A system for soil in-situ stress detection and method thereof

Abstract

The application belongs to the technical field of soil mechanics and agricultural mechanization engineering, and discloses a system and a method for in-situ stress detection of soil, which comprises a stress sensing probe and a mounting device; when the stress sensing probe is buried in the soil body through the mounting device, the stress of the soil body caused by external load is transmitted to the internal liquid through the flexible package, so that the internal pressure change is proportional to the average normal stress of the soil body plane, the formula is met, and the in-situ measurement of the stress of the soil body is realized; the application further provides a matching mounting device and method, directional drilling, reaming and smooth embedding of the sensor are realized through the mounting support, the installation auxiliary pipe and the support leveling mechanism, installation disturbance is reduced, the measurement accuracy and long-term stability are improved, and the laying efficiency and angle control ability of the sensor under complex farmland topography are improved through the standardized mounting device.

Description

Technical Field

[0001] This invention relates to the fields of soil mechanics and agricultural mechanization engineering technology, specifically to a system and method for in-situ soil stress detection. Background Technology

[0002] In the field of modern agricultural mechanization engineering, quantitative analysis of the stress distribution, strength evolution, and deformation characteristics of farmland soil under vehicle operation loads is a core prerequisite for scientifically assessing ground passability and the risk of deep subsoil compaction. Soil is not only the physical support matrix for crop growth but also a key medium for water transport and nutrient cycling. However, excessive compaction caused by agricultural machinery operations can damage the soil's pore structure, leading to increased bulk density and decreased permeability, inhibiting root penetration into deeper layers, and reducing the crop's ability to obtain available water and nutrients. Therefore, in order to ensure the dynamic stability of farmland soil mechanical properties, it is essential to establish a deep physical understanding of its in-situ bearing capacity and elastoplastic deformation characteristics under complex vehicle loads. Currently, commonly used in-situ measurement methods at home and abroad are mainly divided into two categories: "active" and "passive." Active pressure gauges: These devices calculate soil mechanical parameters by actively expanding a flexible membrane inside the borehole and monitoring the pressure-deformation curve. However, their mechanical models are mainly based on the assumption of a static, isotropic stress field, which has obvious limitations in capturing transient, anisotropic dynamic stresses such as those experienced by agricultural machinery, and is difficult to reflect complex real-time operating conditions. Passive fluid inclusion sensors: These probes passively sense pressure changes caused by external stress by filling a constant amount of fluid, which is conceptually more in line with the needs of dynamic monitoring. However, for a long time, the mechanical mapping relationship between the fluid pressure inside the sensor and the actual far-field stress of the soil has not been rigorous, resulting in data interpretation that is highly dependent on empirical parameters, the physical meaning of the measurement results is ambiguous, and the reliability is difficult to meet the needs of precision agricultural monitoring.

[0003] The existing technology has the following main problems: The physical mapping theory is incomplete: There is a lack of a universal theoretical framework to accurately describe the coupling relationship between the internal fluid pressure of the passive probe and the anisotropic stress field of the soil, which often results in the measurement results being unable to quantitatively reproduce the true stress state of the soil. Difficulty in analyzing the interface interaction mechanism: Since the complex interaction between the soil and the probe is not yet fully understood, the measured data often has significant deviations under stress concentration or large soil deformation, making it difficult to achieve high-precision data inversion. Low accuracy of in-situ deployment: The installation process of existing probes lacks standardized guidance and support devices. The process of inserting the probe into the soil can easily disturb the in-situ soil structure and make it difficult to ensure the accuracy of the probe at the preset monitoring depth and spatial angle, which restricts the accuracy and stability of the monitoring data. Summary of the Invention

[0004] The purpose of this invention is to provide a system and method for in-situ stress detection in soil, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a system for in-situ soil stress detection, comprising a stress sensing probe and an installation device, wherein the stress sensing probe consists of an insertion tip, a flexible hose, a main sensor pipe, a connector, a tee, a valve, a two-way valve, and a pressure sensor; One end of the hose is inserted with a soil-penetrating tip, and the other end of the hose is connected to one end of the sensor main tube. The other end of the sensor main tube is connected to a tee via a connector. One end of the tee is connected to one end of the valve, and the pressure sensor is fixedly installed at the other end of the tee. The hose is filled with an incompressible liquid and connected to a pressure sensor via a main sensor pipe. This allows for the measurement of the internal pressure of the hose when the soil is subjected to external loads. The internal pressure of the liquid is directly proportional to the average plane normal stress of the soil, satisfying the formula... in, For the pressure inside the package, , The mean normal stress in the plane of the soil. Poisson's ratio of the soil; The installation device consists of an installation auxiliary pipe, four support height adjustment seats, an installation bracket, and a level. The four height adjustment seats of the support are fixedly installed on both sides of the bottom of the mounting bracket, the level is fixedly installed on the top of the mounting bracket, and the mounting auxiliary tube is installed inside the mounting bracket through a clamp.

[0006] Furthermore, the incompressible liquid is degassed pure water, which is a liquid medium with stable density and negligible compressibility.

[0007] Furthermore, the elastic modulus of the hose is on the same order of magnitude as the stiffness of the soil being tested, meaning that "the presence of the membrane does not affect the measurement pressure only when the stiffness of the membrane and the soil are similar".

[0008] Furthermore, the soil-penetrating tip is made of metal, engineering plastics, and composite materials, and its front end is tapered, which is beneficial for soil penetration.

[0009] Furthermore, the stress sensing probe also includes a water storage pipe and a water injection rod connected to the hose. One end of the water storage pipe is connected to a valve through a two-way valve, and the water injection rod is fixedly installed at the other end of the water storage pipe. It is used to replenish degassed pure water during installation and maintenance, and to achieve venting and sealing through the cooperation of the valve and the two-way valve.

[0010] Furthermore, the pressure sensor is connected to a data acquisition device via a cable, and the data acquisition device is a wired recorder.

[0011] Furthermore, the mounting bracket is a frame structure used to define the direction and position of the stress sensing probe entering the soil, and a guide hole is provided inside the mounting bracket; the installation auxiliary tube is arranged along the direction of the guide hole inside the mounting bracket to guide the drilling and sensor insertion direction.

[0012] A method for in-situ stress detection in soil includes the following steps: S1. Determine the stress sensing probe placement point on the soil surface according to the monitoring requirements, move the mounting bracket to the placement point, and keep the mounting bracket horizontal by adjusting the support height adjustment seat. S2. Fix the installation auxiliary tube in the guide hole inside the installation bracket, and drill a directional hole in the predetermined direction to form an inlet hole that matches the length of the hose. S3. By installing an auxiliary tube to enlarge the hole, the hole wall is made smooth and the fit clearance between the hole diameter and the outer diameter of the stress sensing probe is maintained, so as to improve the stability of the surrounding soil after the stress sensing probe is inserted into the soil. S4. Slowly insert the stress sensing probe into the hole along the direction of the installation auxiliary pipe. During the insertion process, lubricate by continuously injecting liquid to reduce frictional resistance and soil disturbance, and ensure that the tip of the stress sensing probe is at the target depth. S5. After the stress sensing probe is installed in place, remove the installation auxiliary pipe, close the valve to maintain a seal, and connect the pressure sensor to the data acquisition device to collect the incompressible liquid pressure signal inside the hose in real time. Then, calculate the average plane normal stress of the soil according to the formula. S6. When the sensor probe is embedded in the soil, the soil generates principal stress under external loads. , The stress is transmitted to the hose through the soil-to-membrane interface, causing changes in its cross-sectional shape and internal fluid pressure. Since the internal fluid is incompressible degassed pure water, the hose volume remains constant, so the change in the average soil stress is directly converted into a change in internal pressure. The pressure inside the hose is connected to a pressure sensor via a tee, allowing for real-time signal acquisition and transmission to a data acquisition device. Based on theoretical relationships: in, The pressure inside the hose. Poisson's ratio of soil Let be the average normal stress in the soil plane; this formula shows that the measured hose pressure is proportional to the average normal stress in the soil. S7, the water storage pipe and water injection rod are used to replenish degassed pure water during installation and maintenance to ensure that there are no air bubbles in the package to maintain the incompressibility assumption.

[0013] Furthermore, the drilling operation can be completed using manual drilling tools, portable electric drilling rigs, or other drilling devices adapted to different soil types, in order to reduce installation disturbance and ensure the quality of sensor installation.

[0014] Compared with the prior art, the beneficial effects of the present invention are: Internal pressure of the hose Normal stress in the plane of soil , The relationship is given by the formula Quantitatively, this formula, based on the principle of volume conservation of incompressible liquids, directly converts soil stress changes into pressure changes within the flexible tube, establishing a direct physical mapping relationship between the pressure of the passive fluid probe and the anisotropic stress field of the soil. This simplifies the conversion process and eliminates interference from volume changes. The formula is applicable to plane stress states and is derived from the Poisson's ratio of the soil. Incorporating anisotropic effects ( It reflects the elastic anisotropy of soil, and therefore plays a role in quantitatively restoring the true stress state of soil. The efficient coupling between the flexible hose and the soil stress field reduces the complexity of the interaction between the soil and the probe. Even under stress concentration or large soil deformation, efficient coupling can be achieved, thus reducing measurement data deviation and improving data inversion accuracy, thereby enhancing the accuracy of monitoring results. The internal filling with degassed pure water (incompressible) eliminates volume change interference, allowing pressure measurements to directly reflect the soil stress state and reducing the influence of intermediate variables. The pressure sensor is connected to the flexible hose via a tee, acquiring pressure signals in real time and then processing them using a formula. Directly convert to average normal stress in the soil plane This avoids the complex intermediate variables (such as soil deformation modulus and pore water pressure) in the "pressure-stress" conversion of traditional methods, realizes the linearization and standardization of data interpretation, further improves the measurement accuracy, ensures the accurate monitoring of soil stress state, and thus achieves high-precision data inversion. The stress sensing probe of this invention realizes in-situ monitoring of soil stress state through "pressure inside the hose - average stress", and has the characteristics of clear principle, sensitive response and simple calibration. The sensor is successfully installed by using a mounting bracket, auxiliary pipe, and leveling mechanism, enabling directional drilling, hole enlargement, and installation. This reduces installation disturbance, improves measurement accuracy and long-term stability, and allows the sensor to continuously and accurately monitor soil stress. The guiding and leveling structure of the mounting bracket allows for precise deployment of the sensor under various terrain and soil conditions. Standardized installation devices enhance the sensor's deployment efficiency and angle control in complex farmland terrain, ensuring the accuracy of the probe at the preset monitoring depth and spatial angle. This achieves in-situ monitoring of soil stress, enhances data accuracy and stability, and improves the long-term effectiveness of the system. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the stress sensing probe structure of the present invention; Figure 2 A schematic diagram of the hose filled with deaerated pure water according to the present invention; Figure 3 This is a schematic diagram of the installation device structure of the present invention.

[0016] Explanation of reference numerals in the attached figures: 1. Soil entry tip; 2. Hose; 3. Sensor main pipe; 4. Connector; 5. T-joint; 6. Valve; 7. Two-way valve; 8. Water storage pipe; 9. Water injection rod; 10. Pressure sensor; 11. Installation auxiliary pipe; 12. Support height adjustment seat; 13. Mounting bracket; 14. Level. Detailed Implementation

[0017] The technical solution of the present invention will now be described in detail through specific embodiments.

[0018] Please see Figure 1-3 The present invention provides a system for in-situ stress detection in soil, including a stress sensing probe and an installation device. The stress sensing probe consists of an entry tip 1, a flexible hose 2, a sensor main pipe 3, a connector 4, a tee 5, a valve 6, a two-way valve 7, and a pressure sensor 10. One end of the hose 2 is connected to the soil-penetrating tip 1, and the other end of the hose 2 is connected to one end of the sensor main pipe 3. The other end of the sensor main pipe 3 is connected to a tee 5 through a connector 4. One end of the tee 5 is connected to one end of the valve 6. The pressure sensor 10 is fixedly installed at the other end of the tee 5. The stress sensing probe also includes a water storage pipe 8 and a water injection rod 9 connected to the hose 2. One end of the water storage pipe 8 is connected to the valve 6 through a two-way valve 7. The water injection rod 9 is fixedly installed at the other end of the water storage pipe 8 and is used to replenish incompressible liquid during installation and maintenance. It also achieves venting and sealing through the cooperation of the valve 6 and the two-way valve 7. By using the water injection rod 9 and valve 6 in combination, this design can reduce pressure measurement errors caused by air ingress during installation and maintenance by replenishing degassed pure water to vent air and ensure a seal. This maintains the pressure consistency inside and outside the stress sensing probe and improves the stability and reliability of the measurement. Among them, the elastic modulus of the flexible hose 2 is on the same order of magnitude as the stiffness of the soil to be measured, that is, "only when the stiffness of the membrane and the soil are similar, the presence of the membrane will not affect the measurement pressure". The hose 2 is filled with an incompressible liquid, which is degassed pure water, as the incompressible working medium. Degassed pure water is a liquid medium with stable density and negligible compressibility. It is connected to the pressure sensor 10 through the sensor main pipe 3 to measure the internal pressure of the hose 2 when the soil is subjected to external loads. Therefore, the internal pressure of the hose 2 will change. This change directly reflects the average normal stress in the plane of the soil. Thus, this design of the hose 2 indirectly measures the soil stress, thereby achieving the purpose of calculating the average normal stress of the soil by measuring the internal pressure of the hose 2. The internal pressure of the liquid is directly proportional to the average plane normal stress of the soil, satisfying the formula... in, The internal pressure of hose 2 , The mean normal stress in the plane of the soil. Poisson's ratio of the soil; The soil-penetrating tip 1 is made of metal, engineering plastics and composite materials, and the front end is conical, which is conducive to the structure of soil penetration. This design can effectively reduce the disturbance to the soil during installation and ensure that the front end of the stress sensing probe can be smoothly penetrated into the soil to the target depth. Therefore, it can ensure the consistency between the stress sensing probe and the principal stress direction of the soil during installation, thereby improving the accuracy of the measurement results. The pressure sensor 10 is connected to the data acquisition device via a cable, and the data acquisition device is a wired recorder; The installation device consists of an installation auxiliary pipe 11, four support height adjustment seats 12, an installation bracket 13, and a level 14. Four support height adjustment seats 12 are fixedly installed on both sides of the bottom of the mounting bracket 13, and a level 14 is fixedly installed on the top of the mounting bracket 13. The installation auxiliary tube 11 is installed inside the mounting bracket 13 through a clamp. The mounting bracket 13 is a frame structure used to limit the direction and position of the stress sensing probe in the soil. The mounting bracket 13 has a guide hole inside. The level 14 works in conjunction with the support height adjustment seats 12 to correct the levelness of the mounting bracket 13, so as to ensure that the sensor's soil entry angle is consistent with the predetermined direction, thereby reducing the pressure measurement error caused by the deviation of the horizontal plane and improving the measurement accuracy. The installation auxiliary tube 11 is set along the direction of the guide hole inside the mounting bracket 13 to guide the drilling and sensor insertion direction.

[0019] A method for in-situ stress detection in soil includes the following steps: S1. Determine the stress sensing probe placement point on the soil surface according to the monitoring requirements, move the mounting bracket 13 to the placement point, and keep the mounting bracket 13 horizontal by adjusting the support height adjustment seat 12. S2. Fix the installation auxiliary pipe 11 in the guide hole inside the installation bracket 13, and perform directional drilling in the predetermined direction. The drilling operation can be completed by manual drilling tools, portable electric drilling machines, or other drilling devices that are suitable for soil types, so as to reduce installation disturbance and ensure the sensor installation quality, and form an entry hole that is compatible with the length of the hose 2. S3. By installing auxiliary tube 11, the hole is enlarged to make the hole wall smooth and maintain the matching gap between the hole diameter and the outer diameter of the stress sensing probe, so as to improve the stability of the surrounding soil after the stress sensing probe is inserted into the soil. S4. Slowly insert the stress sensing probe into the hole along the direction of the installation auxiliary pipe 11. During the insertion process, lubricate by continuously injecting liquid to reduce frictional resistance and soil disturbance, and ensure that the front end of the stress sensing probe is at the target depth. S5. After the stress sensing probe is installed in place, remove the installation auxiliary pipe 11, close valve 6 to maintain a seal, and connect pressure sensor 11 to the data acquisition device to collect the incompressible liquid pressure signal inside hose 2 in real time, and calculate the average normal stress of the soil in plane according to the formula: S6. When the stress sensing probe is embedded in the soil, the soil generates principal stresses under external loads. , The stress is transmitted to the hose 2 through the soil-to-membrane interface, causing changes in its cross-sectional shape and internal fluid pressure. Since the internal fluid is incompressible degassed pure water, the volume of the hose 2 remains constant. Therefore, the change in the average stress of the soil is directly converted into a change in internal pressure. The pressure inside hose 2 is connected to pressure sensor 10 via tee 5, and the signal is collected in real time and transmitted to the data acquisition device. Based on theoretical relationships: in, The pressure inside the hose. Poisson's ratio of soil Let be the average normal stress in the soil plane; this formula shows that the measured hose pressure is proportional to the average normal stress in the soil. It should be noted that the complete mechanical derivation of the working principle of the stress sensing probe is as follows: Based on the linear elastic solution, on the surface of the flexible tube... At this point, the radial displacements in two orthogonal directions can be written as: ① ② in, Corresponding to the direction θ=π / 2, Corresponding to the direction θ=0, The initial cross-sectional radius of the hose; , These represent the principal stresses of the soil transport field in the x1 and x2 directions, respectively. This refers to the hydrostatic pressure inside the hose; It is the soil shear modulus; Poisson's ratio of the soil; Under plane strain, the cross-section of the flexible tube changes from approximately circular to elliptical, and its relative area change can be expressed as: ③ in, For the surface of the hose in the direction radial displacement, For the surface of the hose in the direction radial displacement, The initial cross-sectional radius of the hose is... This represents the change in hose volume. This represents the initial volume of the hose; Under the limited condition that the hose 2 is filled with incompressible liquid, the total volume of the hose 2 remains constant: ④ Substituting ③ into ④ yields the displacement constraint equations corresponding to constant volume: ⑤ Substituting the displacement expression, we obtain the following about The quadratic equation: ⑥ From equations ① and ②, we have: ⑦ Right now: in, The sum of stresses is defined as follows: ; Substituting the above results into equation ⑤ and eliminating common factors, we finally obtain the information about... Quadratic algebraic equations: ⑧ in Equation ⑧ is the exact algebraic relationship for incompressible fluids. When the hose deformation is large or the soil anisotropy is strong, this equation should be used to solve the problem. And can be solved using numerical methods or table lookup methods; When the hose deformation is very small Compared to (Ignoreable), Equation ⑤ is reduced to a linear term of zero: 9 Substituting ① and ②, we get: in, For soil shear modulus, The sum of stresses is defined as follows: ; Therefore, we obtain the commonly used congruent closed relation: ⑩ in, The average normal stress in the plane; Equation ⑩ is the core theoretical basis supporting the technical solution of this patent. The pressure measured inside Directly with the average normal stress of the soil and the Poisson's ratio of the soil matrix Proportional; The cross-section of the flexible hose changes from a circle to an ellipse, with its major and minor axes being: ⑪ in, The long semi-axis of the cross-section after the hose deforms. This refers to the short half-axis of the cross-section after the hose deforms; The ratio of the major axis to the minor axis; The following can be obtained using a first-order expansion under the small deformation approximation: ⑫ This formula explains the ratio of the major axis to the minor axis. Difference between principal stresses There is a linear proportional relationship (the coefficient includes soil parameters). Therefore, by measuring And combined with soil shear modulus Compared with Poisson Inverse principal stress difference; To reduce the pressure inside the hose Converted to average soil stress The following indoor calibration procedure is adopted: In a controlled laboratory environment, remolded soil samples with high mechanical consistency were prepared based on the key physical properties of the soil layers at the test site (including dry density, mass moisture content and particle size distribution). At the same time, a strict vacuum degassing and grouting procedure was performed on the stress sensing probe to ensure that the hose was filled with completely degassed pure water free of air bubbles, so as to maintain the theoretical assumption of the incompressibility of the fluid inside the system. Place the sensor in an isotropic pressure apparatus (or triaxial) and apply isotropic static pressure in stages. (make ), the steady-state record corresponding to ; Under isotropic conditions, theoretical relation ⑩ is given. Fitting linear coefficients using experimental data (Right now The equivalent Poisson's ratio is obtained from the following formula. : ⑬ in, For fluid compressibility Pa−1, the main case is k→0 (incompressible); 4) On-site measurement Then, the average stress is calculated using the following formula: ⑭ 5) If it is necessary to obtain the principal stress difference simultaneously Measure the ratio of the major and minor axes of the cross section. And invert using the following formula (which requires a given or measured value). ): ⑮ S7. Degassed pure water is replenished through the water storage pipe 8 and the water injection rod 9 during installation and maintenance to ensure that there are no air bubbles in the package to maintain the incompressibility assumption.

[0020] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A system for in-situ stress detection of soil, characterized by: It includes a stress sensing probe and an installation device. The stress sensing probe consists of an insertion tip (1), a flexible hose (2), a sensor main pipe (3), a connector (4), a tee (5), a valve (6), a two-way valve (7), and a pressure sensor (10). One end of the hose (2) is inserted with a soil-penetrating tip (1), and the other end of the hose (2) is connected to one end of the sensor main pipe (3). The other end of the sensor main pipe (3) is connected to a tee (5) through a connector (4). One end of the tee (5) is connected to one end of the valve (6), and the pressure sensor (10) is fixedly installed at the other end of the tee (5). The hose (2) is filled with incompressible liquid and is connected to the pressure sensor (10) through the sensor main pipe (3) to measure the internal pressure of the hose (2) when the soil is subjected to external load. The internal pressure of the liquid is proportional to the average normal stress in the plane of the soil, satisfying the formula... wherein, is the internal pressure of the hose (2), , is the average normal stress of the soil plane, is the Poisson's ratio of the soil; The installation device consists of an installation auxiliary pipe (11), four support height adjustment seats (12), an installation bracket (13), and a level (14); The four support height adjustment seats (12) are fixedly installed on both sides of the bottom of the mounting bracket (13), the level (14) is fixedly installed on the top of the mounting bracket (13), and the mounting auxiliary tube (11) is installed inside the mounting bracket (13) through a clamp.

2. A system for in-situ stress detection of soil according to claim 1, characterized in that, The incompressible liquid is degassed pure water, which is a liquid medium with stable density and negligible compressibility.

3. The system for in-situ stress detection of soil according to claim 1, wherein, The elastic modulus of the hose (2) is on the same order of magnitude as the stiffness of the soil to be measured, that is, "only when the stiffness of the membrane and the soil are similar, the presence of the membrane will not affect the measurement pressure".

4. The system for in-situ stress detection of soil according to claim 1, wherein, The soil-penetrating tip (1) is made of metal, engineering plastics and composite materials, and the front end is conical, which is conducive to the structure of soil penetration.

5. The system for in-situ stress detection of soil according to claim 1, wherein, The stress sensing probe also includes a water storage pipe (8) and a water injection rod (9) connected to the hose (2). One end of the water storage pipe (8) is connected to the valve (6) through a two-way valve (7). The water injection rod (9) is fixedly installed at the other end of the water storage pipe (8) to replenish degassed pure water during installation and maintenance, and to achieve venting and sealing through the cooperation of the valve (6) and the two-way valve (7).

6. The system for in-situ stress detection of soil according to claim 1, wherein, The pressure sensor (10) is connected to the data acquisition device via a cable, and the data acquisition device is a wired recorder.

7. The system for in-situ stress detection of soil according to claim 1, wherein, The mounting bracket (13) is a frame structure used to define the direction and position of the stress sensing probe in the soil. The mounting bracket (13) has a guide hole inside. The installation auxiliary tube (11) is set along the direction of the guide hole inside the mounting bracket (13) to guide the drilling and sensor insertion direction.

8. A method for in-situ soil stress detection, for performing a system for in-situ soil stress detection according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Determine the stress sensing probe placement point on the soil surface according to the monitoring requirements, move the mounting bracket (13) to the placement point, and keep the mounting bracket (13) horizontal by adjusting the support height adjustment seat (12). S2. Fix the installation auxiliary tube (11) in the guide hole inside the installation bracket (13), and drill a hole in a predetermined direction to form an inlet hole that matches the length of the hose (2). S3. By installing the auxiliary tube (11), the hole is enlarged to make the hole wall smooth and maintain the matching gap between the hole diameter and the outer diameter of the stress sensing probe, so as to improve the stability of the surrounding soil after the stress sensing probe is inserted into the soil. S4. Slowly insert the stress sensing probe into the hole along the direction of the installation auxiliary pipe (11). During the insertion process, lubricate by continuously injecting liquid to reduce frictional resistance and soil disturbance, and ensure that the front end of the stress sensing probe (1) is at the target depth. S5. After the stress sensing probe is installed, remove the installation auxiliary pipe (11), close the valve (6) to maintain a seal, and connect the pressure sensor (11) to the data acquisition device to collect the incompressible liquid pressure signal inside the hose (2) in real time, and calculate the average normal stress of the soil in plane according to the formula: S6. When the sensor probe is embedded in the soil, the soil generates principal stress under external loads. , The stress is transmitted to the hose (2) through the soil-to-membrane interface, causing changes in its cross-sectional shape and internal fluid pressure. Since the internal fluid is incompressible degassed pure water, the volume of the hose (2) remains constant, so the change in the average stress of the soil is directly converted into a change in internal pressure. The internal pressure of the hose (2) is connected to the pressure sensor (10) through the tee (5), and the signal is collected in real time and transmitted to the data acquisition device. According to the theoretical relationship: in, The pressure inside the hose. Poisson's ratio of soil Let be the average normal stress in the soil plane; this formula shows that the measured hose pressure is proportional to the average normal stress in the soil. S7, the water storage pipe (8) and the water injection rod (9) are used to replenish degassed pure water during installation and maintenance to ensure that there are no air bubbles in the package to maintain the incompressibility assumption.

9. A method for in-situ stress detection in soil according to claim 8, characterized in that, The drilling operation can be completed using manual drilling tools, portable electric drilling rigs, or other drilling devices adapted to different soil types, in order to reduce installation disturbance and ensure the quality of sensor installation.

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