JPH0296093A - Discharging method for shield excavation earth - Google Patents

Abstract

PURPOSE:To prevent jetting and closing from being generated in a screw conveyor by injection-feeding compressed air, into the screw conveyor for conveying earth excavated with a cutter, in a shield chamber. CONSTITUTION:Earth excavated with a cutter 14 set in front of a shield main- body 10 and taken in a shield chamber 12 is discharged by a screw conveyor 16. The conveyor 16 is connected to a compressor 22 with a piping 24 via a check valve 36, a discharge rate regulating valve 34, an air chamber 32, a pressure-reducing valve 26, and the like. Then, internal pressure in the shield chamber 12 is set as a maximum, and compressed air is injection-fed to the conveyor 16. As a result, an earth jetting accident from the side of the earth discharging port of the conveyor 16 is prevented from being generated, and work can be smoothly executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for removing earth and sand from shield excavation, and in particular, a method that prevents earth and sand excavated by the earth pressure shield method from blowing out or clogging through a screw conveyor, earth discharge pipe, etc. This invention relates to a method for removing earth and sand from shield excavation.

[Conventional technology]

When excavating stagnant ground or high-pressure gravel ground using the mechanical shield method, the face becomes unstable due to groundwater supplied by pore water pressure at the face, causing problems in earth removal. A conventional auxiliary method for this purpose is the well-known pressurized air construction method, in which a bulkhead is installed in the mine, pressurized air is sent into the mine in the section from the face to the bulkhead, and air pressure corresponding to the water pressure acting on the face is applied to the face. The face is stabilized by applying pressure. However, since this is the entire pressure inside the mine, it poses a problem for work, and a limited pressure method is also used to pressurize the inside of the shield chamber. In addition, with earth pressure shielding for the above ground, water-stopping soil such as silt or clay is injected into the shield chamber as an additive to give the excavated soil plastic fluidity and continuously remove soil while maintaining water-stopping properties. I try to do that.

[Problem to be solved by the invention]

However, among the conventional construction methods mentioned above, the limited pressure air construction method actively injects pressurized air into the shield chamber.
Air leaks into the ground through the gaps in the face, creating air passages in the ground, which become so-called waterways. This channel, on the other hand, became a channel for water to actively enter the face, causing the problem of triggering an eruption.

In addition, in the earth pressure shield method, during shield excavation, the soil becomes high in water content or liquefies due to the viscosity imparting material injected to give plastic fluidity to the ground, resulting in shear resistance of the soil due to consolidation. In some cases, it may not be possible to ensure safety, and there is a problem in that it is not possible to effectively prevent explosion accidents. In addition, to prevent eruptions, we are removing soil while increasing the degree of soil filling inside the screw conveyor.
When the amount of silt and clay bones in the excavated soil increases, the screw conveyor may become clogged with the soil, making it impossible to discharge the soil.

The present invention focuses on the above-mentioned conventional problems, and eliminates the risk of channel formation due to the pressure of the shield chamber, eliminates the risk of liquefaction of excavated soil, and solves the problem of soil and sand clogging in the screw conveyor. The object of the present invention is to provide an earth removal method for the shield construction method that can obtain extremely high blowout prevention effects and blockage prevention effects.

[Means for Solving the Problems] In order to achieve the above object, a shield excavated soil discharge method according to the present invention includes a method for discharging excavated soil from inside a shield chamber using a screw conveyor. It was configured to inject and supply compressed air into the tank.

[Effect]

During shield excavation work, the excavated earth and sand is discharged backwards by a screw conveyor, but the pressure distribution of the screw conveyor at this time is high pressure at the end on the shield chamber side, which is equivalent to the internal pressure of the shield chamber.
Since the soil discharge port is opened to the atmosphere, it is desirable that the gauge pressure be zero.

Ideally, this pressure distribution decreases from the entrance to the exit of the screw conveyor. However, when observing the pressure distribution when an eruption occurs, it is found that the pressure distribution of the screw conveyor fluctuates during the soil removal process and does not decrease at a negative slope, but instead increases toward the soil discharge port. As a result, the pressure inside the conveyor increases throughout the entire conveyor, causing it to erupt all at once. In this case, it is observed that the soil inside the screw conveyor is not consolidated, but is in a densely packed state. During this process, the soil discharge rate of the screw conveyor gradually decreases, and liquid material enters the rough areas, causing the internal pressure of the screw conveyor to rise due to water pressure, and the soil erupts within a few seconds.

Therefore, in the present invention, as described above, compressed air is supplied into the screw conveyor during soil removal, so that
Even if the earth and sand are in a dense state in the screw conveyor, compressed air enters the gaps, and the air pressure prevents water from entering from the shield chamber side, reducing the water content ratio of the transported earth and sand. Moreover, the compressed air acts on the earth and sand in the screw conveyor to promote compaction, and acts to ensure shear resistance of the earth and sand due to this compaction.

As a result, the soil removal action by the screw conveyor is performed smoothly, and the intrusion of water that promotes eruption can be effectively prevented. In addition, on the downstream side of the compressed air injection position, the internal earth and sand are compacted, which promotes soil removal, and thereby prevents clogging of the screw conveyor.

Note that the supply pressure of the compressed air may be set to the maximum internal pressure of the shield chamber.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the shield excavation soil removal method according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 and FIG. 2 are a block diagram of a shield excavation apparatus including a screw conveyor to which a shield excavation earth and sand discharge method according to an embodiment is applied, and an overall block diagram of shield equipment. As shown in these figures, the shield machine has a shield chamber 12 formed at the front end of a shield body 10, and is configured to take excavated earth and sand into the shield chamber 12 while excavating the ground using a cutter 14 at the front end.

The tip of a screw conveyor 16 for discharging excavated soil backward is inserted into the shield chamber 12 from the partition wall of the shield chamber 12 . The screw conveyor 16 is arranged with a certain slope from the bottom of the shield chamber 12, and is configured to transport the taken-in earth and sand to the rear of the mine shaft by driving a screw drive motor 18 attached to the rear end of the screw conveyor 16. It has become. A rotary valve 20 is connected to the soil discharge port of the screw conveyor 16, and the screw conveyor 1
The interior of 6 is partitioned to allow continuous soil removal. In this embodiment, the rotary valve 20 is installed at the soil discharge port, but this may be connected continuously to a screw conveyor or to a soil discharge pipe. When an earth removal pipe is connected, compressed air is supplied to perform forced earth removal in the same manner as in the case of the screw conveyor 16, and a higher blockage prevention effect can be obtained.

Here, the screw conveyor 16 for discharging earth and sand from the shield chamber 12 is connected at an intermediate position to a means for injecting and supplying compressed air into the screw conveyor 16 . As shown in the figure, a compressor 22 installed on the ground is used as a supply source of compressed air.
It is designed to lead to 6. In the middle of the air piping 24, compressed air whose pressure is reduced through a pressure reducing valve 26, an automatic valve 28, and a check valve 3o is temporarily supplied to an air chamber 32, and the air chamber 32 controls the flow rate while preventing pulsation. Compressed air is injected into the screw conveyor 16 via a regulating valve 34 and a check valve 36 provided with a filter cloth to prevent backflow of earth and sand. In addition, the pressure reducing valve 26
An air gauge 38 is installed between the check valve 30 on the outlet side of the air chamber 32 and the air chamber 32 to detect the air supply pressure. Further, a polymer absorbent can be supplied to the screw conveyor 16 in case the earth and sand taken in from the shield chamber 12 has a high water content and becomes liquefied. For this reason, the screw conveyor 16
A check valve 46 is connected to the dirt intake section on the tip side of the screw conveyor 16 through a pipe 44 via a polymer absorbent container 40 and a pressure pump 42 connected thereto.
It is configured to be injected through the

The viscosity-imparting material is injected and supplied from the cutter head at the front end of the shield body 10. For this purpose, the viscosity-imparting material is prepared by the mud-making mixer 48 on the ground equipment, and then pumped and supplied by the pump 50. There is. This plastically fluidizes the excavated soil, making it possible to continuously discharge the soil while maintaining water-tight properties.

A method for removing earth and sand from shield excavation using the equipment configured as described above is performed as follows.

When shield excavating water-logged ground or high-pressure gravel ground, water pressure acts on the cutter head of the shield machine, and when the diameter of the shield body 10 is about 3 m, for example, a water pressure of 3 kgf/crM acts on the upper end of the cutter head. , 3 on the bottom edge. Water pressure of 3kgf/c+fl acts.

A viscosity imparting material is injected and filled into the earth and sand, and the earth and sand is plastically fluidized and introduced into the shield chamber 12. The earth and sand taken into the shield chamber 12 by such shield excavation is agitated by a cutter or the like and discharged from the chamber partition wall to the rear of the mine by the screw conveyor 16. During soil removal by the screw conveyor 16, the internal pressure distribution is approximately equal to the internal pressure of the shield chamber 12 at the inlet of the screw conveyor 16.
The gauge pressure is approximately kgf/crfl, and it is desirable that the pressure be atmospheric at the soil discharge port. However, if the transported soil has a high moisture content and is liquefied, the soil within the screw conveyor 16 will be in a coarse and dense state.
In this embodiment, compressed air is injected and supplied from the middle of the screw conveyor 16 to eliminate the cause of the blowout.

That is, in the embodiment, the compressor 22
Generates compressed air with a pressure of f/cf and connects the air pipe 24
0 to 4 kgf/c+f by the pressure reducing valve 26 installed in the middle of
The pressure is reduced to 1 and stored in the air chamber 32, and the pulsation is suppressed in the air chamber 32, and the screw conveyor 16
It is injected into the body. The supply pressure of this compressed air is set to correspond to the pressure distribution originally required for the screw conveyor 16, and therefore the compressed air inlet is set at a position corresponding to the pressure distribution of 2 kgf/aa. If so, that 2kgf/cif
1 pressure is managed and supplied as the set pressure.

This can be easily dealt with by adjusting the settings of the pressure reducing valve 26. When the pressure inside the ground or the shield chamber 12 changes, the corresponding pressure may be determined from the set pressure distribution, and the set value of the pressure reducing valve 26 may be adjusted while checking with the air gauge 38. Furthermore, depending on the condition of the earth and sand discharged from the earth discharge port, a polymer absorbent is injected into the screw conveyor 16 as necessary to prevent the earth and sand from becoming liquefied, which could lead to a blowout accident. , to more reliably improve the eruption prevention effect.

The operation of this shield excavation soil removal method is as follows. When compressed air is supplied into the screw conveyor 16 during earth removal by the screw conveyor 16, the free water of the soil with a high water content is removed by the pressurizing action, and the water content inside the screw conveyor 16 is improved.

Then, the compressed air acts on the rear half side of the screw conveyor 16, which is the low-pressure side of the screw conveyor 16, thereby consolidating the internal earth and sand. Thereby, shear resistance between the earth and sand and the screw conveyor 16 can be ensured, and the soil removal efficiency by the screw conveyor 16 can be improved. That is, since the pressure distribution inside the screw conveyor 16 is adjusted to a normal state by the action of compressed air, the soil removal action is performed smoothly and at the same time the dewatering action is performed.
The water-stopping action on the face side produces a so-called retaining effect, which effectively prevents blowout accidents. In addition, the compressed air promotes soil removal due to the compaction effect on the earth and sand within the screw conveyor, so that clogging of the screw conveyor can be effectively prevented.

Incidentally, in the above embodiment, compressed air is injected at a pressure corresponding to the set pressure distribution of the screw conveyor 16, and depending on the internal pressure of the screw conveyor 16, the injection of compressed air may be stopped. On the other hand, compressed air may be continuously injected regardless of the set pressure distribution. Air is screw conveyor 1
This is because it has the function of suppressing liquefaction of soil even if it is discharged to the soil discharge port side of 6, and does not have an adverse effect on the mechanical soil discharge action by the screw conveyor 16. That is, even if high-pressure air leaks from the soil discharge port, it does not act as a pressure for ejecting the soil and is exhausted independently of the soil. In particular, there is an advantage in that the compaction effect on the earth and sand in the conveyor is enhanced, and the effect of improving shear resistance is improved. Of course, if the pressure is higher than the pressure on the shield chamber 12 side, there is a risk of water path formation in the ground on the face side, so the limit pressure is set on the shield chamber 1.
The internal pressure is 2.

〔Effect of the invention〕

As explained above, according to the present invention, compressed air is injected into the screw conveyor during soil discharge by the screw conveyor, thereby preventing the occurrence of sediment eruption accidents from the soil discharge port side of the screw conveyor. can,
At the same time, the soil removal efficiency can be improved, and excellent effects such as dehydration and heap retention can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a screw conveyor to which the shield excavation earth and sand discharge method according to the embodiment is applied, and FIG. 2 is a block diagram of the entire shield equipment applied to the embodiment. 10... Shield body, 12... Shield chamber, 16... Screw conveyor,
22...Compressor, 26...Reducing valve, 32...Air chamber.

Claims (1)

[Claims] (1) A method for discharging excavated soil from inside a shield machine chamber using a screw conveyor, the method comprising injecting and supplying compressed air into the screw conveyor.