Combined support method for roadway in high stress and extremely broken surrounding rock

Abstract

The application provides a combined supporting method for high-stress and extremely broken surrounding rock roadway, and belongs to the field of underground cavern excavation and supporting. The combined supporting first transfers the stress of extremely broken surrounding rock to the deep part through construction of pressure relief holes and pressure relief grooves, reduces stress concentration, then fills the pressure relief holes and pressure relief grooves, strengthens the support of extremely broken surrounding rock, arranges high-strength prestressed anchor cables and anchor rods of a plum-blossom-shaped anchoring system, strengthens the properties of surrounding rock, improves the self-bearing capacity of surrounding rock, finally carries out grouting and shotcrete sealing treatment, and further enhances the overall strength and bearing capacity of surrounding rock. The combined supporting method of "external support, medium strength and internal pressure relief" combines pressure relief, anchoring and grouting, combines external pressure relief and internal reinforcement, effectively controls the non-uniform deformation of the roof, sides and floor of the roadway, improves the stress distribution of extremely broken surrounding rock, avoids engineering disasters such as floor heave and spalling, and realizes the long-term stability and construction safety of high-stress and extremely broken surrounding rock roadway.

Description

Technical Field

[0001] This invention relates to the field of underground cavern excavation and support technology, specifically to a combined support method for tunnels with high stress and extremely fractured surrounding rock. Background Technology

[0002] Currently, with the continuous increase in mining depth, the engineering problems faced in deep tunnel excavation are becoming increasingly complex. Especially under high stress and extremely fractured surrounding rock conditions, the stability of the surrounding rock has become a key factor affecting construction safety and engineering efficiency. High-stress, extremely fractured surrounding rock often exhibits strong rock mass deformation, floor heave, spalling, roof collapse, and other instability phenomena. Traditional "anchor-mesh-shotcrete" support systems can no longer effectively meet the support requirements in such complex conditions.

[0003] Under conditions of extremely fractured surrounding rock, the rock strength decreases, its self-supporting capacity weakens, and stress concentration areas become more widespread and difficult to transfer, easily leading to rock failure and support failure. Furthermore, the deformation of surrounding rock under high stress is continuous and significant, making it difficult for existing support technologies to coordinate rock deformation with the mechanical properties of the support system, resulting in poor support effectiveness. Especially in cases of significant floor heave, the lack of effective floor support and pressure relief measures makes it difficult for traditional support systems to achieve overall reinforcement and stress release of the surrounding rock, significantly increasing the risk of tunnel deformation and failure.

[0004] The prior art discloses a method for the overall reinforcement and support of the surrounding rock in deep well roadways using rigid-flexible coupling anchor mesh. This method includes: first, spraying concrete onto the roadway cross-section to seal the surrounding rock; then, using steel mesh anchor rods to support the surrounding rock; and finally, installing anchor cables at the center of the top of the surrounding rock and at the arched shoulders on both sides, followed by spraying concrete again. After the roadway is excavated, grouting holes are constructed on the roadway roof and sidewalls. Grouting anchor rods are then installed in these holes, and cement grout is injected into the anchor rods. After excavating to a certain thickness downwards from the horizontal surface of the floor slab, sprayed concrete is used to form a grout-stopping layer. Finally, grouting holes and grouting anchor pipes are constructed on the floor slab rock mass to inject cement grout into the main slab. Concrete is then used to backfill the floor slab, forming a smooth concrete backfill layer, thus achieving overall support for the roadway and surrounding rock. Although this support method couples anchor bolts and cables and solves the problem of severe roadway heave by grouting the floor, it is still difficult to effectively control the non-uniform deformation of the roof, sides and floor under high stress conditions, and it is difficult to solve the problem of large stress concentration areas and difficult transfer under extremely fractured surrounding rock conditions. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a combined support method for roadways with high stress and extremely broken surrounding rock, which aims to solve the technical problems of poor support effect of existing support methods for roadways with high stress and extremely broken surrounding rock, and difficulty in solving the large range of stress concentration areas and the difficulty in transferring stress.

[0006] This application provides a combined support method for roadways with high stress and extremely fractured surrounding rock, comprising the following steps:

[0007] S1. After the tunnel is excavated under the condition of high stress and extremely broken surrounding rock, pressure relief holes and pressure relief grooves are constructed first. The pressure relief holes are located in the stress concentration area of ​​the surrounding rock around the tunnel. The excavation direction of the pressure relief holes is parallel to the direction of the tunnel. The pressure relief grooves are perpendicular to the bottom plate of the tunnel.

[0008] S2. After the pressure relief holes and pressure relief grooves are constructed, they are backfilled using filling technology.

[0009] S3. After the pressure relief holes and pressure relief grooves are filled, anchor bolts and high-strength prestressed anchor cables are arranged in the roadway wall facing the surrounding rock to form a plum blossom-shaped anchoring system.

[0010] S4. High-pressure grouting is performed on the surrounding rock using the high-strength prestressed anchor cables arranged in step S3. Finally, the surrounding rock of the roadway is treated with shotcrete to seal the surface of the surrounding rock, thereby achieving combined support for the roadway with high stress and extremely fractured surrounding rock.

[0011] In the technical solution of this application embodiment, a combined support method of "external support-medium strength-internal unloading" is used, combining pressure relief, anchoring, and grouting to coordinate the mechanical properties of the support structure and the surrounding rock, thereby achieving long-term stability and construction safety in high-stress, extremely fractured rock roadways. First, pressure relief holes and grooves are constructed to transfer stress in the extremely fractured surrounding rock to deeper layers, reducing stress concentration. Then, the pressure relief holes and grooves are filled to strengthen the support for the extremely fractured surrounding rock. Next, high-strength prestressed anchor cables and bolts are arranged to reinforce the properties of the surrounding rock and optimize the anchoring system. A quincunx anchoring system improves the self-supporting capacity of the surrounding rock. Finally, grouting and shotcrete sealing are performed to further enhance the overall strength and bearing capacity of the surrounding rock. The support method of this invention, by combining external pressure relief with internal reinforcement, can effectively control the non-uniform deformation of the roof, sides, and floor of the roadway, improve the stress distribution of the extremely fractured surrounding rock, and avoid engineering disasters such as floor heave and spalling.

[0012] In some embodiments, in step S1, the pressure relief holes are respectively located in the stress concentration areas of the surrounding rock at the top, bottom, and side walls of the roadway, and a borehole connecting the pressure relief holes and the roadway is provided. The radius of the pressure relief hole is 0.4-1.2m; the center distance of the pressure relief hole from the side walls of the roadway is 1.5-5m, and the distance from the top or bottom plate of the roadway is 2-8.5m. The borehole is located between two rows of anchor bolts, with a spacing of 1.0-1.5m between adjacent anchor bolts, and a diameter of 30-42cm. The borehole can be used to deliver explosives to the pressure relief holes where blasting is required.

[0013] In this embodiment, stress distribution is controlled by setting pressure relief holes parallel to the direction of the roadway in the stress concentration area of ​​the surrounding rock around the roadway. This allows the stress concentration area in the extremely fractured surrounding rock to shift unidirectionally to deeper surrounding rock, avoiding the problem of some stress shifting to the roadway surface when pressure relief holes are drilled from the roadway wall, which could easily cause instability in the roadway wall and the surrounding extremely fractured surrounding rock. This reduces damage and deformation of the surrounding rock surface. In addition, by setting small-diameter boreholes between the pressure relief holes and the roadway, it is more conducive to the dispersion of high stress, making the stress concentration less, and further solving the problem of large stress concentration area and difficulty in transfer.

[0014] In some embodiments, the pressure relief groove is located at the junction of the two sides of the roadway and the floor slab, and is perpendicular to the floor slab; the length of the pressure relief groove is the direction length of the roadway, the width of the pressure relief groove is 0.2 to 0.5 m, and the height is 0.8 to 1.2 m.

[0015] In this embodiment, constructing a pressure relief groove on the roadway floor can reduce the peak stress, thereby further reducing the impact of high stress on the roadway and effectively reducing the problems of floor heave and floor displacement.

[0016] In some embodiments, in step S3, the high-strength prestressed anchor cables are respectively installed at the upper and lower corners of the two sides of the roadway and on both sides of the roof. The high-strength prestressed anchor cables at the lower corners of the roadway are installed obliquely downwards, the high-strength prestressed anchor cables at the upper corners of the roadway are installed obliquely upwards, and the high-strength prestressed anchor cables on both sides of the roof are installed perpendicular to the roof of the roadway and upwards. The angle between the high-strength prestressed anchor cable at the lower corner of the roadway and the horizontal plane is greater than the angle between the high-strength prestressed anchor cable at the upper corner of the roadway and the horizontal plane. The anchor bolts are arranged in rows and evenly distributed on the two sides and the roof of the roadway, forming a staggered anchoring system with the high-strength prestressed anchor cables.

[0017] In this embodiment, by setting high-strength prestressed anchor cables and anchor rods, and arranging them together to form a quincunx-shaped anchoring system, a rigid and elastic coupled bearing arch is generated in the extremely fractured surrounding rock, improving the bearing capacity of the rock mass. By setting the arrangement direction of the high-strength prestressed anchor cables at the upper and lower corners, the anchor cables at the upper corners deeply anchor the roof, generating a strong suspension effect and forming continuous strong support points along the longitudinal axis of the roadway. The large prestress helps to alleviate the expansion of the floor and prevents the displacement of the floor. The anchor cables and anchor rods at the lower corners reinforce the stress concentration area at the corners and prevent shear slippage of the surrounding rock.

[0018] In addition, the subsequent anchor grouting process significantly improved the cohesion and internal friction angle of the joint surface (fracture surface), thereby increasing the overall strength and self-supporting capacity of the surrounding rock. At the same time, it reduced the stress concentration of the surrounding rock at the corner, avoiding premature failure of the corner and causing large deformation of the roadway sides and floor, thus effectively preventing or reducing floor heave. On the other hand, the anchor grouting support of the floor reinforces the loose and fractured zone of the roadway surrounding rock, enhances the integrity of the surrounding rock, and improves the rock mass strength and anchoring force of the anchor cables.

[0019] In some embodiments, in step S3, before arranging the anchor bolts and high-strength prestressed anchor cables, a steel mesh is used to provide overall support for the surrounding rock of the roadway; the high-strength prestressed anchor cables extend into the surrounding rock to a depth of 8-10m, and the anchor bolts extend into the surrounding rock to a depth of 1.5-3m.

[0020] In this embodiment, the high-stress, weak surrounding rock is loose and broken with poor anchorability. Therefore, it is necessary to consolidate the fractured surrounding rock to restore and improve its integrity and overall strength. With the support of steel mesh, the effective bearing capacity of the support structure can be expanded.

[0021] In some embodiments, the high-strength prestressed anchor cable at the lower corner of the roadway forms a 45° angle with the horizontal plane, and the high-strength prestressed anchor cable at the upper corner forms a 30° angle with the horizontal plane.

[0022] In some embodiments, in step S2, when filling the pressure relief hole, the slurry is fed from the initial tunneling face entrance of the pressure relief hole; when filling the pressure relief groove, the slurry is fed directly from the roadway.

[0023] In this embodiment, filling the pressure relief holes and pressure relief grooves after pressure relief is completed can reduce the probability of damage to the surrounding rock of the roadway and facilitate subsequent joint support work.

[0024] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0026] Figure 1This is a schematic diagram of the planar structure of the combined support method for a roadway with high stress and extremely fractured surrounding rock in the embodiments of this application;

[0027] Figure 2 This is a spatial structural schematic diagram of the combined support method for a roadway with high stress and extremely fractured surrounding rock in the embodiments of this application;

[0028] Figure 3 This is a distribution diagram of the mining stress field of Class IV surrounding rock under unsupported conditions in Embodiment 1 of this application;

[0029] Figure 4 This is a distribution diagram of the mining stress field of Class V surrounding rock in the unsupported state in Embodiment 1 of this application;

[0030] Figure 5 This is a diagram showing the horizontal displacement of a roadway in Class IV surrounding rock (with boreholes) in Embodiment 1 of this application;

[0031] Figure 6 This is a diagram showing the vertical displacement of the roadway under Class IV surrounding rock in Embodiment 1 of this application;

[0032] Figure 7 This is a diagram showing the horizontal displacement of a roadway in Class V surrounding rock (with boreholes) in Embodiment 1 of this application.

[0033] Figure 8 This is a diagram showing the vertical displacement of the roadway under Class V surrounding rock in Embodiment 1 of this application;

[0034] Figure 9 This is a diagram showing the stress distribution under the pressure relief measures of the combined support method for roadways in Class IV surrounding rock in Embodiment 1 of this application;

[0035] Figure 10 This diagram shows the stress distribution under the pressure relief measures of the combined support method for roadways in Class V surrounding rock in Embodiment 1 of this application.

[0036] Explanation of reference numerals in the attached drawings: 110-Pressure relief hole; 120-Pressure relief groove; 130-High-strength prestressed anchor cable; 140-Anchor rod; 150-Drill hole. Detailed Implementation

[0037] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0039] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0040] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0041] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0042] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0043] With the increasing depth of mining, the stability of surrounding rock in deep roadways under high stress and extremely fractured rock conditions has become a key factor affecting construction safety and engineering efficiency. High-stress, extremely fractured surrounding rock often exhibits strong rock mass deformation, floor heave, spalling, and roof collapse, among other instability phenomena. Traditional "anchor-mesh-shotcrete" support systems are no longer effective in meeting support requirements under such complex conditions. Under extremely fractured rock conditions, the rock strength decreases, its self-supporting capacity weakens, and stress concentration areas become more widespread and difficult to transfer, easily leading to rock failure and support failure. Furthermore, the deformation of surrounding rock under high stress is continuous and significant, making it difficult for existing support technologies to coordinate rock deformation with the mechanical properties of the support system, resulting in poor support effectiveness. Especially in cases of significant floor heave, the lack of effective floor support and pressure relief measures makes it difficult for traditional support systems to achieve overall reinforcement and stress release of the surrounding rock, significantly increasing the risk of roadway deformation and failure.

[0044] To address the technical problems of poor support effect and difficulty in resolving large stress concentration areas and transferring stress in existing support methods for roadways with high stress and extremely fractured surrounding rock, this application provides a combined support method for roadways with high stress and extremely fractured surrounding rock. This method combines external support, medium-strength reinforcement, and internal reinforcement, along with pressure relief, anchoring, and grouting, to coordinate the mechanical properties of the support structure and the surrounding rock, achieving long-term stability and construction safety for roadways with high stress and extremely fractured surrounding rock. This support method, through the combination of external pressure relief and internal reinforcement, can effectively control the non-uniform deformation of the roadway's roof, sides, and floor, improve the stress distribution of the extremely fractured surrounding rock, and avoid engineering disasters such as floor heave and spalling.

[0045] For ease of explanation, the following embodiments use a combined support method for a roadway with high stress and extremely fractured surrounding rock, according to an embodiment of this application, as an example.

[0046] Please refer to Figures 1-2 As shown in the figure, this application provides a combined support method for a roadway with high stress and extremely fractured surrounding rock, including the following steps:

[0047] S1. After the tunnel is excavated under the condition of high stress and extremely broken surrounding rock, the pressure relief hole 110 and pressure relief groove 120 are constructed first. The pressure relief hole 110 is located in the stress concentration area of ​​the surrounding rock around the tunnel. The excavation direction of the pressure relief hole 110 is parallel to the direction of the tunnel. The pressure relief groove 120 is perpendicular to the bottom plate of the tunnel.

[0048] S2. After the construction of the pressure relief hole 110 and the pressure relief groove 120 is completed, the two are backfilled using the filling technology.

[0049] S3. After the pressure relief holes 110 and pressure relief grooves 120 are filled, anchor bolts 140 and high-strength prestressed anchor cables 130 are arranged on the roadway wall to form a plum blossom-shaped anchoring system.

[0050] S4. High-pressure grouting is performed on the surrounding rock using the high-strength prestressed anchor cables 130 arranged in step S3. Finally, the surrounding rock of the roadway is treated with shotcrete to seal the surface of the surrounding rock, thereby achieving combined support for the roadway with high stress and extremely fractured surrounding rock.

[0051] This scheme employs a combined "external support-internal reinforcement-internal unloading" support method, integrating pressure relief, anchoring, and grouting to coordinate the mechanical properties of the support structure and the surrounding rock, achieving long-term stability and construction safety in high-stress, extremely fractured rock roadways. First, pressure relief holes 110 and grooves 120 are constructed to transfer stress from the extremely fractured rock to deeper layers, reducing stress concentration. Then, the pressure relief holes 110 and grooves 120 are filled to strengthen the support for the extremely fractured rock. Next, high-strength prestressed anchor cables 130 and anchor rods 140 are arranged to reinforce the surrounding rock properties and optimize the anchoring system. A quincunx anchoring system enhances the self-supporting capacity of the surrounding rock. Finally, grouting and shotcrete sealing are performed to further enhance the overall strength and bearing capacity of the surrounding rock. This support method, combining external pressure relief with internal reinforcement, effectively controls the non-uniform deformation of the roadway's roof, sides, and floor, improves the stress distribution of the extremely fractured rock, and avoids engineering disasters such as floor heave and spalling.

[0052] Furthermore, in some embodiments, in step S1, pressure relief holes 110 are respectively located in the stress concentration areas of the surrounding rock at the top, bottom, and sides of the roadway. A borehole 150 connects the pressure relief holes 110 and the roadway. The radius of the pressure relief holes 110 is 0.4–1.2 m, the center distance between the pressure relief holes 110 and the two sides of the roadway is 1.5–5 m, and the distance from the top or bottom plate of the roadway is 2–8.5 m. The borehole 150 is located between two rows of anchor bolts 140, with a spacing of 1.0–1.5 m between adjacent anchor bolts 140, and a diameter of 30–42 cm. The borehole 150 can be used to deliver explosives to the pressure relief holes 110 where blasting is required. In practice, when relieving pressure in certain extremely high stress areas, the pressure relief holes 110 can be appropriately blasted to improve their pressure relief range and effect.

[0053] In this embodiment, by setting pressure relief holes 110 parallel to the direction of the roadway in the stress concentration area of ​​the surrounding rock, the stress distribution is controlled. This allows the stress concentration area in the extremely fractured surrounding rock to shift unidirectionally to deeper surrounding rock, from near the roadway to near the pressure relief holes 110. This avoids the problem of some stress shifting to the roadway surface when pressure relief holes are drilled from the roadway wall, which could easily cause instability in the roadway wall and the surrounding extremely fractured surrounding rock, thereby reducing damage and deformation of the surrounding rock surface. In addition, by setting small-diameter boreholes 150 between the pressure relief holes 110 and the roadway, it is more conducive to the dispersion of high stress, making the stress concentration less, and further solving the problem of large stress concentration area and difficulty in transfer.

[0054] Furthermore, in some embodiments, the pressure relief groove 120 is located at the junction of the two sides of the roadway and the floor slab, and is perpendicular to the floor slab; the length of the pressure relief groove 120 is the length of the roadway, the width of the pressure relief groove 120 is 0.2 to 0.5 m, and the height is 0.8 to 1.2 m.

[0055] In the technical solution of this embodiment, the construction of a pressure relief groove 120 on the roadway floor can reduce the stress peak, thereby further reducing the impact of high stress on the roadway and effectively reducing the problems of floor heave and floor displacement.

[0056] Furthermore, in some embodiments, in step S3, high-strength prestressed anchor cables 130 are respectively installed at the upper and lower corners of the two sides of the roadway and at both sides of the roof. The high-strength prestressed anchor cables 130 at the lower corners of the roadway are installed obliquely downwards, the high-strength prestressed anchor cables 130 at the upper corners of the roadway are installed obliquely upwards, and the high-strength prestressed anchor cables 130 at both sides of the roof are installed perpendicular to the roadway roof and upwards. The angle between the high-strength prestressed anchor cables 130 at the lower corners of the roadway and the horizontal plane is greater than the angle between the high-strength prestressed anchor cables 130 at the upper corners of the roadway and the horizontal plane. Anchor bolts 140 are arranged in rows and evenly distributed at the two sides and the roof of the roadway, forming a staggered anchoring system with the high-strength prestressed anchor cables 130.

[0057] In this embodiment, by setting high-strength prestressed anchor cables 130 and anchor rods 140, and arranging them collaboratively to form a quincunx-shaped anchoring system, a rigid and elastic coupled bearing arch is generated in the extremely fractured surrounding rock, improving the bearing capacity of the rock mass. Furthermore, by setting the arrangement direction of the high-strength prestressed anchor cables 130 at the upper and lower corners, the anchor cables at the upper corners deeply anchor the roof, generating a strong suspension effect and forming continuous strong support points along the longitudinal axis of the roadway. This uses greater prestress to alleviate floor expansion and prevent floor displacement. Meanwhile, the anchor cables and anchor rods 140 at the lower corners reinforce the stress concentration area at the corners, preventing shear slippage of the surrounding rock. It should be noted that the spacing of the anchor rods 140, and the parameters of the anchor rods 140 and the high-strength prestressed anchor cables 130, can be determined based on different engineering conditions, such as the location of the stress concentration area.

[0058] In addition, the subsequent anchor grouting process significantly improved the cohesion and internal friction angle of the joint surface (fracture surface), thereby increasing the overall strength and self-supporting capacity of the surrounding rock. At the same time, it reduced the stress concentration of the surrounding rock at the corner, avoiding premature failure of the corner and causing large deformation of the roadway sides and floor, thus effectively preventing or reducing floor heave. On the other hand, the anchor grouting support of the floor reinforces the loose and fractured zone of the roadway surrounding rock, enhances the integrity of the surrounding rock, and improves the rock mass strength and anchoring force of the anchor cables.

[0059] Furthermore, in some embodiments, in step S3, before arranging the anchor bolts 140 and the high-strength prestressed anchor cables 130, a steel mesh is used to provide overall support for the surrounding rock of the roadway; the high-strength prestressed anchor cables 130 extend into the surrounding rock to a depth of 8 to 10 m, and the anchor bolts 140 extend into the surrounding rock to a depth of 1.5 to 3.0 m.

[0060] In the technical solution of this embodiment, the high-stress, weak surrounding rock is loose and broken with poor anchorability. Therefore, it is necessary to consolidate the fractured surrounding rock to restore and improve its integrity and overall strength. With the support of steel mesh, the effective bearing capacity of the support structure can be expanded.

[0061] Furthermore, in some embodiments, the high-strength prestressed anchor cable 130 at the lower corner of the roadway forms an angle of 45° with the horizontal plane, and the high-strength prestressed anchor cable 130 at the upper corner forms an angle of 30° with the horizontal plane.

[0062] Furthermore, in some embodiments, in step S2, when filling the pressure relief hole 110, the slurry is fed and filled from the initial tunneling face entrance of the pressure relief hole 110; when filling the pressure relief groove 120, the slurry is fed and filled directly from the roadway.

[0063] In the technical solution of this embodiment, the pressure relief hole 110 and pressure relief groove 120 are filled after the pressure relief is completed, which can reduce the probability of roadway surrounding rock damage and facilitate the subsequent joint support work.

[0064] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0065] Example 1

[0066] This embodiment provides a combined support method for roadways with high stress and extremely fractured surrounding rock, including the following steps:

[0067] S1. After excavation of the tunnel under high-stress and extremely fractured surrounding rock conditions, pressure relief holes and pressure relief grooves are constructed first. The pressure relief holes are located in the stress concentration areas of the surrounding rock around the tunnel, and the excavation direction of the pressure relief holes is parallel to the direction of the tunnel. The pressure relief grooves are set perpendicular to the bottom plate of the tunnel. Among them, the pressure relief holes are respectively located in the stress concentration areas of the surrounding rock at the top, bottom and side walls of the tunnel. There are boreholes connecting the pressure relief holes and the tunnel. The distance between the boreholes and the adjacent anchors is 1.0m and the diameter is 30cm. The pressure relief grooves are located at the junction of the two sides of the tunnel and the bottom plate.

[0068] S2. After the pressure relief holes and pressure relief grooves are constructed, they are backfilled using filling technology.

[0069] S3. After the pressure relief holes and grooves are filled, anchor bolts and high-strength prestressed anchor cables are arranged on the roadway walls against the surrounding rock to form a quincunx-shaped anchoring system. The high-strength prestressed anchor cables are located at the upper and lower corners of the roadway sides and on both sides of the roof. The high-strength prestressed anchor cables at the lower corners are set diagonally downwards, the high-strength prestressed anchor cables at the upper corners are set diagonally upwards, and the high-strength prestressed anchor cables on both sides of the roof are set perpendicular to the roadway roof and upwards. The angle between the high-strength prestressed anchor cables at the lower corners and the horizontal plane is 45°, and the angle between the high-strength prestressed anchor cables at the upper corners and the horizontal plane is 30°. The anchor bolts are evenly distributed on both sides of the roadway and on the roof. The high-strength prestressed anchor cables extend into the surrounding rock to a depth of 9m, and the anchor bolts extend into the surrounding rock to a depth of 2.2m.

[0070] S4. High-pressure grouting is performed on the surrounding rock using the high-strength prestressed anchor cables arranged in step S3. Finally, the surrounding rock of the roadway is treated with shotcrete to seal the surface of the surrounding rock, thereby achieving combined support for the roadway with high stress and extremely fractured surrounding rock.

[0071] To verify the feasibility of the above support methods, FLAC3D numerical simulation software was used to conduct corresponding simulations to compare the support effects of no support, original support (traditional anchor-mesh-spray support), and the combined support method of Example 1 (hereinafter referred to as combined support). The physical and mechanical parameters of fractured Class IV and Class V surrounding rock were selected to establish roadway models, obtaining relevant basic data of the roadway under Class IV and Class V surrounding rock parameters in the unsupported state.

[0072] Please see Figures 3-4 As shown, in Class IV surrounding rock, horizontal stress is mainly concentrated above the floor and roof of the roadway, approximately 2.64m and 3.08m from the inner wall of the roadway, respectively, while vertical stress is concentrated on both sides of the roadway, approximately 1.98m from the inner wall of the roadway. In Class V surrounding rock, horizontal stress is mainly concentrated above the floor and roof of the roadway, approximately 7.26m and 7.92m from the inner wall of the roadway, respectively, while vertical stress is approximately 4.18m from the inner wall of the roadway.

[0073] Based on the above analysis, a new tunnel model was established (reference). Figure 1 and Figure 2As shown in the figure, in Class IV surrounding rock, the pressure relief groove is 1m high and 0.3m wide, the radius of the pressure relief hole is 0.5m, and the distance from the center of the pressure relief hole to the two sides and the roof (bottom) is 1.98m and 2.64m respectively, which is consistent with the stress concentration area; in Class V surrounding rock, the pressure relief groove is also 1m high and 0.3m wide, the radius of the pressure relief hole is increased to 1m, and the distance from the center of the pressure relief hole to the two sides, the roof and the bottom are 4.18m, 7.26m and 7.92m respectively, which is also consistent with the stress concentration area; at the same time, according to the technical solution of Example 1, high-pressure grouting is performed in the area between the roadway floor and the broken surrounding rock.

[0074] Please see Figures 5-8 As shown, in Class IV surrounding rock, the displacements of the right sidewall (without support), the original support, and the combined support of the roadway are 40.55 mm, 33.67 mm, and 11.77 mm, respectively; the roof displacements are 44.04 mm, 14.23 mm, and 8.83 mm, respectively; and the floor displacements are 48.10 mm, 42.40 mm, and 15.61 mm, respectively. In Class V surrounding rock, the displacements of the right sidewall (without support), the original support, and the combined support of the roadway are 333.16 mm, 284.17 mm, and 52.52 mm, respectively; the roof displacements are 451.84 mm, 143.83 mm, and 40.46 mm, respectively; and the floor displacements are 419.25 mm, 312.63 mm, and 59.12 mm, respectively. The maximum displacement of the combined support is no longer distributed near the inner wall of the roadway, but appears near the pressure relief hole.

[0075] As can be seen from the figure, under Class IV surrounding rock parameters, traditional support methods cannot effectively control roadway deformation. Due to the lack of reinforcement measures for the floor, the deformation in the floor area is extremely large, with floor heave exceeding 40mm in Class IV surrounding rock and reaching 312mm in Class V surrounding rock. Under such large displacement, the roadway will experience large deformation, spalling, roof collapse, floor heave, and other engineering disasters, seriously threatening the safe and efficient mining. After adopting the combined support of Example 1 of this application, the bearing capacity of the surrounding rock near the roadway is significantly improved, and the surrounding rock of the roadway is effectively controlled. The maximum displacement of Class V surrounding rock no longer occurs near the inner wall of the roadway, but near the pressure relief hole. Centered on the roadway, the displacement shows a "large-small-large" characteristic, and the displacement of the roadway floor and sides is reduced, and the deformation of the extremely fractured rock mass is also effectively controlled.

[0076] Please see Figures 9-10The figures show the stress distribution under the combined support method and pressure relief measures in roadways of Class IV and V surrounding rock, respectively. As can be seen from the figures, in Class IV surrounding rock, the horizontal stress above the roof shifted backward by approximately 2 meters, and over a wider area, it was distributed more evenly behind the pressure relief holes, with the value decreasing from 75.31 MPa to 57.55 MPa. The horizontal stress below the floor shifted backward by approximately 1 meter, also over a wider area, and distributed more evenly behind the pressure relief holes. The vertical stress on both sides shifted backward by approximately 1 meter, over a wider area, with a tendency to shift upward, but the numerical value remained relatively unchanged. In Class V surrounding rock, the backward shift effect was more significant, generally about 1 meter further than in Class IV surrounding rock, with a reduced area. More stress was transferred to a small area deep within the surrounding rock, further reducing the impact of high stress on the roadway, and improving the stress state of the roadway in extremely fractured surrounding rock.

[0077] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A combined support method for a high-stress extremely broken surrounding rock roadway, characterized in that, The method comprises the following steps: S1, after the roadway is excavated in the condition of high stress and extremely broken surrounding rock, a pressure relief hole and a pressure relief groove are first constructed, the pressure relief hole is arranged in the stress concentration area of the surrounding rock around the roadway, the driving direction of the pressure relief hole is parallel to the trend of the roadway, and the pressure relief groove is arranged vertically to the floor of the roadway; S2, after the pressure relief hole and the pressure relief groove are constructed, the filling technology is used to backfill the pressure relief hole and the pressure relief groove; S3, after the pressure relief hole and the pressure relief groove are filled, the anchor rod and the high-strength prestressed anchor cable are arranged in the surrounding rock of the roadway wall, and a plum blossom-shaped anchoring system is formed; S4, the high-strength prestressed anchor cable arranged in step S3 is used for high-pressure grouting of the surrounding rock, and finally the surrounding rock of the roadway is treated by shotcrete to seal the surface of the surrounding rock, so that the combined support of the high-stress and extremely broken surrounding rock roadway is realized.

2. The combined support method of high stress extremely broken surrounding rock roadway according to claim 1, characterized in that, In step S1, the pressure relief holes are respectively arranged in the stress concentration areas of the surrounding rock outside the top, bottom and two sides of the roadway, and the drill holes connecting the pressure relief holes and the roadway are arranged between the pressure relief holes and the roadway.

3. The combined support method of high stress extremely broken surrounding rock roadway according to claim 2, characterized in that, The radius of the pressure relief hole is 0.4-1.2 m; the distance between the center of the pressure relief hole and the two sides of the roadway is 1.5-5 m, and the distance between the center of the pressure relief hole and the roof or floor of the roadway is 2-8.5 m.

4. The combined support method of high stress extremely broken surrounding rock roadway according to claim 1, characterized in that, The pressure relief groove is arranged at the junction of the two sides and the floor of the roadway and is arranged vertically to the floor; the length of the pressure relief groove is the length of the trend of the roadway, the width of the pressure relief groove is 0.2-0.5 m, and the height of the pressure relief groove is 0.8-1.2 m.

5. The combined support method of high stress extremely broken surrounding rock roadway according to claim 1, characterized in that, In step S3, the high-strength prestressed anchor cables are respectively arranged at the upper and lower corner positions of the two sides of the roadway and at the two sides of the roof, the high-strength prestressed anchor cable at the lower corner position of the two sides of the roadway is arranged obliquely downward, the high-strength prestressed anchor cable at the upper corner position of the two sides of the roadway is arranged obliquely upward, and the high-strength prestressed anchor cables at the two sides of the roof are arranged vertically to the roof of the roadway and upward; the angle between the high-strength prestressed anchor cable at the lower corner position of the two sides of the roadway and the horizontal plane is greater than the angle between the high-strength prestressed anchor cable at the upper corner position of the two sides of the roadway and the horizontal plane.

6. The combined support method of high stress extremely broken surrounding rock roadway according to claim 5, characterized in that, The anchor rods are arranged in rows and uniformly dispersed at the two sides and the roof of the roadway, and form a plum blossom-shaped anchoring system with the high-strength prestressed anchor cables.

7. The combined support method of high stress extremely broken surrounding rock roadway according to claim 2, characterized in that, The drill holes are arranged between the two rows of anchor rods, the distance between the drill holes and the adjacent anchor rods is 1.0-1.5 m, and the diameter of the drill holes is 30-42 cm; the drill holes can be used to convey explosives to the pressure relief holes that require blasting.

8. The combined support method of high stress extremely broken surrounding rock roadway according to claim 1, characterized in that, In step S3, before the anchor rods and the high-strength prestressed anchor cables are arranged, the surrounding rock of the roadway is supported by the steel mesh; the depth of the high-strength prestressed anchor cable extending into the surrounding rock is 8-10 m, and the depth of the anchor rod extending into the surrounding rock is 1.5-3 m.

9. The combined support method of high stress extremely broken surrounding rock roadway according to claim 5, characterized in that, The angle between the high-strength prestressed anchor cable at the lower corner position of the two sides of the roadway and the horizontal plane is 45°, and the angle between the high-strength prestressed anchor cable at the upper corner position of the two sides of the roadway and the horizontal plane is 30°.

10. The combined support method of high stress extremely broken surrounding rock roadway according to claim 1, characterized in that, In step S2, when the pressure relief hole is filled, the slurry is filled from the initial driving face of the pressure relief hole; when the pressure relief groove is filled, the slurry is directly filled from the roadway.

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