JPH0631538B2 - Stabilizer used for shield method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a stabilizing solution used in a shield construction method using a sealed shield machine.

[Conventional technology]

As is well known, in tunnel construction using a closed shield machine, a shield machine is used in which a closed chamber is formed between the cutter head and the partition behind it, while the chamber is filled with excavated soil or under pressure muddy water. It is used as an earth pressure type shield and the latter is commonly used as a mud pressure shield. In each case, various improvements have been made depending on the soil quality and location conditions, and mud pressure, bubble shield, resin shield, etc. have been proposed to improve pressure resistance and water stoppage. Especially in the mud pressure shield, it is important to control the stabilizing liquid (also called sludge material) supplied to the chamber, and it is necessary to secure an appropriate viscosity according to the properties of the excavated soil.

Conventionally, as such a stabilizing solution, the one in which powdered clay is used as a main ingredient and bentonite or a cellulose-based water-soluble polymer is mixed to prepare a mud is most commonly used.

[Problems to be solved by the invention]

In the case of conventional stabilizers using bentonite as a thickener,
Since bentonite is a substance designated as industrial waste, it is necessary to take special measures for soil disposal. Bentonite has a characteristic that it does not swell completely until a long time has passed after mud preparation. Therefore, in order to secure the set viscosity, it is necessary to secure a storage amount for a considerably long time. Therefore, there is a problem that the equipment becomes large and the workability is poor. Bentonite is a substance contained in prepared mud water and excavated mud, such as iron and humic acid in groundwater, salt in seawater, and acidic and alkaline substances.
It is likely to be adversely affected by such factors as a result, and as a result, there is a risk that the viscosity of the stabilized liquid prepared will change.

In the case of conventional stabilizers that use cellulosic water-soluble polymers (usually carboxymethyl cellulose: CMC) as thickeners, mud-sucking work in the field can lead to muddy fish, which can be decomposed at high temperatures to maintain the stability. There is a danger of becoming difficult. Also, like bentonite, its characteristics are affected by the presence of a large amount of electrolyte.

The present invention is intended to provide a stabilizing solution for a shield construction method which does not have such a problem.

[Means for solving problems]

The stabilizing liquid (slurry material) used in the shield construction method of the present invention is
Calcium compound-containing powder, powdered clay or clay sand
A thickener consisting of sepiolite or attapulgite and, if necessary, cellulose water-soluble polymer was added as a water inhibitor, and then mixed with water at a ratio necessary to secure specific gravity and viscosity according to excavated soil. It was done.

As the weighting material used in the present invention, powdered clay or clay sand can be used as in the conventional case, and calcium compound-containing powder can be used. Ideally, these weighting materials are in the form of fine powder having an average particle size of about 200 to 400 mesh. As the calcium compound-containing powder, powders of minerals containing calcium as a component element such as calcium carbonate powder and dolomite powder are suitable. When such a calcium compound-containing substance is used as a bulking material, it becomes easy to treat the remaining soil of the waste mud after using the stabilizing solution. In other words, the soil discharged by the usual shield method is usually dehydrated and solidified. However, calcium components are mixed in this residual soil, so activated alumina or activated silica should be added to it. Therefore, quick setting treatment can be performed, and the required amount of quicklime, cement or cement-based solidifying agent can be reduced.

The sepiolite used in the present invention is preferably a sepiolite mineral powder-purified to a particle size of about 50 to 200 mesh. Sepiolite is a hydrous magnesium silicate mineral and has a fibrous crystal structure. This fiber structure is easily debunched when strongly stirred in water with a mixer, etc. When the debunched fibers are dispersed in water, the fibers are complicatedly entangled or disentangled, exhibiting unique flow characteristics and a thickening effect. Bring In the present invention, this property is utilized to achieve the thickening effect and the fluidity imparting effect as a stabilizing liquid in the shield construction method. Attapulgite also has properties similar to those of piolite, so that it can be used as a constituent material of the stabilizing solution of the present invention. It is also possible to use sepiolite and attapulgite in combination.

The blending ratio of the thickener consisting of sepiolite or attapulgite to the weighting material is selected according to the type of weighting material and the excavated mud. That is, after selecting an appropriate weighting material, its composition is selected so that the design viscosity and specific gravity can be obtained depending on the soil properties of the ground to be excavated in the shield work, the site conditions (earth pressure and water volume), and the characteristics of the sealed shield machine. To decide.

The stabilizing solution of the present invention can impart high viscosity with a small amount of thickener used, as compared with the conventional case where bentonite is used as the thickener. Generally, the blending amount of the thickener of the present invention is
2 to 20 parts by weight for 100 parts by weight of water, 10 to 2
It may be about 000 parts by weight, and the requirement can be sufficiently satisfied even if the required design viscosity range is wide.

In addition, the stabilizing solution of the present invention can improve mud water by adding a small amount of a cellulose-based water-soluble polymer as an admixture. The amount of CMC blended may be about 1 to 10% of the amount of the thickener for sepiolite or attapulgite.

[Example 1] Table 1 shows an example of blending and an example of the change in viscosity with time when calcium carbonate powder (tancal) is used as a weighting material and sepiolite powders A and B are used as thickeners. As a comparative example, the case where bentonite is used as a thickener is also shown. In each case, 100 parts by weight of water was added to 76 parts by weight of tantalum, and the thickener shown was added to the mixture at the indicated parts by weight, and a mixture was prepared using a mixer (3300 rpm). Viscosity is measured by Visco Tester (VT-04, Rotor N
o.1).

From the results shown in Table 1, it can be seen that the sepiolite powder exhibits a much higher thickening effect than bentonite, and that the thickening effect increases with time. Therefore,
The viscosity of the stabilizing solution of the present invention can be controlled by using a small amount of sepiolite powder.

[Example 2] In the case of the stabilizer of the present invention in which calcium carbonate powder was used as the weighting material and sepiolite powder was used as the thickener, the initial viscosity shown in the table was obtained.

The results in Table 2 show that, when the specific gravity of the thickening material and that of the thickener do not differ greatly, the specific gravity of the stabilizing solution should be maintained almost constant even if the viscosity is adjusted by changing the addition amount of the thickener. It is possible to do.

[Example 3] Powder clay as a weighting material, sepiolite powder as a thickening agent, low-viscosity CMC (GT-1 manufactured by Shikoku Chemical Industry Co., Ltd.) as an admixture (water preventive material), and a design specific gravity of 1.10, 1 .
Three levels of 15 and 1.20 were mixed in the formulations shown in Table 3, and the viscosity and water content were measured. Also, as viscosity increase, CMC
An example using only (Madecon SM manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) is also shown in Table 3 as a comparative example. In Table 3, the viscosity unit is Funnel viscosity / second 500cc / 500cc, and the water amount unit is ml.

As shown in the results of Table 3, the amount of water can be reduced by adding a small amount of CMC as a water-preventing agent, and the material separation can be prevented in the shield construction method to improve the water-stopping property.

[Example 4] Powder clay was used as a weighting material, and the composition of the composition was such that the design control value of viscosity was Funnel 33 / sec 500 cc / 500 cc, and sepiolite powder was used as a thickener to stabilize the present invention. Prepare a liquid and add 0%, 5%, 10%, 15% natural seawater to this stable liquid.
The change with time in viscosity when mixed in the amount of was measured.

The results are shown in FIG. It can be seen from FIG. 1 that the viscosity of the stabilizing solution of the present invention does not substantially change with time even when seawater is mixed.

〔The invention's effect〕

According to the present invention, a new sludge material for a shield construction method is provided which replaces the conventional Bennite or CMC. The stabilizing solution for the shield construction method of the present invention does not have the above-mentioned problems of Bennite and CMC. In particular, the property does not change or the viscosity and fluidity do not change due to the mixture of substances in seawater or excavated soil, so that the controllability of the stable liquid and the excavation workability can be favorably maintained. Further, since the stabilizing solution of the present invention does not contain a substance that causes secondary pollution, it is advantageous in terms of safety since the soil disposal process becomes simple. In addition, since the fluidity is significantly improved compared to the conventional stabilizer using Bennite, wear of the mud pump and mud pipe is reduced, maintenance of each device is improved, and mixing with excavated mud is achieved. Since it is good, the sludge draining work of the shield machine is rationalized, and effects that cannot be obtained with conventional stabilizing liquids are exhibited.

[Brief description of drawings]

FIG. 1 is a diagram showing a change with time in viscosity when seawater is mixed in a stabilizing solution according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukihiko Hizawa 1-11-7 Tsubuhoncho, Nishi-ku, Osaka City, Osaka Prefecture Shinano Hashi Mitsui Building Kashima Construction Co., Ltd. Osaka Branch (72) Inventor Yoshiaki Tamura Nishi-ku, Osaka City, Osaka Prefecture 1-11-7 Tsubuhoncho Shinano Hashi Mitsui Building Kashima Construction Co., Ltd. Osaka Branch (72) Inventor Yukihiro Akioka 19-23 Miyamaecho, Kadoma City, Osaka Prefecture (72) Tsutomu Sawada 361 Nakatara, Maibara-cho, Sakata-gun, Shiga Prefecture

Claims (2)

[Claims] 1. A shield construction method in which a thickening material comprising sepiolite or attapulgite is mixed with water in a powdery thickening material comprising one or more of calcium compound-containing powder, powdered clay or clay sand. Stabilizer to use. 2. A calcium compound-containing powder, powdered clay or clay sand, and one or more powdery thickening materials, a thickener made of sepiolite or attapulgite and a water-soluble cellulose-based polymer. Stabilizing liquid used in the shield construction method that is compounded together.