JPH10238281A - Shielding construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain blocking-up in an earth removing pipe when excavated earth and sand are fluidity carried, and restrain an increase in cutter torque by filling a working face surface with water and muddy water, and excavating the ground while injecting a dispersant into the vicinity of a cutter. SOLUTION: In a muddy water pressurizing shielding construction method to construct and create a tunnel, a working face surface is filed with water or muddy water, and the ground is excavated while injecting a dispersant into the vicinity of a cutter. Excavated earth and sand are fluidly carried as an earth removing liquid from an earth removing pipe, and the tunnel is constructed and created. Alkaline metal salt of a silicic acid, a metasilicic acid, a phosphoric acid, a polyphosphoric acid and a hexametaphosphoric acid and a hydroxide of alkaline metal are used as the dispersant. An adding quantity of the dispersant is added in the quantity ratio not less than 0.5 pts.wt. per water or muddy water 100 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield method in which a ground is excavated while filling a face with water or muddy water, and the excavated earth and sand is transported as a discharge liquid by a discharge pipe to construct a tunnel.

[0002]

2. Description of the Related Art When excavating a tunnel to be a passage for passing railways, roads, water, sewage, etc. through the ground, there is a shield method as a method of safely and easily constructing a tunnel particularly on soft ground.

[0003] As an example of this method, muddy water prepared by mixing water and bentonite or viscous soil generated in the field is pressurized and injected into the face of the cutting machine so that the space between the partition wall and the face of the shield machine at the rear of the cutter chamber is removed. There is a so-called muddy pressure shield method, in which the face is filled with muddy water to stabilize the face, and the tunnel is constructed by transporting the cut soil and soil as a draining liquid by using a discharging pipe.

[0004] Regarding this muddy water, "New system civil engineering
71 Tunnel (II), edited by the Japan Society of Civil Engineers, Chapter 2, Shield Tunnel, states that the specific gravity during construction of muddy water is 1.05
About 1.3, viscosity (funnel viscosity) is silt layer 25-3
0, sand layer 30-38, gravel layer 35-44,
It is made by mixing water and bentonite or viscous soil generated in situ, and often uses additives such as CMC (sodium carboxymethyl cellulose). "

[0005] Further, regarding the muddy water, when the ground to be constructed is a ground such as a silt layer or a clay layer having a high adhesive strength of soil particles, the excavated soil is used as a discharging liquid when discharging fluid through a discharging pipe. In order to prevent clogging due to blockage in clay pipes, lignin sulfonate or its derivative, oxyorganic acid salt, alkyl allyl sulfonate, polyoxyethylene alkyl ether, polyol complex, higher polyhydric alcohol sulfonate, melamine Various fluidizing agents containing a formalin condensate sulfonate as a main component are added to muddy water.

[0006] In addition, the earth removal liquid containing the cut earth and sand is pumped directly from the rear part of the shield machine cutter chamber by a pump, or if the discharge pipe opening cannot be installed at the rear part of the shield machine cutter room, After the earth removal liquid is conveyed by a screw conveyor from the rear of the cutter chamber to the mouth of the earth removal pipe, it is pumped by the earth removal pipe.

On the other hand, as a method for increasing the cutting efficiency of the ground, Japanese Patent Application Laid-Open No. 5-339935 discloses ligninsulfonic acid, naphthalenesulfonic acid, oxycarboxylic acid, polycarboxylic acid, alkylallylsulfonic acid, melamine as a fluidizing agent. At least one alkali metal salt or sodium hydroxide of each acid of sulfonic acid, such as sodium or calcium, or a formalin condensate thereof or silicic acid, metasilicic acid, phosphoric acid, polyphosphoric acid, hexametaphosphoric acid as a dispersant. Is added in an amount ratio of 1 to 10 parts by weight with respect to 100 parts by weight of earth and sand cutting water, and the method of cutting the ground by injecting the earth and sand cutting water into the ground from a small injection hole of an injection pipe is disclosed. I have.

[0008]

However, Japanese Patent Application Laid-Open No. 5-3
The method described in Japanese Patent No. 39935 is a method of injecting water for earth and sand cutting from a small injection hole of an injection pipe into the ground at a high pressure to cut the ground. It is inconvenient for an object that needs to be excavated with a constant diameter such as a tunnel because the excavation diameter is different due to the difference in soil quality in the excavation by water injection. There are inconveniences such as being unable to excavate, causing unevenness on the face and causing the face to collapse.

[0009] The construction method using a shield machine cutter does not have the above-mentioned problem because the excavation can always be carried out with a constant diameter. However, in the conventional construction method using a cutter, the construction target ground is especially soil layer or clay layer. High adhesion of particles,
In the case of ground where the drainage liquid causes blockage in the discharge pipe, the machine torque will increase due to the increase of the shield machine cutter torque, or the excavation efficiency of the ground will decrease and it will take a long time to excavate. There is a problem.

Further, when a screw conveyor is used to transport the discharging liquid discharged from the shield machine cutter chamber to the discharge pipe opening, the torque of the screw conveyor increases,
There is also a problem that mechanical wear increases.

In order to further solve the above problem, the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-339935 is applied,
When adding a dispersing agent such as an alkali metal salt of each acid of silicic acid, metasilicic acid, phosphoric acid, polyphosphoric acid, and hexametaphosphoric acid or sodium hydroxide to the muddy water, the muddy water is formed by the action of the dispersing agent component. Has the problem that the original purpose of muddy water, ie, stable face, cannot be achieved.

An object of the present invention is to solve the above-mentioned problems in the conventional method. In particular, the ground to be constructed has a high adhesive force of soil particles such as a silt layer and a clay layer, and the drainage liquid blocks the drainage pipe. It is an object of the present invention to provide a shielding method capable of suppressing a decrease in cutting efficiency and an increase in cutter torque, even in the case of a ground that causes a rise, and an occlusion in a discharge pipe and an increase in a screw conveyor torque.

[0013]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, excavated the ground while filling the face face with water or muddy water, and used the excavated earth and sand as a discharging liquid. In the shield method, in which a tunnel is constructed by carrying fluid through an earth removal pipe, excavating the ground while injecting a dispersant component near the cutter, especially when the ground to be constructed has an adhesive force of soil particles such as silt layers and clay layers With the conventional method, even in the case of soil where the drainage liquid causes blockage in the drainage pipe, the reduction of cutting efficiency and increase in cutter torque are suppressed, and the blockage in the drainage pipe and the screw conveyor torque The present invention was completed by knowing that the increase of the amount could be suppressed.

The present invention provides a shield construction method in which a ground is excavated while filling a face with water or muddy water, and the excavated earth and sand is transported as a discharge liquid by a discharge pipe to construct a tunnel. And excavating the ground while injecting at least one component selected from the group into the vicinity of the cutter. "

[0015] The dispersant used in the present invention may be any one which is usually used for accelerating the dispersion of soil particles in the suspension or preventing the suspension in the dispersed state from fluffing. Can be used, as a dispersant, silicic acid,
Preferred examples include those which are at least one component selected from the group consisting of alkali metal salts and alkali metal hydroxides of metasilicic acid, phosphoric acid, polyphosphoric acid, and hexametaphosphoric acid. It is preferable to add the dispersant in an amount ratio of 0.5 part by weight or more per 100 parts by weight of water or muddy water filling the face.

Hereinafter, the present invention will be described in more detail. The method of the present invention excavates the ground while filling the face face with water or muddy water, such as a muddy pressure shield method,
It can be applied to the shield construction method of constructing a tunnel by transporting fluid excavated earth and sand as earth removal liquid by earth removal pipe.

In the method of the present invention, when the ground is cut by the above shield method, it is selected from the group consisting of alkali metal salts and alkali metal hydroxides of silicic acid, metasilicic acid, phosphoric acid, polyphosphoric acid and hexametaphosphoric acid. The ground is cut while injecting at least one of them into the vicinity of the cutter.

Examples of the alkali metal salts of silicic acids such as silicic acid and metasilicic acid include sodium silicate, potassium silicate, lithium silicate and sodium metasilicate.

The alkali metal salts of phosphoric acids such as phosphoric acid, polyphosphoric acid and hexametaphosphoric acid include sodium phosphate, disodium phosphate, monosodium phosphate, and the like.
Examples thereof include sodium polyphosphate and sodium hexametaphosphate.

The alkali metal hydroxide includes:
Examples thereof include sodium hydroxide and potassium hydroxide.

Examples of the dispersant include salts of alkali metals such as sodium and calcium of ligninsulfonic acid, naphthalenesulfonic acid, oxycarboxylic acid, polycarboxylic acid, alkylallylsulfonic acid and melaminesulfonic acid, and formalin condensates thereof. If the components are not specified by the present invention, the effects intended by the present invention cannot be obtained.

In the method of the present invention, it is important to inject the dispersant into the vicinity of the cutter for excavating the ground, distinguishing it from water or mud which fills the face. Upon injection, the form of the dispersant is not limited, such as powder, liquid, and aqueous solution, and can be appropriately selected according to the construction situation.

As a method of injecting the dispersant so as to satisfy the regulation of such an injection method, for example, a dedicated inlet is provided on a face plate of a cutter disk on which a cutter is attached, and an aqueous solution is formed from the inlet. Is injected at a predetermined flow rate so as to have a quantitative ratio described later.

When the dispersant is injected together with water or mud which fills the face, the viscosity of the mud is lowered by the action of the dispersant, and the original purpose of the mud, which is the stability of the face, cannot be achieved. In addition, the effect of suppressing an increase in the shield machine cutter torque becomes small, and the object of the present invention cannot be achieved.

In the method of the present invention, the amount of the dispersing agent to be used is 0.5 parts by weight or more, preferably 1 to 100 parts by weight, per 100 parts by weight of water or muddy water filling the face for stabilizing the face. The ratio is preferably 10 parts by weight.

If the used amount of the dispersing agent is less than 0.5 part by weight, blockage of the discharging liquid in the discharging pipe cannot be avoided, and the effect of the present invention cannot be obtained. On the other hand, even if it is used in an amount exceeding 10 parts by weight, the improvement in the effect reaches a peak and is uneconomical.

[0027]

The present invention will be specifically described below with reference to examples and comparative examples. Examples 1 to 6 In the ground where the soil is silty cohesive soil (water content: 105%), the dispersant described in Table 1 was supplied from a dedicated dispersant injection port provided on the face of the cutter disk to which the cutter was attached. While injecting the amount shown in Table 1 as an aqueous solution adjusted to a concentration of 40% by weight,
Excavated 20m. At this time, the discharging liquid discharged from the shield machine cutter chamber was conveyed to a discharging pipe port by a screw conveyor, and then pumped out by a pump of 500 m through a discharging pipe of φ300 mm and discharged.

Specifications of muddy water pressure shield method ・ Shield body outer diameter: 10000mmφ Total length: 8270mm Shield jack: 250t × 1100st × 300kgcm
² × 33 pieces Thrust per face area: 105 t / m ²

[0029] ・ Cutter Type: Full-section excavation forward / reverse type cutter with ultra-high tip Excavation outer diameter: 9970 mmφ Number of rotations: 0 to 0.57 rpm

Screw Conveyor Screw blade diameter: 552 mmφ Number of rotations: 0 to 30 rpm Muddy water Bentonite is added to tap water, and the specific gravity is adjusted to 1.3 before use. Mud sending amount: 80L / min

Table 1 shows the average values of the cutter torque and the screw torque during construction, the presence or absence of blockage in the discharge pipe, and the time required for construction under each condition.

[0032]

[Table 1]

In Table 1, 1) Symbols described as types of dispersants have the following meanings. HMPNa: Sodium hexametaphosphate PPNa: Sodium polyphosphate SiNa: Sodium silicate KOH: Potassium hydroxide LSNa: Sodium ligninsulfonate MFSNa: Sodium sulfonate melamine formalin condensate 2) Injection amount: Dispersion per 100 parts by weight of muddy water filling the face 3) Cutter torque reduction rate: 100-(Cutter torque value / Same value without dispersant added) x
100 (%) 4) Screw torque reduction rate: 100− (screw torque value / same value when dispersant is not added) × 100 (%). Situation 1 in the column of required construction time indicates "interruption due to blockage in pipe", and Situation 2 indicates "interruption due to loosening of face".

Comparative Examples 1 to 3 As a comparison, except that no dispersant was used (Comparative Example 1), or that the one shown in Table 1 was used instead of sodium hexametaphosphate (Comparative Examples 2 and 3). It was the same as in Example 1. Table 1 shows the results. If the dispersant was not added, the earth removal liquid would cause blockage in the earth removal pipe,
Excavation over a predetermined distance could not be performed continuously.

When components other than those specified in the present invention were added as a dispersant, there was no blockage of the discharging liquid in the discharging pipe, and it was possible to excavate a predetermined distance continuously. The reduction rate of cutter torque is about 2 to 6% and the reduction rate of screw torque is about 5 to 10%.
It took more than a minute.

Comparative Example 4 The procedure of Example 3 was repeated except that the injection amount of the dispersant was changed to the amount shown in Table 1. Table 1 shows the results. Examples 3 to 6 and Comparative Example 4 show the effect of the amount of dispersant used on muddy water. When the amount of the dispersant used was less than 0.5 parts by weight with respect to the muddy water (Comparative Example 4), the cutter torque and the screw torque were reduced, but the discharged liquid clogged in the discharge pipe, and It was not possible to continuously excavate the distance.

Comparative Example 5 Experiments No. 11 to No. 12 show the effect of the dispersant injection method. Instead of injecting the dispersant from the injection port dedicated to the dispersant provided on the face plate of the cutter disk, using a muddy water mud pipe, the construction was performed while sending the liquid together with the muddy water. I did the same. Table 1 shows the results. in this case,
The effect of reducing the cutter torque was small, and the face was loosened during excavation, and the construction was interrupted.

On the other hand, when the type of the dispersant, the injection amount, and the injection method satisfy the requirements of the present invention (Examples 1 to 7).
In this method, both the cutter torque and screw torque were greatly reduced, and there was no blockage of the discharging liquid in the discharging pipe, and the construction could be performed efficiently in a short time. In addition, when the injection amount exceeded 10 parts by weight with respect to the muddy water (Example 10), although the effect of the present invention was obtained, the increase in the effect leveled off.

[0039]

According to the shield method of the present invention, the ground is excavated while pouring water or muddy water into the face face, and the excavated earth and sand is fluid-transported as an earth removal liquid by an earth removal pipe to construct a tunnel. Without damaging the original purpose of muddy water, which is the stability of the face, especially in the case of ground where the construction target ground has a high adhesive strength such as silt layer or clay layer, and the drainage liquid causes blockage in the discharge pipe. In addition, it is possible to suppress a decrease in the cutting efficiency and an increase in the cutter torque, and also to suppress a blockage in the discharge pipe and an increase in the screw conveyor torque, thereby making it possible to excavate the tunnel more safely, reliably and efficiently.

 ──────────────────────────────────────────────────の Continued from the front page (72) Inventor Hideki Kobayashi Nitto Chemical Industry Co., Ltd.

Claims (3)

[Claims] 1. A shield method in which a ground is excavated while filling a face with water or muddy water, and the excavated earth and sand is fluid-conveyed by an earth removal pipe as an earth removal liquid to construct a tunnel. A shield method characterized by excavating the ground while injecting at least one type of component into the vicinity of a cutter. 2. The dispersant is at least one selected from the group consisting of alkali metal salts and alkali metal hydroxides of silicic acid, metasilicic acid, phosphoric acid, polyphosphoric acid and hexametaphosphoric acid. The shield method described. 3. The shielding method according to claim 1, wherein the amount of the dispersant to be injected is 0.5 parts by weight or more per 100 parts by weight of water or muddy water filling the face.