Combined supporting method for high-stress extremely-broken surrounding rock roadway

Abstract

The invention provides a combined supporting method for a high-stress extremely-broken surrounding rock roadway, and belongs to the field of underground cavern excavation supporting. According to combined supporting, firstly, pressure relief holes and pressure relief grooves are constructed, the stress of extremely-broken surrounding rock is transferred to the deep part, stress concentration is reduced, then the pressure relief holes and the pressure relief grooves are filled, and the pressure relief holes and the pressure relief grooves are filled; and then high-strength pre-stressed anchor cables and anchor rods of a quincunx anchoring system are arranged, the property of the surrounding rock is strengthened, the self-bearing capacity of the surrounding rock is improved, and finally grouting and concrete spraying sealing treatment is conducted, so that the overall strength and bearing capacity of the surrounding rock are further enhanced. According to the method, an external supporting-medium strength-internal unloading combined supporting method is adopted, pressure relief, anchoring and grouting are combined, external pressure relief and internal reinforcement are combined, non-uniform deformation of a top plate, an upper portion and a bottom plate of a roadway is effectively controlled, stress distribution of extremely-broken surrounding rock is improved, and engineering disasters such as floor heave and wall caving are avoided; and long-term stability and construction safety of the high-stress extremely-broken surrounding rock roadway are realized.

Description

Technical Field

[0001] The invention relates to the technical field of underground cave excavation support, and in particular to a combined support method for a high-stress and extremely broken surrounding rock tunnel. Background Art

[0002] At present, with the continuous increase in mining depth, the engineering problems faced by deep tunnel excavation are becoming increasingly complex, especially under the conditions of high stress and extremely broken surrounding rock, the stability of tunnel surrounding rock has become a key factor affecting construction safety and engineering efficiency. High stress and extremely broken surrounding rock often manifests as strong rock deformation, bottom heave, spalling, roof collapse and other instability phenomena. The traditional "anchor mesh spraying" support system can no longer effectively meet the support needs in such complex working conditions.

[0003] Under extremely broken surrounding rock conditions, the surrounding rock strength is reduced, the self-bearing capacity is weakened, and the stress concentration area is more extensive and difficult to transfer, which can easily lead to surrounding rock damage and support failure. In addition, the deformation of the surrounding rock under high stress is continuous and significant. The existing support technology is difficult to coordinate the mechanical properties of the surrounding rock deformation and the support system, resulting in poor support effect. Especially in the case of significant floor heave, due to the lack of effective floor support and pressure relief measures, the traditional support system is difficult to achieve overall reinforcement and stress release of the surrounding rock, and the risk of tunnel deformation and damage is significantly increased.

[0004] The prior art discloses a method for integrally reinforcing and supporting surrounding rocks of deep-well tunnels with a rigid-flexible coupling support pole, which comprises spraying concrete on the tunnel section surface to seal the surrounding rocks, supporting the tunnel surrounding rocks with a steel mesh pole anchor rod, and implementing anchor cables and re-spraying concrete at the center of the tunnel surrounding rock top and the arch shoulders on both sides; after the tunnel is excavated, grouting holes for the tunnel top plate and the two sides of the surrounding rocks are constructed, and then grouting anchor rods are installed in the grouting holes, cement slurry is injected into the grouting anchor rods, and after a certain thickness is excavated downward from the horizontal surface of the bottom plate, concrete is sprayed to form a grouting stop layer; finally, bottom plate grouting holes and grouting anchor pipes are constructed on the bottom plate rock mass to inject cement slurry into the main plate, and concrete is backfilled to form a flat concrete backfill layer on the tunnel bottom plate, thereby achieving integral support for the tunnel and surrounding rocks. Although this support method couples anchor rods with anchor cables and solves the serious problem of tunnel heave by grouting the bottom plate, it is still difficult to effectively control the non-uniform deformation of the top plate, side plate and bottom plate under high stress conditions, and it is difficult to solve the problem of large stress concentration areas and difficult transfer under extremely broken surrounding rock conditions. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a combined support method for high-stress and extremely broken surrounding rock tunnels, aiming to solve the technical problems that the existing support methods have poor support effects on high-stress and extremely broken surrounding rock tunnels, and are difficult to solve the large range of stress concentration areas and difficult to transfer.

[0006] The embodiment of the present application provides a combined support method for a high-stress extremely broken surrounding rock tunnel, comprising the following steps:

[0007] S1. After excavating a tunnel under high-stress and extremely broken surrounding rock conditions, first construct pressure relief holes and pressure relief grooves. The pressure relief holes are set in the stress concentration area of ​​the surrounding rock around the tunnel. The excavation direction of the pressure relief holes is set parallel to the direction of the tunnel, and the pressure relief groove is set perpendicular to the bottom plate of the tunnel.

[0008] S2. After the construction of the pressure relief holes and the pressure relief grooves is completed, the two are backfilled using a filling technique;

[0009] S3, after the pressure relief holes and pressure relief grooves are filled, anchor rods and high-strength prestressed anchor cables are arranged on the tunnel wall surface in the surrounding rock to form a plum blossom-shaped anchoring system;

[0010] S4, high-pressure grouting is performed on the surrounding rock through the high-strength prestressed anchor cables arranged in step S3, and finally the surrounding rock of the tunnel is treated with shotcrete to seal the surface of the surrounding rock, thereby achieving joint support of the tunnel with high stress and extremely broken surrounding rock.

[0011] In the technical solution of the embodiment of the present application, the "external support-medium strength-internal unloading" joint support method is used, combined with the means of pressure relief, anchoring and grouting, to coordinate the mechanical properties of the support structure and the surrounding rock, and achieve long-term stability and construction safety of high-stress extremely broken surrounding rock tunnels. First, by constructing pressure relief holes and pressure relief grooves, the stress of the extremely broken surrounding rock is transferred to the deep part to reduce stress concentration. Subsequently, the pressure relief holes and pressure relief grooves are filled to strengthen the support for the extremely broken surrounding rock. High-strength prestressed anchor cables and anchor rods are then arranged to strengthen the properties of the surrounding rock, optimize the anchoring system, and improve the self-bearing capacity of the surrounding rock through the plum blossom-shaped anchoring system. Finally, grouting and shotcrete sealing treatment are performed to further enhance the overall strength and bearing capacity of the surrounding rock. The support method of the present invention can effectively control the non-uniform deformation of the top plate, side plate and bottom plate of the tunnel by combining external pressure relief with internal reinforcement, improve the stress distribution of the extremely broken surrounding rock, and avoid engineering disasters such as bottom heave and spalling.

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

[0013] In this embodiment, by setting pressure relief holes parallel to the direction of the tunnel in the stress concentration area of ​​the surrounding rock around the tunnel, the stress distribution is controlled, so that the stress concentration area in the extremely broken surrounding rock is transferred in a single direction to the deeper surrounding rock, avoiding the problem of part of the stress being transferred to the tunnel surface when the pressure relief holes are constructed from the tunnel wall, which easily causes instability of the tunnel wall and the surrounding extremely broken surrounding rock, thereby reducing the damage and deformation of the surface of the surrounding rock; in addition, by dispersing small-diameter drill holes between the pressure relief holes and the tunnel, it is more conducive to the dispersion of high stress, so that the stress concentration is smaller, and the problem of large stress concentration area and difficult transfer is further solved.

[0014] In some embodiments, the pressure relief groove is arranged at the junction of the two sides of the tunnel and the bottom plate, and is arranged perpendicular to the bottom plate; the length of the pressure relief groove is the strike length of the tunnel, 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, a pressure relief groove is constructed on the tunnel floor to reduce the stress peak, so that the impact of high stress on the tunnel is further reduced, and the problems of floor heave and floor displacement are effectively reduced.

[0016] In some embodiments, in step S3, the high-strength prestressed anchor cables are respectively arranged at the upper and lower corners of the two sides of the tunnel and at both sides of the roof. The high-strength prestressed anchor cables at the lower corners of the tunnel are arranged obliquely downward, the high-strength prestressed anchor cables at the upper corners of the tunnel are arranged obliquely upward, and the high-strength prestressed anchor cables at both sides of the roof are arranged vertically upward to the tunnel roof; the angle between the high-strength prestressed anchor cables at the lower corners of the tunnel and the horizontal plane is greater than the angle between the high-strength prestressed anchor cables at the upper corners of the tunnel and the horizontal plane. The anchor rods are arranged in rows and evenly dispersed at the two sides and the roof of the tunnel, forming a plum blossom-shaped anchoring system with the high-strength prestressed anchor cables.

[0017] In this embodiment, high-strength prestressed anchor cables and anchor rods are arranged in coordination to form a plum blossom-shaped anchoring system, thereby generating a rigid and elastic coupled bearing arch in the extremely broken surrounding rock and improving the bearing capacity of the rock mass; and by arranging the arrangement directions of the high-strength prestressed anchor cables at the upper and lower corners, the anchor cables at the upper corners are used to deeply anchor the top plate, thereby generating a strong suspension effect and forming continuous strong support points along the longitudinal axis of the tunnel, thereby alleviating the expansion of the bottom plate with a larger prestress and avoiding the displacement of the bottom plate; and the anchor cables and anchor rods at the lower corners serve to reinforce the stress concentration area of ​​the corners and prevent shear slip of the surrounding rock.

[0018] In addition, through the subsequent anchor grouting process, the cohesion and internal friction angle of the joint surface (crack surface) are significantly improved, thereby improving the overall strength and self-bearing capacity of the surrounding rock; at the same time, the stress concentration of the surrounding rock at the corners is weakened, avoiding premature damage to the corners and causing large deformation of the two sides and the bottom plate of the tunnel, so as to effectively prevent bottom heave or reduce the amount of bottom heave; on the other hand, through the bottom plate anchor grouting support, the loose and broken zone of the tunnel surrounding rock is reinforced, the integrity of the surrounding rock is enhanced, and the rock strength and the anchoring force of the anchor cable are improved.

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

[0020] In this embodiment, the high-stress soft surrounding rock is loose and broken, and has poor anchorability. Therefore, the broken surrounding rock needs to be consolidated to restore and improve the integrity and overall strength of the surrounding rock. Combined with the support of the steel mesh, the effective bearing circle range of the support structure can be expanded.

[0021] In some embodiments, the angle between the high-strength prestressed anchor cable at the lower corner of the tunnel and the horizontal plane is 45°, and the angle between the high-strength prestressed anchor cable at the upper corner of the tunnel and the horizontal plane is 30°.

[0022] In some embodiments, in step S2, when the pressure relief holes are filled, the slurry is fed and filled from the entrance of the initial excavation face of the pressure relief holes; when the pressure relief grooves are filled, the slurry is fed and filled directly from the tunnel.

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

[0024] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1It is a schematic diagram of the planar structure of the combined support method for a high-stress extremely broken surrounding rock tunnel in the embodiment of the present application;

[0027] Figure 2 This is a schematic diagram of the spatial structure of the combined support method for a high-stress and extremely broken surrounding rock tunnel in an embodiment of the present application;

[0028] Figure 3 This is the distribution diagram of the mining stress field of the Class IV surrounding rock in the unsupported state in Example 1 of the present application;

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

[0030] Figure 5 It is the horizontal displacement diagram of the tunnel under the Class IV surrounding rock in Example 1 of the present application (with drilling holes);

[0031] Figure 6 It is the vertical displacement diagram of the tunnel under the Class IV surrounding rock in Example 1 of the present application;

[0032] Figure 7 This is the horizontal displacement diagram of the tunnel under the V-level surrounding rock in Example 1 of this application (with drilling)

[0033] Figure 8 It is the vertical displacement diagram of the tunnel under the grade V surrounding rock in Example 1 of the present application;

[0034] Fig. 9 This is a diagram showing the stress distribution under the pressure relief measures of the combined support method for the tunnel under the Class IV surrounding rock in Example 1 of the present application;

[0035] Fig.10 This is a diagram showing the stress distribution under pressure relief measures of the combined support method for the tunnel under Grade V surrounding rock in Example 1 of the present application.

[0036] Explanation of the reference numerals: 110 - pressure relief hole; 120 - pressure relief groove; 130 - high-strength prestressed anchor cable; 140 - anchor rod; 150 - drill hole. DETAILED DESCRIPTION

[0037] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0039] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0042] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it 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, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0043] With the continuous increase in mining depth, the stability of deep tunnel surrounding rock under high stress and extremely broken surrounding rock conditions has become a key factor affecting construction safety and engineering efficiency. High-stress extremely broken surrounding rock often manifests itself as strong rock deformation, floor heave, spalling, roof fall and other instability phenomena. The traditional "anchor mesh spraying" support system can no longer effectively meet the support needs in such complex working conditions. Under extremely broken surrounding rock conditions, the surrounding rock strength is reduced and the self-bearing capacity is weakened. At the same time, the stress concentration area is more extensive and difficult to transfer, which can easily cause surrounding rock damage and support failure. In addition, the surrounding rock deformation under high stress is characterized by continuity and significance. The existing support technology is difficult to coordinate the surrounding rock deformation with the mechanical properties of the support system, resulting in poor support effect; especially in the case of significant floor heave, due to the lack of effective floor support and pressure relief measures, the traditional support system is difficult to achieve overall reinforcement and stress release of the surrounding rock, and the risk of tunnel deformation and damage is significantly increased.

[0044] In order to solve the technical problems that the existing support methods have poor support effects on high-stress and extremely broken rock tunnels, and are difficult to solve the large range of stress concentration areas and difficult transfer, the present application provides a combined support method for high-stress and extremely broken rock tunnels. Through the "external support-medium strength-internal unloading" combined support method, combined with the means of pressure relief, anchoring and grouting, the mechanical properties of the support structure and the surrounding rock are coordinated to achieve long-term stability and construction safety of high-stress and extremely broken rock tunnels; this support method combines external pressure relief with internal reinforcement to effectively control the non-uniform deformation of the roof, side and bottom plates of the tunnel, improve the stress distribution of the extremely broken surrounding rock, and avoid engineering disasters such as bottom heave and spalling.

[0045] For the convenience of explanation, the following embodiments are described by taking a combined support method for a high-stress and extremely broken surrounding rock tunnel according to an embodiment of the present application as an example.

[0046] Please refer to Figure 1-2 As shown, the embodiment of the present application provides a combined support method for a high-stress extremely broken surrounding rock tunnel, comprising the following steps:

[0047] S1. After excavation of a tunnel under high-stress and extremely broken surrounding rock conditions, pressure relief holes 110 and pressure relief grooves 120 are first constructed. The pressure relief holes 110 are set in the stress concentration area of ​​the surrounding rock around the tunnel. The excavation direction of the pressure relief holes 110 is set parallel to the direction of the tunnel, and the pressure relief grooves 120 are set 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 a filling technology;

[0049] S3. After the pressure relief holes 110 and the pressure relief grooves 120 are filled, anchor rods 140 and high-strength prestressed anchor cables 130 are arranged on the tunnel wall facing the surrounding rock to form an anchoring system in a plum blossom shape;

[0050] S4, high-pressure grouting is performed on the surrounding rock through the high-strength prestressed anchor cable 130 arranged in step S3, and finally the tunnel surrounding rock is treated with shotcrete to seal the surrounding rock surface, thereby achieving joint support of the high-stress and extremely broken surrounding rock tunnel.

[0051] This scheme uses the "external support-medium strength-internal unloading" joint support method, combined with the means of pressure relief, anchoring and grouting, to coordinate the mechanical properties of the support structure and the surrounding rock, and achieve long-term stability and construction safety of high-stress extremely broken surrounding rock tunnels. First, by constructing pressure relief holes 110 and pressure relief grooves 120, the stress of the extremely broken surrounding rock is transferred to the deep part to reduce stress concentration. Then, the pressure relief holes 110 and pressure relief grooves 120 are filled to strengthen the support for the extremely broken surrounding rock. Then, high-strength prestressed anchor cables 130 and anchor rods 140 are arranged to strengthen the properties of the surrounding rock, optimize the anchoring system, and improve the self-bearing capacity of the surrounding rock through the plum blossom-shaped anchoring system. Finally, grouting and shotcrete sealing treatment are carried out to further enhance the overall strength and bearing capacity of the surrounding rock. The support method of the present invention can effectively control the non-uniform deformation of the top plate, side plate and bottom plate of the tunnel by combining external pressure relief with internal reinforcement, improve the stress distribution of the extremely broken surrounding rock, and avoid engineering disasters such as bottom heave and spalling.

[0052] Further, in some embodiments, in step S1, the pressure relief holes 110 are respectively arranged at the top, bottom and surrounding rock stress concentration areas outside the two sides of the tunnel, and a borehole 150 connecting the pressure relief holes 110 and the tunnel is provided. The radius of the pressure relief hole 110 is 0.4-1.2m, the center distance of the pressure relief hole 110 from the two sides of the tunnel is 1.5-5m, and the distance from the top plate or bottom plate of the tunnel is 2-8.5m. The borehole 150 is arranged between two rows of anchor rods 140, the spacing between adjacent anchor rods 140 is 1.0-1.5m, and the diameter is 30-42cm. The borehole 150 can be used to transport explosives to the pressure relief hole 110 with blasting requirements. In practice, when relieving pressure in certain extremely high stress areas, the pressure relief hole 110 can be appropriately blasted to improve its pressure relief range and effect.

[0053] In the technical solution of this embodiment, by setting pressure relief holes 110 parallel to the direction of the tunnel in the stress concentration area of ​​the surrounding rock around the tunnel, the stress distribution is controlled, so that the stress concentration area in the extremely broken surrounding rock is transferred in a single direction to the deeper surrounding rock, from the vicinity of the tunnel to the vicinity of the pressure relief holes 110, avoiding the problem that when the pressure relief holes are constructed from the tunnel wall, part of the stress is transferred to the tunnel surface, which easily causes instability of the tunnel wall and the surrounding extremely broken surrounding rock, thereby reducing the damage and deformation of the surrounding rock surface; in addition, by dispersing small-diameter drill holes 150 between the pressure relief holes 110 and the tunnel, it is more conducive to the dispersion of high stress, so that the stress concentration is smaller, and the problem of large stress concentration area and difficult transfer is further solved.

[0054] Furthermore, in some embodiments, the pressure relief groove 120 is arranged at the junction of the two sides of the tunnel and the bottom plate, and is arranged perpendicular to the bottom plate; the length of the pressure relief groove 120 is the strike length of the tunnel, 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, a pressure relief groove 120 is constructed on the tunnel floor, which can reduce the stress peak value, further reduce the impact of high stress on the tunnel, and effectively reduce the problems of floor heave and floor displacement.

[0056] Further, in some embodiments, in step S3, the high-strength prestressed anchor cables 130 are respectively arranged at the upper and lower corners of the two sides of the tunnel and at both sides of the roof. The high-strength prestressed anchor cables 130 at the lower corners of the tunnel are arranged obliquely downward, the high-strength prestressed anchor cables 130 at the upper corners of the tunnel are arranged obliquely upward, and the high-strength prestressed anchor cables 130 at both sides of the roof are arranged vertically upward to the tunnel roof; the angle between the high-strength prestressed anchor cables 130 at the lower corners of the tunnel and the horizontal plane is greater than the angle between the high-strength prestressed anchor cables 130 at the upper corners of the tunnel and the horizontal plane. The anchor rods 140 are arranged in rows and evenly dispersed at the two sides and the roof of the tunnel, forming a plum blossom-shaped anchoring system with the high-strength prestressed anchor cables 130.

[0057] In the technical solution of this embodiment, by setting high-strength prestressed anchor cables 130 and anchor rods 140, and the two are arranged in coordination to form a plum blossom-shaped anchoring system, a bearing arch with rigid and elastic coupling is generated in the extremely broken surrounding rock, thereby improving the bearing capacity of the rock mass; and 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 are deeply anchored to the top plate, generating a strong suspension effect, and forming continuous strong support points along the longitudinal axis of the tunnel, so as to alleviate the expansion of the bottom plate with a large prestress and avoid the displacement of the bottom plate; and the anchor cables and anchor rods 140 at the lower corners play the role of reinforcing the stress concentration area of ​​the corners and preventing shear slippage of the surrounding rock. It should be noted that the spacing of the anchor rods 140, the setting of the parameters such as the anchor rods 140 and the high-strength prestressed anchor cables 130 can be determined according to different engineering conditions, such as the location of the stress concentration area.

[0058] In addition, through the subsequent anchor grouting process, the cohesion and internal friction angle of the joint surface (crack surface) are significantly improved, thereby improving the overall strength and self-bearing capacity of the surrounding rock; at the same time, the stress concentration of the surrounding rock at the corners is weakened, avoiding premature damage to the corners and causing large deformation of the two sides and the bottom plate of the tunnel, so as to effectively prevent bottom heave or reduce the amount of bottom heave; on the other hand, through the bottom plate anchor grouting support, the loose and broken zone of the tunnel surrounding rock is reinforced, the integrity of the surrounding rock is enhanced, and the rock strength and the anchoring force of the anchor cable are improved.

[0059] Furthermore, in some embodiments, in step S3, before arranging the anchor rods 140 and the high-strength prestressed anchor cables 130, a steel mesh is used to integrally support the tunnel surrounding rock; the high-strength prestressed anchor cables 130 extend into the surrounding rock to a depth of 8 to 10 m, and the anchor rods 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 soft surrounding rock is loose and broken, and has poor anchorability. Therefore, the broken surrounding rock needs to be consolidated to restore and improve the integrity and overall strength of the surrounding rock. Combined with the support of the steel mesh, the effective bearing circle range of the support structure can be expanded.

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

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

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

[0064] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0065] Example 1

[0066] This embodiment provides a combined support method for a high-stress extremely broken surrounding rock tunnel, comprising the following steps:

[0067] 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 set in the stress concentration area of ​​the surrounding rock around the tunnel. The excavation direction of the pressure relief holes is set parallel to the direction of the tunnel, and the pressure relief groove is set perpendicular to the bottom plate of the tunnel. Among them, the pressure relief holes are set in the stress concentration area of ​​the surrounding rock outside the top, bottom and two sides of the tunnel, and a drill hole connecting the pressure relief holes and the tunnel is set. The spacing between the drill hole and the adjacent anchor rod is 1.0m, and the diameter is 30cm; the pressure relief groove is set at the junction of the two sides of the tunnel and the bottom plate;

[0068] S2. After the construction of the pressure relief holes and pressure relief grooves is completed, the two are backfilled using the filling technology;

[0069] S3. After the pressure relief holes and pressure relief grooves are filled, anchor rods and high-strength prestressed anchor cables are arranged on the tunnel wall facing the surrounding rock to form a plum blossom-shaped anchoring system; wherein, the high-strength prestressed anchor cables are respectively arranged at the upper and lower corners of the two sides of the tunnel and at both sides of the roof, the high-strength prestressed anchor cables at the lower corners of the tunnel are arranged obliquely downward, the high-strength prestressed anchor cables at the upper corners of the tunnel are arranged obliquely upward, and the high-strength prestressed anchor cables at both sides of the roof are arranged vertically to the tunnel roof upward; the high-strength prestressed anchor cables at the lower corners of the tunnel are at an angle of 45° to the horizontal plane, and the high-strength prestressed anchor cables at the upper corners are at an angle of 30° to the horizontal plane; the anchor rods are evenly distributed on the two sides and the roof of the tunnel; the high-strength prestressed anchor cables extend into the surrounding rock to a depth of 9m, and the anchor rods extend into the surrounding rock to a depth of 2.2m;

[0070] S4, high-pressure grouting is performed on the surrounding rock through the high-strength prestressed anchor cables arranged in step S3, and finally the surrounding rock of the tunnel is treated with shotcrete to seal the surface of the surrounding rock, thereby achieving joint support of the tunnel with high stress and extremely broken surrounding rock.

[0071] In order to verify the feasibility of the above support method, the FLAC3D numerical simulation software was used to perform the corresponding simulation to compare the support effects of no support, original support (traditional anchor mesh spraying support) and the combined support method (hereinafter referred to as combined support) of Example 1. The physical and mechanical parameters of the broken IV and V grade surrounding rocks were selected to establish the tunnel model, and the relevant basic data of the tunnel under the parameters of the IV and V grade surrounding rocks without support were obtained.

[0072] See also Figure 3-4 As shown, in Grade IV surrounding rock, the horizontal stress is mainly concentrated above the tunnel floor and roof, which are about 2.64m and 3.08m away from the inner wall of the tunnel respectively, and the vertical stress is concentrated on both sides of the tunnel, which are about 1.98m away from the inner wall of the tunnel; in Grade V surrounding rock, the horizontal stress is mainly concentrated above the tunnel floor and roof, which are about 7.26m and 7.92m away from the inner wall of the tunnel respectively, and the vertical stress is about 4.18m away from the inner wall of the tunnel.

[0073] Based on the above analysis, the tunnel model is re-established (ref. Figure 1 and Figure 2As shown), in the IV grade surrounding rock, the pressure relief groove is 1m high, 0.3m wide, the radius of the pressure relief hole is 0.5m, and the distances from the center of the pressure relief hole to the two sides and the top plate (bottom plate) are 1.98m and 2.64m respectively, which is consistent with the stress concentration area; in the V grade surrounding rock, the pressure relief groove is also 1m high, 0.3m wide, the radius of the pressure relief hole is enlarged to 1m, and the distances from the center of the pressure relief hole to the two sides, the top plate and the bottom plate 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 on the tunnel bottom plate and the broken surrounding rock area.

[0074] See also Figures 5 to 8 As shown, in the IV grade surrounding rock, the side (right side) displacements of the tunnel under no support, original support and combined support are 40.55mm, 33.67mm and 11.77mm respectively, the top plate displacements are 44.04mm, 14.23mm and 8.83mm respectively, and the bottom plate displacements are 48.10mm, 42.40mm and 15.61mm respectively; in the V grade surrounding rock, the side (right side) displacements of the tunnel under no support, original support and combined support are 333.16mm, 284.17mm and 52.52mm respectively, the top plate displacements are 451.84mm, 143.83mm and 40.46mm respectively, the bottom plate displacements are 419.25mm, 312.63mm and 59.12mm respectively, and the maximum displacement of the combined support is no longer distributed near the inner wall of the tunnel, but appears near the pressure relief hole.

[0075] As can be seen from the figure, under the condition of Class IV surrounding rock parameters, the traditional support method cannot effectively control the deformation of the tunnel, because it lacks reinforcement measures for the bottom plate, and the deformation of the bottom plate area is extremely large. The bottom drum volume in Class IV surrounding rock is more than 40mm, and it reaches 312mm in Class V surrounding rock. Under such a large displacement, the tunnel will suffer from large deformation, slab slab, roof fall, bottom drum and other engineering disasters, which seriously threaten the safe and efficient mining of the mine. After adopting the combined support of Example 1 of the present application, the bearing capacity of the surrounding rock near the tunnel is significantly improved, and the tunnel surrounding rock is effectively controlled. The maximum displacement of Class V surrounding rock no longer appears near the inner wall of the tunnel, but appears near the pressure relief hole. With the tunnel as the center, the displacement presents the characteristics of "large size", and the displacement of the tunnel bottom plate and the side is reduced, and the deformation of the extremely broken rock mass is also effectively controlled.

[0076] See also Figure 9-10As shown in the figure, they are the stress distribution diagrams of the combined support method under the pressure relief measures of the tunnels in the IV and V surrounding rocks. It can be seen from the figure that in the IV surrounding rock, the horizontal stress above the top plate has moved back by about 2m, and the range is wider, and it is more evenly distributed to the rear of the pressure relief hole, and the value has decreased from 75.31MPa to 57.55MPa. The horizontal stress below the bottom plate has moved back by about 1m, and the range is also wider, and it is more evenly distributed to the rear of the pressure relief hole. The vertical stress of the two sides has moved back by about 1m, and the range is wider. At the same time, it has a tendency to move upward, and the value does not change much. In the V-level surrounding rock, the backward shift effect is more significant, and all directions are generally about 1m more than the IV-level surrounding rock. The area is reduced, and the stress is more transferred to a small area deep in the surrounding rock. The impact of high stress on the tunnel is further reduced, and the stress state of the extremely broken surrounding rock tunnel has been improved.

[0077] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A combined support method for high-stress extremely broken surrounding rock tunnels, characterized in that: The following steps are involved: S1. After excavating a tunnel under high-stress and extremely broken surrounding rock conditions, first construct pressure relief holes and pressure relief grooves. The pressure relief holes are set in the stress concentration area of ​​the surrounding rock around the tunnel. The excavation direction of the pressure relief holes is set parallel to the direction of the tunnel, and the pressure relief groove is set perpendicular to the bottom plate of the tunnel. S2. After the construction of the pressure relief holes and the pressure relief grooves is completed, the two are backfilled using a filling technique; S3, after the pressure relief holes and pressure relief grooves are filled, anchor rods and high-strength prestressed anchor cables are arranged on the tunnel wall surface in the surrounding rock to form an anchoring system with a plum blossom layout; S4, high-pressure grouting is performed on the surrounding rock through the high-strength prestressed anchor cables arranged in step S3, and finally the surrounding rock of the tunnel is treated with shotcrete to seal the surface of the surrounding rock, thereby achieving joint support of the tunnel with high stress and extremely broken surrounding rock.

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

3. The combined support method for high-stress extremely broken surrounding rock tunnel according to claim 2 is characterized in that: The radius of the pressure relief hole is 0.4-1.2m; the center distance of the pressure relief hole to the two sides of the tunnel is 1.5-5m, and the distance from the top plate or bottom plate of the tunnel is 2-8.5m.

4. The combined support method for high-stress extremely broken surrounding rock tunnel according to claim 1 is characterized in that: The pressure relief groove is arranged at the junction of the two sides of the tunnel and the bottom plate, and is arranged perpendicular to the bottom plate; the length of the pressure relief groove is the direction length of the tunnel, the width of the pressure relief groove is 0.2-0.5m, and the height is 0.8-1.2m.

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

6. The combined support method for high-stress extremely broken surrounding rock tunnel according to claim 5 is characterized in that: The anchor rods are arranged in rows and evenly dispersed on the two sides and the top plate of the tunnel, forming an anchoring system with a plum blossom layout with the high-strength prestressed anchor cables.

7. The combined support method for high-stress extremely broken surrounding rock tunnel according to claim 2 is characterized in that: The drill hole is arranged between two rows of anchor rods, with a spacing of 1.0 to 1.5 m between adjacent anchor rods and a diameter of 30 to 42 cm. The drill hole can be used to transport explosives to a pressure relief hole where blasting is required.

8. The combined support method for high-stress extremely broken surrounding rock tunnel according to claim 1 is characterized in that: In step S3, before arranging the anchor rods and high-strength prestressed anchor cables, a steel mesh is used to integrally support the tunnel surrounding rock; the high-strength prestressed anchor cables extend into the surrounding rock to a depth of 8 to 10 m, and the anchor rods extend into the surrounding rock to a depth of 1.5 to 3 m.

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

10. The combined support method for high-stress extremely broken surrounding rock tunnel according to claim 1 is characterized in that: In step S2, when the pressure relief hole is filled, the slurry is fed and filled from the entrance of the initial excavation face of the pressure relief hole; when the pressure relief groove is filled, the slurry is directly fed and filled from the tunnel.

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