Cast-in-place pile structure and green construction method

Abstract

The invention discloses a cast-in-place pile structure and a green construction method, and relates to the technical field of cast-in-place pile construction, the cast-in-place pile structure comprises a pile body, a reinforcement cage and a grouting pipe, the pile body is poured by gradient functional concrete, the outer layer is a high-strength impervious layer, the interior is a toughness enhancement layer, and the outer layer and the inner layer achieve interface strengthening through a nanocrystalline transition layer; a graphene modified polymer protective coating is arranged on the periphery of the pile body, and the thickness of the graphene modified polymer protective coating is 500 micrometers. The pile comprises a pile body, a reinforcement cage and a grouting pipe, the pile body is poured through gradient functional concrete, the outer layer is a high-strength impervious layer, the inner layer is a toughness enhancing layer, and the outer layer and the inner layer achieve interface strengthening through a nanocrystalline transition layer; a graphene modified polymer protective coating is arranged on the periphery of the pile body, and the thickness of the graphene modified polymer protective coating is 500 micrometers. The green construction effects of low carbon, energy conservation and resource recycling are achieved through the step S2 of supercritical COmicrobubble concrete preparation, the step S7 of ground source heat pump auxiliary curing and the step of carbon sink concrete application.

Description

Technical Field

[0001] This invention relates to the field of cast-in-place pile construction technology, and in particular to a cast-in-place pile structure and a green construction method. Background Technology

[0002] Cast-in-place piles are piles made by drilling holes in place and then pouring in concrete or reinforced concrete. Due to their advantages such as no vibration during construction, no soil displacement, low noise, and suitability for use in densely built-up urban areas, cast-in-place piles are widely used in construction. Depending on the drilling process, cast-in-place piles can be divided into cast-in-place piles with dry drilling, cast-in-place piles with mud wall protection, and cast-in-place piles with manually excavated holes.

[0003] Traditional concrete piles have limited resistance to seepage and cracking, and are prone to cracking due to environmental erosion or temperature stress. The ordinary steel bars in the reinforcing cage have weak corrosion resistance. Traditional drilling processes have low verticality control accuracy, and mud slurry wall protection generates a large amount of polluting waste mud. The concrete curing cycle is long and the quality is unstable. At the same time, there is a lack of real-time monitoring methods, high construction energy consumption, and ineffective utilization of waste heat and waste residue. Therefore, it is necessary to design a cast-in-place pile structure and a green construction method to solve the above-mentioned problems. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: a cast-in-place pile structure, comprising a pile body, a reinforcing cage, and a grouting pipe, wherein the pile body is cast with gradient functional concrete, the outer layer is a high-strength impermeable layer, the inner layer is a toughness-enhancing layer, and the outer and inner layers are reinforced at the interface through a nanocrystalline transition layer; a graphene-modified polymer protective coating with a thickness of 500 μm is provided around the pile body. The reinforcing cage is made of carbon fiber-steel composite material, with a spiral graphene-based thermal conductive mesh on the outside, having a thermal conductivity of ≥500W / m*K. Microcapsules of bactericide are embedded in the mesh. A shape memory alloy stress ring is set at the top of the reinforcing cage, which automatically applies a pre-stress of 30MPa after the concrete hardens. The grouting pipe is made of shape memory alloy material, forming an expandable shape memory alloy umbrella-shaped load-bearing body at the pile end. The surface is distributed with biomimetic honeycomb grout outlet holes with a diameter of 1-3mm and a grout outlet uniformity deviation of ≤5%. A ring-shaped ultrasonic vibration device is added to the middle of the pile body, which generates a 20kHz high-frequency vibration through piezoelectric ceramic elements to promote slurry diffusion.

[0005] Preferably, the gradient functional concrete is formed by 3D printing layered casting technology, with the outer layer adopting an ultra-high strength micro-expansion concrete structure and the inner layer adopting a tough fiber concrete structure. The interface between the outer and inner layers is formed by chemical anchoring agent to form a micro-interlaced structure with a depth of ≥5mm. The carbon fiber-steel composite reinforcement is prepared by vacuum impregnation process, with a carbon fiber volume fraction of 30%, and is coated with an epoxy resin-based composite material; the spiral graphene-based thermal conductive mesh is prepared by chemical vapor deposition of graphene on the surface of a copper mesh, with a wire diameter of 0.5 mm and a spacing of 10 mm. The shape memory alloy stress ring is made of NiTi-based alloy. After activation at 60°C, it generates radial expansion stress, which is transferred to the reinforcing cage through a wedge-shaped anchoring system, so that the concrete at the top of the pile is in a pre-compressed state.

[0006] A green construction method for cast-in-place piles, applied to the aforementioned cast-in-place pile structure, includes the following construction steps: S1. Intelligent Site Planning and Geological Holographic Modeling: A three-dimensional site model is generated using UAV oblique photography and lidar scanning, and a geological holographic model is constructed by combining geophysical exploration technologies such as high-density resistivity method and Rayleigh wave exploration. By simulating the entire construction process of cast-in-place piles using BIM technology, the pile layout is optimized and the amount of earthwork excavation is reduced; modular precast pile head technology is adopted to prefabricate pile head components, including steel reinforcement anchoring systems and ultrasonic vibration devices, in the factory. S2. Preparation of supercritical CO2 microbubble concrete: Microbubble concrete is prepared using supercritical CO2 technology. CO2 is mixed with cement paste under a pressure of 6.5 MPa to form stable bubbles with a diameter of 10-50 μm. Adding nanoscale seed materials with a particle size of 50-100nm accelerates cement hydration; 3D-printed guide molds are used to control the layered pouring of gradient functional concrete, and the molds are made of biodegradable polymer materials. S3, Magnetic Levitation Guidance for Precise Hole Formation: The drilling rig is equipped with a magnetic levitation guidance system, which, through the cooperation of a ground magnetic field generator and a drill bit magnetic sensor, controls the verticality deviation of the hole formation to within 0.1%; The double-wall reverse circulation drilling technology is adopted, with flushing fluid delivered through the inner tube and drill cuttings discharged through the outer tube, achieving a drill cuttings recovery rate of ≥95%. During drilling, the changes in formation resistance are monitored in real time, and drilling parameters are automatically adjusted through AI algorithms to adapt to formations with uneven hardness. S4. Vacuum-assisted lowering of the reinforcing cage: A vacuum adsorption device is installed at the orifice to accelerate the sinking of the reinforcing cage through negative pressure. An intelligent stress monitoring system is used to monitor the stress distribution of the steel cage in real time during the lowering process, and the lowering speed is automatically adjusted when the local stress exceeds the threshold. After the lowering is completed, a zinc-based protective layer with a thickness of 20-50μm is formed on the surface of the steel cage using electrochemical deposition technology; S5. Deployment and activation of shape memory alloy grouting pipe: The shape memory alloy grouting pipe, which shrinks at room temperature, is lowered along with the steel cage. After reaching the bottom of the hole, it is activated by injecting 65℃ hot water to expand and form an umbrella-shaped structure. Ultrasonic-assisted activation technology is used to accelerate the phase transformation process of shape memory alloys by generating 20kHz high-frequency vibration through a ring ultrasonic vibration device. High-performance cement slurry containing nano-silica powder with a particle size of 10-30nm and micro-expansion agent is injected. The water-cement ratio of the slurry is 0.4 and the fluidity is 300mm. S6, Integration of 3D Printed Pile Top Reinforcement Structure and Intelligent Monitoring System: The reinforcement structure is directly printed on the pile top using concrete 3D printing technology. 15% of recycled aggregate from construction waste is added to the printing material. At the same time, a distributed fiber optic grating sensor array, a nanowire humidity sensor and a wireless energy harvesting module are integrated. The sensor transmits signals using optical time-domain reflectometry, and its monitoring range covers the entire pile body; a solar power module is installed at the top of the pile, with an output power of ≥10W; S7. Ground source heat pump assisted curing and carbon sink concrete application: A ground source heat pump circulation pipeline is buried around the pile body to use shallow geothermal energy to regulate the curing temperature of concrete, and the curing temperature fluctuation is controlled within ±2℃. Carbon sequestration concrete technology is adopted, incorporating 20% ​​carbonation curing industrial waste into the concrete. During the curing process, CO2 is absorbed to form calcium carbonate, and the amount of fixed CO2 per cubic meter of concrete is ≥100kg. After maintenance is completed, data from the entire construction process will be recorded using blockchain technology.

[0007] Preferably, in the preparation step of the S2 supercritical CO2 microbubble concrete, a biodegradable polymer thickener is added to improve the stability of the CO2 bubbles; Ground source heat pump technology is used to provide a heat source for shape memory alloy grouting pipes, reducing conventional energy consumption; Using nanoscale anti-dispersion agents to improve the anti-dispersion properties of underwater concrete.

[0008] Preferably, in the S3 magnetic levitation guided precision drilling step, combined with real-time detection by ground-penetrating radar, underground obstacles can be identified in advance and the drilling path can be automatically adjusted.

[0009] Preferably, in the S4 vacuum-assisted lowering step of the reinforcing cage, the stability of the borehole wall is monitored in real time by an acoustic monitoring system, and the lowering speed is automatically adjusted when an abnormal vibration signal occurs.

[0010] Preferably, in the S5 shape memory alloy grouting pipe activation step, the injected high-performance cement grout containing nano-silica powder and micro-expansion agent has a self-healing function. When micro-cracks appear in the pile body, the nano-silica powder will react with the cement hydration products to generate an expansive substance to fill the cracks.

[0011] In summary, this invention provides a cast-in-place pile structure and a green construction method, which have the following beneficial effects: 1. By using graded functional concrete pile body, graphene modified polymer protective coating and shape memory alloy stress ring, the seepage resistance, crack resistance and bearing capacity of cast-in-place piles are improved; the outer layer of graded functional concrete is seepage-resistant, the inner layer is tough and the nanocrystalline transition layer is combined with 500μm graphene protective coating to form a multi-layer seepage barrier, improve the seepage resistance level and effectively resist groundwater erosion; the shape memory alloy stress ring applies 30MPa pre-stress, which improves the crack resistance of the pile top concrete and improves the overall bearing capacity.

[0012] 2. Through the S2 supercritical CO2 microbubble concrete preparation step, the S7 ground source heat pump assisted curing step, and the carbon sink concrete application step, green construction effects of low carbon, energy saving, and resource recycling were achieved; through the S3 magnetic levitation guided precise hole forming step, the S4 vacuum assisted rebar cage lowering step, and the S5 shape memory alloy grouting pipe deployment and activation step, the effects of precise and efficient construction and reduced energy consumption and costs were achieved; through the S1 intelligent site planning and geological holographic modeling step, the S6 3D printed pile top reinforcement structure and intelligent monitoring system integration step, and the S7 blockchain data recording step, the effects of intelligent construction process and quality traceability were achieved. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the process architecture of a cast-in-place pile structure and green construction method according to the present invention. Detailed Implementation

[0014] The following is in conjunction with the appendix Figure 1 This application will be described in further detail below.

[0015] Example: This invention provides a technical solution: a cast-in-place pile structure, comprising a pile body, a reinforcing cage, and a grouting pipe. The pile body is constructed using gradient functional concrete, with an outer high-strength impermeable layer and an inner toughness-enhancing layer. The outer and inner layers are reinforced at the interface through a nanocrystalline transition layer. A graphene-modified polymer protective coating with a thickness of 500 μm is applied to the periphery of the pile body, giving it excellent impermeability and toughness. Simultaneously, the high-strength impermeable layer effectively resists external liquid penetration, protecting the internal structure. The toughness-enhancing layer improves the pile body's resistance to deformation and cracking, while the nanocrystalline transition layer enhances the bonding strength between the two layers, significantly improving the overall performance of the pile body. The reinforcing cage uses carbon fiber-steel composite material and is surrounded by a spiral graphene-based thermal conductive mesh with a thermal conductivity ≥500W / m*K. Microcapsules of slow-release bactericide are embedded in the mesh. A shape memory alloy stress ring is set at the top of the reinforcing cage, which automatically applies a 30MPa pre-stress after the concrete hardens, improving the mechanical properties and durability of the reinforcing cage. The spiral graphene-based thermal conductive mesh can effectively conduct heat, which helps to achieve uniform temperature distribution during the concrete curing process and avoid cracks caused by temperature differences. The microcapsule slow-release bactericide can inhibit the growth of microorganisms for a long time and prevent the reinforcing cage from being corroded. The grouting pipe is made of shape memory alloy material, forming an expandable shape memory alloy umbrella-shaped load-bearing body at the pile end. The surface is distributed with biomimetic honeycomb grout outlet holes with a diameter of 1-3mm and a grout outlet uniformity deviation of ≤5%. After the shape memory alloy grouting pipe reaches the bottom of the hole, it expands to form an umbrella-shaped structure, which increases the grouting range and improves the reinforcement effect of the soil at the pile end. The biomimetic honeycomb grout outlet hole design ensures the uniformity of grout outlet, allowing the grout to fill the voids at the pile end more evenly, enhancing the bonding force between the pile end and the soil, and improving the overall stability of the cast-in-place pile. A ring-shaped ultrasonic vibration device is added to the middle of the pile body. The device generates a 20kHz high-frequency vibration through a piezoelectric ceramic element to promote the diffusion of the grout. The high-frequency vibration generated by the ring-shaped ultrasonic vibration device can effectively reduce the viscosity of the grout and enhance its fluidity, thereby allowing it to diffuse more fully into the pores of the soil around the pile, improving the bond strength between the pile body and the soil, and enhancing the bearing capacity of the cast-in-place pile.

[0016] Gradient functional concrete is formed using 3D printing layered casting technology. The outer layer adopts an ultra-high strength micro-expansion concrete structure, while the inner layer adopts a tough fiber concrete structure. The interface between the outer and inner layers is formed with a chemical anchoring agent to create a micro-interlaced structure with a depth of ≥5mm. The 3D printing layered casting technology ensures the precise forming of each layer of the gradient functional concrete structure. The ultra-high strength micro-expansion concrete structure further enhances the impermeability and compressive strength of the outer layer, while the tough fiber concrete structure improves the internal toughness. The micro-interlaced structure formed by the chemical anchoring agent greatly improves the bond strength between the two layers, ensuring the overall synergistic performance of the pile body. The carbon fiber-steel composite reinforcement is prepared using a vacuum impregnation process, with a carbon fiber volume fraction of 30%, and is coated with an epoxy resin-based composite material. The spiral graphene-based thermal conductive mesh is prepared by chemical vapor deposition (CVD) to deposit graphene onto the surface of a copper mesh. The mesh wire diameter is 0.5 mm and the spacing is 10 mm. The vacuum impregnation process ensures thorough composite bonding between the carbon fiber and the steel reinforcement, guaranteeing the stable performance of the composite reinforcement. The 30% carbon fiber volume fraction optimizes cost while maintaining strength. The spiral graphene-based thermal conductive mesh prepared by CVD exhibits excellent thermal conductivity and structural stability. The rational design of the mesh wire diameter and spacing ensures effective thermal conductivity and sterilization functions. The shape memory alloy stress ring is made of NiTi-based alloy. After activation at 60℃, it generates radial expansion stress, which is transferred to the reinforcing cage through a wedge-shaped anchoring system, so that the concrete at the top of the pile is in a pre-compressed state. The shape memory effect of NiTi-based alloy is stable and reliable, and the activation temperature of 60℃ is easy to achieve during construction. The wedge-shaped anchoring system ensures that the stress can be efficiently transferred to the reinforcing cage, so that the concrete at the top of the pile obtains stable pre-compressed stress and improves the structural performance of the pile.

[0017] A green construction method for cast-in-place piles, applied to the aforementioned cast-in-place pile structure, includes the following construction steps: S1. Intelligent Site Planning and Geological Holographic Modeling: Using UAV oblique photography and lidar scanning to generate a 3D site model, combined with geophysical exploration technologies such as high-density resistivity method and Rayleigh wave exploration, a geological holographic model is constructed. Through these advanced technologies, site and geological information can be obtained quickly and accurately, providing comprehensive and accurate data support for the formulation of subsequent construction plans, optimizing the construction process, reducing construction risks, and improving construction efficiency. By simulating the entire process of cast-in-place pile construction using BIM technology, the pile layout can be optimized, reducing the amount of earthwork excavation. Modular precast pile head technology is adopted, in which pile head components including a steel reinforcement anchoring system and an ultrasonic vibration device are prefabricated in the factory. BIM simulation can identify and optimize potential problems during construction in advance, reducing unnecessary earthwork excavation and minimizing the impact on the surrounding environment. Modular precast pile head technology improves the manufacturing precision and quality of pile heads, shortens on-site construction time, increases construction efficiency, and facilitates quality control. S2. Preparation of Supercritical CO2 Microbubble Concrete: Supercritical CO2 technology is used to prepare microbubble concrete. CO2 is mixed with cement paste under a pressure of 6.5MPa to form stable bubbles with a diameter of 10-50μm. Supercritical CO2 microbubble concrete has the advantages of being lightweight, high-strength, and heat-insulating. The stable microbubbles distributed in the concrete can reduce the self-weight of the concrete, improve its thermal insulation performance, and at the same time improve the workability of the concrete, making it easier to carry out construction. Adding nano-sized seed materials with a particle size of 50-100nm accelerates cement hydration. Nano-sized seed materials can significantly accelerate the cement hydration reaction rate, shorten the setting time of concrete, improve early strength, and enable cast-in-place piles to enter subsequent construction processes more quickly, thus speeding up the construction progress. The use of 3D-printed guide molds to control the layered pouring of gradient functional concrete, with the molds made of biodegradable polymer materials, ensures the accuracy and quality of each layer of gradient functional concrete pouring. The biodegradable polymer materials can naturally degrade after pouring, reducing the generation of construction waste, which is in line with the concept of green construction and reduces environmental pollution. S3. Magnetic Levitation Guidance for Precise Hole Formation: The drilling rig is equipped with a magnetic levitation guidance system. Through the cooperation of a ground magnetic field generator and a drill bit magnetic sensor, the verticality deviation of the hole is controlled within 0.1%. The magnetic levitation guidance system greatly improves the verticality accuracy of the hole, reduces pile quality problems caused by hole inclination, improves the bearing capacity and stability of the cast-in-place pile, and reduces the cost and time of correction during construction. The double-wall reverse circulation drilling technology uses an inner pipe to transport flushing fluid and an outer pipe to discharge drill cuttings, achieving a drill cuttings recovery rate of ≥95%. This technology efficiently discharges and recovers drill cuttings, reducing pollution to the construction site and surrounding environment, while also improving drilling efficiency and reducing energy consumption during the drilling process. During the drilling process, the changes in formation resistance are monitored in real time, and drilling parameters are automatically adjusted through AI algorithms to adapt to formations with uneven hardness. Real-time monitoring and AI algorithm adjustment enable the drilling rig to optimize drilling parameters in a timely manner according to the actual formation conditions, thereby improving drilling efficiency, reducing drill bit wear, ensuring hole quality, and reducing construction costs. S4. Vacuum-assisted lowering of the reinforcing cage: A vacuum adsorption device is installed at the borehole opening. The negative pressure accelerates the sinking of the reinforcing cage. Vacuum-assisted lowering of the reinforcing cage can significantly improve the lowering speed, shorten the construction time, and at the same time reduce the friction between the reinforcing cage and the borehole wall during the sinking process, reduce the risk of deformation of the reinforcing cage, and ensure the installation quality of the reinforcing cage. An intelligent stress monitoring system is used to monitor the stress distribution of the steel cage in real time during the lowering process. When the local stress exceeds the threshold, the lowering speed is automatically adjusted. The intelligent stress monitoring system can detect abnormal stress conditions in the lowering process of the steel cage in a timely manner and automatically adjust the lowering speed to avoid damage to the steel cage due to excessive stress, thus ensuring construction safety and the integrity of the steel cage. After the lowering is completed, a zinc-based protective layer with a thickness of 20-50μm is formed on the surface of the reinforcing cage using electrochemical deposition technology. The zinc-based protective layer can effectively protect the reinforcing cage from corrosion, extend its service life, and improve the durability of the cast-in-place pile. At the same time, the electrochemical deposition technology is simple to operate and has a relatively low cost. S5. Deployment and activation of shape memory alloy grouting pipe: The shape memory alloy grouting pipe, which shrinks at room temperature, is lowered with the steel cage. After reaching the bottom of the hole, it is activated by injecting 65°C hot water, which causes it to expand and form an umbrella-shaped structure. The automatic expansion of the grouting pipe at the bottom of the hole is achieved by utilizing the characteristics of shape memory alloy, which improves construction efficiency and ensures the effective working state of the grouting pipe at the pile end. The ultrasonic-assisted activation technology uses a ring-shaped ultrasonic vibration device to generate 20kHz high-frequency vibrations to accelerate the phase transformation process of shape memory alloys. This technology can accelerate the phase transformation of shape memory alloys, allowing them to expand to the designed shape more quickly, shortening construction time, improving construction efficiency, and ensuring that the performance of shape memory alloys is fully utilized. High-performance cement grout containing nano-silica powder with a particle size of 10-30nm and micro-expansion agent is injected. The water-cement ratio of the grout is 0.4, and the fluidity is 300mm. Nano-silica powder and micro-expansion agent can effectively improve the performance of cement grout. Nano-silica powder can enhance the strength and durability of cement grout, while micro-expansion agent can compensate for the shrinkage during the hardening process of cement grout and prevent cracks from forming. The good water-cement ratio and fluidity ensure the construction performance and filling effect of cement grout. S6. Integration of 3D-printed pile top reinforcement structure and intelligent monitoring system: A reinforcement structure is directly printed on the pile top using concrete 3D printing technology. The printing material incorporates 15% recycled construction waste aggregate. Simultaneously, a distributed fiber optic grating sensor array, a nanowire humidity sensor, and a wireless energy harvesting module are integrated. The 3D-printed pile top reinforcement structure improves the strength and stability of the pile top. The inclusion of recycled construction waste aggregate enables resource recycling, reduces the use of new materials, and lowers costs and environmental impact. The intelligent monitoring system can monitor parameters such as stress, strain, and humidity in the pile body in real time, providing data support for the long-term safe operation of the cast-in-place pile. The sensor transmits signals using optical time domain reflectance technology, and the monitoring range covers the entire pile body. A solar power module is installed at the top of the pile, with an output power of ≥10W. Optical time domain reflectance technology ensures the accuracy and stability of sensor signal transmission, and the solar power module provides sustainable energy for the intelligent monitoring system, reducing dependence on external power sources and meeting the requirements of green construction and energy conservation and environmental protection. S7. Ground source heat pump assisted curing and carbon sink concrete application: A ground source heat pump circulation pipeline is buried around the pile body to regulate the curing temperature of concrete using shallow geothermal energy. The curing temperature fluctuation is controlled within ±2℃. Ground source heat pump assisted curing can accurately control the curing temperature of concrete, providing a suitable temperature environment for the hardening of concrete, improving the strength and durability of concrete. At the same time, the use of shallow geothermal energy achieves efficient energy utilization and reduces energy consumption. Carbon sequestration concrete technology incorporates 20% carbonation curing industrial waste into concrete. During the curing process, it absorbs CO2 to form calcium carbonate, fixing ≥100kg of CO2 per cubic meter of concrete. This technology achieves the resource utilization of industrial waste and absorbs carbon dioxide during the curing process, resulting in significant environmental benefits and reduced carbon emissions. After maintenance is completed, data from the entire construction process is recorded using blockchain technology. This technology ensures the authenticity, immutability, and traceability of the construction data, providing reliable data for the quality assessment, maintenance management, and subsequent research of the cast-in-place piles.

[0018] In the preparation process of S2 supercritical CO2 microbubble concrete, the addition of a biodegradable polymer thickener improves the stability of CO2 bubbles. The biodegradable polymer thickener further enhances the stability of CO2 bubbles in cement paste, ensuring uniform performance of microbubble concrete, improving its quality and durability. At the same time, the biodegradable properties meet the requirements of green environmental protection. The use of ground source heat pump technology to provide heat for shape memory alloy grouting pipes reduces conventional energy consumption. Ground source heat pump technology utilizes shallow geothermal energy to provide the heat required for the activation of shape memory alloy grouting pipes, reducing dependence on traditional fossil energy, reducing energy consumption and carbon emissions, and achieving clean energy utilization and sustainable development. The use of nano-level anti-dispersion agents improves the anti-dispersion performance of underwater concrete. Nano-level anti-dispersion agents effectively enhance the anti-dispersion ability of underwater concrete during the pouring process, ensuring that the concrete can be uniformly formed in the underwater environment, improving the underwater construction quality of cast-in-place piles, and reducing quality problems such as concrete segregation.

[0019] In the S3 magnetic levitation-guided precision drilling process, combined with real-time detection by ground-penetrating radar, underground obstacles can be identified in advance and the drilling path can be automatically adjusted. The combination of ground-penetrating radar and magnetic levitation guidance system enables the drilling rig to detect underground obstacles in advance and automatically adjust the drilling path, avoiding construction accidents and equipment damage caused by collisions with obstacles, improving construction efficiency and safety, and ensuring smooth drilling.

[0020] During the S4 vacuum-assisted rebar cage lowering process, the stability of the borehole wall is monitored in real time through an acoustic monitoring system. When abnormal vibration signals occur, the lowering speed is automatically adjusted. The acoustic monitoring system can monitor the stability of the borehole wall in real time, promptly detect potential borehole wall collapse risks, and automatically adjust the lowering speed of the rebar cage to ensure construction safety and avoid damage to the rebar cage and construction delays caused by borehole wall collapse.

[0021] In the activation step of the S5 shape memory alloy grouting pipe, the high-performance cement grout containing nano-silica powder and micro-expansion agent has a self-healing function. When micro-cracks appear in the pile body, the nano-silica powder reacts with the cement hydration products to generate an expansive substance that fills the cracks, effectively improving the durability and safety of the cast-in-place pile. It automatically repairs the micro-cracks when they appear in the pile body, preventing the cracks from expanding further and ensuring the integrity and load-bearing capacity of the pile structure.

[0022] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A cast-in-place pile structure, comprising a pile body, a reinforcing cage, and a grouting pipe, characterized in that: The pile body is constructed using gradient functional concrete, with an outer high-strength impermeable layer and an inner toughness-enhancing layer. The outer and inner layers are reinforced at the interface through a nanocrystalline transition layer. A graphene-modified polymer protective coating with a thickness of 500 μm is applied to the periphery of the pile body. The reinforcing cage is made of carbon fiber-steel composite material, with a spiral graphene-based thermal conductive mesh on the outside, having a thermal conductivity of ≥500W / m*K. Microcapsules of bactericide are embedded in the mesh. A shape memory alloy stress ring is set at the top of the reinforcing cage, which automatically applies a pre-stress of 30MPa after the concrete hardens. The grouting pipe is made of shape memory alloy material, forming an expandable shape memory alloy umbrella-shaped load-bearing body at the pile end. The surface is distributed with biomimetic honeycomb grout outlet holes with a diameter of 1-3mm and a grout outlet uniformity deviation of ≤5%. A ring-shaped ultrasonic vibration device is added to the middle of the pile body, which generates a 20kHz high-frequency vibration through piezoelectric ceramic elements to promote slurry diffusion.

2. The cast-in-place pile structure according to claim 1, characterized in that: The gradient functional concrete is formed by 3D printing layered casting technology. The outer layer adopts an ultra-high strength micro-expansion concrete structure, and the inner layer adopts a tough fiber concrete structure. The interface between the outer and inner layers forms a micro-interlaced structure with a depth of ≥5mm through a chemical anchoring agent. The carbon fiber-steel composite reinforcement is prepared by vacuum impregnation process, with a carbon fiber volume fraction of 30%, and is coated with an epoxy resin-based composite material; the spiral graphene-based thermal conductive mesh is prepared by chemical vapor deposition of graphene on the surface of a copper mesh, with a wire diameter of 0.5 mm and a spacing of 10 mm. The shape memory alloy stress ring is made of NiTi-based alloy. After activation at 60°C, it generates radial expansion stress, which is transferred to the reinforcing cage through a wedge-shaped anchoring system, so that the concrete at the top of the pile is in a pre-compressed state.

3. A green construction method for cast-in-place piles, applied to a cast-in-place pile structure as described in any one of claims 1-2, characterized in that: The construction steps include the following: S1. Intelligent Site Planning and Geological Holographic Modeling: A three-dimensional site model is generated using UAV oblique photography and lidar scanning, and a geological holographic model is constructed by combining geophysical exploration technologies such as high-density resistivity method and Rayleigh wave exploration. By simulating the entire construction process of cast-in-place piles using BIM technology, the pile layout is optimized and the amount of earthwork excavation is reduced; modular precast pile head technology is adopted to prefabricate pile head components, including steel reinforcement anchoring systems and ultrasonic vibration devices, in the factory. S2. Preparation of supercritical CO2 microbubble concrete: Microbubble concrete is prepared using supercritical CO2 technology. CO2 is mixed with cement paste under a pressure of 6.5 MPa to form stable bubbles with a diameter of 10-50 μm. Adding nanoscale seed materials with a particle size of 50-100nm accelerates cement hydration; 3D-printed guide molds are used to control the layered pouring of gradient functional concrete, and the molds are made of biodegradable polymer materials. S3, Magnetic Levitation Guidance for Precise Hole Formation: The drilling rig is equipped with a magnetic levitation guidance system, which, through the cooperation of a ground magnetic field generator and a drill bit magnetic sensor, controls the verticality deviation of the hole formation to within 0.1%; The double-wall reverse circulation drilling technology is adopted, with flushing fluid delivered through the inner tube and drill cuttings discharged through the outer tube, achieving a drill cuttings recovery rate of ≥95%. During drilling, the changes in formation resistance are monitored in real time, and drilling parameters are automatically adjusted through AI algorithms to adapt to formations with uneven hardness. S4. Vacuum-assisted lowering of the reinforcing cage: A vacuum adsorption device is installed at the orifice to accelerate the sinking of the reinforcing cage through negative pressure. An intelligent stress monitoring system is used to monitor the stress distribution of the steel cage in real time during the lowering process, and the lowering speed is automatically adjusted when the local stress exceeds the threshold. After the lowering is completed, a zinc-based protective layer with a thickness of 20-50μm is formed on the surface of the steel cage using electrochemical deposition technology; S5. Deployment and activation of shape memory alloy grouting pipe: The shape memory alloy grouting pipe, which shrinks at room temperature, is lowered along with the steel cage. After reaching the bottom of the hole, it is activated by injecting 65℃ hot water to expand and form an umbrella-shaped structure. Ultrasonic-assisted activation technology is used to accelerate the phase transformation process of shape memory alloys by generating 20kHz high-frequency vibration through a ring ultrasonic vibration device. High-performance cement slurry containing nano-silica powder with a particle size of 10-30nm and micro-expansion agent is injected. The water-cement ratio of the slurry is 0.4 and the fluidity is 300mm. S6, Integration of 3D Printed Pile Top Reinforcement Structure and Intelligent Monitoring System: The reinforcement structure is directly printed on the pile top using concrete 3D printing technology. 15% of recycled aggregate from construction waste is added to the printing material. At the same time, a distributed fiber optic grating sensor array, a nanowire humidity sensor and a wireless energy harvesting module are integrated. The sensor transmits signals using optical time-domain reflectometry, and its monitoring range covers the entire pile body; A solar power module with an output power of ≥10W is installed on the top of the pile. S7. Ground source heat pump assisted curing and carbon sink concrete application: A ground source heat pump circulation pipeline is buried around the pile body to use shallow geothermal energy to regulate the curing temperature of concrete, and the curing temperature fluctuation is controlled within ±2℃. Carbon sequestration concrete technology is adopted, incorporating 20% ​​carbonation curing industrial waste into the concrete. During the curing process, CO2 is absorbed to form calcium carbonate, and the amount of fixed CO2 per cubic meter of concrete is ≥100kg. After maintenance is completed, data from the entire construction process will be recorded using blockchain technology.

4. The green construction method for cast-in-place piles according to claim 3, characterized in that: In the preparation step of the S2 supercritical CO2 microbubble concrete, a biodegradable polymer thickener is added to improve the stability of CO2 bubbles. Ground source heat pump technology is used to provide a heat source for shape memory alloy grouting pipes, reducing conventional energy consumption; Using nanoscale anti-dispersion agents to improve the anti-dispersion properties of underwater concrete.

5. The green construction method for cast-in-place piles according to claim 3, characterized in that: In the S3 magnetic levitation guided precision drilling step, combined with real-time detection by ground-penetrating radar, underground obstacles can be identified in advance and the drilling path can be automatically adjusted.

6. The green construction method for cast-in-place piles according to claim 3, characterized in that: In the S4 vacuum-assisted rebar cage lowering step, the stability of the borehole wall is monitored in real time by an acoustic monitoring system, and the lowering speed is automatically adjusted when abnormal vibration signals occur.

7. The green construction method for cast-in-place piles according to claim 3, characterized in that: In the activation step of the S5 shape memory alloy grouting pipe, the high-performance cement grout containing nano-silica powder and micro-expansion agent has a self-healing function. When micro-cracks appear in the pile body, the nano-silica powder will react with the cement hydration products to generate an expansive substance to fill the cracks.

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