JPS62270681A - Earth pressure shield tunneling - Google Patents

Abstract

PURPOSE:To improve the stabilization of a working face, the fluidity of excavated soil and water stopping in an earth pressure shield tunneling by feeding a high-viscosity gel slurry consisting of a gel material and a gelling agent to an earth pressure chamber to be filled with the excavated soil. CONSTITUTION:A gelling agent is fed to a line mixer 21 by means of a pump P4 and excavated soil discharged from a screw conveyor 5 is fed to a hopper 50 and then pressure-fed on the ground by means of a pump P6. The excavated soil pressure-fed by the pump P6 is received by a reservoir 51 and a degelling agent is added thereto. The mixture is stirred to lower the viscosity of the gel material and the gel material is transferred to a separating tank 14 by a pump P7. A non-defective fluid separated in the tank 14 is returned to a reservoir 11 to reuse it. Examples of the gelling agent are alkaline materials such as sodium hydroxide, slaked lime, etc. The degelling agent to be added after recovery is an acidic material. Examples thereof are aluminum sulfate, aluminum chloride, etc.

Description

[Detailed description of the invention] 3. Detailed description of the invention (Industrial application field) The present invention relates to an earth pressure shield construction method.

(Background of the invention and its problems) The earth pressure shield method involves taking the excavated soil with a cutter disk into the earth pressure chamber and filling it, thereby balancing the earth pressure at the face in front of the cutter disk and reducing the amount of earth excavated in the earth pressure chamber. This is a construction method in which soil is excavated while being mechanically removed.

However, with this type of construction method, when the ground water level is high and the ground has a high permeability coefficient, such as gravel ground, it becomes difficult to ensure the stability and water-tightness of the face due to the excavated soil, and the shielding method becomes difficult. Progress becomes impossible. In addition, there was a problem with the fluidity of soil excavation in gravel ground, and soil removal was also troublesome. .

By the way, the present applicant has previously developed a gelled slurry consisting of a viscous substance dissolved in water and additives such as borax and boric acid.

The viscosity of the gelled mud water varies from centipoise on the alkaline side to centipoise on the acidic side by adjusting the hydrogen ion concentration (pH).
It varies in an extremely wide range from 0 to 50 centimeter voice.

Therefore, when excavating ground with a large amount of sludge, such as a gravel layer, water-stopping properties can be improved by injecting the alkaline side, that is, the highly viscous gelled state created by mixing a gelling agent, into the earth pressure chamber and the front of the face. It is possible to ensure the fluidity of the excavated soil taken into the earth pressure chamber. In addition, this high viscosity gelled mud water is mixed with an acidifying agent, that is, a gelling agent after mixing to lower the viscosity, so that it can be mixed with the excavated earth and sand.
This method has the advantage that the supernatant after separation can be reused.

(Problems to be Solved by the Invention) This invention improves the stability of the face and the fluidity and water-stopping properties of excavated soil in the earth pressure shield method by effectively utilizing the properties of high-viscosity gelled mud. By further improving the quality and reusing the collected muddy water,
The purpose is to reduce the consumption of muddy water itself.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an earth pressure shield that stabilizes the face by filling the earth pressure chamber with excavated soil by a cutter disk. The construction method is characterized in that a high viscosity gelled mud made of a combination of a gelatinous substance and a gelling agent is supplied at least into the earth pressure chamber.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

FIG. 1 is an explanatory diagram showing a high viscosity gelled mud water supply/recovery system according to the present invention.

In the figure, reference numeral 1 denotes a closed type upper pressure shield tunneling machine, and an earth pressure chamber 3 partitioned by an rfA wall 2 is formed in the front part of the tunneling machine 1, and a cutter disk 4 is formed in the front of the earth pressure chamber 3.
is provided. A screw conveyor 5 passing through the partition wall 2 is provided at the bottom of the earth pressure chamber 3.

A mud feeding pipe 6 is provided to penetrate the upper part of the partition wall 2. A part of the mud feeding pipe 6 is connected to the cutter disk 4.
It is branched and connected to a communication hole 7 formed in the central axis 4a of the. A plurality of flow holes 7 are opened at appropriate front positions of the cutter disk 4, and muddy water is spouted toward the face surface.

A mud water supply line 8 is connected to the mud feeding pipe 6.

This mud water supply pipe 8 is connected to a mud production plant 10 provided on or in contact with a starting shaft located at the rear of the shield shaft 9.

Inside the mud production plant 10, a storage tank 111, a recovery tank 129, and a separation tank 14 are arranged.

A stirring tank 15 is arranged above the storage tank 11.

The above-mentioned viscous substance, water and preservative are uniformly mixed in this stirring tank 15, and the mixed gel-like substance is transferred to the storage tank 15.
1 and stored here.

The mud water supply line 8 is connected to the discharge end of this storage tank 11, and is sent to the mud feeding pipe 6 side by a pressure pump P1 provided in the line 8.

A gelling agent supply line 16 is connected to the supply line 8 at a position immediately before connection to the mud feeding pipe 6 . A funnel-shaped liquid tank 18 and a valve 20 are provided above the supply line 16.

By opening the valve 20, the gelling agent stored in the liquid Wg18 is added to the muddy water supply line 8 and merges with the gelled material transported therein.

The merged gel-like substances are sufficiently mixed by passing through the line mixer 21 provided at the leading edge position, and in this state are discharged to the mud feeding pipe 6 side, and discharged into the earth pressure chamber 3 and the front of the cutter disk 4. will be done.

Further, the discharge end of the screw conveyor 5 is located opposite to the supply end of the line mixer 22 for recovery.

A liquid tank 23 for a degelling agent is connected above the line mixer 22 via a valve 24 . A discharge end of the line mixer 22 communicates with the separation tank 14 through a recovery line 26.

A pump P2 is interposed in the recovery line 26, and the discharged mixture of excavated soil and gel material discharged from the screw conveyor 5 is recovered into the separation tank 14 through the line mixer 22 by the pump P2.

By adding the degelling agent stored in the liquid tank 23 into the line mixer 22, the gel-like substance component in the mixture is degelled, and the viscosity is reduced to a level suitable for fluid transport. Separated along with excavated soil through recovery line 26+
f! It is discharged to the 14 side.

Separation based on the difference in specific gravity or classification using a sieve is performed in the separation tank 14, and the gel-like substance that has returned to its original state is recovered into the recovery tank 12 via the pump P3.

Further, the excavated soil that is the residue is discharged from the bottom of the separation tank 14 to the outside through a hopper or the like. Since the gel-like substance is harmless, the excavated earth does not need any special treatment and can be used as a landfill.

Further, a merging line 28 is provided at the discharge end of the recovery tank 12 and merges with the muddy water supply line 8 .

The gel-like substance recovered by the pump P4 provided in the confluence line 28 is again circulated and supplied to the earth pressure chamber 3 and the cutter disk 4 through the muddy water supply line 8.

The viscous substance used in the above system is a vegetable viscous substance such as guar gum or roasted gum, either alone or in combination, and when dissolved in water, it becomes a gel-like liquid. This gel-like substance is made even more viscous by the alkalizing agent, and the viscosity is increased to a centimeter high. Gelling agents are specifically alkaline substances such as sodium hydroxide, slaked lime, and sodium carbonate. The degelling agent added after recovery is an acidic substance, such as sulfuric acid chloride, aluminum chloride, dilute sulfuric acid.

Dilute hydrochloric acid etc. are used.

Therefore, the gel-like substances stored in the storage tank 11 and the recovery tank 12 are neutral to weakly acidic, and are stored in a degelled state. Thereby, even if the distance between the mud production plant 10 and the shield excavation 111 is long and the length of the mud water supply inlet 8 is long, sufficient mud can be fed. Since the gelling agent described above is added and mixed immediately before supply to the shield excavation fi1, the gelatinizer is added and mixed in a highly viscous state through the relatively short distance mud feeding pipe 6 into the earth pressure chamber 3 and in front of the cutter disk 4. You will have to spit it out. The highly viscous gelled mud discharged onto the front surface of the cutter disk 4 becomes like a film and mixes with the excavated soil while facing the face surface and is taken into the earth pressure chamber 3. Therefore, sufficient water-stopping properties can be obtained even in permeable gravel ground.

The excavated soil and high-viscosity gelled mud water scraped off by the cutter disk 4 are mixed by a stirring blade (not shown) in the earth pressure chamber 3, and are further mixed with the high-viscosity gelled mud water supplied therein. While combining with the excavated soil taken and filled in the earth pressure chamber 3 to counter the face earth pressure, the fluidity of the excavated soil is ensured by the high viscosity gelled muddy water filled between the excavated soil.

When the earth pressure in the earth pressure chamber 3 increases, the screw conveyor 5
It is supplied into the recovery line mixer 22 through the line mixer 22.

Then, by mixing with the degelling agent in the line mixer 22, the high viscosity gelled mud in the mixture is degelled and reduced in viscosity. However, even in this state, the function as a fluid medium for excavated soil does not change, so the fluid can be transported to the mud production plant 10 side through the recovery line 6.

In order to control the viscosity of the high-viscosity gelled mud, a viscosity sensor is provided at the tip of the mud water supply tube 8, and the accuracy of the valve attached to the liquid tank 18 is feedback-controlled according to the detection output of this viscosity sensor. By shifting, the viscosity can be controlled with high accuracy.

Further, on the recovery side, the viscosity can be similarly lowered to a level suitable for transportation by feedback control.

FIG. 2 shows a second embodiment of the earth pressure shield construction method according to the present invention, and only its characteristic points will be explained below.

In the embodiment shown in the figure, the gelling agent is supplied to the line mixer 21 by a pump P5, and after the excavated soil discharged from the screw conveyor 5 is once received by a hopper 50, it is pumped to the ground by a pump P6.

The excavated soil pumped by pump P6 is stored in a storage tank 51, a gel-resolving agent is added thereto, the viscosity of the gel-like substance is lowered by stirring, and the excavated soil is transferred to the separation tank 14 by pump P7. The good liquid separated in step 14 is returned to the storage tank 11 by pump P3 for reuse.

FIG. 3 shows a third embodiment of the invention.

In the figure, the earth excavation and high viscosity gelled mud supply system is the same as that of the first embodiment, but the recovery system is such that the transport vehicle 30 running on the rails provided in the shield pit 9 is connected to the screw conveyor 30. The mixture collected by the trolley 30 is sent to the mud production plant 10 via a packet or the like, and a degelling agent is introduced into the separation tank 14 through the liquid tank 31, and the soil is excavated. and the gel-like substance are separated.

This embodiment is particularly suitable for cases where the excavated soil has a large slag component and is unsuitable for fluid transportation through a recovery line.

(Effects of the Invention) As explained in detail in each of the embodiments above, in this invention, high viscosity gelled mud is mixed with excavated soil by supplying it at least within the earth pressure, and water stoppage performance is greatly improved. , and generates an earth pressure that can sufficiently resist the face earth pressure. Further, in the present invention, sufficient fluidity with the excavated soil can be ensured due to the effect of the gelled mud as a binder.

Furthermore, with this invention, it is possible to separate the mixture of recovered excavated earth and mud water, and the gel-like material after separation can be repeatedly fed into the supply line, resulting in less consumption and cost savings. can.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram, not showing a high viscosity muddy water supply/recovery system according to a first embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a high viscosity gelled muddy water supply/recovery system according to a second embodiment. FIG. 3 is an explanatory diagram of the third embodiment. 1......Shield excavator 3...Earth pressure chamber 4...Cutter disc 6...
...Mud feed pipe 8...Mud water supply line 9...Shield pit 10...
...Mud production plant 11...Storage tank

Claims (1)

[Claims] (1) In the earth pressure shield construction method, which stabilizes the face by filling the earth pressure chamber with excavated soil with a cutter disk, at least a combination of a gel-like substance and a gelling agent is added to the earth pressure chamber. This earth pressure shield construction method is characterized by supplying high viscosity gelled mud water.