JPH0352514B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preparing a stabilizing liquid used for excavating the ground in a stabilizing liquid construction method for foundation construction in the civil engineering and architectural fields. In foundation work and underground work in construction work, methods that use stabilizing fluids, such as the underground continuous wall method and the muddy water pressurized shield method, are widely used due to problems such as noise and vibration. Stabilizing liquids used in such construction include clay such as bentonite, water-soluble polymers such as sodium carboxymethyl cellulose (hereinafter abbreviated as CMC), and acid splitting agents such as complex phosphates and humates. The most common is one suspended in water. The primary purpose of the stabilizing liquid is to form an impermeable mud wall on the surface of the mine wall to prevent the wall from collapsing. However, depending on the construction method, the stabilizing liquid is circulated and The viscosity of the stabilizing liquid is increased in order to have the ability to transport the excavated debris out of the mine without settling it. However, in recent years, the underground continuous wall construction method using stabilizing liquid has become larger, and the normal excavation width is 0.4 to 0.5 m.
Some are now appearing with depths of 30 to 40 meters, widths of 1.0 to 1.2 meters, and depths of up to 100 meters. In such deep excavation, excavated soil particles (hereinafter referred to as slime) suspended in the stabilizing liquid
As the settling distance becomes longer, the amount of slime in the stable liquid increases, which increases the amount of slime deposited at the bottom of the mine. If a reinforcing bar cage is built and concrete is poured with slime deposited at the bottom of the mine, the slime is difficult to replace with concrete and remains at the tip of the wall, reducing the supporting capacity of the underground wall and This may cause subsidence. Furthermore, if slime is mixed into concrete, it causes problems such as a decrease in the strength of the concrete, so there is a need for a stabilizing solution from which the slime can be easily separated from the stabilizing solution. Furthermore, in deep excavation, the mud pressure increases, making it easy for the stabilizing fluid to flow into the gaps in the ground or into the permeable layer, which is called mud slippage.Therefore, there is a need for a stabilizing fluid that creates strong mud walls with a small amount of excess water. It is. Usually, the composition of the stabilizer is 100 parts by weight of fresh water, 2 to 8 parts by weight of bentonite, 0.05 to 0.3 parts by weight of CMC, and 0.05 to 0.3 parts by weight of a dispersant such as hexane metaphosphate or sodium humate. Yes, but
Conventionally, the CMC used here has a relatively high viscosity, so the viscosity of the stabilizing liquid becomes high, which is not a desirable direction for slime removal. The present inventors investigated in detail the relationship between the thickening effect of CMC on a stable liquid and the effect of reducing excess water, and found that CMC with a degree of etherification of 1.3 mol/C ₆ or more
It was discovered that by adding a composition in which the stabilizer and sodium glycolate were combined in a specific ratio range, the effect of reducing the amount of excess water was large, although the thickening effect of the stabilizer was small, and the separation of slime was improved. We have completed a method for preparing a stable liquid that has good water retention and a small amount of excess water. The reason why the degree of etherification of CMC in the present invention is defined as 1.3 mol/C ₆ or more is that the degree of etherification of general CMC used in the stabilizing solution is 0.6 to 1.0 mol/C ₆
and in this range of etherification degree,
This is because the thickening effect of CMC is strong, and the effect of using sodium glycolate in combination is not apparent. In addition, in recent years, CMC with a degree of etherification of 1.1 to 2.5 mol/C ₆ has been used in cases where the stabilizer solution is easily putrefied in the summer;
The range of the degree of etherification is limited from the viewpoint of bacterial resistance, and the degree of etherification of the present invention is
This is based on a completely different technical idea from the basis for limiting it to 1.3 mol/C ₆ or more (Japanese Patent Publication No. 57-25585).
issue). That is, the inventors found that the viscosity of CMC is almost the same,
When stabilizing liquids were prepared using various CMCs with different degrees of etherification, it was found that the viscosity of the stable liquids was lower when CMC with a higher degree of etherification was used. This is because the higher the degree of etherification of CMC, the more the dispersion effect is superior to the thickening effect of the stabilizer, and when the degree of etherification is 1.3 mol/C ₆ or more,
It became clear that the relationship was becoming stronger. The reason why CMC with a degree of etherification of 1.3 mol/C ₆ or higher is used in the present invention is as described above, but since this CMC has a strong dispersing action, it has little thickening effect on the stabilizing liquid, and moreover, CMC is 95 to 70% (preferably 90-80%) and 5% by weight of sodium glycolate
It has been found that by adding a composition containing more than 30% by weight (preferably 10 to 20%), the viscosity of the stabilizer can be kept low and the amount of excess water can be kept low. The present invention, which requires this, has succeeded in obtaining a stable liquid with a low viscosity and a small amount of excess water by using CMC in combination with a specific proportion of sodium glycolate, with the amount of bentonite and stabilizer that have been conventionally used. be. Hereinafter, the effects of the present invention will be further explained with reference to Examples. Example 1 100 parts of fresh water (hereinafter all parts by weight) and 5 parts of bentonite from Gunma Prefecture and 1% solution shown in Table 1 have approximately the same viscosity (approximately 300 cps) but different degrees of etherification.
Add 0.3 parts of CMC or a composition consisting of 80% CMC and 20% sodium glycolate and add 600 r.
After stirring with a pm stirrer for 20 minutes, it was left overnight. The next day, after stirring again at 600 r.pm for 20 minutes, the resulting stable solution was adjusted to 25°C, and the API (American Petroleum Institute)
Funnel viscosity (sec) of 500 ml/500 ml was measured using a standard Funnel viscometer. In addition, for the amount of excess water, using the same API standard pressure overtesting device, 350ml of stable liquid at 25℃ was
The amount of liquid (ml) passed through pressurization at Kg/cm ² for 30 minutes was measured. The results are shown in Table 1.

[Table] As seen in Table 1, CMC with similar viscosity
It can be seen that the higher the degree of etherification, the lower the viscosity of the resulting stabilized liquid, despite the addition of .
In the system consisting of CMC and sodium glycolate, funnel viscosity and excess water amount become low when the degree of etherification exceeds 1.3 mol/C ₆ , and the effects of the present invention are clear. Example 2 100 parts of fresh water, 5 parts of bentonite from Gunma Prefecture, 1% solution viscosity 305 cps and etherification degree 1.35 mol/C ₆ CMC 0.3 to 0.15 parts used in Comparative Example 4 in Table 1, and CMC 95 to 50% and sodium glycolate 5~
A stabilizing solution was prepared in the same manner as in Example 1, except that 0.3 part of a composition consisting of 50% was added. Furthermore, in Inventive Examples 7 and 8, the degree of etherification was
Unpurified CMC of 1.34 mol/C ₆ and 1.51 mol/C ₆ was experimentally produced, and 0.3 part was added to prepare a stable solution using the method described above. Furthermore, the degree of etherification of sodium glycolate in unpurified CMC was determined to be 1.34 mol/C ₆ .
Those with 1.51 mol/C ₆ were 13.7% and 15.3%, respectively. Table 2 shows the results of testing the properties of these stabilizers.

【table】

[Table] As shown in Table 2, when sodium glycolate is added to CMC with a degree of etherification of 1.35 mol/ _C6 , the funnel viscosity decreases due to the decrease in CMC content, but the amount of excess water A low effect is observed up to 30% sodium, but no further increase in effect is observed. This fact is
This is thought to be due to a decrease in the CMC portion. It is not clear why the amount of excess water is reduced by the combined use of sodium glycolate and CMC with a degree of etherification of 1.3 mol/C ₆ or higher, but the chelating effect of sodium glycolate can reduce polyvalent metal ions in bentonite minerals. It is presumed that this is because the anionic properties of CMC with a high degree of etherification are fully exhibited by blocking, and the dispersibility and protective colloidal properties of CMC are further strengthened. Example 3 At a site where cast-in-place piles are constructed using the earth drill method, 5 parts of bentonite from Yamagata Prefecture and 0.1 part of sodium humate were added to 100 parts of fresh water, with a normal 1% solution viscosity of 350 cps and degree of etherification of 0.60 mol. 1% solution viscosity 280 cps, degree of etherification 1.36 mol/C ₆ using the method of the present invention instead of 0.2 parts _of normal CMC .18 parts and sodium glycolate
After excavation was carried out using a stabilizing solution to which a composition of 0.02 parts of amount of water,
Specific gravity and sand content were measured. Specific gravity and sand content were also measured using an API standard mud balance and sand content meter, respectively. The results are shown in Table 3.

【table】

[Table] Because this stratum was mainly composed of silt and fine sand layers, the stabilizing liquid contained a large amount of slime.
As shown in Table 3, when ordinary CMC was used, the specific gravity was high, the stabilizer contained a large amount of sand, and the amount of excess water was large, so the stabilizer could not be said to be in good condition. On the other hand, when the method of the present invention is used, both the specific gravity and the sand content are reduced, and the amount of excess water is also reduced, which clearly indicates that slime separation is improved.

Claims (1)

[Claims] 1. A stabilizing construction method for construction work, characterized in that a composition consisting of 93 to 70% by weight of sodium carboxymethyl cellulose and 7 to 30% by weight of sodium glycolate with a degree of etherification of 1.3 mol/C ₆ or more is added. A method for preparing stabilized liquid for construction work.