JPH0811792B2 - Polymer for muddy water method-muddy water - Google Patents

Description

The present invention relates to a polymer muddy water used in muddy water construction methods such as a deep underground continuous wall construction method, a muddy water shield construction method, and a cast-in-place pile construction method.

[Conventional technology]

Conventionally, in the deep underground continuous wall construction method, muddy water shield construction method, cast-in-place pile construction method, etc. The mud method to prevent is used. The liquid having a large specific gravity and a high viscosity used in this muddy water method is generally called a ground stabilizing liquid or muddy water, and has a function of holding and transporting the excavated soil as well as the stability of the excavated wall surface. As such mud water, bentonite mud water containing swelling clay bentonite as a main material, polymer mud water containing a water-soluble polymer as a main material, and the like are widely used.

Here, the bentonite muddy water is prepared by suspending bentonite of about 250 mesh in water at a concentration of about 4 to 10% by weight,
Furthermore, thickeners such as carboxymethyl cellulose (CMC) to improve viscosity and wall-forming properties, and dispersants such as sodium polyphosphate, sodium lignin sulfonate, and sodium humate to prevent deterioration due to cement components or salt. It is a mud made by adding such as.

In addition, polymer muddy water has a degree of polymerization of 600 to 1500 C in water.
Dissolve MC about 0.5%, preservative 0.03 to 0.05% by weight, dispersant 0.1% by weight, bentonite 1
Approximately 2% by weight is mixed to produce mud, which has excellent cement resistance and seawater resistance.

[Problems to be solved by the invention]

By the way, in the bentonite muddy water, the influence of cement in the cement at the time of placing concrete or the cement in the soil cement construction method, further deteriorates due to the influence of seawater, etc., thereby increasing the specific gravity and viscosity, and the mud film forming property. There is a risk that the excavation wall surface may collapse due to deterioration and aggregation of bentonite.

Further, in the above-mentioned polymer mud, there is a problem that CMC rots to cause molecular cleavage, which causes a decrease in viscosity over time and makes it unsuitable for use, and further bentonite added as a weighting agent to this polymer mud As in the case of the bentonite muddy water described above, it deteriorates and causes coagulation separation, which may reduce the specific gravity of the polymer muddy water and cause collapse of the excavated wall surface.

[Means for solving problems]

Therefore, in the present invention, the above problem is solved by blending CMC having a degree of polymerization of less than 100 in water to a weight concentration of 0.8% or less, and adding on-site collected earth and sand to adjust the polymer mud water.

Here, CMC has the property of increasing the viscosity of an aqueous solution in which it is dissolved as the degree of polymerization increases, so in CMC with a high degree of polymerization, polymerization occurs when it decomposes and causes molecular cleavage. And the viscosity of the aqueous solution is reduced accordingly. And, such a decrease in viscosity due to decay is large when the degree of polymerization exceeds 100, and is extremely small when the degree of polymerization is 100 or less. Therefore, the CMC used in the polymer mud of the present invention has a degree of polymerization of less than 100 and preferably 80 or less.

Further, in the above-mentioned polymer mud, when the concentration of the CMC aqueous solution used for the mud production exceeds 0.8%, its viscosity becomes too high and it becomes unsuitable for the construction polymer mud. Therefore, the CMC aqueous solution used for this polymer mud water has a concentration of 0.8% by weight, preferably 0.2 to 0.6% by weight.

Further, in this polymer muddy water, it is possible to sufficiently adjust the specific gravity by mixing earth and sand during excavation without adding bentonite or other weighting agents to increase the specific gravity. Even kaolinite, which has a low swelling property and has settled as slime in muddy water and has hindered construction, can be sufficiently suspended in the polymer muddy water.

With such polymer mud, there is almost no decrease in viscosity due to the decay of CMC, and therefore it is easy to readjust the polymer mud, so that the construction can proceed smoothly. Further, unlike the conventional polymer mud water, since no preservative is added, the chemical oxygen demand of the waste mud water is low, and therefore the disposal processing is easy, so that the disposal processing cost can be reduced. Further, since it does not contain bentonite, it has excellent cement resistance and seawater resistance. Furthermore, since no preservative and dispersant are added, the cost can be reduced to about half that of conventional polymer mud.

〔Example〕

Hereinafter, the present invention will be described more specifically by way of examples.

The polymer mud produced in this experiment was prepared by adding 0.6% by weight of CMC having an average degree of polymerization of 80 to fresh water, then adding 27% by weight of earth and sand collected at the excavation site, and then stirring and mixing with a mixer. .

The initial properties of the polymer mud water thus produced are shown in the table below.

In addition, this polymer mud and CMC with an average degree of polymerization of about 100
Figure 1 shows the change over time in the funnel viscosity when 1% by weight of spoiled mud was added to each of the polymer mud shown in the conventional example with 0.5% by weight of bentonite and 2% by weight of bentonite and left at 30 ° C and 80% RH. It was shown to.

As is clear from this figure, in the conventional polymer mud, the decrease in viscosity due to decay is remarkable, whereas in the polymer mud in this experimental example, the decrease in viscosity is very small.

〔The invention's effect〕

As described above, the polymer mud of the present invention is
CMC with a degree of polymerization of less than 100 was used in an aqueous solution containing 0.8% by weight or less, and the mud was made without adding bentonite. Since adjustments are easy, construction work can proceed smoothly. In addition, since no preservative is added, its disposal is easy,
Therefore, the disposal cost can be reduced.
Furthermore, since it is not always necessary to add a preservative, a dispersant, a weighting agent, etc., the cost of the polymer mud itself can be reduced.

[Brief description of drawings]

The drawing is a graph showing changes over time in funnel viscosity of the polymer mud of the present invention and the conventional polymer mud.

Claims (1)

[Claims] 1. A polymer muddy water for a muddy water construction method, which is characterized in that an aqueous solution prepared by mixing carboxymethylcellulose having a degree of polymerization of less than 100 at a weight concentration of 0.8% or less is prepared without adding bentonite.