High-precision acquisition method, sensor and calibration equipment for wall deformation

Abstract

This invention provides a high-precision acquisition method, sensor, and calibration device for borehole wall deformation, comprising: calibrating the sensor; installing the calibrated sensor onto an ultra-long horizontal exploration borehole wall strain capture test section; acquiring borehole wall photographs and borehole diameter shapes at different depths; selecting at least three test points at a specified depth, in different directions, without structural surfaces or drill marks, based on the borehole wall photographs and borehole diameter shapes; pushing the ultra-long horizontal exploration borehole wall strain capture test section to the depth of the test points; pressing the sensor onto the test points; releasing the rock core at the test points, and continuously acquiring borehole wall strain change data through the sensor during this process. This invention has the functions of withstanding high temperature and high pressure, acquiring high-precision strain and temperature change data of the borehole wall, and providing a strain correction method to ensure the accuracy of the acquired data.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, specifically to a high-precision acquisition method, sensor, and calibration equipment for wall deformation of ultra-long horizontal exploration boreholes. Background Technology

[0002] High ground stress zones are a common and complex geological condition encountered during tunnel construction. High ground stress refers to the stress experienced by deeply buried underground rock strata, which typically has a significant impact on both tunnel construction and operation. The existence of high ground stress zones is crucial for tunnel construction, primarily in the following aspects: First, it affects tunnel stability: Rocks in high ground stress zones are subjected to greater ground stress, making them prone to deformation and damage. This deformation and damage directly affects tunnel stability and may even lead to serious accidents such as tunnel collapse. Therefore, the impact of high ground stress must be fully considered during tunnel construction, and corresponding engineering measures must be taken to ensure tunnel stability. Second, it can trigger geological disasters: High ground stress zones have a higher risk of geological disasters. For example, for hard and brittle rock masses, high ground stress may trigger rock bursts; for soft rock, it may lead to disasters such as large deformation of the tunnel chamber. These disasters not only affect the tunnel construction progress and quality but may also threaten the safety of construction personnel and equipment. Therefore, when constructing tunnels in high ground stress zones, it is essential to strengthen the prevention and control of geological disasters.

[0003] Stress relief methods are two in-situ stress testing methods recommended by the International Committee on Testing Techniques for Rock Mechanics. These methods are based on the relationship between borehole wall stress and in-situ stress in a three-dimensional cylindrical borehole. In-situ stress is calculated by measuring strain at the borehole wall and rock mass deformation parameters. Key aspects of ensuring the accuracy of in-situ stress testing include accurately acquiring borehole wall deformation and temperature changes during drilling, overcoming the complex high-temperature and high-pressure testing environment of deep boreholes, and preventing sensor damage caused by borehole wall roughness.

[0004] Ultra-long horizontal exploration borehole technology combines horizontal directional drilling and ultra-long-distance drilling. Horizontal directional drilling utilizes directional drill rods and guide bits to drill a certain distance in a specific direction, achieving directional borehole extension. Ultra-long-distance drilling, on the other hand, uses specially designed drilling tools and processes to achieve long-distance borehole extension. The combination of these two technologies enables ultra-long horizontal exploration boreholes to accurately detect geological conditions over long distances, significantly improving the accuracy and efficiency of exploration. The technological advantages of ultra-long horizontal exploration boreholes are mainly reflected in the following aspects:

[0005] (1) Long-distance, high-precision exploration: Through advanced navigation systems and mechanical equipment, ultra-long horizontal exploration holes can achieve long-distance, high-precision geological drilling, providing detailed geological data for tunnel design and construction.

[0006] (2) Comprehensive geological information: This technology can reveal information on geological structure, soil and rock properties and groundwater conditions, providing comprehensive and accurate geological information for tunnel engineering.

[0007] (3) Early warning of geological disasters: By analyzing the collected geological data, ultra-long horizontal exploration holes can provide early warning of geological disasters at the tunnel construction face.

[0008] (4) Predict the geological conditions ahead, promptly identify and resolve potential geological disaster risks, and ensure construction safety.

[0009] Currently, the methods and equipment for in-situ testing of geostress in ultra-long horizontal exploration boreholes are still immature. This is mainly because, firstly, the drilling process for ultra-long horizontal boreholes uses small drill bits to create large boreholes, resulting in uneven borehole walls. This places higher demands on the protection and testing accuracy of the wall strain acquisition sensors. Secondly, because drilling fluid does not completely fill the borehole in some sections, the testing accuracy is affected by the heat generated by the drill bit breaking through the rock. Furthermore, conducting geostress testing in ultra-long horizontal boreholes requires pushing the sensor against the borehole wall for data acquisition; therefore, the strain generated by this pushing pressure must be eliminated to obtain accurate wall strain data. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the purpose of this invention is to provide a high-precision acquisition method, sensor, and calibration equipment for wall deformation in ultra-long horizontal exploration boreholes.

[0011] According to one aspect of the present invention, a method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes is provided, comprising:

[0012] The pressure-type sensor was calibrated using calibration equipment to confirm its linearity and hysteresis. The conversion coefficient between the sensor and direct measurement with strain gauges was calibrated, as well as the conversion coefficient between pressure-type and adhesive-type measurement methods.

[0013] The sensor is mounted onto the test section for wall strain capture;

[0014] Obtain images of the borehole wall and borehole diameter shape at different depths during drilling;

[0015] Based on the hole wall and hole diameter shape images, at least three test points with no unstructured surfaces and no drill marks in different directions are selected at a specified depth;

[0016] Push the test section to the depth of the test point;

[0017] Press the sensor onto the test point;

[0018] Core samples are drilled using the test sub to relieve stress at the test points. During this process, the sensor continuously collects data on borehole wall strain changes, and the final measurement value is obtained through the calibrated conversion coefficient.

[0019] Preferably, calibrating the press-type sensor to confirm its linearity and hysteresis includes:

[0020] Place the sensor into the calibration device;

[0021] The calibration device is used to press the sensor;

[0022] After each press, the calibration device is operated to load and unload the sensor;

[0023] Collect data points on strain changes during the loading and unloading process;

[0024] Based on the data points of the strain change, the loading and unloading linearity and loading and unloading hysteresis of the sensor are evaluated, and the maximum number of tests for the sensor is determined.

[0025] Preferably, the linearity of sensor loading and unloading is evaluated based on the data points of the strain change, specifically as follows:

[0026] The least squares method was used to fit the data points of the loading and unloading process to obtain the loading and unloading curve fitting formula and the corresponding R-squared value.

[0027] The R-squared value is judged as follows: if the R-squared value is less than the lowest value of the threshold range, the linearity level is judged as poor; if the R-squared value is greater than the highest value of the threshold range, the linearity level is judged as excellent; if the R-squared value is within the threshold range, the linearity level is judged as good.

[0028] Preferably, the loading / unloading hysteresis is evaluated based on the data points of the strain change, specifically as follows:

[0029] The least squares method was used to fit the data points of the loading and unloading process to obtain the loading and unloading curve fitting formula, and thus the loading and unloading curves were obtained.

[0030] The hysteresis degree of the sensor is quantitatively evaluated based on the loading and unloading curves. The hysteresis degree includes an energy-based quantitative evaluation coefficient and an elastic-plastic quantitative evaluation coefficient. The energy-based quantitative evaluation coefficient is the ratio of the area enclosed by the loading curve and the x-axis to the area enclosed by the unloading curve and the x-axis. The elastic-plastic quantitative evaluation coefficient is the ratio of the strain value before loading to the strain value after unloading.

[0031] Preferably, determining the maximum number of tests for the sensor includes:

[0032] During the calibration process, the sensor is loaded and unloaded once each time it is pressed.

[0033] Calculate the loading / unloading linearity and loading / unloading hysteresis for each loading / unloading operation; if either the loading / unloading linearity or the loading / unloading hysteresis exceeds a feasible threshold range, it indicates that the maximum number of tests for the sensor has been reached.

[0034] Preferably, calibrating the conversion coefficient between the sensor and the strain gauge direct measurement includes:

[0035] Based on the actual load applied by the calibration equipment and the data points of strain change collected during the loading and unloading process, the conversion coefficient between the sensor and the strain gauge direct measurement is obtained.

[0036] Preferably, the conversion coefficient between the calibration press-type measurement method and the adhesive-type measurement method includes:

[0037] Inside the calibration equipment, a sensor sheet is attached to the same material and a sensor is fixed.

[0038] Simultaneously, the same pressing force is applied to the sensing sheet and the sensor, and the sensing fit calibration curve under different pressing force conditions is plotted. The horizontal axis of the curve is the pressing force, and the vertical axis is the collected strain value.

[0039] Based on the two adhesion calibration curves, the conversion coefficient between the calibration pressing measurement method and the adhesive measurement method is obtained.

[0040] Preferably, the step of continuously acquiring strain change data of the borehole wall through the sensor and obtaining the final measured value through the calibrated conversion coefficient includes:

[0041] The measured strain value and pressure collected by the sensor are obtained;

[0042] The true strain value = (measured strain value - pressure × b) × a, where a is the conversion coefficient between direct measurement by the sensor and the strain gauge, b is the conversion coefficient between the pressure measurement method and the adhesive measurement method, and the pressure is calculated based on the displacement of the spring inside the sensor.

[0043] According to a second aspect of the present invention, a press-type sensor is provided for the high-precision acquisition method of wall deformation as described in any one of the claims, comprising:

[0044] A protective shell, the front end of which is used to contact the wall surface, the front end being an elastic membrane;

[0045] The sensing element is located inside the protective shell and fixed to the elastic membrane;

[0046] A sheath is attached to the rear end of the protective shell;

[0047] The communication cable is connected to the sensor sheet via a watertight connector inside the sheath.

[0048] A spring, coaxial with the sheath, is embedded within the sheath.

[0049] A displacement sensor is installed inside the sheath to collect the displacement of the spring.

[0050] According to a third aspect of the present invention, a calibration device is provided for the high-precision acquisition method of wall deformation as described in any one of the claims, comprising:

[0051] A container is a sealed space used to house sensors;

[0052] A strain acquisition device is located outside the container and is connected to the sensor via a cable.

[0053] A pressure fitting is located at the top of the container and communicates with the interior of the container;

[0054] A pressurizer, located outside the container, is connected to the pressurization connector;

[0055] A hydraulic digital display is located on the pressure unit;

[0056] A degassing water generator is located at the top of the container and is connected to the interior of the container.

[0057] Compared with the prior art, the embodiments of the present invention have at least one of the following beneficial effects:

[0058] The high-precision acquisition method for wall deformation of ultra-long horizontal exploration boreholes in this embodiment of the invention evaluates the linearity, hysteresis, and deformation resistance of the sensor, which can significantly improve the testing accuracy and stability of the high-precision wall deformation sensor.

[0059] The high-precision acquisition method for wall deformation of ultra-long horizontal exploration boreholes in this embodiment of the invention can conduct multiple tests at different depths in deep boreholes. Compared with traditional deep hole strain acquisition methods, it is more efficient and has a higher test success rate.

[0060] The high-precision acquisition method for wall deformation of ultra-long horizontal exploration boreholes in this embodiment of the invention provides a strain correction method, which improves the measurement accuracy.

[0061] The press-type sensor in this embodiment of the invention can avoid damage from unevenness and sharp corners on irregular borehole walls, has high temperature resistance, high pressure resistance and waterproof function, and can be repeatedly tested in complex deep borehole environments.

[0062] The press-type sensor in this embodiment of the invention can be quickly replaced, is easy to operate, has low cost, and high measurement accuracy. Attached Figure Description

[0063] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0064] Figure 1 This is a flowchart of a high-precision acquisition method for wall deformation of ultra-long horizontal exploration boreholes according to an embodiment of the present invention;

[0065] Figure 2 This is a schematic diagram of the sensor structure in a preferred embodiment of the present invention. In the figure, 11-communication cable, 12-metal sheath, 13-metal protective shell, 14-watertight connector, 15-thread, 16-sensor cable, 17-adhesive, 18-sensor.

[0066] Figure 3 This is a schematic diagram of an indoor sensor calibration device according to a preferred embodiment of the present invention. In the figure, 1-sensor, 2-base, 3-strain acquisition device, 4-cable, 5-pressure container, 6-airless water generator, 7-pipeline, 8-hydraulic digital display, 9-handle, 10-pressurizer, 101-pressurization connector.

[0067] Figure 4 This is a pressure fitting graph for evaluating the linearity of sensor loading and unloading in a preferred embodiment of the present invention.

[0068] Figure 5 This is a graph showing the hysteresis evaluation during the loading and unloading process in a preferred embodiment of the present invention. Detailed Implementation

[0069] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0070] In one embodiment of the present invention, such as Figure 1 As shown, a method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes is provided, including:

[0071] S100 uses calibration equipment to calibrate the press-type sensor, confirm its linearity and hysteresis, calibrate the conversion coefficient between the sensor and direct strain gauge measurement, and calibrate the conversion coefficient between the press-type and adhesive-type measurement methods.

[0072] S200, mounts the sensor onto the test section for wall strain capture;

[0073] S300, acquire images of the hole wall and hole diameter shape at different drilling depths;

[0074] S400, based on the borehole wall and borehole shape image, selects at least three unstructured surfaces and test points without drill marks in different directions at a specified depth;

[0075] S500 pushes the test section to the test point depth;

[0076] S600, press the sensor to the test point;

[0077] The S700 uses a test sub to drill core samples and relieve stress at the test points. During this process, sensors continuously collect data on borehole wall strain changes, and the final measurement value is obtained through the calibrated conversion coefficient.

[0078] In the process of conducting ultra-long horizontal exploration boreholes, ultra-long horizontal exploration boreholes are commonly used. Therefore, in this embodiment, an ultra-long horizontal exploration borehole can be used to mount camera equipment to acquire borehole images. The test sub is a tool integrating sensors and sampling devices, typically installed in the drill string or coiled tubing, and deployed with the drill string into the horizontal section of the well. The ultra-long horizontal exploration borehole can be used to deliver the test sub to the designated test point. The test sub ensures that the sensor is protected during descent, preventing damage, and provides it with power and data acquisition capabilities. Additionally, the test sub's built-in hollow diamond drill bit can relieve stress and extract core samples.

[0079] The above embodiments evaluate the linearity, hysteresis, and deformation resistance of the sensor, which can significantly improve the testing accuracy and stability of the high-precision sensor for wall deformation.

[0080] Because a press-type sensor is used, the measurement method of directly attaching the sensor to the wall, as in existing technology, is changed, which affects the linearity, hysteresis characteristics, and strain values ​​of the measurement to varying degrees. Therefore, the press-type sensor needs to be calibrated. In a preferred embodiment, step S100 involves calibrating the sensor using a calibration device to confirm its linearity and hysteresis. Specifically, the following steps can be taken:

[0081] S101, Place the sensor into the indoor calibration equipment;

[0082] S102, operate the calibrated device to press the sensor;

[0083] S103, after each press, the calibration device is operated to load and unload the sensor;

[0084] S104, collect data points on strain changes during loading and unloading;

[0085] S105 evaluates the sensor's loading and unloading linearity and hysteresis based on data points showing strain changes, and determines its durability and maximum number of tests.

[0086] During loading and unloading, if the relationship between strain and pressure in a strain gauge sensor exhibits strong linearity, it indicates stable sensor performance and a relatively simple conversion between strain and pressure values. In a preferred embodiment, the loading and unloading linearity of the sensor is evaluated using the following method:

[0087] S105.1, Based on the collected data points of the inductive strain, the loading and unloading curve of the equipment is obtained as shown in the figure.

[0088] S105.2, the least squares method is used to fit the data points of the loading and unloading process to obtain the loading and unloading curve fitting formula and the corresponding R-squared value.

[0089] S105.3, if the R-squared value is less than 0.90, the linearity is considered poor; if the R-squared value is greater than 0.95, the linearity is considered excellent; if the R-squared value is between 0.90 and 0.95, the linearity is considered good.

[0090] In some specific embodiments, such as Figure 4 The diagram shown illustrates the linearity assessment of the loading and unloading process in the calibration experiment (asterisks represent the unloading process; the red dashed line is the linear fitting line of the unloading process, in this example its R-squared value is 0.998, indicating excellent linearity; squares represent the loading process; solid lines represent the loading process; black solid lines are the linear fitting lines of the loading process, in this example its R-squared value is 0.91, indicating moderate linearity).

[0091] Hysteresis, also known as hysteresis or delay, refers to the phenomenon where a material's response (e.g., strain) lags behind the change in the driving force (e.g., stress) when subjected to external forces and undergoing loading and unloading processes. This results in the loading and unloading curves not coinciding, forming a closed hysteresis loop. Figure 5 As shown in the figure (this figure is an evaluation diagram of the hysteresis degree during the loading and unloading process of the calibration experiment, where: Aloading - the area of ​​the diagonal stripe in the figure; Aunloading - the area of ​​the gray part in the figure; Ploading - the strain value corresponding to the period before loading; Punloading - the strain value corresponding to the period after unloading). The area of ​​this hysteresis loop represents the energy dissipated by the material during the loading and unloading process, i.e., hysteresis energy or dissipated energy. For high-precision strain sensors, a large hysteresis effect indicates poor test stability of the device. Therefore, during the calibration of the sensor, the occurrence of hysteresis effect should be avoided as much as possible. Therefore, in a preferred embodiment of the present invention, two indicators are used to evaluate the hysteresis degree of the sensor, specifically:

[0092] First, the smaller the area of ​​the hysteresis loop, the less energy is dissipated during loading and unloading, the closer the loading and unloading curves are, the less significant the hysteresis effect, and the better the sensor's stability. Therefore, the following indicators are used to quantitatively evaluate the degree of hysteresis of the sensor:

[0093] ;

[0094] In the formula: S1 is the quantitative evaluation coefficient of sensor hysteresis using the energy method, A 加载 A refers to the area enclosed by the loading curve and the x-axis in the stress-strain curve. 卸载 S1 refers to the area enclosed by the unloading curve and the x-axis in the stress-strain curve. The range of S1 is 0-1. The closer it is to 1, the closer the loading and unloading curves are, the less significant the hysteresis effect, and the better the sensor performance.

[0095] Secondly, another key characteristic of hysteresis is that after unloading, the material cannot completely return to its original state; instead, it exhibits residual deformation. This residual deformation results from plastic or irreversible deformation that occurred during loading. To ensure good testing accuracy and stability of the sensor, the strain values ​​before and after loading and unloading should be kept as consistent as possible. Therefore, the following formula is used to quantitatively evaluate the linearity of the sensor:

[0096] ;

[0097] In the formula: S2 is the quantitative evaluation coefficient of the hysteresis degree of the sensor, and P 加载 P refers to the strain value before loading in the stress-strain curve. 卸载S2 refers to the strain value after unloading in the stress-strain curve. The range of S2 is 0-1. The closer it is to 1, the closer the loading and unloading curves are, the less significant the hysteresis effect is, and the better the sensor performance.

[0098] The sensor needs to undergo multiple tests at different depths and test points downhole. It must be ensured that the sensor does not undergo plastic deformation or experiences minimal plastic deformation after multiple pressure measurements, while maintaining good linearity and preventing further expansion of hysteresis. To evaluate the sensor's resistance to deformation, multiple pressure tests will be conducted, followed by loading and unloading tests on the probe after each pressure measurement. By assessing its hysteresis and linearity, its durability and the maximum number of tests can be determined.

[0099] The above-described embodiments can maintain borehole testing operations within the maximum number of tests without requiring reinstallation on the surface, ensuring operational efficiency. However, during sidewall stress relief operations, the drill bit generates significant heat during rock breaking, causing strain gauges to be affected by temperature stress and high-temperature drift, resulting in a substantial decrease in testing accuracy and large testing errors. This leads to abnormal final stress calculation results and test failure. Therefore, it is essential that the strain acquisition device can acquire temperature changes during the testing process to perform temperature correction on the results. Specifically, in an environment of 0–150 degrees Celsius, the strain value change of the sensor due to temperature rise is measured every 10°C, thus plotting the sensor's temperature-dependent curve for subsequent temperature calibration. Based on the temperature changes obtained from the sensor during stress relief, the temperature-induced strain change is obtained through the temperature calibration curve, and this portion of the strain change is removed from the measured values.

[0100] Furthermore, since the measurement is performed by pressing the sensor firmly against the borehole wall surface, the degree of contact between the sensor and the object being measured can affect the strain measurement results, thus interfering with the obtained borehole wall strain value. Therefore, the strain generated by pressing must be corrected in actual testing. In a preferred embodiment, step S100 involves calibrating the conversion coefficient between the pressing and adhesive measurement methods. Specifically, the following method can be used:

[0101] S106, Conduct calibration tests for the adhesive strain measurement method and the compression strain measurement method, that is, in the calibration equipment, attach a sensor to the same material and fix a sensor.

[0102] Adhesive-mounted sensors are attached to the surface of the object being measured using adhesive, causing the sensor to deform along with the object. In some cases, where adhesive bonding is not possible, pressure is applied to the back of the sensor to firmly press it against the surface of the object, achieving the same deformation. Here, "fixing a sensor" refers to pressing it against the surface of the object.

[0103] S107. Simultaneously apply the same pressing force to both sensors and plot the sensor fit calibration curves under different pressing force conditions. This fit calibration curve refers to the sensor's sensitivity (linearity or hysteresis) to external force loading and unloading, tested by applying different pressing forces to the sensors. The horizontal axis of the curve represents the pressing force, and the vertical axis represents the collected strain value. Generally, the pressure is applied from the rear side of the sensor.

[0104] S108, based on two adhesion calibration curves, obtains the conversion coefficient b between the calibrated press-type measurement method and the adhesive-type measurement method.

[0105] Of course, the measurement data obtained by using sensors and by directly measuring with strain gauges will be different. Therefore, it is necessary to obtain the conversion coefficient 'a' between sensor and strain gauge direct measurement based on the actual load applied by the calibration equipment during the loading and unloading process and the data points of strain change collected.

[0106] Furthermore, in a preferred embodiment, step S700 involves drilling a core sample using a test sub to relieve stress at the test point. During this process, data on borehole wall strain changes are continuously collected using sensors, and the final measured value is obtained through a calibrated conversion coefficient. This can be achieved by the following steps:

[0107] S701, acquires the measured strain value and pressing force collected by the sensor;

[0108] S702, True strain value = (Measured strain value - Pressure × b) × a, where a is the conversion coefficient between direct measurement by the sensor and the strain gauge, b is the conversion coefficient between the pressure measurement method and the adhesive measurement method, and the pressure is calculated based on the displacement of the spring inside the sensor.

[0109] Specifically, the displacement Dt of the spring at any time t during the stress relief process of the sensor attached to the side wall can be obtained through a displacement sensor. Combined with the spring stiffness k, the pressing force at any time t can be obtained.

[0110] The above embodiments take into account the conversion coefficients between strain gauges and sensors, as well as the conversion coefficients between adhesive and press-type measurement methods. This allows strain data obtained from existing press-type sensors to be converted to data from standard adhesive strain gauges, thereby improving measurement accuracy.

[0111] Currently, the BWSRM ground stress testing equipment uses waterproof strain gauges to directly obtain micro-deformations of the wall surface. However, due to only simple protective measures, it is prone to damage after measuring several test points, requiring it to be retrieved and reinstalled on the ground. This replacement process is cumbersome, requiring complete disassembly of the equipment, severely impacting operational efficiency. Therefore, based on the same inventive concept, one embodiment of this invention provides a press-type sensor, specifically, as shown... Figure 2 As shown, a metal protective shell 13 is used. The front end of the shell is for contact with the wall surface, and the rear end is threaded and connected to the metal sheath 12 via a thread 15. Inside the metal protective shell 13, a sensing element 18 is installed. The sensing element 18 is glued to the center of the metal protective shell 13 with adhesive 17. The sensing element cable 16 is integrated with a watertight connector 14, enabling quick insertion. A communication cable 11 passes through the rear metal sheath. One end of the communication cable 11 is connected to the sensing element 18 via the watertight connector 14, and the other end is connected to an external data acquisition device to achieve real-time data acquisition from the sensor. A spring is installed inside the rear metal sheath to measure the applied pressure. The sensor designed in the aforementioned embodiment has the ability to protect the strain gauge from damage by corrosive drilling fluid, rock cuttings, and sharp protrusions on the irregular borehole wall. This design achieves waterproofing, ensuring the smooth operation of the strain gauge. In addition, the sensor exhibits high-temperature resistance and has the advantages of quick insertion, easy installation, and multiple reuses.

[0112] In some specific embodiments, the sensing element can be a KFGS-3-350-D17-11 L3M3S waterproof strain gauge manufactured by Kyowa Electronics Co., Ltd.

[0113] The press-type sensor in this invention embodiment is immune to damage from unevenness and sharp corners on irregular borehole walls. It is resistant to high temperatures, high pressures, and is waterproof, and can be repeatedly tested in complex deep borehole environments. It can be quickly replaced, is easy to operate, low in cost, and has high measurement accuracy.

[0114] Based on the same inventive concept, another embodiment of the present invention provides a specialized indoor calibration device tailored to the characteristics of sensors. For example... Figure 3As shown, the indoor calibration equipment consists of a pressurizer 10, a pressure vessel 5, a degassing water generator 6, piping 7, and a pressurizing connector 101. The pressure vessel 5 is a sealed space for housing the sensor 1, which is placed on a base 2. The strain gauge 3 is located outside the pressure vessel 1 and connected to the sensor 1 via a cable. The pressurizing connector 101 is located on top of the pressure vessel 5 and communicates with the interior of the vessel. The pressurizer 10 is located outside the pressure vessel 5 and connected to the pressurizing connector 101. A hydraulic digital display 8 is located on the pressurizer 10. The degassing water generator 6 is located on top of the pressure vessel 5 and communicates with the interior of the vessel. The pressurizer 10 is connected to the pressure vessel 5 via piping 7 and the pressurizing connector 101, pressurizing the pressure vessel by pressing down on the handle 9. The degassing water generator 6 is connected to an external water source via piping 7 to generate degassing water to fill the entire pressure vessel. After the sensor designed in the above embodiment is placed in the pressure-resistant container 5, it is connected to the strain acquisition device 3 through a line to collect strain changes during the loading and unloading process.

[0115] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. The above preferred features can be used in any combination without conflict.

Claims

1. A method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes, characterized in that, include: The pressure-type sensor was calibrated using calibration equipment to confirm its linearity and hysteresis. The conversion coefficient between the sensor and direct measurement with strain gauges was calibrated, as well as the conversion coefficient between pressure-type and adhesive-type measurement methods. The sensor is mounted onto the test section for wall strain capture; Obtain images of the borehole wall and borehole diameter shape at different depths during drilling; Based on the hole wall and hole diameter shape images, at least three test points with no unstructured surfaces and no drill marks in different directions are selected at a specified depth; Push the test section to the depth of the test point; Press the sensor onto the test point; Core samples are drilled using the aforementioned test sub to relieve stress at the test points. During this process, borehole wall strain change data are continuously collected using the sensor, and the final measured value is obtained through the calibrated conversion coefficient, including: The measured strain value and pressure collected by the sensor are obtained; True strain value = (Measured strain value - Strain value under pressure) b) a is the conversion coefficient between direct measurement by the sensor and the strain gauge, and b is the conversion coefficient between the pressure measurement method and the adhesive measurement method. The pressure is calculated based on the displacement of the spring inside the sensor.

2. The method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes according to claim 1, characterized in that, The calibration of the press-type sensor, confirming its linearity and hysteresis, includes: Place the sensor into the calibration device; The calibration device is used to press the sensor; After each press, the calibration device is operated to load and unload the sensor; Collect data points on strain changes during the loading and unloading process; Based on the data points of the strain change, the loading and unloading linearity and loading and unloading hysteresis of the sensor are evaluated, and the maximum number of tests for the sensor is determined.

3. The method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes according to claim 2, characterized in that, Based on the strain change data points, the sensor loading and unloading linearity is evaluated, specifically as follows: The least squares method was used to fit the data points of the loading and unloading process to obtain the loading and unloading curve fitting formula and the corresponding R-squared value. The R-squared value is judged. If the R-squared value is less than the minimum value of the threshold range, the linearity level is judged to be poor. If the R-squared value is greater than the highest value in the threshold range, the linearity level is judged as excellent; if the R-squared value is within the threshold range, the linearity level is judged as good.

4. The method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes according to claim 2, characterized in that, Based on the data points of the strain change, the degree of loading / unloading hysteresis is evaluated, specifically as follows: The least squares method was used to fit the data points of the loading and unloading process to obtain the loading and unloading curve fitting formula, and thus the loading and unloading curves were obtained. The hysteresis degree of the sensor is quantitatively evaluated based on the loading and unloading curves. The hysteresis degree includes an energy-based quantitative evaluation coefficient and an elastic-plastic quantitative evaluation coefficient. The energy-based quantitative evaluation coefficient is the ratio of the area enclosed by the loading curve and the x-axis to the area enclosed by the unloading curve and the x-axis. The quantitative evaluation coefficient of elasticity and plasticity is the ratio of the strain value before loading to the strain value after unloading.

5. The method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes according to claim 2, characterized in that, Determining the maximum number of tests for the sensor includes: During the calibration process, the sensor is loaded and unloaded once each time it is pressed. Calculate the linearity and hysteresis of each loading / unloading operation; If either the loading / unloading linearity or the loading / unloading hysteresis exceeds the feasible threshold range, it indicates that the maximum number of tests for the sensor has been reached.

6. The method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes according to claim 2, characterized in that, The calibration of the conversion coefficient between the sensor and the strain gauge direct measurement includes: Based on the actual load applied by the calibration equipment and the data points of strain change collected during the loading and unloading process, the conversion coefficient between the sensor and the strain gauge direct measurement is obtained.

7. The method for high-precision acquisition of wall deformation in ultra-long horizontal exploration boreholes according to claim 2, characterized in that, The conversion coefficient between the calibrated press-type and adhesive-type measurement methods includes: Inside the calibration equipment, a sensor sheet is attached to the same material and a sensor is fixed. Simultaneously, the same pressing force is applied to the sensing sheet and the sensor, and the sensing fit calibration curve under different pressing force conditions is plotted. The horizontal axis of the curve is the pressing force, and the vertical axis is the collected strain value. Based on the two adhesion calibration curves, the conversion coefficient between the calibration pressing measurement method and the adhesive measurement method is obtained.

8. A pressure-type sensor, used in the high-precision wall deformation acquisition method according to any one of claims 1-7, characterized in that, include: A protective shell, the front end of which is used to contact the wall surface, the front end being an elastic membrane; The sensing element is located inside the protective shell and fixed to the elastic membrane; A sheath is attached to the rear end of the protective shell; The communication cable is connected to the sensor plate through the sheath using a watertight connector; A spring, coaxial with the sheath, is embedded within the sheath. A displacement sensor is installed inside the sheath to collect the displacement of the spring.

9. A calibration device for the high-precision acquisition method of wall deformation as described in any one of claims 1-7, characterized in that, include: A container is a sealed space used to house sensors; A strain acquisition device is located outside the container and is connected to the sensor by a cable. A pressure fitting is located at the top of the container and communicates with the interior of the container; A pressurizer, located outside the container, is connected to the pressurization connector; A hydraulic digital display is located on the pressure unit; A degassing water generator is located at the top of the container and is connected to the interior of the container.

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