Steel floral tube grouting reinforcement treatment method for highway excavation weak interlayer side slope

Abstract

The invention provides a highway excavation weak interlayer side slope steel floral tube grouting reinforcement treatment method, belongs to the technical field of road engineering, and aims to solve the problems that a highway excavation side slope containing a weak interlayer is prone to slipping and instability along the interlayer, and a traditional reinforcement method is long in construction period, insufficient in anchoring force, large in side slope disturbance and the like. According to the method, a vertical and oblique combined three-dimensional cooperative reinforcement system is constructed, through slope investigation and positioning, steel floral tube drilling, grouting amount and pressure double-control segmented grouting and later maintenance, a three-dimensional composite reinforcement body is formed on the weak intercalated layer and a potential slip crack surface, and the weak intercalated layer is segmented, wrapped and cemented. The method is high in pertinence, convenient to construct and reliable in quality, the anti-sliding capacity and long-term stability of the slope can be effectively improved, and the problem that a traditional reinforcing mode and a slope instability mode are poor in adaptability is solved.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, specifically to a method for reinforcing weak interlayer slopes in highway excavation using steel pipe grouting. Background Technology

[0002] In highway construction in mountainous or hilly areas, weak interlayers (such as weak clay layers and fractured rock layers) are often present in excavated slopes. These interlayers have low strength and are easily softened when exposed to water, which is a core cause of slope instability. Traditional reinforcement methods have obvious drawbacks: anti-slide piles and gravity retaining walls have long construction cycles and high costs, and cause significant disturbance to the original soil on the slope; when grid anchoring (full-length bonded anchor grid and prestressed cable grid) is used for loose and weak interlayers, it is difficult to establish effective anchoring force in a timely manner—the stress is released quickly after the loose deposits are excavated, and full-length bonded anchors cannot quickly provide anchoring support during slope deformation. The slope anchoring end of the prestressed cable is prone to deformation under concentrated stress, resulting in prestress relaxation and a significant loss of anchoring force.

[0003] Although steel pipe grouting technology has been applied to foundation reinforcement, it is often simply used as a soil improvement method in the treatment of weak interlayers in slopes. There is a lack of pipe layout schemes and grouting control strategies that match the instability mode of slope sliding along the weak interlayer. As a result, problems such as ambiguous grouting parameters and arbitrary pipe layout often occur, which cannot effectively suppress the sliding deformation of the slope along the weak interlayer and make it difficult to ensure the long-term stability of the slope. Therefore, a reinforcement method that is targeted, easy to construct and can fundamentally improve the shear strength of the weak interlayer is proposed. Summary of the Invention

[0004] The present invention aims to solve the problems mentioned in the background art and provides a method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes.

[0005] The specific technical solution is as follows: A method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipe grouting includes the following steps: Step 1: Slope Investigation and Hole Location: Based on the geological survey report and the slope excavation surface, identify the location and attitude of the weak interlayers, and determine the reinforcement area based on the analysis of potential slip surfaces; arrange grouting holes in a quincunx pattern on the slope platform and slope surface, with a hole spacing of 2.0m to 3.0m, and use measuring instruments to accurately lay out and mark the hole positions; Step 2, Steel Pipe Fabrication and Drilling: Fabricate steel pipes that meet the requirements, use a drilling rig to drill holes to the designed depth, and adapt the drilling direction to the potential slip surface to ensure that the weak interlayer is penetrated and the stable layer is penetrated to a depth of not less than 1.0m. After cleaning the hole, install the steel pipe to the designed depth in the hole. Step 3, Grout Preparation and Pressure Grouting: Prepare grout with a specific ratio, adopt a segmented grouting process, focus on covering the weak interlayer in the grouting area, implement the principle of dual control of grouting volume and grouting pressure, and follow the principle of skipping holes from the outer perimeter to the inner perimeter and from the lower row to the upper row in the grouting sequence. Step 4: Grouting completion and post-treatment: Grouting is terminated when one of the grouting control standards is met. The grouting equipment is cleaned, the exposed steel pipe ends are treated, and the grouting area is cured for no less than 7 days. Subsequent operations are carried out after the grout strength reaches the standard. In step two, the steel pipes deployed form a three-dimensional collaborative reinforcement system. This system includes vertical reinforcement units and inclined reinforcement units. The vertical reinforcement unit consists of at least one row of steel pipes vertically deployed on the slope platform. The steel pipes penetrate the weak interlayer and extend into the stable soil layer below it. The ratio of the anchorage lengths in the soil and rock mass above and below the weak interlayer is 0.8 to 1.2. The inclined reinforcement unit consists of at least one row of steel pipes inclined at the toe of the slope at an angle of 5° to 15°. The angle is perpendicular to the potential sliding surface, and the steel pipes are deployed behind the potential slip surface. The steel pipes penetrate the weak interlayer and extend into the stable layer for a depth of not less than 2.0m. The vertical reinforcement units and the inclined reinforcement units are arranged intersectingly in space to form a three-dimensional composite reinforcement body in the weak interlayer and along the path of the potential slip surface.

[0006] As a preferred embodiment of the present invention, the steel pipes of the vertical reinforcement unit are arranged in two rows, and the two rows of steel pipes are arranged in parallel on the slope platform with a row spacing of 1.5m to 2.5m.

[0007] As a preferred embodiment of the present invention, the ratio of the anchorage length of the steel pipe of the vertical reinforcement unit in the soft interlayer soil and rock mass above and below is 1.0.

[0008] As a preferred embodiment of the present invention, the steel pipes of the inclined reinforcement unit are arranged in two rows, and the two rows of steel pipes are staggered at the toe of the slope, with a row spacing of 1.8m to 2.2m.

[0009] As a preferred embodiment of the present invention, the steel pipe is made of steel pipe with an outer diameter ≥89mm and a wall thickness ≥5mm. Holes are drilled in the pipe section within the depth range corresponding to the weak interlayer. The holes are arranged in a plum blossom shape, with a diameter of 8-10mm and a spacing of 300-500mm. The grouting section is wrapped with a protective layer, and a conical pile tip is welded to the bottom of the pipe.

[0010] As a preferred embodiment of the present invention, the slurry is a pure cement slurry with a water-cement ratio of 0.4:1 to 0.6:1, or a pure cement slurry with an admixture added, wherein the admixture is one or more of a water-reducing agent, an early-strength agent, or an expansion agent.

[0011] As a preferred embodiment of the present invention, in the dual-control principle, the grouting amount per meter of steel pipe is 75kg to 100kg of cement, the grouting pressure reaches and stabilizes at ≥1.0MPa, and the duration is 5 to 10 minutes.

[0012] As a preferred embodiment of the present invention, the diameter of the borehole is 20-30 mm larger than the outer diameter of the steel pipe, and mud slurry wall protection or dry drilling method is used during the drilling process to prevent the borehole wall from collapsing.

[0013] As a preferred embodiment of the present invention, the curing environment temperature of the grouting area is not lower than 5°C, and disturbance to the slope is avoided during the curing period.

[0014] As a preferred embodiment of the present invention, the three-dimensional composite reinforcement body is composed of cement grout veins and steel pipe skeleton, which divides, wraps and binds the weak interlayer, thereby increasing the shear strength of the weak interlayer by more than 30%.

[0015] The present invention has the following beneficial effects: 1. Targeted solutions to instability issues to improve slope anti-slide capacity. The three-dimensional collaborative reinforcement system precisely matches the instability mode of slope sliding along the weak interlayer: the vertical reinforcement unit bears the lateral earth pressure and restricts the displacement of the soil above and below the interlayer, while the inclined reinforcement unit anchors the slope and compacts the interlayer. The three-dimensional composite reinforcement body formed by the two directly blocks the sliding path and cements the loose soil of the weak interlayer, fundamentally improving the mechanical properties of the interlayer and greatly reducing the risk of slope sliding along the weak interlayer. 2. Ensure reinforcement quality and avoid potential construction hazards. The plum blossom-shaped hole positioning ensures that there are no blind spots in the reinforcement. The segmented dual-control grouting avoids reinforcement failure caused by insufficient grouting and prevents slope disturbance caused by excessive pressure. The structural design of the steel flower pipe ensures that the grout is accurately injected into the interlayer. Multi-link coordinated control makes the reinforced body dense, uniform, and has stable and reliable strength, solving the problem of unstable quality in traditional reinforcement. 3. Convenient construction, reducing disturbance to slopes. Compared with large structures such as anti-slide piles and gravity retaining walls, steel pipe grouting construction is flexible and fast, does not require large-scale excavation, and causes little disturbance to the original soil on the slope. The standardized construction process (from hole location to post-maintenance) reduces the complexity of construction organization, facilitates on-site operation, and reduces construction period and cost input, taking into account both economy and practicality. 4. Achieve long-term slope stability The three-dimensional composite reinforcement formed after grouting combines the weak interlayer with the surrounding stable soil into a whole, which can effectively inhibit the gradual failure of the slope. With proper post-construction maintenance, the strength of the reinforcement can be maintained stably, ensuring the slope's ability to resist external disturbances (such as rainwater soaking and temperature changes) during long-term service, and avoiding the problem of short-term reinforcement failure. Attached Figure Description

[0016] Figure 1 A flowchart of a method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes, provided in an embodiment of the present invention; Figure 2 This is a construction diagram illustrating the method for reinforcing weak interlayer slopes in highway excavation using steel pipe grouting, as provided in an embodiment of the present invention. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual images. They should not be construed as limiting the scope of this application. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0019] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" or similar designation indicating a connection between components should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example

[0021] The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes, as provided in this embodiment, is as follows: Figure 1 As shown, it includes the following steps: Step 1: Slope Investigation and Hole Location: Based on the geological survey report and the slope excavation surface, identify the location and attitude of the weak interlayers, and determine the reinforcement area based on the analysis of potential slip surfaces; arrange grouting holes in a quincunx pattern on the slope platform and slope surface, with a hole spacing of 2.0m to 3.0m, and use measuring instruments to accurately lay out and mark the hole positions; Step 2, Steel Pipe Fabrication and Drilling: Fabricate steel pipes that meet the requirements, use a drilling rig to drill holes to the designed depth, and adapt the drilling direction to the potential slip surface to ensure that the weak interlayer is penetrated and the stable layer is penetrated to a depth of not less than 1.0m. After cleaning the hole, install the steel pipe to the designed depth in the hole. Step 3, Grout Preparation and Pressure Grouting: Prepare grout with a specific ratio, adopt a segmented grouting process, focus on covering the weak interlayer in the grouting area, implement the principle of dual control of grouting volume and grouting pressure, and follow the principle of skipping holes from the outer perimeter to the inner perimeter and from the lower row to the upper row in the grouting sequence. Step 4: Grouting completion and post-treatment: Grouting is terminated when one of the grouting control standards is met. The grouting equipment is cleaned, the exposed steel pipe ends are treated, and the grouting area is cured for no less than 7 days. Subsequent operations are carried out after the grout strength reaches the standard. In step two, the steel pipes deployed form a three-dimensional collaborative reinforcement system. This system includes vertical reinforcement units and inclined reinforcement units. The vertical reinforcement unit consists of at least one row of steel pipes vertically deployed on the slope platform. The steel pipes penetrate the weak interlayer and extend into the stable soil layer below it. The ratio of the anchorage lengths in the soil and rock mass above and below the weak interlayer is 0.8 to 1.2. The inclined reinforcement unit consists of at least one row of steel pipes inclined at the toe of the slope at an angle of 5° to 15°. The angle is perpendicular to the potential sliding surface, and the steel pipes are deployed behind the potential slip surface. The steel pipes penetrate the weak interlayer and extend into the stable layer for a depth of not less than 2.0m. The vertical reinforcement units and the inclined reinforcement units are arranged intersectingly in space to form a three-dimensional composite reinforcement body in the weak interlayer and along the path of the potential slip surface.

[0022] This solution constructs a three-dimensional, synergistic reinforcement system combining vertical and oblique elements. Vertical reinforcement units penetrate the weak interlayer and control the ratio of upper and lower anchorage lengths, acting like "miniature anti-slide piles" to bear lateral earth pressure and provide shear resistance. Oblique reinforcement units, angled at specific inclinations towards the potential slip surface, achieve "soil nailing" anchorage and directional compaction of the weak interlayer. The three-dimensional composite reinforcement body formed by the spatial intersection of these two elements comprehensively covers the weak interlayer and the path of the potential slip surface, segmenting, encapsulating, and cementing the weak interlayer, fundamentally improving its stress state. Simultaneously, the quincunx-shaped borehole positioning ensures precise alignment of the reinforcement area with risk points, segmented dual-control grouting avoids insufficient grouting or excessive pressure that could disturb the slope, and subsequent curing ensures stable strength formation of the reinforcement body. Ultimately, this comprehensively improves the slope's anti-slide capacity and long-term stability, solving the problem of traditional reinforcement methods failing to match slope instability patterns.

[0023] Specifically, in this embodiment, the steel pipes of the vertical reinforcement unit are arranged in two rows, parallel to each other on the slope platform, with a row spacing of 1.5m to 2.5m. This scheme, by arranging the vertical reinforcement units in two parallel rows, expands the vertical reinforcement coverage compared to a single row arrangement, allowing for more uniform constraint of the vertical steel pipes on the weak interlayer below the slope platform and reducing localized stress concentration. The synergistic support formed by the two rows of steel pipes further enhances the slope's resistance to lateral earth pressure, reduces the risk of localized slippage along the weak interlayer, and strengthens the overall anti-slip support effect of the vertical reinforcement unit on the slope.

[0024] Specifically, in this embodiment, the ratio of the anchorage lengths of the steel pipes of the vertical reinforcement unit in the soil and rock mass above and below the weak interlayer is 1.0. This scheme sets the anchorage lengths of the vertical steel pipes in the soil and rock mass above and below the weak interlayer to be equal, which allows the anchorage force of the steel pipes on both sides of the weak interlayer to be more balanced, avoiding the problem of force concentration due to excessively short anchorage on one side and material waste due to excessively long anchorage on the other side; the balanced anchorage force can make the torsional and shear resistance of the vertical reinforcement unit more stable, reduce the possibility of local anchorage failure, and further ensure the anti-sliding restraint effect of the slope in the vertical direction.

[0025] Specifically, in this embodiment, the steel pipes of the inclined reinforcement unit are arranged in two rows, which are staggered at the toe of the slope, with a row spacing of 1.8m to 2.2m. Compared with parallel arrangement, this scheme arranges the inclined reinforcement unit in two staggered rows, which allows for denser anchoring points of the inclined steel pipes in the toe area of ​​the slope and can cover more potential slip surface paths. The staggered distribution of steel pipes can form a more comprehensive directional compaction effect on the weak interlayer, reducing reinforcement blind spots. At the same time, the synergistic anchoring formed by the two rows of steel pipes can further enhance the rigid support of the weak interlayer at the toe, improve the anti-slip bearing capacity of the toe area, and prevent the slope from sliding along the weak interlayer from the toe.

[0026] Specifically, in this embodiment, the steel perforated pipe uses steel pipes with an outer diameter ≥89mm and a wall thickness ≥5mm. Holes are drilled in a staggered pattern on the pipe sections within the corresponding weak interlayer depth range. The holes are arranged in a quincunx pattern, with a diameter of 8-10mm and a spacing of 300-500mm. A protective layer is wrapped around the outside of the grouting section, and a conical pile tip is welded to the bottom of the pipe. This scheme uses steel pipes of specific specifications to manufacture the steel perforated pipe, ensuring that the steel perforated pipe itself has sufficient strength to serve as a reinforcing skeleton to bear the load. Drilling quincunx-shaped holes in the pipe sections corresponding to the weak interlayer depth allows for precise injection of grout into the weak interlayer area, avoiding waste of grout in non-critical areas. The protective layer wrapped around the outside of the grouting section prevents the holes from being blocked by soil, ensuring smooth grout flow. The conical pile tip at the bottom of the pipe facilitates precise insertion of the steel perforated pipe into the drilled hole. The overall steel perforated pipe structure design ensures effective grout penetration into the weak interlayer and stable force transmission through the steel pipe skeleton, providing a reliable foundation for the formation of a three-dimensional composite reinforced body.

[0027] Specifically, in this embodiment, the grout is a pure cement grout with a water-cement ratio of 0.4:1 to 0.6:1, or a pure cement grout with admixtures, which may be one or more of a water-reducing agent, an early-strength agent, or an expansive agent. This scheme uses pure cement grout or cement grout with admixtures. Pure cement grout itself has good bonding ability, which can bind loose soil in weak interlayers into a whole. Adding a water-reducing agent can improve the fluidity of the grout, ensuring smooth flow of the grout in the perforated holes of the steel pipe and fully filling the voids in the weak interlayer. Adding an early-strength agent can accelerate the hardening speed of the grout, shorten the curing period, and form reinforcement strength as early as possible. Adding an expansive agent can reduce shrinkage cracks after the grout hardens, enhancing the tightness of the bond between the grout and the soil. Regardless of the grout configuration, it can be adapted to different geological conditions, ensuring effective bonding between the grout and the weak interlayer and improving the reinforcement effect.

[0028] Specifically, in this embodiment, the dual-control principle involves grouting 75kg to 100kg of cement per meter of steel pipe, with the grouting pressure reaching and stabilizing at ≥1.0MPa for 5 to 10 minutes. This scheme achieves dual control of grouting volume and pressure. Volume control ensures that the grout is sufficient to fill the voids in the weak interlayer and compact the loose soil, preventing incomplete reinforcement due to insufficient grouting. Stable grouting pressure control ensures that the grout effectively penetrates to the deeper layers of the weak interlayer while preventing excessive pressure from disturbing the slope soil and causing new deformations. The combination of these two methods allows the grout to be evenly distributed in the weak interlayer, forming complete and dense grout veins, ensuring the integrity and strength of the reinforced body, and avoiding the unstable reinforcement quality problems caused by traditional single-control methods.

[0029] Specifically, in this embodiment, the borehole diameter is 20-30mm larger than the outer diameter of the steel pipe. During drilling, mud slurry or dry drilling is used to prevent borehole wall collapse. This scheme sets the borehole diameter to be larger than the outer diameter of the steel pipe, reserving sufficient space for pipe installation and avoiding difficulties in inserting the pipe or disturbance of the borehole wall during insertion due to an excessively small borehole diameter. Using mud slurry or dry drilling prevents borehole wall collapse and blockage, ensuring that the borehole formation quality and depth meet design requirements. Guaranteed drilling quality allows for precise installation of the steel pipe to the designed depth, ensuring it penetrates weak interlayers and reaches stable layers, providing a foundation for subsequent grouting and reinforcement unit operation.

[0030] Specifically, in this embodiment, the curing environment temperature in the grouting area is not lower than 5℃, and disturbing operations on the slope are avoided during the curing period. This scheme controls the curing environment temperature and avoids disturbance during the curing period. A suitable temperature ensures normal hydration and hardening of the grout, preventing slow hardening or insufficient strength due to excessively low temperatures. Avoiding disturbance during the curing period prevents cracking and displacement of the incompletely hardened reinforcement due to external forces, ensuring that the reinforcement can develop strength according to the design shape. Good curing conditions allow the reinforcement to fully develop its strength, ensuring the stability and long-term effectiveness of the reinforcement, and avoiding a decline in reinforcement quality due to improper curing.

[0031] Specifically, in this embodiment, the three-dimensional composite reinforcement body is composed of cement grout veins and a steel pipe skeleton, which divides, wraps and binds the weak interlayer, thereby increasing the shear strength of the weak interlayer by more than 30%.

[0032] In this scheme, the three-dimensional composite reinforcement body is composed of cement grout veins and a steel pipe skeleton. The steel pipe skeleton provides rigid support for the reinforcement body and can resist the tensile and shear forces generated by slope deformation. The cement grout veins can cement the loose soil in the weak interlayer and connect the weak interlayer with the surrounding stable rock and soil as a whole. The synergistic effect of the two in dividing, wrapping and cementing the weak interlayer can fundamentally improve the mechanical properties of the weak interlayer, enhance its shear resistance, and prevent the weak interlayer from becoming a weak link in slope instability, thereby ensuring the long-term stability of the overall slope.

[0033] Example: Project Background: A section of an excavated slope on a mountainous expressway, from K12+350 to K12+480, has a height of 22m. After excavation, a weak interlayer (CD layer, such as...) was exposed. Figure 2 As shown), the interlayer is a silty clay layer, 1.8–2.5 m thick, buried at a depth of 8–10 m, with a natural moisture content of 32% and a natural shear strength of 8.5 kPa. It softens easily when exposed to water and has a potential slip surface (BCD surface, as shown). Figure 2 (As shown) The slope has strong continuity, but the safety factor is only 1.08, lower than the standard requirement of 1.30, requiring reinforcement. This example uses the steel pipe grouting reinforcement method of the present invention, combined with the attached... Figure 2 Construction was carried out based on the structural design.

[0034] Specific implementation process: 1. Slope investigation and borehole location Based on the geological survey report and on-site measurements of the slope excavation surface, the attitude of the weak interlayer CD was determined to be 310° strike, 130° dip, and 12° dip angle. The sliding direction of the potential slip surface BCD pointed outwards from the slope. The reinforcement area was designated as the slope platform segment EO (e.g., Figure 2 (as shown) and the slope toe area; Vertical grouting holes were arranged in a quincunx pattern on the slope platform EO, with a hole spacing of 2.5m; oblique grouting holes were arranged in a quincunx pattern at the toe of the slope, with a hole spacing of 2.5m. The holes were accurately laid out and marked using a total station, with a total of 36 vertical holes and 24 oblique holes.

[0035] 2. Steel pipe fabrication and drilling Steel pipe fabrication: Select seamless steel pipes with an outer diameter of 89mm and a wall thickness of 5mm. Drill quincunx-shaped holes in the pipe section corresponding to the weak interlayer (8-10m depth range), with a hole diameter of 9mm and a hole spacing of 400mm. Wrap the outside of the grouting section with a geotextile protective layer and weld a conical pile tip to the bottom of the pipe. Drilling and Installation: Vertical holes: The borehole diameter is 110mm (21mm larger than the outer diameter of the steel pipe), and dry drilling is used. The hole depth is 15m, ensuring that it penetrates the weak interlayer and extends 3m into the underlying stable sandstone. The anchorage length above and below the weak interlayer is 3.5m (anchorage length ratio of 1.0). After cleaning the hole, the steel pipe is installed to the bottom of the hole. Two rows of vertical steel pipes are arranged in parallel with a row spacing of 2.0m. Inclined hole: The drilling direction is perpendicular to the potential slip surface BCD, with an inclination angle of 10° and a hole diameter of 110mm. The mud wall protection method is used for construction, and the hole depth is 18m. It is ensured that after penetrating the weak interlayer, it penetrates into the stable sandstone to a depth of 3.2m (meeting the requirement of ≥2.0m). After cleaning the hole, steel pipes are installed. Two rows of inclined steel pipes are arranged alternately with a row spacing of 2.0m.

[0036] 3. Grout preparation and pressure grouting Grout preparation: Use pure cement grout with a water-cement ratio of 0.5:1, add 0.8% polycarboxylate superplasticizer by weight of cement, and stir for no less than 3 minutes to ensure that the grout is uniform, free of lumps, and has good pumpability; Pressure grouting: A segmented grouting process was adopted, with each segment having a length of 2m, focusing on grouting the weak interlayer area at a depth of 8-10m; Following the principle of "outer perimeter first, then inner perimeter; lower row first, then upper row", the grouting holes on the outer perimeter of the slope platform and the outer side of the slope toe are constructed first, and then the inner holes are constructed. Dual control standards are implemented: the grouting amount per meter of steel pipe is controlled at 85kg of cement, and the grouting pressure is stabilized for 8 minutes after reaching 1.2MPa (meeting the requirements of ≥1.0MPa and 5-10 minutes). Grouting of the hole is terminated when either standard is met.

[0037] 4. Grouting completion and post-treatment Grouting termination: All boreholes met one of the dual control standards. Among them, 28 boreholes were terminated because the grouting volume met the standard, and 32 boreholes were terminated because the pressure met the standard. The total grouting volume was 58.6t of cement. Equipment cleaning: Immediately after grouting is completed, rinse the grouting pump, pipelines and steel pipes with clean water to prevent the grout from solidifying and causing blockages; Steel pipe treatment: Cut the exposed steel pipe ends to be flush with the slope and seal the pipe openings with C30 high-strength mortar; Curing: The ambient temperature of the grouting area shall be controlled at 15-25℃ (≥5℃, corresponding to claim 9). During the curing period, excavation, compaction and other disturbing operations shall be prohibited on the slope. The curing time shall be 10 days (≥7 days).

[0038] Example effect: After reinforcement, samples were taken from the weak interlayer for testing, and its shear strength increased to 11.5 kPa, an increase of 35.3%. The slope stability calculation results show that the safety factor has been increased to 1.38, which meets the requirements of the specifications; through 6 months of slope displacement monitoring, the maximum horizontal displacement is only 3mm and the vertical displacement is 2mm, with no obvious slippage trend, achieving long-term stability; The construction period is only 28 days, which is 40% shorter than the traditional anti-slide pile construction, and the project cost is reduced by 35%. Moreover, the construction process causes little disturbance to the slope and there is no risk of new deformation.

[0039] It is worth noting that, Figure 2 middle: Line segment AB: represents the original ground surface outline (or top boundary line) before slope excavation, defining the upper starting range of slope excavation; Line segment BC: represents a potential slip surface, which is the fracture path along the weak interlayer of the slope where slippage may occur; Line segment CD: Represents a weak interlayer (such as silty clay layer, fractured rock layer, etc.), which is the core weak area of ​​slope instability and needs to be reinforced by grouting through steel pipes. Line segment DE: represents the unexcavated slope segment, reflecting the boundary range of slope excavation; Point O and Platform EO: Point O is the key node of the slope platform, and EO is the slope reinforcement platform, which is the area for the vertical steel pipes (as in the embodiment, the vertical reinforcement unit is laid on platform EO). Steel perforated pipes (black lines in the diagram): These are divided into vertical steel perforated pipes (placed on platform EO) and diagonal steel perforated pipes (placed in the slope toe area). The two are arranged in a cross pattern to form a three-dimensional composite reinforcement body, which is used to reinforce the weak interlayer CD and the potential slip surface BC.

[0040] The diagram visually presents the spatial structure of the slope, the location of weak interlayers, potential instability paths, and the spatial distribution of the steel pipe reinforcement system through the layout of geometric line segments and steel pipes, providing clear visual support for understanding the invented "three-dimensional collaborative reinforcement system".

[0041] Beneficial effects: This example is highly targeted and has a clear reinforcement mechanism: targeting the weak interlayer as a key factor in slope instability, the angle and depth of the steel pipe layout are optimized to enable it to penetrate the potential slip surface most effectively, forming a composite reinforcement system of "micro anti-slide piles" and "three-dimensional reinforcement". At the same time, the shear strength of the weak interlayer itself is significantly improved through grout vein solidification. Dual-control grouting ensures reliable quality: The dual control standard of "grouting volume" and "grouting pressure" ensures that the grout effectively fills, penetrates and compacts the weak interlayer, avoiding reinforcement failure caused by insufficient grouting and preventing slope disturbance caused by excessive pressure, thus ensuring the uniformity and integrity of the reinforced body. Convenient construction and high overall benefits: Compared to large-scale anti-sliding structures, this method offers flexible and rapid construction with minimal interference to slope excavation. Standardized processes and parameter control reduce the complexity of construction organization, enabling effective control of schedule and cost, resulting in high cost-effectiveness. Preventing problems before they occur and ensuring long-term stability: This method can fundamentally improve the properties of soil and rock, and the resulting mesh-like reinforcement can effectively inhibit the gradual damage of slopes. Combined with a slope monitoring system, it can achieve full life-cycle safety of slopes and meet the requirement of a 15-year service life.

[0042] In summary, this method, through targeted scheme design, effectively treats weak interlayer slopes from three aspects: structural reinforcement, construction control, and long-term stability. The specific effects are as follows: 1. Targeted solutions to instability issues to improve slope anti-slide capacity. The three-dimensional collaborative reinforcement system precisely matches the instability mode of slope sliding along the weak interlayer: the vertical reinforcement unit bears the lateral earth pressure and restricts the displacement of the soil above and below the interlayer, while the inclined reinforcement unit anchors the slope and compacts the interlayer. The three-dimensional composite reinforcement body formed by the two directly blocks the sliding path and cements the loose soil of the weak interlayer, fundamentally improving the mechanical properties of the interlayer and greatly reducing the risk of slope sliding along the weak interlayer. 2. Ensure reinforcement quality and avoid potential construction hazards. The plum blossom-shaped hole positioning ensures that there are no blind spots in the reinforcement. The segmented dual-control grouting avoids reinforcement failure caused by insufficient grouting and prevents slope disturbance caused by excessive pressure. The structural design of the steel flower pipe ensures that the grout is accurately injected into the interlayer. Multi-link coordinated control makes the reinforced body dense, uniform, and has stable and reliable strength, solving the problem of unstable quality in traditional reinforcement. 3. Convenient construction, reducing disturbance to slopes. Compared with large structures such as anti-slide piles and gravity retaining walls, steel pipe grouting construction is flexible and fast, does not require large-scale excavation, and causes little disturbance to the original soil on the slope. The standardized construction process (from hole location to post-maintenance) reduces the complexity of construction organization, facilitates on-site operation, and reduces construction period and cost input, taking into account both economy and practicality. 4. Achieve long-term slope stability The three-dimensional composite reinforcement formed after grouting combines the weak interlayer with the surrounding stable soil into a whole, which can effectively inhibit the gradual failure of the slope. With proper post-construction maintenance, the strength of the reinforcement can be maintained stably, ensuring the slope's ability to resist external disturbances (such as rainwater soaking and temperature changes) during long-term service, and avoiding the problem of short-term reinforcement failure.

[0043] Working principle: This method, through a "three-dimensional collaborative reinforcement system + precise construction control," specifically addresses the instability problem of slopes sliding along weak interlayers. The specific principle is as follows: 1. Mechanical action of three-dimensional synergistic reinforcement system A three-dimensional reinforcement system combining vertical and inclined reinforcement units is constructed: vertical reinforcement units are placed on the slope platform, with steel pipes penetrating the weak interlayer and controlling the ratio of upper and lower anchorage lengths. They can bear the lateral earth pressure of the slope like "miniature anti-slide piles" and exert shear and torsional resistance through their own stiffness, thus constraining the relative displacement of the soil above and below the weak interlayer. Inclined reinforcement units are placed at the toe of the slope at a specific angle (perpendicular to the potential sliding surface), with steel pipes pointing behind the potential slip surface and penetrating into the stable layer. This not only has the effect of "soil nailing" anchorage—limiting slope slippage through the friction between the steel pipes and the surrounding cemented soil—but also "directionally compacts" the weak interlayer, squeezing out loose voids and increasing the density of the interlayer. After the two intersect in space, a three-dimensional composite solidification body composed of cement grout veins and steel pipe skeleton is formed on the path of the weak interlayer and potential slip surface. This solidification divides, wraps and cements the weak interlayer, structurally changes the stress state of the weak interlayer and blocks the slip path. 2. The Guarantee Principle of Precise Construction Control 2.1 Plum blossom-shaped hole arrangement: Based on the location of weak interlayers and potential slip surfaces determined by geological survey, the grouting holes are arranged in a plum blossom shape to ensure that the reinforcement area accurately covers the risk areas and avoids reinforcement blind spots; 2.2 Segmented Dual-Control Grouting: The grouting process is controlled by dual standards of grouting volume and grouting pressure. This ensures that the grout fully fills the voids in the weak interlayer and compacts the loose soil (avoiding incomplete reinforcement due to insufficient grouting), while also preventing excessive grouting pressure from disturbing the original soil of the slope (avoiding new deformation). This ensures that the grout is evenly distributed within the weak interlayer, forming a complete and dense grout vein. 2.3 Steel Pipe Structure Design: The steel pipe has perforated holes drilled in the pipe section corresponding to the depth of the weak interlayer to ensure that the grout is accurately injected into the interlayer area and to avoid grout waste in non-critical areas; the protective layer wrapped around the grouting section can prevent the perforated holes from being blocked by the soil, and the conical pile tip at the bottom of the pipe ensures that the steel pipe can be smoothly inserted into the designed depth, providing a foundation for grout penetration and force transmission of the steel pipe skeleton.

[0044] How to use: This method involves four steps according to the construction process, with each step closely adhering to the reinforcement principle to ensure construction accuracy: 1. Slope investigation and borehole location First, based on the geological survey report and the actual excavation surface of the slope, the location and attitude (such as the direction of inclination and thickness) of the weak interlayer are determined. Then, the areas that need to be reinforced are determined through potential slip surface analysis. On the slope platform and slope surface, grouting holes are arranged in a quincunx pattern. The hole positions are accurately laid out and marked with measuring instruments to ensure that the hole positions correspond to the risk areas, laying a good foundation for the subsequent steel pipe laying.

[0045] 2. Steel pipe fabrication and drilling 2.1 Steel pipe fabrication: Select steel pipes of specific specifications, drill quincunx-shaped holes on the pipe section corresponding to the depth of the weak interlayer, wrap the outside of the grouting section with a protective layer, and weld a conical pile tip to the bottom of the pipe to ensure that the steel pipe can smoothly transfer grout and be stably inserted into the hole. 2.2 Drilling and Installation: Drill holes to the designed depth using a drilling rig. The drilling direction is adjusted according to the orientation of potential slip surfaces to ensure that the drill can penetrate weak interlayers and reach stable layers. After cleaning the hole, install the prepared steel perforated pipe to the designed depth in the hole to ensure that the steel perforated pipe can effectively play its anchoring and supporting role.

[0046] 3. Grout preparation and pressure grouting 3.1 Grout preparation: Prepare pure cement grout according to the proportion, or add water-reducing agent, early strength agent and other admixtures according to geological conditions (such as soil looseness and moisture content) to ensure that the grout has good pumpability and bonding ability. 3.2 Pressure grouting: A segmented grouting process is adopted, focusing on injecting grout into the weak interlayer area; during grouting, the principle of "first the outer perimeter, then the inner perimeter, first the lower row, then the upper row" is followed, and the grouting process is controlled according to the dual control standard - when the set grouting volume is reached or the grouting pressure is stable for the required time, the grouting of that hole is stopped to avoid grout waste or slope disturbance.

[0047] 4. Grouting completion and post-treatment After grouting is completed, clean the grouting equipment in a timely manner (to prevent the grout from solidifying and clogging the equipment); cut the exposed steel pipe ends to be flush with or slightly higher than the slope surface, and seal them with high-strength mortar (to prevent the steel pipes from rusting); cure the grouting area for no less than 7 days, control the ambient temperature and avoid slope disturbance during the curing period, and ensure that the grout is fully hydrated and hardened to form stable strength. Subsequent slope operations can only be carried out after the strength meets the standard.

[0048] In this embodiment, in order to accurately match the steel pipe layout and grouting control and achieve a dynamic balance between reinforcement effect and construction efficiency, a collaborative equation for grouting parameters for three-dimensional reinforcement of weak interlayers is also proposed: ; This equation is used to calculate the total grouting volume of steel pipe grouting for weak interlayer slopes. By integrating the characteristics of potential slip surfaces, reinforcement unit layout parameters, grouting process indicators and soil and rock properties, it achieves accurate quantitative design of grouting parameters and avoids the problems of insufficient grouting or excessive disturbance caused by traditional experience-based values. The derivation of the equation is as follows: 1. Derivation premises The goal of reinforcement is to ensure that the shear strength of the weak interlayer meets the slope stability requirements, i.e., the shear strength of the composite soil-rock mass after grouting is greater than or equal to the design requirement. ; The grouting volume needs to cover the entire potential slip surface area, while matching the synergistic reinforcement range of vertical and inclined steel pipes; The grouting effect is affected by grouting pressure, holding time, and effective utilization rate of grout, and needs to be taken into quantitative consideration. 2. Step-by-step derivation Quantification of slip surface reinforcement requirements: Potential slip surface length is L slip If the unit weight of the weak interlayer is γ, then the correlation value of the total mass of the soil and rock mass in the slip surface region is L. slip •γ requires grouting to enhance shear strength, corresponding to the core requirement item L. slip ·γ· ; Integration of reinforcement unit coverage: Effective anchorage length L of vertical steel perforated pipe v Effective anchorage length L of the inclined steel pipe ob The sum of these values ​​reflects the coverage depth of the three-dimensional reinforcement. Combined with the angle α between the inclined steel pipe and the slip surface (α = 90° when perpendicular to the slip surface), its synergistic effect coefficient is sinα·(L). v +L ob (sinα ensures that the oblique reinforcement force is effectively transmitted along the normal direction of the slip surface). Grouting process efficiency correction: Design grouting pressure P des Duration t hold The effectiveness of grout penetration and compaction is determined by the grout utilization rate η (considering losses due to grout leakage and soil adsorption), which corrects for the actual effective grouting volume. These three factors work together to constitute the process efficiency term P. des ·t hold ·η; Synergy coefficient introduction: k is the synergy coefficient of three-dimensional reinforcement (the value ranges from 1.1 to 1.5, and is adjusted according to the slope safety level), which is used to correct the superposition effect of grout veins caused by the cross arrangement of vertical and inclined steel pipes; Total Grouting Volume Integration: Combining the above factors, the total grouting volume Q is finally derived. total The quantitative formula enables the coordination of demand, parameters, and process. Parameter description table: .

[0049] Example: 1. Given conditions Slope safety level: Level II (k=1.3); Potential slip surface length L slip =20m; The unit weight of the weak interlayer is γ = 20 kN / m³; Design requirements for shear strength =120kPa; The angle between the inclined steel pipe and the slip surface is α=90° (sinα=1); Effective anchorage length L of vertical steel perforated pipe v =3m; Effective anchorage length L of inclined steel pipe ob =3.5m; Design grouting pressure P des =1.2MPa; Grouting holding time t hold =8min; The effective utilization rate of slurry η = 0.8.

[0050] 2. Calculation process: .

[0051] 3. Application Results The total grouting volume for this slope is designed to be 81.1t. With a hole spacing of 2.5m and 16 steel pipes, the grouting volume per steel pipe can be calculated to be approximately 5.07t, which meets the dual control standard of "75~100kg of grouting volume per meter of steel pipe" (the length of a single steel pipe is 12m, and the grouting volume per meter is approximately 422kg. Since it includes the grouting section of the stable layer, the grouting ratio of the weak interlayer section needs to be adjusted in conjunction with the segmented grouting process).

[0052] Technical effects: 1. The synergistic effect of three-dimensional reinforcement units, the characteristics of slip surface, and grouting process parameters are integrated into a quantitative equation, breaking through the limitations of traditional empirical values; the effective utilization rate of grout and the three-dimensional synergistic coefficient are introduced to solve the problem of grouting parameter adaptability under different geological conditions, providing support for personalized design; 2. Achieve closed-loop quantification of "reinforcement requirements - layout parameters - process indicators", upgrading grouting volume design from "experience judgment" to "precise calculation", avoiding insufficient grouting or excessive disturbance; the equation is deeply matched with the three-dimensional collaborative reinforcement system, ensuring that the grout vein forms a uniform composite reinforcement body on the potential slip surface, significantly improving the pertinence of the reinforcement mechanism; 3. The simplified construction parameter design process allows for rapid calculation of the total grouting volume based directly on geological survey data and design requirements, guiding the allocation of grouting volume for individual steel pipe sections. Complementing the dual-control standard, it satisfies both grouting volume and pressure requirements while ensuring reinforcement effectiveness through parameter coordination, reducing construction trial-and-error costs.

[0053] Working principle and process: 1. Parameter acquisition: Obtain soil and rock parameters such as the unit weight of weak interlayers and the length of potential slip surfaces through geological exploration, and determine the synergy coefficient k in combination with the slope safety level; 2. Design Input: Determine the effective anchorage length of vertical / inclined steel pipes and the included angle of inclined steel pipes according to the pipe laying scheme, and set the grouting pressure and holding time according to the process requirements; 3. Efficiency Correction: Adjust the effective utilization rate η of the slurry according to the type of weak interlayer (loose / viscous); 4. Equation Calculation: Substitute into the equation to obtain the total grouting volume, and break it down to individual steel pipes and segmented grouting stages; 5. Construction Application: Perform grouting operations according to the calculation results, and make real-time adjustments in conjunction with the dual control standards to ensure that the grouting volume and pressure meet the standards; 6. Effect verification: After grouting is completed, the rationality of the equation calculation is verified by slope displacement monitoring and composite soil shear strength test.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipe grouting, characterized in that... Includes the following steps: Step 1: Slope Investigation and Hole Location: Based on the geological survey report and the slope excavation surface, identify the location and attitude of the weak interlayers, and determine the reinforcement area based on the analysis of potential slip surfaces; arrange grouting holes in a quincunx pattern on the slope platform and slope surface, with a hole spacing of 2.0m to 3.0m, and use measuring instruments to accurately lay out and mark the hole positions; Step 2, Steel Pipe Fabrication and Drilling: Fabricate steel pipes that meet the requirements, use a drilling rig to drill holes to the designed depth, and adapt the drilling direction to the potential slip surface to ensure that the weak interlayer is penetrated and the stable layer is penetrated to a depth of not less than 1.0m. After cleaning the hole, install the steel pipe to the designed depth in the hole. Step 3, Grout Preparation and Pressure Grouting: Prepare grout with a specific ratio, adopt a segmented grouting process, focus on covering the weak interlayer in the grouting area, implement the principle of dual control of grouting volume and grouting pressure, and follow the principle of skipping holes from the outer perimeter to the inner perimeter and from the lower row to the upper row in the grouting sequence. Step 4: Grouting Completion and Post-Injection Treatment: Grouting shall be terminated when one of the grouting control standards is met. The grouting equipment shall be cleaned, the exposed steel pipe ends shall be treated, and the grouting area shall be cured for no less than 7 days. Subsequent operations shall be carried out after the grout strength reaches the standard.

2. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 1, characterized in that, The steel pipes deployed in step two constitute a three-dimensional collaborative reinforcement system. This system includes vertical reinforcement units and inclined reinforcement units. The vertical reinforcement unit consists of at least one row of steel pipes vertically deployed on the slope platform. The steel pipes penetrate the weak interlayer and extend into the stable soil layer below it. The ratio of the anchorage lengths in the soil and rock mass above and below the weak interlayer is 0.8 to 1.

2. The inclined reinforcement unit consists of at least one row of steel pipes inclined at the toe of the slope at an angle of 5° to 15°. The angle is perpendicular to the potential sliding surface, and the steel pipes are deployed behind the potential slip surface. The steel pipes penetrate the weak interlayer and extend into the stable layer for a depth of not less than 2.0m. The vertical reinforcement units and the inclined reinforcement units are spatially intersected to form a three-dimensional composite reinforcement body in the weak interlayer and along the path of the potential slip surface.

3. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 2, characterized in that, The steel pipes of the vertical reinforcement unit are arranged in two rows, with the two rows of steel pipes arranged in parallel on the slope platform and the row spacing is 1.5m to 2.5m; the ratio of the anchorage length of the steel pipes of the vertical reinforcement unit in the soft interlayer rock and soil is 1.

0.

4. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 2, characterized in that, The inclined reinforcement unit has two rows of steel pipes arranged in a staggered manner at the toe of the slope, with a spacing of 1.8m to 2.2m between rows.

5. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipe grouting according to claim 2, characterized in that, The steel pipe is made of steel pipe with an outer diameter ≥89mm and a wall thickness ≥5mm. Holes are drilled in the pipe section within the depth range of the corresponding weak interlayer. The holes are arranged in a plum blossom shape, with a diameter of 8-10mm and a spacing of 300-500mm. The outside of the grouting section is wrapped with a protective layer, and a conical pile tip is welded to the bottom of the pipe.

6. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 2, characterized in that, The slurry is a pure cement slurry with a water-cement ratio of 0.4:1 to 0.6:1, or a pure cement slurry with admixtures, which are one or more of water-reducing agents, early-strength agents, or expansion agents.

7. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 2, characterized in that, In the aforementioned dual-control principle, the grouting amount per meter of steel pipe is 75kg to 100kg of cement, the grouting pressure reaches and stabilizes at ≥1.0MPa, and the duration is 5 to 10 minutes.

8. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 2, characterized in that, The diameter of the borehole is 20-30 mm larger than the outer diameter of the steel pipe. During the drilling process, mud slurry or dry drilling is used to prevent the borehole wall from collapsing.

9. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 2, characterized in that, The ambient temperature of the grouting area shall not be lower than 5℃, and no disturbing work shall be carried out on the slope during the curing period.

10. The method for reinforcing weak interlayer slopes in highway excavation using steel perforated pipes according to claim 2, characterized in that, The three-dimensional composite reinforcement body is composed of cement grout veins and steel pipe skeleton, which divides, wraps and binds the weak interlayer to improve the shear strength of the weak interlayer.

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