Argillaceous weakly cemented roadway surrounding rock anchor rod and grouting combined reinforcement control method

Abstract

The invention discloses an anchor rod and grouting combined reinforcement control method for surrounding rock of an argillaceous weak cemented roadway, relates to the technical field of coal mine roadway support, and solves the problems of poor anchoring performance of an anchor rod, insufficient grouting pertinence and poor grouting and anchoring collaboration in the prior art. According to the technical scheme, the method comprises the steps that grouting and supporting parameter collaborative design is conducted; after roadway tunneling, full-section concrete spraying sealing is immediately carried out; deep and shallow hole step-by-step differential grouting is conducted, shallow hole low-pressure permeation is conducted firstly to form a shallow reinforcing ring, and then deep hole high-pressure splitting is conducted to form a deep reinforcing area; and finally, high-pretightening-force anchor rods (cables) are installed to form a cooperative bearing body. The reinforcing ring layer with the reasonable strength gradient is formed, efficient cooperation of surrounding rock modification and active supporting is achieved, and the supporting reliability and the overall stability of surrounding rock are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of coal mine roadway support technology, and in particular to a method for combined reinforcement and control of surrounding rock in weakly cemented mud roadways using anchor bolts and grouting. Background Technology

[0002] Muddy, weakly cemented rock masses are widely distributed in mining areas of western my country. These masses are characterized by short formation time, low cementation, and loose structure, generally exhibiting significant engineering characteristics such as low strength, easy weathering, and easy softening and mudification upon contact with water. When tunneling through such rock formations, excavation disturbance easily induces the development of surrounding rock fissures. Coupled with the interaction between water and rock, this leads to a rapid deterioration of the surrounding rock strength, triggering continuous strong rheology and large deformations, making tunnel stability control extremely difficult.

[0003] Currently, the main support techniques for soft rock tunnels include active support using bolts (cables) and grouting reinforcement. However, in the unique geological environment of weakly cemented clay, existing technologies have significant limitations:

[0004] First, the effectiveness of conventional anchor bolt (cable) support is significantly reduced. Its effectiveness is highly dependent on the surrounding rock providing a stable and reliable anchoring foundation. However, weakly cemented argillaceous rock masses cannot form an effective anchoring bearing ring, making it difficult to form anchoring force and causing it to decay easily, resulting in early failure of the support structure.

[0005] Secondly, conventional grouting reinforcement strategies lack specificity. Existing grouting technologies mostly focus on sealing shallow fractures or homogenizing the rock mass, failing to fully consider the structural differences in fracture development, mechanical state, and hydrological influences from shallow to deep layers of the surrounding rock. The use of uniform grouting parameters leads to uneven grout diffusion, making it difficult to construct a complete, continuous reinforcement layer with a reasonable strength gradient from shallow to deep.

[0006] Furthermore, the grouting-support system suffers from poor synergy. In engineering practice, grouting reinforcement and anchor (cable) support are often implemented as independent procedures, resulting in a mismatch in mechanical properties and a lack of coordination in construction sequence. The reinforced body formed by grouting fails to achieve spatial coupling and mechanical matching with the effective anchorage range of subsequent support components, thus failing to form a unified and synergistic load-bearing structure, which greatly limits the overall effectiveness of the combined reinforcement technology.

[0007] Therefore, there is an urgent need for an integrated control method that can combine the functions of surrounding rock modification and active support, and achieve synergy between the parameters and temporal depth of the two, in order to solve the problem of stability control of the surrounding rock of weakly cemented mud roadways. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems in the prior art and provide a method for controlling the reinforcement of surrounding rock in muddy, weakly cemented roadways by combining anchor bolts and grouting.

[0009] The technical concept of this invention is to solve the problem of supporting weakly cemented muddy rock by systematically coupling three elements: "full-section closure, step-by-step differential grouting at deep and shallow holes, and coordinated grouting and anchoring parameters." First, shotcrete is sprayed to seal the rock surface and prevent weathering. Then, low-pressure permeable grouting is used to construct a shallow reinforcement ring, and high-pressure fracturing grouting forms a deep reinforcement zone, actively creating a load-bearing structure with a reasonable strength gradient. Finally, the anchoring ends of high-preload anchors and cables are precisely located within the shallow and deep reinforcement zones, respectively, achieving mechanical performance matching and spatial coupling between the grouting body and the support components. This ultimately forms a highly efficient "anchor-grouting coordinated load-bearing body," fundamentally improving the overall stability of the surrounding rock.

[0010] To achieve the aforementioned objectives, the present invention employs the following technical solution: a method for combined reinforcement and control of surrounding rock in muddy, weakly cemented roadways using anchor bolts and grouting, comprising the following steps:

[0011] S1. Collaborative design of key parameters: Based on the geological survey results, a systematic collaborative design of grouting parameters and anchor bolt support parameters is carried out.

[0012] S2. Full-section timely sealing of surrounding rock: After the tunnel is excavated and formed, the surface of the tunnel is immediately sealed with full-section shotcrete.

[0013] S3. Differential grouting reinforcement in shallow and deep holes: low-pressure permeation grouting is carried out in the shallow part of the surrounding rock and high-pressure fracturing-permeation grouting is carried out in the deep part of the surrounding rock to form a shallow reinforcement ring and a deep reinforcement zone.

[0014] S4. High-strength anchor bolts work together to provide active support. After the grouting solid reaches the design strength, the anchor bolts are installed and a high preload is applied, so that the support system and the grouting solid are coupled to form a co-supporting body.

[0015] Furthermore, the specific content of step S1 is as follows:

[0016] S1.1. Based on the tunnel cross-sectional dimensions, the degree of surrounding rock fragmentation, and the target reinforcement ring thickness, determine the grouting pressure, grouting time, and grout diffusion radius for shallow and deep holes;

[0017] S1.2. Based on the grouting reinforcement range, design the length, diameter, spacing, and preload of the anchor bolts and anchor cables in reverse order to ensure that the anchoring ends of the support components are all located within the effective grouting reinforcement zone and achieve coupling. Through the coordinated design of the above parameters, the problem of mismatch between the mechanical properties of the grouting reinforcement zone and the support components is solved, achieving the optimal spatial coupling effect between the support force field and the grouting reinforcement zone.

[0018] Furthermore, in step S2, the protective layer formed by the shotcrete seal is at least 50mm thick. This effectively isolates the surrounding rock from contact with air and moisture, solving the technical problems of easily weathered and softened rock with weak cementation, and achieving the technical effect of slowing down the initial deterioration of the surrounding rock strength.

[0019] Furthermore, the specific content of step S3 is as follows:

[0020] S3.1 Shallow-hole low-pressure permeation grouting: After the full-section sealing layer reaches the design strength, grouting holes are constructed in the shallow part of the surrounding rock of the roadway. The grout is filled into the shallow tension fractures and cemented broken rock mass by low-pressure permeation to form a shallow reinforcement ring.

[0021] S3.2 Deep-hole high-pressure fracturing-penetration grouting: After the shallow reinforcement ring is formed and reaches the predetermined strength, deep grouting holes are constructed in the deep part of the surrounding rock. Grouting is carried out using a high-pressure method. Under high pressure, the grout fractures and weak surfaces in the deep part are split and penetrated, forming a deep reinforcement zone that is effectively connected to the shallow reinforcement ring. By using stepwise differential grouting, the problem of using uniform reinforcement when the structural characteristics of the shallow and deep surrounding rock are significantly different is solved, achieving the technical effect of constructing a complete and continuous reinforcement ring with a reasonable strength gradient from shallow to deep.

[0022] Furthermore, the shallow low-pressure permeation grouting employs a grouting pressure of 1-2 MPa and uses a high-water-rate, fast-setting material as the grout. This optimizes the shallow grouting process, solves the problem of effective cementation in shallow fractured rock masses, and achieves the technical effect of rapidly forming a shallow reinforcement ring with high integrity and significant bearing capacity.

[0023] Furthermore, the deep high-pressure fracturing-penetration grouting employs a grouting pressure of 3-4 MPa. By using a higher grouting pressure, the problem of effectively improving deep primary fractures and weak surfaces is solved, achieving a significant improvement in the integrity and self-supporting capacity of the surrounding rock.

[0024] Furthermore, the specific content of step S4 is as follows:

[0025] S4.1 Anchor bolts shall be installed after the grouting operation is completed and the solidified grout reaches more than 70% of the design strength.

[0026] S4.2 According to the collaborative design parameters, drill holes at predetermined locations and install high-strength anchor bolts and anchor cables. The anchoring end of the high-strength anchor bolt is located within the effective range of the shallow reinforcement ring, and the anchoring end of the anchor cable extends into the deep reinforcement zone.

[0027] S4.3, using specialized tensioning equipment to apply high preload to the anchor bolts, making them tightly coupled with the grout-reinforced surrounding rock, actively providing radial constraint, and together forming an efficient "anchor-grout synergistic bearing body";

[0028] S4.4, Install metal mesh and steel strips or reinforced ladder beams to form a complete support system. Through the above-mentioned collaborative support process, the problem of poor spatial and temporal coordination between anchor bolt support and grouting reinforcement is solved, achieving the technical effect of forming a unified load-bearing structure with matched mechanical properties and efficient load transfer.

[0029] Furthermore, in step S1 or S3, the grouting material used is one of the following: high-water-content quick-setting material, cement-based composite grout, or chemical grout. By flexibly selecting grouting materials, the problem of insufficient adaptability to grouting under different geological conditions can be solved, achieving the technical effect of improving the universality and engineering applicability of the method.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] First, this invention fundamentally solves the core problem of poor anchoring performance of anchor bolts (cables) in weakly cemented argillaceous surrounding rock through a sequential design and parameter coordination of "grouting improvement followed by anchor bolt support." The stepwise grouting of deep and shallow holes actively constructs a surrounding rock reinforcement zone with a reasonable strength gradient from shallow to deep, providing a stable and reliable anchoring foundation for high-strength anchor bolts (cables). This allows the anchoring force of the support system to effectively act on the reinforced rock mass and be transferred to the deep stable rock strata, significantly improving the reliability, long-term service performance, and safety redundancy of the support structure, effectively avoiding early support failure due to insufficient or weakened anchoring force.

[0032] Secondly, the differentiated grouting strategy employed in this invention achieves precise reinforcement and performance enhancement of the surrounding rock from a localized to a holistic perspective. Addressing the characteristics of shallow surrounding rock as fractured and susceptible to water damage, low-pressure permeable grouting is used to effectively fill tension fractures and cement fractured rock masses, forming a highly intact shallow reinforcement ring that acts as a seal and water barrier. For deep surrounding rock, high-pressure fracturing-permeable grouting is used to improve its original fractures and weak surfaces, forming a deep reinforcement zone that acts as a load-bearing framework. This synergistic reinforcement mechanism from the surface inward significantly improves the overall stiffness, strength, and self-supporting capacity of the surrounding rock, thereby effectively suppressing harmful large deformations such as roof subsidence, side convergence, and floor bulging.

[0033] Third, this invention achieves efficient construction of an "anchor-grout synergistic load-bearing structure" through in-depth synergistic optimization of grouting and support parameters, demonstrating outstanding technical and economic advantages. This method emphasizes the matching design of key parameters such as the grouting diffusion radius, anchor (cable) length, and spacing, ensuring complete spatial coverage and optimal mechanical coupling between the support force field and the grouting reinforcement zone. The resulting unified load-bearing structure exhibits a clear and efficient load transfer path. Furthermore, this method can be parametrically adjusted according to specific geological conditions, demonstrating strong universality and adaptability. It can significantly reduce the frequency of roadway repairs and maintenance costs in the later stages, improve overall life-cycle stability, and provide a reliable and economical solution for safe and efficient mine production. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0035] Figure 1 A flowchart for the combined reinforcement control of anchor bolts (cables) and grouting in the surrounding rock of a muddy, weakly cemented roadway.

[0036] Figure 2 Schematic diagram of shallow hole grouting technology for roadways with weak cemented mudstone.

[0037] Figure 3 Schematic diagram of deep hole grouting technology for roadways with weak cemented mudstone. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] Preparations before implementation

[0040] Before implementing this method, a detailed geological survey must be conducted to comprehensively obtain the physical and mechanical parameters, fracture development patterns, structural surface distribution, and hydrogeological conditions of the surrounding rock of the tunnel. This raw data is the fundamental basis for subsequent coordinated design of all parameters and directly affects the final effectiveness of reinforcement control.

[0041] Example 1

[0042] like Figures 1-3 As shown, this embodiment provides a typical method for reinforcing and controlling the surrounding rock of a muddy, weakly cemented roadway using a combination of anchor bolts (cables) and grouting. Its core lies in the systematic integration of "timely full-section sealing—stepwise differential grouting at varying depths—coordinated depth of anchor bolt and grouting parameters" to construct an "anchor-grouting synergistic bearing body" highly matched to the characteristics of the surrounding rock. The specific steps are as follows:

[0043] Step 1: Collaborative Design of Key Parameters

[0044] This step is fundamental to the entire method and aims to achieve optimal coupling between the grouting reinforcement range and the anchor (cable) support force field in terms of spatial and mechanical properties.

[0045] Step 1.1: Grouting Parameter Design: Based on the geological survey results, and considering the tunnel cross-sectional dimensions, the degree of surrounding rock fracturing, and the target reinforcement ring thickness, key parameters for shallow-hole grouting and deep-hole grouting are determined separately. Shallow-hole grouting focuses on filling and cementing the tension fractures within the shallow relaxation ring; therefore, a lower grouting pressure (usually designed to be 1-2 MPa) is used to ensure that the grout diffuses through penetration rather than fracturing, forming a dense and highly intact shallow reinforcement ring. Deep-hole grouting aims to improve the mechanical properties of deep rock masses; therefore, a higher grouting pressure (usually designed to be 3-4 MPa) is used to allow the grout to fracture and penetrate into deep primary fractures and weak surfaces. The diffusion radius of the grout is the core of this step's design, as it directly determines the extent of the effective reinforcement zone.

[0046] Step 1.2: Reverse Design of Support Parameters: Based on the grouting reinforcement range determined above, the support parameters for anchor bolts and cables are designed in reverse. The length of the anchor bolts must match the thickness of the shallow reinforcement ring to ensure that their anchoring ends are located within the effective shallow reinforcement zone; the length of the anchor cables must penetrate the deep reinforcement zone and anchor into deeper stable rock strata. Simultaneously, the spacing between anchor bolts (cables) must be coordinated with the effective diffusion radius of the grout, for example, it can be designed as 800mm × 800mm, to ensure that the support force field can completely cover the grouting reinforcement zone without any omissions. The design of the preload force must also match the mechanical properties of the reinforced surrounding rock to achieve active and timely radial restraint.

[0047] Step 2: Seal the surrounding rock across the entire cross section in a timely manner.

[0048] After the tunnel is excavated and formed, the entire tunnel surface (including the roof and sidewalls) must be sealed with shotcrete immediately. This process is crucial for controlling the initial deterioration of the surrounding rock. The resulting shotcrete layer should be dense and uniform, with a thickness of not less than 50 mm. This protective layer can quickly and effectively isolate the surrounding rock from moisture and oxygen in the air, significantly slowing down the weathering and deliquescence process of the weakly cemented mudstone, and providing a relatively stable working environment for subsequent grouting and support processes.

[0049] Step 3: Differential grouting reinforcement of deep and shallow holes in stages

[0050] This step employs a phased and differentiated grouting strategy, aiming to precisely reinforce the structural characteristics of surrounding rock at different depths.

[0051] Step 3.1: Shallow-hole low-pressure permeation grouting: After the full-section sealing layer reaches a certain strength, grouting holes are constructed in the shallow part of the surrounding rock of the roadway. Grouting is carried out at the relatively low pressure (1-2 MPa) as designed above. The grout is preferably a high-water-fast-setting material (exemplary water-cement ratio of 1.5:1). This type of material has the characteristics of good fluidity and fast setting speed, which can fully penetrate into the shallow tensile fractures, cement the fractured rock mass, and finally form a "shallow reinforcement ring" with high integrity and significant bearing capacity. This reinforcement ring not only improves the self-stabilizing ability of the shallow surrounding rock and prevents further intrusion of water hazards, but also provides a pressure-bearing foundation for subsequent deep-hole grouting and creates a reliable anchoring base for the ends of the anchor bolts.

[0052] Step 3.2: Deep-hole high-pressure fracturing-penetration grouting: After the shallow reinforcement ring has formed and reached the predetermined strength, deep grouting holes are constructed in the deep surrounding rock. Grouting is performed using the aforementioned high pressure (3-4 MPa). Under this pressure, the grout not only penetrates but also fractures deep primary fractures and weak surfaces, thereby significantly improving the mechanical properties of the deep surrounding rock and forming a "deep reinforcement zone" effectively connected to the shallow reinforcement ring. This reinforcement zone acts as a deep "bearing skeleton," working together with the shallow reinforcement ring to greatly enhance the integrity and self-supporting capacity of the surrounding rock.

[0053] Step 4: High-strength anchor bolts (cables) and active support

[0054] This step is crucial for forming the final synergistic load-bearing structure, emphasizing the coupling of construction sequence and mechanics.

[0055] Step 4.1: Support Sequence Control: The installation of anchor bolts (cables) should be carried out promptly after the grouting operation is completed and the grout has reached more than 70% of its design strength. This ensures that the support components are installed in a modified and stable rock mass environment.

[0056] Step 4.2: Precise Installation: Strictly follow the parameters of the collaborative design in S1 to drill holes at the predetermined locations and install high-strength anchor bolts and anchor cables. It must be ensured that the anchoring end of the anchor bolt is within the effective range of the shallow reinforcement ring, while the anchoring end of the anchor cable extends into the deep reinforcement zone or even deeper stable rock strata.

[0057] Step 4.3: Applying High Preload: Apply high preload to the installed anchor bolts (cables) using specialized tensioning equipment. This step is the core of achieving "active support," ensuring close coupling between the support system and the grout-reinforced surrounding rock, actively providing radial constraint force, and effectively suppressing surrounding rock deformation. At this point, the grout-reinforced body and the support system together constitute a "grout-grout synergistic load-bearing body" with matched mechanical properties and efficient load transfer.

[0058] Step 4.4: Auxiliary support: Finally, install auxiliary components such as metal mesh, steel strips or steel ladder beams, and fit them tightly with the anchor (cable) tray to form a complete support system.

[0059] Optional Implementation Plan

[0060] To adapt to different engineering conditions and cost considerations, this invention allows for flexible adjustments within its core framework:

[0061] The grouting material is not limited to high-water-rate quick-setting materials, but may also be cement-based composite grout or other chemical grouts that meet the engineering requirements.

[0062] The type (such as threaded steel anchor bolt, prestressed anchor cable, etc.), specific specifications and matching components of the anchor bolt (cable) can be selected and combined according to the actual support requirements.

[0063] In sections with extremely poor surrounding rock conditions or severe water hazards, it may be considered to add a re-grouting process after the initial grouting, based on the effect evaluation, or to make adaptive adjustments to parameters such as grouting pressure and grout mix ratio.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reinforcing and controlling the surrounding rock of a weakly cemented mud roadway using a combination of anchor bolts and grouting, characterized in that, Includes the following steps: S1. Collaborative design of key parameters: Based on the geological survey results, a systematic collaborative design of grouting parameters and anchor bolt support parameters is carried out. S2. Full-section timely sealing of surrounding rock: After the tunnel is excavated and formed, the surface of the tunnel is immediately sealed with full-section shotcrete. S3. Differential grouting reinforcement in shallow and deep holes: low-pressure permeation grouting is carried out in the shallow part of the surrounding rock and high-pressure fracturing-permeation grouting is carried out in the deep part of the surrounding rock to form a shallow reinforcement ring and a deep reinforcement zone. S4. High-strength anchor bolts work together to provide active support. After the grouting solid reaches the design strength, the anchor bolts are installed and a high preload is applied, so that the support system and the grouting solid are coupled to form a co-supporting body.

2. The method for combined reinforcement and control of rock mass anchoring and grouting in a muddy, weakly cemented roadway according to claim 1, characterized in that, The specific content of step S1 is as follows: S1.

1. Based on the tunnel cross-sectional dimensions, the degree of surrounding rock fragmentation, and the target reinforcement ring thickness, determine the grouting pressure, grouting time, and grout diffusion radius for shallow and deep holes; S1.

2. Based on the grouting reinforcement range, design the length, diameter, spacing and preload of the anchor rods and anchor cables in reverse order to ensure that the anchoring ends of the support components are all located within the effective grouting reinforcement zone and achieve coupling.

3. The method for combined reinforcement and control of rock mass anchoring and grouting in a weakly cemented mud roadway according to claim 1, characterized in that, In step S2, the thickness of the protective layer formed by the sprayed concrete seal is not less than 50 mm.

4. The method for combined reinforcement and control of rock mass anchoring and grouting in a muddy, weakly cemented roadway according to claim 1, characterized in that, The specific content of step S3 is as follows: S3.1 Shallow-hole low-pressure permeation grouting: After the full-section sealing layer reaches the design strength, grouting holes are constructed in the shallow part of the surrounding rock of the roadway. The grout is filled into the shallow tension fractures and cemented broken rock mass by low-pressure permeation to form a shallow reinforcement ring. S3.2 Deep Hole High-Pressure Fracturing-Permeation Grouting: After the shallow reinforcement ring is formed and reaches the predetermined strength, deep grouting holes are constructed in the deep part of the surrounding rock. Grouting is carried out in a high-pressure manner. Under high pressure, the grout splits and permeates the deep original fractures and weak surfaces to form a deep reinforcement zone that is effectively connected with the shallow reinforcement ring.

5. The method for combined reinforcement and control of rock mass anchoring and grouting in a muddy, weakly cemented roadway according to claim 4, characterized in that, The shallow low-pressure permeation grouting uses a grouting pressure of 1-2 MPa and a high-water-rate-setting material as the grout.

6. The method according to claim 4, characterized in that, The deep high-pressure fracturing-penetration grouting uses a grouting pressure of 3-4 MPa.

7. The method for combined reinforcement and control of surrounding rock in a weakly cemented mud roadway according to claim 1, characterized in that, The specific content of step S4 is as follows: S4.1 Anchor bolts shall be installed after the grouting operation is completed and the solidified grout reaches more than 70% of the design strength. S4.2 According to the collaborative design parameters, drill holes at predetermined locations and install high-strength anchor bolts and anchor cables. The anchoring end of the high-strength anchor bolt is located within the effective range of the shallow reinforcement ring, and the anchoring end of the anchor cable extends into the deep reinforcement zone. S4.3, using specialized tensioning equipment to apply high preload to the anchor bolts, making them tightly coupled with the grout-reinforced surrounding rock, actively providing radial constraint, and together forming an efficient "anchor-grout synergistic bearing body"; S4.4, Install metal mesh, steel strips or reinforced ladder beams to form a complete support system.

8. The method for combined reinforcement and control of surrounding rock in a weakly cemented mud roadway according to claim 1, characterized in that, In step S1 or S3, the grouting material used is one of the following: high water content quick-setting material, cement-based composite grout, or chemical grout.

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