JP2856348B2 - How to suppress the increase in propulsion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing an increase in propulsion resistance.

[0002]

2. Description of the Related Art The propulsion method has been performed as follows. First, a starting shaft is dug in the ground, and a propulsion device pedestal having a bearing wall is provided in the starting shaft, and a propulsion device having a propulsion jack is mounted on the pedestal. Also, the excavator and the propulsion pipe are carried into the starting shaft, the face facing the bearing wall in the starting shaft is excavated by the excavator to dig a side hole, and the propulsion pipe is inserted into the dug side hole. Push the end with a propulsion jack to advance the propulsion tube with the excavator. A similar propulsion pipe is further added to the end of the advanced propulsion pipe, and the added propulsion pipe is pushed by the same propulsion jack for propulsion. In this way, propulsion pipes are buried in the ground one after another. Although a steel pipe may be used as the propulsion pipe, a concrete pipe is often used.

As is apparent from this description, in the propulsion method, the power for propelling the propulsion pipe mainly depends on the propulsion jack. The driving force is large inevitably as the number of propulsion tube to be spliced is increased. However, there is a limit to the jacks that can be arranged depending on the size of the propulsion pipe, and there is a permissible load capacity so that no more propulsion can be applied. The reaction force is limited and cannot receive any more reaction force. Therefore, in order to perform long-distance propulsion, it is necessary to improve the sliding between the outer surface of the propulsion pipe and the wall surface of the hole and to reduce the propulsion resistance as the propulsion proceeds.

[0004] In order to reduce the above-mentioned propulsion resistance, a lubricant has hitherto been injected between the propulsion pipe and the hole wall surface. As the lubricant, a suspension of a water-absorbing polymer or a suspension obtained by adding a suspension stabilizer such as carboxymethyl cellulose to fine powder of bentonite was used. The lubricant was in a liquid state and injected around the propulsion pipe through a small hole formed in the propulsion pipe. This lubricant goes well into narrow friction surfaces
As is the fluid having a relatively low viscosity. Moreover, this lubricant is intended only to reduce the frictional resistance between the propulsion pipe and the wall surface of the bore, and when the propulsion resistance is felt to be large during propulsion, an appropriate small size of the propulsion pipe is used. It was only to be injected through the hole.

[0005] The conventional propulsion method using a concrete pipe as the propulsion pipe and merely injecting a lubricant from a small hole in the concrete pipe has not been sufficient to suppress an increase in propulsion resistance. That is, although the propulsion resistance could be reduced immediately after the lubricant was injected, the propulsion resistance increased after a while. Also, to prevent the propulsion resistance from increasing over time, even if the amount of lubricant is increased and the friction coefficient is reduced , the earth pressure will increase,
It wasn't worth it. Therefore, it was necessary to improve this point.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks associated with the propulsion method. In other words, in the propulsion construction method, the propulsion resistance has increased significantly as the construction progressed until now.However, by improving this, the propulsion resistance does not increase significantly even when the construction progresses, and it is intended to make the propulsion construction easier. Is what you do.

[0007]

The present inventor has concentrated on reducing the frictional resistance of the conventional propulsion method by taking into account only the friction coefficient generated between the hole wall surface and the propulsion pipe. We paid attention to that. The inventor has noticed that the increase in the propulsion resistance is largely affected by the earth pressure applied to the propulsion pipe in addition to the above-described friction coefficient. That is, the propulsion resistance F is the product of the friction coefficient μ between the outer surface of the propulsion pipe and the ground and the earth pressure P applied to the propulsion pipe. In the conventional propulsion method, the friction coefficient μ is reduced by injection of a lubricant. Focusing on that, he noticed that he did not think much about preventing an increase in earth pressure P.

Generally, the earth pressure applied to the propulsion pipe is considered to be the loose earth pressure of Telzergie in terms of geotechnical engineering. In particular, the excavator's cutting edge is made to have a diameter slightly larger than the outer diameter of the propulsion tube, so a gap between the hole dug by the excavator and the propulsion tube is called a tail void. Usually, a gap having a thickness of 1 to 3 cm is formed, and the ground loosens the ground immediately above the propulsion pipe , so that earth pressure is applied to the propulsion pipe. It has been assumed that this earth pressure can be calculated by the formula of Telzergie. However, Telzergie's formula only takes into account the first loose earth pressure, ie the first loose earth pressure. This is because if the propulsion extension is relatively short, e.g.
It is appropriate if the propulsion work is completed within 2 to 3 weeks within the range of 0 m.

However, at present, the propulsion extension is 300-
The distance is as long as 500 m, and the period during which the propulsion work is performed is often as long as one to two months. In such large-scale propulsion works, the earth pressure is determined only by the primary earth pressure calculated by the formula
Notwithstanding, the earth pressure after secondary is also added . The present inventor studied the propulsion method including such a large-scale propulsion work, and as a result, it was not enough to take only the primary loose earth pressure into consideration, and the range of the loose earth pressure was further increased. Expand two
We found that it is necessary to consider the earth pressure after the next . Finally, they found that it was necessary to consider that a large earth pressure close to the total earth pressure would be applied to the propulsion pipe.

Further, the inventor of the present invention has found that if the perimeter of a tunnel at a deep place such as about 100 m underground is supported by a buckling frame support, the plastic flow velocity of the ground becomes extremely slow, and the tunnel is crushed. Inspired by the fact that the period that can be maintained without being extended is inspired, it has been found that when the tail void is filled with a plastic material, loosening and expansion of earth pressure can be prevented. Based on such findings, the present invention is based on filling the tail void with a plastic material to prevent the loose earth pressure applied to the propulsion pipe from expanding, thereby suppressing an increase in propulsion resistance.

[0011] The plastic material must be injected from the underground to Teruboido. It requires a moderate viscosity for plastic materials
And must be in a form that can be injected by a pressure pump . Also, the plastic material must be harmless after being injected into the tail void. Furthermore, the plastic material keeps its plasticity in the tail void ,
Shear resistance must be kept small even in thickness . Furthermore, plastic materials are difficult to penetrate into the ground.
I have to. Due to such demands, the present inventors have found that it is suitable to use a plastic material mainly composed of clay, to which water is added to form a cream, which has a high viscosity.

On the other hand, the propulsion tube must not alter the plastic material even if the plastic material comes into contact with it. In other words, the propulsion tube must be configured so that the original plasticity is maintained even when the plastic material comes into contact with the propulsion tube for a long time. Since the iron pipe has poor water absorption, it can be used as a propulsion pipe as it is. However, some concrete pipes have high water absorption, which absorbs the moisture in the plastic material and solidifies the plastic material. Therefore, it is necessary to reduce the water absorption.
The present invention has been completed based on the above findings.

According to the present invention, in a propulsion method, a plastic material containing clay and water as main components is used by using a low water-absorbing propulsion pipe.
Into the gap provided between the propulsion pipe and the ground ,
Within the plastic material, the plastic material retains its initial plasticity
The gist of the present invention is to provide a method for suppressing an increase in propulsion resistance, which is characterized by causing shear deformation .

In the present invention, a low water-absorbing propulsion tube is used. Metal pipes such as ductile pipes and steel pipes, and synthetic resin pipes such as hard vinyl chloride pipes and polyester pipes are sometimes used as propulsion pipes. This can be used as it is as a propulsion pipe. The problem is concrete pipes. As described above, concrete pipes have high water absorbency, and therefore, when used in the present invention, they need to be low water absorbency. In order to reduce the water absorption, a method of applying a waterproof coating on the outer surface of the concrete pipe, bonding a hydrophobic film, or adding a waterproofing agent to the concrete material itself can be adopted.

As the waterproof paint, a solution in which an epoxy resin, polyethylene, polyvinyl chloride, silicon resin, or the like is dissolved in an organic solvent, or an aqueous emulsion of the above resin can be used. These can be applied to the outer surface of the concrete pipe and dried to make the concrete pipe low in water absorption.

In order to adhere a hydrophobic film, a thermoplastic resin such as polyethylene or polyvinyl chloride is formed into a film or tube in advance, and this film is adhered to the outer surface of a concrete tube or a concrete tube is adhered. Wrap it in a tube. When a tube is used, after the concrete tube is surrounded by the tube, the air existing between the tube and the concrete tube can be suctioned under vacuum to bring the tube into close contact with the concrete tube. When a tube is used, the tube may be provided with heat shrinkability, and after surrounding the concrete tube with the tube, the tube may be heated and shrunk to bring the tube into close contact with the concrete tube.

The concrete pipe thus made low in water absorption has a surface impervious to water or repels water, so that the plastic material can maintain plasticity around the concrete pipe for a long time.

The most important feature of the present invention is that the tail void is filled with a plastic material to facilitate propulsion by shear deformation of the plastic material. The plastic material is made of clay as a main component and water added thereto. The plastic material,
It is a creamy or grease-like high-viscosity material that deforms when external force is applied, but retains its shape without external force. Since the state is semi-solid, large pressure must be applied to inject it. Plastic materials can be stabilized by adding a suspension stabilizer in addition to clay and water. As the suspension stabilizer, sodium carboxymethylcellulose, polyvinyl alcohol (Poval) or the like is used .

It is preferable that the viscosity of the plastic material is slightly changed depending on the properties of the ground. When the ground has a small N value, in other words, when the ground has low self-sustainability and easily collapses, or when the ground has a high water permeability, the viscosity of the plastic material is increased in proportion thereto. However, the approximate viscosity of plastic materials is 8,000 to 30,000 m in international units.
pa · s (millipascal second). By the way, the viscosity of the lubricant used so far in the propulsion method has to penetrate into a narrow friction surface.
It is a fluid within the range of ３3000 mpa · s.

As the main component clay in the plastic material, Kasaoka clay, Kibushi clay, kaolin clay, Gairome clay and the like can be used. These clays are fine particles having a particle size of 5 μm or less and have large water absorption. When water is added thereto, the viscosity becomes high, but when water is further added, the viscosity decreases as the amount of water increases. In the present invention, the viscosity when water is added is 80 as described above.
This is used as a plastic material in the state of 00 to 30000 mpa · s.

According to the present invention, when the plastic material is injected into the tail void, the injection pressure is measured so that the pressure is opposed to the calculated loose earth pressure. If the plastic material was injected after the first loose earth pressure occurred,
Since the effect is drastically reduced, the tail void is injected as soon as it occurs. For this purpose, the injection port of the plastic material should be located as far forward as possible, and if possible, the injection port should be provided on the outer periphery of the excavator. Shall be provided. When the injection port is provided in the propulsion pipe, a small hole conventionally provided in a concrete pipe or the like can be used as the injection port.

According to the present invention, the plastic material is injected such that the plastic material fills the tail void without any gap. When the plastic material is filled without gaps, the injection pressure rises sharply, so that it can be known from the observation of the injection pressure that the plastic material has been filled without gaps. During the propulsion work, the injection of the plastic material is continually performed, and the amount of the injected plastic material is sufficient to fill the tail void to be formed.

According to the present invention, after the plastic material is injected into the tail void from the front injection port, the plastic material is injected into the tail void from the small hole of the subsequent propulsion pipe slightly distant from the injection port to form the gap. Investigate the presence or absence. For example, if the plastic material can be injected through a small hole in the propulsion pipe at a distance of about 10 to 20 m from the front injection port, and the plastic material can be injected with a small injection pressure, it will leave a void around the outer circumference of the propulsion pipe. It is proof that there is. Therefore, a plastic material is further injected from the small hole, and the press-in is continued until the injection pressure antagonizes the earth pressure applied to the outer periphery of the propulsion pipe. This is necessary to completely fill the tail void with a plastic material.

In the present invention, during propulsion, the plastic material is continuously injected into the tail void as described above. Thus, the propulsion is performed while maintaining the state in which the propulsion pipe is floating in the plastic material. This reduces propulsion resistance and therefore facilitates propulsion.

[0025]

According to the present invention, since the plastic material is filled in the gap provided between the propulsion pipe and the ground in the propulsion method, the generation of loose earth pressure is suppressed, and thus the soil during the propulsion work is suppressed. Low pressure build-up, and therefore over a long period of time
A long distance can be propelled safely and reliably . In addition, since the plastic material is mainly composed of clay and water, it is easily available, does not cause pollution, and is inexpensive. Since a low water-absorbing material is used as the propulsion tube, the plastic material injected from the propulsion tube into the tail void does not absorb moisture by the propulsion tube, and therefore maintains plasticity for a long time. As a result, the propulsion pipe is in a state of floating in the plastic material during the propulsion work,
The thrust resistance is mainly shear resistance of the plastic material, and the thrust speed is usually as small as 0.0005 cm / sec. Therefore, according to the method of the present invention, an increase in propulsion resistance can be reliably suppressed. As a result, long-term propulsion work can be easily performed over a long distance. In addition,
The bright method uses a tail void that is highly viscous (ie, has a low moisture content).
Ground) Subsidence after completion of propulsion because of filling with plastic material
Is also produced. The present invention provides such benefits.

Claims (4)

(57) [Claims] In a propulsion method, a plastic material mainly composed of clay and water is filled into a gap provided between the propulsion pipe and the ground using a low water-absorbing propulsion pipe. Plastic material
To maintain the initial plasticity, causing shear deformation in the plastic material.
And characterized in that strained, a method of suppressing an increase in propulsion resistance. 2. The low water-absorbing propulsion pipe is a metal pipe or a synthetic resin.
Pipes or concrete pipes that have been treated to prevent water absorption
The increase in propulsion resistance according to claim 1, which is characterized in that:
how to. 3. The filled plastic material loosens and antagonizes earth pressure.
Wherein the pressure is constant.
Is a method for suppressing an increase in propulsion resistance according to 2. 4. After the plastic material is injected, the injection port
Inject more plastic material from the small hole of the propulsion pipe at the back,
Continue the injection until the injection pressure loosens and antagonizes the earth pressure
4. An increase in propulsion resistance according to claim 3, characterized in that:
how to.