JPS6256913B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a propulsion method. More specifically, the present invention relates to a propulsion method characterized by injecting and mixing a superabsorbent polymer, which becomes a spherical elastic body after absorbing water, into the gap between the ground and the propulsion pipe. BACKGROUND ART Conventionally, in small-diameter pipe installation work such as sewerage work, the propulsion method has been widely used as a construction method that causes relatively little construction pollution. This propulsion method is a construction method in which the propulsion pipes are sequentially pushed forward while propelling the face. Therefore, the propulsion resistance increases in proportion to the propulsion distance. Therefore, the maximum propulsion resistance force is applied to the propulsion tube closest to the main push jack, and the propulsion distance is determined by making this force equal to the load carrying capacity of the propulsion tube. The propulsion resistance force is caused by (1) the frictional force between the ground and the propulsion tube, (2) the adhesive force, a resistance force proportional to the propulsion distance, (3) the resistance force of the cutting edge, and (4) the resistance force due to the meandering of the propulsion tube. , the main ones are resistance due to frictional force and adhesive force. Therefore, injecting an anti-friction material between the ground and the propulsion pipe to reduce the propulsion resistance is very effective in extending the propulsion distance. If the propulsion distance is extended, it will be possible to widen the spacing between vertical shafts, which will greatly help reduce construction pollution, lower construction costs, and shorten the construction period. For this reason, much research has been conducted on anti-friction materials. Conventionally, a viscous suspension containing water and bentonite as the main constituents has been used as an anti-friction material in propulsion methods. However, since this anti-friction material is in the form of a soft gel, even if it is injected between the earth and the propulsion pipe, the earth and sand in the earth will be reduced when the earth and the propulsion pipe move relative to each other during the propulsion work. Easily mixed into abrasive materials,
If the moisture content of the ground is low, such as in a sand layer or gravel layer without groundwater, the anti-friction material will be absorbed into the ground and the anti-friction material's effect will be diminished. Also, when used in a sand layer with a very high moisture content or in a sand layer with a flow of groundwater, the anti-friction material tends to be diluted or even washed away, causing the anti-friction material to lose its effectiveness. It was hot. Also, JP-A-54-79908 and JP-A-55-75483
It has been proposed to use an aqueous suspension prepared by blending an aqueous dispersion of superabsorbent hydrogel with minerals, organic thickeners, surfactants, and oils as an anti-friction material for shield propulsion methods. . However, the superabsorbent hydrogel disclosed therein has an amorphous shape, and when it swells in contact with water, its strength against pressure is low, and it is still difficult to use the above-mentioned water and bentonite as main constituents. It has the same drawbacks as friction materials and is not satisfactory as a friction reducing material. As a result of various studies on these problems, the inventors of this invention found that a specific type of super-absorbent polymer that becomes a spherical elastic body when water is absorbed is used as a component of the anti-friction material. He discovered that it had a remarkable effect when doing so, and completed this invention. This invention was made in light of the above circumstances, and its purpose is to provide a new propulsion method that improves the drawbacks of conventional methods. That is, by filling the gap between the earth and the propulsion tube with a small-diameter spherical elastic body made of a specific type of superabsorbent polymer, the properties of the spherical elastic body as a solid object, such as bearing action and Based on its excellent features such as good water retention and high strength when swollen, it improves the durability of its good anti-friction effect and enables wide application to various types of ground. The superabsorbent polymer used in this invention becomes a spherical elastic body after absorbing water, and is a saponified copolymer obtained by suspension polymerization of vinyl ester and acrylic acid or its ester. ,or,
Consists of a crosslinked polymer of acrylic acid or its salt obtained by suspension polymerization. Suspension polymerization of vinyl ester and acrylic acid or its ester is carried out at a molar ratio of 20:80 to 80:
It is preferable to do this in the range of 20. As the vinyl ester, vinyl acetate is preferably used. As the acrylic acid or its ester, acrylic acid, methacrylic acid, or their methyl ester, ethyl ester, etc. are used. Suspension polymerization is essential for obtaining an elastic body that becomes spherical when it absorbs water. There are no particular limitations on the water absorption rate and average particle size of the superabsorbent polymer, which becomes a spherical elastic body when water is absorbed, but this water absorption capacity is 300 to 3000 times that of distilled water, and after absorbing distilled water, the water absorption capacity is 0.01 A material that forms a spherical elastic body with a diameter of mm to 15 mm is practically preferably used. In carrying out the present invention, when injecting the antifriction material into the gap between the ground and the propulsion pipe, a superabsorbent polymer that becomes a spherical elastic body when it absorbs water can be used alone. Traditionally used minerals, organic thickeners,
Although it is not necessary to use surfactants, oils, etc., they can be used together with the superabsorbent polymer of the present invention which becomes a spherical elastic body when water is absorbed. Although there is no particular limitation on the proportion of superabsorbent polymer used as a spherical elastic body as an anti-friction material, the effect generally increases as the mixing rate increases. The present invention will be explained in further detail by referring to Reference Examples and Examples below. Of course, this invention is not limited to these. Reference example 1 Add 0.5 g of benzoyl peroxide as a polymerization initiator to 60 g of vinyl acetate and 40 g of methyl acrylate, and add 0.2 g of partially saponified polyvinyl alcohol (degree of saponification 88 mol%, degree of polymerization 2000) and 8 g of sodium chloride. The resulting mixture was dispersed in 200 ml of water and subjected to suspension polymerization at 65°C for 6 hours. Next, 30 g of the above copolymer was added to a solution of 16.2 g of sodium hydroxide dissolved in a mixed solvent of 100 ml of methanol and 30 ml of water, and saponification was carried out at 80°C for 2 hours and then at 60°C for 5 hours. After the saponification reaction was completed, the product was sufficiently washed with methanol and then dried under reduced pressure to obtain 24 g of a spherical dry saponified product having a particle size of 20 μm to 200 μm. The spherical saponified product thus obtained was insoluble in water and quickly swelled in water to become a spherical elastic body. Water absorption rate for distilled water is 750
g/g. Reference Example 2 133.1 g of water was placed in a polymerization tank, and 44.7 g of sodium hydroxide was added and dissolved with stirring. While cooling with ice, 100 g of acrylic acid was gradually added and neutralized with stirring. Potassium persulfate 0.0667g and N・N'-methylenebisacrylamide 0.01g
Add. Furthermore, add 6.0 g of sorbitan monostearate and 700 ml of normal hexane, and add 6.0 g while stirring.
Polymerization was carried out at ℃ for 3 hours. After the polymerization was completed, 125.2 g of a spherical superabsorbent polymer was obtained by separating solid and liquid and drying under reduced pressure. The particle size of the obtained superabsorbent polymer was 10μ to 150μ. Also, the water absorption rate is 560g/
It was hot at g. Example 1 The superabsorbent polymer obtained in Reference Example 1 was used as a component of an anti-friction material, and sandy soil was mixed in various proportions. At this time, the blending ratio of the anti-friction material was as shown in Table 1 below.

[Table] The internal friction angle and adhesion strength of this soil mixture were determined by an immediate shear test. The results are shown in Figure 1 in comparison with the case where the conventionally used bentonite mud type antifriction material was mixed with sandy soil. The effect of conventional bentonite mud type anti-friction material is that the mixing ratio of anti-friction material (weight of anti-friction material/weight of mixed soil) is approximately 15
There is almost no effect at the lower end of %, and the effect rapidly becomes apparent between 15% and 30%. On the other hand, the anti-friction material of the present invention is approximately proportional to the mixing ratio, and the effect of the anti-friction material appears. (friction coefficient tanψ decreases). This shows that the anti-friction material of this invention has better sustainability of the anti-friction effect even when the mixing ratio of the anti-friction material becomes low due to the mixing of ground soil into the anti-friction material. Furthermore, it is shown that the friction reduction effect is excellent when the mixing ratio is less than 30%. Further, even when the superabsorbent polymer obtained in Reference Example 2 was used, similar effects were obtained. Example 2 The same anti-friction material prepared in Example 1 was used and field tested. The soil quality was a fine sand layer, the N value was 5 to 10, the unit volume weight γ _t = 1.9 t/m ³ , the soil cover H = 12 m, and the groundwater level was 1 m below the ground surface. Figures 2 and 3 show the results of propelling a propulsion tube with an inner diameter of 900 mm using the mud propulsion method. In these figures, the vertical axis represents the thrust force (tons) of the main thruster, and the horizontal axis represents the propulsion distance. In the test, no anti-friction material was used until the propulsion distance was 20 m, and then the anti-friction material of the present invention was injected as the excavation progressed. In FIGS. 2 and 3, black dots (.) indicate actual measured values of main push jack propulsion (tons) and propulsion distance (m). Further, the solid line is the estimated curve when no anti-friction material is used, the broken line is the estimated curve when the conventional anti-friction material is used after the propulsion distance of 20 m, and the dashed-dotted line is the curve of the actual measured values. Assuming that the allowable load carrying capacity of the propulsion tube is 298.6 tons, the estimated maximum propulsion distance when using conventional anti-friction materials is 66 m and 149 m, respectively, in Figure 2, and 60 m and 176 m, respectively, in Figure 3. The distance increases approximately 2.3 to 2.9 times. Example 3 A field test was conducted using the super absorbent polymer obtained in Reference Example 2 and an anti-friction material prepared with the same formulation as in Example 1. The soil is a fine sand layer, and the N value is over 50.
Unit volume weight γ _t =1.8t/m ³ , earth cover H≒11m, and groundwater level was approximately -3m. The project was carried out using a mud propulsion method using a propulsion tube with an inner diameter of 800 mm. The results are shown in FIG. In the experiment, no anti-friction material was used up to a propulsion distance of 20 m.
The anti-friction material was then injected as the excavation progressed. In Figure 4, the solid line is the estimated curve when no anti-friction material is used, the broken line is the estimated curve when the conventional anti-friction material is used after a propulsion distance of 20 m, and the dashed-dotted line is the estimated curve when the anti-friction material of this invention is used. The curve of actual measured values is shown. Assuming that the allowable load capacity of the propulsion tube is 229.6 tons,
The estimated maximum propulsion distance when using the conventional anti-friction material is 68 m, and the estimated maximum distance when using the anti-friction material of the present invention is 356 m, approximately 5.2 times longer. Example 4 Using the spherical superabsorbent polymer obtained in Reference Example 1 and the Na salt of a conventionally known starch-acrylonitrile graft compound partial hydrolyzate (100 mesh pass product) (referred to as amorphous hydrogel), the following was prepared. Each antifriction material was prepared according to the formulation shown in Table 2.

[Table] Using the obtained anti-friction material, field tests were conducted under the following conditions. <Field test conditions> Soil quality Clay mixed with shellfish N value 0 to 3 Unit volume weight rt = 1.6t/m ³ Earth cover H = 6.25m Groundwater level -1.0m to -1.5m from the ground surface Propulsion method Blind propulsion method Propulsion pipe Nominal diameter Inner diameter 1800mm In addition, in the test, no anti-friction material was used until the propulsion distance was about 20 m, and then comparative anti-friction material was injected into the section from about 20 to 50 m, and this was used for the subsequent propulsion distance. The anti-friction material of the invention was injected. Figure 5 shows the relationship between the propulsion distance (m) and the original thrust (tons) in this test. In the figure, sections (a) to (b) do not use anti-friction materials, sections (b) to (c) use comparative anti-friction materials, and sections (c) to
(d) shows the case where the anti-friction material of this invention is used. In addition, the broken lines (b) to (b') and (c) to (c') exclude the relationship between the propulsion distance and the main push jack thrust in the sections (a) to (b) and (b) to (c), respectively. This is what I inserted. Furthermore, (b) to (d') show the relationship between the propulsion distance and the thrust force of the main thrust jack when the anti-friction material of this invention is used from point (b) in the sections (c) to (d). This is what I was looking for. From this result, the thrust per 1 m of propulsion distance in each section is as shown in Table 3.

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the friction reducing agent mixing ratio and the friction coefficient (tanψ) of the friction reducing agent mixed soil of the present invention. In the figure, the horizontal axis is the anti-friction material mixture ratio (weight of anti-friction material/
Mixed soil weight x 100) (%) is shown. Figures 2 and 3
FIG. 4 is a graph showing the relationship between the original jack thrust and the propulsion distance when the anti-friction material of the present invention is used. A: Estimated thrust when no anti-friction material is used.
B: Estimated thrust when using conventional anti-friction material after 20m propulsion without using anti-friction material. C: No anti-friction material 20
Actual value when using the anti-friction material of this invention after m propulsion. FIG. 5 is a drawing showing the relationship between the propulsion distance (m) and the original jack thrust (t) when the propulsion pipe is installed by the propulsion method while using different anti-friction materials.

Claims (1)

[Scope of Claims] 1 In the propulsion method, a highly water-absorbing material which becomes a spherical elastic body when it absorbs water and is a Ken compound of a copolymer obtained by suspension polymerization of vinyl ester and acrylic acid or its ester. A propulsion method that reduces the frictional force between the soil and the propulsion tube, which is characterized by mixing spherical elastic bodies that have absorbed water molecules into the spaces between the ground and the propulsion tube. 2 In the propulsion method, the spherical elastic body becomes a spherical elastic body when it absorbs water, and the spherical elastic body that absorbs water is made of a super absorbent polymer, which is a crosslinked polymer obtained by suspension polymerization of acrylic acid or its salt, and is propelled with the ground. A propulsion method that reduces the frictional force between the propulsion pipe and the soil, which is characterized by being mixed into the voids in the pipe.