Phase-change spiral energy anchor rod and construction method thereof

Abstract

The invention discloses a phase-change spiral energy anchor rod and a construction method thereof, and relates to the technical field of integration of tunnel engineering supporting structures and shallow geothermal energy collection. The phase change spiral energy anchor rod comprises a spiral steel pipe body, a grouting guide pipe system, a phase change energy storage unit, a heat exchange pipe and an extension connector. Spiral blades are arranged on the outer wall of the spiral steel pipe body, and a heat exchange pipe is integrated in the spiral steel pipe body, penetrates through the anchor rod, is connected with an external circulation pipeline and is used for circulation of a heat transfer medium. The grouting guide pipes are symmetrically distributed along the outer wall of the steel pipe, one-way valves are arranged in grouting holes, and directional seepage of grout is achieved; the phase change energy storage unit is packaged between the inner wall of the steel pipe and the heat exchange pipe, and heat energy storage and release are achieved by adsorbing phase change materials. The supporting and heat exchange functions are deeply coupled, construction is convenient and fast, thermal response is fast, shallow geothermal energy can be efficiently recycled, the method is suitable for constructing an energy self-maintaining system of a high-ground-temperature tunnel, and the structure stability and the energy utilization efficiency are both achieved.

Description

Technical Field

[0001] This invention relates to the field of integrated underground engineering support and shallow geothermal energy harvesting technology, and in particular to a phase change spiral energy anchor and its construction method. Background Technology

[0002] In the field of tunnel engineering, traditional anchor bolt support technology has long focused on mechanical reinforcement, failing to effectively integrate the needs of shallow geothermal energy utilization. Existing anchor bolt systems, primarily composed of solid steel components, are limited by material thermal conductivity and interface contact quality, making efficient conduction of shallow geothermal energy difficult. Conventional anchor bolts, using solid steel components filled with ordinary cement mortar, exhibit high thermal resistance at the bolt-surrounding rock interface, resulting in significant bottlenecks in heat transfer paths. Furthermore, the anchor bolt installation process is disconnected from the heat exchange system construction, with repeated drilling and grouting procedures prolonging the construction period and easily causing secondary disturbance to the surrounding rock. Simultaneously, ground source heat pump systems require independently laid heat exchange pipelines, constructed separately from the anchor bolt support structure, further exacerbating the problem of low underground space utilization efficiency.

[0003] The potential of shallow geothermal energy in tunnel engineering has not yet been fully explored. As a stable, renewable, and clean energy source, the efficient utilization of shallow geothermal energy aligns with global low-carbon development strategies and green infrastructure policies. In recent years, energy policies in many countries have explicitly proposed promoting the coordinated development of underground engineering and geothermal resources to reduce reliance on fossil fuels in traditional refrigeration systems. However, the thermal performance defects and construction limitations of traditional anchor bolt technology severely restrict the integrated application of geothermal energy in support structures.

[0004] Therefore, there is an urgent need to develop a new type of anchor bolt technology that, while ensuring support performance, can construct an efficient heat exchange channel between the anchor bolt and the surrounding rock through structural innovation and material optimization, thereby achieving efficient recovery and utilization of shallow geothermal energy. This technology can not only enhance the energy self-sufficiency of tunnel engineering but also respond to the needs of green building policies, providing a sustainable solution for underground space development. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a phase change spiral energy anchor and its construction method. This anchor combines efficient geothermal exchange and structural support functions, and features convenient construction, fast thermal response, and high energy utilization. It is suitable for the construction of energy self-sustaining systems in high-temperature tunnels.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a phase change spiral energy anchor bolt, comprising a spiral steel pipe body, a grouting conduit system, a phase change energy storage unit, a heat exchange pipe, and an extension joint. The spiral steel pipe body is the main structural component of the anchor bolt, with spiral blades on its outer wall for cutting and disturbing the surrounding rock and enhancing interfacial contact performance. The heat exchange pipe is arranged throughout the interior of the spiral steel pipe body for circulating the heat transfer medium. The phase change energy storage unit is encapsulated in the gap between the inner wall of the spiral steel pipe body and the heat exchange pipe, realizing the temporary storage and release of thermal energy. The grouting conduit system is arranged on the outer wall of the spiral steel pipe body for injecting high thermal conductivity mortar into the surrounding rock during the anchor bolt insertion process. The extension joint is installed at the top of the spiral steel pipe body for connecting drilling equipment or multiple anchor bolt sections to achieve structural extension and system integration.

[0007] Preferably, the main body of the spiral steel pipe is made of Q345B low alloy steel, and its outer diameter and wall thickness can be selected according to actual construction needs. Typically, the outer diameter ranges from 35 to 42 mm, and the wall thickness is 3 mm. The outer wall of the steel pipe is provided with spiral blades. The number, diameter, pitch, and inclination angle of the spiral blades can also be flexibly set according to the surrounding rock conditions and anchoring design requirements. Generally, the number of blades is 2 to 5, the diameter is 70 to 90 mm, the pitch is 30 to 50 mm, the inclination angle is 0° to 20°, and the thickness is 2 ± 0.2 mm. The spiral blades are continuously welded to the outer wall of the steel pipe and are equidistantly arranged along the axial direction of the steel pipe. This can achieve disturbance cutting and interface roughening during the anchor bolt screwing process, enhance the anchoring effect, and promote uniform diffusion of grout.

[0008] Preferably, the grouting conduit system includes four grouting conduits symmetrically arranged along the outer wall of the spiral steel pipe body. Each conduit has an outer diameter of 4 mm and a wall thickness of 2 mm. Multiple grouting holes with a diameter of 3 mm and an axial spacing of 5 mm are evenly arranged on the conduit. The grouting holes are equipped with one-way valves with an opening pressure of 0.5 MPa ± 0.05 MPa, which can realize the directional penetration and uniform diffusion of grout during the spiraling process, forming a dense coating layer and improving the anchoring performance.

[0009] Preferably, the phase change energy storage unit is composed of solid particles formed by the adsorption of n-dodecane by expanded graphite and paraffin-based composite material mixed in a volume ratio of 3:7. It has excellent phase change heat capacity and thermal stability. It is encapsulated in a steel pipe by a porous steel plate. The steel plate has through holes for the heat exchange pipe to pass through and to prevent material leakage, so as to realize the spatiotemporal regulation and temperature balance of the internal heat energy of the anchor rod.

[0010] Preferably, the heat exchange pipe system comprises three parts: a spiral pipe, a straight pipe, and a connecting pipe. The straight pipe runs vertically through the anchor rod axis, the spiral pipe is arranged around the straight pipe, and the connecting pipe is used for end convergence. The heat exchange pipe is fixed to the inner wall of the steel pipe by a U-shaped buckle and connected to an external heat pump system by a quick-connect connector. The outside is wrapped with an aerogel insulation layer to reduce energy loss.

[0011] Preferably, the spiral steel pipe body is filled with a high thermal conductivity mortar with a thermal conductivity of not less than 2.8 W / (m·K) and a 28-day compressive strength of not less than 45 MPa. This mortar is composed of silicate cement, nano-aluminum nitride (20 wt%), and silane coupling agent (1.2 wt%), and has both mechanical support properties and high thermal conductivity.

[0012] Preferably, the extension joint is located at the top of the spiral steel pipe body, made of Q345B steel, with an outer diameter consistent with the steel pipe body and a wall thickness of 4mm; a symmetrical through-hole (10mm in diameter) is provided in the middle, which can be connected to the adjacent anchor rod section by laser welding or bolts, and the connection position is coated with epoxy glue to seal and prevent leakage; the extension joint also serves as a force transmission component during construction, and can be quickly connected to the drilling device.

[0013] This invention also provides a construction method based on the above-mentioned phase change spiral energy anchor, comprising the following steps: S1. Construction Preparations: Based on the construction drawings, measure and mark the anchor bolt hole locations on site; simultaneously, ensure the grouting equipment is in place and the grouting conduit is pre-connected to guarantee smooth system operation. S2. Drilling: The drilling operation is completed using a self-advancing stepped drill bit. During the drilling process, "low speed and stable pressure" control is maintained. After the hole is completed, positive pressure air or water is used to clean the bottom of the hole to ensure that the hole wall is intact and there is no residue inside the hole. S3. Synergistic Anchor Drilling and Grouting: The phase change spiral energy anchor is connected to the hydraulic drilling equipment through an extension joint. Grouting is performed simultaneously with the starting of the spiral drilling operation, forming an integrated anchoring-grouting construction process; S4. Staged control of grouting: S4.1 Initial grouting trigger: When the anchor bolt is screwed in to an initial depth of 0.5~1.0m, the grouting pump is started, and the grout forms a coating layer through the bottom grouting hole to enhance the front-end sealing. S4.2 Dynamic grouting balance: During the continued advancement process, the grouting pressure and flow rate are adjusted to achieve dynamic matching between axial advancement and grout penetration; S4.3 Terminal pressure compensation: After the anchor bolt reaches the design depth, it continues to rotate and is pressurized and grouted through the top guide pipe to fill the top cavity and form a complete and dense grout body; S5. Installation Completed: After the anchor system is installed and positioned, the joints are sealed to ensure that its mechanical properties and fluid tightness meet the design requirements; S6. Connecting the heat pump system: Connect the quick-connect fittings of the heat exchange tubes to the external ground source heat pump system, conduct hydraulic testing and thermal performance debugging, and finally build an integrated support-heat exchange system.

[0014] The beneficial effects of this invention: Compared with existing anchoring technologies, this invention has the following technical advantages: (1) Deeply couple the tunnel support structure with shallow geothermal energy collection technology, construct heat exchange channels through the spiral anchor body, so that the support construction and geothermal system installation can be completed simultaneously, eliminating the surrounding rock damage caused by repeated drilling in traditional processes, greatly improving construction efficiency, and realizing the integrated development of underground space "support-heat exchange".

[0015] (2) A four-way symmetrical grouting conduit and a rotary jetting mechanism are adopted. During the insertion of the anchor bolt, the grout penetrates directionally along the gap between the spiral blades to form a continuous coating layer. This significantly expands the grouting range, enhances the interfacial bonding strength, reduces the rock wall void ratio, and effectively improves the quality of surrounding rock reinforcement.

[0016] (3) The invented anchor bolt innovatively integrates geothermal intelligent regulation functions while reinforcing the surrounding rock. The phase change energy storage unit forms an adaptive temperature control mechanism through a gradient encapsulation structure, effectively capturing and storing excess heat energy of the surrounding rock. Combined with the ground source heat pump system, it achieves dynamic energy balance and significantly improves the utilization efficiency of shallow geothermal energy. In addition, while ensuring mechanical performance and durability, it utilizes renewable energy to achieve thermal regulation, reducing dependence on traditional energy sources. The overall structure and process are optimized in a coordinated manner, making construction convenient and long-term stable. It maintains the thermal environment balance of the strata and reduces the energy consumption of tunnel operation and maintenance, providing a green and sustainable energy solution for underground engineering. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a phase change spiral energy anchor rod according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the heat exchange tube structure in a phase change spiral energy anchor according to an embodiment of the present invention; Figure 3 This is a partially enlarged structural diagram of the anchor head in a phase change spiral energy anchor bolt according to an embodiment of the present invention; Figure 4 This is a partially enlarged structural diagram of the extension joint in a phase change spiral energy anchor bolt according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a porous steel plate structure in a phase change spiral energy anchor bolt according to an embodiment of the present invention.

[0018] Figure 6 This is a schematic cross-sectional view of rock stratum support in a phase change spiral energy anchor bolt according to an embodiment of the present invention.

[0019] Figure 7 This is a construction process flow diagram of a phase change spiral energy anchor bolt according to an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Spiral steel pipe body; 11. Anchor head; 12. Grouting hole; 13. Spiral blade; 14. Grouting conduit; 2. Heat exchange pipe; 21. Spiral pipe; 22. Straight pipe; 23. Connecting pipe; 3. Extension joint; 4. Perforated steel plate; 5. Rock wall. Detailed Implementation

[0021] The specific embodiments of this invention are described in detail below with reference to the accompanying drawings. However, the scope of protection of this invention is not limited to the description of these embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0022] Example 1: This invention provides a phase change helical energy anchor, such as... Figure 1-5 As shown, the phase change spiral energy anchor bolt includes a spiral steel pipe body 1, a heat exchange pipe 2, an extension joint 3, and a perforated steel plate 4.

[0023] like Figure 1 As shown, the spiral steel pipe body 1 is made of Q345B low alloy steel, with an outer diameter of Φ38mm, a wall thickness of 3mm, and a surface nitriding treatment, achieving a hardness ≥800HV. The spiral blades 13 have a diameter of 80mm, a pitch of 40mm, a thickness of 2mm, a blade inclination angle of 15°, and are numbered in triplicate, uniformly welded to the outer wall of the steel pipe. In some embodiments, four grouting conduits 14 (Φ4mm×2mm) are symmetrically distributed along the axial direction of the outer wall of the steel pipe, and continuous grouting holes 12 (Φ3mm, spaced 5mm apart) are opened 15mm from the end of the anchor head 11, with one-way valves installed in the holes (opening pressure 0.5MPa).

[0024] like Figure 2 As shown, the heat exchange tube 2 consists of a copper alloy spiral tube 21, a straight tube 22, and a connecting tube 23. The straight tube 22 vertically passes through the axis of the spiral tube 21 and is fixed to the inner wall of the steel pipe by U-shaped clips (500mm spacing). The exposed end of the heat exchange tube is connected to a quick-connect fitting (pressure 1.6MPa) and wrapped with an aerogel insulation layer (10mm thick).

[0025] like Figure 1 and Figure 4 As shown, extension joint 3 is a Q345B steel joint with an outer diameter of Φ38mm, a wall thickness of 4mm, a symmetrical through hole (Φ10mm) in the middle, and internal threads at both ends (3mm pitch, 20mm depth). Assuming a single anchor rod is 2m long, when it needs to be extended, screw the head of the second anchor rod into the extension joint of the first anchor rod and fix it with a high-strength bolt. Apply epoxy resin sealant (1mm thickness) to the joint.

[0026] like Figure 5As shown, the porous steel plate structure 4 is made of Q345B steel discs with the same diameter as the inner diameter of the steel pipe body 1. It has an opening rate of 40% and two fully penetrating 4mm diameter holes and multiple 1mm diameter holes on its surface. The two 4mm diameter holes allow the heat exchange tubes to pass through, while the remaining small holes prevent leakage of the phase change energy storage particles. After the phase change energy storage unit is filled, laser welding is used to seal the opening at the top of the anchor bolt.

[0027] Specifically, the construction method of the phase change spiral energy anchor bolt according to the embodiments of the present invention is as follows: Figure 7 As shown, the first step is to complete all construction preparations before anchor bolt support. Next, the anchor bolt hole positions are measured and laid out, and the drilling positions are marked using a total station, with an error ≤2cm. Before drilling, the rock surface must be cleaned and loose rocks removed. A hydraulic rotary drilling rig is selected, equipped with a self-propelled stepped drill bit (carbide tip, front diameter Φ38mm, tail enlargement to Φ50mm). During initial drilling, the drill bit is held vertically against the rock surface, and the low-speed setting is started (60rpm, feed pressure 8kN). After drilling to a depth of 0.5m, the setting is switched to normal (70rpm, feed pressure 10kN). Real-time deviation monitoring is conducted during drilling, using a borehole inclination monitoring system to provide real-time feedback on deviations. If the angle is >1°, the hydraulic deviation correction device is automatically activated (adjustment speed 5mm / s). After drilling is completed, borehole acceptance is performed. The final hole depth error should be ≤30mm, the verticality deviation ≤0.8°, and the thickness of residual rock cuttings at the bottom of the hole ≤5cm.

[0028] Subsequently, the anchor bolts were driven in and grouting was performed. Specifically, the upper extension joint of the anchor bolt was connected to the hydraulic screw-in device, with the screw-in torque set to 800 N·m, the rotation speed to 20 rpm, and the advance speed to 30 mm / min. When the anchor bolt was driven in 0.5 m, the grouting pump (model ZB-3) was started with an initial pressure of 0.3 MPa. The grout was injected through the bottom grouting hole to the front end of the borehole, forming the initial coating layer.

[0029] In some embodiments, when the grouting depth reaches 1m, the dynamic equilibrium grouting stage is entered, the grouting pressure is stepped up to 0.6MPa, the grouting speed is adjusted to 25rpm, and the propulsion speed is 40mm / min. The grout flow rate is dynamically matched to 12L / min according to the formula (1) of claim 9, and the rock mass fissures are uniformly filled through the radial holes (90° symmetrically distributed) of the four grouting pipes.

[0030] In some embodiments, the anchor bolt is rotated for 10 seconds (15 rpm) after reaching the final hole to eliminate dead zones in grout flow. The bottom grouting hole is closed, and the grouting is switched to the top grouting conduit for pressurized grouting (pressure 1.0 MPa, lasting 2 min), and the top cavity is filled in reverse through a one-way valve.

[0031] like Figure 6As shown, after grouting is completed, thermal performance testing is conducted. The exposed heat exchange pipe at the upper end of the anchor bolt is connected to a circulating water pump, and water is circulated at a rate of 1.0 m / s to ensure that the temperature difference between the inlet water and the rock mass is 12℃ for 72 hours. The heat exchange is recorded every 8 hours. When the unit heat exchange is ≥65W / m and the temperature difference decay rate is ≤5%, the thermal performance is considered to meet the design requirements.

[0032] Example 2: This invention provides a phase change helical energy anchor, such as... Figures 1 to 6 As shown, the phase change spiral energy anchor bolt includes a spiral steel pipe body 1, a grouting hole system, a phase change energy storage unit, a heat exchange pipe 2, a high thermal conductivity filling mortar, and an extension joint.

[0033] The main body of the spiral steel pipe 1 is made of Q345B low alloy steel, and the surface is nitrided to improve wear resistance; the outer diameter is Φ35-42mm and the wall thickness is 3mm; the surface is provided with spiral blades (blade diameter 70~90mm, pitch 30~50mm, thickness 2±0.2mm, inclination angle 0°-20°), and the number of blades is 2~5.

[0034] The grouting hole system includes four grouting guide pipes 14 (4mm in diameter and 2mm in wall thickness) evenly and symmetrically distributed along the outer wall of the steel pipe. A continuous grouting hole group is set starting 15mm from the anchor head. The grouting hole group includes multiple grouting holes 12, each with a diameter of Φ3mm and an axial spacing of 5mm. Each grouting hole 12 has a built-in one-way valve (opening pressure 0.5MPa±0.05) to achieve directional penetration of grout.

[0035] The phase change energy storage unit comprises solid particles with a diameter of 5-8 mm formed by adsorbing n-dodecane onto expanded graphite (85% porosity). These particles are then mixed with paraffin-based composite materials at a volume ratio of 3:7 to form an energy storage material that enhances high-temperature stability. During pile construction, the particles are pre-encapsulated in the gap between the inner wall of the steel pipe and the central heat-conducting pipe. The upper end is sealed by laser welding of a porous steel plate 4 (35-50% porosity, Φ1 mm aperture) to prevent particle leakage while allowing the heat-conducting pipe to pass through.

[0036] The heat exchange tube 2 is a copper alloy heat exchange tube located at the central axis of the steel pipe, with a diameter of Φ5mm. It is fixed to the inner wall by U-shaped clips (500mm spacing) and is used for circulating heat transfer media (including but not limited to water or antifreeze). Its structural form includes but is not limited to W-type, U-type, and spiral type. The heat exchange tube 2 includes a spiral tube 21, a straight tube 22, and a connecting tube 23. The straight tube 22 vertically passes through the axis of the spiral tube 21, and the connecting tube 23 is connected to the lower end of the straight tube 22 and the spiral tube 21 to form a whole. In addition, the exposed end of the heat exchange tube 2 has a 15mm quick connector, which is used to connect to the ground source heat pump circulation pipeline through a quick-connect fitting (pressure resistance 1.6MPa), and is covered with an aerogel insulation layer.

[0037] The high thermal conductivity filling mortar is made of 42.5 grade silicate cement, nano aluminum nitride (20wt% dosage, particle size 50-80nm), and silane coupling agent (1.2wt% dosage). The measured thermal conductivity is ≥2.8W / (m·K) and the 28d compressive strength is ≥45MPa.

[0038] The extension joint 3 is made of Q345B low alloy steel; with an outer diameter of Φ38-45mm and a wall thickness of 4mm; it has a symmetrical, fully penetrating circular hole (10mm in diameter) in the middle, which is laser-welded to the top of the anchor rod for connecting the drilling device or extending the length of the anchor rod with high-strength bolts.

[0039] This invention also provides a construction method for the phase change spiral energy pile as described above, such as... Figure 7 As shown, the construction method includes the following four steps.

[0040] Step 1: Drilling.

[0041] Drilling rig positioning is performed using a laser positioning instrument for drilling calibration. A self-feeding stepped drill bit (carbide tip) is used for a one-pass drilling process. The diameter of the cutting section at the front end of the drill bit is Φ38mm, the transition cone angle in the middle is 12°, and the tail end is enlarged to Φ50mm. Drilling parameters are dynamically controlled: rotation speed 60-80rpm, feed pressure 8-12kN, and the hole inclination monitoring system provides real-time feedback on deviations (automatically activating the hydraulic correction device when >1°). The final hole depth error is ≤50mm, and the verticality deviation is ≤1°.

[0042] Step 2: Synchronous anchor drilling - grouting and implantation.

[0043] The anchor bolt screwing and grouting processes are coordinated in time and space using a hydraulic drive system. The specific process is as follows: ① Initial grouting trigger (0-1m): The top extension interface of the anchor bolt is connected to the hydraulic screw-in device, and it is screwed in along the borehole according to the designed torque. When the anchor bolt head is screwed in to a depth of 0.5m, the grouting pump is started (initial pressure 0.3MPa), and the grout is rapidly injected through the top grouting conduit and diffuses towards the borehole front end through continuous grouting holes (5mm spacing) at the bottom of the anchor bolt. The anchor bolt rotation speed is 20rpm, and the advance speed is 30mm / min, forming the initial grouting coating layer.

[0044] ② Dynamic Balance Grouting (1-3m): As the anchor bolt insertion depth increases, the grouting pressure increases stepwise (0.5→0.8MPa). Utilizing the centrifugal force generated by the rotating spiral blades (speed 25rpm), the grout is uniformly sprayed along the radial holes (90° symmetrical distribution) of the four grouting guide pipes. The grouting flow rate and the propulsion speed satisfy equation (1) for dynamic matching: (1) Where, Q is the grouting flow rate, in L / min; v is the advancing rate, in mm / min; P is the grouting pressure, in MPa. Through the synergistic effect of the spiral blades on the outer wall of the anchor rod and the grouting holes, the two-way strengthening of axial filling and radial penetration of the grout is achieved.

[0045] ③ Final stage pressure compensation (from 3 m to the designed depth): After the anchor rod reaches the final hole position, it maintains rotation for 10 s (rotation speed 15 rpm) to eliminate dead corners of slurry flow. Close the bottom grouting hole and switch to the top grouting conduit to pressurize and supplement the slurry (pressure 1.0 MPa, for 2 min). The reverse supplement of the slurry is achieved through the one-way valve (opening pressure 0.5 MPa) in the grouting conduit to eliminate the top cavity.

[0046] Step 3: Thermal performance test.

[0047] The circulating water pump enters the heat conduction pipe (flow rate 1.0 m / s, temperature difference between the inlet water temperature and the rock temperature is 10 °C) for 72 hours. The unit heat transfer amount ≥ 65 W / m (under the condition of rock temperature 18 °C) is qualified. After the thermal performance acceptance is qualified, it can be connected to the heat pump circulation system.

[0048] Step 4: Temperature compensation measures.

[0049] During summer construction, the slurry temperature is controlled ≤ 25 °C (cool the mixing water with circulating water); during winter construction, the slurry temperature is ≥ 10 °C (heat the mixing water to 30 - 40 °C with resistance).

[0050] The above embodiments are only used to illustrate the present invention and are not limitations to the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of this application. The patent protection scope of the present invention shall be defined by the claims.

Claims

1. A phase change spiral energy anchor, characterized in that, include: The spiral steel pipe body has spiral blades on its outer wall and a heat exchange pipe inside it. The heat exchange pipe runs through the spiral steel pipe body and is connected to an external circulation pipeline for circulating the heat transfer medium. The grouting conduit system includes multiple grouting conduits symmetrically distributed along the outer wall of the spiral steel pipe body, and the grouting conduits are provided with continuous grouting holes; A phase change energy storage unit is encapsulated in the gap between the inner wall of the spiral steel pipe body and the heat exchange pipe; An extension joint, located at the top of the spiral steel pipe body, is used to connect a drilling device or extend an anchor rod.

2. The phase change spiral energy anchor bolt according to claim 1, characterized in that, The diameter of the spiral blade is 70~90mm, the pitch is 30~50mm, the number of blades is 2~5, and the blade tilt angle is 0°~20°.

3. The phase change spiral energy anchor bolt according to claim 1, characterized in that, The number of grouting conduits is 4, symmetrically distributed at 90° along the outer wall of the spiral steel pipe body; the diameter of the grouting hole is 3mm, the axial spacing is 5mm, and a one-way valve with an opening pressure of 0.5MPa±0.05 is built in.

4. The phase change spiral energy anchor bolt according to claim 1, characterized in that, The phase change energy storage unit includes solid particles formed by the adsorption of n-dodecane by expanded graphite. The solid particles are mixed with paraffin-based composite material at a volume ratio of 3:7 and sealed inside the spiral steel pipe body by a porous steel plate.

5. The phase change spiral energy anchor bolt according to claim 1, characterized in that, The heat exchange tube includes a spiral tube, a straight tube, and a connecting tube. The straight tube passes vertically through the axis of the spiral tube and is fixed to the inner wall of the spiral steel tube body by a U-shaped buckle.

6. The phase change spiral energy anchor bolt according to claim 1, characterized in that, The spiral steel pipe body is filled with high thermal conductivity mortar, the thermal conductivity of which is ≥2.8W / (m·K) and the 28d compressive strength is ≥45MPa.

7. The phase change spiral energy anchor bolt according to claim 6, characterized in that, The high thermal conductivity filling mortar is formulated from silicate cement, nano aluminum nitride and silane coupling agent, wherein the amount of nano aluminum nitride is 20wt% and the amount of silane coupling agent is 1.2wt%.

8. The phase change spiral energy anchor bolt according to claim 1, characterized in that, The extension joint 3 has symmetrical through holes in the middle and is connected to the adjacent anchor rod by laser welding or high-strength bolts.

9. A construction method for a phase change spiral energy anchor bolt as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Drilling: Drilling is carried out using a self-advancing stepped drill bit. The hole inclination deviation is monitored and corrected in real time during the drilling process. (2) Synchronous anchor drilling-grouting: While the anchor is screwed into the borehole, high thermal conductivity filling mortar is injected in stages through the grouting pipe. The stages include initial grouting triggering, dynamic balance grouting and final pressure compensation. (3) Thermal performance test: The heat transfer medium is introduced into the heat exchange tube and the unit heat exchange capacity is tested to see if it meets the preset threshold. (4) Temperature compensation measures: Adjust the grout temperature according to the construction season.

10. The construction method according to claim 9, characterized in that, In step (2), the grouting pressure is increased in stages with the depth of anchor bolt insertion, with an initial pressure of 0.3 MPa and a final pressure of 1.0 MPa, and the grouting flow rate and the advancing speed satisfy the dynamic matching of formula (1): （1） In the formula, This refers to the grouting flow rate, expressed in L / min. The propulsion rate is expressed in mm / min. The pressure is the grouting pressure, measured in MPa.

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