Real-time imaging method for the evolution of rock mass damage state in deep geological environment

Abstract

The present invention discloses a real-time imaging method for the evolution of the damage state of rock masses in a deep-earth environment. An adjacent longitudinal wave receiving sensor and transverse wave receiving sensor are used to form a receiving sensor group, and then the longitudinal wave velocity and transverse wave velocity are determined based on the start and end times of the received longitudinal wave and transverse wave signals. Furthermore, the damage variable is calculated according to the wave velocity. By arranging excitation sensors and receiving sensors at different positions, the overall damage state distribution of the tested rock mass can be obtained. Further, by changing the deep-earth conditions, an evolution image of the damage state of the tested rock mass can be obtained, providing effective data support for the analysis of the intact state of rock masses under deep-earth conditions.

Description

Technical Field

[0001] This application belongs to the technical field of deep geological engineering, and relates to the evolution of the damage state of rock masses in a deep geological environment, especially to a real-time imaging method for the evolution of the damage state of rock masses in a deep geological environment. Background Art

[0002] Rock masses will be damaged under the action of external loads. The damage accumulates gradually with the evolution of time, which will eventually lead to the failure of the rock masses. However, rock masses are natural geological materials with internal heterogeneity and anisotropy, which will inevitably lead to different internal damage evolution states of the rock masses. For the rock masses in deep underground engineering, they are not only affected by the coupling of the temperature field, stress field, seepage field, etc. existing in the deep part, but also the structural state inside the rock masses will change and deteriorate due to the changes in load conditions and deformations caused by engineering construction disturbances, ultimately having an adverse impact on the stability and safety of engineering construction and operation. Therefore, it is of great significance and value to master the damage distribution characteristics of deep geological rock masses under the influence of comprehensive factors such as occurrence conditions and disturbances, and to establish the correlation between different types of parameters for studying the stability of deep geological engineering rock masses and formulating relevant measures.

[0003] There are various technical means for testing the internal damage state of rock masses in the laboratory, such as industrial CT scanning, nuclear magnetic resonance scanning, acoustic emission monitoring, elastic wave testing, etc. How to intuitively display the changes and distribution states of relevant parameters inside the rock masses through imaging methods is also a difficult problem in current research. In terms of imaging the internal state of rocks, CT scanning and nuclear magnetic resonance scanning are currently applied. CT scanning is based on the principle of X-ray transmission for imaging. Although this method can observe the internal structural state of rocks, it usually takes more than 2 hours to complete one scan, while the single mechanical test process of rocks is usually about 10 minutes. Obviously, this method cannot meet the requirements of real-time imaging for scanning speed and accuracy, and currently this method cannot achieve comprehensive testing under complex coupling conditions in deep geological environments.

[0004] Nuclear magnetic resonance scanning is based on the fact that the tested rock can be saturated with water or oil, and then the distribution of hydrogen atoms in it is tested, and based on this, the internal structural state of the rock is imaged. This technology not only requires that there are no metal minerals in the tested object, but also still cannot achieve comprehensive testing under complex coupling conditions in deep geological environments. Although acoustic emission technology can display the evolution of the damage location of rock masses, the display method is presented in the form of a scatter plot, which is not only not intuitive enough, but also cannot achieve the quantification of the internal damage state distribution of rock masses, and its accuracy is low and the effect is poor. Currently, it is mostly used as a qualitative reference.

[0005] In summary, neither CT scans, nor nuclear magnetic resonance scans and acoustic emission monitoring can achieve real-time quantitative display of the internal damage state of rock masses, nor can they establish a correlation between the test results and the relevant damage states. However, the elastic wave velocity changes in real time with the change of the rock mass state. Therefore, based on indoor real-time tests, the longitudinal and transverse waves of elastic waves can be used as a link to build relevant parameters of the rock mass to achieve real-time imaging of the relevant state of the rock mass. However, there are still many problems in indoor test and analysis: (1) The analysis of the rock state is only based on the compression wave, and the shear wave test is not effectively considered; (2) It is not possible to obtain synchronous signals of different types of waves by homologous excitation; (3) It is not possible to achieve imaging of the evolution process of the rock mass damage state; (4) The analysis test conditions do not consider the deep and complex coupling factors; (5) The results shown are not intuitive and cannot reflect the real distribution and change state. Summary of the Invention

[0006] The purpose of the present invention is to provide a real-time imaging method for the evolution of the damage state of rock masses in a deep geological environment to achieve real-time imaging of the evolution process of the damage state of rock masses in view of the above technical problems existing in the prior art.

[0007] To achieve the above purpose, the present invention adopts the following method solutions.

[0008] The real-time imaging method for the evolution of the damage state of rock masses in a deep geological environment provided by the present invention includes the following steps:

[0009] S1 Under given deep geological conditions, an excitation signal is sent by an excitation sensor installed on the test rock mass, and then the signal is received by a receiving sensor installed on the test rock mass; the number of excitation sensors installed on the test rock mass is more than two, the number of receiving sensors installed on the test rock mass is more than two, the types of the receiving sensors include longitudinal wave (P-wave) sensors and transverse wave (S-wave) sensors, different types of receiving sensors are arranged staggeredly, and an adjacent longitudinal wave receiving sensor and transverse wave receiving sensor form a receiving sensor group;

[0010] S2 For any excitation sensor, obtain the longitudinal wave velocity V p received by the longitudinal wave receiving sensor in each group of receiving sensors, and the transverse wave velocity V S received by the transverse wave receiving sensor;

[0011] S3 For each group of receiving sensors, according to the following damage variable model, calculate the damage variable at the corresponding position of each group of receiving sensors based on the longitudinal wave velocity and the transverse wave velocity:

[0012]

[0013] Where: α is the damage variable, [0,1]; VP is the longitudinal wave propagation velocity (m / s); V S is the shear wave propagation velocity (m / s); ρ is the rock density (g / cm 3 ); is the ratio of strain invariants, with a value range of: I1 = ε ii , I2 = ε ij ε ij , I1, I2 are the first and second invariants of the elastic strain tensor, ε ii 、ε ij are measured, i = 1, 2, 3, j = 1, 2, 3, 1, 2, 3 represent the three directions of a given coordinate system; μ0, μ1, γ1 are constants related to the material; λ is the Lamé constant:

[0014] And use it as the damage state distribution between the excitation sensor and the set of receiving sensors on the tested rock mass;

[0015] S4 Repeat steps S2 - S3 to obtain the damage state distribution between all excitation sensors and each set of receiving sensors on the tested rock mass;

[0016] S5 Change the deep - earth conditions, repeat steps S1 - S4 to obtain the evolution images of the rock mass damage state corresponding to different deep - earth states, and the real - time change images of the mechanical damage state of the rock mass corresponding to the change process of the deep - earth state can be obtained.

[0017] In the above step S1, the deep - earth conditions are the temperature field, stress field (i.e., pressure environment), seepage field, load, etc. where the tested rock mass is located, which can be realized by a triaxial pressure chamber for simulating the deep - earth environment (see CN202011431049.4).

[0018] The installation methods of the excitation sensor and the receiving sensor include at least one of the following methods:

[0019] (1) The excitation sensor is installed at one end of the load - loading end of the tested rock mass in the deep - earth environment simulation chamber, and can be set in the loading pad set at one end of the tested rock mass; in the preferred implementation, each excitation sensor can be evenly arranged radially and / or circumferentially along the loading pad; when there is a seepage channel on the tested rock mass, the excitation sensor can be arranged in a staggered manner with the seepage channel; the receiving sensor is installed at the opposite end of the load - loading end of the tested rock mass; it can be set in the loading pad set at the other end of the rock mass sample; in the preferred implementation, each receiving sensor can be evenly arranged radially and / or circumferentially along the loading pad; when there is a seepage channel on the tested rock mass, the receiving sensor can be arranged in a staggered manner with the seepage channel; the number of excitation sensors and receiving sensors can be the same or different.

[0020] (2) The excitation sensors and the receiving sensors are arranged uniformly along the axial direction of the tested rock mass; the number of excitation sensors and receiving sensors distributed along the axial direction of the tested rock mass can be the same or different.

[0021] In the above step S2, the longitudinal wave velocity V p is calculated according to the following formula:

[0022] V p = L P / △t P

[0023] In the formula, L P is the distance of the tested rock mass passed by the connection line from the excitation sensor to the longitudinal wave receiving sensor, and △t P is the time for the corresponding longitudinal wave received by the longitudinal wave receiving sensor to pass through the tested rock mass;

[0024] The shear wave velocity V S is calculated according to the following formula:

[0025] V S = L S / △t S

[0026] In the formula, L S is the distance of the tested rock mass passed by the connection line from the excitation sensor to the shear wave receiving sensor, and △t S is the time for the corresponding shear wave received by the shear wave receiving sensor to pass through the tested rock mass;

[0027] The above △t P can be calculated by the following formula:

[0028] △t P = t 1P - t0 - t 2P

[0029] In the formula, t 1P is the longitudinal wave receiving time of the longitudinal wave sensor (i.e., the arrival time of the longitudinal wave), and t0 is the excitation sensor sending time (i.e., the starting time of the longitudinal wave). t 2P is the time consumed for the corresponding longitudinal wave received by the longitudinal wave receiving sensor to propagate through the loading block or the non-rock mass interior; if both the excitation sensor and the receiving sensor are set in the cushion block, it is the total time through the cushion blocks at both the excitation and receiving ends; if the excitation sensor is set in the loading cushion block and the receiving sensor is directly set on the rock mass sample, then this time t 2p is the time consumed for the received wave to pass through the excitation end cushion block, and vice versa, it is the time consumed for passing through the receiving end cushion block; if both the excitation sensor and the receiving sensor are set on the side of the tested rock mass and in direct contact with the rock mass, then t 2P = 0.

[0030] The above-mentioned △t s can be calculated by the following formula:

[0031] △t S = t 1S - t0 - t 2S

[0032] In the formula, t 1S is the arrival time of the shear wave received by the shear wave sensor (i.e., the arrival moment of the shear wave), and t0 is the transmission time of the excitation sensor (i.e., the starting moment of the shear wave). t 2S is the time consumed by the corresponding shear wave received by the shear wave receiving sensor during propagation through the loading block or the non-rock mass; if both the excitation sensor and the receiving sensor are set in the cushion block, it is the total time through the cushion blocks at both the excitation and receiving ends; if the excitation sensor is set in the loading cushion block and the receiving sensor is directly set on the rock mass sample, then this time t 2S is the time consumed by the received wave through the excitation-end cushion block, and vice versa, it is the time consumed by the receiving-end cushion block; if both the excitation sensor and the receiving sensor are set on the side of the tested rock mass and in direct contact with the rock mass, then t 2S = 0.

[0033] The above-mentioned t 2p and t 2S can be obtained by separately testing the loading cushion block or the non-rock mass part. The excitation sensor sends an excitation signal to the separate loading cushion block, and then it is received by the receiving sensor, and then it is calculated by using the difference between the signal receiving moment and the signal excitation moment. For another example, if there is other material with a certain thickness padded between the excitation sensor and the receiving sensor connection lines in addition to the tested rock mass, then the time consumed by the corresponding sound wave passing through the other material can also be obtained by directly installing the excitation sensor and the receiving sensor on the material with the corresponding thickness for testing.

[0034] In the above-mentioned step S3, the above-mentioned damage variable model is obtained by analyzing the damage variable expressed by the double wave:

[0035]

[0036]

[0037]

[0038]

[0039] From the above formulas (1) and (2), it is obtained that:

[0040]

[0041] In the formula, μ e= μ - γξ / 2, the expression of the damage variable μ = μ0 + μ1α, γ = γ1α, where μ = μ0, γ = 0 represents the initial state of the material without fracture. Substituting into the above formula (4), the damage variable model of the above damage variable α can be obtained.

[0042] The obtained damage state is used to characterize the damage state distribution between the corresponding excitation sensor and this group of receiving sensors on the tested rock mass, that is, the calculated damage variable is used to characterize the damage variable distribution in the area between the corresponding excitation sensor and the line connecting the two receiving sensors on the tested rock mass.

[0043] Through the above step S4, the damage state distribution between all excitation sensors and each group of receiving sensors on the tested rock mass under given deep-earth conditions can be obtained, and then the overall damage state distribution of the tested rock mass can be determined. When there are intersection points between the lines connecting the positions of each excitation sensor to each group of receiving sensors, a tiny unit of the tested rock mass is formed by these intersection points, and the maximum loss variable calculated at this position is used as the damage variable corresponding to this tiny unit.

[0044] In the above step S5, by changing the deep-earth conditions (including temperature field, stress field, seepage field, or / and load), repeating the above steps S1 - S4 can obtain the overall damage state distribution of the tested rock mass under different deep-earth conditions, and then based on the overall damage state distribution of the tested rock mass under different deep-earth conditions, an image of the damage state evolution of the tested rock mass can be obtained.

[0045] The real-time imaging method for the damage state evolution of rock mass in deep-earth environment provided by the present invention has the following beneficial effects:

[0046] (1) In the present invention, an excitation signal is sent by an excitation sensor installed on the tested rock mass. A group of receiving sensors is composed of adjacent longitudinal wave receiving sensors and transverse wave receiving sensors. Then, based on the start and end moments of the received longitudinal wave and transverse wave signals, the longitudinal wave and transverse wave velocities are determined, and further the damage variable is calculated according to the wave velocities; by arranging excitation sensors and receiving sensors at different positions, the overall damage state distribution of the tested rock mass can be obtained; further, by changing the deep-earth conditions, an image of the damage state evolution of the tested rock mass can be obtained, providing effective data support for the analysis of the intact state of rock mass under deep-earth conditions;

[0047] (2) Since different types of receiving sensors in the present invention receive the excitation signal sent by the same excitation sensor, synchronous testing of different receiving sensors can be realized, thus ensuring the authenticity of the received signals; and the anisotropic differences of damage can be judged synchronously;

[0048] (3) The image of the damage state evolution obtained by the present invention is intuitive and can reflect the actual distribution and change state;

[0049] (4) The correlation established by the present invention with other mechanical or influencing conditions of the rock mass is simple and fast, and the results are true and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0051] Figure 1 It is a schematic flow diagram of a real-time imaging method for the evolution of the damage state of a rock mass in a deep geological environment.

[0052] Figure 2 It is a schematic layout diagram of excitation sensors and receiving sensors provided on the first type of test rock mass; among them, (a) is a sectional view from the front view angle, (b) is a sectional view from the top view angle; (c) is a schematic diagram of multiple excitation sensors sending and multiple receiving sensors receiving.

[0053] Figure 3 It is a schematic layout diagram of excitation sensors and receiving sensors provided on the second type of test rock mass; among them, (a) is a sectional view from the front view angle, (b) is a sectional view from the top view angle; (c) is a schematic diagram of a single excitation sensor sending and multiple receiving sensors receiving.

[0054] Figure 4 It is a schematic layout diagram of excitation sensors and receiving sensors provided on the third type of test rock mass.

[0055] Figure 5 It is a schematic diagram of the real-time evolution of the damage state of the rock mass; among them, Rc represents the compressive strength / or the maximum bearing capacity. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0057] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0058] The present invention is realized by arranging more than two excitation sensors and more than two receiving sensors on a test rock mass. The wave type of the excitation sensor is a longitudinal wave (i.e., a compression wave). The wave types of the receiving sensors include longitudinal waves (P waves) and transverse waves (S waves). Different types of receiving sensors are arranged staggeredly, and adjacent longitudinal wave receiving sensors and transverse wave receiving sensors form a receiving sensor group. Both the excitation sensors and the receiving sensors are ultrasonic sensors.

[0059] The upper and lower ends of the test rock mass A-9 are respectively installed in a triaxial pressure chamber through an upper loading pad A-3 and a lower loading pad A-4 (see CN202011431049.4). The upper loading pad A-3 and the lower loading pad A-4 are of U-shaped structures, and a loading pad cover plate A-2 is provided at the open end, and the two are connected by a connecting bolt A-1. First seepage channels A-7 and second seepage channels A-8 are respectively opened and installed at the middle positions of the upper loading pad A-3 and the lower loading pad A-4.

[0060] The installation methods of the excitation sensors and the receiving sensors include at least one of the following methods:

[0061] (1) The excitation sensors are installed at one end of the load loading end of the test rock mass in the deep earth environment simulation chamber, and can be arranged in the loading pads provided at one end of the test rock mass; in a specific implementation manner: each excitation sensor can be uniformly arranged along the radial direction or / and the circumferential direction of the loading pad; when there is a seepage channel provided on the test rock mass, the excitation sensors can be arranged in a staggered manner with the seepage channel;

[0062] The receiving sensors are installed at the opposite end of the load loading end of the test rock mass; they can be arranged in the loading pads provided at the other end of the rock mass sample; in a specific implementation manner: each receiving sensor can be uniformly arranged along the radial direction or / and the circumferential direction of the loading pad; when there is a seepage channel provided on the test rock mass, the receiving sensors can be arranged in a staggered manner with the seepage channel; for different types of receiving sensors, their positions can be staggered one by one, aiming to facilitate real-time imaging of the rock mass state under deep earth conditions using homologous double waves (i.e., longitudinal waves and transverse waves); this is because rocks are not ideal homogeneous bodies after all, and there must be anisotropy, so using alternately installed longitudinal wave and transverse wave receiving sensors can ensure that the test results are more in line with the actual situation.

[0063] The numbers of the excitation sensors and the receiving sensors can be the same or different.

[0064] (2) The excitation sensors and the receiving sensors are arranged uniformly along the axial direction of the test rock mass; the number of excitation sensors and receiving sensors distributed along the axial direction of the test rock mass can be the same or different. For different types of receiving sensors, their positions can be staggered one by one. The purpose is to facilitate real-time imaging of the state of the rock mass under deep-earth conditions using homologous dual waves (i.e., longitudinal waves and transverse waves). Since rocks are not ideal homogeneous bodies and there must be anisotropy, using alternately installed longitudinal wave and transverse wave receiving sensors can ensure that the test results are more in line with the actual situation.

[0065] Figures 2 - 4 Multiple arrangement methods of the excitation sensors and the receiving sensors are listed.

[0066] Example 1 Figure 2 An example is provided in which for a cylindrical test rock mass, excitation sensors and receiving sensors are respectively arranged at the load loading end and the opposite end. The number of excitation sensors is 4, and the number of receiving sensors is 4. The 4 excitation sensors A-5 are installed at the bottom of the U-shaped structure of the upper loading pad, and the 4 excitation sensors A-5 are arranged uniformly along the circumferential direction of the upper loading pad; the 4 receiving sensors A-6 are arranged radially along the lower loading pad and installed at the bottom of the U-shaped structure of the lower loading pad, and the 4 receiving sensors A-6 are arranged uniformly along the circumferential direction of the lower loading pad; for different types of receiving sensors, their positions are staggered one by one.

[0067] Example 2 Figure 3 An example is provided in which for a cylindrical test rock mass, excitation sensors and receiving sensors are respectively arranged at the load loading end, the opposite end, and along the vertical direction of the test rock mass. The number of excitation sensors is 13 (A-5, A-10), and the number of receiving sensors is 13 (A-6, A11). The 4 excitation sensors A-5 are installed at the bottom of the U-shaped structure of the upper loading pad, and the 4 excitation sensors A-5 are arranged uniformly along the circumferential direction of the upper loading pad; the 4 receiving sensors A-6 are arranged radially along the lower loading pad and installed at the bottom of the U-shaped structure of the lower loading pad, and the 4 receiving sensors A-6 are arranged uniformly along the circumferential direction of the lower loading pad. Additionally, the 9 excitation sensors A-10 and the 9 receiving sensors A11 are distributed uniformly along the axial direction of the test rock mass, and the positions of the excitation sensors A-10 and the receiving sensors A11 correspond one by one. For different types of receiving sensors, their positions are staggered one by one.

[0068] Example 3 Figure 4An example is provided in which an excitation sensor and a receiving sensor are respectively arranged vertically along a cylindrical test rock mass. The number of excitation sensors is 9 (A-10); the number of receiving sensors is 27 (A-11), and the 27 receiving sensors are divided into three columns, with 9 receiving sensors in each column. The 9 excitation sensors A-10 are evenly distributed along the axial direction of the test rock mass, and the three columns of receiving sensors are all evenly distributed along the axial direction of the test rock mass, and the excitation sensor group and the three columns of receiving sensors are evenly distributed along the circumferential direction of the test rock mass. For different types of receiving sensors, their positions are staggered one by one.

[0069] In addition to the above-mentioned cylindrical test rock mass, the present invention can also be directed to test rock masses of other shapes, such as columnar structure test rock masses with triangular, square, regular polygon cross-sections, etc.

[0070] For the excitation sensors and receiving sensors installed at the upper and lower ends of the test rock mass, during use, the excitation sensors are excited separately. For example, after the first excitation, different types of receiving sensors installed at the receiving end start to synchronously receive the arriving signals; then the second excitation sensor is excited, and all the sensors at the receiving end still synchronously receive; and so on, until all the signals at the excitation end are excited one by one.

[0071] For the excitation sensors and receiving sensors installed axially on the surface of the test rock mass, during use, when an excitation sensor emits an excitation signal, the excitation sensors installed on the same surface do not receive the signal emitted by this excitation sensor (for example Figure 4 , for the excitation sensors installed in the loading pad, if an excitation sensor A-5 is excited, since several other excitation sensors A-5 and the currently emitting excitation signal are on the same plane, they are not used as receiving sensors. However, the excitation sensor A-10 installed on the side as an excitation sensor can be used as a receiving sensor for receiving signals, for example Figure 4 the excitation sensor installed on the side of the rock in Figure 4 ; similarly,

[0072] From the above analysis, it can be known that since multiple excitation and reception sensors are arranged both longitudinally and transversely, each excitation sensor can be directly connected point-to-point with other sensors, and these straight line segments of point-to-point connections can form a dense intertwined grid (as shown in (c) of Figure 2 and (c) of Figure 3 ). Whether in the horizontal direction perpendicular to the axis of the specimen or in the vertical direction parallel to the axis of the specimen, any slice of these intertwined grids can form a plane, and the superposition of these infinitely many horizontal and vertical planes can form a three-dimensional specimen. Therefore, each intersection point can be regarded as a tiny unit that makes up the specimen, and the material parameters corresponding to each tiny unit can be considered the same. So, as long as the material state of each intersection point (or tiny unit) is known, the material state distribution of the entire specimen can be displayed in the form of an image, that is, imaging.

[0073] Embodiment 1

[0074] The real-time imaging method for the evolution of the damage state of rock mass under deep-earth conditions based on homologous dual waves provided in this embodiment, as shown in Figure 1 , includes the following steps:

[0075] S1 Under given deep-earth conditions, an excitation signal is sent by an excitation sensor installed on the test rock mass, and then the signal is received by a reception sensor installed on the test rock mass.

[0076] The excitation sensor and the reception sensor are arranged as described above.

[0077] S2 For any excitation sensor, obtain the longitudinal wave velocity V p received by the longitudinal wave reception sensors in each group of reception sensors, and the transverse wave velocity V S received by the transverse wave reception sensors.

[0078] According to the arrangement of the excitation sensor and the reception sensor, the waveforms (longitudinal wave Vp or transverse wave Vs) recorded by each reception sensor, the excitation start time t0 (Vp or Vs), and the arrival time t 1P (Vp) or t 1S (Vs) corresponding to this wave can be obtained.

[0079] According to the arrangement of the excitation sensor and the reception sensor, the distances (L P or L S ) through which the connection lines between each excitation sensor and each reception sensor pass through the specimen can also be determined, as well as the time t 2P (Vp) or t 2S(Vs) (obtained by separate test). When both the excitation sensor and the receiving sensor are set on the side of the test rock mass and in direct contact with the rock mass, then t 2P = 0, t 2S = 0.

[0080] Then, the longitudinal wave velocity V p is calculated according to the following formula:

[0081] V p = L P / △t P

[0082] In the formula, L P is the distance of the test rock mass passed by the connection line between the excitation sensor and the longitudinal wave receiving sensor, and △t P is the time for the corresponding longitudinal wave received by the longitudinal wave receiving sensor to pass through the test rock mass.

[0083] The above △t P can be calculated by the following formula:

[0084] △t P = t 1P - t0 - t 2P

[0085] In the formula, t 1P is the longitudinal wave receiving time of the longitudinal wave sensor (i.e., the arrival time of the longitudinal wave), t0 is the excitation sensor sending time (i.e., the starting time of the longitudinal wave), and t 2P is the time consumed for the corresponding longitudinal wave received by the longitudinal wave receiving sensor to pass through the loading block or propagate inside the non-rock mass. If both the excitation sensor and the receiving sensor are set on the side of the test rock mass and in direct contact with the rock mass, then t 2P = 0.

[0086] The shear wave velocity V S is calculated according to the following formula:

[0087] V S = L S / △t S

[0088] In the formula, L S is the distance of the test rock mass passed by the connection line between the excitation sensor and the shear wave receiving sensor, and △t S is the time for the corresponding shear wave received by the shear wave receiving sensor to pass through the test rock mass;

[0089] The above △t s can be calculated by the following formula:

[0090] △t S = t 1S - t0 - t 2S

[0091] where t 1S is the time when the shear wave sensor receives the shear wave (i.e., the arrival time of the shear wave), t0 is the transmission time of the excitation sensor (i.e., the starting time of the shear wave), and t 2S is the time consumed by the corresponding shear wave received by the shear wave receiving sensor during propagation through the loading block or the non-rock mass interior. If the loading and receiving sensors are set on the side of the test rock mass and in direct contact with the rock mass, then t 2S = 0.

[0092] The properties of the rock mass mainly depend on the mechanical parameters of the rock mass under the combined influence of various conditions such as corresponding temperature, seepage, stress, and load. The essence of the difference in mechanical parameters is the different internal damage states of the rock mass. Therefore, the above-mentioned various combined condition changes will lead to different damage states of the rock mass. Even within the same rock, due to the differences in the above-mentioned certain conditions, the damage states of different parts will also be different, and the damage state of the same part is also changing. As described in the "imaging principle" part above, it can be seen that the change in the intact state of a certain part indicates that the corresponding wave velocity will change. The core is that the corresponding damage state has changed. Therefore, the change in wave velocity can be used as a variable to calculate the change in the damage state, and an image of the change in the damage state can be drawn accordingly. For the specific operation, see steps S3 - S5.

[0093] For each group of receiving sensors, according to the following damage variable model, the damage variable at the corresponding position of each group of receiving sensors is calculated based on the longitudinal wave velocity and the shear wave velocity:

[0094]

[0095] where: α is the damage variable, [0, 1]; V P is the longitudinal wave propagation velocity (m / s); V S is the shear wave propagation velocity (m / s); ρ is the rock density (g / cm 3 ); is the ratio of strain invariants, and the value range is: I1 = ε ii , I2 = ε ij ε ij , I1 and I2 are the first and second invariants of the elastic strain tensor, and ε ii , ε ij are measured (which can be measured by a deformation measurement extensometer set on the outer side of the test rock mass, such as MTS632.92H - 03), i = 1, 2, 3, j = 1, 2, 3; μ0, μ1, γ1 are constants related to the material; λ is the Lamé constant:

[0096] And use it to characterize the damage state distribution between the excitation sensor and this group of receiving sensors on the test rock mass.

[0097] The obtained damage state is used to characterize the damage state distribution between the corresponding excitation sensor and this group of receiving sensors on the test rock mass, that is, the calculated damage variable is used to characterize the damage variable distribution in the area between the corresponding excitation sensor and the line connecting the two receiving sensors of this group on the test rock mass.

[0098] S4 Repeat steps S2 - S3 to obtain the damage state distribution between all the excitation sensor positions on the test rock mass and each group of receiving sensors.

[0099] Through this step, the damage state distribution between all the excitation sensors and each group of receiving sensors on the test rock mass under given deep - earth conditions can be obtained, and then the overall damage state distribution of the test rock mass can be determined. When there are intersection points in the lines connecting each excitation sensor and the receiving sensor, a tiny unit of the test rock mass is formed by these intersection points, and the maximum loss variable calculated at this position is used as the damage variable corresponding to this tiny unit.

[0100] S5 Change the deep - earth conditions and repeat steps S1 - S4 to obtain the evolution image of the rock mass damage state.

[0101] In this step, change the deep - earth conditions (including temperature field, stress field, seepage field or / and load), and repeat the above steps S1 - S4 to obtain the overall damage state distribution of the test rock mass under different deep - earth conditions. Then, based on the overall damage state distribution of the test rock mass under different deep - earth conditions, the evolution image of the test rock mass damage state can be obtained.

[0102] Figure 5 Provides a Figure 3 Schematic diagram of the real - time evolution of the damage variable α obtained under the arrangement of the excitation sensors and receiving sensors given (where P - wave receiving sensors and S - wave receiving sensors are installed alternately). It can be clearly seen from the figure how the damage states at different positions of the test rock mass change with the change of load. It can be intuitively seen from the figure that as the load increases, the change of the loss state at different positions inside the rock mass is different.

[0103] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A real-time imaging method for the evolution of the damage state of rock masses in deep geological environments, characterized in that, It includes the following steps: S1 Under given deep - earth conditions, an excitation signal is sent by an excitation sensor installed on the test rock mass, and then the signal is received by a receiving sensor installed on the test rock mass; The number of excitation sensors installed on the test rock mass is more than two, and the number of receiving sensors installed on the test rock mass is more than two. The types of the receiving sensors include longitudinal - wave sensors and transverse - wave sensors. Different - type receiving sensors are arranged staggeredly, and an adjacent longitudinal - wave receiving sensor and transverse - wave receiving sensor form a receiving - sensor group; S2 For any excitation sensor, obtain the longitudinal wave velocity V received by the longitudinal wave receiving sensors in each group of receiving sensors p , and the shear wave velocity V received by the shear wave receiving sensors S ; Longitudinal wave velocity V p Calculated according to the following formula: V p =L P / △t P where L P is the distance of the test rock mass through which the connection line from the excitation sensor to the longitudinal wave receiving sensor passes, and △t P is the time for the corresponding longitudinal wave received by the longitudinal wave receiving sensor to pass through the test rock mass; The said △t P can be calculated by the following formula: △t P =t 1P -t0 - t 2P where t 1P is the longitudinal wave reception time of the longitudinal wave sensor, t0 is the transmission time of the excitation sensor, and t 2P is the time consumed by the corresponding wave received by the longitudinal wave receiving sensor during propagation through the loading block or the non-rock mass interior. If the excitation sensor and the receiving sensor are arranged on the side of the test rock mass and in direct contact with the rock sample, then t 2P = 0; Transverse wave velocity V S Calculated according to the following formula: V S =L S / △t S Where, L S is the distance of the test rock mass through which the line connecting the excitation sensor and the shear wave receiving sensor passes, and △t S is the time for the corresponding shear wave received by the shear wave receiving sensor to pass through the test rock mass; The said △t S can be calculated by the following formula: △t S =t 1S -t0-t 2S where t 1S is the shear wave reception time of the shear wave sensor, t0 is the transmission time of the excitation sensor, and t 2S is the time consumed by the corresponding wave received by the shear wave receiving sensor during propagation through the loading block or the non-rock mass interior. If the excitation sensor and the receiving sensor are set on the side of the test rock mass and in direct contact with the rock sample, then t 2S = 0; S3 For each group of receiving sensors, according to the following damage - variable model, the corresponding damage variable of each group of receiving sensors is calculated based on the longitudinal - wave velocity and transverse - wave velocity: ； Wherein: is the damage variable; V P is the longitudinal wave propagation velocity; V S is the shear wave propagation velocity; ρ is the rock density; is the ratio of strain invariants, and the value range is: ; , , , are the first and second invariants of the elastic strain tensor, i = 1, 2, 3, j = 1, 2, 3; , , are constants related to the material; is the Lamé constant: ; = ; The damage - variable model is obtained by analyzing the damage variable expressed by double waves: （1） （2） （3） From the above formulas (1) and (2), we get: （4） In the formula, , the damage variable expression , , where = , represents the initial state of the material without fracture. Substituting it into the above formula (4), the above damage variable damage variable model can be obtained; And the damage variable is used as the damage - state distribution between the excitation sensor on the test rock mass and this group of receiving sensors; S4 Repeat steps S2 - S3 to obtain the damage - state distribution between all the positions of the excitation sensors on the test rock mass and each group of receiving sensors; S5 Change the deep - earth conditions, and repeat steps S1 - S4 to obtain the evolution image of the rock - mass damage state corresponding to different deep - earth states, and the real - time change image of the corresponding rock - mass mechanical damage state can be obtained according to the change process of the deep - earth state.

2. The real-time imaging method for the evolution of the rock mass damage state in the deep geological environment according to claim 1, wherein In step S1, the deep - earth conditions are the temperature field, stress field, seepage field, and load in which the test rock mass is located.

3. The real-time imaging method for the evolution of the rock mass damage state in the deep geological environment according to claim 1, wherein, In step S1, the installation methods of the excitation sensor and the receiving sensor include at least one of the following methods: (1) The excitation sensor is installed at one end of the load - loading end of the test rock mass in the deep - earth environment simulation chamber and is arranged in the loading cushion block set at one end of the test rock mass; the receiving sensor is installed at the opposite end of the load - loading end of the test rock mass; It is arranged in the loading cushion block set at the other end of the rock - mass sample; the number of excitation sensors and receiving sensors can be the same or different; (2) The excitation sensor and the receiving sensor are uniformly arranged along the axial direction of the test rock mass respectively; the number of excitation sensors and receiving sensors distributed along the axial direction of the test rock mass can be the same or different.

4. The real-time imaging method for the evolution of the rock mass damage state in the deep geological environment according to claim 3, characterized in that Each excitation sensor is uniformly arranged along the radial direction or / and circumferential direction of the loading cushion block; each receiving sensor is uniformly arranged along the radial direction or / and circumferential direction of the loading cushion block.

5. The real-time imaging method for the evolution of the rock mass damage state in a deep geological environment according to claim 1, characterized in that, In step S3, the obtained damage state is used to characterize the damage - state distribution between the corresponding excitation sensor on the test rock mass and this group of receiving sensors.

6. The real-time imaging method for the evolution of the rock mass damage state in a deep geological environment according to claim 1, characterized in that In step S5, change the temperature field, stress field, seepage field, or / and load in the deep - earth conditions, repeat the above steps S1 - S4 to obtain the overall damage - state distribution of the test rock mass under different deep - earth conditions, and then obtain the evolution image of the rock - mass damage state based on the overall damage - state distribution of the test rock mass under different deep - earth conditions.

7. The real-time imaging method for the evolution of the rock mass damage state in the deep geological environment according to any one of claims 1 to 6, characterized in that, When there are intersection points in the connection lines from each excitation sensor to each group of receiving sensors, a tiny unit of the test rock mass is formed by this intersection point, and the maximum damage variable calculated at this intersection point is used as the damage variable corresponding to this tiny unit.

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