Device and method for measuring residual stress of rock mass at non-uniform temperature

Abstract

The invention discloses a device and a method for measuring residual stress of a rock mass at a non-uniform temperature. The device comprises a sample cell, a heating temperature control system and an X-ray diffractometer system, the sample pool comprises a sample pool upper base and a sample pool lower base, and a rock mass sample to be detected is placed in the sample pool upper base; the heating temperature control system comprises a thermocouple, a heating element and a PID (Proportion Integration Differentiation) temperature controller; the non-uniform temperature evolution process in the X-ray diffraction testing process is changed through a heating temperature control system, the non-uniform temperature environment where the rock mass is located under the real working condition is simulated, in-situ testing is carried out on the rock mass under the non-uniform temperature condition through an X-ray diffractometer, diffraction peak data of the rock mass at each same inclination angle psi are tested and collected through a same inclination method, and the rock mass is subjected to in-situ testing through the X-ray diffractometer. Further determining the residual stress evolution process of the rock mass at different temperatures; meanwhile, stress relief annealing treatment can be carried out on the rock mass sample through the heating temperature control system, and the change condition of residual stress after stress relief annealing treatment under different non-uniform temperature fields is researched.

Description

Technical Field

[0001] The present invention relates to the technical field of residual stress characterization of rock mass materials, and particularly to a device and method for measuring the residual stress of rock mass under non-uniform temperature. Background Art

[0002] Residual stress refers to the internal stress that maintains self-equilibrium in a material without external loads or changing temperature environments. For rock mass materials, residual stress may cause crack propagation in the rock mass materials, reduce the crack resistance of the rock mass materials, and thus affect the stability of geological engineering. Therefore, measuring the residual stress of rock mass materials is of great significance for geological engineering safety.

[0003] Regarding the method for characterizing the residual stress of rock mass materials, among which the X-ray diffraction method (XRD) has the advantages of non-destructive, fast, accurate, etc., and is therefore widely used for measuring the residual stress of materials. Among them, the same inclination method (sin 2 ψ method) is applicable to samples with large and flat measured surfaces and can be used for characterizing the residual stress of rock mass materials. The same inclination method performs XRD characterization at different same inclination angles ψ (the angle between the sample surface and the X-ray beam), records the diffraction angle θ (the angle between the X-ray and the diffracting crystal plane) at each same inclination angle ψ, and then, according to the Bragg equation, elastic mechanics theory, combined with the Poisson's ratio and elastic modulus of the rock mass, the magnitude and distribution law of the residual stress of the material can be analyzed. Currently, the commonly used same inclination method usually performs characterization tests at room temperature, while in actual working conditions, rock mass materials are usually under non-uniform temperature field conditions; on the other hand, studying the stress relief annealing of rock mass materials at different temperature conditions can effectively remove the residual stress in the rock mass materials and enhance the stability and reliability of the rock mass materials. Therefore, performing the residual stress characterization test of rock mass materials under non-uniform temperature field conditions has important scientific value and practical application significance in the fields of geological engineering and the like. Summary of the Invention

[0004] The main purpose of the present invention is to provide a device for measuring the residual stress of rock mass under non-uniform temperature. By using materials with different resistivities to form a heating element, the sample pool is in a non-uniform temperature field condition. The non-uniform temperature field distribution of the measured surface of the sample is monitored in real time through a thermocouple. The diffraction angle θ of the sample at each same inclination angle is measured by the in-situ XRD same inclination method, and the magnitude and distribution law of the residual stress are calculated through theoretical derivation. Based on this device, the present invention realizes the measurement of the residual stress of rock mass materials under non-uniform temperature field conditions, and reveals the relationship between the stress relief annealing of rock mass materials under different non-uniform temperature field conditions and the magnitude and distribution law of their residual stress through the stress relief annealing process and related theoretical methods.

[0005] The technical solution adopted by the present invention is:

[0006] An apparatus for measuring the residual stress of rock mass under non-uniform temperature, comprising a sample cell, a heating and temperature control system, and an X-ray diffractometer system; the sample cell includes an upper base of the sample cell and a lower base of the sample cell, and the rock mass sample to be detected is placed in the upper base of the sample cell; the heating and temperature control system includes a thermocouple, a heating element, and a PID temperature controller; a plurality of the thermocouples are arranged along a certain radial direction of the upper base of the sample cell for measuring the temperatures at different positions of the sample cell, and each thermocouple is electrically connected to the PID temperature controller to transmit the measured temperature signal to the PID temperature controller; a plurality of heating elements with different resistivities are arranged between the upper base of the sample cell and the lower base of the sample cell, and each heating element is electrically connected to the PID temperature controller; the PID temperature controller compares the actual temperature measured by the thermocouple with the preset temperature, and makes the actual temperature approach the preset temperature by controlling the energization time of the heating element, thereby realizing the control of non-uniform temperature; the X-ray diffractometer system includes an X-ray emitter, an X-ray detector, an X-ray diffraction sample stage, and an X-ray diffractometer control system; the sample cell is placed on the X-ray diffraction sample stage, the X-ray emitter and the X-ray detector are located above the sample cell and are respectively signal-connected to the X-ray diffractometer control system, the X-ray detector receives the ray intensity and diffraction angle θ of the diffracted ray after the X-ray emitter irradiates the sample, and transmits it to the X-ray diffractometer control system signal, and the X-ray diffractometer control system can change the same inclination angle ψ between the measured surface of the sample and the X-ray emitted by the X-ray emitter.

[0007] In the above solution, the sample cell further includes a transparent beryllium window, the transparent beryllium window is made of metallic beryllium, and the transparent beryllium window is placed on the upper end surface of the upper base of the sample cell, above the sample.

[0008] In the above solution, the sample cell further includes a sample cell housing, and the sample cell housing is fixedly connected to the upper base of the sample cell in a detachable manner; the upper base of the sample cell and the lower base of the sample cell are fixedly connected in a detachable manner.

[0009] In the above solution, a heating hole for inserting each heating element is opened in the horizontal direction at the connection between the upper base of the sample cell and the lower base of the sample cell, and each heating element is embedded in the heating hole in a straight line manner.

[0010] In the above solution, three thermocouples are arranged along a certain radial direction of the upper base of the sample cell by embedding, which are thermocouple I, thermocouple II, and thermocouple III respectively. Among them, thermocouple I and thermocouple III are respectively located at both ends, and thermocouple II is located at the midpoint between thermocouple I and thermocouple III.

[0011] In the above solution, two heating elements are arranged in parallel, namely the I heating element and the II heating element. Among them, the I heating element is arranged between the I thermocouple and the II thermocouple, and the II heating element is arranged between the II thermocouple and the III thermocouple.

[0012] In the above solution, let the position of the I thermocouple be x = 0, and the position of the III thermocouple be x = D. Then the position of the II thermocouple is x = D / 2. The temperature distribution in the sample cell with respect to the position x is calculated by formula (2), and formula (2) is as follows:

[0013]

[0014] In formula (2), T x is the temperature at position x in the sample cell, T 0 is the temperature at the I thermocouple, and T D is the temperature at the III thermocouple;

[0015] By presetting various temperature distribution conditions, the change of residual stress of the same rock sample under different non-uniform temperature fields is compared.

[0016] The present invention also proposes a method for measuring the residual stress of a rock mass under non-uniform temperature, which is carried out by using the above device and includes the following steps:

[0017] Step 1: Place the cut and polished rock mass sample on the upper base of the sample cell, place the transparent beryllium window above the sample, and place the sample cell on the X-ray diffraction sample stage;

[0018] Step 2: Turn on the heating and temperature control system for preheating, set the temperature to the preset temperature, and wait until the temperature difference between the I thermocouple and the III thermocouple is stable at 5 - 10 °C;

[0019] Step 3: After the temperature is stable, start the XRD test. Set the X-ray diffractometer system to the preset conditions, with the co-inclination angle ψ being 0°, the measurement range being 10 - 80°, conduct the first characterization, and obtain the highest diffraction intensity of the sample and its corresponding diffraction angle θ;

[0020] Step 4: Use the X-ray diffractometer control system to change the co-inclination angle ψ between the transparent beryllium window and the X-ray emitter, conduct XRD tests at multiple co-inclination angles, and record the highest diffraction intensity and its corresponding diffraction angle θ at each co-inclination angle;

[0021] Step 5: Calculate the stress value σ of the sample at each co-inclination angle ψ respectively, and use the stress value σ at each co-inclination angle as the vertical axis and the square of the sine value of the co-inclination angle sin 2 ψ as the horizontal axis to plot an image, perform linear fitting on the data, and obtain the residual stress existing at the measurement point of the sample.

[0022] Step 6. Adjust the heating and temperature control system, change the temperature in the sample cell, and repeat Steps 3 - 5 to record the change curve of the residual stress of the same sample under different non-uniform temperature field conditions.

[0023] In the above method, in Step 5, the lattice plane spacing d of the sample at each same inclination angle ψ is calculated by formula (3). ψ , and formula (3) is:

[0024] nλ = 2d ψ ·sinθ (3)

[0025] In formula (3), n is the diffraction order, usually taken as 1, representing the first-order diffraction; λ represents the wavelength of the X-ray source; d ψ is the lattice plane spacing of the sample to be measured at the same inclination angle ψ; θ is the diffraction angle;

[0026] Then, the stress value σ at each same inclination angle ψ is calculated by the elastic theory formula (4), and formula (4) is:

[0027]

[0028] In formula (4), σ is the stress value at each same inclination angle; E is the Young's modulus corresponding to the sample; ν is the Poisson's ratio corresponding to the sample; Δd is the change value of the lattice plane spacing of the sample at each same inclination angle, Δd = d ψ -d 0 ; d 0 is the lattice plane spacing of the sample when the inclination angle is 0.

[0029] In the above method, when it is necessary to study the influence of stress relief annealing, Step 6 is adjusted to: Adjust the heating and temperature control system to perform stress relief annealing on the rock mass sample, specifically by setting the temperature at the I thermocouple to 200 - 300 °C, holding for 1 - 3 hours, and then cooling to room temperature. After cooling, Steps 3 - 5 are repeated respectively to record the change of the residual stress of the same sample after stress relief annealing under the non-uniform temperature field; it also includes Step 7. Adjust the heating and temperature control system, change the temperature in the sample cell, and repeat Steps 3 - 6 to record the change of the residual stress of the same sample after stress relief annealing under different non-uniform temperature fields, so as to optimize the conditions of stress relief annealing.

[0030] The beneficial effects produced by the present invention are:

[0031] The device for measuring the residual stress of rock mass under non-uniform temperature proposed by the present invention realizes the non-uniform temperature control of the sample cell through two kinds of electric heating elements with different resistivity. Cooperating with the temperature monitoring of the thermocouple, the temperature control is realized through the PID temperature controller, so as to simulate the non-uniform temperature environment in which the rock mass is located under real working conditions. The in-situ test of the rock mass under non-uniform temperature conditions is carried out by the X-ray same-inclination method. The diffraction peak data of the rock mass at each same inclination angle ψ are collected by using the same-inclination method test, and then the evolution process of the residual stress of the rock mass under different non-uniform temperatures is determined. At the same time, the stress relief annealing can be carried out on the rock mass through the heating and temperature control system to reduce the existing residual stress of the rock mass, and the change of the residual stress after the stress relief annealing treatment of the same sample under different non-uniform temperature fields is recorded, so as to optimize the conditions of the stress relief annealing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings.

[0033] Figure 1 is a schematic structural diagram of the device for measuring the residual stress of rock mass under non-uniform temperature of the present invention;

[0034] Figure 2 is Figure 1 a structural decomposition diagram of the sample cell in the device;

[0035] Figure 3 is Figure 1 a schematic distribution diagram of the thermocouple and the heating element in the device;

[0036] Figure 4 is a flowchart of the method for measuring the residual stress of rock mass under non-uniform temperature of the present invention.

[0037] In the figure: 11, transparent beryllium window; 12, upper base of the sample cell; 13, lower base of the sample cell; 14, outer shell of the sample cell;

[0038] 21, thermocouple; 211, I thermocouple; 212, II thermocouple; 213, III thermocouple; 22, I heating element; 23, II heating element; 24, PID temperature controller;

[0039] 31, X-ray emitter; 32, X-ray detector; 33, X-ray diffraction sample stage; 34, X-ray diffractometer control system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] It should be noted that the illustrations provided in the embodiments of the present invention only schematically illustrate the basic concept of the present invention. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape and size of the components in actual implementation. The type, quantity and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0042] In the present invention, it should also be noted that when terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or positional relationship indicated thereby is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application. In addition, when terms such as "first" and "second" appear, they are only used for descriptive and distinguishing purposes and cannot be understood as indicating or implying relative importance.

[0043] Such as Figure 1-2As shown in the figure, the present invention proposes a device for measuring the residual stress of rock mass under non-uniform temperature, which includes a sample cell, a heating and temperature control system, and an X-ray diffractometer system. The sample cell includes an upper base 12 and a lower base 13 of the sample cell, and the rock mass sample to be detected is placed in the upper base 12 of the sample cell; the heating and temperature control system includes a thermocouple 21, a heating element, and a PID temperature controller 24; several thermocouples are arranged along a certain radial direction on the upper base 12 of the sample cell for measuring the temperature at different positions of the sample cell, and each thermocouple is electrically connected to the PID temperature controller 24 respectively to transmit the measured temperature signal to the PID temperature controller 24; several heating elements with different resistivities are arranged between the upper base 12 and the lower base 13 of the sample cell, and each heating element is electrically connected to the PID temperature controller 24 respectively; the PID temperature controller 24 compares the actual temperature measured by each thermocouple with the preset temperature, and makes the actual temperature approach the preset temperature by controlling the energization time of the heating element, thereby realizing the control of temperature. The X-ray diffractometer system includes an X-ray emitter 31, an X-ray detector 32, an X-ray diffraction sample stage 33, and an X-ray diffractometer control system 34; the sample cell is placed on the X-ray diffraction sample stage 33, the X-ray emitter 31 and the X-ray detector 32 are located above the sample cell, and the X-ray detector 32 receives the diffraction ray intensity and diffraction angle θ after the X-ray emitted by the X-ray emitter 31 enters the sample; the X-ray diffractometer control system 34 can change the same inclination angle ψ between the measured surface of the sample and the X-ray emitted by the X-ray emitter 31, and the adjustable range of the same inclination angle ψ is 0-45°.

[0044] In an embodiment of the present invention, the sample cell further includes a transparent beryllium window 11, which is made of metallic beryllium. The transparent beryllium window 11 is placed on the upper end surface of the upper base 12 of the sample cell, above the sample, and can effectively reduce the attenuation of X-rays.

[0045] In an embodiment of the present invention, the sample cell further includes a sample cell housing 14, and the sample cell housing 14 is fixedly connected to the upper base 12 of the sample cell in a detachable manner (such as threaded connection).

[0046] In an embodiment of the present invention, the upper base 12 and the lower base 13 of the sample cell are fixedly connected in a detachable manner (such as bolt connection).

[0047] In an embodiment of the present invention, a heating hole for inserting each heating element is opened horizontally at the connection between the upper base 12 and the lower base 13 of the sample cell, and each heating element is embedded into the heating hole in a straight line manner.

[0048] In an embodiment of the present invention, the upper base 12 of the sample cell can accommodate at most a cylindrical sample, and the size of the transparent beryllium window 11 is the aperture of the heating hole is

[0049] In one embodiment of the present invention, as Figure 3 shown, three thermocouples are arranged along a certain radial direction of the upper base 12 of the sample cell by means of embedding, namely, thermocouple I 211, thermocouple II 212 and thermocouple III 213. Among them, thermocouple I 211 and thermocouple III 213 are located at both ends respectively, and thermocouple II 212 is located at the midpoint between thermocouple I 211 and thermocouple III 213. All three thermocouples can monitor the temperature from 25 to 300 °C, and the temperature control accuracy is 0.1 °C. The temperature can be displayed on the panel of the PID temperature controller 24.

[0050] By selecting heating elements with different resistivities, a non-uniform temperature field can be loaded on the sample cell at the same time. The heat generated by the heating elements with different resistivities can be expressed by Joule's law (1), and the formula (1) is:

[0051] Q = I 2 Rt (1)

[0052] In formula (1), Q is the heat generated by the heating element, I is the current passing through the heating element, R is the resistance of the heating element, and t is the time for the current to pass through the heating element.

[0053] In one embodiment of the present invention, as Figure 3 shown, two heating elements are arranged in parallel, namely, heating element I 22 and heating element II 23. Among them, heating element I 22 is arranged between thermocouple I 211 and thermocouple II 212, and heating element II 23 is arranged between thermocouple II 212 and thermocouple III 213, so as to heat the sample cell with different temperature gradients.

[0054] Denote the position of thermocouple I 211 as x = 0, the position of thermocouple III 213 as x = D, then the position of thermocouple II 212 is x = D / 2. The temperature distribution in the sample cell with respect to the position x is calculated by formula (2), and the formula (2) is as follows:

[0055]

[0056] In formula (2), T x is the temperature at x in the sample cell, T 0 is the temperature at thermocouple I 211, and T D is the temperature at thermocouple III 213.

[0057] According to formula (2), various temperature distribution situations can be preset to discuss the change of residual stress of the same rock sample under different non-uniform temperature fields.

[0058] It is verified that the actual measured temperature at the II thermocouple 212 and T calculated by formula (2) D / 2 differ by no more than 1 °C, indicating that the temperature distribution of the non-uniform temperature field meets the expectations.

[0059] Before the experiment, embed the I thermocouple 211, II thermocouple 212, and III thermocouple 213 in the upper base 12 of the sample cell according to the design requirements and connect them to the PID temperature controller 24. Insert the I heating element 22 and II heating element 23 into the heating holes and connect them to the PID temperature controller 24. Then, fixedly connect the upper base 12 and the lower base 13 of the sample cell by bolts or screws; place the rock sample into the upper base 12 of the sample cell, place the transparent beryllium window 11 on the upper base 12 of the sample cell, and then tighten the sample cell housing 14; place and fix the sample cell on the X-ray diffraction sample stage 33. Install the X-ray emitter 31 and the X-ray detector 32 above the sample cell and connect them to the X-ray diffraction instrument control system 34, thus forming the device for measuring the residual stress of rock mass under non-uniform temperature of the present invention.

[0060] Based on the above device, the present invention also proposes a method for measuring the residual stress of rock mass under non-uniform temperature, as Figure 4 shown, the method includes the following steps:

[0061] Step 1: Cut and polish the rock sample into a cylindrical body, ensure that the test surface of the sample is flat and defect-free, place it in the upper base 12 of the sample cell, place the transparent beryllium window 11 above the sample, fixedly tighten the sample cell housing 14 and the upper base 12 of the sample cell by screw rotation, and place the sample cell on the X-ray diffraction sample stage 33.

[0062] Step 2: Turn on the heating and temperature control system for preheating, set the temperature to the preset temperature, and wait until the temperature difference between the I thermocouple 211 and the III thermocouple 213 stabilizes at 5 - 10 °C.

[0063] Step 3: After the temperature in Step 2 stabilizes, start the XRD test. Set the X-ray diffraction instrument system to the preset conditions, with the same inclination angle ψ being 0 °, the measurement range being 10 - 80 °, the scanning time being 10 min, conduct the first characterization, and obtain the sample diffraction peak data.

[0064] Step 4: Use the X-ray diffraction instrument control system 34 to change the same inclination angle ψ between the transparent beryllium window 11 and the X-ray emitter 31, increase it by 15 ° each time up to 45 °, conduct XRD tests at multiple same inclination angles, and record the highest diffraction intensity and its corresponding diffraction angle θ at each same inclination angle.

[0065] Step 5: Calculate the stress value σ of the sample at each same inclination angle ψ. Specifically, calculate the lattice plane spacing d of the sample at each same inclination angle ψ through formula (3). ψ , and formula (3) is as follows:

[0066] nλ = 2d ψ ·sinθ (3)

[0067] In formula (3), n is the diffraction order, usually taken as 1, representing the first-order diffraction; λ represents the wavelength of the X-ray source; d ψ is the lattice plane spacing of the sample under test at ψ; θ is the diffraction angle.

[0068] Then calculate the stress value σ at each same inclination angle ψ through the elastic theory formula (4). Formula (4) is as follows:

[0069]

[0070] In formula (4), σ is the stress value at each same inclination angle; E is the Young's modulus corresponding to the sample; ν is the Poisson's ratio corresponding to the sample; Δd is the change value of the lattice plane spacing of the sample at each same inclination angle, and Δd = d ψ -d 0 ; d 0 is the lattice plane spacing of the sample when the same inclination angle is 0.

[0071] Then, with the stress value σ at each same inclination angle as the vertical axis and the square of the sine value of the same inclination angle sin 2 ψ as the horizontal axis, plot an image and perform linear fitting on the data to obtain the residual stress existing at the measurement point of the sample.

[0072] Step 6: Adjust the heating and temperature control system, change the temperature in the sample cell, heat it at a temperature gradient of 25°C increment each time according to the I thermocouple 211, and repeat steps 3 - 5 to record the change curve of the residual stress of the same sample under different non-uniform temperature field conditions.

[0073] Based on the above device, the present invention also proposes a method for measuring the change in residual stress of a rock mass after stress-relieving annealing under a non-uniform temperature field. Steps 1 to 5 of this method are the same as Steps 1 to 5 of the above method for measuring the residual stress of a rock mass under a non-uniform temperature. The difference is that Step 6 is to adjust the heating and temperature control system to perform stress-relieving annealing on the rock mass sample. Specifically, set the temperature at the I thermocouple to 250 °C, keep it warm for one hour, and then cool it down to room temperature. After cooling, repeat Steps 3 to 5 to record the change in residual stress of the same sample after stress-relieving annealing under a non-uniform temperature field; it also includes Step 7, adjust the heating and temperature control system, change the temperature in the sample pool, and repeat Steps 3 to 6 to record the change in residual stress of the same sample after stress-relieving annealing under different non-uniform temperature fields, so as to optimize the conditions for stress-relieving annealing, such as time, temperature, heating rate, etc.

[0074] It should be noted that according to the needs of implementation, each step / component described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0075] The sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0076] It should be understood that those of ordinary skill in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A device for measuring residual stress in rock mass at non-uniform temperature, characterized in that: Including sample pool, heating temperature control system and X-ray diffractometer system; The sample pool comprises an upper base and a lower base of the sample pool, and the rock sample to be tested is placed in the upper base of the sample pool; the heating and temperature control system comprises a thermocouple, a heating element and a PID temperature controller; a plurality of the thermocouples are arranged along a radial direction on the upper base of the sample pool for measuring the temperature at different positions of the sample pool, and each thermocouple is electrically connected to the PID temperature controller respectively to transmit the measured temperature signal to the PID temperature controller; a plurality of heating elements with different resistivities are arranged between the upper base and the lower base of the sample pool, and each heating element is electrically connected to the PID temperature controller respectively; the PID temperature controller compares the actual temperature measured by the thermocouple with the preset temperature, and makes the actual temperature approach the preset temperature by controlling the power-on time of the heating element, thereby realizing the control of non-uniform temperature; The X-ray diffractometer system includes an X-ray emitter, an X-ray detector, an X-ray diffraction sample stage and an X-ray diffractometer control system; the sample pool is placed on the X-ray diffraction sample stage, the X-ray emitter and the X-ray detector are located above the sample pool and are respectively connected to the X-ray diffractometer control system by signals, the X-ray detector receives the intensity and diffraction angle θ of the rays diffracted after the X-ray emitter enters the sample, and transmits the signal to the X-ray diffractometer control system, and the X-ray diffractometer control system can change the co-inclination angle ψ between the sample test surface and the X-ray emitter.

2. The device for measuring residual stress of rock mass at non-uniform temperature according to claim 1, characterized in that: The sample pool also includes a transparent beryllium window, which is made of metal beryllium. The transparent beryllium window is placed on the upper end surface of the upper base of the sample pool and is located above the sample.

3. The device for measuring residual stress of rock mass at non-uniform temperature according to claim 1, characterized in that: The sample pool also includes a sample pool shell, and the sample pool shell is fixedly connected to the sample pool upper base in a detachable manner; the sample pool upper base is fixedly connected to the sample pool lower base in a detachable manner.

4. The device for measuring residual stress of rock mass at non-uniform temperature according to claim 1, characterized in that: A heating hole for inserting each heating element is opened in the horizontal direction at the connection between the upper base and the lower base of the sample cell, and each heating element is pre-buried in the heating hole in a straight line.

5. The device for measuring residual stress of rock mass at non-uniform temperature according to claim 1, characterized in that: The thermocouples are pre-embedded in three along a radial direction of the base on the sample pool, namely thermocouple I, thermocouple II and thermocouple III, wherein thermocouple I and thermocouple III are located at both ends respectively, and thermocouple II is located at the midpoint of thermocouple I and thermocouple III.

6. The device for measuring residual stress of rock mass at non-uniform temperature according to claim 5, characterized in that: Two heating elements are arranged in parallel, namely, heating element I and heating element II, wherein heating element I is arranged between thermocouple I and thermocouple II, and heating element II is arranged between thermocouple II and thermocouple III.

7. The device for measuring residual stress of rock mass at non-uniform temperature according to claim 6, characterized in that: Let the position of thermocouple I be x=0, the position of thermocouple III be x=D, then the position of thermocouple II be x=D / 2, and the distribution of the temperature in the sample pool about the position x is calculated by formula (2), which is as follows: In formula (2), T x is the temperature at x in the sample cell, T0 is the temperature at the thermocouple I, T D is the temperature at the III thermocouple; By presetting a variety of temperature distribution conditions, the changes in residual stress of the same rock sample under different non-uniform temperature fields can be compared.

8. A method for measuring residual stress in a rock mass at a non-uniform temperature, characterized in that: The device according to any one of claims 1 to 7 comprises the following steps: Step 1: Place the cut and polished rock sample on the upper base of the sample pool, place the transparent beryllium window above the sample, and place the sample pool on the X-ray diffraction sample stage; Step 2, turn on the heating temperature control system for preheating, set the temperature to the preset temperature, and wait until the temperature difference between the thermocouple I and the thermocouple III is stable at 5-10°C; Step 3, after the temperature stabilizes, start the XRD test, set the X-ray diffractometer system to the preset conditions, the same inclination angle ψ is 0°, the measurement range is 10-80°, and the first characterization is performed to obtain the highest diffraction intensity of the sample and its corresponding diffraction angle θ; Step 4, using the X-ray diffractometer control system to change the co-inclination angle ψ between the transparent beryllium window and the X-ray emitter, perform XRD tests at multiple co-inclination angles, and record the highest diffraction intensity and its corresponding diffraction angle θ at each co-inclination angle; Step 5: Calculate the stress value σ of the sample at each inclination angle ψ, and use the stress value σ at each inclination angle as the vertical axis and the square of the sine value of the inclination angle sin 2 ψ is the horizontal axis to draw the graph, and the data is linearly fitted to obtain the residual stress at the test point of the sample; Step 6: Adjust the heating and temperature control system to change the temperature in the sample pool, and repeat steps 3 to 5 to record the residual stress variation curve of the same sample under different non-uniform temperature field conditions.

9. The method for measuring residual stress of rock mass at non-uniform temperature according to claim 8, characterized in that: In step 5, the interplanar spacing d of the sample at each isopiplinic angle ψ is calculated by formula (3): ψ , formula (3) is: nλ=2d ψ ·sinθ (3) In formula (3), n is the diffraction order, usually 1, indicating the first order diffraction; λ is the wavelength of the X-ray source; d ψ is the interplanar spacing of the sample under test at the same inclination angle ψ; θ is the diffraction angle; Then, the stress value σ at each inclination angle ψ is calculated by the elastic theory formula (4), which is: In formula (4), σ is the stress value at each same inclination angle; E is the Young's modulus corresponding to the sample; ν is the Poisson's ratio corresponding to the sample; Δd is the change in the sample interplanar spacing at each inclination angle, Δd = d ψ -d0; d0 is the interplanar spacing of the sample when the isopipular angle is 0.

10. The method for measuring residual stress of rock mass at non-uniform temperature according to claim 8, characterized in that: When the influence of stress relief annealing needs to be studied, step 6 is adjusted to: adjust the heating temperature control system, and perform stress relief annealing on the rock sample, specifically, set the temperature at the I thermocouple to 200-300°C, keep it warm for 1-3 hours, then cool it down to room temperature, and repeat steps 3-5 after cooling down, and record the change of residual stress of the same sample after stress relief annealing under non-uniform temperature field; The method also includes step 7, adjusting the heating temperature control system, changing the temperature in the sample pool, and repeating steps 3 to 6, recording the change of residual stress of the same sample after stress relief annealing treatment under different non-uniform temperature fields, so as to optimize the stress relief annealing conditions.

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