An assembled cantilever reinforced subgrade retaining structure suitable for high and steep rock slope

Abstract

The present application relates to the field of geotechnical engineering such as highway subgrade, and particularly relates to an assembled cantilever reinforced subgrade retaining structure suitable for high and steep rock slope, aiming at solving the technical problems of complex and harsh construction conditions and high bending moment of pile body faced by the retaining structure of high and steep rock slope section. The assembled cantilever reinforced subgrade retaining structure comprises a pile foundation, a retaining board, a joist, a retaining wall and a geogrid. The pile foundation is arranged at intervals along the extension direction of the line, and is a reinforced concrete structure formed by on-site binding and pouring of reinforcement. The retaining board is arranged between adjacent pile foundations, and is used for retaining the backfill soil at the bottom of the subgrade between the rock slope and the pile foundation. The joist is arranged at the top of the pile foundation and is fixedly connected with the pile foundation. The retaining wall is a prefabricated overhanging structure, and is fixedly connected with the joist with the joist as the base. The geogrid is laid between the rock slope and the retaining wall, and forms a reinforced subgrade together with the upper backfill soil of the subgrade, and the two ends of the geogrid are fixedly connected with the retaining wall and the rock slope respectively.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering, such as highway subgrade, and particularly to a prefabricated cantilevered reinforced subgrade retaining structure suitable for steep rock slopes. Background Technology

[0002] As the national highway network extends into rugged mountainous areas, the construction of roadbeds along steep rock slopes has become a significant challenge for the industry. Mountainous areas account for two-thirds of my country's land area, and due to complex topography, many highway routes must traverse areas with steep rock slopes, creating steep cross-slope sections. The roadbed retaining structures for these sections must not only meet the road width requirements but also withstand the lateral pressure from the slope's rock and soil, ensuring driving safety and long-term structural stability.

[0003] In existing technologies, solutions for retaining walls on steep rock slopes mainly fall into two categories: one is to use bridges to cross the terrain, but bridge solutions are expensive, posing a significant cost burden for economically disadvantaged mountainous areas and making large-scale application difficult; the other is to use traditional retaining structures or combined retaining forms, such as prestressed anchor pile slab walls, anti-slide piles combined with platforms and retaining walls, etc. However, traditional single retaining structures are prone to insufficient structural stability due to the retaining height exceeding the standard limits, posing safety hazards for later operation; while existing combined retaining structures mostly adopt on-site casting construction methods, which are complex in construction processes and have stringent requirements for site work space, construction equipment, and environmental conditions. When implemented in steep rock slope areas, they face problems such as high construction difficulty, long construction period, and high safety risks.

[0004] Furthermore, the unique topography of steep rock slopes necessitates that roadbed retaining structures balance road width expansion with structural stress equilibrium. Traditional retaining structures often require increased cantilever height to ensure road width, leading to a significant increase in bending moments on the piles and increasing the risk of structural cracking and deformation, further complicating the design and construction of the retaining structure. Simultaneously, the reliability of connections between components in cast-in-place retaining structures depends heavily on construction techniques, making consistency difficult to guarantee. Moreover, the harsh climate and terrain conditions of mountainous areas make quality control challenging, further reducing the structure's safety margin. Summary of the Invention

[0005] The purpose of this invention is to provide a prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes, aiming to solve the technical problems of complex and harsh construction conditions and high pile height and bending moment faced by retaining structures on steep rock slopes.

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

[0007] This invention provides a prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes, comprising: pile foundations, retaining slabs, supporting beams, retaining walls, and geogrids; the pile foundations are spaced apart along the extension direction of the road, and are reinforced concrete structures formed by on-site binding of steel bars and casting; the retaining slabs are placed between adjacent pile foundations to retain the backfill soil at the bottom of the roadbed between the rock slope and the pile foundations; the supporting beams are placed on top of the pile foundations and are fixedly connected to the pile foundations; the retaining wall is a prefabricated cantilevered structure, with the supporting beams as its base and fixedly connected to the supporting beams; the geogrids are laid between the rock slope and the retaining wall, forming a reinforced roadbed together with the backfill soil above the roadbed, and the two ends of the geogrids are fixedly connected to the retaining wall and the rock slope, respectively.

[0008] A grouting corrugated pipe is pre-embedded at the top of the pile foundation. The top of the grouting corrugated pipe is flush with the top surface of the pile foundation. The bottom of the support beam is provided with reserved splicing longitudinal bars, which are inserted into the grouting corrugated pipe to fix the support beam to the pile foundation.

[0009] The top of the support beam has a groove, and the bottom of the retaining wall has a downward protrusion. The protrusion matches the groove, so that the retaining wall and the support beam are locked together.

[0010] The retaining wall includes an outward-facing sidewall and a base plate. The outward-facing sidewall and the base plate are fixedly connected to form an integrated structure. The outward-facing sidewall is provided with a reserved hook, which is fixedly connected to one end of the geogrid.

[0011] Before the roadbed is filled, the rock slope is pretreated to form a stepped structure. A vertical anchor is buried in the center of the stepped structure, and the anchor is fixedly connected to one end of the geogrid.

[0012] The portion of the rock slope that is higher than the road surface elevation is excavated to form a cut roadbed, and the cut roadbed is connected with the reinforced roadbed to form a complete roadbed structure.

[0013] The retaining plate is a precast reinforced concrete structure, with its two sides aligned with the center line of the corresponding pile foundation.

[0014] Geogrids are laid layer by layer along the gap between the rock slope and the retaining wall to form a continuous reinforced protective structure.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. This application provides a prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes. In this invention, the retaining plate, supporting beam, and retaining wall are all prefabricated in a factory; only the pile foundation requires on-site reinforcement binding and pouring, significantly reducing the amount of on-site work required for steep rock slopes. After the prefabricated components are transported to the site, they can be quickly installed using standardized assembly methods, eliminating the need for complex on-site construction processes. This effectively reduces reliance on narrow working spaces, harsh terrain, and climatic conditions in mountainous areas, solving the problem of complex and demanding construction of traditional on-site cast-in-place structures. Simultaneously, prefabricated construction reduces time-consuming processes such as on-site concrete curing and formwork erection, significantly shortening the construction cycle, improving project construction efficiency, and reducing safety risks in mountainous construction. On the one hand, the retaining wall adopts an outward-cantilever design, combined with the excavation treatment of the rock slope above the road surface elevation. While ensuring the road width requirement, it significantly shortens the height of the cantilever section of the retaining structure, reducing the root cause of pile bending moment from a structural design perspective. On the other hand, the reinforced subgrade formed by the geogrid and the backfill soil on the upper part of the subgrade effectively improves the stability of the soil itself, significantly weakens the horizontal earth pressure on the outward-cantilever sidewall of the retaining wall, and indirectly reduces the lateral force borne by the pile body. In addition, the bottom plate of the retaining wall penetrates into the soil to play a load-bearing role, further reducing the lateral earth pressure on the retaining plate between adjacent pile foundations, achieving multiple reductions in pile bending moment. This fundamentally solves the technical problem of high pile bending moment in traditional retaining structures and improves the safety and reliability of the structure in long-term service.

[0017] 2. This invention ensures the connection stability of the prefabricated structure through multiple optimized designs: the support beam and the pile foundation are fixedly connected by inserting pre-reserved spliced ​​longitudinal reinforcement into pre-embedded grouting corrugated pipes, resulting in a tight connection and strong load-bearing capacity after grouting; the groove at the top of the support beam and the matching snap-fit ​​of the protrusion at the bottom of the retaining wall achieve precise positioning and stable connection between the two, avoiding displacement deviation during assembly; the two ends of the geogrid are fixed to the pre-reserved hooks of the retaining wall and the pre-embedded anchors of the rock slope, and are laid continuously layer by layer to form a complete reinforcement system, making the reinforced roadbed, slope, and retaining wall form a coordinated whole for stress distribution. The reliable connection and coordinated work of each component significantly improve the overall rigidity and stability of the retaining structure, effectively resisting the lateral thrust and deformation of the soil and rock mass on steep rock slopes.

[0018] 3. Compared to bridge crossing solutions, this invention, through the combination of roadbed support and prefabricated design, significantly reduces material consumption and construction costs while meeting road width and structural safety requirements. It is particularly suitable for mountainous highway construction in economically disadvantaged areas. Simultaneously, the standardized production of prefabricated components reduces on-site labor and equipment input, and the shortened construction cycle further reduces project duration and management costs. Furthermore, the improved structural stability and reduced pile bending moment lower the frequency and cost of later maintenance and repairs, optimizing the overall project cost from a life-cycle perspective. This invention possesses significant economic applicability and promotional value. Attached Figure Description

[0019] Figure 1 This is a cross-sectional schematic diagram of a prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes, provided in an embodiment of this application.

[0020] Figure 2 This is a schematic diagram showing the connection of each component of a prefabricated cantilevered reinforced roadbed retaining structure provided in an embodiment of this application;

[0021] Figure 3 This is a three-dimensional schematic diagram of a prefabricated cantilevered reinforced roadbed retaining structure provided in an embodiment of this application;

[0022] Figure 4 This is a comparison diagram of numerical models provided in an embodiment of this application;

[0023] Figure 5 This is a schematic diagram comparing numerical calculation results provided in an embodiment of this application.

[0024] The attached diagram is labeled as follows: 10 is pile foundation, 11 is grouting corrugated pipe, 20 is retaining plate, 30 is supporting beam, 31 is spliced ​​longitudinal reinforcement, 32 is groove, 40 is retaining wall, 41 is cantilevered side wall, 42 is bottom plate, 43 is reserved hook, 44 is protrusion, 50 is earth and wood grid, 60 is rock slope, 70 is backfill soil at the bottom of the roadbed, 80 is reinforced roadbed, 90 is anchor bolt, and 100 is excavated roadbed. Detailed Implementation

[0025] The technical solutions of 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] For example, such as Figure 1As shown in the embodiment of this application, a prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes is provided, including: pile foundations 10, retaining plates 20, supporting beams 30, retaining walls 40, and geogrids 50. The pile foundations 10 are spaced apart along the extension direction of the road, and are reinforced concrete structures formed by on-site binding of reinforcing bars; the retaining plates 20 are placed between adjacent pile foundations 10 to support the backfill soil 70 at the bottom of the roadbed between the rock slope 60 and the pile foundations 10; the supporting beams 30 are placed on top of the pile foundations 10 and are fixedly connected to them; the retaining wall 40 is a prefabricated cantilevered structure, with the supporting beams 30 as its base and fixedly connected to them; the geogrids 50 are laid between the rock slope 60 and the retaining wall 40, forming a reinforced roadbed 80 together with the backfill soil above the roadbed, and both ends of the geogrids 50 are fixedly connected to the retaining wall 40 and the rock slope 60, respectively.

[0027] See Figure 1 and Figure 2 The pile foundation 10 is made of reinforced concrete of not less than C35. The pile spacing should be reasonably determined according to the stress of the upper supporting beam. The pile length and cross-sectional dimensions are determined by calculation based on the axial force, bending moment and shear force transmitted from the upper structure to the pile top.

[0028] The pile foundation 10 is a reinforced concrete component formed by on-site steel reinforcement binding and concrete pouring. It serves as the load-bearing foundation of the entire retaining structure, bearing the load transmitted by the upper support beam 30 and retaining wall 40, and stably transferring it to the deep underground soil and rock mass, preventing overall structural slippage or overturning. The pile foundation 10 is formed on-site to ensure a stable connection with the foundation, and by being spaced along the extension direction of the highway, it minimizes disturbance to the original soil and rock mass of the slope while ensuring load-bearing efficiency.

[0029] For example, refer to Figure 1 and Figure 3 The retaining plate 20 is a precast reinforced concrete structure, integrally precast using reinforced concrete of grade no lower than C30, and its cross-sectional dimensions should meet the structural strength requirements. The two edges of the retaining plate 20 are aligned with the center lines of the corresponding pile foundations 10 to ensure installation accuracy and stress balance. During the construction of steep slope roadbeds, backfilling and leveling are required. The function of the retaining plate 20 is to prevent lateral collapse of the bottom backfill soil, while also providing a safe working space for the construction of the superstructure and preventing bottom soil instability from affecting the overall structure.

[0030] The support beam 30 serves as a connecting component between the pile foundation 10 and the retaining wall 40. On the one hand, it evenly distributes the load of the retaining wall 40 to the pile foundation 10 below, avoiding excessive local stress on the pile foundation 10. On the other hand, it provides a flat and stable installation base for the retaining wall 40, ensuring the assembly accuracy of the retaining wall 40.

[0031] For example, refer toFigure 1 , Figure 2 and Figure 3 The retaining wall 40 includes an outwardly projecting sidewall 41 and a base plate 42. The outwardly projecting sidewall 41 and the base plate 42 are fixedly connected to form an integrated structure. A pre-installed hook 43 is provided on the outwardly projecting sidewall 41, and the pre-installed hook 43 is fixedly connected to one end of the geogrid 50. The retaining wall 40 is a precast structure, integrally precast using prestressed concrete of grade not lower than C50, and its cross-sectional dimensions should meet the structural strength requirements. The height of the retaining wall 40, the slope of the sidewall 41, and the length of the base plate 42 should be calculated and determined in conjunction with the load conditions of the roadbed to ensure that they meet the structural stability requirements and the requirements of the substructure. The retaining wall 40 directly resists the lateral thrust of the upper backfill soil and the slope soil and rock mass, and is the main retaining carrier of the retaining structure. Its outwardly projecting design allows for the expansion of the road width without increasing the height of the cantilever section, while simultaneously reducing the bending moment of the pile body from the source.

[0032] In some embodiments, a ring of corrugated grouting pipes 11 is pre-embedded at the top of the pile foundation 10. For example, the pre-length of the corrugated grouting pipes 11 is 900mm, and the top of the corrugated grouting pipes 11 is flush with the top surface of the pile foundation 10. A support beam 30 is disposed between the pile foundation 10 and the retaining wall 40, and is prefabricated with reinforced concrete of not less than C35 grade. The top of the support beam 30 has a groove 32 with a depth of 250mm, and the bottom of the retaining wall 40 has a downward protrusion 44 that matches the groove 32, so that the retaining wall 40 and the support beam 30 are snapped together and fixed. The bottom of the support beam 30 has a reserved splicing longitudinal bar 31, which is inserted into the corrugated grouting pipes 11 to fix the support beam 30 to the pile foundation 10.

[0033] For example, the length of the reserved splicing longitudinal reinforcement 31 is consistent with the length of the pre-embedded grouting corrugated pipe 11. When connecting, ultra-high performance concrete should be poured into the grouting corrugated pipe 11 first. The ultra-high performance concrete used is concrete with a compressive strength greater than or equal to 120MPa, a tensile strength greater than 5MPa, an expansion range of 730mm to 770mm, good fluidity, and self-compacting properties. Then, the extended section of the reserved splicing longitudinal reinforcement 31 is inserted into the grouting corrugated pipe 11 to achieve a fixed connection between the support beam 30 and the pile foundation 10.

[0034] The combination of grouting corrugated pipe 11 and pre-reserved splicing longitudinal reinforcement 31 is adopted. After the splicing longitudinal reinforcement 31 is inserted into the pre-embedded pipe, it can form a tightly integrated whole through grouting. The connection strength is high and the bearing capacity is strong. It can effectively transfer the vertical pressure and lateral force between the support beam 30 and the pile foundation 10, and avoid loosening or displacement of the connection. At the same time, the precise matching and snapping of the groove 32 of the support beam 30 and the protrusion 44 of the retaining wall 40 not only realizes the rapid positioning of the two, but also forms a secondary fixed constraint, which greatly improves the integrity of the connection of the prefabricated components, prevents the retaining wall 40 from shifting under the action of lateral earth pressure, and ensures that the load is smoothly transferred from the retaining wall 40, support beam 30 and pile foundation 10 layers, laying the foundation for the overall stability of the structure.

[0035] The support beam 30 is evenly connected to the pile foundation 10 at multiple points through the bottom longitudinal reinforcement, which can distribute the concentrated load transmitted by the retaining wall 40 to the entire pile foundation 10, avoiding structural damage caused by excessive local stress at the top of the pile foundation 10. The interlocking design of the retaining wall 40 and the support beam 30 ensures full fit between the two contact surfaces, so that the lateral earth pressure is evenly distributed on the support beam, reducing local stress concentration, indirectly reducing the unbalanced bending moment borne by the pile body, and further improving the safety and durability of the structure in long-term service.

[0036] For example, refer to Figure 1 The geogrid 50 is laid layer by layer along the gap between the rock slope 60 and the retaining wall 40 to form a continuous reinforced protective structure. More specifically, the geogrid 50 is laid layer by layer between the rock slope 60 and the cantilevered sidewall 40 of the retaining wall to form a reinforced roadbed 80. The two sides of the laid geogrid 50 are connected to the hooks 43 reserved on the cantilevered sidewall 41 of the retaining wall 40 and the anchors 90 buried on the rock slope 60, respectively.

[0037] As one possible implementation, the rock slope 60 is pretreated to form a stepped structure before the roadbed filling. A vertical anchor 90 is embedded in the center of the stepped structure, and the anchor 90 is fixedly connected to one end of the geogrid 50. The geogrid 50 itself has high strength and tensile strength, which can enhance the integrity and shear strength of the backfill soil, reduce the lateral deformation of the soil, and thus reduce the horizontal earth pressure on the retaining wall 40 (indirectly reducing the bending moment of the pile). At the same time, it allows the backfill soil, slope, and retaining wall 40 to form a synergistic force-bearing whole, improving the overall stability of the structure.

[0038] For example, the portion of the rock slope 60 above the road surface elevation is excavated to form a cut roadbed 100, which is then connected to the reinforced roadbed 80 to form a complete roadbed structure. If the portion of the rock slope above the road surface elevation is not treated, to ensure the road width, the cantilever section of the retaining wall 40 needs to be significantly raised, leading to a sharp increase in the bending moment borne by the piles. However, by excavating to form the cut roadbed 100, the original rock and soil mass of the slope is essentially used as part of the roadbed. This eliminates the need to widen the road surface by extending the cantilever of the retaining wall 40, directly shortening the height of the cantilever section of the retaining structure and reducing the foundation for pile bending moments from the structural design stage. Simultaneously, the cut roadbed 100, composed of original rock and soil mass, has strong inherent stability and does not generate significant lateral pressure like backfill soil, indirectly reducing the lateral forces borne by the retaining wall 40 and pile foundation 10, further reducing pile bending moments. This, combined with the effect of geogrid reinforcement, more thoroughly resolves the contradiction between wide road surfaces and high bending moments in traditional structures.

[0039] Reference Figure 4 and Figure 5 To verify the practicality of the structure provided in this application's embodiments, a typical working condition was simulated: a rock slope divided into two sections from top to bottom (upper section slope angle 60°, lower section slope angle 45°), pile spacing 6m, reinforced roadbed top width 10m (excluding the width of the excavated roadbed section), retaining wall height 4m, and retaining wall sidewall overhang 30°. Simplified finite difference numerical models were constructed for the cantilevered reinforced roadbed retaining structure (retaining wall height 4.5m, base height 0.5m, pile length 14m, including a 5m cantilever section) provided in this application's embodiments and the traditional pile-slab wall retaining structure (pile length 19m, including a 13.25m cantilever section) under this working condition. Comparative results show that the prefabricated cantilevered reinforced roadbed retaining structure proposed in this application's embodiments reduces the cantilever section length of the pile foundation by 62.3% and the roadbed backfill volume by 27.6%. Furthermore, a comparison of the simulation results for lateral earth pressure and pile bending moment between the two methods shows that the prefabricated cantilevered reinforced roadbed retaining structure proposed in this application can reduce the maximum lateral earth pressure by 60.7% and the maximum pile bending moment by 29.1%. Based on this, as the slope of the rock slope is gradually increased, the reduction in maximum lateral earth pressure and the maximum pile bending moment also gradually increase. This indicates that under steeper slope conditions, the technical advantages and economic efficiency of the prefabricated cantilevered reinforced roadbed retaining structure proposed in this application become increasingly prominent.

[0040] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0041] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes, characterized in that, include: The structure comprises pile foundations (10), retaining walls (20), supporting beams (30), retaining walls (40), and geogrids (50). The pile foundations (10) are spaced apart along the direction of the road extension, and are reinforced concrete structures formed by on-site binding of steel bars and casting. The retaining walls (20) are located between adjacent pile foundations (10) to support the backfill soil (70) at the bottom of the roadbed between the rock slope (60) and the pile foundations (10). The supporting beams (30) are located between the pile foundations (10). The top of the retaining wall (40) is fixedly connected to the pile foundation (10); the retaining wall (40) is a prefabricated cantilever structure, with the support beam (30) as the base and fixedly connected to the support beam (30); the geogrid (50) is laid between the rock slope (60) and the retaining wall (40), and together with the backfill soil above the roadbed, it forms a reinforced roadbed (80). The two ends of the geogrid (50) are fixedly connected to the retaining wall (40) and the rock slope (60) respectively.

2. The prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes according to claim 1, characterized in that, The top of the pile foundation (10) is pre-embedded with a grouting corrugated pipe (11), the top of the grouting corrugated pipe (11) is flush with the top surface of the pile foundation (10), and the bottom of the support beam (30) is provided with a reserved splicing longitudinal bar (31). The reserved splicing longitudinal bar (31) is inserted into the grouting corrugated pipe (11) so that the support beam (30) is fixedly connected to the pile foundation (10).

3. A prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes according to claim 2, characterized in that, The top of the support beam (30) has a groove (32) and the bottom of the retaining wall (40) has a downward protrusion (44). The protrusion (44) is adapted to the groove (32) so that the retaining wall (40) and the support beam (30) are locked together.

4. A prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes according to claim 1, characterized in that, The retaining wall (40) includes an outwardly projecting sidewall (41) and a base plate (42). The outwardly projecting sidewall (41) and the base plate (42) are fixedly connected to form an integrated structure. The outwardly projecting sidewall (41) is provided with a reserved hook (43), which is fixedly connected to one end of the geogrid (50).

5. A prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes according to claim 1, characterized in that, The rock slope (60) is pretreated to form a stepped structure before the roadbed is filled. A vertical anchor (90) is buried in the center of the stepped structure. The anchor (90) is fixedly connected to one end of the geogrid (50).

6. A prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes according to claim 5, characterized in that, The portion of the rock slope (60) above the road surface elevation is excavated to form a cut roadbed (100), and the cut roadbed (100) is connected with the reinforced roadbed (80) to form a complete roadbed structure.

7. A prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes according to claim 1, characterized in that, The retaining plate (20) is a precast reinforced concrete structure, and the two sides of the retaining plate (20) are respectively aligned with the center line of the pile foundation (10) on the corresponding side.

8. A prefabricated cantilevered reinforced roadbed retaining structure suitable for steep rock slopes according to claim 1, characterized in that, The geogrid (50) is laid layer by layer along the gap between the rock slope (60) and the retaining wall (40) to form a continuous reinforced protective structure.

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