Intelligent pile for measuring soil moisture content based on active heat pulse principle

Abstract

This application discloses a smart pile for measuring soil moisture content based on the principle of active thermal pulse, belonging to the field of soil moisture content measurement technology. It includes a metal pile body, a power supply, a temperature measuring element, and a data acquisition and processing system. The temperature measuring element is built into a cavity within the metal pile body. The power supply is used to directly energize the metal pile body or generate active thermal pulses by energizing a heating element. The temperature measuring element measures the temperature at different depths within the metal pile body. The data acquisition and processing system collects temperature data and performs inversion calculations based on the temperature changes over time at different depths to obtain the soil moisture content at different depths. The entire device has high structural strength and can be directly driven into the soil layer. The internal core components are not subject to soil compression, shearing, or external water vapor erosion, thus meeting the long-term, accurate, in-situ monitoring needs of deep soil moisture content in field environments.

Description

Technical Field

[0001] This application relates to the field of soil moisture content measurement technology, and more specifically, to a smart pile for measuring soil moisture content based on the principle of active thermal pulse. Background Technology

[0002] In the evolution of soil slope hazards, rainfall infiltration leads to an increase in the moisture content of deep soil layers. Obtaining real-time soil moisture content data is of great significance for natural disaster early warning and disaster prevention and mitigation efforts.

[0003] Traditional soil moisture sensors, when buried separately in deep soil, are costly and have a low survival rate. When installed together with anti-slide piles, they cannot withstand the mechanical impact during slope piling, nor can they resist the huge shear force generated by the soil sliding surface. Therefore, it is difficult to conduct deep and long-term in-situ monitoring in the field, and cannot provide accurate boundary conditions for dynamic assessment of slope stability. Summary of the Invention

[0004] This application aims to provide a smart pile for measuring soil moisture content based on the principle of active thermal pulse, which solves the problem that traditional sensors in the prior art are difficult to adapt to long-term in-situ moisture content monitoring of deep soil, while providing slope reinforcement and sensing functions.

[0005] A smart pile for measuring soil moisture content based on the principle of active thermal pulse includes: Metal pile body, power supply, temperature measuring element and data acquisition and processing system; One end of the metal pile is set as a pointed tip. In the working state, the metal pile is driven into the soil layer to a preset depth along its axis. The metal pile has a receiving cavity inside. The opening end of the receiving cavity is provided with a sealing structure. The sealing structure is sealed to the metal pile to seal and isolate the receiving cavity from the external environment. The metal pile body includes a hollow steel pipe or a solid steel column; The power source is connected to the metal pile body, and the power source is used to directly energize the solid steel column to heat the solid steel column; or, a heating element is provided in the accommodating cavity, and the power source is connected to the heating element, and the power source is used to energize the heating element to assist the heating element in heating the hollow steel pipe. The temperature sensing element is disposed in the accommodating cavity and is used to detect temperature data at different depths of the metal pile in real time. The data acquisition and processing system is connected to the temperature measuring element and is used to collect temperature data at different depths at preset time intervals during the data acquisition period. Based on the characteristics of temperature data at different depths changing over time, the volumetric water content of the soil at different depths around the metal pile is obtained.

[0006] Optionally, the temperature measuring element includes a distributed temperature measuring optical fiber extending along the axial direction of the metal pile, or a multi-point temperature measuring array arranged along the axial direction of the metal pile.

[0007] Optionally, the cavity formed by the inner wall of the hollow steel pipe is the receiving cavity.

[0008] Optionally, the heating element includes multiple heating cables, which are arranged close to the inner wall of the steel pipe and extend along the axial direction of the steel pipe, and are evenly spaced apart in the circumferential direction of the steel pipe.

[0009] Optionally, the multi-point temperature measurement array includes multiple temperature sensors evenly spaced along the axial direction of the steel pipe; the number of multi-point temperature measurement arrays is set to multiple sets, and the multiple sets of multi-point temperature measurement arrays are evenly spaced along the circumference of the steel pipe.

[0010] The number of groups in the multi-point temperature measurement array is the same as the number of heating cables, and the temperature sensor is fixed on the inner wall of the steel pipe and is spaced apart from the heating cables.

[0011] The temperature sensor and the heating cable are respectively fixed to the inner wall of the steel pipe with tape.

[0012] Optionally, the heating element includes an AC induction coil, which is fixed to the sealing structure and suspended at the axis of the steel pipe. The power source provides high-frequency AC power to the AC induction coil, which generates an alternating magnetic field after being energized and induces eddy currents in the steel pipe wall to generate heat and raise the temperature of the steel pipe.

[0013] Optionally, the solid steel column has a channel inside, and the inner cavity of the channel forms the receiving cavity, the size of which is adapted to the size of the temperature measuring element.

[0014] Beneficial effects: The intelligent pile for measuring soil moisture content based on the active thermal pulse principle described in this application includes a metal pile body, a power supply, a temperature measuring element, and a data acquisition and processing system. By embedding the temperature measuring element within the metal pile body, the element can be effectively protected from soil compression, shearing, and external water vapor erosion, significantly improving the long-term survival rate of the monitoring element in deep soil and meeting the needs of long-term in-situ monitoring of deep soil. Simultaneously, active thermal pulses are generated by the self-heating of the metal pile body or by the auxiliary heating element. Combined with temperature change data, the soil moisture content at different depths can be retrieved. The entire device has high structural strength, a simple and reliable overall structure, and can be directly implanted into the soil layer through pile driving operations. It is easy to install, adaptable to complex field construction environments, and provides slope reinforcement and sensing functions. It can stably output soil moisture content data at different depths over a long period, providing reliable basic data support for long-term stability monitoring and disaster early warning of soil slopes. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a smart pile for measuring soil moisture content based on the active thermal pulse principle, according to an embodiment of this application. Figure 2 This is a schematic diagram of the arrangement of heating cables and temperature sensors on the cross-section of a steel pipe in a smart pile for measuring soil moisture content based on the active thermal pulse principle, according to an embodiment of this application.

[0017] Explanation of reference numerals in the attached figures: 1. Steel pipe; 11. Receptacle; 2. Sealing cap; 3. Conical structure; 4. Heating cable; 5. Temperature sensor; 6. Data acquisition instrument. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In related technologies, soil moisture sensors have a low survival rate in deep soil, cannot withstand the mechanical impact during slope piling, and cannot resist the huge shear force generated by the soil sliding surface. Therefore, it is difficult to conduct deep and long-term in-situ monitoring in the field and cannot provide accurate boundary conditions for dynamic assessment of slope stability.

[0020] In view of this, this application provides a smart pile for measuring soil moisture content based on the active thermal pulse principle, which can realize long-term in-situ monitoring of deep soil moisture content.

[0021] See Figure 1 and Figure 2 A smart pile for measuring soil moisture content based on the principle of active thermal pulse includes: a metal pile body, a power supply, a temperature measuring element, and a data acquisition and processing system. One end of the metal pile is set as a pointed tip. In the working state, the metal pile is driven into the soil layer at a preset depth along its axis. The metal pile has a receiving cavity 11 inside. The opening end of the receiving cavity 11 is provided with a sealing structure. The sealing structure is sealed to the metal pile to seal and isolate the receiving cavity 11 from the external environment. The power source is connected to the metal pile body, and the power source is used to directly energize the metal pile body to heat it up; or, a heating element is provided in the accommodating cavity 11, and the power source is connected to the heating element, and the power source is used to energize the heating element to assist the heating element in heating the metal pile body. The temperature measuring element is disposed in the accommodating cavity 11 and is used to detect the temperature data at different depths of the metal pile in real time. The data acquisition and processing system is connected to the temperature measuring element and is used to collect temperature data at different depths at preset time intervals during the data acquisition period. Based on the characteristics of temperature data at different depths changing over time, the volumetric water content of the soil at different depths around the metal pile is obtained.

[0022] Active thermal pulse (APP) is a technology that actively injects instantaneous heat into a measured object using external energy and monitors its temperature response to obtain its physical properties. The smart pile provided in this embodiment is based on this principle. By heating the metal pile and monitoring its temperature response, the volumetric water content of the soil surrounding the metal pile is obtained.

[0023] Specifically, in the working state (i.e., when monitoring soil moisture content), the smart pile provided in this embodiment has its metal body embedded in the soil layer being measured. As the main load-bearing structure of the entire device, the metal pile possesses sufficiently high structural strength to withstand the mechanical impact during pile driving and to resist the shear forces within the deep soil. The metal pile has an internal cavity 11 for installing a temperature-sensing element. By setting a sealing structure at the opening of the cavity 11, the temperature-sensing element can be sealed within the cavity 11, isolating it from moisture in the external soil, reducing the impact of environmental erosion on the element's lifespan, and preventing interference from the external environment during measurement, thus ensuring the stability of long-term monitoring.

[0024] The power supply is externally located and connected to the metal pile to directly energize it and heat it up; alternatively, a heating element is installed inside the accommodating cavity 11, and the power supply powers the heating element to assist in heating the metal pile. During the heating process, the heat from the metal pile diffuses into the surrounding soil. Since soils with different moisture contents have significantly different heat capacities and thermal conductivity rates, the rate of heat diffusion varies in soils with different moisture contents, resulting in different temperature variations over time at different locations on the metal pile.

[0025] The temperature sensing element can continuously monitor the temperature of the metal pile at different depths. The data acquisition and processing system includes an acquisition module and a processing module. The acquisition module is connected to the temperature sensing element and can record temperature data at different depths at preset time intervals. The processing module is connected to the acquisition module and can obtain the temperature change characteristics of the metal pile at different depths over time, and plot the in-situ temperature change characteristic curve (ΔT-t) at each depth. Based on this characteristic curve and combined with the pre-constructed ideal heat transfer model, the heat capacity change and heat conduction rate can be analyzed and extracted, and the mapping relationship between temperature response and soil moisture can be established, thereby accurately retrieving the soil volumetric water content at different depths of the deep profile.

[0026] Optionally, the temperature measuring element includes a distributed temperature measuring optical fiber extending along the axial direction of the metal pile, or a multi-point temperature measuring array arranged along the axial direction of the metal pile.

[0027] Distributed temperature sensing fiber optic cable, also known as a distributed fiber optic temperature measurement system (DTS), is based on fiber optic sensing principles and enables long-distance, continuous, and real-time temperature distribution monitoring. In practical applications, it is arranged along the axial direction of the metal pile within the receiving cavity 11 to obtain temperature distribution data across the entire axial range of the metal pile, facilitating the acquisition of continuous and complete deep profile moisture content data with higher accuracy. In contrast, a multi-point temperature sensing array uses multiple independent temperature sensors 5 arranged at preset intervals along the axial direction to acquire temperature data at predetermined intervals, resulting in lower cost, simpler structure, and easier maintenance. The type of temperature sensing element can be flexibly selected based on actual monitoring needs and budget constraints.

[0028] Optionally, the metal pile body is a hollow steel pipe 1, and the cavity formed by the inner wall of the steel pipe 1 is the receiving cavity 11.

[0029] like Figure 1 As shown, in this embodiment, the metal pile body adopts a thick-walled seamless hollow steel pipe 1, which has high overall mechanical strength. As a rigid skeleton for the anti-slide pile, it can withstand the mechanical impact during pile driving and is not easily damaged during the implantation into deep soil layers. In subsequent use, it can also directly withstand the thrust of the slope soil and resist the shearing action generated by the soil sliding surface, ensuring that the entire device can be stably buried in deep soil for a long time without structural damage due to soil deformation. The cavity inside the steel pipe 1 can be directly used as a receiving cavity 11 to accommodate the temperature measuring element and the heating element, thereby protecting the core element inside the steel pipe 1, avoiding the element from being directly subjected to soil compression and shearing action, and also avoiding water vapor erosion of the element, ensuring the long service life of the element.

[0030] Meanwhile, the wall of steel pipe 1 possesses excellent thermal conductivity, acting as a heat-conducting outer shell that transfers heat to the external soil and senses soil temperature. The static air (or vacuum) inside the cavity of steel pipe 1 has low thermal conductivity, forming a physical barrier with extremely high thermal resistance, cutting off the path of heat transfer into the pipe cavity. Forced by the significant difference in thermal resistance between the inside and outside of the pipe, the heat accumulated on the wall of steel pipe 1 will radially and unidirectionally penetrate the outer shell of the heat-conducting steel pipe 1 and radiate into the surrounding soil. This unidirectional heat radiation avoids interference with the measurement results caused by heat diffusion into the inner cavity of steel pipe 1, ensuring the accuracy of the measurement.

[0031] A pointed cone structure 3 is installed at the bottom of the steel pipe 1, which can reduce the resistance during the pile driving process, making it easier to press the steel pipe 1 pile into the soil layer as a whole and reducing the construction difficulty. A sealing cap 2 is installed at the top of the steel pipe 1, which serves as a sealing structure to seal the cavity inside the pipe. Through physical cut-off, it can isolate external air and prevent surface rainfall from flowing back in, protecting the internal temperature measuring and heating elements from moisture corrosion. At the same time, it can also create an independent and closed environment inside the pipe cavity that is not disturbed by external airflow, further ensuring the accuracy of the measured temperature change data and improving the precision and stability of the measurement results.

[0032] Optionally, the heating element includes multiple heating cables 4, which are closely attached to the inner wall of the steel pipe 1 and extend along the axial direction of the steel pipe 1. The multiple heating cables 4 are evenly spaced in the circumferential direction of the steel pipe 1.

[0033] In one optional embodiment, the heating element employs multiple heating cables 4. The heating cables 4 are fixed tightly against the inner wall of the steel pipe 1 and extend axially along the steel pipe 1. The uniform circumferential distribution of the multiple heating cables 4 ensures more uniform heating. As an example, in this embodiment, the heating element uses four flexible constant-power heating cables 4 of equal length. These four heating cables 4 are laid straight downwards along the depth direction of the inner wall of the steel pipe 1 (i.e., the axial or longitudinal direction of the steel pipe 1), and are arranged in a cross-shaped symmetrical distribution at 90° intervals on the cross-section of the steel pipe 1. The heating cables 4 form a circuit by connecting to an external power source through wires passing through the sealing cover 2. Once energized, they continuously generate heat. The heat spreading from adjacent heating cables 4 to both sides of the pipe wall collides at the pipe wall position between them, enabling the cross-section of the thick-walled steel pipe 1 to reach a basically uniform temperature in a very short time, thus constructing a uniform temperature field and making the steel pipe 1 pile body an isothermal body.

[0034] Through the above arrangement, multiple heating cables 4 form a multi-line symmetrical heating method, which can achieve uniform heating of steel pipe 1 and ensure that the temperature of the same cross section of steel pipe 1 is uniform. At the same time, by combining multi-line symmetrical heating with the internal cavity structure of steel pipe 1, the heat superposition effect is used to overcome the heat loss error of thick-walled steel pipe 1. The radial uniform heat transfer boundary conditions required for single probe water content measurement are perfectly reconstructed on a macroscopic level, ensuring the accuracy of the inversion results.

[0035] Optionally, the multi-point temperature measurement array includes multiple temperature sensors 5 evenly spaced along the axial direction of the steel pipe 1; the number of multi-point temperature measurement arrays is set to multiple sets, and the multiple sets of multi-point temperature measurement arrays are evenly spaced along the circumference of the steel pipe 1.

[0036] like Figure 1As shown, in this embodiment, a multi-point temperature measurement array is selected as the temperature measurement element. The multi-point temperature measurement array specifically includes multiple miniature temperature sensors 5 (such as PT100). The multiple miniature temperature sensors 5 are evenly spaced along the depth direction of the steel pipe 1 and arranged in a straight line. In an optional embodiment, the interval can be set to 10cm.

[0037] Multiple sets of multi-point temperature measurement arrays are preferably set up and evenly distributed along the circumference of the steel pipe 1. This allows for the simultaneous acquisition of temperature data at different circumferential locations at the same depth, which helps reduce measurement errors, makes the temperature measurement results at the same depth more accurate, and further improves the accuracy of moisture content inversion.

[0038] The acquisition module in the data acquisition and processing system can be a data acquisition instrument 6. Each temperature sensor 5 in the multi-point temperature measurement array can be connected to the external data acquisition instrument 6 via a cable passing through a sealed structure. The data acquisition instrument 6 is used to acquire temperature data at preset time intervals (e.g., 1 second) during the data acquisition period, and transmits the data to the processing module after acquisition. The processing module can be a remote computer or server that communicates with the data acquisition instrument 6. After receiving the temperature data, it can perform data analysis and processing to obtain the soil volumetric water content at the corresponding depth location and automatically output the water content monitoring results.

[0039] In this embodiment, the method for inverting the soil volumetric moisture content based on temperature response (temperature change characteristics over time) is a known technology in the field. The corresponding processing module also uses a known program to perform data processing or calculation. This application does not involve any improvement to the computer program itself.

[0040] Optionally, the number of groups in the multi-point temperature measurement array is the same as the number of heating cables 4, and the temperature sensor 5 is fixed on the inner wall of the steel pipe 1 and has a gap between it and the heating cables 4.

[0041] As an example, in this embodiment, the multi-point temperature measurement array is set to four groups, which are arranged in an alternating manner with the four heating cables 4, such as... Figure 2 As shown, the four sets of multi-point temperature measurement arrays are arranged at intervals corresponding to the four heating cables 4. The temperature sensor 5 in each set is fixed on the inner wall of the steel pipe 1 and maintains a certain distance from the heating cable 4.

[0042] Optionally, the temperature sensor 5 and the heating cable 4 are respectively fixed to the inner wall of the steel pipe 1 with tape.

[0043] Specifically, in this embodiment, the temperature sensor 5 and the heating cable 4 are preferably fixed to the inner wall of the steel pipe 1 using tape. This fixing method is simple to operate, low in cost, and can ensure the relative position of the temperature sensor 5 and the heating cable 4 is stable, preventing displacement during the pile driving process and ensuring the reliability of the temperature measurement results.

[0044] In other embodiments, when the temperature sensing element is a distributed temperature sensing fiber, the number of distributed temperature sensing fibers can also be set to multiple, consistent with the number of heating cables 4. The above-mentioned tape fixing method can also be used to fix the distributed temperature sensing fibers and heating cables 4 to the inner wall of the steel pipe 1 respectively. Multiple fixing points can be set according to the depth of the steel pipe 1.

[0045] Optionally, the heating element includes an AC induction coil, which is fixed to the sealing structure and suspended at the axis of the steel pipe 1. The power source is used to provide high-frequency AC power to the AC induction coil, which generates an alternating magnetic field after being energized and induces eddy currents in the wall of the steel pipe 1 to generate heat and raise the temperature of the steel pipe 1.

[0046] In other embodiments, the heating element can also be an AC induction coil. A corresponding hook or other fixing structure can be provided inside the sealing cover 2 at the top of the steel pipe 1 to suspend and fix the AC induction coil at the axial position of the steel pipe 1. This does not occupy the arrangement space on the inner wall of the steel pipe 1, making the arrangement of the temperature sensing element more flexible. The AC induction coil forms a circuit with the power supply through a wire passing through the sealing cover 2. When the power supply outputs high-frequency AC current to the AC induction coil, the AC induction coil will generate an alternating magnetic field around it. This alternating magnetic field will penetrate the entire steel pipe 1, inducing eddy currents within the pipe wall. The heating effect of the eddy currents directly raises the overall temperature of the steel pipe 1.

[0047] Optionally, the metal pile is a solid steel column with a channel inside, the inner cavity of the channel forming the receiving cavity, and the size of the receiving cavity is adapted to the size of the temperature measuring element.

[0048] In other embodiments, the metal pile can also be a solid steel column. Tiny perforated structures are created inside the solid steel column to house the temperature sensing element. The openings of the perforations are sealed with appropriate plugs or other sealing structures to prevent the intrusion of external dust, rainwater, etc. The temperature sensing element is connected to an external data acquisition instrument 6 via wires passing through the sealed structure. The temperature sensing element can also be a multi-point temperature sensing array spaced along the axial direction of the steel column or a distributed temperature sensing optical fiber extending along the axial direction of the steel column. The size of the perforations is adapted to the size of the selected temperature sensing element. Because the solid steel column has a high resistivity, the power supply can be directly connected in series with the solid steel column to form a circuit. A low-voltage, high-current (thousands of amperes) power supply is applied to the entire solid steel column, and the Joule heating generated by the column's own resistance is sufficient to heat the column, thus creating a uniform temperature field within the steel column without the need for additional heating elements.

[0049] The intelligent pile for measuring soil moisture content based on the active thermal pulse principle provided in this application, by embedding a temperature measuring element in the metal pile body and directly or indirectly heating the metal pile body, endows the pile body with the ability to actively emit thermal pulses and sense temperature. This makes the entire robust anti-slide pile equivalent to a high-precision giant hydrothermal probe, which can be directly driven into the soil layer through pile driving operations without the need to insert fragile sensors into the soil. This makes up for the shortcomings of traditional anti-slide piles that cannot sense the dynamic moisture of the surrounding soil and the low survival rate of traditional moisture sensors in deep soil. It can realize long-term in-situ monitoring of deep soil moisture content and obtain the real moisture changes at the pile-soil interface, thereby providing accurate boundary conditions for dynamic assessment of slope stability, which is of great significance for natural disaster early warning and disaster prevention and mitigation.

[0050] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0051] It should also be noted that, in this document, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "includes a..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0052] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, for those skilled in the art, there will be different forms of changes in the specific implementation methods and application scope based on this application. It is neither necessary nor possible to exhaustively list all implementation methods here, and obvious changes or modifications derived therefrom are still within the protection scope of this application.

Claims

1. A smart pile for measuring soil moisture content based on the principle of active thermal pulse, characterized in that, include: Metal pile body, power supply, temperature measuring element and data acquisition and processing system; One end of the metal pile is set as a pointed tip. In the working state, the metal pile is driven into the soil layer to a preset depth along its axis. The metal pile has a receiving cavity inside. The opening end of the receiving cavity is provided with a sealing structure. The sealing structure is sealed to the metal pile to seal and isolate the receiving cavity from the external environment. The metal pile body includes a hollow steel pipe or a solid steel column; The power source is connected to the metal pile body, and the power source is used to directly energize the solid steel column to heat the solid steel column; or, a heating element is provided in the accommodating cavity, and the power source is connected to the heating element, and the power source is used to energize the heating element to assist the heating element in heating the hollow steel pipe. The temperature sensing element is disposed in the accommodating cavity and is used to detect temperature data at different depths of the metal pile in real time. The data acquisition and processing system is connected to the temperature measuring element and is used to collect temperature data at different depths at preset time intervals during the data acquisition period. Based on the characteristics of temperature data at different depths changing over time, the volumetric water content of the soil at different depths around the metal pile is obtained.

2. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 1, characterized in that: The temperature measuring element includes a distributed temperature measuring optical fiber extending along the axial direction of the metal pile, or a multi-point temperature measuring array arranged along the axial direction of the metal pile.

3. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 2, characterized in that: The cavity formed by the inner wall of the hollow steel pipe is the receiving cavity.

4. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 3, characterized in that: The heating element includes multiple heating cables, which are closely attached to the inner wall of the steel pipe and extend along the axial direction of the steel pipe. The multiple heating cables are evenly spaced in the circumferential direction of the steel pipe.

5. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 4, characterized in that: The multi-point temperature measurement array includes multiple temperature sensors that are evenly spaced along the axial direction of the steel pipe; the number of multi-point temperature measurement arrays is set to multiple sets, and the multiple sets of multi-point temperature measurement arrays are evenly spaced along the circumference of the steel pipe.

6. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 5, characterized in that: The number of groups in the multi-point temperature measurement array is the same as the number of heating cables, and the temperature sensor is fixed on the inner wall of the steel pipe and is spaced apart from the heating cables.

7. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 6, characterized in that: The temperature sensor and the heating cable are respectively fixed to the inner wall of the steel pipe with tape.

8. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 3, characterized in that: The heating element includes an AC induction coil, which is fixed to the sealed structure and suspended at the axis of the steel pipe. The power source provides high-frequency AC power to the AC induction coil, which generates an alternating magnetic field after being energized and induces eddy currents in the steel pipe wall to generate heat and raise the temperature of the steel pipe.

9. The smart pile for measuring soil moisture content based on the active thermal pulse principle according to claim 1 or 2, characterized in that: The solid steel column has a channel inside, and the inner cavity of the channel forms the receiving cavity. The size of the receiving cavity is adapted to the size of the temperature measuring element.

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