Construction method of roadway surrounding rock reinforcing structure

Abstract

The application discloses a construction method of a roadway surrounding rock reinforcing structure and belongs to the field of roadway surrounding rock reinforcement. In view of the problems that grout is prone to loss and prestress loss is large in the existing grouting and anchor rod supporting, the application adopts a deep-to-shallow sequence grouting, deep injection of slow-setting grout, shallow injection of fast-setting grout, and larger shallow grouting pressure, realizes deep filling and shallow compaction cooperation, accurately controls the prestress application time to the period from initial setting to final setting of the shallow grouting material, reduces the prestress loss, sets differentiated grouting parameters through surrounding rock detection zoning, realizes symptomatic reinforcement, controls the mutual overlap of the shallow grouting diffusion ranges, forms a continuous ring-shaped reinforcing shell, and forms a shell-arch composite supporting system together with a surface fiber concrete layer. The application has compact procedures, does not need complex equipment, significantly improves the overall stability of the surrounding rock, and is suitable for underground engineering such as mines and tunnels.

Description

Technical Field

[0001] This invention relates to the field of roadway surrounding rock reinforcement, and more specifically, to a construction method for a roadway surrounding rock reinforcement structure. Background Technology

[0002] In mine roadways, traffic tunnels, and underground cavern engineering, the stability of the surrounding rock directly affects construction safety and long-term service performance. For surrounding rock with well-developed joints and fissures and large loosened zones, traditional single anchor bolt support or single grouting reinforcement methods often fail to form an effective synergistic load-bearing structure. Existing technologies often employ a combined "anchor bolt + grouting" support approach, but most methods involve one-time full-hole grouting or grouting followed by anchor bolt installation. While this approach has several advantages, the inventors have discovered the following shortcomings in practical work, such as: 1. The grouting pressure is singular, and the grout is prone to flow away along large cracks, making it impossible to achieve both deep filling and shallow compaction at the same time; 2. The timing of grouting and anchor bolt prestressing is unreasonable, making it difficult to effectively transfer prestress to the grouting body and causing prestress loss; 3. The selection of grouting materials is limited, making it inconvenient to adapt to different reinforcement needs at different depths and shallow depths.

[0003] Therefore, there is an urgent need for a construction method that can achieve zoned and sequential coordinated reinforcement. So we propose a construction method for roadway surrounding rock reinforcement structure to solve the above-mentioned problems. Summary of the Invention

[0004] 1. Technical problems to be solved To address the problems existing in the prior art, the present invention aims to provide a construction method for reinforcing the surrounding rock of a roadway. By precisely matching the timing of sequential grouting and prestressing, it achieves the synergistic effect of deep filling reinforcement and shallow compaction bearing, significantly improving the overall stability of the surrounding rock.

[0005] 2. Technical Solution To solve the above problems, the present invention adopts the following technical solution.

[0006] A construction method for a roadway surrounding rock reinforcement structure includes the following steps: S1. Sealing of surrounding rock surface: Shot concrete is sprayed onto the surface of the surrounding rock of the tunnel to form a sealing layer; S2. Anchor bolt installation: Drill holes through the sealing layer into the surrounding rock, and after setting a grout stop plug at the hole opening, install hollow grouting anchor bolts in the drill hole; S3. Deep grouting: The first grouting material is injected into the depth of the borehole through the hollow grouting anchor rod at the first grouting pressure. Grouting is stopped when the grout absorption is lower than the preset threshold and the pressure is stabilized for a preset time, thus forming a deep reinforcement zone. S4. Shallow grouting: When the first grouting material has initially set but not yet fully set, the second grouting material is injected into the shallow part of the borehole through the same hollow grouting anchor at the second grouting pressure. Grouting continues until the grouting pressure reaches the second grouting pressure and the grout absorption is lower than another preset threshold, thus forming a shallow reinforcement zone. Wherein, the second grouting pressure is greater than the first grouting pressure, and the gel time of the second grouting material is shorter than the gel time of the first grouting material. S5. Prestressing application: Before the second grouting material reaches initial setting but not final setting, prestress is applied to the hollow grouting anchor and locked. S6. Construction of surface bearing layer: After prestressing is locked, a fiber concrete layer is sprayed onto the surface of the sealing layer to form a surface bearing layer.

[0007] Furthermore, the first grouting material is ordinary silicate cement single-liquid grout, and the second grouting material is cement-water glass double-liquid grout.

[0008] Furthermore, in the cement-water glass two-component slurry, the volume ratio of cement slurry to water glass is 1:0.3 to 0.5.

[0009] Furthermore, the water-cement ratio of the ordinary silicate cement single-liquid slurry is 0.6 to 0.8:1.

[0010] Furthermore, in step S5, the applied prestress value is 30% to 60% of the yield load of the hollow grouting anchor rod.

[0011] Furthermore, between steps S3 and S4, a step for determining the timing of grouting switching is included: monitoring the curing state of the first grouting material, and starting the shallow grouting step when the curing degree of the first grouting material reaches a predetermined proportion of its initial setting state. Preferably, the predetermined proportion is 70% to 90%.

[0012] Furthermore, prior to step S2, a rock detection and zoning step is included: detecting the distribution of fracture zones and the range of loosened zones in the surrounding rock of the roadway, dividing the roadway circumferentially into multiple grouting zones based on the detection results, and setting different grouting parameters for different zones. The grouting parameters include at least one or more of the following: first grouting pressure, second grouting pressure, and borehole depth.

[0013] Furthermore, in step S4, the gelation time and grouting pressure of the second grouting material are controlled to ensure that the shallow grouting diffusion range of adjacent hollow grouting anchors overlaps with each other, thereby forming a continuous circumferential reinforced shell in the shallow part of the roadway surrounding rock.

[0014] Furthermore, in step S1, the sprayed concrete is concrete with added quick-setting agent; in step S6, the sprayed fiber concrete contains added steel fibers or polypropylene fibers.

[0015] 3. Beneficial Effects Compared with the prior art, the advantages of this invention are: (1) The scheme adopts a sequential grouting strategy of first deep and then shallow, and the grouting material in the deep part gels slowly while the grouting material in the shallow part gels quickly. Combined with the pressure gradient that the second grouting pressure is greater than the first grouting pressure, the scheme achieves the dual effect of filling deep fissures and compacting and squeezing water in the shallow part, avoiding excessive loss of grout and improving grouting efficiency. (2) This scheme precisely controls the timing of prestressing application after the initial setting and before the final setting of the second grouting material. At this time, the grouting body still has a certain plastic deformation capacity, and the applied prestress can be evenly transmitted to the surrounding rock and the grouting body. After the grout is completely solidified, a high prestressed synergistic bearing structure is formed, which reduces the prestress loss. (3) This scheme uses different grouting parameters for different fracture development levels through surrounding rock detection and zoning steps, so as to achieve targeted reinforcement and avoid material waste or reinforcement blind spots caused by uniform grouting. (4) In the shallow grouting step, this scheme controls the overlapping of the grout diffusion range to form a continuous circumferential reinforced shell, which together with the surface fiber concrete bearing layer constitutes a shell arch composite support system, greatly improving the overall stability of the surrounding rock of the roadway. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the construction method of the present invention. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] Example 1: Please see Figure 1 A construction method for a roadway surrounding rock reinforcement structure includes the following steps: First, perform S1 surrounding rock surface sealing: After cleaning the surface of the surrounding rock of the tunnel by removing loose rocks and rinsing it clean, spray C20 concrete mixed with a quick-setting agent to form a sealing layer with a thickness of about 30-50mm. The purpose of the sealing layer is to prevent a large amount of grout from escaping from the surrounding rock surface during subsequent grouting and to provide a flat working surface for anchor bolt installation.

[0019] Next, the S2 anchor bolt installation is carried out: a borehole with a diameter of 42mm is drilled through the sealing layer into the surrounding rock, and the depth is determined to be 2.5-4.0m based on the loosening zone detection results. A grout stop plug is installed at the borehole opening, and then the hollow grouting anchor bolt is inserted into the borehole, so that the grouting channel of the anchor bolt is connected to the inside of the borehole. The exposed length of the anchor bolt does not exceed 150mm to facilitate subsequent tensioning.

[0020] Next, S3 deep grouting is performed: The first grouting material is injected into the depth of the borehole through the grouting channel of the hollow grouting anchor at a first grouting pressure (preferably 0.5–1.5 MPa). The first grouting material is ordinary silicate cement single-liquid grout with a water-cement ratio of 0.7:1, which has a relatively long gel time (approximately 2–4 hours). During the grouting process, the grout absorption rate is continuously monitored. When the absorption rate is below 1 L / min, the pressure is maintained for 3–5 minutes before grouting is stopped. At this point, a deep reinforcement zone is formed in the depth of the borehole and surrounding fractures.

[0021] Then, determine the timing for switching grouting: monitor the temperature of the first grouting material or use a penetration resistance meter to detect its curing degree. When the curing degree of the first grouting material reaches about 80% of its initial setting state (i.e., it has initially set but has not yet fully set), start the shallow grouting step.

[0022] Next, shallow grouting (S4) is performed: A second grouting material is injected into the shallow part of the borehole using the same hollow grouting anchor at a second grouting pressure (preferably 2.0–4.0 MPa). The second grouting material is a cement-water glass dual-liquid grout, with a cement grout to water glass volume ratio of 1:0.4, and a gel time controlled at 1–2 minutes. When the grouting pressure reaches the second grouting pressure and the grout absorption rate remains less than 0.5 L / min, the pressure is maintained for 2 minutes before grouting is stopped, forming a shallow reinforcement zone. Because the second grouting pressure is greater than the first grouting pressure, and the second grouting material gels quickly, it can create a compaction and water-squeezing effect in the shallow part without damaging the already partially set deep reinforcement zone.

[0023] Subsequently, S5 prestressing is applied: Before the second grouting material reaches initial setting but not final setting (i.e., within approximately 3–10 minutes after grouting), prestress is applied to the hollow grouting anchor rod using a tensioning jack. The prestress value is taken as 40%–50% of the anchor rod's yield load. After reaching the design value, the nut is used to lock it in place. At this time, the grouting body has not yet fully solidified and has a certain degree of plasticity, allowing the prestress to be evenly transmitted to the surrounding rock and the grouting body.

[0024] Finally, the S6 surface bearing layer is constructed: after prestressing is locked, a C25 concrete layer mixed with steel fibers, 80–120 mm thick, is sprayed onto the surface of the sealing layer to form the surface bearing layer. This completes the construction of the entire reinforcement structure.

[0025] Example 2: In view of the above embodiment 1, further description is provided, see reference. Figure 1 This embodiment addresses the uneven development of fractures in the surrounding rock of a roadway by adding a rock detection and zoning step before the anchor bolt installation in step S2. Ground-penetrating radar is used to detect fracture zones every 5 meters along the roadway's longitudinal direction, obtaining the distribution of fracture zones and the extent of loosening. Based on the detection results, the roadway is divided into four zones: the roof zone, the sidewall zone, and the bottom corner zone. For the roof zone with strong fracture development, the first grouting pressure is set to 0.8 MPa, the second grouting pressure to 2.5 MPa, and the drilling depth is increased to 4.0 m. For the sidewall zone with moderate fracture development, the first grouting pressure is set to 1.2 MPa, the second grouting pressure to 3.2 MPa, and the drilling depth to 3.0 m. For the bottom corner zone with poor fracture development, the first grouting pressure is set to 1.5 MPa, the second grouting pressure to 3.8 MPa, and the drilling depth to 2.5 m. The remaining construction steps are the same as in Embodiment 1. This differentiated grouting by zone ensures the reinforcement effect of key areas while avoiding unnecessary material waste.

[0026] Example 3: In view of the above embodiments 1 and 2, further description is provided, please refer to... Figure 1 In this embodiment, to achieve a better overall load-bearing effect, during shallow grouting in step S4, the gel time of the second grouting material (controlled between 30 seconds and 1 minute) and the grouting pressure (appropriately increased to 3.0–4.0 MPa) are adjusted so that the shallow grouting diffusion radii of adjacent hollow grouting anchors overlap. Specifically, the anchor spacing is designed to be 1.0 m, and the grouting diffusion radius is controlled to be no less than 0.6 m, thereby forming a continuous circumferential reinforced shell with a thickness of approximately 0.8–1.2 m in the shallow part of the surrounding rock of the roadway. This shell, together with the subsequently constructed surface load-bearing layer, constitutes a double-layer load-bearing structure, significantly improving the roadway's resistance to deformation.

[0027] Example 4: In view of the above embodiments 1, 2 and 3, further description is provided, please refer to Figure 1 In this embodiment, during the sealing of the surrounding rock surface in step S1, concrete with added accelerator is used, with the accelerator dosage being 4% to 6% of the cement weight, to allow the sealing layer to set quickly and shorten the process interval. During the construction of the surface bearing layer in step S6, polypropylene fibers are added to the sprayed fiber-reinforced concrete at a dosage of 1.2 kg / m³. 3 This improves the crack resistance and toughness of the surface bearing layer. The remaining steps are the same as in Example 1.

[0028] The above description is merely a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concepts, should be covered within the scope of protection of the present invention.

Claims

1. A construction method for a roadway surrounding rock reinforcement structure, characterized in that, Includes the following steps: S1. Sealing of surrounding rock surface: Shot concrete is sprayed onto the surface of the surrounding rock of the tunnel to form a sealing layer; S2. Anchor bolt installation: Drill holes through the sealing layer into the surrounding rock, and after setting a grout stop plug at the hole opening, install hollow grouting anchor bolts in the drill hole; S3. Deep grouting: The first grouting material is injected into the depth of the borehole through the hollow grouting anchor rod at the first grouting pressure. Grouting is stopped when the grout absorption is lower than the preset threshold and the pressure is stabilized for a preset time, thus forming a deep reinforcement zone. S4. Shallow grouting: When the first grouting material has initially set but not yet fully set, the second grouting material is injected into the shallow part of the borehole through the same hollow grouting anchor at the second grouting pressure. Grouting continues until the grouting pressure reaches the second grouting pressure and the grout absorption is lower than another preset threshold, thus forming a shallow reinforcement zone. Wherein, the second grouting pressure is greater than the first grouting pressure, and the gel time of the second grouting material is shorter than the gel time of the first grouting material. S5. Prestressing application: Before the second grouting material reaches initial setting but not final setting, prestress is applied to the hollow grouting anchor and locked. S6. Construction of surface bearing layer: After prestressing is locked, a fiber concrete layer is sprayed onto the surface of the sealing layer to form a surface bearing layer.

2. The construction method for a roadway surrounding rock reinforcement structure according to claim 1, characterized in that: The first grouting material is ordinary silicate cement single-liquid grout, and the second grouting material is cement-water glass double-liquid grout.

3. The construction method for a roadway surrounding rock reinforcement structure according to claim 2, characterized in that: In the cement-water glass two-component slurry, the volume ratio of cement slurry to water glass is 1:0.3 to 0.

5.

4. The construction method for a roadway surrounding rock reinforcement structure according to claim 2, characterized in that: The water-cement ratio of the ordinary silicate cement single-liquid slurry is 0.6 to 0.8:

1.

5. The construction method for a roadway surrounding rock reinforcement structure according to claim 1, characterized in that: In step S5, the applied prestress value is 30% to 60% of the yield load of the hollow grouting anchor rod.

6. The construction method for a roadway surrounding rock reinforcement structure according to claim 1, characterized in that: Between step S3 (deep grouting) and step S4 (shallow grouting), there is also a grouting switching timing judgment. The grouting switching timing judgment includes monitoring the curing state of the first grouting material. When the curing degree of the first grouting material reaches a predetermined proportion of its initial setting state, the shallow grouting step is started.

7. The construction method for a roadway surrounding rock reinforcement structure according to claim 1, characterized in that: Before the anchor bolt installation in step S2, a rock detection and zoning step is also included. The rock detection and zoning step includes detecting the distribution of fracture zones and the range of loosened zones in the surrounding rock of the roadway. Based on the detection results, the roadway is divided into multiple grouting zones in the circumference, and different grouting parameters are set for different zones. The grouting parameters include at least one or more of the following: first grouting pressure, second grouting pressure, and borehole depth.

8. The construction method for a roadway surrounding rock reinforcement structure according to claim 1, characterized in that: In step S4, shallow grouting, the gel time and grouting pressure of the second grouting material are controlled to ensure that the shallow grouting diffusion range of adjacent hollow grouting anchors overlaps with each other.

9. The construction method for a roadway surrounding rock reinforcement structure according to claim 1, characterized in that: In step S1, the surrounding rock surface sealing is carried out using sprayed concrete with added quick-setting agent. In step S6, the surface bearing layer construction is carried out using sprayed fiber concrete with added steel fibers or polypropylene fibers.

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