JPH0249893A - Additive material for mud pressure shield - Google Patents

Abstract

PURPOSE:To improve the extent of shield effect by containing air bubbles muddy water consisting of a montmorillonite clay mineral inorganic extender, carboxymethylcellulose - sodium salt, an anionic surface active agent and water. CONSTITUTION:A bottom plate bored with a small hole of about 1mm in diameter is installed in an acrylic cylinder 1, and each pebble in size of the remnant of about half of the eyes of a sieve, run past the sieve opening of 10 times over the small hole 2 is charged in this cylinder 1. Next, bubble content muddy water A large in viscosity and inclusive of blinding material and a bubble content aqueous solution poor in viscosity and uninclusive of a solid portion as the blinding material both are put in a space 5 by the same quantity at a time and compared with each other. The, A is confined to 20% in infiltration after the elapse of 30 minutes, while B is made to quickly flow down in a pebble layer clearance and infiltrated in the whole pebble layer within 30 minutes. With this constitution, a bubble A solution has effectiveness for mud pressure type shield work applying ground enlargement, so that a merit for shield work is thus improvable.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an additive composition for shield excavation work.

(Conventional technology) Various methods have been developed for shield excavation work necessary for constructing subways, underground roads, sewers, etc. depending on the ground conditions (geology and groundwater conditions), but each method has its own disadvantages and advantages. The most suitable construction method is adopted depending on the condition of the ground to be constructed. In recent years, the bubble shield construction method (Special Publication Showa 5B-4
7560) was developed, and its performance in imparting fluidity to excavated soil through the bearing effect of air bubbles, as well as its ability to impart watertightness by retaining air bubbles, was highly praised.In particular, its ease of processing and disposing of excavated soil was highly praised, and it became popular. is increasing. This construction method is a progressive construction method that skillfully utilizes the above-mentioned effect of stably retaining air bubbles in the soil, but it also has inherent problems. In other words, if the ground has many voids, for example, the permeability coefficient is 1.
If the ground or excavated soil layers are on the order of 0 to 10 cm/sec and are alternate layers containing layers with many gaps,
The amount of air bubbles decreases due to loss of the injected air bubbles or dilution of groundwater, and the necessary amount of air bubbles is not mixed into the excavated soil. Therefore, the expected fluidity and water-stopping properties may not be provided and smooth excavation may not be possible.

(Problems to be Solved by the Invention) The present inventor has determined that the problem with the bubble shield method described above is due to the easy loss of the foam material, and the cause of this is the low viscosity of the foam material. It is assumed that this is because it easily penetrates into the ground gap because it does not contain a filling material. It has been found that an additive material containing a filler material does not dissipate even in the ground with many gaps, and can provide soil fluidity and water-stopping properties.

Furthermore, air bubbles of the size necessary for imparting soil fluidity were created for a long time (5
~12 hours) Higher viscosity is better for retention, but
It has been found that fluid viscosity and interfacial tension must be appropriately balanced in order to reduce the size of bubbles. In this way, it is necessary to balance these conflicting performances and to select inexpensive constituent materials. An object of the present invention is to provide an additive for mud pressure shielding that meets the above objectives.

(Means for solving the problem) The above problem is solved by the present invention, which is a muddy water consisting of a montmorillonite clay mineral, an inorganic filler, carboxymethylcellulose sodium salt having a 1% aqueous solution viscosity of 3000 cps or more, an anionic surfactant, and water. This problem can be solved by incorporating air bubbles into the bubbles.

With the configuration of the present invention, the viscosity of a 1% aqueous solution (viscosity at a rotor rotation of 60 rpm using a B-type viscometer) is 3000c.
When montmorillonite clay mineral fine powder is added to an aqueous solution in which a small amount of carboxymethyl cellulose sodium salt (hereinafter referred to as high viscosity CMC) is dissolved, the viscosity increases significantly. The slurry obtained by adding an anionic surfactant to impart foaming properties is forcibly stirred using a high-speed stirrer. At this time, air is drawn in and a viscous fluid is obtained which is dispersed in large quantities as fine bubbles. In the present invention, this is referred to as bubble-containing muddy water, but the properties of this bubble-containing muddy water vary depending on the composition, but initial muddy water (muddy water without bubbles)
The volume of fluid becomes more than 2.5 times the volume. The foam-containing mud obtained by the present invention has a thicker viscosity than the foam material produced by the foam shield method (and contains plugging material, so it penetrates into the ground with many gaps more than necessary). It has been confirmed that the water remains at a certain penetration depth, and it is expected that it will be difficult for it to be lost.

An important point in the present invention is the synergistic effect of high viscosity development by combining a small amount of highly viscous CMC with a relatively small amount of montmorillonite clay mineral. This synergistic effect gives the present invention an economical advantage over the foam material of the bubble shield method.

The higher the viscosity, the better the air bubble retention; if the viscosity is low, syneresis (a phenomenon in which air bubbles and muddy water separate) occurs when the viscosity is left standing for a short period of time, and the integrity of the fluid is lost, resulting in poor water-stopping properties of excavated soil. becomes insufficient.

In the case of implementing the present invention, the viscosity of the bubble-containing mud (viscosity when the rotor rotation speed is 6 Orpm using a B-type viscometer) is 150.
0 to 2600 cps is suitable. This viscosity varies depending on the type and amount of high-viscosity CMC, the type and amount of montmorillonite clay mineral, the type and amount of inorganic filler, etc., but the amount of each component added is not particularly limited.
The minimum amount necessary to achieve the desired purpose may be determined experimentally.

The montmorillonite clay mineral used may be from any source, but it is desirable that it has a high montmorillonite content and is inexpensive. Any type of inorganic filler may be used as long as it is a fine powder, but one with a small particle size is preferable. In addition, kaolinite clay minerals have good water retention properties and are therefore advantageous in developing viscosity and are preferred as fillers. The anionic surfactant is not particularly limited, but it is desirable to have good foaming properties, and sodium alkyl ether sulfate type surfactants are preferred.

Appropriate items for evaluating the performance of the bubble-containing muddy water of the present invention include bubble size, syneresis time, and viscosity.

(Effect of the invention) The purpose of the present invention is to provide a hybrid type shielding additive material in which fine air bubbles are contained in highly viscous muddy water, which complements the shortcomings of conventional foam materials and expands the application ground for earth pressure shielding construction. It is effective and economically advantageous, and has great advantages in shield construction.

Embodiments of the present invention will be described below with specific examples.

Example 1 C with a 1% aqueous solution viscosity of 8000 cps in 200 d of water
Add and dissolve 7 g of MCO and 2 cc of a 25% aqueous solution of sodium lauryl ether sulfate, add 2 g of bentonite (Asama Seal manufactured by Toyosun Mining Co., Ltd.) and 10 g of FC powder (manufactured by Shoei Sangyo Co., Ltd.), and mix with a household mixer. ．．
Stir for 5 minutes. The obtained foam-containing muddy water was 600
It has a volume of - and contains a large amount of bubbles with a diameter of about 0.3+w+s. This foam-containing muddy water did not change in volume even after 5 hours had passed after its creation, and its foam retention was good. In addition, the viscosity measured by a B-type viscometer (60 rpm) was 1880c.
It was ps.

Comparative Example 1 Adding foaming agent 0K- designated by the bubble shield method to 200 ml of water.
1 and 2 g of thickener 0K-2 were dissolved, and the mixture was stirred for 1.5 minutes using a household mixer in the same manner as in Example 1. The bubble-containing aqueous solution (albeit muddy water) at this time was 550-. When this product was allowed to stand still for 30 minutes, a syneresis phenomenon was observed. That is, the bubble retention property is not as good as that of Example 1. Further, when the viscosity was measured, it was 500 cps, which was considerably lower than that of Example 1.

Example 2 In place of CMC in Example 1, a 1% aqueous solution with a viscosity of 4000
The properties of the bubble-containing muddy water, which was prepared in the same manner as in Example 1 except that 1 and 2 g of CMC, which is cps, were used, were almost the same as those in Example 1.

Comparative Example 2 A sample was prepared under the same conditions as in Example 1 except that the anionic surfactant (sorbitan monolaurate) was used.
Foamability was poor and the bubble content was extremely low. From this, it is understood that the use of an anionic surfactant is an essential condition for carrying out the present invention.

Example 3 Using Mt. Asama sand (produced in Futtsu, Chiba Prefecture), the volume of the foam-containing muddy water of Example 1 and the foam material of Comparative Example 1 was added to a sample whose water content ratio (13%) was adjusted so that the slump value was O. The flow value of the 22% mixture was determined as follows.

Not added Example 1 Sand of Comparative Example 1 Added Added flow value 145 205 180 (mm) The additive material according to the present invention has the effect of imparting fluidity to soil similar to the foam material.

Example 4 As shown in Fig. 1, an acrylic cylinder (1) with an inner diameter of 5 cm and a height of 25 cm was provided with a bottom plate (3) having a small hole (2) of 1 mm in diameter, and a hole with an opening of 10 mm+ was placed inside the cylinder. Gravel (4) of a size that passes through a sieve and remains on a sieve with an opening of 5 mm is placed at a height of 2
The foam-containing muddy water (A) of Example 1 and the foam-containing aqueous solution of Comparative Example 1 (A) were filled in the upper 5 cm space (5).
The same volume of B) was added and the permeation status into the gravel layer was compared.

Liquid B has a low viscosity and has no solid content as a filler, so it flows down the gaps between the gravel layers relatively quickly, and penetrates the entire gravel layer after 30 minutes. Due to the presence of the filler, only 20% of the initial volume had penetrated even after 30 minutes. Figure 2 shows how the permeation distance of each liquid changes over time.

In other words, the foam-containing muddy water according to the present invention is shown to have a superior effect of filling the gaps between gravel layers compared to the conventional foam material.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the infiltration experimental apparatus. FIG. 2 is a diagram showing the relationship between penetration distance and time, in which the mark "." indicates Example 1, and "-." indicates Comparative Example 1. The symbols in the figure are: 1 Acrylic cylinder 2 Small hole 3 Bottom plate 4 Gravel 5 Bubbly-containing mud water

Claims (1)

[Claims] An additive material for mud pressure shielding, characterized in that air bubbles are contained in mud water consisting of a montmorillonite clay mineral inorganic filler, carboxymethyl cellulose sodium salt having a 1% solution viscosity of 3000 cps or more, an anionic surfactant, and water. .