Underground three-way coupling stress test sensor calibration device and installation method thereof

Abstract

The invention discloses an underground three-way coupling stress test sensor calibration device and an installation method thereof, which are used for solving the technical problem that the test result is uncertain due to the fact that complex stress borne by a sensor cannot be completely avoided. The calibration device comprises a protolith sample, a fixed seat and a positioning assembly, a mounting channel penetrating through the interior of the protolith sample is formed in the protolith sample, and the fixed seat is located in the mounting channel; the three sensors to be calibrated are arranged on three adjacent surfaces of the fixed seat, and the three surfaces share one vertex; the mounting channel is filled with a matching material with the same Poisson coefficient as the original rock sample; the positioning assembly comprises a base, a positioning plate, a plurality of supporting columns and two groups of positioning lines; the protolith sample is placed on the base; the positioning plate is positioned above the protolith sample and is connected with the base through a plurality of supporting columns; the upper end and the lower end of the fixed seat are respectively connected with the positioning plate and the base through two groups of positioning lines, so that the central point of the fixed seat is overlapped with the central point of the original rock sample.

Description

Technical Field

[0001] This invention relates to a sensor calibration device, specifically to a calibration device for an underground three-dimensional coupled stress testing sensor and its installation method. Background Technology

[0002] Underground stress is a key mechanical parameter measured at the explosion site. It is used to analyze the propagation and attenuation of stress waves in the underground medium. The basic laws governing the propagation characteristics of stress waves in the underground medium are important bases for evaluating the damage effect on underground structures or the protective capacity of underground structures after explosive loading.

[0003] The test of underground stress is difficult, mainly because: (1) the sensor material and the ground medium material are difficult to match perfectly, and stress concentration inevitably exists at the sensitive surface of the sensor, which leads to the distortion of the measurement results; (2) due to the influence of Poisson coefficient, the solid medium is in a complex stress state, and the stress sensor buried in the ground medium will inevitably be affected by the complex stress, that is, the measured stress in one direction will be affected by the stress in other directions. The calibration of the sensor sensitivity coefficient is mostly carried out under unidirectional stress state, which is inconsistent with the actual use, thus leading to the distortion of the test results; (3) the ground medium is complex and diverse, and the complex stress state of different ground media has different effects on the sensor, which further increases the uncertainty of the test results.

[0004] For the reasons mentioned above, existing technologies reduce the impact of complex stress by changing the structural design of sensors. However, this impact cannot be completely avoided when conducting underground stress tests in practice, resulting in uncertainty in the test results. Summary of the Invention

[0005] The purpose of this invention is to provide a calibration device and installation method for a three-dimensional coupled stress test sensor in underground environments, which solves the technical problem that the test results are uncertain because the complex stresses experienced by the sensor cannot be completely avoided when conducting underground stress tests in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: A calibration device for a triaxially coupled stress testing sensor in underground is characterized by including a rock sample, a fixing base, and a positioning component. The original rock sample has a cubic structure and is provided with an installation channel that runs vertically through its top and bottom ends; the installation channel is a circular channel and its central axis passes through the center of the original rock sample. The mounting base is a cube structure located within the installation channel. The surface of the mounting base has three mounting slots for mounting the sensor to be calibrated. These three slots are distributed on three adjacent faces of the mounting base, sharing a common vertex. The mounting base is aligned with the original rock sample and divides the installation channel into two chambers. The two chambers and the space between the mounting base and the inner wall of the installation channel are filled with a matching material having the same Poisson's coefficient as the original rock sample. The positioning assembly includes a base, a positioning plate, multiple support columns, and two sets of positioning lines; the original rock sample is placed on the base; the positioning plate is located above the original rock sample, is parallel to the base, and is connected to the base through multiple support columns; the upper and lower ends of the fixing seat are connected to the positioning plate and the base through two sets of positioning lines, respectively, so that the center point of the fixing seat coincides with the center point of the original rock sample.

[0007] Furthermore, each of the mounting slots has a lead wire slot on its wall, and the lead wire outlets of the lead wire slots on the three mounting slots are close to each other. The original rock sample is equipped with a wire outlet channel. The connecting cables of the sensors to be calibrated pass through their respective lead-in slots in sequence and are then led out through the wire outlet channel.

[0008] Furthermore, each apex of the fixing base is cut into a planar structure, and the wire outlets of the three lead slots are concentrated on the same planar structure.

[0009] Furthermore, the upper surface of the base is provided with a positioning groove that matches the surface size of the original rock sample.

[0010] Furthermore, the fixed base has two sets of wire grooves on its circumferential sidewalls. The two sets of positioning lines pass through the corresponding wire grooves and are connected to the positioning plate and the base, and the connection is provided with a fixing buckle.

[0011] Furthermore, the positioning line is made of steel wire.

[0012] The present invention also provides an installation method for a calibration device for an underground three-dimensional coupled stress testing sensor, which is characterized by including the following steps: Step 1: Install the three sensors to be calibrated into their respective mounting slots on the mounting base, with their sensitive surfaces facing outwards; Step 2: Place the mounting base with the sensor to be calibrated in the installation channel of the original rock sample, then place the original rock sample on the base, and adjust the position of the mounting base in the installation channel using two sets of positioning lines until the center point of the mounting base coincides with the center point of the original rock sample. Step 3: Pour the matching material into the installation channel, then vibrate to remove the gas from the matching material. After it has solidified, cut the positioning line and remove the original rock sample from the base. Finally, grind the upper and lower surfaces of the matching material to make it flush with the surface of the original rock sample, thus completing the installation of the underground three-dimensional coupled stress test sensor calibration device.

[0013] Further, in step 1, the installation method of the three sensors to be calibrated is as follows: First, apply epoxy resin to the three mounting slots of the mounting base, and press the three sensors to be calibrated into the corresponding mounting slots with the sensitive surfaces facing outwards; then, cover the sensitive surface of each sensor to be calibrated with a layer of plastic film, and use U-shaped clips to clamp and fix the sensors to be calibrated to the mounting base. After the epoxy resin has cured, remove the U-shaped clips and plastic film to complete the installation of the sensors to be calibrated.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a calibration device for a three-dimensional coupled stress testing sensor in underground environments. The device includes a pre-existing rock sample, a mounting base, and a positioning assembly. By mounting the sensor to be calibrated on the mounting base, and then installing the mounting base within an installation channel using the positioning assembly, the center point of the mounting base coincides with the center point of the pre-existing rock sample. Finally, matching material is filled into the installation channel, thus creating a three-dimensional test sample from three unidirectional sensors, enabling subsequent calibration. This device eliminates the need to modify the sensor's structure and uses a pre-existing rock sample consistent with the actual operating environment. By calibrating the sensor, the influence of complex stresses on the sensor can be fundamentally avoided, thereby improving the accuracy of stress testing.

[0015] 2. In the underground three-dimensional coupled stress test sensor calibration device provided by the present invention, the matching material can be flexibly selected according to the material of the original rock sample. This not only matches different usage environments, but also improves the fit between the calibration device and the sensor to be calibrated, thereby improving the calibration accuracy.

[0016] 3. The original rock sample in the underground three-dimensional coupled stress test sensor calibration device provided by the present invention is flexible and controllable. Different sizes of original rock samples can be designed for different underground environments to match different test environments.

[0017] 4. The underground three-dimensional coupled stress test sensor calibration device provided by the present invention is applicable to different types of sensors, and a mounting base that conforms to the sensor can be designed according to the type and size of the sensor.

[0018] 5. The present invention provides a calibration device for an underground three-dimensional coupled stress test sensor, which can accurately determine the position of the fixed base and the sensor to be calibrated by means of a positioning line, thereby reducing the influence of the external support structure on the calibration results.

[0019] 6. In the calibration device for an underground three-dimensional coupled stress test sensor provided by the present invention, each apex of the fixing base is a planar structure, thereby reducing the contact between the sharp position of the fixing base and the matching material, and avoiding the accuracy problem of gaps caused by different media.

[0020] 7. In the calibration device for an underground three-dimensional coupled stress test sensor provided by the present invention, lead wire grooves are respectively provided on the walls of the three mounting slots, and the outgoing ends of the three lead wire grooves are close to each other, thereby reducing the influence of the cables on the calibration results. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of an embodiment of the calibration device for an underground three-dimensional coupled stress testing sensor according to the present invention; Figure 2 This is a schematic diagram of the structure of the sensor to be calibrated installed on the fixed base in step 1 of an embodiment of the method of using a calibration device for an underground three-dimensional coupled stress test sensor of the present invention.

[0022] The attached figures are labeled as follows: 1-Original rock sample, 11-Installation channel, 12-Outlet channel; 2-Fixing base, 21-Installation groove, 22-Leading wire groove, 23-Threading groove, 24-Fixing buckle; 3-Sensor to be calibrated; 4-Base, 41-Positioning groove; 5-Positioning plate; 6-Support column; 7-Positioning line. Detailed Implementation

[0023] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] Combination Figure 1 and Figure 2 This embodiment provides a calibration device for a three-dimensional coupled stress test sensor in underground rock, including a rock sample 1, a fixing base 2, and a positioning component.

[0025] In this embodiment, the original rock sample 1 has a cubic structure and is provided with a vertical mounting channel 11 running through its top and bottom ends. The mounting channel 11 is a circular channel, and its central axis passes through the center of the original rock sample 1. The original rock sample 1 in this embodiment is determined according to the scale of the test environment. The size of the original rock sample 1 is obtained by numerical simulation calculation to avoid the influence of size effects, which is 200*200*200mm. The diameter of the mounting channel 11 is determined by the size of the sensor 3 to be calibrated, the size of the fixing base 2, and the strength of the original rock sample 1. It is necessary to ensure that the strength requirements are met. In this embodiment, the diameter of the mounting channel 11 is 80mm.

[0026] The mounting base 2 is a cube structure located within the mounting channel 11. Three mounting slots 21 are provided on the surface of the mounting base 2 for mounting the sensors 3 to be calibrated. The three mounting slots 21 are distributed on three adjacent faces of the mounting base 2, and these three faces share a common vertex. The mounting base 2 is positioned in the same orientation as the original rock sample 1, dividing the mounting channel 11 into two chambers. The two chambers and the space between the mounting base 2 and the inner wall of the mounting channel 11 are filled with a matching material having the same Poisson's coefficient as the original rock sample 1. According to the wave impedance formula, the product of the wave velocity and density of the matching material must be equal to the product of the wave velocity and density of the original rock sample 1.

[0027] The positioning assembly includes a base 4, a positioning plate 5, multiple support columns 6 and two sets of positioning lines 7; the upper surface of the base 4 is provided with a positioning groove 41 that matches the surface size of the original rock sample 1, the depth of the positioning groove 41 is 3mm, and the original rock sample 1 is placed in the positioning groove 41.

[0028] The positioning plate 5 is located above the original rock sample 1. It is parallel to the base 4 and connected to the base 4 through multiple support columns 6, and locked with nuts. The circumferential side wall of the fixing seat 2 is provided with two sets of wire grooves 23. The two sets of positioning lines 7 pass through the corresponding wire grooves 23 and are connected to the positioning plate 5 and the base 4, and the connection is provided with a fixing buckle 24. That is, the fixing seat 2 can be adjusted by pulling it up and down at both ends through the positioning lines 7.

[0029] The position of the fixing seat 2 can be adjusted using two sets of positioning lines 7, ultimately ensuring that the center point of the fixing seat 2 coincides with the center point of the original rock sample 1. The design of the threaded groove 23 is used to fix the positioning line 7, preventing it from sliding relative to the fixing seat 2 and affecting the accuracy of positioning. In this embodiment, the positioning line 7 is made of 0.25mm steel wire, which has high strength and low elasticity, making it easy to use for positioning, limiting the movement of the fixing seat 2 relative to the original rock sample 1, and ensuring accurate positioning.

[0030] Each mounting slot 21 has a lead wire slot 22 on its wall, and the outlet ends of the lead wire slots 22 on the three mounting slots 21 are close to each other to reduce the influence of the cable on the calibration results. The original rock sample 1 has a circular hole-type cable outlet channel 12 with a diameter of 5mm. The connecting cable of the sensor 3 to be calibrated passes through its respective lead wire slot 22 in sequence and then converges and is led out through the cable outlet channel 12.

[0031] Each apex of the mounting base 2 is cut into a planar structure to reduce the contact between the sharp points of the mounting base 2 and the matching material during calibration, which could lead to stress concentration and affect the calibration value. In this embodiment, the wire outlets of the three lead slots 22 are concentrated on the same planar structure.

[0032] This invention designs a sensor calibration device that fixes a unidirectional sensor in the calibration device, forming a calibration device with three orthogonal directions. This device does not add any support structure that would affect the test results or change the structure of the sensor itself while ensuring that the sensor is level. This improves the calibration accuracy of the sensor and thus ensures the accuracy of stress testing.

[0033] The present invention also provides an installation method for a calibration device for an underground three-dimensional coupled stress testing sensor, comprising the following steps: Step 1: Install the three sensors 3 to be calibrated into the corresponding mounting slots 21 on the mounting base 2, with their sensitive surfaces facing outwards. The specific installation method is as follows: First, select three sensors with corresponding ranges to be calibrated according to the requirements. Apply epoxy resin to the three mounting slots 21 of the mounting base 2 respectively, and press the three sensors 3 to be calibrated into the corresponding mounting slots 21 with the sensitive surfaces facing outward.

[0034] Next, a smooth plastic film is covered on the sensitive surface of each sensor 3 to be calibrated, and the three sensors 3 to be calibrated are clamped and fixed to the mounting base 2 by three U-shaped clips. After the epoxy resin has cured, the U-shaped clips and plastic film are removed, thus completing the installation of the sensors 3 to be calibrated.

[0035] Step 2: Place the mounting base 2 with the sensor to be calibrated 3 installed in the mounting channel 11 of the original rock sample 1, then place the original rock sample 1 on the base 4, and lead out the cables of the three sensors to be calibrated 3 through the cable outlet channel 12, leaving 10-20cm inside for easy positioning of the mounting base 2 later.

[0036] The two sets of positioning lines 7 are passed through the corresponding threading grooves 23 and the positioning holes reserved on the positioning plate 5 and the base 4 respectively. The position of the fixing seat 2 in the installation channel 11 is adjusted by the length of the positioning lines 7 until the center point of the fixing seat 2 coincides with the center point of the original rock sample 1.

[0037] After slowly pulling out the reserved sensor cable, place the circular bubble ruler on the surface of the fixed base 2, adjust the positioning line 7 to ensure that the fixed base 2 is horizontal, and then use the fixing buckle 24 to lock the positioning line 7 to determine the position of the fixed base 2.

[0038] Step 3: Pour the matching material into the installation channel 11, then vibrate to remove the gas from the matching material. After it has solidified, cut off the excess positioning line 7 and remove the original rock sample 1 from the base 4. Finally, grind the upper and lower surfaces of the matching material to make it flush with the surface of the original rock sample 1, thereby completing the installation of the underground three-dimensional coupled stress test sensor calibration device for subsequent calibration.

[0039] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A device for calibrating a three-way coupled stress test sensor in an underground environment, comprising: a rock sample (1), a fixed seat (2), and a positioning assembly. The rock sample (1) is in a cubic structure and is provided with an installation channel (11) vertically penetrating through the upper and lower ends thereof; the installation channel (11) is a circular channel, and the central axis thereof passes through the center of the rock sample (1). The fixed seat (2) is in a cubic structure and is located in the installation channel (11); the surface of the fixed seat (2) is provided with three installation grooves (21) for installing a sensor (3) to be calibrated; the three installation grooves (21) are distributed on three adjacent surfaces of the fixed seat (2), and the three surfaces share a vertex; the fixed seat (2) is consistent with the placement orientation of the rock sample (1) and divides the installation channel (11) into two chambers, and the chambers and the circumferential side wall of the fixed seat (2) are filled with a matching material having the same Poisson's ratio as the rock sample (1). The positioning assembly comprises a base (4), a positioning plate (5), a plurality of support columns (6), and two groups of positioning lines (7); the rock sample (1) is placed on the base (4); the positioning plate (5) is located above the rock sample (1) and is parallel to the base (4) and connected to the base (4) through the plurality of support columns (6); the upper end and the lower end of the fixed seat (2) are connected to the positioning plate (5) and the base (4) through the two groups of positioning lines (7), so that the center point of the fixed seat (2) coincides with the center point of the rock sample (1). 2.The device for calibrating a three-way coupled stress test sensor in an underground environment according to claim 1, wherein: each installation groove (21) is provided with a lead slot (22) on the groove wall, and the lead-out ends of the lead slots (22) of the three installation grooves (21) are close to each other; the rock sample (1) is provided with a lead-out channel (12), and the connection cables of the sensors (3) to be calibrated are sequentially collected through the respective lead slots (22) and led out through the lead-out channel (12). 3.The device for calibrating a three-way coupled stress test sensor in an underground environment according to claim 2, wherein: each vertex of the fixed seat (2) is cut into a planar structure, and the lead-out ends of the three lead slots (22) are concentrated on the same planar structure. 4.The device for calibrating a three-way coupled stress test sensor in an underground environment according to claim 1 or 2 or 3, wherein: the upper surface of the base (4) is provided with a positioning groove (41) matching the surface size of the rock sample (1). 5.The device for calibrating a three-way coupled stress test sensor in an underground environment according to claim 4, wherein: the circumferential side wall of the fixed seat (2) is provided with two groups of threading grooves (23), and the two groups of positioning lines (7) are connected to the positioning plate (5) and the base (4) through the corresponding threading grooves (23), and the connection portions are provided with fixing buckles (24). 6.The device for calibrating a three-way coupled stress test sensor in an underground environment according to claim 5, wherein: the positioning lines (7) are steel wires. comprising the following steps: ​ ​ ​ ​ ​ ​ 7. The installation method of the calibration device of the underground three-way coupling stress test sensor according to any one of claims 1 to 6, characterized in that, ​ Step 1: Install three sensors (3) to be calibrated in the corresponding installation slots (21) of the fixed seat (2) respectively, with their sensitive surfaces facing outward; Step 2: Place the fixed seat (2) with the sensors (3) to be calibrated in the installation channel (11) of the original rock sample (1), and then place the original rock sample (1) on the base (4). Adjust the position of the fixed seat (2) in the installation channel (11) through the two sets of positioning lines (7) until the center point of the fixed seat (2) coincides with the center point of the original rock sample (1); Step 3: Pour matching material into the installation channel (11), and then remove the gas in the matching material by vibrating. After the matching material solidifies, cut off the positioning lines (7), remove the original rock sample (1) from the base (4), and finally polish the upper and lower surfaces of the matching material to make them flush with the surface of the original rock sample (1), thereby completing the installation of the calibration device for the underground three-way coupled stress test sensor.

8. The installation method of the calibration device for the underground three-way coupled stress test sensor according to claim 7, characterized in that: In step 1, the installation method of the three sensors (3) to be calibrated is as follows: First, apply epoxy resin in the three installation slots (21) of the fixed seat (2), and press the sensitive surfaces of the three sensors (3) to be calibrated into the corresponding installation slots (21) with the sensitive surfaces facing outward. Then, cover a layer of plastic film on the sensitive surface of each sensor (3) to be calibrated, and clamp the sensor (3) to be calibrated and the fixed seat (2) with a U-shaped clamp. After the epoxy resin solidifies, remove the U-shaped clamp and the plastic film, and complete the installation of the sensors (3) to be calibrated.

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