A kind of slope broken rock mass integral reinforcing structure and construction method

Abstract

The application discloses a kind of whole reinforcing structure of side slope broken rock mass and construction method, belong to side slope engineering reinforcement technical field.The reinforcing structure includes hollow steel pipe, double-layer steel mesh and shotcrete, hollow steel pipe is divided into grouting section embedded in rock mass and exposed shotcrete section, grouting section side wall is provided with grouting hole and the bottom is provided with the opening cone structure that can expand outward, lower steel mesh is fixed with grouting section and adheres slope face, upper steel mesh is fixed with shotcrete section and is spaced apart with lower steel mesh, shotcrete covers upper steel mesh and shotcrete section and fills inside hollow steel pipe.Solve the problem that traditional anchor shotcrete mode is poor in reinforcing effect to thick broken rock mass, prone to secondary landslide due to rainwater erosion, realize the layered overall reinforcement of broken rock mass from inside to slope face, effectively improve the stability and anti-slippage ability of side slope, convenient for construction, adapt to a variety of broken slope working conditions.

Description

Technical Field

[0001] This invention relates to the field of tunnel slope engineering reinforcement technology, specifically to an integral reinforcement structure for fractured rock mass slopes and its construction method. Background Technology

[0002] In tunnel and underground engineering construction, the reinforcement and support of fractured surrounding rock sections is a core element in ensuring construction safety and long-term structural stability. Traditional initial tunnel support commonly employs a shotcrete-anchor support system combining anchor bolts with steel mesh and shotcrete. This system anchors the surrounding rock and seals the rock surface with shotcrete, achieving initial reinforcement of the surrounding rock. It is widely used in rock support operations for various underground engineering projects such as railway tunnels, highway tunnels, and water conservancy tunnels.

[0003] However, in tunnel sections with highly fractured surrounding rock and thick fault fracture zones, conventional anchor bolts can only achieve single-point anchoring and cannot comprehensively cement and fill the intersecting fissures within the surrounding rock. The support structure and the deep fractured surrounding rock cannot form a cohesive whole for load-bearing. Under the long-term effects of groundwater seepage and stress redistribution in the surrounding rock, problems such as loosening and spalling of the surrounding rock, cracking of the sprayed layer, and water leakage are likely to occur. In severe cases, this can even lead to local collapses and instability of the support structure, directly affecting tunnel construction safety and operational durability. Furthermore, existing support schemes largely rely on engineering experience for parameter selection, lacking quantitative design calculation methods for surrounding rock with different fracture depths and lithologies, resulting in poor controllability of support quality and safety reserves.

[0004] Therefore, there is an urgent need for an integrated reinforcement structure that can integrate deep grouting reinforcement and surface support of fractured surrounding rock in tunnels, improve the integrity of the fractured surrounding rock and the synergistic stress-bearing capacity of the support system, and ensure the construction safety and long-term service performance of tunnel projects. Summary of the Invention

[0005] This invention aims to solve the problems of poor reinforcement effect, insufficient integrity, and susceptibility to secondary landslides and seepage caused by rainwater erosion in the existing traditional anchor bolt shotcrete support for thick fractured rock masses. It provides an integral reinforcement structure and construction method for fractured rock masses on slopes.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On one hand, an integral reinforcement structure for fractured rock slopes includes a hollow steel pipe, a reinforcing mesh, and shotcrete. The hollow steel pipe comprises a grouting section and a shotcrete section. The grouting section is embedded within the fractured rock mass, while the shotcrete section is exposed on the slope surface. The reinforcing mesh comprises a lower layer and an upper layer. The lower layer is fixedly connected to the grouting section and adhered to the fractured rock slope surface. The upper layer is fixedly connected to the shotcrete section, and the upper and lower layers are spaced apart. Grouting holes are provided on the sidewalls of the grouting section, and an outwardly expanding conical structure is provided at the bottom of the grouting section. The shotcrete covers the upper reinforcing mesh and the shotcrete section, and fills the hollow steel pipe.

[0008] Furthermore, the upper steel mesh is welded and fixed at a position 3-5cm away from the end of the shotcrete section.

[0009] Furthermore, it also includes diagonal reinforcing bars, which are welded and fixed to the transversely arranged hollow steel pipes and the longitudinally arranged hollow steel pipes, respectively.

[0010] Furthermore, the diameter of the diagonal reinforcing bars is larger than the diameter of the reinforcing bars in the steel mesh.

[0011] Furthermore, the lower layer of reinforcing mesh is welded and fixed to the grouting section, and the upper layer of reinforcing mesh is connected to the diagonal reinforcing bars by binding.

[0012] Furthermore, the outer diameter D of the hollow steel pipe satisfies the following design calculation formula:

[0013]

[0014] In the formula, G is the maximum shear force borne by the hollow steel pipe, t is the ratio of the inner and outer diameters of the hollow steel pipe, and [τ] is the maximum shear strength of the hollow steel pipe.

[0015] Furthermore, the lower layer of reinforcing mesh is welded to the side of the hollow steel pipe, and the hollow steel pipe of the same lower layer of reinforcing mesh is arranged along both sides of the reinforcing bar.

[0016] On the other hand, a construction method for an integral reinforcement structure for fractured rock mass slopes includes the following steps:

[0017] S1. Based on the geological survey report, determine the rock mass fracture depth, calculate the shear resistance parameters of the hollow steel pipe, and process the hollow steel pipe into a structure with grouting holes on the side wall and an open conical shape at the bottom.

[0018] S2. Install the hollow steel pipe on the fractured slope, so that the grouting section of the hollow steel pipe is buried inside the fractured rock mass, and the shotcrete section is exposed on the surface of the fractured slope.

[0019] S3. High-pressure grouting is performed into the hollow steel pipe. Grouting is stopped when grout continuously emerges from the side wall of the hollow steel pipe.

[0020] S4. Fix the lower layer of steel mesh to the grouting section and fix the upper layer of steel mesh to the shotcrete section.

[0021] S5. Spray concrete from top to bottom, so that the concrete covers the upper steel mesh and the sprayed concrete section to form an integral reinforced structure.

[0022] Furthermore, in step three, after stopping grouting, let it stand for 3-5 minutes. If there is no sinking of the grout on the side wall of the hollow steel pipe, the grouting operation is considered complete.

[0023] Furthermore, after step four is completed, diagonal reinforcing bars are welded between the horizontally arranged hollow steel pipes and the longitudinally arranged hollow steel pipes.

[0024] Compared with existing technologies, the present invention has the following significant advantages:

[0025] 1. The structure of hollow steel pipe grouting combined with double-layer steel mesh shotcrete is adopted to achieve integrated reinforcement of internal cracks in fractured rock mass and surface support of slope, which significantly improves the integrity and anti-sliding capacity of thick fractured slopes.

[0026] 2. The bottom of the hollow steel pipe is equipped with an expandable conical structure, which, together with the grouting holes on the side wall, can achieve omnidirectional grouting from the bottom and sides, fully filling the voids in the rock mass, blocking the rainwater infiltration path, and preventing the rock mass from deteriorating.

[0027] 3. The overall structure is flexible, with clear parameter design methods and construction processes, adaptable to slope conditions with different fracture depths, and the construction quality is controllable, which can effectively reduce the long-term operation risks of the project. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the integral reinforcement structure according to an embodiment of the present invention. Figure 1 ;

[0029] Figure 2 This is a schematic diagram of the integral reinforcement structure according to an embodiment of the present invention. Figure 2 ;

[0030] Figure 3 This is a schematic plan view of the integral reinforcing structure according to an embodiment of the present invention;

[0031] Figure 4 This is a side view schematic diagram of the integral reinforcing structure according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of a hollow steel pipe structure according to an embodiment of the present invention;

[0033] Figure 6 for Figure 5 A magnified view of a portion of the image;

[0034] Figure 7 This is a schematic diagram of the construction method according to an embodiment of the present invention.

[0035] Among them, 1. Hollow steel pipe; 11. Shotcrete section; 12. Grouting section; 13. Grouting hole; 14. Conical structure; 141. Conical head; 2. Reinforcing mesh; 21. Lower reinforcing mesh; 22. Upper reinforcing mesh; 3. Shotcrete; 4. Diagonal reinforcing bars. Detailed Implementation

[0036] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0037] The following is combined with Figures 1 to 7 The following describes embodiments of the present invention.

[0038] According to an embodiment of the present invention, an integral reinforcement structure for fractured rock mass slope is provided, comprising a hollow steel pipe 1, a reinforcing mesh 2, and shotcrete 3. The hollow steel pipe 1 includes a grouting section 12 and a shotcrete section 11. The grouting section 12 is embedded inside the fractured rock mass, while the shotcrete section 11 is exposed on the slope surface of the fractured rock mass. The reinforcing mesh 2 includes a lower reinforcing mesh 21 and an upper reinforcing mesh 22. The lower reinforcing mesh 21 is fixedly connected to the grouting section 12 and attached to the slope surface of the fractured rock mass. The upper reinforcing mesh 22 is fixedly connected to the shotcrete section 11, and the upper and lower reinforcing meshes are spaced apart. Grouting holes 13 are provided on the sidewall of the grouting section 12, and an outwardly expanding conical structure 14 is provided at the bottom of the grouting section 12. The shotcrete 3 covers the upper reinforcing mesh 22 and the shotcrete section 11, and fills the hollow steel pipe 1.

[0039] Specifically, the hollow steel pipe 1 serves as the internal grouting channel and anchors the external reinforcing mesh 2, integrating the internal rock mass reinforcement with the slope support structure to ensure the continuity of force transmission in the reinforcement system. In practical engineering applications, seamless welded steel pipes are preferred for the hollow steel pipe 1, with Q235 or Q355 series structural steel selected based on the slope load level. For high-intensity earthquake zones or slopes with large landslide thrust, low-alloy high-strength steel pipes can be used to improve shear and tensile bearing capacity under the same cross-sectional dimensions. The wall thickness of the hollow steel pipe 1 needs to be designed uniformly based on the ratio of the outer diameter to the inner diameter, typically not less than 4mm, to avoid buckling deformation of the pipe wall during rock driving and to ensure structural stability under high grouting pressure. The surface of the hollow steel pipe 1 can be treated with rust removal and then coated with epoxy anti-rust primer to reduce the risk of corrosion during long-term service, especially in rainy, high-humidity, or corrosive groundwater environments, effectively extending the overall service life of the structure.

[0040] Grouting section 12 is the part of the hollow steel pipe 1 embedded in the rock mass. Through sidewall grouting and bottom expansion, it achieves deep bonding with the fractured rock mass, diffusing the anchoring force of the steel pipe to the surrounding rock mass and improving the integrity of the rock mass. Shotcrete section 11 is the part of the hollow steel pipe 1 exposed on the slope surface. It provides welding fixing points for the upper steel mesh 22 and is also wrapped with shotcrete 3, becoming the internal skeleton of the slope support surface layer and enhancing the shear and impact resistance of the surface layer.

[0041] The reinforcing mesh 2 serves as a strengthening component for slope support, arranged in two layers. This significantly improves the tensile and crack resistance of the shotcrete surface layer 3, while simultaneously connecting the dispersed hollow steel pipes 1 into a unified support system. The double-layer reinforcing mesh 2 arrangement allows the shotcrete surface layer 3 to form a load-bearing structure similar to a composite beam: the lower reinforcing mesh 21 primarily bears the compressive stress and interfacial shear force on the side closest to the rock mass, constraining the outward deformation of the shallow fractured rock mass; the upper reinforcing mesh 22 primarily bears the tensile stress on the outer side of the surface layer, resisting the tensile strain generated by slope unloading rebound, temperature stress, and rainwater infiltration and expansion. The two layers of reinforcing mesh 2 are rigidly connected by the hollow steel pipes 1, working together to form a reinforced concrete layer with overall load-bearing capacity. Compared to the traditional single-layer reinforcing mesh 2 shotcrete structure, the surface layer exhibits significantly improved flexural bearing capacity and ultimate crack resistance, effectively avoiding common defects such as longitudinal cracking and localized hollowing and spalling that are prone to occur in traditional shotcrete surface layers. The mesh size of the steel mesh 2 needs to match the average particle size of the broken rock mass. The mesh side length is usually set to 15-25cm, which can effectively protect the broken rocks on the slope and prevent small rock fragments from peeling off. For broken rock masses with larger block diameters, the mesh can be appropriately densified to further enhance the passive protection capability of the slope.

[0042] The lower layer of reinforcing mesh 21 is directly attached to the fractured rock slope and fixedly connected to the grouting section 12. It provides initial restraint for the shallow fractured rock mass on the slope, preventing rock fragments from peeling off, and also provides bottom support for the upper support structure. The upper layer of reinforcing mesh 22 is fixed to the shotcrete section 11 and is spaced apart from the lower layer of reinforcing mesh 21. It is located on the outer side of the inner part of the shotcrete surface layer 3, which can improve the overall bending and crack resistance of the surface layer and enhance the durability of the slope support.

[0043] Grouting holes 13 are located on the sidewall of grouting section 12. During high-pressure grouting, the grout diffuses through the holes into the surrounding rock fissures, achieving cementation and anchoring between the steel pipe and the surrounding rock mass, expanding the grouting reinforcement range, and improving the integrity of the rock mass. The arrangement of grouting holes 13 needs to be designed in conjunction with the degree of fissure development in the fractured rock mass. Under normal working conditions, a staggered, quincunx arrangement is adopted, with 3-4 rows of holes evenly arranged circumferentially. This spacing ensures that the grout diffusion range of adjacent holes fully overlaps, avoiding grouting blind spots. If the spacing is too small, it will excessively weaken the cross-sectional strength of the steel pipe; if it is too large, it will easily lead to discontinuous grout filling. The diameter of grouting holes 13 is usually set to 6-12mm, which ensures the smooth flow of cement grout and prevents rock debris from entering the channel and causing blockage during the steel pipe driving process. Before grouting construction, a biodegradable paper sealing film can be temporarily pasted on the outside of the hole to prevent soil particles from entering the channel during the installation of the hollow steel pipe 1. The sealing film will automatically rupture under pressure during grouting without affecting the normal diffusion of the grout.

[0044] A conical structure 14 is located at the bottom of the grouting section 12. During high-pressure grouting, it expands outward under the pressure of the grout, opening up the voids in the bottom rock mass and filling them with grout. This achieves bottom-expanding anchorage at the end of the steel pipe, significantly improving the pull-out and shear bearing capacity of the hollow steel pipe 1. Specifically, the conical structure 14 adopts a two-lobed prefabricated cone head 141 structure. The cone head 141 is connected to the main body of the steel pipe by spot welding. In the initial state, the cone head 141 is closed into a cone shape, which facilitates the smooth driving of the hollow steel pipe 1 into the rock mass and reduces drilling or driving resistance. When the grouting pressure reaches a set threshold, the grout pressure pushes the cone head 141 to expand outward, forming an expanded-diameter anchorage section at the end of the hollow steel pipe 1. The expanded anchoring end significantly enhances the pull-out bearing capacity of the steel pipe. Compared to ordinary anchor rods of the same diameter, the ultimate pull-out force of a single hollow steel pipe 1 can be greatly increased. Simultaneously, the spherical grout bubbles formed after bottom expansion fill the voids in the end rock mass, evenly distributing the end load to the surrounding intact rock mass, thus preventing localized crushing failure of the rock mass due to stress concentration. For slopes with extremely high fracture degree and a fractured layer thickness greater than 5m, a double-stage conical structure can be adopted, adding a set of expanding cones 141 in the lower part of the grouting section 12 to achieve multi-point expanded anchoring, further improving the anchoring reliability and overall anti-sliding capacity of the hollow steel pipe 1.

[0045] Shotcrete 3 is the main surface layer of the slope support. After covering the upper steel mesh 22 and the shotcrete section 11, it forms a continuous support surface layer, which isolates external rainwater and weathering. At the same time, it connects the double-layer steel mesh 2 and the hollow steel pipe 1 into a whole, which together bear the lateral pressure of the slope rock mass.

[0046] In some embodiments, the upper reinforcing mesh 22 is welded and fixed at a position 3-5 cm from the end of the shotcrete section 11. Specifically, the welding position of the upper reinforcing mesh 22 directly affects the protective layer thickness and structural performance of the shotcrete 3 surface layer. Setting the upper reinforcing mesh 22 at a position 3-5 cm from the end of the shotcrete section 11 ensures that the outer side of the reinforcing mesh 2 has sufficient concrete protective layer thickness, preventing exposed and corroded reinforcing bars, while placing the reinforcing mesh 2 at the optimal cross-sectional position for surface layer stress, fully utilizing its tensile strengthening effect. If the distance is less than 3 cm, the outer concrete protective layer will be too thin, making the reinforcing bars susceptible to external environmental erosion, and the reinforcing bars will easily be exposed and damaged when the surface layer is impacted; if the distance is greater than 5 cm, the upper reinforcing mesh 22 is too inward, failing to effectively improve the crack resistance of the outer side of the surface layer, and cracks will easily appear on the surface of the surface layer. The preferred welding position is 4 cm from the end of the shotcrete section 11, balancing the protective layer thickness and structural structural performance.

[0047] In some embodiments, the system further includes diagonal reinforcing bars 4, which are welded and fixed to the transversely arranged hollow steel pipes 1 and the longitudinally arranged hollow steel pipes 1, respectively. The diagonal reinforcing bars 4 connect the transversely and longitudinally arranged hollow steel pipes 1, forming a stable force-bearing system within the slope plane. This enhances the overall shear and deformation resistance of the support structure, preventing overall misalignment of the support structure when shear slip occurs along the slope surface, and improving the integrity and stability of the reinforcement system. The diagonal reinforcing bars 4 and the transversely and longitudinally arranged hollow steel pipes 1 together constitute a planar truss force-bearing system, which can evenly transfer the horizontal shear force within the slope surface to each steel pipe anchor point, preventing single steel pipe failure due to excessive local load. This truss force-bearing system is particularly suitable for layered fractured slopes with a risk of bedding plane slip, effectively constraining the shear deformation of the rock mass along the bedding plane. The connection between the diagonal reinforcing bars 4 and the hollow steel pipes 1 requires double-sided full welding, with a weld length not less than 5 times the diameter of the reinforcing bar, ensuring the reliability of force transmission at the joint and preventing shear failure of the welded joint before the reinforcing bar itself.

[0048] Furthermore, the diameter of the diagonal reinforcing bar 4 is larger than the diameter of the reinforcing bar in the steel mesh 2. The diagonal reinforcing bar 4 mainly bears the shear force transfer, and its stress level is higher than that of the ordinary steel mesh 2. Using a larger diameter reinforcing bar can ensure its shear and tensile bearing capacity, prevent the reinforcing bar from yielding and failing before other components of the support system, and ensure the overall structural safety reserve.

[0049] In some embodiments, the lower reinforcing mesh 21 is welded to the grouting section 12, and the upper reinforcing mesh 22 is connected to the diagonal reinforcing bar 4 by binding. Welding the lower reinforcing mesh 21 to the grouting section 12 ensures connection strength and effective force transfer between the hollow steel pipe 1 and the reinforcing mesh 2. Binding the upper reinforcing mesh 22 to the diagonal reinforcing bar 4 allows for flexible adjustments during on-site construction, reduces on-site welding workload, improves construction efficiency, and meets the stress connection requirements of the splicing area.

[0050] In some embodiments, the outer diameter D of the hollow steel pipe 1 satisfies the following design calculation formula:

[0051]

[0052] In the formula, G is the maximum shear force borne by the hollow steel pipe 1, t is the ratio of the inner and outer diameters of the hollow steel pipe 1, and [τ] is the maximum shear strength of the hollow steel pipe 1.

[0053] Specifically, this formula is derived based on the shear strength theory of mechanics of materials and the overall stress model of slope reinforcement. Hollow steel pipe 1 is taken as the core shear-resistant component of the slope reinforcement system. Combining the shear bearing capacity of the steel pipe section with the shear load under the most unfavorable slope conditions, the minimum design value of the outer diameter of the steel pipe is determined to ensure that hollow steel pipe 1 does not undergo shear failure under slope sliding loads. The derivation of this design formula is based on the limit equilibrium theory of slopes and the shear strength criterion of mechanics of materials. First, the reinforcement area corresponding to a single hollow steel pipe 1 is taken as an independent calculation unit. The tangential component of the self-weight of the fractured rock mass, the self-weight of the support structure, and the additional load generated by rainfall infiltration within the calculation unit, along the potential shear plane, is the maximum shear force G that hollow steel pipe 1 needs to bear. For seismic fortification areas, the horizontal shear force generated by the seismic action also needs to be superimposed to ensure structural safety reserves under the most unfavorable conditions.

[0054] The shear capacity of the hollow steel pipe 1 is determined by the effective shear area of ​​the pipe wall and the allowable shear strength of the material. For a hollow circular pipe section, the effective shear area is approximately taken as the annular cross-sectional area of ​​the pipe wall, i.e. Where d is the inner diameter of the steel pipe, and satisfies According to the shear strength condition, the shear stress at the critical section must satisfy... By substituting and rearranging the formula for the area of ​​the annular cross-section, the design calculation formula for the outer diameter D can be obtained. This formula avoids material waste or insufficient safety reserves caused by empirical selection. In addition to shear control, for high slopes with large anchorage depths, it is also necessary to simultaneously verify the pull-out bearing capacity and compression stability of the hollow steel pipe 1 to ensure that the hollow steel pipe 1 will not experience pull-out failure or buckling instability under the synergistic effect of the grouting body, thus forming a complete design system with multiple control indicators.

[0055] Design Example: For a fractured rock slope with a slope angle of 45°, an average depth of 3m, a rock mass unit weight of 25kN / m³, and a total self-weight of the support structure of 2kN / m², a single hollow steel pipe 1 supports a slope reinforcement area of ​​4m². Calculations show that the shear load generated by the self-weight of the fractured rock mass is 25×3×4×cos45°≈212.1kN, and the shear load generated by the self-weight of the support structure is 2×4×cos45°≈5.66kN. Therefore, the maximum shear force G borne by a single hollow steel pipe 1 is approximately 217.76kN. A Q235 welded steel pipe is selected, with a maximum shear strength [τ] of 120MPa. The ratio of the inner and outer diameters of the steel pipe, t, is chosen to be 0.8. Substituting the parameters into the formula, D≥89.2mm. Considering commonly used steel pipe specifications in engineering, a hollow steel pipe 1 with an outer diameter of 100mm is selected, meeting the shear strength design requirements.

[0056] In some embodiments, the lower reinforcing mesh 21 is welded to the side of the hollow steel pipe 1, and the hollow steel pipe 1 of the same lower reinforcing mesh 21 is arranged along both sides of the reinforcing bar. Welding the lower reinforcing mesh 21 to the side of the hollow steel pipe 1 can prevent the reinforcing mesh 2 from protruding from the slope surface, ensuring that the reinforcing mesh 2 is tightly attached to the rock surface and improving the restraint effect on shallow fractured rock mass. The arrangement of steel pipes on both sides of the same reinforcing bar can make the force of a single reinforcing bar evenly transmitted through the hollow steel pipes 1 on both sides, avoiding bending failure of the reinforcing bar due to single-point stress, and improving the overall flatness and fixing firmness of the reinforcing mesh 2.

[0057] According to an embodiment of the present invention, another aspect provides a construction method for an integral reinforcement structure for fractured rock mass slopes, comprising the following steps:

[0058] S1. Based on the geological survey report, determine the rock mass fracture depth, calculate the shear resistance parameters of hollow steel pipe 1, and process hollow steel pipe 1 to form sidewall grouting holes 13 and bottom conical structure 14.

[0059] S2. Install the hollow steel pipe 1 on the fractured slope, so that the grouting section 12 of the hollow steel pipe 1 is buried inside the fractured rock mass, and the shotcrete section 11 is exposed on the slope surface of the fractured rock mass.

[0060] S3. High-pressure grouting is performed into the hollow steel pipe 1. Grouting is stopped when grout continuously emerges from the side wall of the hollow steel pipe 1.

[0061] S4. Fix the lower layer steel mesh 21 to the grouting section 12 and fix the upper layer steel mesh 22 to the shotcrete section 11.

[0062] S5. Spray concrete 3 from top to bottom, so that the concrete covers the upper steel mesh 22 and the sprayed concrete section 11 to form an overall reinforced structure.

[0063] Step S1 is the preliminary design and component processing stage. The extent and depth of rock mass fracture are determined through geological survey, and the specifications and parameters of steel pipes are determined by mechanical calculation. Hollow steel pipe components with grouting holes 13 and conical structures 14 are prefabricated in advance to prepare for on-site construction and ensure the accuracy and adaptability of subsequent construction.

[0064] Step S2 is the steel pipe installation stage. Hollow steel pipes 1 are driven or implanted into the fractured slope rock mass according to the designed spacing. The length of the exposed section is controlled to ensure that the grouting section 12 completely enters the fractured rock layer, providing a foundation for subsequent grouting and the installation of the reinforcing mesh 2. The installation of hollow steel pipes 1 in step two requires selecting the appropriate construction technology based on the hardness and degree of fracture of the rock mass. For strongly weathered or completely weathered fractured rock masses with relatively low hardness, a direct driving method can be used. A vibratory pile driver is used to drive the hollow steel pipes 1 into the designated depth at the designed angle, resulting in high construction efficiency and minimal disturbance to the surrounding rock mass. For medium-hard fractured rock masses or slopes containing large boulders, a geological drilling rig must first be used to drill holes. After drilling, high-pressure air is used to clean the holes, removing rock powder and debris. Then, the hollow steel pipes 1 are smoothly placed into the holes, followed by grouting operations.

[0065] Step S3 is the high-pressure grouting stage. Cement grout is injected into the hollow steel pipe 1. The grout diffuses from the grouting holes 13 on the side wall and the conical structure 14 at the bottom to the surrounding rock fissures. Continuous grout seepage from the side wall indicates that the surrounding fissures have been basically filled, achieving cementation and reinforcement of the fractured rock mass and improving its overall integrity. The high-pressure grouting in step S3 can be performed using a one-time full-section grouting or segmented grouting process. For slopes with deeper fractures, segmented grouting from bottom to top is preferred to ensure the filling effect of deep fissures. The grout is mainly composed of ordinary silicate cement grout with a cement strength grade of not less than 42.5. The water-cement ratio is dynamically adjusted according to the permeability of the rock mass: for highly permeable, strongly fractured rock masses, the water-cement ratio is 0.6-0.8 to ensure the long-distance diffusion capacity of the grout; for less permeable fractured rock masses, the water-cement ratio is 0.45-0.55 to improve the early and final strength of the grout. For slopes with abundant water or high groundwater levels, an appropriate amount of water glass can be added to the grout as a quick-setting agent, at a dosage of 2%-4% of the cement mass. This shortens the initial setting time of the grout and prevents it from being washed away by groundwater. During grouting, the grouting pressure must be strictly controlled. The initial pressure should be controlled at 0.5-1.0 MPa, and then gradually increased to the design final pressure, maintaining the pressure for 2-3 minutes to ensure the grout fully fills the rock fissures. If large-scale grout seepage occurs on the slope surface during construction, the grouting pressure should be reduced promptly or intermittent grouting should be adopted to ensure that the grout effectively fills the internal fissures of the rock mass, rather than flowing away along the slope surface.

[0066] Furthermore, in step three, after stopping grouting, allow the grout to stand for 3-5 minutes. If there is no sinking of the grout on the sidewall of the hollow steel pipe 1, the grouting operation is considered complete. This standing observation step verifies the fullness of the grout filling, preventing the grout level from dropping due to incomplete filling of internal cracks, which would affect the grouting reinforcement effect. A standing time of 3-5 minutes fully reflects the stable filling state of the grout. If the standing time is less than 3 minutes, the internal grout has not fully penetrated and settled, making it impossible to accurately judge the fullness of the filling; if the standing time is greater than 5 minutes, the grout begins to set, and even if voids exist, they cannot be filled, reducing construction efficiency. A standing time of 4 minutes is preferred, balancing the accuracy of grout quality judgment with construction efficiency. If there is no sinking of the grout on the sidewall after standing, it indicates that the surrounding rock fissures have been completely filled by the grout, and the grouting effect meets the standards.

[0067] Step S4 is the installation stage of the reinforcing mesh 2. The lower reinforcing mesh 21 and the upper reinforcing mesh 22 are fixed sequentially, ensuring that both layers of reinforcing mesh 2 are firmly connected to the corresponding sections of the steel pipes, forming the skeleton system of the slope support and providing internal reinforcement support for the shotcrete 3. Further, after step four is completed, diagonal reinforcing bars 4 are welded between the transversely arranged hollow steel pipes 1 and the longitudinally arranged hollow steel pipes 1. Welding the diagonal reinforcing bars 4 after the installation of the double-layer reinforcing mesh 2 creates diagonal force-transmitting components between the longitudinal and transverse hollow steel pipes 1, further enhancing the planar integrity of the support structure and improving the slope's resistance to shear slippage. This process is arranged after the installation of the reinforcing mesh 2 to avoid interference from the reinforcing bars in the laying and positioning of the reinforcing mesh 2, ensuring a smooth on-site construction sequence.

[0068] Step S5 is the construction stage of shotcrete 3. The top-down spraying sequence can avoid concrete flow and accumulation, ensure uniform surface thickness, and after the concrete completely covers the upper steel mesh 22 and the shotcrete section 11 of the hollow steel pipe 1, a complete slope support surface layer is formed, and finally the internal grouting reinforcement and external shotcrete support are integrated.

[0069] In actual engineering construction, the slope geological survey is carried out first. Through drilling, geophysical exploration and other means, the distribution range, depth, degree of rock fragmentation and the location of the intact rock mass below are determined, and the physical and mechanical parameters of the rock mass are obtained as the basis for subsequent structural design. Based on the survey results, the shear load borne by a single hollow steel pipe 1 is calculated. Combined with the material properties of the steel pipe, the outer diameter, wall thickness and total length of the hollow steel pipe 1 are determined. The length of the grouting section 12 matches the depth of rock fragmentation, and the length of the shotcrete section 11 is determined according to the designed thickness of the shotcrete 3.

[0070] Subsequently, hollow steel pipe components 1 are prefabricated in the factory. Grouting holes 13 are drilled on the side wall of the grouting section 12 according to the design spacing. The diameter of the holes is usually 6-12mm, and they are arranged in a quincunx pattern to ensure that the grout can spread evenly in all directions. The bottom of the hollow steel pipe 1 is processed into an outwardly expanding conical structure 14, using a prefabricated segmented cone head 141 with an internal expansion gap. During high-pressure grouting, the cone head 141 opens outward under the pressure of the grout, realizing end expansion.

[0071] After the component processing is completed, on-site construction preparation is carried out. Loose rocks and debris on the slope surface are cleared, the slope surface is leveled, and the installation positions of hollow steel pipe 1 are marked according to the design points. Hollow steel pipe 1 is installed by drilling or driving, ensuring that hollow steel pipe 1 is perpendicular to the slope surface or inserted at the design angle. Grouting section 12 is completely inserted into the bottom of the fractured rock mass, with the end extending 0.5-1m into the intact rock mass to improve anchoring stability. Shotcrete section 11 is evenly exposed on the slope surface, with a consistent exposed length.

[0072] After the hollow steel pipe 1 is installed, high-pressure grouting is performed using pure cement grout, and the grouting pressure is gradually increased to the design pressure. During the grouting process, the grout discharge from the side wall of the hollow steel pipe 1 is observed. When grout continuously and evenly emerges from multiple grouting holes 13, the grouting valve is initially closed, and the pipe is left to stand for 3-5 minutes for observation. If there is no obvious sinking of the grout surface on the side wall, it indicates that the surrounding cracks are fully filled, and grouting can be terminated. If the grout surface sinks, grouting needs to be added until the grout surface stabilizes. After the grout has initially set, the residual grout at the pipe opening is cleaned.

[0073] After the grout reaches more than 70% of its design strength, the reinforcing mesh 2 is laid. First, the lower layer of reinforcing mesh 21 is laid. Reinforcing mesh 2 is made of φ8 threaded steel bars and is laid close to the slope surface, welded and fixed to the exposed side of the hollow steel pipe 1 grouting section 12. The upper layer of reinforcing mesh 22 is connected by binding at the joints. After the lower layer of reinforcing mesh 21 is laid, the upper layer of reinforcing mesh 22 is welded 3-5cm from the end of the shotcrete section 11. The upper layer of reinforcing mesh 22 has the same specifications as the lower layer. The two layers of reinforcing mesh 2 are arranged parallel to each other, with spacing matching the exposed length of the shotcrete section 11.

[0074] After the double-layer steel mesh 2 is installed, diagonal reinforcing bars 4 are welded between the horizontally and vertically adjacent hollow steel pipes 1. The diagonal reinforcing bars 4 are made of threaded steel bars with a specification of φ10 or above, and are arranged along the diagonal of the steel pipe mesh to form a triangular reinforcement system, thereby improving the shear resistance of the overall structure.

[0075] Finally, sprayed concrete (3) is applied using either dry or wet spraying techniques, spraying in layers from top to bottom, in 2-3 layers to the designed total thickness. This ensures the concrete completely covers the upper reinforcing mesh (22) and the sprayed concrete section (11) of the hollow steel pipe (1), resulting in a smooth surface without exposed reinforcement or hollow areas. After spraying, curing is performed according to specifications for at least 7 days, ultimately forming an integral reinforced structure with internal grouting bonding, double-layer reinforcement, and a sealed surface concrete layer.

[0076] After all construction is completed, systematic quality testing must be carried out according to relevant specifications to verify the construction quality and reinforcement effect of the reinforced structure. Grout fullness testing can be performed using sonic logging, testing the elastic wave velocity changes between the pipe wall and the surrounding rock mass along the axial direction of the hollow steel pipe 1 to determine the grout filling range and density, requiring a grout fullness of over 90%. For critical stress areas, core drilling can be used to directly observe the grout filling in the rock core and test the uniaxial compressive strength of the grout-formed rock mass. The thickness and compressive strength of the shotcrete surface layer 3 need to be tested. Thickness testing is performed using drilling, with no fewer than 3 testing points per 100㎡ of slope, an average thickness not less than the design thickness, and a minimum thickness not less than 80% of the design thickness. Strength testing uses the shotcrete slab cutting method or core drilling method; the compressive strength at 28 days should not be lower than the design strength grade. In addition, on-site pull-out tests of the hollow steel pipe 1 are required; the ultimate pull-out bearing capacity must meet the design safety factor requirements, typically not less than 2.0.

[0077] After the slope reinforcement project is completed, surface displacement monitoring points and deep displacement monitoring holes can be installed to track the slope deformation dynamics over a long period and verify the long-term service performance of the reinforced structure. Engineering application data shows that, compared with traditional anchor bolt shotcrete support, slopes using the integral reinforcement structure of this invention can reduce the horizontal displacement rate during the rainy season by more than 60%, reduce the seepage flow at the rear edge of the slope by more than 70%, and increase the overall anti-sliding safety factor of the slope by 30%-50%. Long-term stability and durability are significantly improved, effectively reducing slope operation and maintenance costs and secondary damage treatment costs.

[0078] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A monolithic reinforcement structure for fractured rock mass slopes, characterized in that, This includes hollow steel pipes, steel mesh, and shotcrete; The hollow steel pipe includes a grouting section and a shotcrete section. The grouting section is embedded inside the fractured rock mass, and the shotcrete section is exposed on the slope of the fractured rock mass. The reinforcing mesh includes a lower reinforcing mesh and an upper reinforcing mesh. The lower reinforcing mesh is fixedly connected to the grouting section and is attached to the fractured rock slope. The upper reinforcing mesh is fixedly connected to the shotcrete section. The upper and lower reinforcing meshes are spaced apart. Grouting holes are provided on the sidewall of the grouting section. The bottom of the grouting section is provided with an outwardly expanding conical structure. The shotcrete covers the upper reinforcing mesh and the shotcrete section and fills the hollow steel pipe.

2. The integral reinforcement structure for fractured rock mass slope according to claim 1, characterized in that, The upper steel mesh is welded and fixed at a position 3-5cm away from the end of the shotcrete section.

3. The integral reinforcement structure for fractured rock mass slope according to claim 1, characterized in that, It also includes diagonal reinforcing bars, which are welded and fixed to the transversely arranged hollow steel pipes and the longitudinally arranged hollow steel pipes, respectively.

4. The integral reinforcement structure for fractured rock mass slope according to claim 3, characterized in that, The diameter of the diagonal reinforcing bars is larger than the diameter of the reinforcing bars in the steel mesh.

5. The integral reinforcement structure for fractured rock mass slope according to claim 4, characterized in that, The lower layer of reinforcing mesh is welded and fixed to the grouting section, and the upper layer of reinforcing mesh is connected to the inclined reinforcing bars by binding.

6. The integral reinforcement structure for fractured rock mass slope according to claim 1, characterized in that, The outer diameter D of the hollow steel pipe satisfies the following design calculation formula: ； In the formula, G is the maximum shear force borne by the hollow steel pipe, t is the ratio of the inner and outer diameters of the hollow steel pipe, and [τ] is the maximum shear strength of the hollow steel pipe.

7. The integral reinforcement structure for fractured rock mass slope according to claim 1, characterized in that, The lower layer of reinforcing mesh is welded to the side of the hollow steel pipe, and the hollow steel pipe of the same lower layer of reinforcing mesh is arranged along both sides of the reinforcing bar.

8. A construction method for an integral reinforcement structure for fractured rock mass slopes, characterized in that, Includes the following steps: S1. Determine the rock mass fracture depth based on the geological survey report, calculate the shear resistance parameters of the hollow steel pipe, and process the hollow steel pipe to form a structure with grouting holes on the side wall and an open conical shape at the bottom; S2. Install the hollow steel pipe on the fractured slope, so that the grouting section of the hollow steel pipe is buried inside the fractured rock mass, and the shotcrete section is exposed on the surface of the fractured slope. S3. High-pressure grouting is performed into the hollow steel pipe. Grouting is stopped after grout continuously emerges from the side wall of the hollow steel pipe. S4. Fix the lower layer of steel mesh to the grouting section and fix the upper layer of steel mesh to the shotcrete section; S5. Spray concrete from top to bottom, so that the concrete covers the upper steel mesh and the sprayed concrete section to form an integral reinforced structure.

9. A construction method for an integral reinforcement structure for fractured rock mass slopes according to claim 8, characterized in that, In step S3, after stopping grouting, let it stand for 3-5 minutes. If there is no sinking of the grout on the side wall of the hollow steel pipe, the grouting operation is considered complete.

10. A construction method for an integral reinforcement structure for fractured rock mass slopes according to claim 8, characterized in that, After step S4 is completed, diagonal reinforcing bars are welded between the horizontally arranged hollow steel pipes and the longitudinally arranged hollow steel pipes.

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