JPH0243874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a muddy water shield construction method, and more particularly to a face pressure maintaining method in a muddy water shield construction method that prevents fluctuations in face pressure and can always maintain the pressure on the face constant.

The mud shield method is used when excavating sandy or gravelly ground. Due to the nature of the ground, it is important to keep the pressure on the face constant at all times in order to prevent ground collapse and subsidence. This is the most important condition.

However, conventional construction methods have had problems in keeping the pressure on the face constant at all times.

In other words, with the excavators used in the conventional construction method, the mud pipe that supplies mud water was constructed as a double pipe called a telescopic pipe near the excavator, and this was extended as the excavation was carried out. Once the pipe was stretched, the excavator could no longer move forward, so mud feeding was temporarily suspended and new pipe material was added to continue digging.

Therefore, during this replenishment work, the pressure on the face naturally decreased, and there was an extremely high risk that the ground would collapse and subside.

In addition, in this type of construction method, the bentonite is usually separated from the bentonite after excavation, and the bentonite is reused. was.

Therefore, if excavation work is stopped for a long period of time, the muddy water within the face surface will penetrate into the ground over time and cause a decrease in pressure, and if the muddy water is mixed with earth and sand, the sedimentation rate will be faster than with good quality muddy water. This will further promote a pressure drop and increase the risk of ground collapse.Also, long-term suspension will cause bentonite to precipitate and accumulate in the mud pipe, which must be removed when excavation is resumed. It took a lot of time and effort to restart work.

For such problems, for example,
Publication No. 61853 discloses a technique in which a mud feeding pipe for pressure adjustment is provided separately from the existing mud feeding and mud draining pipes.

However, in the technology shown in this publication, a small-capacity variable discharge pump is installed in the mud pipe,
Since this pump is controlled according to the size of the pressure detector, if there are multiple faces, these must be installed individually, which complicates the configuration and requires entry into the tunnel to confirm operation. As a result, handling has become complicated.

This invention was made in view of the above-mentioned problems, and its purpose is to provide a relatively simple structure that can be used when the pressure on the face decreases, such as when excavation work is interrupted or stopped. Therefore, it is an object of the present invention to provide a method for maintaining face pressure in a muddy water shield construction method that prevents collapse and subsidence of the ground by effectively and reliably preventing this.

In order to achieve the above object, the present invention provides a mud water shield construction method in which excavation is carried out while supplying mud water containing bentonite to the face, and after that, the turbidity of the mud water and excavated soil is discharged to excavate a shaft such as a tunnel. A mud feeding device is installed on the ground and includes a plurality of extensible mud feeding pipes for regulating face pressure, one end of which has a bypass pipe for regulating pressure, and the other end communicating with the face surface, Interruption/stopping of excavation work by connecting a mud feeding pipe for pressure adjustment to the face surface, filling the bypass pipe with muddy water, and constantly sending muddy water at a constant pressure to the mud feeding pipe for regulating face pressure. The pressure on the face is sometimes maintained at a predetermined pressure.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

The figure shows an embodiment of a face pressure maintaining method in the muddy water shield construction method according to the present invention.

The method of maintaining pressure at the face shown in the same figure involves pumping muddy water containing bentonite stored in a tank or the like onto the face of the face.
Existing sludge pipe 14 that supplies sludge to 2 via a pump, etc.
and a mud discharge pipe 18 for discharging the muddy soil and muddy water excavated by a mud water shield excavator 16, and the so-called mud water shield construction method in which the excavator is driven while supplying mud water to excavate a shaft such as a tunnel. This shows the case where it is applied to.

The method shown in the figure has the following characteristics.

That is, in the method shown in the figure, a mud feeding pipe 20 for adjusting the face pressure is provided separately from the existing mud feeding pipe 14, and a mud feeding device equipped with this mud feeding pipe 20 is as follows:
It is installed on the ground.

The mud feeding device includes a tank 24 storing good quality muddy water 10, that is, muddy water 10 mixed with new bentonite that does not contain any recovered bentonite;
It has a first mud feeding valve 26 and a sand pump 28, and the output side of this sand pump 28 is branched into two branches, one of which returns to the tank 24 via a pressure adjustment valve 30. One end is a bypass pipe 32 for pressure adjustment, and the other end is a pressure tank 38 equipped with an air bleed valve 34 and a pressure gauge 36.

In this embodiment, the pressure tank 38 is provided with a pair of second mud feeding valves 40, each of which is connected to a pressure regulating mud feeding pipe 20.

The other end of the pressure regulating slurry pipe 20 is a telescopic pipe or flexible tube used in the conventional construction method.
It is disposed near the excavator 16, is extendable, and communicates with different face surfaces 12, respectively.

In addition, in the figure, 42 indicates a water injection valve, and 44 indicates a pressure confirmation gauge.

In the above configuration, for example, interruption of excavation work,
When stopping, first stop the excavator 16 and open the existing mud pipe 14.
After closing the valve of the sludge drain pipe 18, the pressure is checked using the pressure confirmation gauge 44, and the sludge feeding valve 42 is opened and closed in accordance with the decrease in the supporting pressure of the pressure gauge 46 directly connected to the face 12. , the pressure on the face 12 is adjusted to be constant.

At this time, since a bypass pipe 32 is provided at one end of the mud feeding pipe 20 for adjusting the face pressure, which is provided separately from the existing mud feeding and mud removal pipes 14 and 18, the mud feeding pipe 20 always has a constant pressure. Mud water 10 at a constant pressure can be sent out through the mud pipe 2.
0, the other end of the mud feeding pipe 20 is in communication with the face surface 12, so when the pressure on the face surface 12 decreases, the muddy water 10 is sent from the mud feeding pipe 20, and the pressure is reduced. When the pressure on the face 20 increases, the amount of passage through the bypass pipe 32 increases, reducing the pressure on the face 12 and automatically maintaining the pressure on the face 12 at a predetermined pressure.

Therefore, even when the work is stopped for a long time, the face surface 12 is always maintained at a constant pressure by the action of the pressure regulating bypass pipe 32 as described above, so even if the muddy water 10 penetrates into the ground, The pressure does not drop and the face 1
If 2 is filled with good quality muddy water 10, the separation speed can be made slower than muddy water containing recovered bentonite, and the face 12 will be more stable, which is desirable.

In addition, by installing the pressure regulating slurry pipe 20, there are two emergency face pressure holding systems, which not only increases safety, but also increases the safety level even if the existing mud pipe 14
Even if bentonite is precipitated and accumulated in the excavation work, the newly installed mud pipe 20 can be used to carry out the excavation work, so work can be resumed smoothly after a long stoppage.

As described above, the method of the present invention is a mud shield construction method, which includes a plurality of extensible mud feeding pipes for adjusting face pressure, each having a bypass pipe for regulating pressure at one end and communicating with the face surface at the other end. A mud feeding device is installed on the ground, the mud feeding pipe for adjusting the face pressure is connected to the face surface, the bypass pipe is filled with mud water, and the mud feeding pipe for adjusting the face pressure is constantly supplied with mud water at a constant pressure. By sending out the pressure, the pressure on the face is maintained at a specified pressure when excavation work is interrupted or stopped.This allows the pressure to be maintained at a specified pressure when excavation work is stopped for a long time, when adding to an existing mud pipe, etc. Also, collapse of the face can be reliably prevented.

In addition, the mud feeding pipe for pressure adjustment that maintains the pressure on the face surface only needs to be provided with a bypass pipe at one end, so that the structure is simple, the operation is easy, and the operation can be easily confirmed.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 10... Mud water, 12... Face surface, 16... Mud water shield excavation machine (excavation machine), 20... Mud feeding pipe for pressure adjustment, 30... Valve for pressure regulation, 32... Bypass path for pressure regulation.

Claims (1)

[Claims] 1 In the mud shield method, in which muddy water containing bentonite is supplied to the face while excavating, and then the muddy water and excavated soil are discharged to excavate a tunnel or other shaft, a bypass pipe is installed at one end for pressure regulation. A mud feeding device having a plurality of extendable mud pipes for adjusting face pressure, the other ends of which are connected to the face, is installed on the ground, and the mud feeding pipes for adjusting face pressure are connected to the face. By connecting and filling the bypass pipe with muddy water and constantly sending muddy water at a constant pressure to the face pressure adjustment mud feeding pipe, the pressure on the face surface is maintained at a predetermined pressure when excavation work is interrupted or stopped. A method for maintaining face pressure in the muddy water shield method.