Drilling stress meter based on magnetic grid sensor principle and method for monitoring surrounding rock stress

Abstract

The invention provides a borehole stress meter based on a magnetic grid sensor principle and a surrounding rock stress monitoring method. The borehole stress meter comprises a cylindrical shell, an upper steel sheet, a lower steel sheet, a long-strip-shaped wedge-shaped block, an arc-shaped pressure-bearing block and a magnetic grid sensor. The outer wall of the cylindrical shell and the inner wall of the arc-shaped pressure-bearing block are each provided with a longitudinal groove used for containing the long-strip-shaped wedge-shaped block. The long-strip-shaped wedge-shaped block is contained in a space formed by the two longitudinal grooves, the wedge-shaped block slides to enable the arc-shaped pressure-bearing block and the cylindrical shell to be tightly attached to the inner wall of a surrounding rock drill hole, and surrounding rock stress is sensed. The upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell are rigidly connected with an upper steel sheet and a lower steel sheet respectively; the upper steel sheet and the lower steel sheet are arranged in parallel and are not in the same axial plane; and magnetic grid sensors are respectively adhered to the surfaces of the upper steel sheet and the lower steel sheet. The borehole stress meter is arranged in a surrounding rock borehole, and the deformation of the cylindrical shell is measured through the magnetic grid sensor to calculate the surrounding rock stress.

Description

Technical Field

[0001] The present invention relates to a borehole stress meter for measuring surrounding rock stress, and in particular to a borehole stress meter based on the magnetic grating sensor principle and a method for monitoring surrounding rock stress using the borehole stress meter. The present invention belongs to the technical field of underground engineering safety monitoring. Background Art

[0002] Large-scale water conservancy and hydropower projects are characterized by their large construction scale. During the excavation and construction of their underground powerhouses, chambers and tunnels, strong surrounding rock stress transfer can easily induce rock bursts, large deformation of surrounding rock, spalling, collapse and other engineering disasters, which seriously restrict the construction progress and threaten the safety of personnel and equipment. Therefore, strengthening the monitoring of the evolution characteristics of surrounding rock stress during the construction of underground chambers and tunnels is a prerequisite for ensuring the safe construction and efficient advancement of large-scale water conservancy and hydropower projects.

[0003] At present, the monitoring of surrounding rock stress in chambers and tunnels of water conservancy and hydropower projects is lacking in monitoring means and low monitoring accuracy, which makes it impossible to accurately judge the changes in high ground stress, the trend of rock deformation, the unloading effect of surrounding rock, and the changes in seepage pressure. The reason is that, on the one hand, conventional monitoring equipment such as vibrating wire borehole stress gauge converts the surrounding rock borehole stress into the surrounding rock borehole deformation, and then converts the surrounding rock borehole deformation into the deformation of the vibrating wire borehole stress gauge shell, and then further converts the shell deformation into the vibration wire frequency change, and reads the vibration wire frequency change and converts it into stress to achieve the monitoring of surrounding rock stress. Due to the multiple conversions of physical quantities, there is a certain impact on the stress measurement accuracy, resulting in low monitoring accuracy, which makes it difficult to meet the high-precision surrounding rock stress monitoring needs; on the other hand, the elastic modulus of the surrounding rock of the chamber is generally high. When the surrounding rock stress changes significantly, the deformation of the borehole in the surrounding rock is still small, and the deformation of the vibrating wire borehole stress gauge shell is even smaller, resulting in inaccurate monitoring results and low monitoring accuracy. Summary of the invention

[0004] In order to solve the problem of monitoring surrounding rock stress in underground engineering in water conservancy and hydropower engineering, the purpose of the present invention is to provide a borehole stress meter based on the principle of magnetic grating sensor. The borehole stress meter can realize efficient and accurate monitoring of surrounding rock stress and provide reliable reference data for real-time safety warning of disaster behavior.

[0005] Another object of the present invention is to provide a method for monitoring surrounding rock stress using the borehole stress gauge.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a drilling stress gauge based on the principle of magnetic grating sensor, which includes a cylindrical shell, an upper steel sheet, a lower steel sheet, a long wedge block, an arc-shaped pressure block and a magnetic grating sensor;

[0007] The cylindrical shell is built into the surrounding rock borehole, and a longitudinal pit groove for accommodating the long wedge block is opened on its outer wall; the arc-shaped side of the arc-shaped pressure block is in close contact with the inner wall of the surrounding rock borehole, and a longitudinal groove for accommodating the long wedge block is opened on its inner wall; the cylindrical shell, the long wedge block and the arc-shaped pressure block are arranged in parallel along the axis of the surrounding rock borehole, and the long wedge block is accommodated in the space formed by the longitudinal pit groove and the longitudinal groove, and can slide in the space formed by the longitudinal pit groove and the longitudinal groove, so that the arc-shaped pressure block and the cylindrical shell are both in close contact with the inner wall of the surrounding rock borehole;

[0008] The upper steel sheet and the lower steel sheet are rigidly connected to the top surface and the bottom surface of the inner cavity of the cylindrical shell respectively; the upper steel sheet and the lower steel sheet are arranged in parallel, and the horizontal projection distance between the two is 0.1mm-0.3mm; the length of the upper steel sheet and the lower steel sheet is 0.5-0.8 times the inner cavity diameter of the cylindrical shell;

[0009] The upper steel sheet and the lower steel sheet are arranged opposite to each other in the inner cavity of the cylindrical shell;

[0010] The magnetic grating sensors are respectively adhered to the surfaces of the upper steel sheet and the lower steel sheet.

[0011] Preferably, the upper steel sheet is fixed on the inner wall of the cylindrical shell cavity close to the elongated wedge block, and the lower steel sheet is fixed on the inner wall of the other side of the cylindrical shell cavity opposite and away from the elongated wedge block.

[0012] Preferably, the cylindrical shell, the elongated wedge-shaped block and the arc-shaped pressure-bearing block are all made of stainless steel.

[0013] Preferably, the cylindrical shell has an optimal outer radius of 20 mm and an inner cavity radius of 10 mm.

[0014] Preferably, the displacement range of the magnetic grating sensor needs to meet 1-1000 microns, and its accuracy is 0.1-1 microns.

[0015] A method for monitoring surrounding rock stress using the borehole stress gauge based on the magnetic grating sensor principle, comprising:

[0016] S1. First, make a stainless steel cylindrical shell with a length of 40mm-100mm, a wall thickness of 10mm-35mm, and an inner cavity radius of 10mm;

[0017] An upper steel sheet and a lower steel sheet are rigidly fixed on the top surface and the bottom surface of the inner cavity of the cylindrical shell respectively;

[0018] The upper steel sheet and the lower steel sheet are arranged in parallel, the two are not on the same longitudinal plane, and the horizontal projection distance between the two is 0.1mm-0.3mm; the length of the upper steel sheet and the lower steel sheet is 0.5-0.8 times the diameter of the inner cavity of the cylindrical shell; one end of the upper steel sheet is fixed on the inner wall of one side of the inner cavity of the cylindrical shell, and one end of the lower steel sheet is fixed on the inner wall of the other side of the inner cavity of the cylindrical shell;

[0019] A magnetic grating sensor is pasted on the upper and lower steel sheets respectively;

[0020] S2, make a stainless steel long wedge block with a length of 50mm-125mm, a width of 10mm-15mm, and a top angle of 5°-15°;

[0021] S3, making a stainless steel arc-shaped pressure block with a length of 40mm-80mm that can fit the inner wall of the surrounding rock borehole;

[0022] S4. A longitudinal groove for accommodating the long strip wedge-shaped block is opened on the outer wall of the cylindrical shell, and the depth of the longitudinal groove is 5-10 mm; a longitudinal groove for accommodating the long strip wedge-shaped block is also opened on the inner wall of the arc-shaped pressure-bearing block;

[0023] S5, placing the arc-shaped pressure-bearing block and the cylindrical shell in parallel, accommodating the long strip wedge-shaped block in the space formed by the longitudinal groove of the arc-shaped pressure-bearing block and the longitudinal groove of the cylindrical shell, sliding the long strip wedge-shaped block so that the three are closely fitted into a whole to form a drilling stress gauge;

[0024] S6, simulate the surrounding rock stress, apply 5, 6, 7, 8, 9 and 10 MPa to the borehole stress gauge from the top of the arc-shaped pressure block downward, measure the displacement of the upper and lower steel sheets of the cylindrical shell, and draw a curve diagram of the relationship between the simulated surrounding rock stress and the displacement of the upper and lower steel sheets in the cylindrical shell of the borehole stress gauge; fit the curve with a linear equation, and the correlation coefficient R2 is equal to 0.99, and obtain a curve with good linearity between the simulated load and the change in the relative position of the upper and lower steel sheets of the cylindrical shell;

[0025] S7. The borehole stress meter is buried in the actual engineering surrounding rock borehole. The arc-shaped pressure block and the cylindrical shell with built-in magnetic grating sensor are made to fit closely to the inner wall of the surrounding rock borehole by sliding the long wedge block. The relative displacement of the upper and lower steel sheets of the cylindrical shell is measured. The surrounding rock stress is directly calculated based on the relationship curve between the simulated load and the relative position change of the upper and lower steel sheets of the cylindrical shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the side view of the surrounding rock borehole structure in which the borehole stress meter of the present invention is built-in;

[0027] Figure 2 is along Figure 1 AA-direction cutaway side view of the structure;

[0028] Figure 3 It is to simulate the stress state of the borehole stress meter of the present invention in the surrounding rock borehole;

[0029] Figure 4 It is a cloud diagram of the relative position change of the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell of the borehole stress gauge of the present invention under different simulated stresses;

[0030] Figure 5 The present invention is a simulation calculation of the relationship curve between the relative position change of the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell and the load when the drilling stress gauge is made of stainless steel material under different simulated loads;

[0031] Figure 6 The present invention is a simulation calculation of the relationship curve between the relative position change of the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell and the load when the drilling stress gauge of the present invention is made of aluminum alloy material under different simulated loads;

[0032] Figure 7 The present invention simulates and calculates the relationship curve between the relative position change of the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell and the load when the outer radius of the cylindrical shell is 25 mm for the borehole stress gauge made of stainless steel material of the present invention. DETAILED DESCRIPTION

[0033] The structure and features of the present invention are described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that various modifications can be made to the embodiments disclosed herein, and therefore, the embodiments disclosed in the specification should not be regarded as limiting the present invention, but are merely examples of embodiments, the purpose of which is to make the features of the present invention obvious.

[0034] Magnetic grating ranging technology has the characteristics of accurate deformation measurement, high resolution, high precision, strong long-term working stability and little interference. Considering the long-term stress monitoring problem during the construction process and service life of underground chambers and tunnels, the present invention uses magnetic grating sensors to form a borehole stress meter to monitor the stress unloading and transfer process inside the surrounding rock, reflect the overall stress state of the surrounding rock, and provide accurate and reliable reference data for the risk assessment of surrounding rock instability.

[0035] like Figure 1 , Figure 2 As shown, the borehole stress gauge based on the magnetic grating sensor principle disclosed in the present invention includes a cylindrical shell 1, an upper steel sheet 2, a lower steel sheet 3, a long wedge block 4, an arc-shaped pressure block 5 and a magnetic grating sensor 6.

[0036] The cylindrical shell 1 is built into the surrounding rock borehole 7, and a longitudinal pit groove for accommodating the elongated wedge block 4 is opened on its outer wall; the arc-shaped edge of the arc-shaped pressure-bearing block 5 is tightly attached to the inner wall of the surrounding rock borehole 7, and a longitudinal groove for accommodating the elongated wedge block 4 is also opened on the inner wall of the pressure-bearing block 5; the cylindrical shell 1, the elongated wedge block 4 and the arc-shaped pressure-bearing block 5 are arranged parallel to the axis of the surrounding rock borehole, and the elongated wedge block 4 is accommodated in the space formed by the longitudinal pit groove and the longitudinal groove, and can slide in the space formed by the longitudinal pit groove and the longitudinal groove, so that the arc-shaped pressure-bearing block 5 and the cylindrical shell 1 are tightly attached to the inner wall of the surrounding rock borehole 7, and feel the deformation of the surrounding rock 8, the internal stress unloading and transfer process.

[0037] An upper steel sheet 2 and a lower steel sheet 3 are rigidly connected to the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell 1, respectively. The upper steel sheet 2 and the lower steel sheet 3 are arranged in parallel, and the two are not on the same longitudinal plane. The horizontal projection distance between the two is 0.1mm-0.3mm. The length of the upper steel sheet 2 and the lower steel sheet 3 is 0.5-0.8 times the diameter of the inner cavity of the cylindrical shell, and there is no limit to their width, as long as the surface can be pasted with the magnetic grating sensor 6. As shown in the figure, one end of the upper steel sheet 2 is fixed on the inner wall of one side of the inner cavity of the cylindrical shell, and one end of the lower steel sheet 3 is fixed on the inner wall of the other side of the inner cavity of the cylindrical shell. In order to better sense the deformation, internal stress unloading and transfer process of the surrounding rock, in a preferred embodiment of the present invention, the upper steel sheet 2 is fixed on the inner wall of the inner cavity of the cylindrical shell close to the long wedge block 4, and the lower steel sheet 3 is fixed on the inner wall of the other side of the inner cavity of the cylindrical shell opposite and away from the long wedge block 4.

[0038] Magnetic grating sensors 6 are attached to the surfaces of the upper steel sheet 2 and the lower steel sheet 3 to detect the displacement between the upper and lower steel sheets. The data line of the magnetic grating sensor passes through the through hole 11 opened in the side wall of the cylindrical shell. When the surrounding rock 8 is deformed, the internal stress is unloaded and transferred, the changes in the surrounding rock are transmitted to the upper steel sheet 2 and the lower steel sheet 3 through the pressure block 5, the wedge block 4, and the cylindrical shell 1 that are tightly fitted with the inner wall of the surrounding rock borehole; the upper and lower steel sheets produce relative displacement from the initial position, and the relative displacement between the two is detected by the magnetic grating sensor 6, thereby monitoring the changes in the surrounding rock stress.

[0039] In a preferred embodiment of the present invention, the arc-shaped pressure block, the elongated wedge-shaped block, and the cylindrical shell are all made of rust-proof metal materials and have good rust-proof capabilities, which can ensure that the present invention can work stably for a long time in underground powerhouses and tunnel surrounding rocks of water conservancy and hydropower projects.

[0040] The displacement range of the magnetic grating sensor 6 of the present invention needs to meet 1-1000 microns, and its accuracy is 0.1-1 microns.

[0041] The working principle of the present invention for monitoring the change of surrounding rock stress is as follows: when the surrounding rock is deformed and the surrounding rock stress changes, the surrounding rock stress is transmitted to the wedge block through the pressure block, and the wedge block applies the stress to the shell, causing the deformation of the inner cavity of the shell. The change of the surrounding rock stress can be reflected by measuring the deformation of the inner cavity of the shell. In order to measure the deformation of the inner cavity of the shell, the present invention rigidly connects an upper steel sheet and a lower steel sheet to the upper top surface and the lower bottom surface of the inner cavity of the shell respectively, and magnetic grating sensors are attached to the upper and lower steel sheets. The deformation of the inner cavity of the shell can be directly and accurately monitored by the magnetic grating sensor, thereby monitoring the change of the surrounding rock stress.

[0042] The present invention establishes a relationship diagram between the deformation of the cylindrical shell and the stress it receives through comparative quantitative tests, that is, the stress change relationship corresponding to the deformation of the cylindrical shell. The specific method is as follows: first, a three-dimensional model of the borehole stress gauge of the present invention is established through computer simulation software, such as Figure 3 As shown; then, the simulation analysis method is used to simulate different loads, measure the relative displacement of the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell of the borehole stress gauge of the present invention, and calculate and draw the relationship curve between the relative displacement between the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell of the present invention and the surrounding rock stress.

[0043] The simulation simulates the stress state of the cylindrical shell after the borehole stress gauge is loaded. That is, the simulated stress is applied from the top surface of the wedge block. The simulated stresses are 5, 6, 7, 8, 9 and 10 MPa respectively. The effective area of ​​the wedge block is 400 mm 2 , the simulated loads applied to the top surface of the wedge block are 2, 2.4, 2.8, 3.2, 3.6 and 4 kN respectively. The cylindrical shell and wedge block models are made of stainless steel. The outer radius of the cylindrical shell is 20 mm, and the inner radius of the cylindrical shell is 10 mm;

[0044] The cloud diagram of the relative position change of the top surface and the bottom surface of the inner cavity of the cylindrical shell of the drilling stress gauge model under different loads is simulated and calculated, such as Figure 4 As shown; Figure 5 It is a simulation calculation of the relative position change curve of the upper top surface and the lower bottom surface of the borehole stress gauge shell under different simulated loads. The horizontal axis is the simulated load, and the vertical axis is the relative position change of the upper top surface and the lower bottom surface. In order to obtain the relationship between the simulated load and the relative position change, the simulated load is converted by the relative position change, and the curve is fitted with a first-order equation. The correlation coefficient R2 is equal to 0.99, and the relationship curve between the simulated load and the relative position change with good curve linearity is obtained. In actual engineering, the surrounding rock stress can be directly calculated based on the measured relative position change of the upper top surface and the lower bottom surface of the cylindrical shell cavity, and the relationship curve between the fitted simulated load and the relative position change.

[0045] Since the present invention is mainly aimed at the surrounding rock of underground projects, the mechanical parameters of underground project rock masses vary greatly. Therefore, the materials constituting the cylindrical shell, elongated wedge-shaped blocks, and arc-shaped pressure-bearing blocks of the present invention need to be selected in consideration of the rock mass and the underlying conditions. Figure 5 It is a curve of the relationship between the relative position change of the upper top surface and the lower bottom surface of the inner cavity of the shell and the load when the pressure block, the wedge block and the shell of the borehole stress gauge of the present invention are made of stainless steel by simulation calculation; Figure 6 The present invention is a simulation calculation of the relationship curve between the relative position change of the upper top surface and the lower bottom surface of the inner cavity of the shell and the load when the pressure block, the wedge block and the shell of the borehole stress gauge are made of aluminum alloy; Figure 5 and Figure 6 It can be seen that due to the lower elastic modulus of aluminum alloy relative to stainless steel, the deformation of the aluminum alloy shell is larger under the same load. When the simulated loads are 2, 2.4, 2.8, and 3.2 kN, respectively, the curve linearity is better. However, when the simulated load is 4 kN, the curve linearity deteriorates. For the shell made of stainless steel, when the simulated loads are 2, 2.4, 2.8, 3.2, and 4 kN, respectively, the curve linearity is better. Therefore, the pressure block, wedge block, and shell of the drilling stress gauge of the present invention are made of stainless steel.

[0046] In addition, the radius of the drill rod equipped with the drilling rig in underground engineering construction is generally a fixed value. In order to ensure that the present invention can adapt to drilling holes of different diameters, the outer radius of the cylindrical shell of the present invention needs to be adjusted according to the on-site conditions to meet the needs of different underground projects. Figure 7 The simulation calculation is the relationship curve between the relative position change of the top surface and the bottom surface of the inner cavity and the load when the outer radius of the stainless steel cylindrical shell of the present invention is 25mm. Figure 5 and Figure 7 By comparison, it can be seen that compared with the outer radius of 25mm, when the outer radius of the shell is 20mm, the linearity of the curve of the relative position change of the upper top surface and the lower bottom surface of the inner cavity of the cylindrical shell and the load is better. Therefore, in a preferred embodiment of the present invention, the cylindrical shell constituting the present invention is made of stainless steel material, the outer radius of the cylindrical shell is 20mm, and the inner cavity radius is 10mm.

[0047] The method of the present invention for monitoring surrounding rock stress using a borehole stress meter based on the magnetic grating sensor principle is as follows:

[0048] S1. First, make a stainless steel cylindrical shell with a length of 40mm-100mm, a wall thickness of 10mm-35mm, and an inner cavity radius of 10mm;

[0049] An upper steel sheet and a lower steel sheet are rigidly fixed on the top surface and the bottom surface of the inner cavity of the cylindrical shell respectively;

[0050] The upper steel sheet and the lower steel sheet are arranged in parallel, the two are not on the same longitudinal plane, and the horizontal projection distance between the two is 0.1mm-0.3mm; the length of the upper steel sheet and the lower steel sheet is 0.5-0.8 times the diameter of the inner cavity of the cylindrical shell; the upper steel sheet is fixed on the inner wall of one side of the inner cavity of the cylindrical shell, and the lower steel sheet is fixed on the inner wall of the other side of the inner cavity of the cylindrical shell;

[0051] A magnetic grating sensor is pasted on the upper and lower steel sheets respectively;

[0052] S2, make a stainless steel long wedge block with a length of 50mm-125mm, a width of 10mm-15mm, and a top angle of 5°-15°;

[0053] S3, making a stainless steel arc-shaped pressure block with a length of 40mm-80mm that can fit the inner wall of the surrounding rock borehole;

[0054] S4. A longitudinal groove for accommodating the long strip wedge-shaped block is opened on the outer wall of the cylindrical shell, and the depth of the longitudinal groove is 5-10 mm; a longitudinal groove for accommodating the long strip wedge-shaped block is also opened on the inner wall of the arc-shaped pressure-bearing block;

[0055] S5, placing the arc-shaped pressure-bearing block and the cylindrical shell in parallel, accommodating the long strip wedge-shaped block in the space formed by the longitudinal groove of the arc-shaped pressure-bearing block and the longitudinal groove of the cylindrical shell, sliding the long strip wedge-shaped block so that the three are closely fitted into a whole to form a drilling stress gauge;

[0056] S6, simulate the surrounding rock stress, apply 5, 6, 7, 8, 9 and 10 MPa to the borehole stress gauge from the top of the arc-shaped pressure block downward, measure the displacement of the upper and lower steel sheets of the cylindrical shell, and draw a curve diagram of the relationship between the simulated surrounding rock stress and the displacement of the upper and lower steel sheets in the cylindrical shell of the borehole stress gauge; fit the curve with a linear equation, and the correlation coefficient R2 is equal to 0.99, and obtain a curve with good linearity between the simulated load and the change in the relative position of the upper and lower steel sheets of the cylindrical shell;

[0057] S7. The borehole stress meter is buried in the actual engineering surrounding rock borehole. The arc-shaped pressure block and the cylindrical shell with built-in magnetic grating sensor are made to fit closely to the inner wall of the surrounding rock borehole by sliding the long wedge block. The relative displacement of the upper and lower steel sheets of the cylindrical shell is measured. The surrounding rock stress is directly calculated based on the relationship curve between the simulated load and the relative position change of the upper and lower steel sheets of the cylindrical shell.

[0058] The method of monitoring surrounding rock stress by using a borehole stress gauge based on the magnetic grating sensor principle has the following advantages over traditional measuring devices and monitoring methods:

[0059] 1. High monitoring accuracy.

[0060] The present invention directly measures the deformation of the inner cavity of the cylindrical shell constituting the borehole stress gauge of the present invention through a magnetic grating sensor, and intuitively obtains the change of the inner cavity when the shell is subjected to force, thereby reducing physical quantity conversion calculations, reducing stress measurement errors, and having high measurement accuracy, thereby significantly improving the monitoring accuracy of surrounding rock stress.

[0061] 2. The present invention adopts magnetic grating sensor for measurement, which has the advantages of long service life and high measurement accuracy. It has strong sensing ability for small changes in the rock wall of the surrounding rock borehole, and the measurement accuracy of the deformation of the borehole stress gauge shell can reach micron level, which can better meet the requirements of high-precision measurement of water conservancy and hydropower projects.

[0062] 3. The present invention has been verified through simulation. By using different shell, wedge block and pressure block materials and adjusting the shell radius, a highly linear shell deformation and load correlation curve can be obtained. On the premise of directly obtaining the accurate relative displacement of the top and bottom surfaces of the shell by using a magnetic grating sensor, the stress condition of the surrounding rock can be accurately monitored through a highly linear calibration curve.

[0063] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A drilling stress gauge based on the principle of magnetic grating sensor, characterized in that: It includes a cylindrical shell, an upper steel sheet, a lower steel sheet, a long wedge-shaped block, an arc-shaped pressure-bearing block and a magnetic grating sensor; The cylindrical shell is built into the surrounding rock borehole, and a longitudinal pit groove for accommodating the long wedge block is opened on its outer wall; the arc-shaped side of the arc-shaped pressure block is in close contact with the inner wall of the surrounding rock borehole, and a longitudinal groove for accommodating the long wedge block is opened on its inner wall; the cylindrical shell, the long wedge block and the arc-shaped pressure block are arranged in parallel along the axis of the surrounding rock borehole, and the long wedge block is accommodated in the space formed by the longitudinal pit groove and the longitudinal groove, and can slide in the space formed by the longitudinal pit groove and the longitudinal groove, so that the arc-shaped pressure block and the cylindrical shell are both in close contact with the inner wall of the surrounding rock borehole; The upper steel sheet and the lower steel sheet are rigidly connected to the top surface and the bottom surface of the inner cavity of the cylindrical shell respectively; the upper steel sheet and the lower steel sheet are arranged in parallel, and the horizontal projection distance between the two is 0.1mm-0.3mm; the length of the upper steel sheet and the lower steel sheet is 0.5-0.8 times the inner cavity diameter of the cylindrical shell; The upper steel sheet and the lower steel sheet are arranged opposite to each other in the inner cavity of the cylindrical shell; The magnetic grating sensors are respectively adhered to the surfaces of the upper steel sheet and the lower steel sheet.

2. The drilling stress gauge based on the magnetic grating sensor principle according to claim 1 is characterized in that: The upper steel sheet is fixed on the inner wall of the cylindrical shell cavity close to the long wedge-shaped block, and the lower steel sheet is fixed on the inner wall of the other side of the cylindrical shell cavity opposite and away from the long wedge-shaped block.

3. The drilling stress gauge based on the magnetic grating sensor principle according to claim 2 is characterized in that: The cylindrical shell, the long strip wedge-shaped block and the arc-shaped pressure-bearing block are all made of stainless steel.

4. The drilling stress gauge based on the magnetic grating sensor principle according to claim 3 is characterized in that: The cylindrical shell has an optimal outer radius of 20 mm and an inner cavity radius of 10 mm.

5. The drilling stress gauge based on the magnetic grating sensor principle according to any one of claims 1 to 4, characterized in that: The displacement range of the magnetic grating sensor must meet 1-1000 microns, and its accuracy is 0.1-1 microns.

6. A method for monitoring surrounding rock stress using a borehole stress gauge based on the magnetic grating sensor principle as claimed in any one of claims 1 to 5, characterized in that: It includes: S1. First, make a stainless steel cylindrical shell with a length of 40mm-100mm, a wall thickness of 10mm-35mm, and an inner cavity radius of 10mm; An upper steel sheet and a lower steel sheet are rigidly fixed on the top surface and the bottom surface of the inner cavity of the cylindrical shell respectively; The upper steel sheet and the lower steel sheet are arranged in parallel, the two are not on the same longitudinal plane, and the horizontal projection distance between the two is 0.1mm-0.3mm; the length of the upper steel sheet and the lower steel sheet is 0.5-0.8 times the diameter of the inner cavity of the cylindrical shell; one end of the upper steel sheet is fixed on the inner wall of one side of the inner cavity of the cylindrical shell, and one end of the lower steel sheet is fixed on the inner wall of the other side of the inner cavity of the cylindrical shell; A magnetic grating sensor is pasted on the upper and lower steel sheets respectively; S2, make a stainless steel long wedge block with a length of 50mm-125mm, a width of 10mm-15mm, and a top angle of 5°-15°; S3, making a stainless steel arc-shaped pressure block with a length of 40mm-80mm that can fit the inner wall of the surrounding rock borehole; S4. A longitudinal groove for accommodating the long strip wedge-shaped block is opened on the outer wall of the cylindrical shell, and the depth of the longitudinal groove is 5-10 mm; a longitudinal groove for accommodating the long strip wedge-shaped block is also opened on the inner wall of the arc-shaped pressure-bearing block; S5, placing the arc-shaped pressure-bearing block and the cylindrical shell in parallel, accommodating the long strip wedge-shaped block in the space formed by the longitudinal groove of the arc-shaped pressure-bearing block and the longitudinal groove of the cylindrical shell, sliding the long strip wedge-shaped block so that the three are closely fitted into a whole to form a drilling stress gauge; S6, simulate the surrounding rock stress, apply 5, 6, 7, 8, 9 and 10 MPa to the borehole stress gauge from the top of the arc-shaped pressure block downward, measure the displacement of the upper and lower steel sheets of the cylindrical shell, and draw a curve diagram of the relationship between the simulated surrounding rock stress and the displacement of the upper and lower steel sheets in the cylindrical shell of the borehole stress gauge; fit the curve with a linear equation, and the correlation coefficient R2 is equal to 0.99, and obtain a curve with good linearity between the simulated load and the change in the relative position of the upper and lower steel sheets of the cylindrical shell; S7. The borehole stress meter is buried in the actual engineering surrounding rock borehole. The arc-shaped pressure block and the cylindrical shell with built-in magnetic grating sensor are made to fit closely to the inner wall of the surrounding rock borehole by sliding the long wedge block. The relative displacement of the upper and lower steel sheets of the cylindrical shell is measured. The surrounding rock stress is directly calculated based on the relationship curve between the simulated load and the relative position change of the upper and lower steel sheets of the cylindrical shell.

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