A method for controlling the stability of soft rock roadway surrounding rock prone to weathering and swelling

Abstract

The application provides a kind of easy weathering dilatant soft rock roadway surrounding rock stability control method, belongs to underground mine roadway surrounding rock control technical field.The method includes: in the surface of the surrounding rock of roadway full section spraying high molecular waterproof material, the water layer formed blocks water vapor into the surrounding rock;In the roadway setting hierarchical support structure, form shallow anchor rod reinforcement and deep anchor cable suspension mutual cooperation of active support layer;In the surface of the active support layer of roadway spray steel fiber reinforced concrete, to form the passive support layer coupled with active support layer;The bottom surface of roadway is excavated into arch wave surface, the plane corresponding to arch wave surface is arch plate surface, arch wave surface and arch plate surface are surrounded by anti-arch space, pouring rubble concrete in the anti-arch space, to form anti-arch structure in the bottom of roadway.The application can effectively control the deformation of surrounding rock instability, solve the waterproof failure of easy weathering dilatant soft rock roadway, support system mismatch and bottom heave out of control problem, realize easy weathering dilatant soft rock roadway long-term safety and stability.

Description

Technical Field

[0001] This invention relates to the field of surrounding rock control technology in underground mine roadways, and particularly to a method for controlling the stability of surrounding rock in easily weathered and expansive soft rock roadways. Background Technology

[0002] Controlling the surrounding rock in tunnels is a crucial aspect of safety management in underground mines. During tunnel excavation and operation, the primary objective of rock control is to ensure the stability and safety of the tunnel, preventing deformation, damage, and instability of the surrounding rock. Easily weathered and expansive soft rock is a special type of engineering rock mass with relatively low mechanical strength. Rich in clay minerals such as kaolinite and illite, it exhibits rapid weathering upon exposure, swelling and softening upon contact with water, and strong rheological properties. This makes it prone to problems such as roof collapse, floor heave, full-section shrinkage deformation, and creep instability, resulting in significant challenges in controlling the surrounding rock.

[0003] For roadways made of easily weathered and expansive soft rock, previous methods for controlling the surrounding rock included anchor mesh spraying support, surrounding rock grouting, U-shaped steel arch support, and double-layer concrete lining. However, these traditional technologies have the following drawbacks: 1) The surrounding rock begins to weather 1-2 hours after exposure, and traditional processes cannot seal it quickly; ordinary concrete spraying has low strength, is prone to cracking, has poor sealing performance, and cannot effectively block water vapor infiltration; the surrounding rock grouting is delayed and cannot seal the rock voids and block water vapor infiltration in time. For surrounding rock with poor permeability, the grouting effect is poor; the construction cycle of double-layer concrete lining is long and cannot meet the needs of rapid excavation and support of soft rock tunnels.

[0004] 2) The surrounding rock itself has low strength, strong rheological properties, large expansion deformation pressure, and long creep duration. Conventional anchor-mesh-spray support structures are simple and cannot effectively control the distribution of pressure at different depths of the surrounding rock. Anchor bolts and sprayed layers are prone to failure due to local stress concentration, resulting in a high risk of surrounding rock instability, a high roadway repair rate, and affecting the normal functioning of personnel passage, ore transportation, and mine ventilation.

[0005] 3) The treatment of roadway floor heave lacks coordinated design with roof and sidewall support, resulting in poor control of shrinkage deformation of the surrounding rock across the entire cross section; U-shaped steel arch support is costly and lacks a floor anti-arch structure, which cannot suppress roadway floor heave, thus triggering a vicious cycle of roof and sidewall deformation and damage.

[0006] Based on the above analysis, the relevant technologies cannot adequately meet the actual needs of controlling the surrounding rock in easily weathered and expansive soft rock tunnels. Summary of the Invention

[0007] This invention provides a method for controlling the stability of surrounding rock in easily weathered, expansive soft rock roadways. Its purpose is to effectively control the deformation and instability of the surrounding rock, solve the problems of waterproofing failure, support system mismatch, and floor heave in easily weathered, expansive soft rock roadways, and achieve long-term safety and stability of easily weathered, expansive soft rock roadways.

[0008] To achieve the above objectives, the present invention provides a method for controlling the stability of surrounding rock in easily weathered and expansive soft rock roadways, comprising: Step 1: Excavate the underground rock mass of the mine to form a tunnel. Spray a high-polymer waterproof material on the entire cross-section of the surrounding rock surface of the tunnel to form a water-proof layer and prevent water vapor from seeping into the surrounding rock. Step 2: Install graded support structures on the roof and sidewalls of the roadway to form an active support layer in which shallow anchor bolt reinforcement and deep anchor cable suspension work together. Step 3: Spray steel fiber reinforced concrete onto the surface of the active support layer in the roadway to form a passive support layer coupled with the active support layer. Step 4: Excavate the bottom surface of the tunnel into an arched surface, and the plane corresponding to the arched surface is an arch plate surface. The arched surface and the arch plate surface enclose an anti-arch space. Pour crushed stone concrete in the anti-arch space to form an anti-arch structure at the bottom of the tunnel.

[0009] In one embodiment, step 2 involves setting up a graded support structure on the roof and sidewalls of the roadway to form an active support layer that combines shallow anchor bolt reinforcement with deep anchor cable suspension, including: Step 21: The anchor rod is inserted into the shallow surrounding rock of the tunnel at the first anchorage length, and a first steel mesh is laid on the top plate and sidewalls of the tunnel. The anchor rod protrudes from one side of the tunnel and is connected to the first steel mesh. The anchor rod's reinforcement effect suppresses the delamination deformation of the shallow surrounding rock. Step 22: The anchor cable is inserted into the deep surrounding rock of the roadway at the second anchoring length, and a preload is applied to the anchor cable to provide secondary reinforcement and support for the surrounding rock. The deep suspension effect of the anchor cable prevents the surrounding rock from collapsing and becoming unstable.

[0010] In one embodiment, step 21, inserting the anchor bolt into the shallow surrounding rock of the tunnel at a first anchorage length, includes: Step 211: First anchoring holes are opened in a rectangular array on the top plate and sidewalls of the tunnel; Step 212: Place anchoring agent in each of the first anchoring holes; Step 213: Insert the anchor rod into each of the first anchoring holes so that the side of the anchor rod facing away from the tunnel is bonded to the anchoring agent so that the anchor rod has the first anchoring length.

[0011] In one embodiment, step 22, inserting the anchor cable into the deep surrounding rock of the roadway at a second anchorage length, includes: Step 221: Open second anchoring holes in a rectangular array on the top plate and sidewalls of the tunnel; Step 222: Place anchoring agent in each of the second anchoring holes; Step 223: Insert the anchor cable into each of the second anchor holes so that the side of the anchor cable facing away from the tunnel is bonded to the anchoring agent so that the anchor cable has the second anchor length.

[0012] In one embodiment, the polymer waterproofing material is configured as a polyurethane material or an acrylate curing material.

[0013] In one embodiment, step 3, spraying steel fiber reinforced concrete onto the surface of the active support layer in the roadway to form a passive support layer coupled with the active support layer, includes: The steel fiber reinforced concrete is sprayed in layers on the surface of the active support layer of the roadway. The thickness of each layer of steel fiber reinforced concrete is less than or equal to 50 mm, and the total thickness of the steel fiber reinforced concrete ranges from 80 mm to 120 mm, providing high-strength passive support for the surrounding rock of the roadway.

[0014] In one embodiment, step 4 involves excavating the bottom surface of the tunnel into an arched surface, with the plane corresponding to the arched surface being an arch plate surface. The arched surface and the arch plate surface enclose a reverse arch space, and crushed stone concrete is poured into the reverse arch space to form a reverse arch structure at the bottom of the tunnel, including: Step 41: Lay a second steel mesh on the arch wave surface and the arch plate surface respectively; Step 42: Pour the crushed stone concrete into the anti-arch space to combine the crushed stone concrete with the second steel mesh to form the anti-arch structure; Step 43: In the vertical direction, the arch foot of the anti-arch structure is brought into contact with the passive support layer to form an integrated closed bearing ring for full-section support of the roadway.

[0015] In one embodiment, the waterproofing layer spraying operation is completed rapidly within 1-2 hours after the tunnel excavation.

[0016] In one embodiment, step 1 involves excavating the underground rock mass of the mine to form a tunnel, and spraying a polymer waterproof material across the entire cross-section of the surrounding rock surface of the tunnel to form a waterproof layer that prevents water vapor from penetrating the surrounding rock, including: Clean up loose rock blocks, debris, and dust from the surface of the surrounding rock.

[0017] In one embodiment, the thickness of the waterproof layer ranges from 2 mm to 3 mm.

[0018] The above-described solution of the present invention has the following beneficial effects: In this embodiment, based on the understanding of the weathering, expansion, and softening mechanism of easily weathered and expansive soft rock, a waterproof layer formed by polymer waterproof material is used to quickly seal the surrounding rock formed during excavation, creating a flexible isolation layer. This effectively blocks the infiltration of water vapor into the surrounding rock, preventing water-rock reaction and fundamentally controlling the environmental conditions for weathering, expansion, and softening of the surrounding rock. Furthermore, based on the understanding of the rheological properties and creep instability mechanism of soft rock, graded support structures are installed on the roof and sidewalls of the tunnel, followed by sprayed steel fiber reinforced concrete for surface support. This combination forms a synergistic control mechanism for the pressure at different depths of the surrounding rock, effectively controlling deformation and instability. Moreover, the anti-arch structure at the bottom of the tunnel can be combined with steel fiber reinforced concrete to form a closed bearing ring across the entire cross-section, effectively preventing tunnel floor heave and its resulting chain reaction damage to the roof and sidewall support structures and surrounding rock instability. In summary, the method for controlling the surrounding rock stability of easily weathered, expansive soft rock roadways provided by this invention has significant innovation and technical advantages. It can effectively control roof subsidence, floor heave deformation, and creep instability, significantly extend the effective service life of roadways after primary support, and significantly improve the safety and stability of easily weathered, expansive soft rock roadways. It has broad application prospects and high promotion value.

[0019] Other beneficial effects of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating a method for controlling the stability of surrounding rock in easily weathered and expanding soft rock tunnels according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the tunnel cross-section in one embodiment of the present invention; Figure 3 for Figure 2 A magnified schematic diagram of the structure at point A in the middle.

[0021] [Explanation of Labels in the Attached Image] 1. Tunnel; 11. Roof; 12. Sidewalls; 2. Waterproof layer; 3. Graded support structure; 31. Anchor bolt; 32. Anchor cable; 33. First steel mesh; 34. Tray; 4. Steel fiber reinforced concrete; 5. Inverted arch structure; 51. Arch wave surface; 52. Arch slab surface; 53. Second steel mesh; 54. Crushed stone concrete; 6. Surrounding rock. Detailed Implementation

[0022] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not 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 invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] This application provides a method for controlling the stability of the surrounding rock 6 in a roadway 1 that is prone to weathering and expansion. By comprehensively implementing and coordinating the sealing and waterproofing of the surrounding rock 6, the active and passive graded collaborative support, and the anti-arch structure 5 of the bottom plate, the deformation and instability of the surrounding rock 6 can be effectively controlled, and the problems of waterproofing failure, support system mismatch, and bottom heave loss of control in the roadway 1 that is prone to weathering and expansion are solved, so as to achieve long-term safety and stability of the roadway 1 that is prone to weathering and expansion.

[0026] Specifically, please refer to Figure 1 and Figure 2 The stability control method for the surrounding rock 6 of the easily weathered and expansive soft rock tunnel 1 in this application includes: Step S1: Excavate the underground rock mass of the mine to form a tunnel 1. Spray a polymer waterproof material on the entire cross-section of the surrounding rock 6 of the tunnel 1 to form a water-proof layer 2, which blocks water vapor from seeping into the surrounding rock 6.

[0027] For example, the mountain can be an underground mine containing easily weathered and expandable soft rock, such as a tin-copper mine. The ore body occurs in the alteration zone within granite and the contact zone between granite and marble. The altered granite, rich in the clay mineral kaolinite, is highly susceptible to rapid weathering and expansion when exposed to moisture, making it a typical example of easily weathered and expandable soft rock. Excavation is carried out in this underground mine to form tunnel 1. When tunnel 1 is located within altered granite, controlling the stability of the surrounding rock 6 is challenging. For example, the burial depth of tunnel 1 is approximately 800m, the cross-sectional dimensions of tunnel 1 can be 4.2m x 3.9m, and the shape of the cross-section can be a three-centered arch composed of three internally tangent circular arcs. When conventional anchor-mesh shotcrete support or U-shaped steel arch support is used in roadways in altered granite, problems such as concrete spraying layer cracking, anchor bolt breakage and failure, roadway floor heave, cross-sectional narrowing, and roof instability frequently occur. Repeated repairs have failed to achieve satisfactory results, severely impacting the normal use of the roadway and significantly increasing support costs. Therefore, the following steps are adopted to improve the stability of the surrounding rock 6.

[0028] For example, after the tunnel 1 is excavated, a water-proof layer 2 is immediately sprayed on the entire surface of the tunnel 1 to make the water-proof layer 2 more continuous and sealed, reducing the possibility of water vapor infiltrating into the surrounding rock 6 around the tunnel 1, thereby helping to reduce the possibility of weathering and softening of the surrounding rock 6.

[0029] For example, the spraying operation of the waterproof layer 2 should be completed within 1 to 2 hours after the excavation of the tunnel 1. The thickness of the waterproof layer 2 can be 2 mm to 3 mm. The spraying coverage of the waterproof layer 2 should be greater than or equal to 95% so that the impermeability of the waterproof layer 2 is greater than or equal to 99%.

[0030] In step S2, a graded support structure 3 is installed on the roof 11 and sidewalls 12 of the tunnel 1 to form an active support layer in which shallow anchor bolts 31 reinforce and deep anchor cables 32 suspend in coordination.

[0031] For example, after the waterproof layer 2 is sprayed, short anchor bolts 31 can be anchored in the shallow surrounding rock 6 of the roof 11 and sidewalls 12 of the tunnel 1 to suppress deformation of the shallow surrounding rock 6. Long anchor cables 32 can be anchored in the deep surrounding rock 6 of the roof 11 and sidewalls 12 of the tunnel 1 to reduce the possibility of collapse and instability of the surrounding rock 6. The short anchor bolts 31 and long anchor cables 32 can work together, and prestress can be applied to the short anchor bolts 31 and long anchor cables 32 to actively tighten the surrounding rock 6, forming an active support to control the deformation of the surrounding rock 6.

[0032] Step S3: Steel fiber reinforced concrete 4 is sprayed onto the surface of the active support layer of roadway 1 to form a passive support layer coupled with the active support layer.

[0033] For example, the steel fiber reinforced concrete 4 sprayed on the graded support structure 3 can be coupled with the structure of the part of the graded support structure 3 that protrudes from the roadway 1 to enhance the physical and mechanical properties of the steel fiber reinforced concrete 4. This allows the steel fiber reinforced concrete 4 to better withstand the pressure of the surrounding rock 6 of the roadway 1 after solidification and provide a high-strength passive support for the surrounding rock 6 of the roadway 1.

[0034] For example, by incorporating steel fibers into concrete, the tensile, flexural, and shear strengths and toughness of steel fiber reinforced concrete 4 are significantly improved, while crack resistance, fatigue resistance, and durability are also enhanced. Its core properties include enhanced mechanical properties and improved impact resistance. When steel fiber reinforced concrete 4 is sprayed onto the protruding portion of the graded support structure 3 within the roadway 1, it can couple with it to form a steel fiber reinforced reinforced concrete support layer. The pressure of the surrounding rock 6 around the roadway 1 acts on the steel fiber reinforced concrete 4, which passively provides high-strength support to the surrounding rock 6.

[0035] For example, in steel fiber reinforced concrete 4, the content of steel fibers can be 1% to 1.5% of the volume of steel fiber reinforced concrete 4, for example, 1.2%. The length of the steel fibers ranges from 25 mm to 35 mm. The tensile strength of the steel fibers is greater than or equal to 800 MPa.

[0036] For example, the mix ratio of cement, sand, and crushed stone in steel fiber reinforced concrete 4 can be 1:1.5:2. The water-cement ratio can be 0.4~0.45, for example, 0.45.

[0037] Step S4: The bottom surface of the tunnel 1 is excavated into an arched surface 51, and the plane corresponding to the arched surface 51 is an arched plate surface 52. The arched surface 51 and the arched plate surface 52 enclose an anti-arch space. Crushed stone concrete 54 is poured in the anti-arch space to form an anti-arch structure 5 at the bottom of the tunnel 1.

[0038] For example, the bottom surface of tunnel 1 can be excavated into an arched surface 51 and excavated to the design elevation, and then crushed stone concrete 54 can be poured. When the crushed stone concrete 54 is poured to the arch surface 52, the pouring of crushed stone concrete 54 can be stopped. When the crushed stone concrete 54 solidifies, an anti-arch structure 5 is formed at the bottom of tunnel 1 to reduce the possibility of bottom bulging deformation of tunnel 1.

[0039] For example, the strength grade of the crushed stone concrete 54 can be C30 to C40. The particle size of the crushed stone in the crushed stone concrete 54 can be 20mm to 40mm, and the mix ratio of cement to sand to crushed stone can be 1:1.5:3.

[0040] In this embodiment, based on the understanding of the weathering, expansion, and softening mechanism of easily weathered and expandable soft rock, a waterproof layer 2 formed by polymer waterproof material is used to quickly seal the surrounding rock 6 formed by excavation, forming a flexible isolation layer. This effectively blocks the infiltration of water vapor into the surrounding rock 6, preventing water-rock reaction between the surrounding rock 6 and water vapor, and fundamentally controlling the environmental conditions for weathering, expansion, and softening of the surrounding rock 6. Furthermore, based on the understanding of the rheological properties and creep instability mechanism of soft rock, graded support structures 3 are installed on the roof 11 and sidewalls 12 of the tunnel 1, and then sprayed steel fiber reinforced concrete 4 provides surface support. The combination of these structures forms a synergistic control mechanism for the deep and shallow pressure of the surrounding rock 6, which can effectively control the deformation and instability of the surrounding rock 6. Moreover, the anti-arch structure 5 at the bottom of the tunnel 1 can be combined with the steel fiber reinforced concrete 4 to form a full-section closed bearing ring, effectively preventing the floor heave of the tunnel 1 and the resulting chain reaction damage to the roof 11 and sidewall 12 support structures and the instability of the surrounding rock 6. In summary, the stability control method for the surrounding rock 6 of the easily weathered, expansive soft rock roadway 1 provided by this invention has significant innovation and technical advantages. It can effectively control the subsidence of the roof 11, the deformation of the floor, and creep instability of the roadway 1, significantly extend the effective service life of the roadway 1 after primary support, and significantly improve the safety and stability of the easily weathered, expansive soft rock roadway 1. It has broad application prospects and high promotion value.

[0041] In one embodiment, please refer to Figure 2 Step S2 involves installing a graded support structure 3 on the roof 11 and sidewalls 12 of roadway 1, forming an active support layer where shallow anchor bolts 31 provide reinforcement and deep anchor cables 32 provide suspension, comprising: In step S21, anchor bolts 31 are inserted into the shallow surrounding rock 6 of the tunnel 1 with a first anchoring length, and a first steel mesh 33 is laid on the top plate 11 and sidewall 12 of the tunnel 1. The anchor bolts 31 protrude from one side of the tunnel 1 and are connected to the first steel mesh 33. The reinforcement effect of the anchor bolts 31 suppresses the delamination deformation of the shallow surrounding rock 6.

[0042] For example, the length of the anchor bolt 31 can be 1.5m to 2m, for example, 2m. The diameter of the anchor bolt 31 can be 20mm to 22mm, for example, 20mm. The material of the anchor bolt 31 can be HRB grade left-hand threaded steel with a yield strength greater than or equal to 335MPa.

[0043] In step S22, anchor cable 32 is inserted into the deep surrounding rock 6 of roadway 1 at the second anchoring length, and pre-tightening force is applied to the anchor cable 32 to provide secondary reinforcement support for the surrounding rock 6. The deep suspension effect of the anchor cable 32 prevents the surrounding rock 6 from collapsing and becoming unstable.

[0044] For example, the length of the anchor cable 32 can be 6m to 8m, such as 7m. The diameter of the anchor cable 32 can be 15.2mm to 21.8mm, such as 15.2mm. The material of the anchor cable 32 can be 1*7 standard steel strand with a tensile strength greater than or equal to 260kN. The second anchorage length of the anchor cable 32 can be 1.5m to 2m, and the first anchorage length of the anchor rod 31 can be 0.5m to 0.8m, such that the second anchorage length is greater than the first anchorage length.

[0045] For example, the first reinforcing mesh 33 can be welded from hot-rolled round steel with a diameter of 6mm to 8mm. The mesh size of the first reinforcing mesh 33 is 100mm*100mm, that is, the spacing between the reinforcing bars in both the horizontal and vertical directions of the first reinforcing mesh 33 is 100mm. The size of the first reinforcing mesh 33 can be 2m*1.5m. The overlap width of two adjacent pieces of the first reinforcing mesh 33 can be greater than or equal to 100mm. The anchor bolt 31 and the anchor cable 32 protrude along their own axial direction from one side of the roadway 1 and are connected to the first reinforcing mesh 33, for example, they can be as follows: Figure 3 The tray 34 shown is connected. The tray 34 is set on the side of the first steel mesh 33 away from the surrounding rock 6 so that the first steel mesh 33 can be laid on the roof 11 and sidewall 12 of the tunnel 1, and also so that the anchor bolt 31, anchor cable 32 and the first steel mesh 33 can be connected as a whole.

[0046] In this embodiment, based on the understanding of the rheological properties and creep instability mechanism of soft rock, a combined active and passive support scheme is constructed, integrating the graded active support of anchor bolts 31 and anchor cables 32 with the passive support of steel fiber reinforced concrete 4. The anchor bolts 31 are relatively short and can be configured to reinforce shallow surrounding rock 6. The anchor cables 32 are relatively long and can be configured to anchor deeper surrounding rock 6. A first steel mesh 33 is laid on the roof 11 and sidewalls 12 of the tunnel 1, and connected to the anchor bolts 31 and anchor cables 32. Steel fiber reinforced concrete 4 is then sprayed onto it to fully utilize its surface support function. The coupling of anchor bolts 31, anchor cables 32, first steel mesh 33, and steel fiber reinforced concrete 4 significantly improves the integrity and synergistic support strength of the anchor-mesh-sprayed support structure. The organic combination of these components forms a synergistic control mechanism for the deep and shallow pressure of the surrounding rock 6, effectively controlling the deformation and instability of the surrounding rock 6.

[0047] In one embodiment, please refer to Figure 2 and Figure 3 Step S21 involves inserting anchor bolts 31 into the shallow surrounding rock 6 of the tunnel 1 at a first anchoring length, including: Step S211: First anchoring holes are opened in a rectangular array on the top plate 11 and sidewall 12 of the tunnel 1.

[0048] For example, the first anchoring holes are arranged at intervals of 0.8m to 1.2m in two mutually perpendicular directions on the roof 11 and sidewall 12 of the roadway 1, for example, 1m, to reduce the effect of the group anchoring effect.

[0049] Step S212: Place anchoring agent in each first anchoring hole.

[0050] For example, the material of the anchoring agent can be a fast-curing resin cartridge, such as an MSCKb2350 resin cartridge.

[0051] Step S213: Anchor bolts 31 are inserted into each first anchoring hole so that the side of the anchor bolts 31 facing away from the roadway 1 is bonded with the anchoring agent so that the anchor bolts 31 have a first anchoring length.

[0052] For example, the anchor bolt 31 may include an anchoring section, a free section, and an anchor head. The length of the anchoring section is the length of the portion of the anchor bolt 31 that is inserted into the first anchoring hole and bonded with the anchoring agent, i.e., the first anchoring length. The length of the portion of the anchor bolt 31 that is inserted into the first anchoring hole but not bonded with the anchoring agent is the length of the free section. The anchor head is the portion of the anchor bolt 31 located outside the first anchoring hole.

[0053] For example, once the anchor rod 31 has bonded with the anchoring agent and formed a certain strength, the free section of the anchor rod 31 can be tensioned by the locking device to apply prestress to the free section.

[0054] In this embodiment, the first anchoring holes are distributed in a rectangular array, so that the anchor rods 31 inserted in the first anchoring holes are also distributed in a rectangular array on the roof 11 and sidewalls 12 of the tunnel 1. Under the curing of the anchoring agent, the relatively uniform and shorter anchor rods 31 can better suppress the deformation of the shallow surrounding rock 6.

[0055] In one embodiment, please refer to Figure 2 and Figure 3 Step S22 involves embedding anchor cable 32 into the deep surrounding rock 6 of roadway 1 at a second anchoring length, including: Step S221: Open second anchoring holes in a rectangular array on the top plate 11 and sidewall 12 of the tunnel 1.

[0056] For example, the second anchoring holes are arranged at intervals of 2m to 3m in two mutually perpendicular directions on the roof 11 and sidewall 12 of the roadway 1, for example, 2m, to reduce the effect of the group anchoring effect.

[0057] For example, the second anchor hole does not coincide with the first anchor hole.

[0058] Step S222: Place anchoring agent in each second anchoring hole.

[0059] For example, the material of the anchoring agent can be a fast-curing resin cartridge, such as an MSCKb2350 resin cartridge.

[0060] Step S223: Anchor cable 32 is inserted into each second anchor hole so that the side of anchor cable 32 facing away from roadway 1 is bonded with anchoring agent so that anchor cable 32 has a second anchor length.

[0061] For example, when the anchor cable 32 has bonded with the anchoring agent and formed a certain strength, the free section of the anchor cable 32 can be tensioned by the locking device to apply a prestress of 80kN to 120kN to the free section, for example, a prestress of 100kN.

[0062] In this embodiment, the second anchoring holes are distributed in a rectangular array, so that the anchor cables 32 inserted in the second anchoring holes are also distributed in a rectangular array on the roof 11 and sidewalls 12 of the roadway 1. Under the curing of the anchoring agent, the relatively uniform and longer anchor cables 32 can better suppress the deformation of the deep surrounding rock 6.

[0063] In one embodiment, please refer to Figure 3 The polymer waterproofing material is configured as either polyurethane or acrylate curing material, enabling the waterproof layer 2 to cure at a faster rate. This reduces the time required to seal the surrounding rock 6 around the tunnel 1, thereby slowing down the weathering and softening process of the surrounding rock 6. Furthermore, it exhibits good adhesion to both the surrounding rock 6 and the steel fiber reinforced concrete 4, ensuring a tight bond between the waterproof layer 2 and both materials, preventing delamination.

[0064] For example, the polymer waterproofing material can be a two-component polyurethane.

[0065] In one embodiment, step S3, spraying steel fiber reinforced concrete 4 onto the surface of the active support layer of the roadway 1 to form a passive support layer coupled with the active support layer, includes: Steel fiber reinforced concrete 4 is sprayed in layers onto the surface of the active support layer of roadway 1. Each layer of steel fiber reinforced concrete 4 has a thickness of less than or equal to 50 mm, and the total thickness of the steel fiber reinforced concrete 4 ranges from 80 mm to 120 mm, providing high-strength passive support for the surrounding rock 6 of roadway 1. Layered spraying of steel fiber reinforced concrete 4 has two advantages: firstly, it facilitates the expulsion of air bubbles in the inner layers of steel fiber reinforced concrete 4, reducing the possibility of honeycomb voids during the solidification process and thus improving the density of the steel fiber reinforced concrete 4; secondly, it allows the steel fiber reinforced concrete 4 to dissipate heat layer by layer, reducing temperature stress within the steel fiber reinforced concrete 4.

[0066] For example, in the process of layered spraying of steel fiber reinforced concrete 4, a wet spraying process is adopted, and the total thickness of steel fiber reinforced concrete 4 can be 100mm.

[0067] In one embodiment, please refer to Figure 2 and Figure 3 Step S4: The bottom surface of tunnel 1 is excavated into an arched surface 51, and the plane corresponding to the arched surface 51 is an arched plate surface 52. The arched surface 51 and the arched plate surface 52 enclose an anti-arch space. Crushed stone concrete 54 is poured in the anti-arch space to form an anti-arch structure 5 at the bottom of tunnel 1, including: Step S41: Lay the second steel mesh 53 on the arch wave surface 51 and the arch plate surface 52 respectively.

[0068] For example, please refer to Figure 3 The second steel mesh 53 on both the arch wave surface 51 and the arch plate surface 52 can be configured in two layers. The mesh spacing of each layer of the second steel mesh 53 can be 150mm to 200mm, and the reinforcement ratio can be 0.6% to 1%. For example, if the mesh spacing is 150mm, the reinforcement ratio is 0.8%. That is, the spacing of the steel bars in the two mutually perpendicular directions in the second steel mesh 53 can be 150mm to 200mm.

[0069] Step S42: Pour crushed stone concrete 54 into the anti-arch space so that the crushed stone concrete 54 is combined with the second steel mesh 53 to form the anti-arch structure 5. The anti-arch structure 5 is configured as a reinforced concrete structure, which is beneficial to improving the performance and strength of the anti-arch structure 5.

[0070] Step S43: In the vertical direction, the arch foot of the anti-arch structure 5 is brought into contact with the passive support layer to form an integrated closed bearing ring for full-section support of the roadway 1.

[0071] For example, please refer to Figure 3 In the vertical direction, the overlap length between the arch foot of the inverted arch structure 5 and the steel fiber reinforced concrete 4 can be greater than or equal to 100mm, for example, 110mm. That is, the depth to which the arch foot of the inverted arch structure 5 is embedded in the steel fiber reinforced concrete 4 can be 110mm.

[0072] For example, after the steel fiber reinforced concrete 4 of the roof slab 11 and sidewalls 12 of the tunnel 1 has initially hardened, the bottom of the tunnel 1 is excavated to the design depth. A double layer of second steel mesh 53 is laid on the arch wave surface 51 and the arch plate surface 52, and crushed stone concrete 54 is poured to form an anti-arch structure 5. The arch foot of the anti-arch structure 5 can be embedded in the bottom of the sidewalls 12 of the tunnel 1, that is, embedded in the steel fiber reinforced concrete 4, and together with the graded support structure 3, it forms an integrated full-section closed bearing ring, providing full-section support for the tunnel 1 and reducing the possibility of chain failure of other support structures and instability of the surrounding rock 6 caused by floor heave.

[0073] In one embodiment, please refer to Figure 2The rise-to-span ratio of the inverted arch structure 5 ranges from 1 / 8 to 1 / 10. This relatively reasonable rise-to-span ratio makes the inverted arch structure 5 both economical and safe.

[0074] For example, the rise-to-span ratio of the inverted arch structure 5 is the ratio of the rise of the arch structure to its span. The rise-to-span ratio of the inverted arch structure 5 can be 1 / 9.

[0075] In one embodiment, please refer to Figure 2 and Figure 3 The spraying of the waterproof layer 2 is completed quickly within 1-2 hours after the excavation of the tunnel 1, so as to quickly seal the surrounding rock 6 of the tunnel 1, which is beneficial to control the deformation and instability of the surrounding rock 6 of the easily weathered and expansive soft rock tunnel 1.

[0076] In one embodiment, step S1 involves excavating the underground rock mass of the mine to form a tunnel 1, and spraying a polymer waterproof material across the entire cross-section of the surrounding rock 6 of the tunnel 1 to form a waterproof layer 2, preventing water vapor from seeping into the surrounding rock 6. This includes: Clean the loose rock blocks, debris and dust from the surface of the surrounding rock 6 so that the wall surface of the tunnel 1 to be sprayed is cleaner, flatter and firmer, which is conducive to improving the bonding ability between the waterproof layer 2 and the wall surface of the tunnel 1.

[0077] For example, a pry bar can be used to quickly remove loose rock blocks from the surface of the surrounding rock 6 around the tunnel 1, and a compressed air jet can be used to clean the debris and dust from the surface of the surrounding rock 6 more thoroughly.

[0078] In one embodiment, the thickness of the waterproof layer 2 ranges from 2mm to 3mm, so that the waterproof layer 2 has a good waterproof sealing effect.

[0079] For example, by strictly controlling the construction sequence to maximize the synergistic effect of steps S1 to S4, the on-site construction of the following five steps should be completed rapidly within 24 to 72 hours after the excavation of tunnel 1: “Sealed water-proof layer 2 → primary support with anchor bolts 31 → secondary support with anchor cables 32 → shotcrete layer with steel fiber reinforced concrete 4 → bottom arch structure 5”. After construction, the deformation and stability of the surrounding rock 6 of tunnel 1 and the integrity of the support structure are monitored regularly. After 12 months of continuous monitoring, the results show that, with the technical solution of this application, the settlement of the roof 11 and surrounding rock 6 of tunnel 1 is 40mm to 50mm, and the heave at the bottom is 5mm to 10mm, which are reduced by about 80% and 90% respectively compared with the construction methods in related technologies. No obvious cracking was observed in the shotcrete steel fiber reinforced concrete 4, and the overall stability of tunnel 1 is good, indicating that the technical solution of this application has a significant control effect on the stability of easily weathered and expansive soft rock tunnel 1.

[0080] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the stability of surrounding rock in easily weathered and expansive soft rock tunnels, characterized in that, include: Step 1: Excavate the underground rock mass of the mine to form a tunnel. Spray a polymer waterproof material on the entire cross-section of the surrounding rock surface of the tunnel to form a water-proof layer and prevent water vapor from penetrating the surrounding rock. The polymer waterproof material is configured as a polyurethane material or an acrylate curing material. Step 2 involves installing a graded support structure on the roof and sidewalls of the roadway to form an active support layer that combines shallow anchor bolt reinforcement with deep anchor cable suspension. Specifically, this includes: Step 21: The anchor rod is inserted into the shallow surrounding rock of the tunnel at the first anchorage length, and a first steel mesh is laid on the top plate and sidewalls of the tunnel. The anchor rod protrudes from one side of the tunnel and is connected to the first steel mesh. The anchor rod's reinforcement effect suppresses the delamination deformation of the shallow surrounding rock. Step 22: The anchor cable is inserted into the deep surrounding rock of the roadway at the second anchoring length, and a pre-tightening force is applied to the anchor cable to provide secondary reinforcement and support for the surrounding rock. The deep suspension effect of the anchor cable is used to prevent the surrounding rock from collapsing and becoming unstable. Step 3: Spray steel fiber reinforced concrete onto the surface of the active support layer in the roadway to form a passive support layer coupled with the active support layer; wherein, the steel fiber reinforced concrete is sprayed in layers onto the surface of the active support layer in the roadway, with each layer of steel fiber reinforced concrete having a thickness of less than or equal to 50 mm, and the total thickness of the steel fiber reinforced concrete ranging from 80 mm to 120 mm, providing high-strength passive support for the surrounding rock of the roadway. Step 4: Excavate the bottom surface of the tunnel into an arched surface, and the plane corresponding to the arched surface is an arch plate surface. The arched surface and the arch plate surface enclose an anti-arch space. Pour crushed stone concrete into the anti-arch space to form an anti-arch structure at the bottom of the tunnel. Specifically, this includes: Step 41: Lay a second steel mesh on the arch wave surface and the arch plate surface respectively; Step 42: Pour the crushed stone concrete into the anti-arch space to combine the crushed stone concrete with the second steel mesh to form the anti-arch structure; Step 43: In the vertical direction, the arch foot of the anti-arch structure is brought into contact with the passive support layer to form an integrated closed bearing ring for full-section support of the roadway.

2. The method for controlling the stability of surrounding rock in easily weathered, expansive soft rock tunnels according to claim 1, characterized in that, Step 21, inserting the anchor bolt into the shallow surrounding rock of the roadway at a first anchorage length, including: Step 211: First anchoring holes are opened in a rectangular array on the top plate and sidewalls of the tunnel; Step 212: Place anchoring agent in each of the first anchoring holes; Step 213: Insert the anchor rod into each of the first anchoring holes so that the side of the anchor rod facing away from the tunnel is bonded to the anchoring agent so that the anchor rod has the first anchoring length.

3. The method for controlling the stability of surrounding rock in easily weathered, expansive soft rock tunnels according to claim 1, characterized in that, Step 22, inserting the anchor cable into the deep surrounding rock of the roadway at a second anchorage length, including: Step 221: Open second anchoring holes in a rectangular array on the top plate and sidewalls of the tunnel; Step 222: Place anchoring agent in each of the second anchoring holes; Step 223: Insert the anchor cable into each of the second anchor holes so that the side of the anchor cable facing away from the tunnel is bonded to the anchoring agent so that the anchor cable has the second anchor length.

4. The method for controlling the stability of surrounding rock in easily weathered, expansive soft rock tunnels according to claim 1, characterized in that, The waterproofing layer spraying operation is completed quickly within 1-2 hours after the tunnel is excavated.

5. The method for controlling the stability of surrounding rock in easily weathered, expansive soft rock tunnels according to claim 1, characterized in that, Step 1: Excavate the underground rock mass of the mine to form a tunnel. Spray a high-polymer waterproof material across the entire cross-section of the surrounding rock surface of the tunnel to form a waterproof layer, preventing water vapor from penetrating the surrounding rock. This includes: Clean up loose rock blocks, debris, and dust from the surface of the surrounding rock.

6. The method for controlling the stability of surrounding rock in easily weathered, expansive soft rock tunnels according to claim 1, characterized in that, The thickness of the waterproof layer ranges from 2mm to 3mm.

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