WO2024139800A1

WO2024139800A1 - Construction method for gas partition system of gas outburst tunnel

Info

Publication number: WO2024139800A1
Application number: PCT/CN2023/131556
Authority: WO
Inventors: 关瑞士; 郑仕跃; 王健安; 周刚; 王刚; 陈平; 李斌; 苏航
Original assignee: 中海建筑有限公司; 中建国际工程有限公司
Priority date: 2022-12-29
Filing date: 2023-11-14
Publication date: 2024-07-04
Also published as: CN115977686A

Abstract

A construction method for a gas partition system of a gas outburst tunnel, comprising: spraying concrete onto the current tunnel face that has been subjected to gas outburst prevention treatment so as to form a target tunnel face; conducting first-time grouting construction on the target tunnel face towards a target partition area, and then conducting first-time grouting construction on the target tunnel face towards the target partition area again; after the first-time grouting construction is completed, in the excavation direction of a tunnel, conducting excavation construction of an area to be excavated on the target tunnel face, so as to form a current tunnel section; in the current tunnel section, conducting second-time grouting construction on an area to be partitioned, so as to convert a geologic body in a preset distance range outside the tunnel contour line into a partition body; and using the partition body formed by part of the geological body outside a preliminary bracing layer to isolate gas in the geological body in a space outside the preliminary bracing layer. The construction method for a gas partition system of a gas outburst tunnel solves the defect in the prior art that gas gathered behind lining layers may enter passing tunnels by means of the leakage of tunnel secondary lining construction joints, causing large potential safety hazards.

Description

Construction method of gas isolation system in gas outburst tunnel

This application claims priority to Chinese patent application No. 202211711313.9 filed on December 29, 2022, the entire contents of which are incorporated by reference into this application.

Technical Field

The present application relates to the technical field of gas tunnel construction, and in particular to a construction method of a gas isolation system for a gas outburst tunnel.

Background technique

The purpose of anti-burst control for highway gas tunnels is to meet the requirements of tunnel construction safety and smooth excavation. When anti-burst control is carried out for gas tunnels, gas control is mainly carried out within a certain range of the outer contour of the tunnel, thereby ensuring that the tunnel construction is completed safely and smoothly under the premise that gas does not protrude during the construction phase. However, as the gas concentration in the treated area decreases, the gas in the untreated area will leak into the treated area, and at the same time, it will also leak into the gas tunnel through the treated area, affecting the safety performance of the tunnel.

In addition, conventional long and large tunnels generally adopt a herringbone slope. The gas accumulated in the tunnel first gathers at a high place inside the tunnel and then is discharged outside the tunnel. The gas is more likely to accumulate behind the lining. As the amount of gas accumulation increases, the gas accumulated behind the lining layer may leak into the tunnel through the construction joint of the second lining of the tunnel, posing a major safety hazard.

technical problem

The main purpose of this application is to provide a method for constructing a gas isolation system for a gas outburst tunnel, aiming to solve the technical problem that the gas accumulated behind the lining layer may leak into the tunnel through the construction joint of the tunnel secondary lining through relevant technologies, posing a major safety hazard.

Technical Solutions

To achieve the above objectives, in a first aspect, the present application proposes a construction method of a gas isolation system for a gas outburst tunnel, comprising the following steps:

The target tunnel face is formed by spraying concrete on the current tunnel face after gas outburst prevention and control is completed; wherein the minimum clear distance between the current tunnel face and the coal seam is the target distance;

The first grouting construction is performed on the target tunnel face toward the target isolation area; wherein the target isolation area includes an area to be excavated and an area to be isolated formed on the periphery of the area to be excavated, the area to be excavated is an area to be formed of the gas tunnel, and the area to be isolated is an area formed in a direction extending from the contour line of the gas tunnel to a first preset distance away from the contour line;

Along the excavation direction of the gas tunnel, excavation construction is performed on the target heading surface in the area to be excavated, so as to form a current tunnel section in the area to be formed;

Performing a second grouting construction on the area to be partitioned in the current tunnel section to obtain a partition body;

The partition body is supported and constructed in the current tunnel section.

In one embodiment, the step of performing a first grouting construction on the target tunnel face toward the target partition area includes:

Drilling at least two first grouting hole groups spaced apart along the radial direction of the gas tunnel in the target tunnel face toward the target isolation zone; wherein each of the first grouting hole groups includes at least two first grouting holes in an annular shape spaced apart along the circumference of the gas tunnel, and each of the first grouting holes extends in a direction away from the central axis of the gas tunnel;

Installing a first grouting pipe in all the first grouting holes; wherein one end of the first grouting pipe away from the coal seam extends out of the opening of the first grouting hole;

Performing plugging construction on the gaps between the inner walls of all the first grouting holes and the outer pipe walls of the corresponding first grouting pipes;

A first grouting construction is performed toward the target partition area through all the first grouting pipes with a first preset grouting parameter.

In one embodiment, the radial spacing between any two adjacent groups of the first grouting holes is C, wherein 2m≤C≤3m.

In one embodiment, in each of the first grouting hole groups, the distance between any two adjacent first grouting holes is gradually expanded in a direction away from the central axis of the gas tunnel.

In one embodiment, in each of the first grouting hole groups, the distance between the orifices of any two adjacent first grouting holes is A, and the distance between the bottoms of any two adjacent first grouting holes is B; wherein, 0.4m≤A≤0.6m, 2.8m≤B≤3.2m.

In one embodiment, the step of performing a first grouting construction toward the target partition area through all the first grouting pipes with the first preset grouting parameters includes:

Along a direction away from the central axis of the gas tunnel, a first grouting construction is performed toward the target partition area through the first grouting pipes in all the first grouting hole groups in sequence with a first preset grouting parameter.

In one embodiment, a gap to be blocked is formed between each of the first grouting holes and the corresponding first grouting pipe, and the gap to be blocked includes a first gap arranged on the outer wall of the first grouting pipe and a second gap arranged outside the first gap;

The step of sealing the gaps between the inner walls of all the first grouting holes and the outer walls of the corresponding first grouting pipes comprises:

Performing plugging construction on all the first gaps;

All the second gaps are sealed.

In one embodiment, after the step of sealing all the second gaps, the method further includes:

The first pipe opening of the first grouting pipe is welded by using a steel plate; wherein the first pipe opening is formed at one end of the first grouting pipe extending out of the opening of the first grouting hole;

Welding a faucet with a preset pipe diameter on the steel plate;

A hole is drilled on the steel plate to form a grouting port connecting the faucet with the first grouting pipe.

In one embodiment, the step of performing a second grouting construction on the area to be partitioned in the current tunnel section to obtain a partition body comprises:

Drilling at least two second grouting hole groups spaced apart along the excavation direction of the gas tunnel in the current tunnel section toward the area to be isolated; wherein each of the second grouting hole groups includes at least two second grouting holes in an annular shape spaced apart along the circumference of the gas tunnel, and each of the second grouting holes extends in a direction away from the central axis of the current tunnel section;

Installing a small conduit in each of the second grouting holes;

The openings of all the second grouting holes are sealed and a second grouting construction is carried out toward the area to be isolated through the second grouting pipe.

In one embodiment, the step of plugging the openings of all the second grouting holes and performing a second grouting construction toward the area to be isolated through the second grouting pipe includes:

Performing plugging construction on the gaps between the inner walls of all the second grouting holes and the outer walls of the corresponding second grouting pipes;

A second grouting construction is performed toward the area to be isolated through the second grouting pipe with a second preset grouting parameter.

Beneficial Effects

The technical solution of the present application forms a target face by spraying concrete on the current face after gas burst prevention and control has been completed, and then performs the first grouting construction on the target face toward the target partition area, and then performs the first grouting construction on the target face toward the target partition area. After completing the first grouting construction, excavation construction is carried out on the target face in the area to be excavated along the excavation direction of the tunnel to form the current tunnel section, and the second grouting construction is carried out on the area to be excavated in the current tunnel section to obtain a partition body, and then support construction is carried out on the current tunnel section, so that the present application can convert the geological body within a preset distance range outside the tunnel contour line into a partition body by means of secondary grouting during specific implementation, and then the present application can use the partition body formed by part of the geological body outside the initial support layer to isolate the gas in the geological body in the space outside the initial support layer during specific implementation, and thus the present application solves the defect in the related technology that the gas accumulated behind the lining layer may enter the passage tunnel through the leakage of the construction joint of the second lining of the tunnel, posing a great safety hazard.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

FIG1 is a flow chart of a construction method of a gas isolation system for a gas outburst tunnel according to an example of the present application;

FIG. 2 is a detailed flow chart of step S200 of the example in FIG. 1 ;

FIG3 is a detailed flow chart of step S240 of the example in FIG2 ;

FIG4 is a flow chart of step S400 of the example in FIG3 ;

FIG5 is a flow chart of step S430 of the example in FIG1 ;

FIG6 is a schematic diagram of the structure of the geological structure of a gas tunnel according to an example of the present application;

FIG7 is a schematic diagram of the reinforcement of the geological structure shown in FIG6;

FIG. 8 is a schematic diagram of the planar structure of the reinforcement area exemplified in the present application.

The purpose, features and advantages of this application will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Embodiments of the present invention

The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various mechanisms under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and/or" appearing in the full text includes three parallel schemes. Taking "A and/or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

The application concept of the present application is further explained below in conjunction with some specific implementation methods.

The present application provides a construction method of a gas isolation system for a gas outburst tunnel.

As shown in FIG. 1 to FIG. 8 , an embodiment of a construction method of a gas isolation system for a gas outburst tunnel of the present application is proposed.

In this embodiment, referring to FIG. 1 , the construction method of the gas isolation system of the gas outburst tunnel includes the following steps:

S100, spraying concrete on the current tunnel face after gas outburst prevention and control to form a target tunnel face; wherein the minimum clear distance between the current tunnel face and the coal seam is the target distance;

In this embodiment, during the specific implementation, the gas tunnel is first excavated to the current face, wherein the minimum clear distance between the current face and the coal seam is the target distance, and the geological body is prevented from bursting through the current face, and then the current face is sprayed with concrete of at least C20 for at least 20 cm to form the target face.

It should be particularly and clearly stated that, in this embodiment, the minimum clear distance is 10 m, and the C20 concrete can be, but is not limited to, fine stone concrete.

S200, performing a first grouting construction on the target tunnel face toward the target isolation area; wherein the target isolation area includes an area to be excavated and an area to be isolated formed on the periphery of the area to be excavated, the area to be excavated is an area to be formed of the gas tunnel, and the area to be isolated is an area formed extending from the contour line of the gas tunnel in a direction away from the contour line by a first preset distance;

In this embodiment, the slurry used when performing the first grouting construction on the target tunnel face toward the target partition area may be, but is not limited to, a single cement slurry with a cement:water ratio of 1:1.

It should be particularly and clearly stated that the first preset distance in this embodiment is 6 m.

S300, along the excavation direction of the gas tunnel, excavation construction is performed on the target heading surface in the area to be excavated, so as to form a current tunnel section in the area to be formed;

In this embodiment, the excavation construction scheme adopted when excavating the tunnel is the same as the scheme for excavating the gas tunnel in the related art. After the excavation is completed, the tunnel is initially supported to form the current tunnel section.

It should be particularly and clearly stated that, in the present embodiment, the exemplified excavation construction process may be, but is not limited to, excavation construction carried out in a cyclic advancement manner. Specifically, excavation of two meters is considered a cycle. After each two meters of excavation, initial support construction is carried out. After the initial support construction is completed, the next cyclic advancement excavation construction is carried out.

S400, performing a second grouting construction in the area to be partitioned in the current tunnel section to obtain a partition body;

In this embodiment, the slurry used in the second grouting construction can be, but is not limited to, a single cement slurry with a cement:water ratio of 1:1.

S500. Carry out support construction on the partition body in the current tunnel section.

In this embodiment, the support construction for the current tunnel section mainly involves constructing a secondary lining layer and a gas isolation layer of the partition body in the current tunnel section.

In some specific embodiments, the step of performing a first grouting construction on the target tunnel face toward the target isolation area includes:

S210, drilling at least two first grouting hole groups spaced apart along the radial direction of the gas tunnel in the target tunnel face toward the target isolation zone; wherein each first grouting hole group includes at least two first grouting holes in an annular shape spaced apart along the circumference of the gas tunnel, and each first grouting hole extends in a direction away from the central axis of the gas tunnel;

In this embodiment, when drilling, it is necessary to ensure that the angle between each first grouting hole and the central axis of the gas tunnel is the same, and they are gradually expanded along the excavation direction of the gas tunnel in the direction away from the central axis of the gas tunnel.

It should be particularly and clearly stated that, in this embodiment, the angle between the first grouting hole and the central axis of the gas tunnel can be ±30°.

In an exemplary technology, the process of determining the angle of the first grouting hole is: determined according to the setting length L of the first grouting hole and the spacing X between two adjacent grouting holes, and exemplary, obtained by a sinusoidal function between the length L and the spacing X.

S220, installing a first grouting pipe in all the first grouting holes; wherein one end of the first grouting pipe away from the coal seam extends out of the opening of the first grouting hole;

In this embodiment, the diameter of the first grouting pipe installed in the first grouting hole is at least 108 mm.

S230, performing plugging construction on the gaps between the inner walls of all first grouting holes and the outer walls of the corresponding first grouting pipes;

In this embodiment, when the gap between the inner wall of the first grouting hole and the outer wall of the corresponding first grouting pipe is plugged, an anchoring agent can be used for the first plugging, and when the plugging is completed, a gap of about 1 cm is reserved between the inner wall of the first grouting hole and the outer wall of the corresponding first grouting pipe. After the anchoring agent solidifies, cotton yarn and cement mortar or AB glue are used to plug the orifice until the plugging construction is completed, and then a 6m steel plate is used to weld the exposed 108 orifice pipe, and a 4cm diameter grouting faucet is welded on the steel plate as the grouting port until the plugging construction is completed. Through the exemplified plugging construction method, the present application can ensure that the slurry will not seep out of the gap during the grouting construction process during the specific implementation, so that the slurry can be completely filled in the cracks or gaps in the geological body, thereby improving the gas isolation effect of the target isolation area.

S240, performing the first grouting construction toward the target partition area through all first grouting pipes with the first preset grouting parameters.

In this embodiment, by using the first grouting pipe to perform grouting construction on the target isolation area under the first preset grouting parameters, the present application can ensure that the gaps or cracks in the entire target isolation area are completely filled with slurry during specific implementation, thereby ensuring the isolation effect of the entire target isolation area on gas.

It should be particularly and clearly stated that in this embodiment, the first preset grouting parameters of the example are 0.5-1.0MPa initial grouting pressure and 2.0MPa final pressure; the slurry diffusion radius is 2m. The specific grouting process is to define multiple first grouting hole groups from inside to outside as the first first grouting hole group, the second first grouting hole group, the third first grouting hole... the Nth first grouting hole group, and then sequentially perform grouting construction on the target partition area through the first first grouting hole group, the second first grouting hole group, the third first grouting hole... the Nth first grouting hole group until the grouting construction of the entire target partition area is completed.

In some specific embodiments, the radial spacing between any two adjacent first grouting hole groups is C, wherein 2m≤C≤3m.

In this embodiment, the radial spacing between any two adjacent first grouting hole groups is set to C, and the value of C is 2m to 3m, so that when the present application is implemented, it can be ensured that the entire target partition area can be injected with slurry, and the slurry will not be wasted.

In some specific embodiments, in each first grouting hole group, the distance between any two adjacent first grouting holes is gradually expanded in the direction away from the central axis of the gas tunnel.

In this embodiment, the distance between any two adjacent first grouting holes is gradually expanded in the direction away from the central axis of the gas tunnel, so that when the present application is implemented, it can ensure that each area in the target isolation area composed of the area to be isolated and the area to be excavated can be injected with slurry, thereby improving the isolation range of the target isolation area.

In some specific embodiments, in each first grouting hole group, the distance between the orifices of any two adjacent first grouting holes is A, and the distance between the bottoms of any two adjacent first grouting holes is B; wherein, 0.4m≤A≤0.6m, 2.8m≤B≤3.2m.

In this embodiment, by setting the spacing between the openings of any two adjacent first grouting holes to 0.4m to 0.6m, and the spacing between the bottoms of any two adjacent first grouting holes to 2.8m to 3.2m, the present application can ensure that the grouting range of the entire target isolation zone is a gradually expanding table-like structure from the target face along the excavation direction of the gas tunnel during specific implementation, so that the present application can enhance the isolation range of the entire target isolation zone during specific implementation.

In some specific embodiments, the step of performing a first grouting construction toward the target partition area through all first grouting pipes with a first preset grouting parameter includes:

S240, along the direction away from the central axis of the gas tunnel, perform the first grouting construction toward the target partition area through the first grouting pipes in all the first grouting hole groups in sequence with the first preset grouting parameters.

In some specific embodiments, a gap to be blocked is formed between each first grouting hole and the corresponding first grouting pipe, and the gap to be blocked includes a first gap arranged on the outer wall of the first grouting pipe and a second gap arranged outside the first gap;

The step of sealing the gaps between the inner walls of all first grouting holes and the outer walls of the corresponding first grouting pipes comprises:

S241, sealing all first gaps;

In this embodiment, when the first gap is sealed, an anchoring agent is mainly used for the sealing.

S242. Perform sealing construction on all second gaps.

In this embodiment, when the second gap is sealed, cotton yarn and cement mortar or AB glue are mainly used to seal the hole until the sealing construction is completed.

It should be particularly and clearly stated that, in this embodiment, the spacing of the second gap is about 1 cm.

In some specific embodiments, after the step of sealing all the second gaps, the method further includes:

S243, welding a first pipe opening of a first grouting pipe with a steel plate; wherein the first pipe opening is formed at one end of the first grouting pipe extending out of the opening of the first grouting hole;

S244, welding a faucet with a preset pipe diameter onto a steel plate;

S245. Drill a hole on the steel plate to form a grouting port that connects the faucet with the first grouting pipe.

In this embodiment, by welding steel plates and welding faucets on the steel plates, the present application can ensure that during the grouting of the target partition area through the first grouting pipe, the slurry will be evenly injected into the gaps or cracks in the geological body of the target partition area.

In some specific embodiments, the step of performing a second grouting construction on the area to be partitioned in the current tunnel section to obtain a partition body includes:

S410, drilling at least two second grouting hole groups spaced apart along the excavation direction of the gas tunnel in the current tunnel section toward the area to be isolated; wherein each second grouting hole group includes at least two second grouting holes in an annular shape spaced apart along the circumference of the gas tunnel, and each second grouting hole extends in a direction away from the central axis of the current tunnel section;

In this embodiment, by setting a radial second grouting hole group, the present application can seal the gaps or cracks created during the excavation construction process during specific implementation, thereby forming an integral partition structure for the entire area to be partitioned.

It should be particularly and clearly stated that, in this embodiment, the spacing between the second grouting hole groups is at least 2 m: the circumferential spacing between any two adjacent second grouting holes is at least 2 m:

S420, installing a small conduit in each second grouting hole;

In this embodiment, holes are formed in the surrounding rock due to measures such as anchor rods, locking anchor rods or advance support in the initial support construction system of the tunnel; gaps are formed due to the fact that the initial support shotcrete is not completely close to the surrounding rock; and cracks are formed in the surrounding rock due to the convergence deformation and settlement of the surrounding rock. Small-duct grouting is used to perform small-duct grouting on the shotcrete and the surrounding rock behind it to a certain depth, and cement slurry is used to close these cracks or holes and block the gas overflow channel.

S430, sealing the openings of all second grouting holes and performing a second grouting construction toward the area to be isolated through the second grouting pipe.

In some specific embodiments, the steps of sealing the openings of all second grouting holes and performing a second grouting construction toward the area to be isolated through the second grouting pipe include:

S431, performing plugging construction on the gaps between the inner walls of all second grouting holes and the outer walls of the corresponding second grouting pipes;

In this embodiment, it is necessary to particularly and clearly explain that the plugging construction process of the example is the same as the plugging construction process of the first grouting hole and the first grouting pipe, and will not be repeated here.

S432, performing a second grouting construction toward the area to be isolated through a second grouting pipe with a second preset grouting parameter.

In some specific embodiments, there are also a large number of cracks in the tunnel surrounding rock; gas outburst prevention measures such as drainage drilling, hydraulic cutting or hydraulic fracturing form holes or cracks in the coal seam; the initial support construction system of the tunnel, anchor rods, locking anchor rods or advance support measures form holes in the surrounding rock; the gaps formed by the injection soil and the surrounding rock are not completely close together; cracks will also form in the rock mass due to the convergence deformation and settlement of the surrounding rock. These cracks or gaps are channels for gas to overflow into the tunnel. The main purpose of gas outburst control is to ensure that gas no longer outbursts during the tunnel construction stage, but during the tunnel opening and operation stage, under the action of gas pressure and concentration gradient difference, gas moves into the tunnel along cracks or holes, and may penetrate into the tunnel, posing a major safety hazard.

The purpose of this application is to seal cracks or holes by taking technical measures, consolidate the surrounding rock and coal seam into a whole within a certain range outside the tunnel excavation contour line, form a barrier, isolate the gas outside the circle, and prevent it from infiltrating or infiltrating less behind the tunnel lining.

The coal seam of a certain tunnel has a prominent danger. During the construction, a large number of holes were drilled in the rock pillars within 5-6m of the outer contour of the tunnel excavation, and hydraulic slitting and cutting were used to form countless cracks and holes in the coal seam, so as to drain and control the gas. Before the coal seam was excavated, the rock mass and coal seam within 6m outside the tunnel excavation contour line, 10m close to the coal seam group and 10m away from the coal seam group, were reinforced by deep hole curtain grouting. The cracks in the surrounding rock, the gaps and holes formed by gas control were filled with cement slurry to solidify the rock mass and coal seam.

After the tunnel has completed the treatment of the outburst, after the tunnel has completed the support shotcrete construction, but before the construction of the gas isolation board, radial small pipe grouting is used to close the cracks or holes formed in the rock mass. Through two rounds of grouting, a circle of integral surrounding rock mass is formed within 6m behind the tunnel lining, isolating the gas from penetrating into the lining clearance.

S10: After the gas outburst in Tianchengba Tunnel was controlled, the face 21 was 10m away from the normal line of the coal seam, and 20cm thick C25 shotcrete was used to completely seal the face.

S20: After the closure is completed, 4 rings of grouting holes are set in the Zhangzi. The grouting holes are arranged in an umbrella shape from the heading to the center line of the tunnel. The circumferential spacing between the grouting holes is 50cm, the spacing between each ring is about 2m, and the spacing between the hole bottoms is not more than 3m; 3 rings of grouting pipe holes are set longitudinally, and the grouting section is 30m long, divided into 3 rings, the first ring is 12m long, the second ring is 20m long, and the third ring is 30m long. After the grouting of the first section is completed, no excavation is done to serve as the grouting stop rock plate for the next section.

Curtain grouting consolidation and sealing is achieved within 6m outside the tunnel excavation contour line.

S30: The borehole diameter is 115, and a 108 seamless steel pipe is buried in the borehole as the orifice pipe. The orifice pipe is 3m long and exposed 20-30cm outside the face.

S40: After the orifice pipe is buried, use anchoring agent to seal the air between the orifice pipe and the shotcrete, leaving a gap of about 1 cm, and then use cotton yarn and cement mortar or AB glue to seal the orifice. After the orifice is partially solidified, use 6m steel plate to weld the exposed 108 orifice pipe, and use a 4cm diameter grouting tap welded to the steel plate as the grouting port.

S50: Grouting, grouting from inside to outside according to the construction, each ring is grouting from the bottom of the invert arch to the top of the arch in a symmetrical order from both sides of the tunnel, and the grouting adopts 1:1 cement single liquid slurry, the initial grouting pressure is 0.5-1.0MPa, and the final pressure is 2.0MPa; the slurry diffusion radius is 2m. After the first ring of grouting is completed, the second ring, then the third ring and the fourth ring are applied.

S60: After the coal seam is reinforced and solidified, the coal seam is uncovered by progressive coal uncovering. After every 26m of coal seam uncovering, the second round of curtain grouting is carried out. This sequence is repeated until the curtain grouting is 10m away from the normal line of the coal seam, and no more curtain grouting is carried out.

S70: When the initial support of the invert is completed, the surrounding rock converges horizontally and the arch crown settlement is stable, the initial support back grouting is started. The initial support back grouting length section is defined as the length range from 10m close to the coal seam normal and 10m away from the normal after the coal is uncovered.

S80: Grouting behind the initial support, the grouting sequence is from the bottom of the invert to the side wall and the arch, until it is completed away from the normal line of the coal seam.

The grouting ring is arranged perpendicular to the treatment support surface, with a radial length of no less than 6m along the tunnel, one ring every 2m along the tunnel extension direction, and a 2m spacing along the tunnel inner contour direction. The grouting sequence is to grout the inverted arch first, and then gradually grout and solidify along the tunnel side wall to the arch top, reinforcing the rock mass solidified in the first stage.

S90: This application can carry out curtain grouting and radial grouting reinforcement around the tunnel contour line, close the cracks and holes in the coal seam and surrounding rock, block the gas overflow channel, and achieve the effect of isolating external gas. Isolating the gas 6m away from the tunnel excavation contour line can improve the stability coefficient of the coal seam, ensure the safety of tunnel construction, and reduce safety hazards in tunnel operation.

The technical solution of the present application forms a target face by spraying concrete on the current face after gas burst prevention and control has been completed, and then performs the first grouting construction on the target face toward the target partition area, and then performs the first grouting construction on the target face toward the target partition area. After the first grouting construction is completed, excavation construction is performed on the target face in the area to be excavated along the excavation direction of the tunnel to form the current tunnel section, and the second grouting construction is performed on the partition area to be treated in the current tunnel section to obtain a partition body, and then support construction is performed on the current tunnel section, so that the present application can be implemented in practice. Through the secondary grouting method, the geological body within a preset distance outside the tunnel contour line is converted into a partition body, so that when the present application is implemented, the partition body formed by part of the geological body outside the initial support layer can be used to isolate the gas in the geological body in the space outside the initial support layer. Therefore, when the present application is implemented, it solves the defect in the related technology that there is a high possibility of gas accumulation behind the lining. As the gas accumulation amount increases, the continuous gas accumulation may leak into the tunnel through the construction joint of the second lining of the tunnel, posing a great safety hazard.

The above descriptions are only some embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structural changes made using the contents of the present application specification and drawings under the application concept of the present application, or direct/indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

A construction method of a gas isolation system for a gas outburst tunnel, comprising the following steps:

The target tunnel face is formed by spraying concrete on the current tunnel face after gas outburst prevention and control is completed; wherein the minimum clear distance between the current tunnel face and the coal seam is the target distance;

The first grouting construction is performed on the target tunnel face toward the target isolation area; wherein the target isolation area includes an area to be excavated and an area to be isolated formed on the periphery of the area to be excavated, the area to be excavated is an area to be formed of the gas tunnel, and the area to be isolated is an area formed in a direction extending from the contour line of the gas tunnel to a first preset distance away from the contour line;

Along the excavation direction of the gas tunnel, excavation construction is performed on the target heading surface in the area to be excavated, so as to form a current tunnel section in the area to be formed;

Performing a second grouting construction on the area to be partitioned in the current tunnel section to obtain a partition body;

The partition body is supported and constructed in the current tunnel section.
The construction method of the gas isolation system of the gas outburst tunnel according to claim 1, wherein the step of performing the first grouting construction on the target tunnel face toward the target isolation area comprises:

Drilling at least two first grouting hole groups spaced apart along the radial direction of the gas tunnel in the target tunnel face toward the target isolation zone; wherein each of the first grouting hole groups includes at least two first grouting holes in an annular shape spaced apart along the circumference of the gas tunnel, and each of the first grouting holes extends in a direction away from the central axis of the gas tunnel;

Installing a first grouting pipe in all the first grouting holes; wherein one end of the first grouting pipe away from the coal seam extends out of the opening of the first grouting hole;

Performing plugging construction on the gaps between the inner walls of all the first grouting holes and the outer pipe walls of the corresponding first grouting pipes;

A first grouting construction is performed toward the target partition area through all the first grouting pipes with a first preset grouting parameter.
The construction method of the gas isolation system of the gas outburst tunnel as described in claim 2, wherein the radial spacing between any two adjacent groups of the first grouting holes is C; wherein 2m≤C≤3m.
The construction method of the gas isolation system of the gas outburst tunnel as described in claim 2, wherein, in each of the first grouting hole groups, the distance between any two adjacent first grouting holes is gradually expanded in the direction away from the central axis of the gas tunnel.
The construction method of the gas isolation system of the gas outburst tunnel as described in claim 4, wherein, in each of the first grouting hole groups, the distance between the orifices of any two adjacent first grouting holes is A, and the distance between the bottoms of any two adjacent first grouting holes is B; wherein, 0.4m≤A≤0.6m, 2.8m≤B≤3.2m.
The construction method of the gas isolation system of the gas outburst tunnel according to claim 2, wherein the step of performing the first grouting construction toward the target isolation area through all the first grouting pipes with the first preset grouting parameters comprises:

Along a direction away from the central axis of the gas tunnel, a first grouting construction is performed toward the target partition area through the first grouting pipes in all the first grouting hole groups in sequence with a first preset grouting parameter.
The construction method of the gas isolation system of the gas outburst tunnel according to claim 6, wherein a gap to be blocked is formed between each of the first grouting holes and the corresponding first grouting pipe, and the gap to be blocked includes a first gap arranged on the outer wall of the first grouting pipe and a second gap arranged outside the first gap;

The step of sealing the gaps between the inner walls of all the first grouting holes and the outer walls of the corresponding first grouting pipes comprises:

Performing plugging construction on all the first gaps;

All the second gaps are sealed.
The method for constructing a gas isolation system for a gas outburst tunnel according to claim 7, wherein, after the step of sealing all the second gaps, it further comprises:

The first pipe opening of the first grouting pipe is welded by using a steel plate; wherein the first pipe opening is formed at one end of the first grouting pipe extending out of the opening of the first grouting hole;

Welding a faucet with a preset pipe diameter on the steel plate;

A hole is drilled on the steel plate to form a grouting port connecting the faucet with the first grouting pipe.
The construction method of the gas isolation system of the gas outburst tunnel according to any one of claims 1 to 8, wherein the step of performing a second grouting construction on the area to be isolated in the current tunnel section to obtain the isolation body comprises:

Drilling at least two second grouting hole groups spaced apart along the excavation direction of the gas tunnel in the current tunnel section toward the area to be isolated; wherein each of the second grouting hole groups includes at least two second grouting holes in an annular shape spaced apart along the circumference of the gas tunnel, and each of the second grouting holes extends in a direction away from the central axis of the current tunnel section;

Installing a small conduit in each of the second grouting holes;

The openings of all the second grouting holes are sealed and a second grouting construction is carried out toward the area to be isolated through the second grouting pipe.
The construction method of the gas isolation system of the gas outburst tunnel according to claim 9, wherein the step of sealing the openings of all the second grouting holes and performing a second grouting construction toward the area to be isolated through the second grouting pipe comprises:

Performing plugging construction on the gaps between the inner walls of all the second grouting holes and the outer walls of the corresponding second grouting pipes;

A second grouting construction is performed toward the area to be isolated through the second grouting pipe with a second preset grouting parameter.