JPH0542560B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an earth pressure shield excavation method using slurry.

[Conventional technology]

In shield excavation work in geological strata rich in groundwater, there are problems such as the face collapsing easily due to water outflow, so a mud shield excavation method is used in which the face is excavated while injecting slurry. . Sludge here refers to an additive material whose main components are bentonite and clay, and which do not contain sand as its main component. Generally, a slurry based on bentonite and clay, or a slurry based on clay is used.

This slurry shield excavation method involves excavating a face while injecting slurry with a cutter portion of a slurry shield excavation machine, and filling an earth pressure chamber at the rear surface of the cutter portion with earth and sand from this excavation, that is, a mixture of excavation sludge and the injected slurry. While stirring, it is further stirred by an internally rotating scraping plate to form ready-mixed concrete, and the mixed excavation shear filled in this earth pressure chamber generates earth pressure against the face of the tunnel, suppressing earth pressure at the face and groundwater pressure. While continuing to excavate the face, the mixed excavation sludge in the earth pressure chamber is discharged while being stirred from the rear outside of the slurry shield excavator by the discharge means while maintaining its full state, and the discharged mixed excavation sludge is transferred to the belt conveyor. It is carried out outside the mine using transportation means such as

Another construction method is a bubble shield excavation method in which excavation is carried out while injecting shaving cream-like bubbles into the face instead of the slurry. This bubble shield excavation method is widely used because it prevents excavation debris from adhering to clayey soil and improves fluidity in sandy to gravelly soil.

[Problem that the invention seeks to solve]

However, when the slurry shield excavation method is applied to excavation of ground containing cobblestones, etc. with abundant groundwater, the ground has a large gap due to the cobblestones, and the proportion of sand contained is low. For,
By simply injecting the slurry, the mixed excavated waste could not satisfy the conditions for becoming ready-mixed concrete in terms of composition, and therefore it was difficult to improve it into ready-mixed concrete. Therefore, there was a problem in that it was not possible to continue face excavation while suppressing the face earth pressure and groundwater pressure by generating earth pressure against the face due to mixed excavation shear.

Therefore, conventionally, for the ground containing cobblestones, etc., sand-containing slurry was created by adding sand to the slurry in order to compensate for the lack of sand content and satisfy the conditions for the mixed excavation debris to become ready-mixed concrete in terms of composition. That is, a method of injecting mortar slurry has been proposed.

However, during actual construction, sand settles and separates from the mortar slurry during transportation.
It was extremely difficult to get the sand to reach the face. Of course, if a large amount of mortar slurry is injected in anticipation of the reduction in sand separation, the state of ready-mixed concrete can be improved to some extent, but such construction will result in a large amount of slurry being mixed into the excavated slag that is ultimately carried out of the mine. Therefore, from the standpoint of pollution prevention, post-treatment to reduce the amount of slurry mixed in is time-consuming and impractical.

In addition, when the bubble shield excavation method is applied to excavation in ground that contains cobbles, etc., which are rich in groundwater, the gap between the ground becomes large due to the cobbles in the ground, so air bubbles alone will not be enough to reduce the amount of excavation. It was difficult to improve the fluidity of the concrete and it was not possible to make it into a ready-mixed concrete state. Furthermore, due to the presence of a large amount of groundwater between large soil particles such as cobblestones, the injected air bubbles cannot fully penetrate between the soil particles of the face and are washed away, making it virtually impossible to inject the air bubbles into the face. There was a problem in that it was not possible to reduce the load that the cutter part of the shield tunneling machine received from the face, and that the excavation was interrupted and stopped. In other words, stable excavation of such ground could not be maintained using the bubble shield excavation method.

The purpose of the present invention is to be able to reliably reduce the load that the cutter part of the slurry shield excavator receives from the face surface even in the ground to be excavated, which includes cobblestones rich in groundwater, and further to ensure mixed excavation shear. Earth pressure using slurry that can be made into a ready-mixed concrete form, and can continue excavation at the face while suppressing the face earth pressure and groundwater pressure by generating anti-earth pressure against the face by mixed excavation shear. To provide a system shield digging method.

[Means and effects for solving problems]

The present invention is characterized in that the ground to be excavated is a stratum containing cobblestones rich in groundwater, a predetermined amount of air bubbles is mixed in the slurry injected therein, and the discharge means is a ribbon screw. It is.

According to the present invention, since the slurry mixed with air bubbles is directly injected into the face, even if the ground to be excavated is a stratum containing cobbles etc. with abundant groundwater, the spaces between large soil particles such as cobbles etc. Second, the existing groundwater is pushed away, and the slurry and air bubbles permeate together without being separated, which reliably reduces the load that the cutter part receives from the face surface, making stable excavation possible.

The mixed excavated sludge produced by drilling while injecting the aerated slurry into the face has a low sand content, but the lack of sand is compensated for by the air bubbles, so the mixed sludge has a compositional composition of It meets the conditions for becoming ready-mixed concrete. Therefore, this mixed excavated waste is reliably reformed into ready-mixed concrete, and it is possible to stably continue face excavation while generating earth pressure against the face and suppressing the face earth pressure and groundwater pressure. . Here, to explain the role of air bubbles, air bubbles play the role of connecting gravel and fine grains in the ground, and thus play a role similar to that of sand, which is necessary to form ready-mixed concrete. The amount of air bubbles mixed into the slurry is an amount that can maintain the earth pressure against the mine and turn the mixed excavated waste mixed into the slurry into a ready-mixed concrete having fluidity that is discharged by the ribbon screw.

In addition, the amount of slurry injected is reduced by the volume of air bubbles mixed into the slurry, which reduces the amount of slurry mixed into the final drilling shear. Since the water is compensated by water, it is possible to prevent the fluidity and water-stopping properties of excavated slag from decreasing.

In addition, since a ribbon screw is used as the discharge means, it is possible to smoothly discharge excavated debris including large boulders, and a sand plug zone is formed at the discharge port, which can be filled with mixed excavated debris. Anti-earth pressure is generated. There is also a slide gate, which also generates earth pressure against the mine.

In this way, by injecting air bubbles together with the slurry, the excavated slag can be easily improved into a ready-mixed concrete-like material with excellent fluidity and water-stopping properties, making it possible to generate sufficient anti-earth pressure in the earth pressure chamber. This prevents the collapse of the face and enables stable excavation.
It is now possible to carry out construction even in ground that contains abundant underground water, such as cobblestones, where stable excavation has been difficult until now.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in the order of steps.

The ground to be excavated is ground containing boulders, etc. with abundant groundwater, and the cutter part of the slurry shield excavator excavates the face while injecting slurry mixed with air bubbles. The mixing of air bubbles is carried out by mixing dense air bubbles created by foaming a foaming agent into the slurry before it is injected into the face. That is, the slurry mixed with air bubbles is directly injected into the face. Note that these bubbles were pressurized to prevent them from disappearing due to face earth pressure and groundwater pressure. As the type of foaming agent, a protein-based foaming agent, a surfactant, etc. are used. It goes without saying that air bubbles may be mixed into the slurry by other methods.

The amount of air bubbles mixed in the slurry will vary depending on the ground condition, but if it is adjusted based on the volume ratio of (sludge): (air bubbles) = 1:1, reformation into the ready-mixed concrete can be achieved. I can do it. If the ground has a lot of groundwater, it is better to adjust the proportion of air bubbles, and if the ground has a lot of cobblestones, it is better to adjust the proportion of mud to a higher proportion. This allows air bubbles to penetrate between the particles of the face together with the slurry, reducing the load that the cutter part receives from the face surface.

The soil excavated from the face, that is, the excavated sludge mixed with the injected slurry, satisfies the conditions for becoming like ready-mixed concrete in terms of its composition.
This mixed excavation slag is filled into the earth pressure chamber and mixed and stirred. As a result, the cobblestone-containing excavated sludge, slurry, and further air bubbles are sufficiently mixed to form mixed excavated sludge similar to ready-mixed concrete. The mixed excavation debris in the form of ready-mixed concrete created in this way fills the earth pressure chamber, generating earth pressure against the shaft, suppressing the face earth pressure and groundwater pressure, and excavation continues stably in this state. .

This mixed excavation slurry has a reduced mixing ratio of slurry, but because air bubbles are mixed in accordingly,
The fluidity and water-stopping properties of the mixing and stirring shear do not decrease. The figure shows the fluidity of mixed drilling sludge when only slurry is injected, and the fluidity of mixed drilling swarf when slurry mixed with air bubbles is injected at a volume ratio of 1:1. From this figure, it can be seen that even if the amount of slurry itself decreases by incorporating air bubbles, the fluidity does not decrease. It can be seen that in a small injection amount range (35% or less), the fluidity of the mixed drilling slurry is improved by the slurry mixed with air bubbles.
Therefore, by using the slurry mixed with air bubbles, it is possible to reduce the amount of slurry mixed into the mixed drilling slag without reducing the fluidity and water-stopping properties of the mixed drilling slag.

The mixed excavated debris in the earth pressure chamber is discharged to the rear of the slurry shield excavator by the ribbon screw while maintaining its full state. At this time, since the fluidity and water-stopping properties of the mixed excavation sludge have not decreased, the mixed excavation swarf can be discharged in a stable state while maintaining the earth pressure generated in the earth pressure chamber constant. The mixed excavated waste thus discharged is carried out of the mine by means of conveyance such as a belt conveyor. Since the amount of slurry mixed in the final mixed excavation slurry is reduced by the amount of air bubbles as described above, post-treatment to reduce the amount of mixed slurry is facilitated from the standpoint of pollution prevention.

〔Effect of the invention〕

According to the present invention, since the slurry mixed with air bubbles is used, even if the ground to be excavated is a stratum containing cobblestones, it can be easily improved into ready-mixed concrete, and the air bubbles allow the cutter part to form a face. The load received from the surface can be reduced, which allows stable excavation to continue. In addition, the amount of slurry injected is reduced by the amount of air bubbles mixed in, and the amount of slurry mixed into the final excavation is reduced, making it easier to post-process to reduce the amount of slurry that is discarded from the perspective of pollution prevention. becomes. Furthermore, even if the amount of slurry injected is reduced, it is compensated for by air bubbles, so the fluidity and water-stopping properties of the excavation slag do not deteriorate, and the excavation work can be carried out in a stable state.

[Brief explanation of the drawing]

The figure shows the fluidity of mixed drilling slurry when only slurry is injected and the same fluidity when aerated slurry is injected.

Claims (1)

[Scope of Claims] 1. Excavation is carried out while injecting slurry into the face using the cutter part of the slurry shield excavator, and the earth pressure chamber on the rear surface of the cutter part is filled with the excavated slurry and the injected slurry, and mixed and stirred. The filled mixed excavation shear generates earth pressure against the tunnel face and continues excavation while suppressing the face earth pressure and groundwater pressure, and the mixed excavation shear in the earth pressure chamber is kept filled with slurry by the discharge means. In an earth pressure type shield excavation method using slurry, in which slurry is discharged to the rear of the shield excavation machine and the discharged mixed excavation slurry is carried out of the mine by a conveyance means, the face, which is the ground to be excavated, is rich in groundwater. The discharge means is a ribbon screw, and the slurry contains air bubbles, and the amount of air bubbles mixed in the slurry is determined by the cobblestone-containing mixed excavation mixed with the slurry. An earth pressure system shield excavation method using mud, characterized in that the amount of shear is sufficient to maintain the earth pressure against the mine and turn it into a ready-mixed concrete state having fluidity that is discharged by the ribbon screw.