JPS621670B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to muddy water used in muddy water construction methods such as underground wall construction method and muddy water shield construction method. Bentonite mud, which is mainly composed of bentonite, has been known as mud water used in underground wall construction methods and the like. This bentonite mud water is made by dispersing 6 to 8% bentonite (weight ratio, the same below) in tap water, and has excellent wall-building properties.
We have many achievements. However, this bentonite slurry has ion exchange ability or base substitution ability, which is one of the characteristics of bentonite.
It has the disadvantage that it deteriorates due to the influence of various ions (especially ions from metal salts, etc.) leached from soil, groundwater, seawater, cement, etc. In particular, the contamination of seawater and cement significantly reduces the stability of bentonite mud. For this reason, as a measure to prevent stability deterioration due to contamination with seawater or cement, thickeners such as carboxymethyl cellulose (CMC) and dispersants such as lignin sulfonic acid compounds and polyphosphates are added at approximately 0.05 to 0.3% each. Sometimes. Thickeners have the effect of maintaining the viscosity of muddy water and reducing the amount of water dewatered, while dispersants prevent deterioration due to salt contamination, settle mixed soil, and reduce the specific gravity of muddy water.
It has the effect of preventing an increase in viscosity. However, the effects of these thickeners and dispersants are not sufficient, with salt water (NaCl) at 0.5-0.7% and cement components at 0.5-0.
If it is mixed in at a concentration of 1% or more, it becomes unusable. However, at construction sites, seawater often mixes in at 1% or more, and when concrete is poured, up to 5 to 7% of cement components may mix in. Adding the above-mentioned thickeners and dispersants is not effective as a countermeasure against deterioration. It was insufficient. For this reason, polymer slurry based on CMC, which does not deteriorate even when mixed with seawater or cement components, is being used. However, this polymer muddy water has the disadvantage that the CMC rots and deteriorates during the summer and loses its functionality. In addition, when applying the rotary excavation method using an excavation pit to the excavation method,
CMC is separated together with mixed soil and CMC
must be constantly replenished, making it uneconomical in terms of cost.Therefore, polymer slurry is also by no means satisfactory as slurry for muddy construction methods. Furthermore, bentonite mud must be manufactured using high-quality clean water that does not contain Cl ions or Ca ions, but it is becoming increasingly impossible to obtain such high-quality clean water at construction sites. . This invention was made in view of the above circumstances, and it does not gel even when seawater components or cement components are mixed in at high concentrations, has stability, sufficiently maintains its functions, and provides high-quality fresh water. The object of the present invention is to provide mud water for mud construction methods that can be produced using low-quality water such as river water, sea water, and ground water without the need for mud water. The muddy water of the present invention is characterized by containing at least bentonite and a polyacrylate having a complexing power for Ca ions of 300 mg/g or more. The bentonite used in this invention is
Examples include particles having a particle size of about 200 to 350 mesh, which have been conventionally used for bentonite mud, but are not particularly limited. The mixing amount of bentonite is 4 to 8% by weight of the muddy water, and usually about 6% is preferable. In addition, examples of acrylates with complexing power for Ca ions of 300 mg/g or more include sodium salts, potassium salts, ammonium salts of polyacrylic acid, monoethanolamine, diethanolamine, triethanolamine, pyridine, piperidine, morpholine, etc. It is an amine salt and has a complexing power for Ca ions of 300 mg/g or more. The complexing power for Ca ions was determined by titration of an aqueous calcium acetate solution.
A polyacrylate having a complexing power of less than 300 mg/g is ineffective in preventing gelation caused by seawater components and cement components and maintaining stability. (1st
(See Figure 10 - Graph showing the relationship between Gel and the amount of cement mixed in) The amount of polyacrylate added is 0.2 to 2% by weight, preferably 0.4 to 0.6% by weight of the muddy water.
%. (See Figure 2) If it is less than 0.2%, the above-mentioned stabilizing effect cannot be obtained sufficiently, and if it exceeds 2%, the viscosity of the muddy water becomes too high, making it impossible to knead and causing agglomeration, which is disadvantageous. . Furthermore, the water used for the muddy water of the present invention is not limited to high-quality water such as tap water, but also low-quality water that is easy to procure at low cost, such as groundwater, river water, and industrial water that contain various ions. be able to. This has a complexing power of 300 for the above Ca ions.
This is because by using a polyacrylate of mg/g or more, various ions contained in water are complexed and their reaction with bentonite is inhibited. The muddy water of this invention sufficiently exhibits its function with bentonite and the above-mentioned specific polyacrylate, but if necessary, it may be added with a known thickener such as CMC, humate, ligurin sulfonic acid compound, etc. A dispersant such as hexametaphosphate or tripolyphosphate may be added. The amount of the thickener added is 0.05 to 0.3 wt% with respect to the muddy water, and the amount of the dispersant added is also 0.05 to 0.3 wt%. Hereinafter, a specific explanation will be given by showing examples. Example 1 Bentonite 6wt%, CMC 0.1wt as thickener
A portland cement dispersion and an aqueous sodium chloride solution were added to the muddy water of the present invention consisting of 0.4wt% of sodium polyacrylate having a complexing power for Ca ions of 340mg/g, and changes in the properties of the muddy water were investigated. The amounts of cement dispersion and sodium chloride aqueous solution added to mud water were kept constant at 5 wt%, and the concentrations of the dispersion and aqueous solution were varied to determine changes in mud water properties corresponding to changes in the concentrations of cement and sodium chloride. In addition, in place of the above sodium polyacrylate, a lignin sulfonic acid compound and a complexing power of 260
mg/g sodium polyacrylate at 0.4wt%
A similar study was conducted for the comparative example in which the compound was added. The properties of the muddy water were determined by PH measurement (using a glass electrode), the amount of water removed by the API standard pressurization test, the gel strength (10-Gel) by a VG meter, and the Funnel viscosity FV using a Funnel viscometer. The results are shown in Figure 1. Figure 1 shows, from top to bottom, changes in PH, dewatering amount, gelation amount, and viscosity of mud water when cement or NaCl is mixed. The lower the dehydration amount, gelling amount, and viscosity of mud water, the more effective it is. As is clear from the relationship between 10-Gel and the amount of cement mixed in Figure 1, the complexing power is 300mg/
Mud water containing more than g of sodium polyacrylate does not gel even when the amount of cement mixed in is 5 wt%, and maintains its function as mud water. From this result, it was confirmed that the muddy water of the present invention has excellent stability. Example 2 Bentonite 6wt%, CMC 0.1wt as thickener
%, producing muddy water containing 0 to 0.6 wt% of sodium polyacrylate with a complexing power for Ca ions of 340 mg/g,
The gel strength (10-Gel) and funnel viscosity (FV) of these muddy waters were measured in the same manner as in Example 1, and the influence of the concentration of the sodium polyacrylate was investigated. The results are shown in FIG. Figure 2
As is clear from the relationship between FV. and the amount of cement mixed in, if 0.2% or more of sodium polyacrylate with a complexing power of 300 mg/g or more is mixed, an increase in viscosity due to cement mixed in can be reliably prevented. Also, 10−Gel
As is clear from the relationship between the amount of cement mixed in and the amount of cement mixed in, when sodium polyacrylate is blended in an amount of 0.4% or more, an increase in 10-Gel due to cement mixed in is reliably prevented. From the results, when the concentration of sodium polyacrylate having the above-mentioned specific complexing power is 0.2wt% or more, gelation prevention effect starts to appear, and 0.4wt% or more.
It was found that a sufficient effect can be obtained at ~0.6wt%. Example 3 Various waters for producing muddy water were prepared, muddy water of the present invention was prepared using these waters, and its properties and stability were investigated. At the same time, we also studied a method of creating concentrated mud with twice the concentration of normal mud and then diluting this concentrated mud. The results are shown in Table 1. As is clear from the results in Table 1, the present invention
By using polyacrylate with a complexing power for Ca ions of 300 mg/g or more, stable muddy water that does not gel even when using water containing high concentrations of Na and Ca ions, such as cement extraction water and artificial seawater, can be created. can be created. The ability to use cement extracted water has a great practical effect. In other words, in actual construction, when concrete is poured, muddy water inevitably comes into contact with the concrete.
In conventional muddy water, 10m from the concrete pouring surface.

【table】

【table】

[Table] Previously, the muddy water within the range of 100 to 100 ml was disposed of, but the muddy water of this invention does not need to be disposed of, and the muddy water that was conventionally disposed of can be recovered and used. Furthermore, it can be seen that even if highly concentrated concentrated mud is once created and then diluted with water separated from drilling mud, mud with good properties can be obtained. This also makes it possible to effectively utilize the separated drilling mud water generated at the site, reduce the amount of tap water that is expensive and difficult to obtain, and significantly reduce construction costs. As explained above, the muddy water for the muddy construction method of the present invention contains at least bentonite and polyacrylate having a complexing power for Ca ions of 300 mg/g or more. Even when the ingredients are mixed in at high concentrations (NaCl content: 3%, cement content: 5-7%), it does not gel and maintains stability. Therefore, in the past, muddy water that had to be discarded as a result of being mixed with cement components during concrete placement can be effectively reused, disposal costs can be reduced, and processing equipment can be downsized. In addition, low-cost and easily procured groundwater, river water, separated water from drilling mud, etc. can be used as manufacturing water. Furthermore, it can be installed in areas with high salt content, such as coastal landfills, without any problems.
Furthermore, unlike polymer slurry made mainly of CMC, it does not rot and is not subject to the limitations of excavating machinery. In addition, it is possible to create concentrated mud water and dilute it using separated drilling mud water generated on-site, which allows for effective use of separated water and the use of high-quality water such as expensive tap water. You can save money. Furthermore, when using the muddy water construction method in remote areas where it is difficult to obtain good quality water, there is no need to bring good quality water to the construction site, and from this point of view as well, construction costs can be reduced. Furthermore, since there is no gelation of muddy water, it has extremely great practical effects, such as preventing deterioration in the quality of poured concrete due to gelation of muddy water.

[Brief explanation of the drawing]

FIG. 1 is a graph showing, from top to bottom, changes in PH, amount of dehydration, amount of gelling, and funnel viscosity in the muddy water of the present invention when mixed with cement or salt;
The figure is a graph showing how the relationship between the amount of cement or salt mixed in, the amount of gelation, and the funnel viscosity changes when the amount of polyacrylate with a complexing power of 300 mg/g or more is changed.

Claims (1)

[Claims] 1. Comprised of at least bentonite and polyacrylate, the polyacrylate has a complexing power for Ca ions of 300 mg/g or more, and the blending amount is 0.2 to 2% by weight. Mud water for mud water construction method is characterized by certain characteristics.