KR102028547B1 - Construction method of messer shield - Google Patents

Abstract

The present invention discloses a mesa shield method using a porous material. Mesa shield method using the porous material of the present invention is to advance the mesa plate in the excavation direction, the step of the mesa plate in contact with the pre-installed porous material and support material; Disposing a subsequent perforated material in a space formed at the bottom of the tail of the mesa plate; Disposing a subsequent porous material in a space below the tail of the mesa plate, wherein the subsequent porous material is disposed to be in close contact with the mesa plate tail and fixed to the installed porous material; Excavating the earth and sand under the advanced mesa plate; And installing a subsequent support material in the excavated space.

Description

Mesa shield method using porous materials {CONSTRUCTION METHOD OF MESSER SHIELD}

The present invention relates to a mesa shield method using a porous material, and more particularly, to a mesa shield method using a porous material to excavate a tunnel by closely pushing the mesa plate with the porous material.

Referring to FIG. 1A, in general, the mesa shield method prevents the arch sliding phenomenon by constructing the steel pipe grouting 250 at the tip of the tunnel in a complex stratum section or a soft ground section, which is difficult to apply a mechanical method. As a method for safely constructing a tunnel by minimizing deformation, the mesa plates 210 are arranged in parallel to move forward in the tunnel excavation direction, and the subsequent porous material 220 is installed in a space formed after the mesa plates 210 are advanced. And, excavating the internal ground, repeating the installation of the support material 230 refers to a method of excavating the tunnel. The hydraulic jack 240 is mainly used to advance the mesa plate 210.

This mesa shield method is possible to change the construction in the vertical and horizontal direction, various linear design is possible, the mesa plate is compact and can be pushed with a small pressure, the work tool can be miniaturized, and the shape or size of tunnel such as box or arch It is possible to construct without, and has the advantage of easy to change the excavation method or excavation direction when the rock layer appeared during the excavation.

However, referring to FIG. 1B, in the conventional mesa shield method, since the moving mesa plate 210 is supported only by the support members 232, 234, and 236, the load is difficult to be dispersed and the mesa plate 210 and the support member 232. , 234, the friction force acts greatly, there was a problem that requires a lot of force to advance the mesa plate (210).

In addition, due to the gap between the porous material 220 and the tail portion 216 of the mesa plate 210, the tip deflection of the tail portion 216 occurs, the ground voids by the interval d is generated and the ground is settled. There was a problem happening.

The present invention is to solve the above problems, an object of the present invention in the excavation of the tunnel using the mesa plate by pushing the mesa plate in close contact with the porous material, to distribute the load to reduce the friction between the support material and the mesa plate, It relates to a mesa shield method that can minimize ground voids to prevent ground subsidence.

In the mesa shield method using the porous material according to an embodiment of the present invention for solving the above problems, the mesa plate is advanced in the excavation direction, the mesa plate is already installed during the advance process and the completion of the advance Contacting and supporting the porous material and the support material;
Disposing a subsequent porous material in a space formed at a lower end of the tail of the mesa plate;
Disposing the subsequent perforation in the space below the tail of the mesa plate,
Disposing a brace member between the subsequent porous material and the support material to keep the position in close contact with the lower surface of the mesa plate tail;
The subsequent porous material is arranged to be fixed to the pre-installed porous material to be in close contact with the lower surface of the mesa plate tail, but the retaining jaw on the opposite end side of the excavation in the excavation direction so that the subsequent porous material is impossible to move in the excavation direction Disposed on an edge of the member;
Excavating earth and sand under the advanced mesa plate; And
Installing a subsequent support in the excavated space;
Characterized in that it comprises a.

The step of disposing the subsequent porous material may include disposing a bracing member under the subsequent porous material.

Steps corresponding to each other may be formed on the contact surfaces of the pre-installed porous material and the subsequent porous material.

In the contact surface, a lower stepped portion may be formed in the pre-installed porous material, and an upper stepped portion may be formed in the subsequent porous material.

A horizontal contact surface is formed by the step, and a fixing pin and a fixing groove, or a fixing groove and a fixing pin are formed in the horizontal contact surfaces of the pre-installed porous material and the subsequent porous material, respectively. Protruding from the contact surface may be inserted into the fixing groove.

Mesa shield method using a porous material according to another embodiment of the present invention, the mesa plate for advancing in the excavation direction, the mesa plate in the advancing step is supported by contact with the pre-installed porous material and support material; Installing first and second level supports respectively on two rows of support members positioned at the bottom of the mesa plate tail, wherein the first level supports are installed to prevent movement in the excavation direction; Disposing a subsequent perforated material on the first and second level supports, such that the engaging jaw formed at the opposite end of the excavated perforated material is caught by an edge of the first level support; Raising the first and second level supports to adhere the subsequent porous material to the tail of the mesa plate; Excavating earth and sand under the advanced mesa plate; And installing a subsequent support material in the excavated space; Characterized in that it comprises a.

The step of placing the subsequent porous material may include installing a brace member between the first and second level supports and the lower support member.

The first level support and the lower support material is formed in communication with the compression level bolt hole, and may include the step of inserting the compression level bolt into the compression level bolt hole.

First and second compression level bolt holes are formed in the first and second level supports and lower support members, respectively, and the compression level bolts are inserted into the first and second compression level bolt holes. Tightening a level bolt may include elevating the first and second level supports.

Contact support by the pre-installed porous material of the mesa plate, the tail portion of the mesa plate may be made in contact with the pre-installed porous material.

Steel wires may be disposed on the upper surface of the porous material in the excavation direction.

According to the mesa shield method according to an embodiment of the present invention, in the excavation of the tunnel using the mesa plate advances in the excavation direction, by pushing the mesa plate in close contact with the porous material during the forwarding process and the completion of the forward, Dispersion can reduce the friction between the support material and the mesa plate, and can provide a mesa shield method that can prevent the ground settlement by minimizing the ground voids.

1A and 1B are views for explaining a mesa shield method according to the present invention.
2 to 4 are views for explaining the mesa shield method according to an embodiment of the present invention.
5 is a perspective view for explaining a porous material according to an embodiment of the present invention.
FIG. 6 is a partial cross-sectional view taken along the line BB of FIG. 5.
7 is a perspective view for explaining a porous material according to another embodiment of the present invention.
FIG. 8 is a partial cross-sectional view taken along the line BB of FIG. 7.
9 to 11 are views for explaining the mesa shield method according to another embodiment of the present invention.

In order to help the understanding of the features of the present invention as described above, it will be described in more detail with respect to the mesa shield method according to the present invention with reference to the accompanying drawings.

Hereinafter, the described embodiments will be described on the basis of the most suitable embodiments for understanding the technical features of the present invention, and the technical features of the present invention are not limited by the described embodiments. It is to be exemplified that the present invention can be implemented as in the following embodiments. Accordingly, the present invention may be modified in various ways within the technical scope of the present invention through the embodiments described below, and such modified embodiments fall within the technical scope of the present invention. And, in order to help the understanding of the embodiments described below, in the reference numerals described in the accompanying drawings, among the components that will have the same function in each embodiment, the related components are denoted by the same or extension numbers.

2 to 4 are views for explaining the mesa shield method according to an embodiment of the present invention.

2, in order to excavate earth and sand, the first support member 32, the second support member 34, the third support member 36 and the fourth support member 38 are provided. , 38 is provided to prevent the tunnel, which has already been excavated, in advancing the mesa plate 10 in the excavation direction (arrow A direction) to excavate the tunnel.

The first, second, third and fourth support members 32, 34, 36 and 38 may be composed of upper support members 32a, 34a, 36a and 38a and side support members 32b, 34b, 36b and 38b, respectively. have. The side support members 32b, 34b, 36b, and 38b are installed at right angles to the ground with their pairs at regular intervals. The upper support members 32a, 34a, 36a, 38a are installed on the upper surface of the pair of side support members. In order to prevent collapse of the excavated tunnel, the support material other than the upper support material (32a, 34a, 36a, 38a) and the side support material (32b, 34b, 36b, 38b) may be further installed, but the illustration is omitted here. It was.

As the support members 32, 34, 36, 38, generally, I-beam or H-beam can be used.

The previously installed porous material 22 is disposed on the first upper support member 32a and the second upper support member 34a. Bracing members 42a and 42b may be disposed between the previously installed porous material 22 and the first and second upper support members 32a and 34a.

The mesa plate 10 has a plate shape which is elongated in the excavation direction as a whole. Mesa plate 10 may be composed of a head 12, the body 14 and the tail (16). A plurality of mesa plate 10 is arranged in parallel in the excavation direction is used for the excavation of earth and sand.

The mesa plate 10 is advanced in the tunnel excavation direction for the excavation of the tunnel. In the advancing process, the mesa plate 10 is in contact with the pre-installed porous material 22, the third upper support member 36a and the fourth upper support member 38a to be supported.

Unlike the conventional mesa shield method according to the present invention, in the advance of the mesa plate 10, the mesa plate 10 and the third and fourth upper support member (36a, 38a) in addition to the pre-installed porous material 22 and Is contacted and supported. Therefore, load distribution is easy and frictional force between the mesa plate 10 and the third and fourth upper support members 36a and 38a can be reduced.

A steel wire having a thin diameter such as a piano steel wire may be disposed in the tunnel excavation direction on the upper surface of the previously installed porous material 22. When the steel wire is disposed, the friction between the mesa plate 10 and the pre-installed porous material 22 may be reduced.

The decrease in frictional force is due to a decrease in the contact area between the mesa plate 10 and the installed porous material 22. That is, the decrease in the contact area is due to the increase in pressure at the contact surface between the mesa plate 10 and the pre-installed porous material 22, the increase in pressure is due to the increase in heat generation, and the increase in heat generation is due to the decrease in the friction coefficient. As a result, the reduction of the friction coefficient leads to the decrease of the frictional force.

As a result, the mesa plate 10 can be more easily advanced by the load distribution and the reduction of the frictional force due to the steel wire.

The mesa plate 10 is advanced in the excavation direction to the extent that the end of the trunk portion 14 on the side of the tail portion 16 is disposed on the third upper support material 36a. At this time, a predetermined space is formed below the mesa plate 10. Although not shown, the mesa plate 10 may be advanced by a hydraulic jack that is supported by the second upper support member 34a and pushes the mesa plate 10 in the excavation direction.

Referring to FIG. 3, the subsequent porous material 24 is disposed in the space while being coupled to and fixed with the existing porous material 22.

Steps corresponding to each other may be formed on the contact surfaces of the installed porous material 22 and the subsequent porous material 24.

In the contact surface, the lower stepped portion 22b may be formed in the installed porous material 22, and the upper stepped portion 23a may be formed in the subsequent porous material 24. When the lower step 22b and the upper step 24a are formed as described above, the lower step 22b and the mesa plate 10 of the second step 22a of the subsequent porous material 24 are provided. It can be easily pushed between the tail 16 of the. Therefore, workability of arranging the subsequent porous material 24 can be improved.

Referring to FIG. 4, after the subsequent porous material 24 is installed, the subsequent porous material 24 is brought into close contact with the lower surface of the tail 16 of the mesa plate 10, and at the same time, Bracing members 44a and 44b may be disposed between the second and third upper support members 34a and 36a, respectively. By arranging the bracing members 44a and 44b, the subsequent perforated material 24 may be in close contact with the lower surface of the tail 16 to maintain its position.

After arranging the subsequent porous material 24 or the supporting members 44a and 44b, the earth and sand under the mesa plate 10 is excavated, and a fifth support material 40 is newly installed in the excavated space. The fifth support member 40 may be configured of the fifth upper support member 40a and the fifth side support member 40b in the same manner as the pre-installed support members.

Thereafter, when the mesa plate 10 is advanced in the tunnel excavation direction, the mesa plate 10 is brought into contact with and supported by the subsequent porous material 24 and the fourth and fifth support members 38 and 40.

On the other hand, unlike the conventional case, according to the mesa shield method according to the present invention, the gap (D) by the thickness of the tail portion 16 of the mesa plate 10 between the porous material (22, 24) and the ground thereon Only is formed. That is, as the porous materials 22 and 24 and the tail portion 16 are in close contact with each other and the tunnel is constructed, only the gap D corresponding to the thickness of the tail portion 16 is formed. Accordingly, settlement of the ground voids and the upper ground on the upper part of the porous materials 22 and 24 may be minimized.

FIG. 5 is a perspective view for describing a porous material according to an exemplary embodiment of the present invention, and FIG. 6 is a partial cross-sectional view taken along line B-B of FIG. 5.

As described above, steps 22b and 24a corresponding to each other may be formed on the contact surfaces of the porous materials 22 and 24 adjacent to each other. In addition to the vertical contact surfaces, the steps 22b and 24a may be formed by the steps 22b and 24a. Horizontal contact surfaces may be formed.

5 and 6, the first fixing groove 22d is formed on the horizontal contact surface of the one side of the porous material 22 for mutual fixing by coupling the adjacent porous materials 22 and 24 to each other. First fixing pins 24c may be formed on the horizontal contact surface of the common material 24, respectively. In addition, a guide groove 22e may be formed extending from the end of the one side porous material 22 to the first fixing groove 22d.

By means of elastic means (not shown), the first fixing pin 24c maintains the state protruding from the horizontal contact surface of the other cavity member 24, and draws an arc around one axis when subjected to a constant force. It may have a configuration that is folded to the horizontal contact surface side.

Referring to FIG. 6, when the other side porous material 24 moves in the direction of the arrow C to be combined with the one side porous material 22, the first fixing pin 24c is folded and moves along the guide groove 22e to move the first. It is combined with the fixing groove 22d. At this time, the first fixing pin 24c is returned to the state protruding from the horizontal contact surface by elasticity. As a result, one side porous material 22 and the other side porous material 24 may be combined.

Meanwhile, as shown in FIG. 5, the porous materials 22 and 24 may be formed by joining a plurality of square pipes by welding or the like.

7 is a perspective view for explaining a porous material according to another embodiment of the present invention, and FIG. 8 is a partial cross-sectional view taken along the line B-B of FIG. 7.

As shown in FIGS. 7 and 8, in order to mutually secure by coupling the adjacent porous materials 22 and 24 to each other, the second fixing groove 22h is formed on the horizontal contact surface of the one porous material 22, and the other Second fixing pins 24f may be formed on the horizontal contact surface of the common material 24, respectively. In addition, a guide portion 24i may be formed on an upper surface of the lower stepped portion 22b of the one side porous material 22.

By means of elastic means, the second fixing pin 24f is kept in a state of protruding from the horizontal contact surface of the other porous member 24, but is pushed into the upper step of the other porous member 24 when subjected to a constant force. It can have a configuration to go in. The elastic means may be a spring 24g.

Referring to FIG. 8, when the other side porous material 24 moves in the direction of the arrow C and is engaged with the one side porous material 22, the second fixing pin 24f is along the guide portion 24i and the other side porous material 24 is provided. After being pushed into the upper stepped portion 24a of the second fixing groove 22h by the elastic means. As a result, one side porous material 22 and the other side porous material 24 may be combined. In addition, one side porous material 22 and the other side porous material 24 may be combined by various configurations in addition to the above configuration. In order for the second fixing pin 24f to be pushed inward more easily, the guide part 241f may be formed in the second fixing pin 24f.

9 to 11 are views for explaining the mesa shield method according to another embodiment of the present invention.

Referring to FIG. 9, in order to excavate earth and sand, a first support member 132, a second support member 134, a third support member 136, and a fourth support member 138 are installed. The support members 132, 134, 136, and 138 are installed in order to advance the mesa plate 110 in the excavation direction (arrow D direction) to excavate the tunnel, thereby preventing the tunnels which have already been excavated.

The first, second, third and fourth support members 132, 134, 136, and 138 may be composed of upper support members 132a, 134a, 136a, and 138a and side support members 132b, 134b, 136b, and 138b, respectively. have. The side support members 132b, 134b, 136b, and 138b are installed vertically on the ground with a pair of regular intervals, and the upper support members 132a, 134a, 136a, and 138b are installed on the upper surfaces of the pair of side support members. . In order to prevent the collapse of the excavated tunnel, support members other than the upper support members 132a, 134a, 136a, and 138a and the side support members 132b, 134b, 136b, and 138b may be further installed. It was.

As the support members 132, 134, 136, and 138, generally, I-beams or H-beams may be used.

The first and second upper support members 132a and 134a are provided with a porous material 122, and the level supports 152a and 152a between the pre-installed porous material 122 and the first and second upper support members 132a. 152b) and bracing members 142a and 142b may be disposed.

The mesa plate 110 has a plate shape formed long in the excavation direction. Mesa plate 110 may be composed of a head 112, the body 114 and the tail 116. A plurality of mesa plate 110 is arranged in parallel in the excavation direction is used for excavation of soil.

The mesa plate 110 is advanced in the tunnel excavation direction for the excavation of the tunnel. In the advancing process, the mesa plate 110 is in contact with the pre-installed porous material 122, the third upper support member 136a and the fourth upper support member 138a to be supported.

Unlike the conventional mesa shield method according to the present invention, in the advance of the mesa plate 110, the mesa plate 110 and the pre-installed porous material 122 in addition to the third and fourth upper support member (136a, 138a) and Contact. Therefore, load distribution is easy and frictional force between the mesa plate 110 and the third and fourth upper support members (136a, 138a) can be reduced.

A steel wire having a thin diameter such as a piano steel wire may be disposed in the tunnel excavation direction on the upper surface of the previously installed porous material 122. When the steel wire is disposed, the friction force between the mesa plate 110 and the pre-installed porous material 22 may be reduced.

The decrease in frictional force is due to a decrease in the contact area between the mesa plate 110 and the pre-installed porous material 122. That is, the decrease in the contact area is due to the increase in pressure at the contact surface between the mesa plate 110 and the pre-installed porous material 122, the increase in pressure is due to the increase in heat generation, the increase in heat generation is the decrease in the coefficient of friction As a result, the reduction of the friction coefficient leads to the decrease of the frictional force.

As a result, the mesa plate 110 may be more easily advanced by the load distribution and the reduction of the frictional force due to the steel wire.

The mesa plate 110 is advanced in the excavation direction until the end of the body portion 114 of the tail portion 116 abuts with the third upper support member 136a. At this time, a predetermined space is formed below the mesa plate 110.

Referring to FIG. 10, first and second level supports 154a and 154b are parallel to the second and third support members 134a and 136a on the second upper support member 134a and the third support member 136a, respectively. Is installed. The first and second level supports 154a and 154b may extend in the same direction as the second and third support members 134a and 136a.

First and second compression level bolt holes communicating with each other may be formed on the upper surface of the second upper support member 134a and the lower surface of the first level support 154a, respectively. The compression level bolts 155a may be inserted into the first and second compression level bolt holes.

The first level support 154a should be installed to prevent movement in the excavation direction of the tunnel, and the movement of the first level support 154a may be prevented by the insertion of the compression level bolt 155a.

The second level support 154b is not necessarily prevented from being moved as described above, but the same method as the first level support 154a is installed on the second upper support member 134a by the crimping level bolt 155a. By, it may be installed on the third upper support member (136a) by the compression level bolt (155b).

After the first and second level supports 154a and 154b are installed, the subsequent perforated material 124 is placed over the first and second level supports 154a and 154b. At this time, the subsequent porous material 124 is fixed to the first level support 154a, that is, fixedly installed so as not to move in the tunnel excavation direction. For this purpose, the locking projection 125 is formed at the end of the subsequent opposite hole 124 in the opposite direction to the excavation. The locking jaw 125 may have a shape that may be caught by the first level support 154a. In addition, one side edge of the first level support 154a may have a shape in which the locking step 125 may be caught. According to the shape, the subsequent porous material 124 may be disposed to be caught by the first level support 154a.

By the installation of the first level support 154a on the second upper support 134a and the placement of the subsequent restoration 124 on the first level support 154a, the subsequent restoration 124 is forced in the tunnel excavation direction. Even when receiving is not to move in the digging direction.

Referring to FIG. 11, after placing the subsequent porous material 124, the first and second level supports 154a and 154b are raised to move the subsequent porous material 124 to the tail portion 116 of the mesa plate 110. It adheres to the lower surface.

For the close contact, the screw level may be formed on the compression level bolts (155a, 155b). In addition, a screw line corresponding to the screw line may be formed in the first pressing level bolt hole of the second and third upper support members 134a and 136a. In this case, tightening the compression level bolts 155a and 155b raises the first and second level supports 154a and 154b so that the subsequent porous material 124 comes into close contact with the tail portion 116 of the mesa plate 110. do. Meanwhile, a thread line corresponding to a screw line of the compression level bolts 155a and 155b may be formed in the second compression level bolt holes of the first and second level supports 154a and 154b.

Meanwhile, as shown in FIG. 11, the first and second level supports 154a and 154b may have empty spaces formed therein, and unlike FIG. 11, empty spaces may not be formed therein. .

After raising the first and second level supports 154a and 154b, the support members 144a and 144b are provided with the first and second level supports 154a and 154b and the second and third upper support members provided thereunder. It may be disposed in the space between (134a, 136a). By arranging the bracing members 144a and 144b, the subsequent porous material 124 can more easily maintain the exact position in close contact with the lower surface of the tail 16.

After raising the subsequent porous material 124 or arranging the support members 144a and 144b, the earth and sand under the mesa plate 110 is excavated, and a fifth support material 140 is newly installed in the excavated space. The fifth support member 140 may be configured of the fifth upper and side support members 140a and 140b in the same manner as the pre-installed support members.

Thereafter, when the mesa plate 110 is advanced in the tunnel excavation direction, the mesa plate 110 is brought into contact with and supported by the subsequent porous material 124 and the fourth and fifth support members 138 and 140.

On the other hand, unlike the conventional case, when the mesa shield method according to the present invention is carried out, the interval (by the thickness of the tail portion 116 of the mesa plate 110) between the porous material (122, 124) and the ground of the upper portion ( Only D) remains. That is, as the porous materials 122 and 124 and the tail portion 161 are in close contact with each other and the tunnel is constructed, only an interval D corresponding to the thickness of the tail portion 116 is formed. Accordingly, settlement of the ground voids and the upper ground above the porous materials 122 and 124 can be minimized.

10, 110: mesa plate 22, 24: pre-installed porous material
122, 124: subsequent restoration material 32, 132: first support material
34, 134: Second support material 36, 136: Third support material
38, 138: 4th support material 40, 140: 5th support material

Claims (11)

Advancing a mesa plate in an excavation direction, wherein the mesa plate is in contact with and supported by a previously installed porous material and support material during the advancement process and upon completion of the advancement;
Disposing a subsequent porous material in a space formed at a lower end of the tail of the mesa plate;
Disposing the subsequent perforation in the space below the tail of the mesa plate,
Disposing a brace member between the subsequent porous material and the support material to keep the position in close contact with the lower surface of the mesa plate tail;
The subsequent porous material is arranged to be fixed to the pre-installed porous material to be in close contact with the lower surface of the mesa plate tail, but the retaining jaw on the opposite end side of the excavation in the excavation direction so that the subsequent porous material is impossible to move in the excavation direction Disposed on an edge of the member;
Excavating earth and sand under the advanced mesa plate; And
Installing a subsequent support in the excavated space;
Mesa shield method using a porous material comprising a. delete The method of claim 1,
Mesa shield method using a porous material in which the stepped surface corresponding to each other is formed on the contact surface of the pre-installed porous material and the subsequent porous material The method of claim 3, wherein
In the contact surface, the mesa shield method using a porous material in which the lower stepped portion is formed in the pre-installed porous material, the upper stepped portion is formed in the subsequent porous material. The method of claim 3, wherein
A horizontal contact surface is formed by the step,
Fixed pins and fixing grooves, or fixing grooves and fixing pins are formed on the horizontal contact surfaces of the pre-installed porous material and the subsequent porous material, respectively.
The fixing pin is a mesa shield method using a porous material is protruded from the horizontal contact surface by the elastic material is inserted into the fixing groove. Advancing the mesa plate in an excavation direction, wherein the mesa plate is in contact with and supported by a pre-installed porous material and support material;
Installing first and second level supports respectively on two rows of support members positioned at the bottom of the mesa plate tail, wherein the first level supports are installed to prevent movement in the excavation direction;
Disposing a subsequent perforated material on the first and second level supports, such that the engaging jaw formed at the opposite end of the excavated perforated material is caught by an edge of the first level support;
Raising the first and second level supports to adhere the subsequent porous material to the tail of the mesa plate;
Excavating earth and sand under the advanced mesa plate; And
Installing a subsequent support in the excavated space;
Mesa shield method using a porous material comprising a. The method of claim 6,
Disposing the subsequent porous material,
Mesa shield method using a porous material comprising the step of installing a support member between the first and second level support and the lower support material. The method of claim 6,
The first level support and the support material in the lower portion of the crimping level bolt hole is formed in communication,
Mesa shield method using a porous material comprising the step of inserting the compression level bolt into the compression level bolt hole. The method of claim 6,
First and second compression level bolt holes are formed in the first and second level support and the support material thereunder, respectively,
Mesa shield method using a porous material comprising the step of inserting the compression level bolt in the first and second compression level bolt hole, and tightening the compression level bolt to raise the first and second level support. The method of claim 6,
Contact support by the pre-installed porous material of the mesa plate,
Mesa shield method using a porous material formed by the tail portion of the mesa plate is in contact with the pre-installed porous material. The method of claim 6,
Mesa shield method using a porous material in which a steel wire is disposed in the excavation direction on the upper surface of the porous material.

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