JPH0296100A - Underground space constructing method and lock bolt to be used for its execution - Google Patents

Abstract

PURPOSE:To enable work to be easily executed by inserting a lock bolt provided with a pressure resistance tube, into a lower slot set on an excavating surface, to introduce pressure fluid into the tube, and by expanding the tube to permit it to come in close contact with the internal surface of the lower slot. CONSTITUTION:A tunnel 12 is excavated in natural ground 11, and on an excavated surface 12a, a primary spray concrete layer 13 is sprayed. After that, radially through the surface 13a of the concrete layer 13, in the axial line direction of the tunnel 12, at proper intervals, a plurality of lower slots 14 are bored. After that, lock bolts 15 provided with pressure resistance tubs 17 are inserted into the lower slots 14, and after that, pressure fluid is introduced into the tubes 17 via a pressure hose 32. The tubes 17 are expanded further, and come in close contact with the external surfaces of the tubes 17, guide sleeves 19, and the internal surfaces of the lower slots 14.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for constructing underground spaces such as tunnels, underground passages, and piping cavities, and a lock for preventing rock collapse that is directly used in carrying out the method. Regarding bolts.

[Conventional technology]

As shown in Figure 6, the so-called NA'TM method, which has been implemented in recent years as a tunnel excavation method, excavates a tunnel (2) into the ground (1) using an appropriate excavation device (not shown). ), and as it progresses,
The primary shotcrete layer (3) is sprayed on the excavated surface (2a) of the tunnel (2), and the tunnel (2) is constructed using ground pressure.
) After the fluctuations in the ground (1), such as shrinkage of the ground (1), have stabilized, a secondary shotcrete layer (not shown) is applied.

If the ground (1) is soft and prone to collapse, please refer to Figures 6 and 7.
As shown in the figure, after the construction of the second shotcrete layer (3), a large number of pilot holes (4) are drilled almost radially from the surface (3a) to the ground (1), and each pilot hole is Inject mortar (5) such as early-strength mortar into (4), and then immediately insert rock bolts (6) to prevent collapse of the ground and allow the mortar (5) to solidify. 1)
This prevents deformation.

In this case, as the cutting edge is dug after the mortar (5) has set, the stress in the ground (1) on the back side of the second shotcrete layer (3) changes, causing the right angle around the rock bolt (6) to fluctuate. Mortar when directional stress increases (5)
The frictional resistance between the rock bolt (6) and the rock bolt (1) becomes the pulling resistance of the rock bolt (6) and increases to an appropriate value, thereby effectively preventing the collapse of the rock bolt (1). can be prevented.

[Problem to be solved by the invention]

In the conventional tunnel construction method as described above, before inserting the rock bolt (6) into the pilot hole (4), mortar (5) must be injected into the pilot hole (4). The work is complicated, and until the injected mortar (5) solidifies, compressive resistance and pull-out resistance against the contraction of the ground (1) rarely occur. There is a risk that the tunnel (2) will shrink and the ground (1) will become deformed.

In addition, since the conventional rock bolt (6) is made of steel, etc., it is necessary to use the ground right setting width (
W) (see Figure 6) and leave it there permanently, if underground construction is subsequently carried out in the adjacent area, the rock bolt (6) will be damaged by the excavator (as shown). (omitted), etc., may obstruct the construction work, or damage to the tunnel (2) due to breakage or movement of rock bolts (6), etc.
) There is a risk of cracks or damage occurring on the inner wall.

An object of the present invention is to provide an underground space construction method that solves all of these problems, and a rock bolt used therein.

[Means to solve the problem]

In order to achieve the above object, the method for constructing an underground space according to the invention of claim (1) is such that after drilling a pilot hole for a rock bolt in the excavated surface of the excavated underground space, the pilot hole is provided with an internal pressure fluctuation. A locking bolt for preventing collapse of the ground is inserted which has a pressure-resistant tube that expands and contracts due to the pressure-resistant tube, and then a pressure fluid is introduced into the pressure-resistant tube to expand the pressure-resistant tube and apply it to the inner surface of the lower hole. It is characterized by being anchored in close contact with the ground.

Furthermore, the underground space construction method according to claim (2) includes:
After constructing a concrete layer on the excavated surface of the excavated underground space, a pilot hole for a rock bolt is drilled from the surface of the concrete layer to the ground, and then a pressure-resistant hole that expands and contracts due to fluctuations in internal pressure is drilled in the pilot hole. A rock bolt with a tube for preventing collapse of the ground is inserted, and then a pressure fluid is introduced into the pressure tube to expand the pressure tube and bring it into close contact with the inner surface of the prepared hole, thereby anchoring the ground. After the ground has settled and the movement of the ground has stabilized, the pressure fluid in the pressure tube is released to contract the pressure tube, and the tube is extracted from the prepared hole.

In order to effectively implement the underground space construction method, the rock bolt according to the invention of claim (3) is provided with a sealed rock bolt whose one end is closed and whose other end is connected to a base for introducing pressure fluid. It is characterized by having a pressure-resistant tube that is flexible and stretchable.

This lock bolt is provided with a check valve in the cap portion that allows pressure fluid to be introduced into the pressure tube from the outside and prevents pressure fluid from being discharged from the pressure tube to the outside. ), a guide sheath is provided on the outside of the pressure tube, the base of which is connected to the base, and which is divided into a plurality of parts in the circumferential direction from the vicinity of the base to the tip, so that it can expand and contract radially and covers the outer periphery of the pressure tube. Set up (
The invention of claim (5)) is preferable.

[For production]

According to the method of the invention of claim (1), at the same time as the pressure tube expands, a large compressive force is applied to the ground from the circumferential surface of the prepared hole, and the reaction force becomes a pulling resistance force, and the rock bolt is immediately pulled out. Extraction from the pilot hole is stopped, the deformation of the ground is quickly stopped, and the compressive action on the ground due to the expansion of the pressure-resistant tube prestresses the ground, and the deformation of the ground is quickly converged. , the amount of contraction displacement of the underground space is maintained at a small value.

According to the invention of claim (2), in addition to producing the same effect as the invention of claim (1), by releasing the pressure fluid in the pressure-resistant tube, the pressure-resistant tube contracts, and the lock bolt is released from the lower hole. This produces the effect that it can be easily removed.

When the rock bolts are removed, the ground is already stable, so the movement of the ground due to the removal of the rock bolts, if any, will be minimal. I can handle it.

Further, according to the invention of claim (2), the deformation of the ground is quickly converged due to the compressive action on the ground due to the expansion of the pressure tube, and the displacement of the concrete layer is maintained at a small value.

According to the rock bolt of the invention of claim (3), by connecting the cap to a pressure fluid source or opening it to the atmosphere, the pressure tube expands due to the internal pressure of the pressure fluid introduced therein. or contract due to the release of pressure fluid.

The check valve in the invention of claim (4) functions to prevent the pressure fluid introduced into the pressure tube from being accidentally released from the mouthpiece.

The guide sheath in the invention of claim (5) not only facilitates insertion of the lock bolt into the pilot hole, but also intervenes between the pressure tube and the inner surface of the pilot hole when the pressure tube is expanded.
It acts to protect the pressure tube from damage.

〔Example〕

FIG. 1 and FIG. 2 show one implementation status of the underground space construction method of the invention of claims (1) and (2).

The implementation procedure is explained based on both figures.
1), a tunnel (12), which is an underground space, is dug by a known excavation device (not shown), and as the tunnel (12) progresses, a
The next shotcrete layer (hereinafter simply referred to as the primary concrete layer) (13) is applied by spraying.

Next, the surface (13a) of the primary concrete layer (13)
A plurality of pilot holes (14) are formed more radially and at appropriate intervals in the axial direction of the tunnel (12) (see Figure 3).
to be drilled.

Next, lock bolts (15) for preventing collapse of the ground as shown in FIGS. 3 and 4 are inserted into each pilot hole (14). In addition, as shown in Figure 2, tunnels (
12) Long lock bolts (15) lined up in the axial direction
It is preferable to arrange a short lock bolt (15') in the middle of (15).

This lock bolt (15) has a cap (16) for introducing pressure fluid such as high-pressure water or high-pressure air, and a sealable and expandable structure whose one end is connected to the cap (16) and the other end is closed. A bag-like pressure-resistant tube (17) with a cylindrical base is connected to a cap (16), and a plurality of slits (18) in the axial direction are formed from the vicinity of the base to the tip. A guide sheath (19) that covers the outer periphery of the pressure tube (17) and a male threaded portion (20) connected to one end can be expanded and contracted radially.
a) is screwed into a female threaded hole (21) provided in the cap (16), and the other end is coaxial with the cap (16) and extends into the pressure tube (17); Material (20)
It is equipped with

The pressure tube (17) is made of rubber or the like, and the guide sheath (1
9) is preferably formed from a thin steel plate or hard synthetic resin.

The base of the pressure tube (17) and the base of the guide sheath (19) are the flange (1, 6a) provided at the center of the cap (16).
It fits into the small diameter part (16a) formed closer to the core material (20) as an inner and outer double, and is tightened from the outer periphery by a band (
22), it is attached to the cap (16) in a liquid-tight or air-tight manner.

A smaller diameter part (], than the collar part (16a) in the cap (16),
6b) and the male threaded part (16c) provided on the opposite side,
A retaining plate (23) is loosely fitted to contact the surface of the primary concrete M (13) to prevent its collapse, and a nut (24) is screwed into the male threaded portion (16c).
The holding plate (23) is prevented from being removed from the male threaded portion (], 6c).

An inlet hole (25) for introducing pressure fluid is bored at the end of the cap (16) opposite to the female screw hole (21), and this inlet hole (25) and the female screw hole (21) A tapered hole (26) and an enlarged hole (27) that widen toward the female screw hole (21) are provided between the two. A steel ball (28) with a slightly smaller diameter than the enlarged hole (27) is movably fitted inside the tapered hole (26) and the enlarged hole (27). (21) is provided with a check plate (29) in the form of a grid to prevent the steel ball (28) from being pulled out from the enlarged hole (27) toward the core material (20). ) is provided.

Thus, the steel ball (28), the tapered hole (26), the enlarged hole,
A stop plate (29) or the like allows pressure fluid to be introduced into the pressure tube (17) from the outside through the inlet hole (25), and vice versa. A check valve (30) is formed which prevents the steel ball (28) from being discharged to the outside through the inlet hole (25) by tightly fitting the steel ball (28) into the tapered hole (26).

The rock bolt (15) having such a structure has its holding plate (23) attached to the surface (1) of the primary concrete layer (13).
3a) into each pilot hole (14), then insert an appropriate coupling (31) into the tip of the cap (16).
), connect the tip of the pressure hose (32) (see imaginary line in Figure 3) to the pressure fluid source (path shown), or connect the pressure hose (32) to the base (16) in advance. After joining, insert the zero bolt (15) into the pilot hole (14), then insert the lock bolt (15) from the pressure hose (32) side.
) side.

The fluid pressure of this pressure fluid is, for example, 10 to 100 kg/c
It is best to set it to about J.

When pressure fluid is introduced from the cap (16) through the core material (20) into the pressure-resistant tube (17), the pressure-resistant tube (
17) expands due to an increase in its internal pressure, and the guide sheath (1
9) and press it against the inner surface of the prepared hole (14).

Then, a compressive force acts on the ground (11) in the radial direction from the inner surface of the pilot hole (14), and prestress is applied to the ground (11) behind the primary concrete layer (13), resulting in early collapse. Converge the deformation of the ground until the primary condensation (8 layers)
The amount of displacement is maintained at a smaller value compared to the conventional one.

In addition, due to the expansion of the pressure tube (17), the outer surface of the pressure tube (17), the guide sheath (19), and the inner surface of the pilot hole (14) come into close contact with each other with high contact pressure, and the 11), a large pulling resistance force is immediately generated in the lock bolt (15).

Thereafter, when the cut end (12b) of the tunnel (12) (see Figure 2) is dug, the primary zinccrete layer (13
) and the surrounding ground (11) move little by little toward the center of the tunnel (12), and the tunnel (12) is slightly reduced in size. During this time, the earth masses exert stress on each other,
When the initial ground pressure is balanced as a whole, the ground (1
The movement of 1) stops and the ground (11) becomes stable.

After that, the rock bolts (I5) may be left in place as they were cast, but for example, if the width of the surface right of the land or the width of the acquired area is narrow, the rock bolts (15) that have been cast may If it exceeds, after the ground (11) has stabilized,
It is best to remove the lock bolt (15) from the pilot hole (14) as follows.

First, insert a suitable rod (path shown) through the entrance hole (25) of the cap (16) in Rockpol l~ (15) so that the steel ball (28) is separated from the tapered hole (26). By pushing it deep inside, the pressure fluid inside the pressure tube (17) is released to the outside.

Then, the pressure tube (17) contracts due to the drop in internal pressure, and the guide sheath (19) also contracts due to its elastic restoring force.

Due to the contraction of the pressure tube (17), the pulling resistance force of the lock bolt (15) becomes almost O, so that the lock bolt (15) can be easily pulled out from the pilot hole (14) thereafter.

At this time, the ground (11) is already stable, so there is almost no possibility that the ground (11) will change thereafter.

After that, the surface (13a) of the primary concrete layer (13)
Then, a secondary concrete layer (hereinafter simply referred to as secondary concrete layer) (as shown in the diagram) is constructed.

At this time, the pilot hole (14) may be closed with a secondary concrete layer, but if necessary, an appropriate pipe (path shown in the diagram) may be inserted into the pilot hole (14) and its tip connected to the secondary concrete layer. By protruding from the surface of the layer, the ground (11
) can also be directed to the desired location through this pipe.

” By constructing an underground space like two series, “
Effects described below as "effects of the invention" can be achieved.

FIG. 5 shows a second embodiment of the lock bolt.

In this figure, the same members as those of the first embodiment shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, as in the first embodiment, the base (16
), by rotating the operating lever (41) at the tip of the base (16),
Through the valve stem (42), the ball valve body (
A known ball valve (45) which is opened or closed by rotating the ball valve (44) is coupled thereto.

With this configuration, pressure fluid can be introduced into the pressure tube (17) by connecting the pressure hose (32) to the ball valve (45) and opening the operating lever (41). After inflating the pressure tube (17), the operating lever (41) is operated to close the valve, and the pressure hose (32) is removed from the cap (16), leaving the lock bolt (15) in place. Then, by simply opening the operating lever (41), the pressure fluid inside the pressure tube (17) can be released to the outside and the pressure tube (17) can be contracted.

[Examples of odd forms]

The invention can be implemented in many different ways in addition to those described above. For example, the following variations are possible.

(1) If the purpose is only for early stabilization of the ground, 1
It is also possible to simply drill a pilot hole directly into the excavated surface of the underground space, insert a rock bolt therein, and expand it without spraying the next shotcrete layer or regardless of that.

(2) The guide sheath (19), check valve (30), ball valve (45), core material (20), etc. may be omitted if necessary. In addition, if neither the check valve (30) nor the ball valve (45) is provided, the cap (16)
) It is preferable to control the introduction and discharge of pressure fluid into the pressure tube (17) by a control means such as a control valve on the pressure hose (32) side connected to the pressure hose (32).

(3) If the check valve (30) is of a different type, for example, when pressure fluid flows from one direction, damper tongues or a plurality of petal-shaped closing members open to prevent the flow. If the pressure fluid is allowed to flow from the other direction, the dampers, tongues, or closing members may be closed to prevent the flow.

(4) A check valve (30) may be provided within the core material (20).

〔Effect of the invention〕

According to the underground space construction method of the present invention, the following effects can be achieved.

(1) Unlike the conventional method, there is no need to pour mortar into the prepared hole, so the work is simple.

(2) At the same time as introducing pressure fluid into the pressure-resistant tube, prestress is applied to the ground, which can stabilize the ground at an early stage, and at the same time as the pressure-resistant tube expands, a large pull-out resistance is applied to Rockpol I~ can be applied to the ground, so it is possible to immediately prevent the movement of the ground, and it can be applied to expansible ground, etc., to achieve a tremendous effect.

(3) According to the invention of claim (2), after the movement of the ground is stabilized, the pressure fluid in the pressure tube is released, the pressure tube is contracted, and the rock bolt is extracted from the pilot hole. Not only can the removal work of rock bolts be performed easily and smoothly, but even when the installed rock bolts exceed the width of the land acquisition area or the width of the ground rights, by removing them, it is possible to perform the work of removing rock bolts easily and smoothly. Land problems caused by rock bolts crossing borders can be solved before they occur.

According to the lock bolt of the present invention, the above method can be carried out effectively.

In addition, the rock bolt of the present invention can apply a high compressive force capable of resisting ground pressure to the ground from its outer periphery depending on the sealing pressure and bolt length, and can apply a high compressive force to the ground in the radial direction inside the ground. Since it is possible to generate compressive stress according to Poisson's ratio, it has the advantage of being highly applicable to excavation of large cross-sections and excavation of poor geology with a poor ground strength ratio.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view perpendicular to the central axis of the tunnel, showing one implementation status of the underground space construction method of the present invention; FIG. 2 is a vertical cross-sectional view also taken along the central axis of the tunnel; and FIG. FIG. 4 is a vertical sectional view showing the first embodiment of the lock bolt of the present invention inserted into the prepared hole.
5 is a longitudinal sectional view taken along the X-ray; FIG. 5 is a longitudinal sectional view of the second embodiment of the rock bolt of the present invention; FIG. 6 is a longitudinal sectional view showing a state of implementation of a conventional tunnel excavation method; The figure is an enlarged vertical cross-sectional view of the Y section in FIG. 6. (]1) Ground (12) Tunnel (12a) Excavation surface (], 2b) Cut edge (
13) Primary shotcrete layer (1, 3a) surface (
14) Pilot hole (15) Lock bolt (16) Cap (16a) Flange (1
6b) Small diameter part (16c) Male thread part (1
7) Pressure tube (18) Slit (19)
) Guide sheath (20) Core material (20a) Male thread (21) Female thread (22) Tightening band (23) Holding plate (24) Nut
(25) Inlet hole (26) Tapered hole (28) Steel ball (30) Check valve (32) Pressure hose (42) Valve stem (44) Ball valve body (27) Enlarged hole (29) Removal stop plate ( 31) Coupling (41) Operation lever (43) Valve box (45) Ball valve = 1 Figure 7

Claims (5)

[Claims] (1) After drilling a pilot hole for a rock bolt in the excavated surface of the excavated underground space, install a rock bolt in the lower hole to prevent collapse of the ground, which has a pressure-resistant tube that expands and contracts due to fluctuations in internal pressure. A method for constructing an underground space, which comprises: inserting the pressure-resistant tube, and then introducing pressure fluid into the pressure-resistant tube to expand the pressure-resistant tube so as to bring it into close contact with the inner surface of the prepared hole, thereby anchoring it to the ground. (2) After constructing a concrete layer on the excavated surface of the excavated underground space, a pilot hole for a rock bolt is drilled from the surface of the concrete layer to the ground, and then, in the pilot hole, expansion and expansion occur due to fluctuations in internal pressure. A rock bolt for preventing collapse of the ground that has a pressure tube that contracts is inserted, and then a pressure fluid is introduced into the pressure tube to expand the pressure tube and bring it into close contact with the inner surface of the prepared hole. A method for constructing an underground space, which comprises: after anchoring on a mountain and stabilizing movement of the ground, pressurized fluid in the pressure tube is released to contract the pressure tube and extract it from the pilot hole. (3) A rock bolt for preventing collapse of ground, which is used directly in carrying out the method according to claim (1) or (2),
A lock bolt characterized by comprising a pressure-resistant tube having sealability and elasticity, one end of which is closed, and the other end of which is connected to a mouthpiece for introducing pressure fluid. (4) Claim (3) The cap portion is equipped with a check valve that allows pressure fluid to be introduced into the pressure tube from the outside and prevents pressure fluid from being discharged from the pressure tube to the outside.
) Rock bolts listed. (5) The base is connected to the cap on the outside of the pressure tube,
Claim (3) or (4) further comprising a guide sheath that covers the outer periphery of the pressure tube so that it can expand and contract radially by being divided into a plurality of parts in the circumferential direction from the vicinity of the base to the tip.
) Rock bolts listed.