Offshore photovoltaic socketed pile and construction method thereof

Abstract

The invention relates to an offshore photovoltaic socketed pile and a construction method thereof, and is suitable for the technical field of offshore photovoltaic power generation. According to the technical scheme, the socketed pile comprises a drill hole located in the surface of a rock stratum, and the diameter of the drill hole is larger than the outer diameter D of a steel pipe pile; the concrete is poured into the drill hole in the surface of the rock stratum and exceeds the outer diameter D of the steel pipe pile by one time on the surface of the rock stratum, an over-pouring section is formed above the rock surface, and the distance from the edge of the over-pouring section to the axis of the drill hole is larger than the radius of the steel pipe pile; the steel pipe piles are inserted into drill holes in the surface of the rock stratum and are combined with the rock stratum into a whole through the concrete; the concrete is doped with an expanding agent, and the expansion rate of the concrete is controlled between 0.2 per mill and 0.5 per mill. The steel pipe pile is inserted into the drill hole in the surface of the rock stratum, the steel pipe pile and the rock stratum are combined into a whole through concrete, the pile end is effectively embedded in the rock stratum, the embedding effect of the rock stratum is fully played, and the steel pipe pile is reasonable in structural stress, safe and reliable.

Description

Technical Field

[0001] The present invention relates to a rock-embedded pile for offshore photovoltaic power generation and a construction method thereof, and is applicable to the technical field of offshore photovoltaic power generation. Background Art

[0002] Offshore photovoltaic power generation systems require the construction of offshore photovoltaic platforms. Steel pipe piles are typically used for their foundations, and they must withstand the forces of the upper platform, waves, and currents. In some coastal areas of my country, such as those in Shandong, Zhejiang, Fujian, Guangxi, and Hainan, the rock formations are often shallow, requiring the pile foundations to be embedded in the rock, forming rock-embedded piles.

[0003] Unlike traditional pile foundations, which primarily resist vertical compression and pullout, offshore photovoltaic platforms are primarily designed to withstand horizontal forces and the resulting bending moments due to the unique forces acting on them. Controlling factors in offshore photovoltaic pile foundation design include: first, soil damage surrounding the pile under horizontal forces, manifesting as excessive horizontal deformation of the pile, causing significant tilt or even collapse; and second, large bending moments generated by horizontal forces, resulting in bending damage to the pile, manifesting as buckling or even fracture. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in view of the above-mentioned problems, a rock-embedded pile for offshore photovoltaics and a construction method thereof are provided.

[0005] The technical solution adopted by the present invention is: a rock-embedded pile for offshore photovoltaics, comprising: A borehole is located on the rock surface, and the diameter of the borehole is larger than the outer diameter D of the steel pipe pile; Concrete is poured into the drilled hole on the rock surface and exceeds the rock surface by one times the outer diameter D of the steel pipe pile, forming an over-filling section above the rock surface. The distance from the edge of the over-filling section to the axis of the drilled hole is greater than the radius of the steel pipe pile. The steel pipe pile is inserted into a drilled hole on the surface of the rock layer and is integrated with the rock layer through the concrete; The concrete is added with an expansion agent, and the expansion rate of the concrete is controlled between 0.2‰ and 0.5‰.

[0006] The diameter of the drill hole is 0.2-0.4 m larger than the outer diameter of the steel pipe pile, and the drilling depth is 2-5D.

[0007] The bottom of the drill hole has an over-drill section and is compacted by concrete pouring.

[0008] The steel pipe pile is composed of a rock section, a soil section, a variable diameter section and an upper straight section from bottom to top; Among them, the outer diameter of the rock section is D, and it corresponds to the rock layer; the outer diameter of the soil section is D, and it corresponds to the soil layer; the outer diameter of the variable diameter section gradually decreases from bottom to top, the outer diameter of the lower end of the variable diameter section is D, and the diameter of the upper end is d, d<D; the outer diameter of the upper straight section is d.

[0009] The wall thickness of the rock mass section gradually becomes thicker from bottom to top; the wall thickness of the soil mass section gradually becomes thinner from bottom to top; the wall thickness of the variable diameter section remains unchanged; and the wall thickness of the upper straight section gradually becomes thinner from bottom to top.

[0010] A construction method for the rock-socketed piles comprises: Sink the casing to the surface of the rock layer, and the height of the casing is greater than the thickness of the soil layer above the rock layer; Drilling holes on the rock surface through casing; Pour concrete into the drilled hole, with the pouring height exceeding the rock layer surface by one times the outer diameter D of the steel pipe pile; Remove the casing before the concrete begins to set; Before the concrete begins to set, insert steel pipe piles into the borehole and vibrate the piles to the designed elevation.

[0011] The beneficial effects of the present invention are as follows: the present invention inserts the steel pipe pile into the drilled hole on the surface of the rock layer, and combines the steel pipe pile and the rock layer into a whole through concrete, effectively embeds the pile end in the rock layer, gives full play to the embedding effect of the rock layer, and its structure is reasonably stressed, safe and reliable.

[0012] The bending moment on the steel pipe pile body is greatest at the bottom of the soil layer and the top of the rock layer. This invention overfills the pile with concrete to a height of approximately one pile diameter. After the steel pipe pile is driven into place, a concrete overfill section with a height of one pile diameter is formed above the rock surface. After the concrete solidifies, the lower end of the concrete in the overfilled section is located at the lower end of the steel pipe pile, while the upper end is higher than the point where the steel pipe pile body is subjected to the greatest bending moment. The concrete in the pile and the pile form an integral whole, allowing the pile and concrete to share the bending moment, creating a steel pipe concrete effect and improving the bending bearing capacity of the pile body. The concrete outside the overfilled section integrates with the concrete outside the pile in the drilled hole and forms an integral whole with the surrounding soil, improving the horizontal bearing capacity of the surrounding soil and reducing the horizontal deformation of the pile.

[0013] The expansion rate of concrete in the present invention is controlled between 0.2‰ and 0.5‰, so that after the concrete is solidified, it is in close contact with the pile body and the rock wall, so that the concrete, pile and rock mass are combined into an integral force. Too small an expansion rate cannot effectively make the concrete, pile body and rock wall in close contact, and too large an expansion rate may cause excessive initial stress on the pile body. After the present invention adopts micro-expansive concrete pouring, the pile and the concrete in the pile are in close contact, and cracks, disengagement and the like will not occur, so that the pile and concrete share the bending moment, forming the effect of steel tube concrete, and the concrete in the pile can effectively resist the buckling of the pile body, improve the bending bearing capacity of the pile, so that the lower section of the pile foundation rock mass section can reduce the pile thickness and reduce the amount of steel used.

[0014] The application adopts a construction process of drilling first, pouring concrete second and inserting pile third, cooperates with the concrete pouring height exceeding the rock surface by one diameter D of the steel pipe pile and the expansion rate of the concrete being controlled between 0.2‰ and 0.5‰, and has the advantages of fast construction, less construction process, saving of construction equipment and saving of construction cost; the surrounding soil of the constructed rock-socketed pile has high horizontal bearing capacity, reducing the horizontal deformation of the pile; the pile and the concrete jointly bear the bending moment, forming the effect of the steel pipe concrete, and the concrete in the pile can effectively resist the buckling of the pile body, improving the bending bearing capacity of the pile. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Fig. 1 is a schematic diagram of the state of the rock-socketed pile for offshore photovoltaic in the embodiment after pile sinking.

[0016] Figure 2 Fig. 2 is a schematic diagram of the sinking of the casing in the embodiment.

[0017] Figure 3 Fig. 3 is a schematic diagram of the drilling in the casing in the embodiment.

[0018] Figure 4 Fig. 4 is a schematic diagram of the pouring of concrete in the embodiment.

[0019] Figure 5 Fig. 5 is a schematic diagram of the state of the casing after removal in the embodiment.

[0020] 1, casing; 2, full-rotation drilling equipment; 3, concrete; 31, concrete pouring pipe; 4, steel pipe pile; 41, rock body section; 42, soil section; 43, variable diameter section; 44, upper straight section. DETAILED DESCRIPTION

[0021] As shown in the figure, the embodiment is a rock-socketed pile for offshore photovoltaic, a drill hole is arranged on the upper surface of the rock layer, the drill hole diameter is 0.2-0.4 m larger than the outer diameter D of the steel pipe pile, and the drill hole depth is slightly greater than 2-5D. Figure 1 In the example, the drill hole on the surface of the rock layer is filled with concrete, and in addition to filling the holes in the rock body with concrete, a height of about one diameter of the steel pipe pile is poured upwards, forming an over-pouring section above the rock surface, and the distance from the edge of the over-pouring section to the drill hole axis is greater than 0.5D of the radius of the steel pipe pile. In the embodiment, the concrete is mixed with an expanding agent, and the expansion rate of the poured concrete is controlled between 0.2‰ and 0.5‰.

[0022] In the embodiment, the steel pipe pile is inserted into the drill hole on the surface of the rock layer, the depth of the steel pipe pile inserted into the rock layer is 2-5D, and the steel pipe pile is combined with the rock layer into a whole through the concrete in the drill hole and the concrete in the over-pouring section.

[0023]

[0024] ​In this embodiment, after the concrete has solidified, the steel pipe pile, concrete, and rock formation form a single unit, effectively embedding the pile end in the rock formation and fully utilizing the rock formation's embedding properties. This results in a structure with reasonable stress response and safety and reliability. Because of this clear and reliable embedding, the steel pipe pile does not need to be inserted too deeply into the rock formation; generally, only 2 to 5 depths are required to achieve complete embedment, saving on pile foundation space and drilling work.

[0025] In this example, micro-expansive concrete is used, with an expansion rate controlled between 0.2‰ and 0.5‰. This allows the concrete to adhere tightly to the pile and rock face after curing, allowing the concrete, pile, and rock mass to form a single, integrated unit under load. Excessively small expansion rates prevent effective adhesion of the concrete, pile, and rock face, while excessive expansion rates may cause excessive initial stress on the pile. After pouring micro-expansive concrete, the pile and the concrete within the pile adhere tightly, preventing cracks or separation. This allows the pile and concrete to share the bending moment, creating a concrete-filled steel tube effect. The concrete within the pile effectively resists buckling, improving the pile's flexural bearing capacity. Therefore, the pile thickness and steel consumption can be reduced in the lower rock section of the pile foundation.

[0026] The bending moment on the pile is greatest at the bottom of the soil layer and the top of the rock layer. In this embodiment, concrete is overfilled to a height of approximately one-fold the pile diameter. The distance from the edge of the overfilled section to the drill axis is greater than 0.5D of the steel pipe pile radius. This ensures that concrete is present both inside and outside the overfilled section after the pile is driven. The concrete inside the overfilled section integrates with the pile, allowing the pile and concrete to share the bending moment, creating a concrete-filled steel tube effect and improving the pile's bending bearing capacity. The concrete outside the pile integrates with the surrounding soil, increasing the soil's horizontal bearing capacity and reducing horizontal deformation of the pile.

[0027] The construction method of rock-embedded piles for offshore photovoltaic systems in this embodiment specifically includes the following steps: S100, sink the casing to the rock surface ( Figure 2 ), the casing height is greater than the thickness of the soil layer above the rock layer, and the inner diameter of the casing is 10~20cm larger than the borehole diameter; S200, install a full-rotation drilling device in the casing. The outer diameter of the drilling rig is 10~20cm smaller than the inner diameter of the casing. Drill holes on the rock surface using the full-rotation drilling device ( Figure 3 ), using casing to achieve wall protection and auxiliary mucking, the diameter of the drill hole is 10~20cm smaller than the inner diameter of the casing; S300, after drilling and deburring, insert the concrete pouring pipe to the bottom of the hole, and pour concrete into the casing inside the hole from the bottom up. The poured concrete surface is about twice the pile diameter D higher than the rock surface ( Figure 4 ); S400, remove the casing before the concrete begins to set ( Figure 5 ), use the hydraulic clamp of the vibratory hammer to clamp the top of the casing, and pull out the casing under the action of the vibratory hammer; S500. Before the concrete begins to set, insert the steel pipe pile into the drill hole, clamp the top of the steel pipe pile with the hydraulic clamp of the vibratory hammer, and sink the steel pipe pile to the designed elevation under the action of the vibratory hammer.

[0028] In this embodiment, a retarder is added to the concrete to control the initial setting time of the concrete to 5 to 10 hours. By slowing down the initial setting time of the concrete, time is reserved for the construction of casing removal and pile insertion after the concrete is poured.

[0029] In this embodiment, the casing is removed after pouring concrete and before inserting piles. When pouring concrete, the casing is still protected by the casing to prevent the hole from collapsing and forming a pouring failure. The casing is pulled out before inserting piles because the concrete has not yet initially set and the casing can be easily pulled out. If the casing is pulled out after the piles are sunk, it will be difficult to pull out the casing because the limiting device of the engineering pile during pile sinking is smaller than the diameter of the casing and interferes with the casing. Secondly, the engineering quantity has been accurately positioned at this time. The vibration and interference when the vibrating hammer pulls out the casing are likely to affect the positioning of the engineering pile, resulting in engineering quantity positioning error or pile top elevation error.

[0030] In this example, the concrete pouring pipe is inserted to the bottom of the hole, and concrete is poured into the casing inside the hole from the bottom up. This can discharge the mud and water in the hole from the bottom up, so that the concrete remains poured densely, avoids excessive mud and seawater mixing into the concrete, and ensures the quality of the poured concrete.

[0031] In this embodiment, the piles are sunk before the initial setting of the concrete. After the concrete solidifies, the concrete, the piles and the rock mass form an integral load-bearing structure. No steel cage is needed, thus saving the engineering workload and construction procedures of the steel cage.

[0032] This embodiment uses a vibratory hammer for both casing extraction and pile sinking. This allows the same vibratory hammer to be used for both operations, eliminating time-consuming equipment changes and reducing the number of construction equipment needed. The vibratory hammer generates high-frequency vibrations in the pile or casing, liquefying the soil surrounding it, reducing soil friction and resistance to casing extraction and pile sinking. The high-frequency vibrations of the pile driven by the vibratory hammer displace aggregate within unset concrete, enabling smooth insertion of the steel pipe pile.

[0033] In some specific embodiments, the bottom of the borehole has an overdrilled section and is compacted with concrete. When drilling, after the borehole reaches the bottom of the steel pipe pile, it is overdrilled by 0.1-0.3m, and this overdrilled area is compacted with concrete.

[0034] Drilling depth is subject to measurement and construction errors. Therefore, this embodiment reserves 0.1 to 0.3 meters of overdrilling distance to adjust for this error, allowing the pile top to sink smoothly to the designed elevation. The overdrilled area is then compacted with concrete, which does not affect the bearing capacity of the pile tip.

[0035] In some specific embodiments, the steel pipe pile consists of a rock section, a soil section, a variable diameter section and an upper straight section from bottom to top, wherein the rock section is a constant diameter section with an outer diameter of D, corresponding to the rock layer; the soil section is a constant diameter section with an outer diameter of D, corresponding to the soil layer; the outer diameter of the variable diameter section gradually decreases from bottom to top, the outer diameter of the lower end of the variable diameter section is D, and the diameter of the upper end is d, d<D, the lower end of the variable diameter section is near the mud surface, and its variable diameter slope ratio is generally 3:1~10:1 on one side; the upper straight section is a constant diameter section with an outer diameter of d.

[0036] In this embodiment, the wall thickness of the rock section is variable, gradually becoming thicker from bottom to top, the wall thickness of the upper rock section is thicker, and the wall thickness of the lower rock section is thinner; the wall thickness of the soil section is variable, gradually becoming thinner from bottom to top, the wall thickness of the lower soil section is thicker, and the wall thickness of the upper soil section is thinner; the wall thickness of the variable diameter section remains unchanged; the wall thickness of the upper straight section is variable, gradually becoming thinner from bottom to top, the wall thickness of the lower upper straight section is thicker, and the wall thickness of the upper upper straight section is thinner.

[0037] In this embodiment, the steel pipe pile is extended to the bottom of the pile, and the bending moment is borne by the steel pipe pile throughout the whole process. The force is clearly received, and there is no need to place a steel cage, which saves the engineering workload and construction process of the steel cage.

[0038] In this example, the steel pipe piles are divided into four sections. The diameter and wall thickness of the steel pipe piles are set according to the different stress characteristics of the four sections, so as to give full play to the bending resistance of the steel pipe piles in each section and save steel.

[0039] In this embodiment, the rock and soil segments have the same diameter, the largest diameter of the entire pile. The upper rock and lower soil segments are where the pile experiences the greatest bending moment, and therefore have the largest diameters. These equal-diameter segments facilitate pile insertion within concrete and soil. The upper and lower rock segments experience the greatest bending moment, minimizing both upward and downward bending moments. Therefore, the wall thickness of the lower rock and upper soil segments can be reduced, saving steel.

[0040] In this example, a variable diameter section is provided above the mud surface. Because the bending moment continues to decrease above the mud surface, the pile diameter is reduced to further reduce steel usage. This reduction in diameter also reduces the forces acting on the pile from waves and currents, further reducing the bending moment in the pile. The upper straight section connects to the upper photovoltaic platform, so the diameter remains unchanged, but the wall thickness continues to decrease according to the bending characteristics. By adopting a method where the variable diameter steel pipe pile is subjected to bending throughout its entire length, the bending resistance of the pile body is fully utilized based on the load characteristics of the entire pile, minimizing steel usage.

Claims

1. A rock-embedded pile for offshore photovoltaics, characterized in that: include: A borehole is located on the rock surface, and the diameter of the borehole is larger than the outer diameter D of the steel pipe pile; Concrete is poured into the drilled hole on the rock surface and exceeds the rock surface by one times the outer diameter D of the steel pipe pile, forming an over-filling section above the rock surface. The distance from the edge of the over-filling section to the axis of the drilled hole is greater than the radius of the steel pipe pile. The steel pipe pile is inserted into a drilled hole on the surface of the rock layer and is integrated with the rock layer through the concrete; The concrete is added with an expansion agent, and the expansion rate of the concrete is controlled between 0.2‰ and 0.5‰.

2. The rock-socketed pile for offshore photovoltaics according to claim 1, characterized in that: The diameter of the drill hole is 0.2-0.4 m larger than the outer diameter of the steel pipe pile, and the drilling depth is 2-5D.

3. The rock-socketed pile for offshore photovoltaics according to claim 1 or 2, characterized in that: The bottom of the drill hole has an over-drill section and is compacted by concrete pouring.

4. The rock-socketed pile for offshore photovoltaics according to claim 1, characterized in that: The steel pipe pile is composed of a rock section, a soil section, a variable diameter section and an upper straight section from bottom to top; Among them, the outer diameter of the rock section is D, and it corresponds to the rock layer; the outer diameter of the soil section is D, and it corresponds to the soil layer; the outer diameter of the variable diameter section gradually decreases from bottom to top, the outer diameter of the lower end of the variable diameter section is D, and the diameter of the upper end is d, d<D; the outer diameter of the upper straight section is d.

5. The rock-socketed pile for offshore photovoltaics according to claim 4, characterized in that: The wall thickness of the rock mass section gradually becomes thicker from bottom to top; the wall thickness of the soil mass section gradually becomes thinner from bottom to top; the wall thickness of the variable diameter section remains unchanged; and the wall thickness of the upper straight section gradually becomes thinner from bottom to top.

6. A construction method for rock-socketed piles according to any one of claims 1 to 5, characterized in that: include: Sink the casing to the surface of the rock layer, and the height of the casing is greater than the thickness of the soil layer above the rock layer; Drilling holes on the rock surface through casing; Pour concrete into the drilled hole, with the pouring height exceeding the rock layer surface by one times the outer diameter D of the steel pipe pile; Remove the casing before the concrete begins to set; Before the concrete begins to set, insert steel pipe piles into the borehole and vibrate the piles to the designed elevation.

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