the time of inputting the reclaimed sand, so the reclaimed sand is left loosely deposited on the original ground after being input. Therefore, there is a risk that the artificial ground itself may sink due to various loads acting on the artificial ground after it has been deposited, and there is also a high risk that liquefaction of the ground may occur when a strong external force such as an earthquake is applied.
For this reason, it becomes necessary to perform ground improvement on the artificial ground itself formed on the original ground. Because reclaimed sand cannot be expected to harden or improve its self-reliance over time, the thickness of the reclaimed sand that has been put in, that is, the deeper the reclaimed depth, the more difficult it is to create an outer shell such as a cofferdam, seawall, etc. surrounding the reclaimed sand. The earth pressure acting on the wall also increases, making it necessary to construct a very strong outer shell wall. Furthermore, as mentioned above, when performing soil improvement on artificial ground, the accompanying pressure increase must also be taken into account. ``Means for Solving the Problems'' Therefore, the present invention aims to form an artificial ground material made of fly ash by mixing volcanic ash and water with fly ash as a main component, and to create an artificial ground material consisting of fly ash and the total dry weight of the fly ash and volcanic ash. The dry weight ratio of volcanic ash to volcanic ash is within the range of 30 to 60%, and
The above problem is attempted to be solved by setting the weight ratio of water to the total dry weight within the range of 40 to 60%. Hereinafter, the artificial ground material made of flyash of the present invention will be explained in detail. First, fly ash is collected from coal ash generated from coal-fired power plants and other coal-burning plants, and there are no particular limitations on its type or properties. This fly ash has pozzolanic activity similar to cement, and has the property of hardening itself by reacting with water. In addition, the fly ash has a specific gravity of about 1.55 when hardened by adding water, which is smaller than the reclaimed sand, so it is possible to form a lightweight artificial ground. Here, if the fly ash is left unused for a long period of time after being discharged from the coal-fired power plant, etc., the moisture content in the fly ash may increase, which may reduce the self-hardening properties of the fly ash. There is. Alternatively, due to construction conditions or the like, it may be necessary to make the formed artificial ground develop a predetermined strength in a short period of time. In such cases, it is preferable to add an appropriate amount of a curing aid such as cement or gypsum. The amount of this curing aid added is
For example, in the case of cement, the greater the amount of cement added, the greater the strength, but considering the versatility of the artificial ground material of this invention, we have developed a material that has sufficient strength as an artificial ground (normally 3 kgf/cm ² or more at 28 days). 2 to 4% by weight, based on the total dry weight of flyash and volcanic ash, is sufficient to obtain a high compressive strength. Water and volcanic ash are then added to this flyash to produce a slurry-like artificial ground material. That is, the fly ash itself is a powder, and as it is, it is difficult to compact and compact it underwater. Therefore, by using the fly ash as a slurry-like artificial ground material, the self-hardening properties of the fly ash eliminate the need for operations such as compaction, and also facilitate operations such as transportation.
As this water, in addition to clean water such as ordinary tap water and well water, natural water such as lake water and seawater can be used. Among these waters, seawater is preferable because it is easily available since the construction site is mainly located in a coastal area. The amount of water mixed is 40 to 60% by weight based on the total dry weight of fly ash and volcanic ash (if the hardening aid is added, this weight is also added).
is within the range of If the weight ratio of water is less than 40%, the slump value approaches 0 and fluidity deteriorates, making construction difficult. Similarly, the weight ratio of water is
If it exceeds 60%, the slump value increases, leading to material separation, resulting in a decrease in the strength of the artificial ground and an increase in the shrinkage rate. Further, a surfactant such as lignin sulfonic acid, hydroxy acid salt and its derivative, polyol and its derivative is added to the water as necessary. By adding this surfactant, the fluidity of the slurry-like artificial ground material can be improved and a uniform slurry reclaimed ground can be constructed. This volcanic ash is mixed for the purpose of uniformly kneading flyash, water, etc., increasing the amount of slurry-like artificial ground material, or adjusting the specific gravity of artificial ground material. That is, if a slurry-like artificial ground material is produced by kneading only fly ash and water, the fly ash and water will not be kneaded uniformly, and the fly ash will aggregate into lumps, forming so-called "clumps." Therefore, by mixing volcanic ash with the flyash and water, the formation of the "clumps" due to the coarse particles is suppressed and uniform kneading is promoted.
In addition, considering the production volume of fly ash and the distance from the production site to the construction site, it is uneconomical to compose a slurry-like artificial ground material only from fly ash and water, so we will use filler materials that can replace this fly ash. It is preferable to mix them appropriately.
In particular, the volcanic ash has a relatively high pozzolanic activity, although it is not as good as that of fly ash, and is therefore preferable as a fly ash replacement material. Furthermore, when building a tunnel using the shield construction method on the artificial ground of this invention, if the specific gravity of the ground around the shield excavator, including the artificial ground, is too light, it will be difficult to suppress the buoyancy of the tunnel by the weight of the upper ground. This may impede excavation or cause the tunnel to collapse. In this way, by mixing volcanic ash into the artificial ground material depending on its use, the specific gravity can be adjusted as appropriate. The mixed amount of volcanic ash is 30 to 60% in weight ratio of volcanic ash to the total dry weight of fly ash and volcanic ash. The dry weight ratio of volcanic ash is
If it is less than 30%, the specific gravity of the artificial ground will be too light and may have a negative impact on the surrounding area during or after construction. In addition, if the dry weight ratio of coarse particles exceeds 60%, the fly attachment will decrease by that amount.
There is no mention of the strength required for artificial ground. In this way, a predetermined amount of water and volcanic ash are mixed into the fly ash, hardening aids and surfactants are added as necessary, and these mixtures are kneaded using a normal kneading machine such as a forced mixer to achieve the intended purpose. It becomes a slurry-like artificial ground material. Then, this artificial ground material is used for reclamation by being put into the seabed or seawall that is the planned reclamation site through a transfer pipe, or it is placed on the ground as backfill soil or embankment to form an artificial ground. . The artificial ground formed in this way has a sufficient compressive strength of 3 kgf/cm ² or more, so there is no need to consider ground subsidence or liquefaction of the artificial ground itself. Therefore, ground improvement work on artificial ground becomes unnecessary. In addition, since the artificial ground material has self-hardening properties, there is no need to make the outer shell wall surrounding it strong, making construction easier. Furthermore, since the specific gravity of hardened artificial ground is lighter than the specific gravity of reclaimed sand, which is the conventional artificial ground material, subsidence of the original ground,
There is no risk of landslide destruction, and there is no need for ground improvement work on the original ground. In particular, volcanic ash is mixed into the artificial ground material, which makes it possible to uniformly mix the mixture of flyash, water, etc., and also allows the specific gravity of the artificial ground to be adjusted to match the construction conditions. Furthermore, since volcanic ash has the same pozzolanic activity as fly ash, it can be mixed as a fly ash replacement material. "Example" Hereinafter, the artificial ground material made of fly ash of the present invention will be explained in more detail with reference to examples, but the artificial ground material made of fly ash of the present invention is not limited to the examples shown below. Experimental Example Flyash, volcanic ash, cement, and water were kneaded to produce an artificial ground material made of flyash of the present invention. The fly ash was discharged from a coal-fired power plant in a wet state and was used without drying after being left for one week to one month. Table 1 shows the physical properties of the fly ash.

[Table] Coal produced in Hokkaido is used for these fly ash, and the calcium content is high at about 6%. Therefore, if the fly ash is discharged and stored in a dry state, it is presumed that due to the self-hardening properties of the fly ash, a compressive strength of about several kgf/cm ² will be developed when mixed with water. Volcanic ash is mixed as an extender for artificial ground material made of fly ash, produced in central Hokkaido, and after removing particles larger than 2 mm,
It was used in a wet state. The natural moisture content of the volcanic ash used in the experiment was 22.8%, the average particle size was 290 μm, and the specific gravity was
It is 2.59. Due to the above-mentioned self-hardening properties of fly ash, which may be degraded by wet conditions and the need to obtain a certain level of strength within a short period of time, fly ash is commonly used as a hardening aid for artificial ground. Portland cement was added within a few percent. Also,
As water for mixing fly ash, volcanic ash, and cement, filtered seawater collected from Tokyo Bay was used. A slurry-like artificial ground material was prepared by kneading each of the above materials in a 3 g Hobart mixer for 5 minutes. The rotation speed of the Hobart type mixer is 60 rpm for planetary motion and 60 rpm for rotary motion.
It is 140rpm. The fluidity, specific gravity, and material separation of the slurry-like artificial ground material thus obtained were investigated. The fluidity of the artificial ground material is similar to that of a normal concrete slump cone,
Measurements were made using a special slump cone for mortar and plaster with a height of 15 cm. In addition, the specific gravity of the artificial ground material was measured using a mud balance used for measuring the density of drilling mud. Furthermore, material separation of the artificial ground material was measured using a 100ml graduated cylinder. Next, after measuring each characteristic of these artificial ground materials, this artificial ground material was filled into a vinyl chloride mold with a diameter of 5 cm and a height of 10 cm, the top surface was closed with polyethylene film, and the mold was heated at 20°C. The specimens were cured in seawater at a temperature maintained at . The strength characteristics of the artificial ground material thus hardened were then measured. The strength characteristics were mainly measured using a uniaxial compression test (strain rate 0.8%/min). In the following experimental results, terms indicating the composition of fly ash, volcanic ash, and cement are defined as follows. ●Volcanic ash content (As): weight ratio of dry volcanic ash to the total dry weight of fly ash and volcanic ash ●Cement addition rate (Ac): weight ratio of cement to the total dry weight of fly ash and volcanic ash ●Water content ratio (Wp): dry Weight ratio of total moisture to total dry weight of fly ash, dry volcanic ash, and cement Figure 1 shows the amount of cement added as a hardening agent when volcanic ash is not mixed in the artificial ground material (As = 0%). It is a figure showing the relationship between and the compressive strength of artificial ground. Other conditions are shown in the figure. The flyash used in this experiment contains approximately 6% calcium as shown in the table above, and therefore has a compressive strength of several kgf/ ^cm2 if it is discharged and stored in a dry state. It is assumed that this is expressed. Therefore, if this flyash is stored in a dry state, it is considered unnecessary to add cement as a hardening aid. However, since this fly ash was left in a wet state for one month after being discharged, it is thought that the self-curing properties that it should originally have had deteriorated. However, even with such fly ash, strength can be expected to increase by adding a small amount of cement. FIG. 2 is a diagram showing the relationship between the amount of volcanic ash added and the compressive strength of artificial ground. Other conditions are shown in the figure. Although volcanic ash alone cannot provide sufficient compressive strength, it can be understood that if it is used in combination with fly ash, sufficient strength can be achieved as a material for artificial ground. In this case, within the range of volcanic ash content of 37% to 63%, no significant difference is observed in the strength development of the artificial ground. FIG. 3 is a diagram showing the relationship between the wet density of the artificial ground after hardening and the volcanic ash content. As seen in the figure, it can be seen that the specific gravity of the artificial ground formed can be adjusted by appropriately adjusting the amount of volcanic ash mixed. This result is due to the fact that the specific gravity of volcanic ash is greater than that of fly ash, but it is also thought to be due to the fact that material separation and shrinkage become greater with the addition of volcanic ash. That is, FIG. 4 is a diagram showing the relationship between the breathing rate and shrinkage rate of artificial ground and the volcanic ash content,
As shown in Figure 4, as the volcanic ash content increases, the breathing rate and shrinkage rate also increase, that is, the material separation of the slurry-like artificial ground material increases, and when the volcanic ash content is around 60-75%, It is reaching its peak. This result is because the particle size of volcanic ash is larger than that of fly ash, so fly ash fills the gaps between volcanic ash without any gaps, which increases the apparent specific gravity of the mixture due to the so-called particle size adjustment effect. However, this can be interpreted to be due to the generation of free water. FIG. 5 is a diagram showing the relationship between the wet density of the artificial ground after hardening and the water content ratio. As in Figure 3, it can be seen that the specific gravity of the artificial ground can be adjusted by increasing or decreasing the volcanic ash content. Similarly,
It is also possible to adjust the specific gravity of the artificial ground to some extent by increasing or decreasing the blended water content. FIG. 6 is a diagram showing the relationship between the slump value, which indicates the fluidity of slurry-like artificial ground material, and the blended water content ratio. Although it depends on the amount of volcanic ash mixed, the fluidity of the artificial ground material also improves as the water content increases. Similarly, FIG. 7 is a diagram showing the relationship between the slump value and volcanic ash content of artificial ground materials. A similar trend to the results shown in FIG. 4 is shown. Based on the experimental results shown above, we will discuss the blending ratio of each mixture suitable as an artificial ground material. Considering the versatility of artificial ground materials, the required performance values are as follows. Unconfined compressive strength: 3Kgf/ ^cm2 at age 28 days Wet density: 1.7g/ ^cm3 or less Breathing rate: 3% or less Fluidity: Slump value 12cm or less The compounding ratio that satisfies these performances is shown in Table 2 below. As shown.

[Table] "Effects of the Invention" As explained in detail above, the artificial ground material made of fly ash of the present invention can provide the following excellent effects. a. Use fly ash, which has pozzolanic activity and has the property of hardening itself by reacting with water, as the main component of artificial ground materials such as backfilling materials, fillers, and reclamation materials to be put into landfills, seawalls, etc. As a result, the artificial ground material will harden on its own after being placed at the planned reclamation site such as the seabed, and will have sufficient strength as an artificial ground.
There is no need to consider subsidence or liquefaction of the artificial ground itself, and there is no need for a strong outer wall, making construction easier. Furthermore, since the specific gravity of the hardened artificial ground is lighter than the specific gravity of reclaimed sand, which is the conventional artificial ground material, there is no fear of subsidence or landslide destruction of the original ground, and there is no need for ground improvement work on the original ground. b By using volcanic ash with porazon activity in addition to fly ash as a component of the artificial ground material, and adjusting the amount of volcanic ash that has a heavier specific gravity and larger particle size than fly ash, the difference in specific gravity between fly ash and volcanic ash and the difference between fly ash and volcanic ash can be reduced. Due to the particle size adjustment effect due to the difference in particle size from volcanic ash, the specific gravity of the artificial ground that becomes the artificial ground material can be adjusted, and the inconvenience caused by the artificial ground being too light or too heavy can be avoided. I can do it. In addition, by adding volcanic ash to fly ash, we can prevent the formation of so-called "clumps", and by increasing the amount of artificial ground material with volcanic ash, it is possible to prevent the formation of so-called "clumps" when using only fly ash, which has restrictions on production area and production volume. In comparison, the economic efficiency of artificial ground materials can be improved. That is, by configuring the artificial ground material mainly from fly ash and volcanic ash, it is possible to form an artificial ground that has sufficient strength as a ground and has an optimal specific gravity as a ground.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the amount of cement added and the compressive strength of the artificial ground, Figure 2 shows the relationship between the amount of volcanic ash added and the compressive strength of the artificial ground, and Figure 3 shows the relationship between the amount of cement added and the compressive strength of the artificial ground. Figure 4 is a diagram showing the relationship between the wet density of the ground and the volcanic ash content; Figure 4 is a diagram showing the relationship between the breathing rate and shrinkage rate of the artificial ground and the volcanic ash content;
Figure 5 is a diagram showing the relationship between the wet density of the artificial ground after hardening and the mixed water content ratio, Figure 6 is a diagram showing the relationship between the slump value of the artificial ground material and the mixed water content ratio, and Figure 7 is a diagram showing the relationship between the artificial ground material's wet density and the mixed water content ratio. FIG. 3 is a diagram showing the relationship between the slump value of a material and the volcanic ash content.

Claims (1)

[Scope of Claims] 1. A backfilling material, filler material, and landfill construction material that is made of flyash as a main component and mixed with volcanic ash and water, and that is used in reclaimed lands such as artificial islands, seawalls, etc. An artificial ground material such as, etc., in which the dry weight ratio of volcanic ash to the total dry weight of fly ash and volcanic ash is within the range of 30 to 60%, and the weight ratio of water to the total dry weight is 40 to 60%. %. 2. An artificial ground material made of flyash according to claim 1, characterized in that a hardening aid is added. 3. An artificial ground material made of fly ash according to claim 1 or 2, characterized in that a surfactant is added thereto.