JPH0776820A - Improving method for ground of tunnel excavation part and periphery thereof - Google Patents

Abstract

PURPOSE:To improve the peripheral ground of a tunnel with a short term of works by a method wherein a chemical injection method and timbering based on a lock bolt method are simultaneously executed. CONSTITUTION:A heading 3 is previously excavated and built below a tunnel 2 to be excavated. Outer pipes 11 for injection are driven from the interior of the heading 3 in a manner that the outer pipe is driven over the cross section of the tunnel 2 to be excavated an down to a given depth in a ground at the peripheral part thereof. By using an inner pipe for injection with a double packer introduced in the outer pipe 11 for injection, chemicals are injected. A high strength part 11A of the outer pipe 11 for injection is caused to remain in a drive position. Further, the high strength part 11A is formed of a high strength member, such as a steel pipe and reinforced plastic. A multistage anchor part is built at the high strength part 11A to improve anchoring ability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving a tunnel excavation part and the ground around it.

[0002]

2. Description of the Related Art Conventionally, when constructing a tunnel in soft ground that has low self-sustainability, such as unconsolidated soft ground, the tunnel cross section and the ground around the tunnel are usually solidified by chemical injection prior to tunnel excavation. It is tied up and strengthened so that the main fence and the face part do not collapse during tunnel excavation.

During the tunnel excavation, simultaneously with the excavation of the tunnel, a pit wall newly created by the excavation is supported to secure a hollow space. Conventionally, such chemical solution injecting work and supporting work have been performed by individual work, but these works require a great deal of manpower and time, which causes the extension of the work period and the rise of the construction cost. Furthermore, although the ground around the mine wall newly created by tunnel excavation has been consolidated and strengthened by chemical injection, there is a limit to the effect of ground improvement by chemical injection, so there is concern when supporting the pit wall. As a measure to prevent collapse of the mine wall, it is not perfect, and further improvement has been desired.

The present invention has been made for the purpose of eliminating such conventional problems.

[0005]

The present invention is a method for improving a tunnel excavation portion and the ground around it from the inside of a tunnel that has been excavated and formed substantially parallel to the tunnel to be excavated. An injection outer pipe built so as to reach a predetermined depth in the ground around the tunnel beyond the cross section of the tunnel to be excavated from the tunnel, and an injection inner pipe with a double packer inserted into the outer pipe. Including the step of injecting a chemical solution using the above, after injection of the chemical solution, the portion of the injection outer pipe left at the built-in position that is left in the surrounding ground outside the tunnel cross section is made of steel pipe, reinforced plastic, etc. A tunnel excavation part and its surroundings, which is composed of high-strength material, and in which the anchor part for enhancing the fixing property at the remaining position is formed in multiple stages in the pipe axis direction in the high-strength material constituent part. Ground improvement According to the law.

[0006]

Embodiments of the method of the present invention will be described below with reference to the accompanying drawings.

In carrying out the method of the present invention, as shown in FIG. 1, first, in the vicinity of the lower part of the virtual tunnel 2 to be constructed, in the unconsolidated soft ground 1 having low self-sustainability,
Preferably, below the midpoint of the lower side thereof, a tunnel 3 extending in the longitudinal direction in parallel with the tunnel is excavated.

The guide pit 3 is used as a working pit when performing ground improvement in a tunnel excavation portion, and usually has a diameter of about 2 to 5 m. FIG. 2 shows the excavation formation state of the guide shaft 3, and for example, the guide shaft 3 can be excavated and formed between the vertical shafts 6 and 6 by successively adding the segments 5 as the cider type excavator 4 advances.

FIG. 3 shows a situation after the guide shaft 3 is used as a work shaft and the ground is improved according to the method of the present invention. Reference numeral a indicates one ground improvement portion formed by applying the method of the present invention. The ground improvement portion a is repeatedly formed in both directions at an appropriate pitch in order to improve the entire area in the tunnel cross-section direction and the tunnel length direction. It is formed.

The formation condition of the ground improvement portion a will be described in the order of steps with reference to the drawings as follows.

FIG. 4 shows a situation when forming a hole, and the hole is formed by using the casing tube 7. The casing tube 7 is inserted from the inside of the tunnel 3 into the ground 1 through the mouth water stop box 8 under the guide of the drilling water ejected from the tip of the tube 7, and the muddy water generated by the drilling is removed. It passes through the outside of the casing 7 and is discharged to an appropriate place in the tunnel 3 through the opening / closing valve 9 provided in the mouth water-stop box 8. The insertion of the casing tube 7 for forming the hole is performed while being added in the tunnel 3, and, for example, as shown in FIG. 3, the casing tube 7 is crossed over the cross section of the virtual tunnel 2 to a predetermined depth in the ground 1a in the peripheral portion. When it reaches the end.

After the formation of the drilled hole 10, the injection outer pipe 11 is built in the drilled hole 10 as shown in FIG.

The outer pipe 11 for injection is for improving the ground by injecting a chemical solution in cooperation with an inner pipe for injection with a double packer described below, and has a multi-stage structure with an appropriate interval in the direction of the pipe length. Inlet 13 with a large number of check valve rings 12 (see FIG. 9).
(See). Since the outer pipe 11 used in the method of the present invention also serves as a lock bolt, the outer pipe 11 in FIG.
The portion 1A inserted and installed in a is formed by adding a high-strength material such as a pipe material made of steel or reinforced plastic. Further, anchor portions 15 are provided on the outer peripheral portion of the high-strength material constituting portion 1A in multiple stages in the tube axis direction in order to enhance the fixing property.

FIG. 9 shows the details of the anchor portion 15, and the anchor portions 15 at each step are composed of a linear or plate-shaped spring member that is obliquely extended downward from the attachment fixing portion 15a at the upper end. The overhang width is set to a dimension that slightly exceeds the hole diameter of the drilled hole 10. In each stage, the anchor portions 15 are installed at a plurality of positions, for example, four positions in the direction around the pipe, at intervals of 90 °. The tip of the outer tube 11 is closed, and the tip of the closed portion is provided with a non-return-shaped auxiliary anchor portion 15 'composed of two wing members 15a', 15a 'that can expand and contract against a restoring spring (not shown). Has been. The auxiliary anchor portion 15 ′ mainly functions as a fall prevention member for the outer tube 11.

The outer tube 11 having the above-described structure is inserted into the casing tube 7 from the base end side toward the tip end while being sequentially added from the tip end side inside the tunnel 3 (see FIG. 3). During the passage, the anchor members 15 and 15 'are constrained by the inner wall of the tube and can pass while retaining the contracted state against the retaining spring and the restoring spring. With this insertion, when the tip of the outer tube 11 passes through the casing tube 7,
As shown in FIG. 5, the auxiliary anchor member 15 ′ is released from the constraint on the inner wall of the tube, is automatically restored to the original expanded state by the action of the restoring spring, is locked to the hole wall 10 a of the drilled hole 10, and fixes the outer tube 11 to the outer tube 11. It is restrained at the built-in position to prevent it from falling. Outer tube 11
After the completion of the construction, the casing tube 7 is pulled out to near the mouth of the drilled hole 10 as shown in FIG. When the tube 7 is pulled out, the anchor portions 15 of each step provided on the outer tube 11 are released from the constraint on the inner wall of the casing tube, and the retained spring automatically restores the initial expanded state, and the holes 10 of the drilled holes 10 respectively. It is locked to the hole wall 10a to enhance the fixing property of the outer tube 11, particularly the high-strength material constituting portion 11A.
After the casing tube 7 has been extracted to the hole-drilling hole, the gap between the tube 7 and the outer tube 11 is closed by the plug 14 at the hole, and then sealed in the hole-drilling hole 10 through, for example, the opening / closing valve 9. The grout 16 is injected and filled. The filling of the seal grout 16 may be performed by using the following inner tube for injection.

After the outer tube 11 has been built in the drilled hole 15 and the seal grout 16 has been injected and filled, the ground is improved by injecting a chemical solution while curing and solidifying the seal grout 16. In the ground improvement process by chemical injection, as shown in FIG. 7, double packers 17 and an injection inner pipe 18 having an injection port (shown in the figure) between the packers 17 and 17 are spliced in the tunnel 3. While being taken out, it is inserted into the outer pipe 11, and then double packers 17 and 17 are manufactured in accordance with a conventional method.
In cooperation with the injection port 13 with check valve ring 12 (see FIG. 9), ground improvement is performed by injecting a chemical solution for each injection port 13 with check valve ring 12 at each stage.

This state is shown in FIGS.

One cycle of the ground improvement step is completed by sequentially passing through the steps shown in FIGS. 4 to 8, and one ground improvement portion a is obtained as shown in FIG.

Thus, one cycle of such ground improvement process is repeated at an appropriate pitch in the tunnel cross-section direction and the tunnel length direction, and is continued in both directions, whereby the tunnel cross-section direction and the tunnel length direction are obtained. The whole area of can be improved. The ground improvement portion a obtained by the method of the present invention includes a solid ground portion a ₁ reinforced by chemical injection as shown in FIG. 3, and an outer pipe 11 penetrating into the center of the solid ground portion a _1. Contains.

A portion 11A made of a high-strength material in the outer pipe 11 is a portion which remains in the ground 1a around the periphery of the outer pipe 11 after excavation of the tunnel as shown in FIG. 1A has anchoring portions 15 (see FIG. 9) formed in multi-steps on the outer peripheral portion thereof, so that pullout resistance in the proximal direction is enhanced and fixing property is enhanced.

As a result, after the tunnel is excavated, the high-strength material constituting portion 11A of the outer pipe 11 remaining in the ground 1a around the tunnel is excavated.
Due to its high strength and enhanced pull-out resistance and thus anchorage, it is possible to act like a lock bolt in the lock bolt construction method well known as one of the shafts.

Therefore, in the method of the present invention, the chemical solution injecting process and the supporting work in the rock bolt process can be performed at the same time.

After the ground improvement of the tunnel excavation portion is completed according to the method of the present invention, the portion of the virtual tunnel 2 shown in FIG. 3 is excavated according to the ordinary method.

Considering the excavability during tunnel excavation, the outer pipe 1
It is preferable to use a material such as vinyl chloride resin, which does not substantially hinder excavation, for the portion of the first portion which penetrates the region of the virtual tunnel 2.

Generally, during the tunnel excavation, while the tunnel excavation is being carried out, in parallel with the tunnel excavation, support work is carried out in order to prevent collapse of the new pit wall caused by excavation. Since the support work has already been completed, new support work can be omitted or at least simplified. Further, since the support work precedes the tunnel excavation, the work safety can be improved as compared with the case where the support work is carried out only after the tunnel excavation.

FIG. 10 shows an example of another embodiment of the method of the present invention. In this embodiment, the check valve ring 12 at each stage provided in the high-strength material component portion 11A in multiple stages has an outer side. An anchor portion 151 formed of a ring protrusion having a triangular cross-section protruding in one direction is integrally provided. The anchor 151
Has a structure capable of functioning as an anchor portion that bites into the layer of the seal grout 16. Anchor part 151
The check valve ring 12 including the ring protrusion is made of, for example, hard rubber, and has a cut opening 12a extending in the left-right width direction at an intermediate position of the vertical width.
Normally keeps the closed state, and when receiving the injection pressure from the injection port 13, opens against the retained elasticity and enables injection.

In the present embodiment, the ring protrusion and the anchor 151 are formed on the check valve ring 12, and the layer thickness of the seal grout 16 is reduced at the outer peripheral portion of the anchor 151. Therefore, even when the seal grout 16 has relatively high strength, for example, cement bentonite having a high cement content (mixing weight ratio 10 to 50: 1), the seal grout layer is formed by the injection pressure at the time of injecting the chemical liquid. It becomes possible to split.

When a high-strength seal grout is used as described above, the anchor portion 151 is more firmly locked to the high-strength seal grout layer, and the fixing property can be further enhanced. In order to further enhance the fixing property, a protrusion 19 is formed on the outer peripheral surface of the high-strength material component portion 11A.
May be provided, and the protrusion 19 may be locked to the seal grout layer.

Other configurations are substantially the same as those of the previous embodiment. In the method of the present invention, as shown in FIG. 11, after the injection of the chemical solution is completed, the lock bolt 20 is inserted and installed in the outer tube in place of the inner tube. A high strength bond 22, such as cement silk, can be used to bond and integrate. With such a configuration, the strength of the high-strength material constituting portion 11A of the sleeve pipe 11 can be further strengthened. In this case, it is preferable that the portion penetrating the inside of the virtual tunnel 2 (see FIG. 3) is made of plastic in consideration of excavation properties when excavating the tunnel.

In the method of the present invention, the formation position of the tunnel 3 is in addition to the lower portion of the virtual tunnel 2 shown in FIG.
It may be in the tunnel 2 as shown in FIGS.

[0031]

According to the method of the present invention, prior to excavation of the tunnel, the chemical solution injection work and the support work based on the rock bolt construction method can be carried out at the same time. The time can be reduced, and the construction period and the construction cost can be reduced at the same time. Further, since the support work is performed prior to the excavation of the tunnel, the stability of the work can be improved as compared with the case where the support work is performed for the first time after the tunnel excavation.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing the formation position of a tunnel in the method of the present invention.

FIG. 2 is an explanatory view schematically showing a formation position of the tunnel.

FIG. 3 is an overall view schematically showing a ground improvement situation in the method of the present invention.

FIG. 4 is an explanatory view schematically showing a drilling situation in the method of the present invention.

FIG. 5 is an explanatory view schematically showing a situation in the process of building the outer injection pipe.

FIG. 6 is an explanatory view schematically showing a situation in which the seal grout is injected and filled after the outer tube for injection is built.

FIG. 7 is an explanatory diagram schematically showing a situation at the start of injecting a chemical liquid.

FIG. 8 is an explanatory diagram schematically showing a situation at the end.

FIG. 9 is an enlarged detailed view of a high-strength material constituting portion of the injection outer tube applied to the method of the present invention.

FIG. 10 is a view corresponding to FIG. 9 showing another example of the method of the present invention.

FIG. 11 is a view corresponding to FIG. 9 showing still another embodiment of the method of the present invention.

FIG. 12 is an explanatory diagram showing an example of changing the formation position of the tunnel in the method of the present invention.

FIG. 13 is an explanatory diagram showing still another modification example.

FIG. 14 is an explanatory diagram showing still another modification example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Soft ground 2 Virtual tunnel 3 Guide shaft 4 Cider type excavator 5 Segment 6 Vertical shaft 7 Casing tube 8 Port water stop box 9 Open / close valve 10 Drilling hole 11 Injection outer pipe 12 Check valve ring 13 Pouring port 14 Plug 15 Anchor part 16 Seal grout 17 Double packer 18 Inner tube for injection 19 Protrusion 20 Lock bolt 21 Gap 22 High strength fixing material

Claims (1)

[Claims] 1. A method for improving a tunnel excavation part and surrounding ground from a tunnel formed beforehand so as to be substantially parallel to a tunnel to be excavated, the cross section of the tunnel to be excavated from the tunnel. An outer pipe for injection that is built so as to reach a predetermined depth in the ground of the surrounding area,
Including a step of injecting a chemical solution using an inner tube for injection with a double packer inserted into the outer tube, of the outer tube for injection remaining at the built-in position after injecting the chemical solution, the surrounding ground outside the tunnel cross section. The part left inside is made of high-strength material such as steel pipe and reinforced plastic. The high-strength material part has multi-stage anchors to enhance the anchorage at the left position. The method for improving the tunnel excavation part and the ground around it is characterized by being formed on the ground.