Dewatering and micro pile group coordinated open pit mine slope protection structure and method

Abstract

The open-pit mine slope protection structure and method, which integrates drainage and micropile systems, includes a drainage system and a micropile system that work together. The drainage system comprises a drainage ditch at the bottom of a stepped slope, drainage holes and water pipes on the slope. The water pipes within the drainage holes have filter holes and are covered with a filter screen. A flexible water pipe connects the water pipe to the drainage ditch. The micropile system includes multiple cast-in-place piles embedded in the slope's soil and rock, and a pile top connection frame that connects the tops of the piles. The method for constructing the slope protection structure is divided into two stages and steps: a first stage of three steps for constructing the drainage system, and a second stage of three steps for constructing the micropile system. This method has the advantages of solving the problem of limited slope reinforcement due to the independent and poor coordination of drainage and retaining measures, while also significantly reducing costs.

Description

Technical Field

[0001] This invention relates to the field of open-pit mine slope protection technology, and in particular to an open-pit mine slope protection structure and method that combines drainage and micropile groups. Background Technology

[0002] In open-pit mining, the stability of steep slopes directly affects mine safety and production efficiency. Slope instability is usually caused by the combined effects of internal factors such as rock mass structure and mechanical strength, and external factors such as groundwater and excavation disturbance. Among these, groundwater is one of the most active factors inducing slope instability. It significantly weakens the slope's resistance to sliding by softening the rock and soil, increasing pore water pressure, and causing erosion.

[0003] Currently, the commonly used slope protection techniques in the industry that need to consider both the improvement of hydrogeological conditions and the mechanical reinforcement of soil and rock masses are mainly divided into two categories: one is a drainage system with drainage holes and drainage ditches as the core, which aims to lower the groundwater level; the other is a support structure represented by anti-slide piles and anchors (cables), which aims to provide direct anti-slide force. However, these traditional methods have the following limitations in practical applications: First, the drainage system and the support structure are often designed and constructed independently, failing to fully consider the interaction and synergistic effect between the two; second, traditional anti-slide piles or anchors involve large engineering volume, complex construction, and high cost, and drilling is difficult in water-rich soil and rock, and the anchoring effect is easily affected by groundwater; third, drainage holes are prone to failure due to rock powder blockage or fine particle erosion, while the support structure may experience performance degradation due to corrosion or decreased bond strength in a long-term water pressure environment.

[0004] To address the aforementioned issues, several publications have revealed solutions, including CN202022819909.3, "Micropile Reinforcement and Drainage System for Embankment Slopes After Sliding." This system involves a micropile reinforcement and drainage system for embankment slopes after sliding, comprising an embankment slope and a drainage ditch located at the slope toe. Multiple micropile groups are longitudinally spaced from the slope toe to the slope crest within the slope. A flexible permeable pipe extending from the slope toe into the drainage ditch is installed at the slope toe. A flexible permeable pipe extending onto the slope surface is also installed within the slope. A capping beam is installed at the top of the micropile groups at the slope toe. Although it involves both micropiles and drainage pipes, the flexible permeable pipe, as a drainage element, relies on the material's permeability for drainage, which poses challenges in long-term operation. In operation, the system is prone to collapse and blockage due to insufficient material strength, and there is no effective means to deal with this blockage problem. Furthermore, there is a lack of a true synergistic mechanism between the drainage system and the micropile reinforcement system; that is, the increased porosity of the soil and rock after drainage weakens the mechanical properties of the surrounding medium, and the two are only physically superimposed without any active compensation measures. CN202222828627.9, "A pile structure for slope reinforcement and drainage," relates to a pile structure for slope reinforcement and drainage, including a steel pipe with wellpoint pipes installed inside. The bottom end of the wellpoint pipes is connected to a filter pipe, and the gap between the steel pipe and the wellpoint pipes is filled with sand and gravel. The steel pipe is installed in a borehole on the slope. Reinforcement and drainage functions are integrated into a single pile structure, through which the wellpoint pipes and filter pipes... The system collects and pumps groundwater, offering resistance to landslides and precipitation. However, its drainage relies on wellpoint pipes and filter pipes, making it a passive drainage system. It requires pumping equipment to extract the collected groundwater, resulting in a complex system with high maintenance costs and a lack of a systematic design for a three-dimensional drainage network. The drainage range is limited to the perimeter of individual piles, making it difficult to effectively reduce pore water pressure within large-area slopes. Furthermore, grouting only fills the gap between the pile and the borehole wall during pile formation, without actively backfilling the pores in the soil and rock that may be formed due to drainage. CN202410776200.X, "A Landslide Protection Structure for Open-Pit Slopes in Quicksand Layers," relates to a landslide protection structure for open-pit slopes in quicksand layers, including a first fiber concrete layer, drainage ditches, dewatering channels, and shallow... The grouting holes and the second fiber concrete layer are connected to the drainage ditch at the outer end of the drainage channel and to the groundwater at the inner end. Cement grout is injected into the shallow grouting holes, and the cement grout can penetrate into the bottom slope to fill the pores of the quicksand layer after the groundwater is drained. It involves both drainage and grouting. However, the grouting is only used as an independent anti-seepage reinforcement measure. It lacks organic connection with the construction sequence and spatial layout of the drainage system and fails to form a closed-loop collaborative mechanism of "drainage-reinforcement-backfilling". In addition, the drainage method is single, the layout of the drainage channel does not form a multi-stage three-dimensional network, and the grouting holes are shallow grouting, which cannot form an integrated load-bearing structure with the deep piles. CN202511319813.1. "A Micropile Combination Reinforcement Method for Highway Expansive Soil Slopes" addresses the reinforcement of highway expansive soil slopes using micropile combinations. It employs a micropile group as the retaining structure for the slope, reinforcing the slope through grouting micro-steel pipe piles. While it claims to solve the problem of traction-induced sliding caused by the expansion and softening of expansive soil upon contact with water and its shrinkage and cracking upon water loss, this technology clearly lacks an independent drainage system. The micropile grouting process itself does not constitute a drainage structure, and therefore cannot systematically lower the groundwater level within the slope. Even when combined with surface drainage ditches in some expansive soil slope projects, the drainage and micropile systems are merely physically superimposed, each functioning independently.

[0005] Therefore, it is of great significance to develop a slope protection structure and method for open-pit mines that combines drainage and micro-piles. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an open-pit mine slope protection structure and method that combines drainage and micro-piles. This can solve the problem that drainage and retaining measures are independent and have poor coordination, resulting in limited slope reinforcement effect, and can also greatly reduce costs.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] An open-pit mine slope protection structure that integrates drainage and micropile systems comprises a drainage system and a micropile system that work together. The drainage system includes a drainage ditch at the bottom of the stepped slope, drainage holes and water pipes arranged on the slope. The water pipes located within the drainage holes have filter holes and are covered with filter screens, as well as flexible water pipes connecting the water pipes and the drainage ditch. The micropile system includes multiple cast-in-place piles embedded in the slope's soil and rock, and a pile top connection frame that connects the tops of each cast-in-place pile into a whole. This structure can solve the problem of limited slope reinforcement effect caused by the independent and poor coordination of drainage and retaining measures, and greatly reduce mining costs.

[0009] The methods used for slope protection structures are divided into the following two stages and steps:

[0010] Construction steps for the first-stage drainage system:

[0011] S1. Drainage ditch construction: Along the slope direction, drainage ditches are constructed at the bottom line of each step, and polyethylene geomembrane is laid in the ditch to form a continuous seepage-proof layer.

[0012] S2. Construction of multi-step drainage holes and water guide pipes: Determine the location of the drainage steps according to the multi-step three-dimensional drainage scheme; first, drill upward-sloping drainage holes at intervals of 10-20m along the slope direction 0.5-1.5m above the bottom line of the selected step; then determine the length of the water guide pipe according to the depth of the drainage hole, the length of the infiltration section should not be less than 95% of the depth of the drainage hole, and set a closed cone at one end of the infiltration section near the bottom of the hole; then open filter holes around the circumference of the infiltration section and cover it with a filter screen; insert the water guide pipe into the drainage hole, so that the section of the hole without filter holes is exposed outside the hole; finally, use cement mortar to fill and seal the annular gap between the pipe wall and the hole wall within 1 meter of the hole opening.

[0013] S3. Pipe connection: Use a water-conducting hose to connect the outer end of the water-conducting pipe to the drainage ditch to complete the drainage path;

[0014] Two-stage micropile group system construction steps:

[0015] S4. Pile location layout and drilling: On the selected stepped platform in the middle of the slope, first measure and layout in a quincunx pattern, marking at least two rows of drilling positions; then use a down-the-hole drill to drill holes sequentially according to the design inclination angle and depth.

[0016] S5. Pressure grouting pile formation: Steel components are lowered into the hole, and pressure grouting is performed from the bottom of the hole upward through the pre-embedded grouting pipe. Cement mortar is injected until the borehole is filled, forming a cast-in-place pile that is tightly bonded to the surrounding rock and soil.

[0017] S6. Pile top connection: First, a connecting beam is erected between the pile heads exposed at the borehole of each cast-in-place pile to connect all the pile tops into an integral grid. Then, connecting steel bars are arranged and fixed on the connecting beam at the designed intervals. Finally, fine stone concrete is poured integrally on the frame composed of the connecting beam and the steel bars to form a reinforced concrete pier that consolidates the top of the micro pile group into one.

[0018] Compared with the prior art, the innovative points, advantages or effects of this invention are as follows:

[0019] By organically combining the multi-stage three-dimensional drainage system with the top-rigidly connected micropile system, a synergistic effect of "drainage" and "active reinforcement" is achieved. At the same time, the drainage system effectively reduces pore water pressure in the slope and improves the shear strength of the soil and rock. In addition, the micropile system provides anti-sliding force, and its pressure grouting process can backfill and reinforce microcracks and pores that may be generated by drainage. The two complement each other, so the overall stability and safety reserve of the slope can be significantly improved. Moreover, the construction is flexible, the disturbance to the slope is small, and the technical and economic benefits are excellent. Attached Figure Description

[0020] Figure 1This is a cross-sectional view of the overall protection structure of an open-pit mine slope protection structure and method that combines drainage and micro-piles, based on the present invention.

[0021] Figure 2 for Figure 1 A schematic diagram of the cross-section of the water pipe inserted into the drainage hole of the overall protective structure shown.

[0022] Figure 3 for Figure 1 The diagram shows the water pipe structure of the overall protective structure.

[0023] Figure 4 This is a schematic diagram of the pile top connection frame structure of a micropile group system for a slope protection structure and method for open-pit mines that combines drainage and micropile grouping, based on the present invention.

[0024] Figure 5 for Figure 4 Schematic diagram of the AA section.

[0025] Figure 6 This is a schematic diagram of the process flow for a method of slope protection in open-pit mines that combines drainage and micropiles.

[0026] The symbols in the attached diagram represent:

[0027] 1. Drainage ditch 2. Drainage hole 3. Water pipe 301. Filter hole 302. Filter screen 303. Closed cone 4. Water hose 5. Cast-in-place pile 501. Steel component 502. Cement mortar 6. Pile top connection frame 601. Tie beam 602. Reinforcing steel 603. Fine aggregate concrete

[0028] The present invention will now be described in further detail with reference to the accompanying drawings. Detailed Implementation

[0029] like Figures 1-5 As shown, the open-pit mine slope protection structure that combines drainage and micropile systems includes a drainage system and a micropile system that work together. The drainage system includes a drainage ditch 1 located at the bottom of the terrace slope, drainage holes 2 and water pipes 3 arranged on the slope. The section of the water pipe 3 located in the drainage hole 2 has filter holes 301 and is covered with a filter screen 302, as well as a flexible water pipe 4 connecting the water pipe 3 and the drainage ditch 1. The micropile system includes multiple cast-in-place piles 5 embedded in the slope soil and rock, and a pile top connection frame 6 that connects the tops of each cast-in-place pile 5 into a whole. This structure can solve the problem of limited slope reinforcement effect caused by the independent drainage and support measures and poor coordination, and greatly reduce mining costs.

[0030] The slope protection structure of the present invention may further be:

[0031] The drainage ditch 1 is laid along the slope direction at the bottom of each step, and its cross-section is an inverted trapezoid, with a polyethylene geomembrane impermeable layer inside.

[0032] The drainage holes 2 are arranged on the slope as follows: along the slope height direction, a row of drainage holes 2 is constructed every 1 to 2 steps; along the slope direction, the spacing of the same row of drainage holes 2 is 10 to 20 m; the depth of each drainage hole 2 is 40 to 60 m.

[0033] The water guide pipe 3 is divided into sections inside and outside the drainage hole 2. The section inside the drainage hole 2 is the infiltration section. The filter holes 301 are circumferentially opened on the pipe wall of the infiltration section and are arranged in an alternating long strip shape. The length of the infiltration section is not less than 95% of the depth of the drainage hole 2, and a closed cone 303 is set at one end near the bottom of the hole.

[0034] The two ends of the water-conducting hose 4 are respectively connected to the outlet end outside the hole of the water-conducting pipe 3 and the drainage ditch 1.

[0035] The cast-in-place pile 5 is constructed by drilling to the designed depth on the stepped platform, with a steel component 501 inside the hole and cement mortar 502 poured in, forming a pile body that is tightly integrated with the surrounding rock and soil.

[0036] The pile top connection frame 6 includes a connecting beam 601 and a reinforced concrete pier formed by integrally pouring fine stone concrete 603 after binding longitudinally and transversely arranged steel bars 602 on the connecting beam 601. The connecting beam 601 connects the pile tops of all cast-in-place piles 5.

[0037] like Figure 6 As shown, the method for the slope protection structure described in any of the above items is divided into the following two stages and steps:

[0038] Construction steps for the first-stage drainage system:

[0039] S1. Drainage ditch construction: Along the slope direction, drainage ditch 1 is opened at the bottom line of each step, and a polyethylene geomembrane is laid in the ditch to form a continuous seepage prevention layer.

[0040] S2. Construction of multi-step drainage holes and water guide pipes: Determine the location of the drainage steps according to the multi-step three-dimensional drainage scheme; first, drill upward-sloping drainage holes 2 at intervals of 10-20m along the slope direction 0.5-1.5m above the bottom line of the selected step; then determine the length of the water guide pipe 3 according to the depth of the drainage hole 2, the length of the infiltration section is not less than 95% of the depth of the drainage hole 2, and a closed cone 303 is set at one end of the infiltration section near the bottom of the hole; then, filter holes 301 are opened around the infiltration section and covered with filter screens 302; insert the water guide pipe 3 into the drainage hole 2, so that the section of the hole without filter holes 301 is exposed outside the hole; finally, use cement mortar to fill and seal the annular gap between the pipe wall and the hole wall within 1 meter of the hole opening.

[0041] S3. Pipeline connection: Use the water-conducting hose 4 to connect the outer end of the hole of the water-conducting pipe 3 to the drainage ditch 1 to complete the drainage path connection;

[0042] Two-stage micropile group system construction steps:

[0043] S4. Pile location layout and drilling: On the selected stepped platform in the middle of the slope, first measure and layout in a quincunx pattern, marking at least two rows of drilling positions; then use a down-the-hole drill to drill holes sequentially according to the design inclination angle and depth.

[0044] S5. Pressure grouting pile formation: Steel component 501 is lowered into the hole, and pressure grouting is carried out from the bottom of the hole upward through the pre-embedded grouting pipe. Cement mortar 502 is injected until the borehole is filled, forming a cast-in-place pile 5 that is tightly bonded to the surrounding rock and soil.

[0045] S6. Pile top connection: First, a connecting beam 601 is erected between the pile heads exposed at the borehole of each cast-in-place pile 6 to connect all the pile tops into an integral grid. Then, connecting steel bars 602 are arranged and fixed on the connecting beam 601 at the designed intervals. Finally, fine stone concrete 603 is poured integrally on the frame formed by the connecting beam 601 and the steel bars 602 to form a reinforced concrete pier that consolidates the top of the micro pile group into one unit.

[0046] The method for slope protection structures of the present invention can be further described as follows:

[0047] The cross-section of the drainage ditch 1 in step S1 is an inverted trapezoid.

[0048] The depth of the drainage hole 2 in step S2 is 40-60m.

[0049] Example 1

[0050] Reference Figures 1 to 5 This embodiment describes in detail the specific composition of the protective structure:

[0051] The drainage system mainly consists of drainage ditch 1, drainage holes 2, water guide pipes 3, and water guide hoses 4. Drainage ditch 1 is laid along the slope direction at the bottom of each step, with a slope of 3‰. Its cross-section is designed as an inverted trapezoid to facilitate the collection and diversion of slope water. To prevent water infiltration, a polyethylene geomembrane is laid and welded inside the ditch to form a continuous impermeable layer. Drainage holes 2 and water guide pipes 3 are the core seepage collection units of the system. Water guide pipes 3 are segmented and located inside and outside drainage holes 2. The drainage holes 2 are arranged in a multi-step, three-dimensional drainage pattern: in the vertical direction of the slope, a row of boreholes is set at intervals of 1 to 2 steps; in the horizontal direction, the spacing between boreholes in the same row is controlled between 10 and 20 meters; the depth of a single borehole is 40 to 60 meters to ensure that the borehole can penetrate potential slip surfaces or major aquifers. Thus, 2 to 3 rows of drainage holes can be formed on a single slope surface, constituting a three-dimensional groundwater drainage network.

[0052] The water guide pipe 3 is a key water conveyance component, and the portion within the drainage hole 2 is called the infiltration section. This section has multiple rows of staggered, elongated filter holes 301 arranged around its circumference, and is tightly covered with a filter screen 302 to prevent soil particles from entering and causing blockage. The length of the infiltration section is no less than 95% of the total depth of the drainage hole, and a closed conical head 303 is welded to one end near the bottom of the hole for easy installation and to prevent clogging at the bottom. The section of the water guide pipe 3 without filter holes 301 protrudes from the slope. The flexible water guide hose 4 serves as a connecting component, with one end connected to the section of the water guide pipe 3 and the other end connected to the drainage ditch 1, thereby concentrating and draining the groundwater collected from each drainage hole into the ditch. The micropile system is designed in conjunction with the drainage system, including multiple cast-in-place piles 5 and a pile top connecting frame 6. The cast-in-place piles 5 are formed using a pressure grouting process. First, boreholes are drilled to the predetermined depth at the selected pile locations on the stepped platform. Then, steel components such as steel cages or structural steel sections 501 are lowered as reinforcement. Finally, pressure grouting is performed from the bottom of the hole upwards through pre-embedded grouting pipes, injecting cement mortar 502. Under pressure, the grout not only fills the borehole to form the pile body but also penetrates into the surrounding soil and rock, thereby reinforcing the surrounding medium and ensuring a tight bond between the pile body and the soil and rock. The pile top connecting frame 6 is used to connect the dispersed micropiles into a unified load-bearing structure. The construction process is as follows: first, connecting beams 601 are erected between the pile heads of each exposed cast-in-place pile 5 to initially connect all the pile tops into a grid; then, longitudinally and transversely arranged steel bars 602 are tied on the connecting beams 601; finally, fine stone concrete 603 is poured as a whole to form a reinforced concrete pier that consolidates the top of the entire micropile group into one unit, thereby significantly improving the overall bending and shear resistance of the pile group.

[0053] Example 2

[0054] Reference Figure 6This embodiment is based on the structure described in Embodiment 1, and details its construction method, namely, the open-pit mine slope protection method for the coordinated use of drainage and micropile groups, specifically including the following steps and conditions:

[0055] (1) Construction of the drainage system:

[0056] a. Drainage ditch construction: Excavate an inverted trapezoidal trench along the bottom line of each step of the slope, and then lay and weld a polyethylene geomembrane in the trench to form a seepage-proof drainage ditch 1.

[0057] b. Drainage hole formation: Based on the location of potential slip surfaces or aquifers determined by geological surveys, a three-dimensional drainage network is planned. On the selected step, at a distance of 0.5 to 1.5 meters above the slope baseline, drainage holes 2 are drilled according to the designed inclination angle, spacing (10-20 meters), and depth (40-60 meters) to form 2 to 3 rows of three-dimensional drainage hole arrays.

[0058] c. Installation of the water guide pipe: Prepare water guide pipe 3, ensuring that the length of its infiltration section is not less than 95% of the hole depth, and that a closed conical head 303 is installed at the bottom. The filter screen 302 is wrapped around the water filter hole 301 section. Insert it into the drainage hole, leaving the section without the filter hole 301 exposed on the slope. Finally, seal the annular gap of approximately 1 meter around the water guide pipe hole opening with cement mortar to achieve a watertight seal.

[0059] d. Pipeline connection: Use water-conducting hoses 4 to connect the opening sections of each water-conducting pipe 3 to the drainage ditch 1 to complete the laying of the entire drainage path.

[0060] (2) Construction of micropile group system:

[0061] a. Pile location layout and drilling: On the stepped platform in the middle of the slope area requiring reinforcement, pile locations are laid out in a quincunx pattern. Down-the-hole drills are used to drill at the designed angle and depth.

[0062] b. Lowering the steel component and pressure grouting: The fabricated steel component 501 is lowered to the bottom of the hole, and then pressure grouting is performed through the grouting pipe. The grouting material is cement mortar 502, and the grouting pressure is required to ensure that the grout can effectively penetrate into the surrounding soil and rock, thereby forming the cast-in-place pile 5 and simultaneously reinforcing the surrounding soil.

[0063] c. Constructing the pile top connection frame: Install connecting beams 601 between the pile heads to form a foundation connection grid. Then tie the designed steel bars 602 on the beams to form a steel mesh. Finally, formwork is erected as a whole and fine stone concrete 603 is poured to form a solid reinforced concrete pier, connecting the top of the micropile group into a rigid whole, forming the pile top connection frame 6.

[0064] This invention, through the synergistic implementation of the aforementioned structure and method, firstly utilizes a three-dimensional dewatering system to effectively reduce pore water pressure within the slope, thereby increasing the effective stress and shear strength of the soil and rock mass; then, it employs a micropile system to provide active anti-sliding force, and its pressure grouting process compensates for any weakening of the soil structure that may occur due to drainage. The two are closely integrated in terms of space and function, jointly and significantly improving the long-term stability and safety margin of open-pit mine slopes under complex hydrogeological conditions.

[0065] As described above, the present invention can be well implemented. The above embodiments are only the best implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are all included within the protection scope of the present invention.

Claims

1. An open-pit mine slope protection structure that combines drainage and micropile groups, characterized in that... It includes a drainage system and a micro-pile system that work together; the drainage system includes a drainage ditch (1) at the bottom of the stepped slope, drainage holes (2) and water pipes (3) arranged on the slope body, the water pipe (3) has a filter hole (301) on the pipe section located in the drainage hole (2) and is covered with a filter screen (302), and a water pipe (4) connecting the water pipe (3) and the drainage ditch (1); the micro-pile system includes multiple cast-in-place piles (5) embedded in the slope rock and soil, and a pile top connection frame (6) that connects the tops of each cast-in-place pile (5) into a whole, which can solve the problem that the drainage and support measures are independent and have poor coordination, resulting in limited slope reinforcement effect and greatly reduce mining costs.

2. The slope protection structure according to claim 1, wherein The drainage ditch (1) is laid along the slope direction at the bottom of each step, and its cross-section is an inverted trapezoid, with a polyethylene geomembrane impermeable layer inside.

3. The slope protection structure according to claim 1, wherein The layout of the drainage holes (2) on the slope is as follows: along the slope height direction, a row of drainage holes (2) is constructed every 1 to 2 steps; along the slope direction, the spacing between the drainage holes (2) in the same row is 10 to 20 m; the depth of the drainage holes (2) is 40 to 60 m / hole.

4. The slope protection structure according to claim 1, wherein The water guide pipe (3) is divided into sections inside and outside the drainage hole (2). The pipe section inside the drainage hole (2) is the infiltration section. The filter holes (301) are circumferentially opened on the pipe wall of the infiltration section and are arranged in an alternating long strip shape. The length of the infiltration section is not less than 95% of the depth of the drainage hole (2), and a closed cone (303) is set at one end near the bottom of the hole.

5. The slope protection structure according to claim 1, wherein The two ends of the water-conducting hose (4) are respectively connected to the outlet end outside the hole of the water-conducting pipe (3) and the drainage ditch (1).

6. The slope protection structure according to claim 1, wherein The cast-in-place pile (5) is constructed by drilling to the designed depth on the stepped platform, with steel components (501) and cement mortar (502) inside the hole, forming a pile body that is tightly integrated with the surrounding rock and soil.

7. The slope protection structure according to claim 1, wherein The pile top connection frame (6) includes a connecting beam (601) and a reinforced concrete pier formed by integrally pouring fine stone concrete (603) after binding longitudinally and transversely arranged steel bars (602) on the connecting beam (601). The connecting beam (601) connects the pile tops of all cast-in-place piles (5).

8. Method for the construction of a slope protection structure according to any one of claims 1 to 7, characterized in that It is divided into the following two stages and steps: Construction steps for the first-stage drainage system: S1. Drainage ditch construction: Along the slope direction, drainage ditches (1) are opened at the bottom line of each step, and polyethylene geomembrane is laid in the ditch to form a continuous seepage prevention layer. S2. Construction of multi-step drainage holes and water pipes: The location of the drainage steps is determined according to the multi-step three-dimensional drainage scheme; first, drainage holes (2) are drilled at intervals of 10-20m along the slope direction 0.5-1.5m above the bottom line of the selected step; then, the length of the water pipe (3) is determined according to the depth of the drainage hole (2), and the length of the infiltration section is not less than 95% of the depth of the drainage hole (2), and a closed cone (303) is set at one end of the infiltration section near the bottom of the hole; then, filter holes (301) are opened around the infiltration section and covered with filter screen (302); the water pipe (3) is inserted into the drainage hole (2) so that the section of the hole without filter holes (301) is exposed outside the hole; finally, cement mortar is used to fill and seal the annular gap between the pipe wall and the hole wall within 1 meter of the hole opening. S3. Pipeline connection: Use a water-conducting hose (4) to connect the outer end of the hole of the water-conducting pipe (3) to the drainage ditch (1) to complete the drainage path connection; Two-stage micropile group system construction steps: S4. Pile location layout and drilling: On the selected stepped platform in the middle of the slope, first measure and layout in a quincunx pattern, marking at least two rows of drilling positions; then use a down-the-hole drill to drill holes sequentially according to the design inclination angle and depth. S5. Pressure grouting pile formation: Lower the steel component (501) into the hole, and perform pressure grouting from the bottom of the hole upward through the pre-embedded grouting pipe, and inject cement mortar (502) until the borehole is filled, forming a cast-in-place pile (5) that is tightly bonded to the surrounding rock and soil. S6. Pile top connection: First, a connecting beam (601) is erected between the pile heads exposed at the borehole of each cast-in-place pile (6) to connect all the pile tops into an integral grid. Then, connecting steel bars (602) are arranged longitudinally and laterally on the connecting beam (601) according to the design spacing and fixed. Finally, fine stone concrete (603) is poured integrally on the frame composed of the connecting beam (601) and the steel bars (602) to form a reinforced concrete pier that consolidates the top of the micro pile group into one.

9. The method of claim 8, wherein The cross-section of the drainage ditch (1) in step S1 is an inverted trapezoid.

10. The method of claim 8, wherein The depth of the drainage hole (2) in step S2 is 40-60m.

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