JP2690592B2 - Construction method of underground cavern in soft ground - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Industrial field of application” The present invention relates to a soft ground, for example, a gel-like sludge layer in a coastal landfill or a ground layer deposited in the form of a floating powder with extremely small gravity such as the moon and Mars. Method of constructing underground cavern using superplastic alloy in Japan.

"Conventional technology" Building a large space in so-called soft ground, such as the sludge layer above and the layer accumulated in the form of floating powder because the gravity in the universe is small, is the use of space under underground conditions and meteor showers. Attention is paid to the construction of the base.

Applying the open cut construction method, in which the ground is piled up and the root is cut, or the tunnel excavation method is used, etc., assuming ground improvement (hardening) to build a cavity in the ground under bad conditions as described above. Then, it becomes too unrealistic and cannot be adopted, and a means that can easily construct a cavity by using the weakness of the ground as a reverse hand without improving the ground,
The present applicant has proposed it in Japanese Patent Application No. 1-143761. The gist of the idea is to excavate a vertical shaft reaching a desired depth in soft ground, and a double-membrane air balloon consisting of an inner membrane and an outer membrane that have a difference in size corresponding to the cross section of the lining and an injection pipe connected to each membrane. Is inserted into the vertical shaft in a state of being folded small, and a weighted portion is formed by placing concrete at the position of the neck of the air balloon in the vertical shaft, and then high pressure air is passed through the injection pipe in the inner membrane. Is to inflate the air balloon to a large extent, and then an injection material such as fiber reinforced concrete is injected into the outer membrane through the injection pipe to form a lining.

[Problems to be Solved by the Invention] In the above conventional means, a ductile balloon-shaped membrane material (inner membrane) is pressurized in the soil to be inflated, and the inner and outer pressures are balanced. The outside of the membrane material (inner membrane) (inside the outer membrane) so that it is stable even if a cavity is formed and then the pressure is released.
It is said that the solidified material is filled in and the strength is developed by a three-layer structure mainly composed of the solidified material layer.

However, various stresses act on the membrane material in contact with the ground and the solidified material layer, and strength durability and structural stability are required, and the manufacturing and construction methods are complicated.

At the present time, no solidifying material with excellent performance has been found.

In addition, there is a restriction that an expander must be inserted before the excavated shaft collapses. Furthermore, after releasing the pressure to the expander itself that forms a cavity by pressure,
It has the inconvenience of requiring reinforcement after cavity formation because it has no ability to maintain its shape against external pressure.

According to the present invention, an expander that forms a cavity under pressure has both extensibility and strength, that is, a material that can be stretched freely and once the cavity is formed by expansion is selected to maintain a shape against external pressure. By doing so, it is an object of the present invention to provide a method for constructing an underground cavity in soft ground that does not require a lining process for maintaining the cavity after it is formed.

“Means for achieving the object” In order to achieve the above-mentioned object, the method of the present invention is to drive a standing hole pipe with a closed tip manufactured with fine grain superplastic alloy into soft ground, and to the standing hole pipe. Attach the bulge prevention mouthpiece, move the heating part inserted in the vertical hole pipe in an extendable manner in the longitudinal direction, and apply pressure that matches the depth of the heating part to the inner surface of the vertical hole pipe, and continue. After expanding the hole of the vertical hole pipe, the vertical hole pipe is cooled to remove the superplasticity property, the fine diameter portion of the die is cut to form the vertical hole opening, and then the vertical hole pipe is formed. A side-hole pipe with a fine-grained superplastic alloy manufactured from the side wall is used to block the tip of the side-hole. Let them join, and then make a horizontal hole pipe. Is cooled to remove the superplastic property, and the desired underground cavity is constructed by cutting and removing the narrow diameter portion.

[Operation] According to the method of constructing an underground cavity configured as described above, no pre-excavation for inserting an expansion body is required when constructing a vertical hole and a horizontal hole in soft ground, and simply setting a predetermined rigidity. By inserting a pipe that can be driven into the expansion body, it is possible to complete insertion and installation of the expansion body at a predetermined site in the ground.

Further, since the expander is made of an alloy, the strength of contact with the ground is sufficient and there is no concern. Furthermore, since the expandable body immediately develops the strength to maintain its shape against external pressure in the cooling process after expanding the pressure hole, no reinforcing treatment is necessary.

Example An example will be described with reference to the drawings.
b illustrates two basics of the hole-expanding technique used by the method of the present invention.

That is, as described above, the hole expansion by the expander according to the present invention is performed in the vertical hole portion where the external pressure in the ground changes gradually and the lateral hole portion where the external pressure is constant, but it is rational to correspond to this. Figure a is a technique when the external pressure changes gradually.
Is a metal or alloy having an equiaxed crystal structure with a crystal grain size of several mμ or less, which deforms with extremely low stress within a predetermined temperature range and exhibits a huge elongation (superplasticity).
A pipe with a closed tip made of this so-called fine-grain superplastic alloy, which is the above-mentioned "expandable body".

Under the condition that the external pressure gradually increases from the left to the right in the figure, for example, the laser heating 2 inserted in the pipe 1 in a freely extendable manner is moved in the longitudinal direction, and the inner surface side is pressed by the gas press-fitting 3 to a predetermined position. The hole is expanded while applying pressure.

Reference numeral 4 in the drawing denotes a bulge preventing mouthpiece mounted on the base end of the pipe 1. If the heating 2 is moved in this way, the superplastic part also moves and the holes are sequentially expanded. Therefore, if gas injection corresponding to the external pressure of that part is performed, a hole having a predetermined shape can be formed.

An encircling line 5 that surrounds the pipe 1 in the figure shows a heat insulating material-filled layer that is preferably filled in advance to prevent heat escape from the pipe 1. On the other hand, FIG. B shows a case where the external pressure is constant, and in this case, the treatment can be performed by simultaneous heating and simultaneous pressurization.

Next, the procedure of the configuration method of the present invention will be described with reference to FIGS. A vertical hole pipe 7 with a closed tip manufactured by using a fine-grain superplastic alloy is driven into the soft ground 8 (a).

The bulge preventing mouthpiece 4 is attached to the base end of the pipe 7, and the heating part 9 which is inserted into the pipe 7 so as to extend freely is moved in the longitudinal direction, and gas (hydrogen, oxygen, nitrogen, helium) is attached to the inner surface of the pipe 7. By press-fitting 10 (for example, the outer pressure increases toward the bottom), the hole is expanded (the technique shown in FIG. 1a) while applying pressure (downward).

The pipe 7 is cooled by, for example, charging a cooling-material spraying bar 11 to remove superplastic characteristics and impart strength as a wall material (C).

Note that the pipe 7 is generally cooled by natural cooling, but in a special environment such as vacuum where a long time is required for natural cooling, a thermosetting resin may be sprayed to forcibly remove heat. Alternatively, a method of converting heat energy into other useful energy by using a heat-electricity conversion element or a chemical heat storage material is used. The upright hole opening 12 is formed by cutting the small diameter portion of the die 4 part (d).

This completes the stable vertical hole 13. A horizontal hole pipe 14 made of the same material as the pipe 7 is driven horizontally from the side wall of the vertical hole 13 (e).

In the same way as the case of the pipe 7, the bulge prevention mouthpiece 15 is attached, and the pipe 14 is expanded with the high temperature gas injection 16 (first
The technique shown in FIG.

At this time, superplastic joining is performed between the upright hole 13 and the expanded lateral hole pipe 14, and the gap between the joining portions of both members is sealed. The expanded horizontal hole pipe 14 is installed by, for example, inserting a cooling-material removing bar 17 to remove superplastic characteristics and impart strength as a wall material (g).

The underground cavity is completed by opening the lateral hole 18 for cutting and removing the small diameter portion and finishing the inner surface (h).

[Effect of the Invention] Since the present invention is configured as described above,
The following effects are obtained.

(1) Since the expander for forming the void space is a fine crystal grain superplastic alloy having both ductility and strength, no lining care is required after forming the void.

(2) Since the expander of the present invention has a driving strength,
It is not necessary to excavate an insertion hole for soft ground that is likely to collapse and is ineffective when it is installed at a predetermined site on the ground.

[Brief description of the drawings]

1 (a) and 1 (b) are explanatory views of the basic hole-expanding technique in the present invention, and FIGS. 1 ... pipe, 2 ... laser heating, 3 ... gas injection,
4 …… Swelling prevention cap, 5 …… Enclosure, 6 …… High temperature gas injection, 7 …… Standing pipe, 8 …… Soft ground, 9 …… Heating part, 10 …… Gas (hydrogen, oxygen, nitrogen) , Helium, etc.)
Press fit, 11 …… Coolant spraying bar, 12 …… Vertical hole opening, 13…
… Upright hole, 14 …… Horizontal hole pipe, 15 …… Swelling prevention mouthpiece, 16 …… High temperature gas injection, 17 …… Coolant spraying bar, 18
...... Horizontal hole.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takafumi Shimokawauchi 2-5-14 Minamisuna, Koto-ku, Tokyo Inside Takenaka Corporation Technical Research Institute (72) Inventor Toshio Saito 2-5-14 Minamisuna, Koto-ku, Tokyo No. Ltd. Takenaka Corporation Technical Research Institute (72) Inventor Kenji Higashi 3-4-9 Teraike, Tomitabayashi, Osaka

Claims (1)

(57) [Claims] 1. A vertical ground pipe with a closed tip manufactured by using a fine-grain superplastic alloy is driven into soft ground, a bulge-preventing mouthpiece is attached to the vertical hole pipe, and the vertical hole pipe is freely extendable. After moving the inserted heating part in the longitudinal direction and applying pressure suitable for the depth of the heating part to the inner surface of the vertical hole pipe, the vertical hole pipe is continuously expanded after the vertical hole pipe is expanded. Cooling to remove superplasticity characteristics, cutting the small diameter part of the die to form vertical hole openings, and then forming a horizontal hole pipe with a closed tip from the vertical hole side wall with fine grain superplastic alloy. Driving, attaching a bulge prevention die to the horizontal hole pipe and pressurizing with high temperature gas to expand the hole and perform superplastic joining with the vertical hole, and then cool the horizontal hole pipe to obtain superplastic characteristics. Remove it by cutting and removing the small diameter part. Configuring the underground cavity in the soft ground, characterized in that the set to constitute the underground cavity.