JP7025614B2 - Method of reforming mixed soil with bubbles - Google Patents

Description

The present invention relates to a method for modifying a bubble-mixed soil.

Conventionally, mud that is generated in construction work such as shield work and propulsion work, that is, soft earth and sand with a high water content, is dehydrated as industrial waste and then landfilled in a final disposal site for disposal. .. The treatment of such mud is extremely uneconomical because the dehydration treatment is expensive and the dehydrated mud must be disposed of without being reused as industrial waste. Moreover, even if the mud is treated and disposed of in this way, the difficulty in locating the final disposal site for industrial waste has become more serious recently.

Against this background, there is an increasing need to recycle mud generated during construction work. In response to these demands, the contractor himself mixed a modifier and reformed the mud, which had not been used until now, at the site where the mud was generated. Technology that creates utility value by reforming the soil, transports it directly from the reforming treatment site to the reuse destination, and reuses it for various purposes such as roadbed materials, backfill soil, residential land development soil, and embankment of embankments. Is under development (see, for example, Patent Document 1).

By the way, an anionic polymer flocculant can be mentioned as a typical modifier used for the reforming treatment of mud, but it is a drilling additive used in shielding work, propulsion work, etc. For excavated soil containing a large amount of (foaming material or bentonite) to which an anionic thickener such as molecular mud material or carboxymethyl cellulose (CMC) is added, sufficient modification can be achieved with the anionic polymer flocculant alone. In some cases, it was not possible to reform the soil into self-sustaining earth and sand that could be transported.
Further, the earth and sand modified by using an anionic polymer flocculant on the earth and sand in which only an anionic surfactant is used as a foaming agent in the excavation additive is an anionic interface constituting the foaming agent by rainfall or the like. In some cases, the activator was eluted and foaming became a problem.

In addition, the earth and sand modified only by the anionic polymer flocculant may cause foaming filter water to flow into rivers and groundwater due to the elution of the surfactant that constitutes the foaming agent due to rainfall, etc., and the landfill site at sea. There was a risk of causing secondary problems such as foaming in the water and a decrease in yield due to the generation of foam during intermediate treatment such as classification treatment of soil waste in the intermediate treatment plant.

In such a case, it is known that the modification can be performed by using a cationic polymer flocculant having a high cationic value instead of the anionic polymer flocculant (see, for example, Patent Document 2). ) However, the cationic polymer flocculant having a high cationic value and a large molecular weight is highly toxic to fish, and it is regarded as a problem that the cationic polymer flocculant elutes when the reformed earth and sand are reused. rice field.

Japanese Unexamined Patent Publication No. 2006-2658585 Japanese Unexamined Patent Publication No. 3-100295

INDUSTRIAL APPLICABILITY The present invention has a problem associated with a method for modifying a fluid-like sediment such as mud, which is difficult to reform into a self-sustaining sediment by adding the above-mentioned anionic polymer flocculant alone, particularly a bubble-mixed sediment. In view of this point, the anion constituting the foaming agent is used to modify the foam-mixed earth and sand containing an anionic thickener, bentonite, etc. into the earth and sand having self-sustaining property by adding the polymer flocculant alone. It is an object of the present invention to provide a method for modifying a bubble-mixed earth and sand that can solve the secondary problem associated with the elution of a sex surfactant and the problem of fish toxicity due to the use of a cationic polymer flocculant.

In order to achieve the above object, the method for modifying the bubble-mixed soil of the present invention is the method for modifying the bubble-mixed soil, in which an amphoteric polymer flocculant is added to the bubble-mixed soil and stirred, and water is added to the ion complex. It is characterized by reforming a bubble-mixed earth and sand into a self-sustaining earth and sand by generating an insoluble substance.

In this case, as the amphoteric polymer flocculant, an amphoteric polymer flocculant having a polymerization ratio in which the number of cation moles is lower than the number of anion moles in the neutral range of pH 6 to 8 can be used.

Further, the bubble-mixed earth and sand may be one containing an anionic surfactant, or one containing an anionic thickener and / or bentonite.

According to the method for modifying the bubble-mixed sediment of the present invention, an amphoteric polymer flocculant is added to the foam-mixed sediment and stirred to generate a water-insoluble substance by an ion complex, whereby an anionic surfactant or anionic surfactant or anionic. Bubble-mixed sediment containing thickeners, bentonite, etc. can be reformed into self-sustaining sediment, and at the same time, water insolubilization by an ion complex suppresses elution of cation components, causing problems of fish toxicity and problems. It is possible to solve the secondary problem associated with the elution of the surfactant constituting the foaming agent.

Hereinafter, embodiments of the method for modifying bubble-mixed soil of the present invention will be described based on specific embodiments.

In the method for modifying the bubble-mixed sediment of the present invention, an amphoteric polymer flocculant is added to the foam-mixed sediment and stirred to generate a water-insoluble substance by an ion complex, whereby an anionic surfactant or an anionic thickening agent is produced. A bubble-mixed earth and sand containing agents, bentonite, etc. can be modified into self-sustaining earth and sand, and at the same time, anionic surfactant that suppresses elution of cationic components by water insolubilization and constitutes a foaming agent. It is intended to solve the secondary problem associated with the elution of foam and the problem of fish toxicity due to the use of a cationic polymer flocculant.

Here, "self-sustaining soil" means soil that can be directly transported from the reforming treatment site to the reuse destination using a dump truck, and more specifically. , Means earth and sand with a slump value of 1.0 cm or less as determined by the mini slump test.

By the way, when an amphoteric polymer flocculant is added to the bubble-mixed earth and sand and stirred, both the cation part and the anion part are ionically dissociated in the neutral pH range (pH 6 to 8), and the cation is the anion of the surfactant. It becomes a water-insoluble substance while forming an ionic complex by ionic bonding with an anionic charge such as an electric charge or a thickener and, in some cases, ionic bonding with its own anionic part.
At this time, the anionic surfactant and the anionic thickener constituting the foaming agent in the water-insoluble substance become water-insoluble substances, so that the secondary surfactant associated with the elution of the surfactant constituting the bubbles becomes secondary. The problem can be solved.

In this case, the amphoteric polymer flocculant is not limited to the anionic material or the cationic material to be polymerized, and if the polymerization ratio is such that the number of cation moles is less than the number of anion moles in the neutral range of pH 6 to 8, the cation is more reliably used. It is possible to suppress the elution of components and solve the problem of fish toxicity. More specifically, the amphoteric polymer flocculant has a molecular weight of 5 million to 25 million, an anion portion of 20 mol% to 40 mol%, and a cation portion of 0.1 mol% to 20 mol%. It can be used selectively, and in the comparison between the anion part and the cation part, the cation value is increased or decreased according to the anion value of the excavation additive used (if the anion value of the excavation additive is high, the cation value is increased). If it is low, the cation value can be lowered).

Below, Tables 1 and 2 show the results of comparative tests of the modification treatment of the bubble-mixed soil using the anionic polymer flocculant and the amphoteric polymer flocculant under the following conditions.

Foaming agent (lauryl ether sulfate) containing anionic thickener (carboxymethyl cellulose salt) 1% aqueous solution Dry river sand 15% water (150 ml in 1 L of dry river sand)
Bubble injection 20% (Inject 300 ml of bubbles into 1 L of water river sand)

Foaming agent (lauryl ether sulfate) 1% aqueous solution Dry river sand 15% water (150 ml in 1 L of dry river sand)
Bubble injection 30% (Inject 300 ml of bubbles into 1 L of water river sand)

From the results of the above comparative test, it was confirmed that the amphoteric polymer flocculant exhibits better reformability in the reforming treatment of the bubble-mixed soil as compared with the anionic polymer flocculant.

The method for modifying the bubble-mixed soil of the present invention has been described above based on the embodiment, but the present invention is not limited to the above embodiment, and the configuration thereof is appropriately configured as long as the purpose is not deviated. It can be changed.

In the method for modifying a bubble-mixed earth and sand of the present invention, a cell-mixed earth and sand containing an anionic surfactant, an anionic thickener, bentonite and the like is added alone as a polymer flocculant to have self-sustaining earth and sand. Since it is possible to solve the secondary problem associated with the elution of the anionic surfactant constituting the foaming agent and the problem of fish toxicity due to the use of the cationic polymer flocculant, the anionic polymer can be modified. It can be suitably used for reforming earth and sand having fluidity such as mud soil which is difficult to be modified into self-sustaining earth and sand by adding a flocculant alone, particularly foam-mixed earth and sand.

Claims (3)

In the method for modifying the bubble-mixed sediment, only the amphoteric polymer flocculant having a polymerization ratio of less than the anion mol number in the neutral range of pH 6 to 8 is added and stirred as the polymer flocculant to the bubble-mixed sediment. A method for reforming a bubble-mixed sediment, which comprises generating a water-insoluble substance by an ion complex and reforming the bubble-mixed sediment into a self-sustaining sediment without performing a dehydration treatment. The method for modifying a bubble-mixed soil according to claim 1, wherein the bubble-mixed soil contains an anionic surfactant. The method for modifying a bubble-mixed soil according to claim 1 or 2, wherein the bubble-mixed soil contains an anionic thickener and / or bentonite.