JPH10220171A - Method of shield tunneling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain fluidity in a chamber and make fluidity disappear on the outside of the chamber even in the excavation of a permeable ground, and to conduct excavation stably by a normal shield machine by utilizing the thickening action of sodium alginate and the gelation reaction of sodium alginate at different times. SOLUTION: A mud additive, in which clay, bentonite and water are mixed, is injected into the chamber of a shield machine, and excavation is performed while discharging mud, in which the mud additive and excavated materials are mixed, from the inside of the chamber. The inside of the chamber is supplied with sodium alginate or a thickening agent consisting of water-soluble high molecules when occasion demands together with the mud additive or apart from the mud additive at that time, and sodium alginate and the thickening agent are made to exist in mud under the state not gelled in the chamber. When mud is discharged from the inside of the chamber, polyvalent metallic salts excepting a magnesium salt such as calcium chloride are injected into a screw conveyor for discharging mud, and mud is gelled by utilizing the gelation reaction of sodium alginate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of imparting appropriate fluidity to materials in a chamber when excavating while pouring a mud material into a chamber of a shield machine, and providing fluidity to earth removal. It relates to the shield method to be eliminated.

[0002]

2. Description of the Related Art A mud pressurized shield method in which a mud is poured into a chamber of a shield machine and excavated while discharging the mud in the chamber in which the mud and the excavated soil are mixed from the chamber. As clay, bentonite,
A water-soluble polymer-based thickener such as carboxymethyl cellulose (CMC) mixed with water and having a specific gravity of 1.1 to 1.4 and a viscosity of about 1000 to 5000 cP is used. Injection gives fluidity to the material in the chamber. The mud in the fluidized chamber is discharged from the chamber by a screw conveyor.

However, when excavating a highly permeable ground such as a gravel ground, when the fluidity of the mud is increased by injecting the mud material, the ground water pressure is erupted or the mud is dripped without riding on a belt conveyor. Therefore, it is not preferable for excavation work. In addition, since it is difficult to transport mud with high fluidity to the ground and transport it with a dump truck, it must be removed after treatment with lime or cement-based solidifying agent, which leads to an increase in labor and transport volume, which is preferable. Absent.

[0004] For this reason, when excavating a sandy or gravel ground where it is difficult to stop water, measures to reduce the fluidity of the mud, such as extending a screw conveyor for discharging mud from the chamber or adding a rotary feeder, etc., are called. Mechanical water stoppage measures, increasing the viscosity and specific gravity of the mud
Alternatively, measures such as adding a polymer flocculant to the mud material have been taken to reduce the fluidity of the mud.

[0005] Further, a natural water-soluble polymer such as guar gum, which has been surface-treated with an acid-decomposable film, is added to a mud material, and when the mud is discharged by a screw conveyor, acid is added to break the film. However, a special method has been proposed in which the viscosity of the excess water in the mud is increased (the fluidity is suppressed) by the thickening action of the natural water-soluble polymer.

[0006]

[Problems to be Solved by the Invention] The method of taking a mechanical water stoppage measure for highly permeable ground such as gravel ground requires modification of mechanical equipment and may not be applicable to other grounds. In addition, the equipment cost becomes excessive, and there is a limit to reducing the fluidity of mud by mechanical means alone, even if the equipment becomes large.

Further, when a polymer flocculant is added to the mud material, a flocculation reaction occurs in the chamber and the fluidity of the mud inside the chamber is reduced, so that an excessive torque for stirring is required. This is not preferable in that respect. The same problem occurs when the viscosity and specific gravity of the mud material to be injected are increased.

Further, in the above method of blending the surface-treated natural water-soluble polymer, the natural water-soluble polymer added to the soil is dissolved in water. For sites where it is necessary to promote the biodegradation of water-soluble polymers and do not have a capacity to stock the residual soil, the waste will be treated with lime or cement-based solidifying material and discharged as described above. There is a problem that leads to an increase in

An object of the present invention is to solve the problem in such a mud pressure shield method.

[0010]

According to the present invention, a shield material is injected into a chamber of a shield machine, and excavates while discharging mud mixed with the mud material and excavated earth and sand from the chamber. In the construction method, a sodium alginate and, in some cases, a thickener composed of a water-soluble polymer are supplied into the chamber together with or separately from the mud, and magnesium salt is added to the mud discharged from the chamber. The present invention provides a shielding method characterized by adding a polyvalent metal salt to be excluded.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides an appropriate fluidity to a material in a chamber when digging while pouring a muddy material into a chamber of a shield machine. Has a characteristic that the fluidity is lost, and in particular, the fluidity is lost using a gelation reaction of sodium alginate.

[0012] Sodium alginate itself is a natural polymer obtained by alkaline extraction of calcium alginate, a seaweed component, and it dissolves in water to form a viscous paste.
It is used as an adhesive and a thickener as a paste. It is also a highly safe compound as recognized as a food additive. Sodium alginate does not gel when dissolved in water, but has the unique property of forming an insoluble strong gel by ion exchange when polyvalent metal ions other than magnesium are added to the solution. The present invention utilizes this unique property of sodium alginate to eliminate the fluidity of mud discharged from a chamber in the shield method.

That is, a suitable amount of sodium alginate is added to the mud material to be injected into the chamber of the shield method, or sodium alginate is supplied separately from the mud agent into the chamber in a powdered or dissolved state in water. Thus, the mud is allowed to exist in the mud without being gelled in the chamber, and at the stage when the mud is discharged from the chamber, a polyvalent metal salt other than magnesium is added to the mud to cause gelation. As a polyvalent metal salt for gelling, a calcium salt such as calcium chloride is most convenient for handling.

As the mud material used in the method of the present invention, the same material as that of the conventional one can be used. That is, a mixture of clay, bentonite, and water, or a mixture of a water-soluble polymer-based thickener such as carboxymethyl cellulose (CMC) and water can be used.

When sodium alginate is added, the viscosity of the material in the chamber is increased as compared with the case where sodium alginate is not added. However, the sum of sodium alginate and other ordinary thickeners (eg, CMC) to be added to the mud material is added. Then, the overall viscosity may be adjusted. In other words, when imparting appropriate fluidity to the mixed material of excavated earth and sand and mud in the chamber, the CM is used to provide material separation resistance even if the fluidity is increased.
It is common practice to add thickeners such as C to the mud, but it is sufficient to reduce the amount of thickener such as CMC by the amount by which the thickening effect of adding sodium alginate increases. This avoids excessive viscosity.

Therefore, even if sodium alginate is supplied to the material in the chamber, there is no problem such as an increase in the agitation torque of the mud as in the case of coagulating the material by adding a polymer flocculant, and good fluidity is obtained. Can be maintained. In this way, sodium alginate is added to the mud as part or all of the thickener to be added to the mud, or sodium alginate is supplied to the chamber separately from the mud, to increase the water permeability. Even when excavating ground, the purpose of the mud pressure shield can be sufficiently achieved because the material in the chamber can be given appropriate viscosity and fluidity.

[0017] Once out of the chamber, the fluidity of the mud can be eliminated when a polyvalent metal salt other than magnesium is added. In particular, when a polyvalent metal salt is added to a screw conveyor for discharging mud from the chamber, gelation can be advanced in a conveying process in the screw conveyor. When it is not preferable that the gelation occurs too quickly, a reaction retarder for delaying the gelation reaction may be added. Examples of the reaction retarder include sodium tripolyphosphate,
Chelating agents such as sodium hexametaphosphate, sodium carbonate, disodium ethylenediaminetetraacetate, and sodium hydrogencarbonate may be used. The addition of the reaction retardant may be performed before or before the addition of the polyvalent metal salt, and may be performed, for example, when adding sodium alginate.

When the polyvalent metal salt is added to the mud, it is convenient in practical operation to add an aqueous solution of the polyvalent metal salt, for example, an aqueous solution of calcium chloride from an injection port provided in the screw feeder. By the addition of the calcium chloride aqueous solution, sodium alginate in the mud being conveyed while being stirred in the screw conveyor gradually becomes an insoluble gel, and the fine substance in the mud is wrapped in the insoluble gel. Accumulates at the outlet while losing fluidity. The waste fluid that has lost its fluidity accumulates near the end of the screw conveyor, which acts as a plug, preventing liquid with high fluidity from escaping from near the outlet from inside the pressurized chamber. In addition, the back pressure is sufficiently maintained by the plug action, so that the face can be prevented from collapsing.

As described above, by reforming the mud with high fluidity in the chamber so that the fluidity is lost in the process of discharging the mud with the screw conveyor, the mud is stable even in the ground where water stopping is difficult. Excavation can be performed. And after being discharged from the screw conveyor,
At the stage of storage in the primary storage tank, the water rises upward in a short time due to its own weight and separates into solid and liquid from the sediment. Therefore, by discharging this water, it is easy to obtain earth removal with a reduced water content . This earth removal is close to the original ground condition, and has sufficient strength to be able to be carried out as it is without secondary treatment with lime or cement-based solidification material. Therefore,
It can be sufficiently used as embankment material and vegetation soil without a rise in pH. On the other hand, since the alginate gel in the wastewater is not harmful at all, no special secondary treatment is required for the wastewater.

The addition of a polyvalent metal salt, for example, an aqueous solution of calcium chloride can be carried out by dividing into a screw conveyor and a storage tank in some cases. In other words, depending on the condition of the excavation ground, the screw conveyor can only stop the fluidity to a sufficient extent to stop the water stoppage, and can completely gelate in the storage tank to sufficiently discharge the pore water.

[0021]

【Example】

[Example 1] A mud material was prepared by mixing clay and an admixture in the following composition. Kadorozai 1m ³ per clay: 100Kg Matomaru D2: 1Kg FY gel 10Kg water 1000L

Here, "Matmar D2" is a trade name of a thickener manufactured by Daiko Bussan Co., Ltd. The main component of the thickener is a polyacrylamide / sodium acrylate polymer. “FY gel” is a trade name of a flocculant manufactured by Daiko Bussan Co., Ltd., and its main component is sodium alginate.

The mud material having the above-mentioned composition is saturated with soil (water 11%) collected from the gravel layer ground until it becomes saturated (15 to 15%).
(20% by volume) and the fluidity when stirred was evaluated by a slump value. The slump value was 18 to 20.
cm.

An aqueous solution obtained by adding 40% by weight / weight of calcium chloride (dihydrate) to water was added to the fluidized mud and stirred at 0.5% by volume. It became 0-5 cm, and it was in the state of high self-reliance. When this was allowed to stand for 30 minutes, pore water was spontaneously released, and a compact was obtained. It was in a state similar to the tested earth and sand.

Example 2 30 kg of FY gel and 100 parts of water
Mixed 0L,. 15 to this for gravel-based sand 1 m ³
Twenty parts by volume were mixed and stirred. The slump value of the obtained mixture was 18 to 20 cm. The slump value when adding an aqueous calcium chloride solution and stirring in the same manner as in Example 1 was 0 to 5 cm. When this was allowed to stand for 30 minutes, pore water was spontaneously released, and a compact was obtained. It was in a state similar to the tested earth and sand.

Example 3 10 kg of FY gel, 7 kg of Matmar D2 and 1000 L of water were mixed with 1 m ^{3 of} gravel-based earth and sand and stirred. The slump value of the resulting mixture was 15-20 cm. Example 1
The slump value when the calcium chloride aqueous solution was added and stirred in the same manner as in Example 1 was 0 to 5 cm. This is 3
When left for 0 minutes, pore water was released spontaneously and a compact was obtained. It was in a state similar to the tested earth and sand.

[0027]

As described above, according to the present invention,
By using the thickening action of sodium alginate and its gelling reaction at different times for the shield method, it is possible to maintain good fluidity in the chamber even when excavating permeable ground with difficult water stoppage. Since the fluidity can be lost when it comes out, it is possible to stably excavate with a normal shield machine without using a special device that mechanically configures the water stop plug.

Further, since alginate gel is a harmless substance, it is possible to avoid polluting the environment, and the effluent obtained by carrying out the method of the present invention is a residual soil having a strength close to the ground and wastewater that can be discharged. Because of this, removal and disposal can be performed easily. In addition, since the residual soil is not solidified with lime, cement, or the like, it is advantageous in that it can be reused for embankment and vegetation soil.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuji Ikezoe, 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. (72) Inventor Nobuyuki Hanawa 1-2-1, Moto-Akasaka, Minato-ku, Tokyo No. 7 Inside Kashima Construction Co., Ltd.

Claims (5)

[Claims] 1. A shield method in which a mud material is injected into a chamber of a shield machine and excavation is performed while discharging mud mixed with the mud material and excavated earth and sand from the chamber. A shielding method, characterized in that sodium alginate is supplied together with or separately from mud material, and a polyvalent metal salt other than a magnesium salt is blended into mud discharged from the chamber. 2. A shield method in which a mud material is injected into a chamber of a shield machine and excavation is performed while discharging mud mixed with the mud material and excavated earth and sand from the chamber. A thickener comprising sodium alginate and a water-soluble polymer is supplied together with the mud or separately from the mud, and a polyvalent metal salt other than a magnesium salt is blended into the mud discharged from the chamber. Shield construction method. 3. The shielding method according to claim 1, wherein the polyvalent metal salt is a calcium salt. 4. The multivalent metal salt is injected into a screw conveyor for discharging mud from the chamber.
Or the shield method described in 3. 5. The shielding method according to claim 1, wherein a gelling reaction retarder is added before or before adding the polyvalent metal salt.