A non-destructive testing and evaluation method and system for the heterogeneity degree of rock mechanics

Abstract

The present invention discloses a non-destructive testing and evaluation method and system for the heterogeneity degree of rock mechanics, belonging to the field of testing the heterogeneity characteristics of rock mechanics in deep underground engineering. The method includes: selecting a complete formation to be tested and drilling to obtain a core column; processing the core column to obtain rock specimens and marking numbers on the surfaces; respectively arranging ultrasonic longitudinal wave and transverse wave transducers on different numbered surfaces with marked numbers for single-sided testing and recording wave velocity data; obtaining a mechanical heterogeneity coefficient based on the recorded wave velocity data, and evaluating the mechanical heterogeneity degree of the rock through the mechanical heterogeneity coefficient. The technical solution of the present invention ensures that after testing, the rock specimens are not significantly damaged, can be repeatedly tested and used in other experiments, and the mechanical heterogeneity coefficient can significantly characterize the mechanical heterogeneity degree of the internal materials of the rock, with easy calculation, simple operation, good economy, strong practicability, promoting the evaluation and classification of the surrounding rock quality in deep underground engineering, and more effectively evaluating the risk of rock instability rupture and dynamic disasters.

Description

Technical Field

[0001] The present invention belongs to the field of testing the heterogeneity characteristics of rock mechanics in deep underground engineering, and particularly relates to a non-destructive testing and evaluation method for rock mechanics heterogeneity. Background Art

[0002] Although a rock structure body is an apparently complete block, it contains a considerable number of hidden cracks and micro-cracks that penetrate and bypass crystals. Most rocks are not composed of only one kind of mineral particle, and the relevant mechanical properties of various mineral particles that make up the block are also very different. These differences, including the spatial composition structure, result in the non-uniformity of the properties of rock materials, that is, the heterogeneity of rock materials. Heterogeneity is an important index for judging such inherent properties.

[0003] In the experimental research related to rock mechanical properties, this property interferes with the experimental results to a considerable extent. It affects the various strengths, stiffnesses, damage characteristics, and energy evolution of rock materials. In different engineering applications, different requirements for the heterogeneity of rocks are also required. Especially in extreme environments such as high stress in deep engineering, it is necessary to ensure that the rock material has high strength and can exhibit obvious cascading characteristics when it is damaged, so as to prevent and avoid dynamic disasters such as rock bursts and rock bumps in the surrounding rock.

[0004] Currently, the mainstream methods for evaluating rock heterogeneity include scanning electron microscopy, core observation method, X-CT tomography imaging method, etc. These methods characterize the heterogeneity by visually observing the microscopic composition of rocks, but do not deeply characterize the mechanical heterogeneity of rocks, and have strict requirements for material size and detection equipment, with high costs. In addition, there is also a method to evaluate the mechanical heterogeneity by analyzing the deformation, acoustic emission events, etc. of rock materials under loading, but this will cause obvious damage to the materials and there are certain risks in the operation. Repeated tests will consume more resources. As related projects develop deeper underground, the difficulty of drilling and coring is higher, and some special rock specimens are also more precious. Summary of the Invention

[0005] Aiming at the problem that the existing methods for evaluating rock heterogeneity cannot deeply characterize the mechanical heterogeneity of the internal materials of rocks, and cause great damage to rock materials and high costs, the present invention aims to provide a non-destructive testing and evaluation method and system for rock mechanics heterogeneity based on ultrasonic technology to solve the above problems existing in the prior art.

[0006] The above technical object of the present invention will be achieved by the following technical solutions.

[0007] According to the first aspect of the technical solution of the present invention, there is provided a non-destructive testing and evaluation method for rock mechanics heterogeneity, wherein the method includes the following steps:

[0008] S1. Select the intact formation to be measured, and drill for the intact formation to be measured to obtain a core column;

[0009] S2. Process the core column to obtain a rock specimen, and mark numbers on the surface;

[0010] S3. Arrange ultrasonic longitudinal wave and transverse wave transducers on different numbered surfaces marked on the rock specimen for single-sided testing, and record the wave velocity data received by the ultrasonic longitudinal wave and transverse wave transducers during the testing process;

[0011] S4. Obtain the mechanical heterogeneity coefficient based on the recorded wave velocity data, and evaluate the mechanical heterogeneity degree of the rock through the mechanical heterogeneity coefficient.

[0012] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. In step S1, vertical coring is performed on the formation to be measured to continuously obtain a core column.

[0013] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. The number of core columns is 3 to 10, and the length is 50 to 100 cm.

[0014] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. Step S2 is specifically: process all core columns to obtain the cube-shaped rock specimens, and mark numbers on each surface.

[0015] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. The side length of the cube-shaped rock specimen is 100 to 300 mm.

[0016] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. Step S3 is specifically:

[0017] S31. Arrange ultrasonic longitudinal wave transducers at the center positions of the opposite numbered surfaces marked on the rock specimen;

[0018] S32. Set the ultrasonic longitudinal wave transducers arranged on the opposite sides as the generator and the receiver respectively for ultrasonic testing. Subsequently, arrange the generator on all numbered surfaces except the numbered surface where the receiver is located for ultrasonic testing, and record the longitudinal wave velocity data received by the receiver as a single-sided test;

[0019] S33. Arrange the receiver on another numbered surface, and repeat the above single-sided test operation until single-sided testing is completed on each numbered surface and the longitudinal wave testing ends;

[0020] S34. Replace the ultrasonic longitudinal wave transducer with an ultrasonic shear wave transducer, repeat the single-sided test experiment, and record the shear wave velocity data received by the receiver until the shear wave test experiment ends.

[0021] In the above-described aspect and any possible implementation, a further implementation is provided. In step S31, an ultrasonic longitudinal wave transducer is respectively arranged at the center position of the numbered surface on the opposite side.

[0022] In the above-described aspect and any possible implementation, a further implementation is provided. Step S31 further includes: coupling the ultrasonic longitudinal wave transducer with the numbered surface, and fixing and closely attaching the ultrasonic longitudinal wave transducer to the numbered surface.

[0023] In the above-described aspect and any possible implementation, a further implementation is provided. The contact surface between the ultrasonic longitudinal wave transducer and the rock specimen is coupled by applying epoxy resin, and the transducer is fixed and closely attached to the surface of the rock specimen by using a compression spring support.

[0024] In the above-described aspect and any possible implementation, a further implementation is provided. In step S32, during the ultrasonic test, the generator releases ultrasonic waves once every 5 s, and the total release duration of the ultrasonic waves is set to 30 s.

[0025] In the above-described aspect and any possible implementation, a further implementation is provided. In step S34, aluminum foil is placed between the ultrasonic shear wave transducer and the numbered surface for coupling, and the ultrasonic shear wave transducer is fixed and closely attached to the surface of the rock specimen by using a compression spring support.

[0026] In the above-described aspect and any possible implementation, a further implementation is provided. Step S4 is specifically as follows:

[0027] S41. Calculate the initial mean value for the wave velocity data obtained during one ultrasonic test.

[0028] S42. Perform a secondary averaging calculation based on the initial mean value obtained in S41 to calculate the true mean values of the ultrasonic longitudinal wave and shear wave velocity data for each numbered surface of the rock specimen.

[0029] S43. Calculate the dynamic elastic modulus parameters for each numbered surface of the rock specimen based on the true mean values obtained in S42.

[0030] S44. Calculate the mechanical heterogeneity coefficient of the rock specimen based on the dynamic elastic modulus parameters obtained in S43.

[0031] S45. Evaluate the mechanical heterogeneity of the rock through the mechanical heterogeneity coefficient.

[0032] In the aspect and any possible implementation manner as described above, a further implementation manner is provided. The mechanical heterogeneity coefficient is the product of the ratio of the minimum value to the maximum value of the dynamic elastic modulus parameters of each numbered surface of the rock specimen and the percentage.

[0033] Here, the elastic modulus is an important index to measure the ability of a material to resist deformation in the elastic deformation stage. It represents the stress corresponding to the unit strain of the material under the action of stress. It can intuitively reflect the strength of the material's resistance to deformation. In addition, the elastic modulus is related to factors such as the internal structure, mineral composition, particle size, and arrangement mode of the material. These factors will all affect the mechanical properties of the material. Therefore, the elastic modulus can indirectly reflect the internal structure and composition of the material. In engineering applications, the elastic modulus can be used to evaluate the stability of rock engineering, and it can help predict the response of rocks under load. Through the elastic modulus, the deformation behavior of rocks under different load conditions can be evaluated, providing a basis for engineering design and being one of the important parameters.

[0034] Using the propagation principle of ultrasonic waves, the magnitude of the dynamic elastic modulus of the material can be calculated, reflecting the strength of the mechanical properties of the material, which can be used as a reference for the properties related to the mechanical response of the material. The mechanical heterogeneity degree refers to the non-uniformity of the mechanical properties inside the material in space. Specifically, it describes the differences and variations of the mechanical parameters (such as elastic modulus, strength, hardness, etc.) of the material at different positions or different scales.

[0035] The mechanical heterogeneity coefficient, which is the product of the ratio of the minimum value to the maximum value of the dynamic elastic modulus parameters of each numbered surface of the rock specimen and the percentage, can characterize the differences in the internal mechanical properties of the rock material to the greatest extent, quantitatively analyze its degree of uniformity, and the sorting of the maximum and minimum values can also indirectly analyze the anisotropy of the mechanical properties of the rock material. The comparison and analysis of the maximum and minimum values are also the most widely used and highly recognized data analysis methods in quantitative indicators. Among them, the smaller the value of the mechanical heterogeneity coefficient, the worse the evaluated mechanical heterogeneity degree of the rock specimen; the larger the value of the mechanical heterogeneity coefficient, the better the evaluated mechanical heterogeneity degree of the rock specimen.

[0036] In the aspects and any possible implementation manners described above, a further implementation manner is provided. When the mechanical heterogeneity coefficient is greater than or equal to 80%, the mechanical heterogeneity degree of the rock specimen is evaluated as good; when the mechanical heterogeneity coefficient is greater than or equal to 60% and less than 80%, the mechanical heterogeneity degree of the rock specimen is evaluated as medium; when the mechanical heterogeneity coefficient is less than 60%, the mechanical heterogeneity degree of the rock specimen is evaluated as poor, indirectly indicating that the mechanical heterogeneity degree of the rock stratum where the rock sample is located is poor.

[0037] According to a second aspect of the present invention, a non-destructive test and evaluation system for the mechanical heterogeneity degree of rocks is provided. The system includes: a processor and a memory for storing executable instructions; wherein, the processor is configured to execute the executable instructions to perform the non-destructive test and evaluation method for the mechanical heterogeneity degree of rocks as described in any of the above aspects.

[0038] According to a third aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the non-destructive test and evaluation method for the mechanical heterogeneity degree of rocks as described in any of the above aspects is implemented.

[0039] Advantageous technical effects of the present invention:

[0040] By using the present invention, the mechanical properties of different regions of rock materials can be quantitatively analyzed through ultrasonic testing of rocks and by using the ultrasonic propagation principle, and the mechanical heterogeneity degree of rocks can be evaluated. After the test, the rock specimen will not be significantly damaged, and can be repeatedly tested and used in other experiments. The mechanical heterogeneity coefficient defined in the present invention can significantly characterize the mechanical heterogeneity degree of the internal materials of the rock, is easy to calculate, simple to operate, has good economy and strong practicability, promotes the evaluation and classification of the surrounding rock quality of deep underground engineering, and more effectively evaluates the risk of rock instability, fracture and dynamic disasters. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, wherein:

[0042] Figure 1 It is a schematic diagram of the steps of the evaluation method in the embodiment of the present invention;

[0043] Figure 2 It is a schematic diagram of the arrangement of ultrasonic transducers on a rock specimen in the embodiment of the present invention;

[0044] Figure 3 It is a schematic diagram of the change of the dynamic elastic modulus parameters of different numbered surfaces of three rock specimens in the embodiment of the present invention.

[0045] Among them, the reference numerals are explained as follows:

[0046] 1 Rock specimen; 2 Ultrasonic transducer; 3 Indenter that can slide along the anti-skid rod; 4 Anti-skid rod; 5 Compression spring support. Detailed implementation mode

[0047] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments, but the implementation modes of the present invention are not limited thereto.

[0048] Based on the elastic wave propagation principle that when ultrasonic waves penetrate a cube-shaped rock specimen under non-destructive conditions, the velocity attenuation will occur due to the structural differences such as internal pores, and indirectly reflect the mechanical property differences inside the rock, the evaluation method of the present invention is proposed.

[0049] The technical solution of the present invention first provides a non-destructive test and evaluation method for the rock mechanics heterogeneity based on ultrasonic technology, as Figure 1 shown, the method includes the following steps:

[0050] S101. Select the intact formation to be measured, and drill for the intact formation to be measured to obtain a core column.

[0051] In a preferred embodiment, step S1 is specifically to vertically drill and take cores for the formation to be measured, and continuously take 3 to 10 core columns with a length of 50 to 100 cm.

[0052] S102. Process the core column to obtain a rock specimen, and mark the numbers on the surface.

[0053] In a preferred embodiment, step S2 is specifically to process all core columns to obtain the cube-shaped rock specimens with side lengths of 100 to 300 mm, and mark the numbers on each surface.

[0054] S103. Respectively arrange ultrasonic longitudinal wave and transverse wave transducers on the numbered surfaces of the rock specimen for single-sided test experiments, and record the data received by the ultrasonic transducers during the test.

[0055] In a preferred embodiment, step S3 is specifically:

[0056] S31. Respectively arrange 1 longitudinal wave transducer at the center position of the opposite side surface of the specimen in the test area for the generation and reception of longitudinal waves during the ultrasonic test.

[0057] In a preferred embodiment, step S31 further includes: applying epoxy resin at the contact surface between the longitudinal wave transducer and the rock specimen for coupling, and using a compression spring support to fix the transducer and closely attach it to the surface of the rock specimen.

[0058] S32. Set the ultrasonic longitudinal wave transducer on a certain numbered surface as the ultrasonic generator, and set the ultrasonic longitudinal wave transducer on the other numbered surface as the receiver to conduct an ultrasonic test once. The generator releases ultrasonic waves every 5 s, and the total release duration of the ultrasonic waves is set to 30 s. After the receiver has collected all the ultrasonic signals, that is, when the waveform displayed on the oscilloscope no longer changes, record the wave velocity data received by the ultrasonic transducer during this process. Subsequently, remove the generator and arrange it on other specimen numbered surfaces through the same operation, and repeat the above operation until ultrasonic generators have been arranged for testing on all specimen numbered surfaces except the numbered surface where the receiver is located, which is regarded as a single-sided test.

[0059] S33. After a single-sided test is completed, arrange the receiver on other numbered surfaces of the specimen, and repeat the above single-sided test operation until ultrasonic single-sided tests have been completed on all numbered surfaces of the specimen. Record the longitudinal wave velocity data received by the ultrasonic receiver during the operation process, and the ultrasonic longitudinal wave test experiment ends.

[0060] S34. After the longitudinal wave test experiment ends, replace the ultrasonic longitudinal wave transducer used in the above test process with a transverse wave transducer. Place aluminum foil at the contact surface between the transverse wave transducer and the rock specimen for coupling, and the rest of the operations are the same as those in the above longitudinal wave test experiment. Repeat the single-sided test experiment, record the transverse wave velocity data received by the ultrasonic receiver during the operation process, and the ultrasonic transverse wave test experiment ends.

[0061] S104. According to the recorded data, statistically analyze the true mean values of the transverse wave and longitudinal wave velocities, the dynamic elastic modulus, and the mechanical heterogeneity coefficient of each numbered surface, and evaluate the mechanical heterogeneity degree of the rock by the mechanical heterogeneity coefficient.

[0062] In a preferred embodiment, the step S4 specifically includes:

[0063] S41. Conduct an ultrasonic test experiment on the rock specimen, and calculate the initial mean values of the ultrasonic longitudinal wave and transverse wave velocity data received by the receiver in each ultrasonic test.

[0064] S42. Conduct a secondary averaging calculation based on the initial mean values obtained in S41, and calculate the true mean values of the ultrasonic longitudinal wave and transverse wave velocities obtained by the transducer in the single-sided test of a single numbered surface.

[0065] S43. Calculate the dynamic elastic modulus parameters of each numbered surface of the rock specimen according to the true mean values of the longitudinal wave and transverse wave velocities obtained in S42.

[0066] S44. Calculate the mechanical heterogeneity coefficient of the rock specimen according to the dynamic elastic modulus parameters obtained in S43.

[0067] In a preferred embodiment, the mechanical heterogeneity coefficient is the product of the ratio of the minimum value to the maximum value of the dynamic elastic modulus parameters of each numbered surface of the rock specimen and the percentage.

[0068] Here, the smaller the value of the mechanical heterogeneity coefficient, the worse the mechanical heterogeneity degree of the rock specimen is evaluated; the larger the value of the mechanical heterogeneity coefficient, the better the mechanical heterogeneity degree of the rock specimen is indicated.

[0069] In a preferred embodiment, when the mechanical heterogeneity coefficient is greater than or equal to 80%, the mechanical heterogeneity degree of the rock specimen is evaluated as good; when the mechanical heterogeneity coefficient is greater than or equal to 60% and less than 80%, the mechanical heterogeneity degree of the rock specimen is evaluated as medium; when the mechanical heterogeneity coefficient is less than 60%, the mechanical heterogeneity degree of the rock specimen is evaluated as poor.

[0070] The technical solution of the present invention also provides a non-destructive testing and evaluation system for the mechanical heterogeneity degree of rocks. The system includes: a processor and a memory for storing executable instructions; wherein, the processor is configured to execute the executable instructions to perform the non-destructive testing and evaluation method for the mechanical heterogeneity degree of rocks as described above.

[0071] The technical solution of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the non-destructive testing and evaluation method for the mechanical heterogeneity degree of rocks as described above.

[0072] Embodiment

[0073] To better illustrate the present invention, taking granite as the experimental object, the change trend of mechanical properties reflected by the difference in ultrasonic propagation velocity in different directions inside the rock specimen under three different metamorphic degrees was studied.

[0074] The non-destructive testing and evaluation method for the mechanical heterogeneity degree of rocks based on ultrasonic technology includes the following steps:

[0075] S1. Select the intact formation to be measured;

[0076] S2. Drill the intact formation to be measured to obtain a core column;

[0077] S3. Process the core column to obtain a rock specimen, and mark numbers on the surface;

[0078] S4. Respectively arrange ultrasonic longitudinal wave and transverse wave transducers on the numbered surfaces of the rock specimen for single-sided testing experiments, and record the data received by the ultrasonic transducers during the testing process.

[0079] S5. Statistically analyze the true average shear wave velocity, longitudinal wave velocity, dynamic elastic modulus, and mechanical heterogeneity coefficient of each numbered surface based on the recorded data, and evaluate the mechanical heterogeneity degree of the rock according to the mechanical heterogeneity coefficient.

[0080] Specifically, the evaluation method of the rock heterogeneity degree is the wave velocity dispersion coefficient method for ultrasonic waves penetrating the rock in different directions, including the following steps:

[0081] Preparation of rock specimens

[0082] (1) Formation selection: Select the intact formation to be measured in the deep part as the area for drilling and sampling.

[0083] (2) Core drilling: Vertically drill and take cores from the intact formation to be evaluated for mechanical heterogeneity. Continuously take 3 to 10 core columns with a length of 50 to 100 cm. Preferably, in this embodiment, 5 core columns with a length of 60 to 80 cm are continuously taken. For the same formation, the sampling distance between each core column should not exceed 50 cm. The formation with the above core columns is an intact formation, rather than a fractured zone formation. The sampling interval not exceeding 50 cm is to ensure that the sampled core columns come from the same formation.

[0084] (3) Preparation of rock specimens: Process the core columns obtained in step (2) to uniformly process the rock specimens in the shape of a cube with a side length of 100 to 300 mm according to the rock mechanics test standard. In the present invention, it is preferred to process the rock specimens in the shape of a cube with a side length of 200 mm.

[0085] (4) According to the penetration characteristics of the rock specimens under ultrasonic testing experiments, number and mark each surface of the rock specimens obtained in step (3). Arrange two ultrasonic transducers, which are respectively set as a generator and a receiver, on different numbered surfaces. Replace the types of transducers, the placement directions of the specimens, and the placement positions of the transducers, and conduct ultrasonic testing. Ultrasonic waves in different directions will have wave velocity changes when penetrating the rock specimens due to the differences in the internal structures of the rocks, so as to calculate the initial average value and true average value of the ultrasonic wave velocities from different directions during the testing process of the transducers on different numbered surfaces, further calculate the dynamic elastic modulus of different numbered surfaces of the rock specimens and the mechanical heterogeneity coefficient of the rock specimens, and further evaluate the mechanical heterogeneity degree of the rock according to the mechanical heterogeneity coefficient of the rock.

[0086] (5) The present invention uses 3 cube-shaped rock specimens, such as Figure 2As shown in the figure, the upper and lower ends of each rock specimen 1 are connected to the indenter 3 that can slide along the anti-side-slip rod, which is used to prevent the position of the rock specimen from moving during the test. Two ultrasonic transducers 2 are arranged on both sides of the rock specimen 1 by using epoxy resin or aluminum foil. Each transducer is fixed by two compression clamping springs 5. The anti-side-slip rod 4 is connected to both the indenter 3 that can slide along the anti-side-slip rod and the compression clamping springs 5, ensuring the stability of the rock specimen 1 and the ultrasonic transducers 2 during the test and preventing the position from moving. The ultrasonic generator is controlled by a computer to output ultrasonic waves, and the ultrasonic signal characteristics of the ultrasonic receiver are recorded and processed to obtain wave velocity data.

[0087] Data processing of ultrasonic transducers

[0088] (1) Under non-destructive conditions, when ultrasonic waves penetrate the rock from different directions, the wave velocity will change due to the influence of the internal structure differences. Moreover, the greater the internal differences, the greater the difference in ultrasonic wave velocities in different directions. According to the elastic wave propagation theory, the dynamic elastic modulus parameters and mechanical heterogeneity coefficients of the rock can be calculated. When the rock is not affected by other factors, the mechanical heterogeneity coefficient calculated from the wave velocity differences of ultrasonic waves penetrating the rock in different directions can reflect the mechanical heterogeneity degree of the rock's mechanical characteristics.

[0089] (2) Ultrasonic tests with the same test steps are carried out on all three rock specimens. Each transducer receives several ultrasonic signals during the test. When conducting the first ultrasonic longitudinal wave test, the longitudinal wave transducer set as the ultrasonic generator will release ultrasonic waves every 5 s under computer control, and the overall duration is not less than 15 s. In the present invention, it is set to 30 s, that is, 6 times of ultrasonic waves are released. The longitudinal wave transducer set as the ultrasonic receiver will receive the ultrasonic wave signals released at these 6 different times. After computer processing, the wave velocities of these 6 different ultrasonic longitudinal waves will be obtained. At this time, the first ultrasonic longitudinal wave test ends. The generator is removed and arranged on another numbered surface according to the same operation to conduct the second ultrasonic longitudinal wave test. The test steps are the same until the ultrasonic longitudinal wave tests are completed on all the specimen numbered surfaces except the one where the receiver is located. At this time, the first single-sided test ends. The receiver is removed and arranged on another numbered surface according to the same operation to conduct the second single-sided test. The test steps are the same. Finally, the receiver will receive several groups of ultrasonic longitudinal wave data on each specimen numbered surface. At this time, the ultrasonic longitudinal wave test ends. The longitudinal wave transducer is replaced with a transverse wave transducer, and the above operations are repeated. Finally, the receiver will receive several groups of ultrasonic transverse wave data on each specimen numbered surface.

[0090] (3) Process the wave velocity data obtained when the receiver is arranged on the surface of the specimen numbered 1. Let the longitudinal wave velocity received by the receiver arranged on the surface of the specimen numbered 1 during the first ultrasonic test be v 1, v 2 , v 3 , …, v m , the initial average value V of the longitudinal wave velocity received by the receiver from the direction of the generator can be obtained a = Σv m / m. During a single-sided test process, the transducer will receive the initial average values of longitudinal waves from five different directions of the generator on the surface of the specimen numbered 1, which are V a , V b , V c , V d , V e . Then, the true average value V of the longitudinal wave of the receiver arranged on the numbered surface of 1 specimen can be obtained p1 = (V a + V b + V c + V d + V e ) / 5. Similarly, the true average values V of the longitudinal wave velocities received by the receiver arranged on the numbered surfaces of n specimens can be obtained p1 , V p2 , V p3 , …, V pn . Similarly, the true average values V of the shear wave velocities received by the receiver arranged on the numbered surfaces of n specimens can be obtained s1 , V s2 , V s3 , …, V sn .

[0091] Quantitative Characterization of Rock Heterogeneity

[0092] Furthermore, the mechanical heterogeneity of the internal structure of the rock under non-destructive conditions leads to the differential change in the wave velocity of the rock specimen during ultrasonic testing. According to the calculation formula of acoustic-related theory, the mechanical parameters such as the dynamic elastic modulus of the rock specimen can be obtained. In order to quantitatively reflect the mechanical parameter differences in different regions inside the rock specimen shown by the wave velocity changes when ultrasonic waves penetrate the rock specimen in different directions due to rock heterogeneity, a mechanical heterogeneity coefficient determined by the dynamic elastic modulus parameters of different regions of the rock specimen is defined; with the help of ultrasonic testing experiments, the heterogeneity parameters of the rock specimen are calculated using the longitudinal and shear wave velocity data in different directions to reflect the mechanical differences in the internal structure of the rock;

[0093] Furthermore, the calculation formula for the dynamic elastic modulus of the rock specimen adopted in the present invention is as follows:

[0094]

[0095] Among them, E d is the dynamic elastic modulus (GPa); ρ is the density of the rock specimen (kg / m 3 ); Vp and V s are the true average longitudinal and shear wave velocities (m / s), respectively;

[0096] Furthermore, by using the true average longitudinal and shear wave velocities obtained by the receivers arranged on the n specimen number surfaces, the dynamic elastic modulus E of the regions where the n specimen number surfaces are located can be calculated using the above formula d1 and E d2 and E d3 , …, E dn , and sorting them to obtain the maximum dynamic elastic modulus E max and the minimum value E min ;

[0097] Furthermore, the mechanical heterogeneity coefficient K E of the rock specimen defined in the present invention is calculated as follows:

[0098]

[0099] This expression indicates that the larger the value of the mechanical heterogeneity coefficient K E , the smaller the difference in mechanical parameters of each region of the rock specimen, indirectly indicating better mechanical homogeneity of the rock specimen; while the smaller the value of the mechanical heterogeneity coefficient K E , the greater the difference in mechanical parameters of each region of the rock specimen, then the mechanical heterogeneity of the rock specimen is worse, thus indicating that the mechanical heterogeneity of the rock formation where the rock specimen is located is also worse.

[0100] For example Figure 3 The mechanical heterogeneity degrees of the three rock specimens shown are all different. Rock specimens with the mechanical heterogeneity coefficient K E greater than or equal to 80% are classified as rock specimens with better mechanical heterogeneity, and those with the mechanical heterogeneity coefficient K E less than 80% and greater than or equal to 60% are classified as rock specimens with general mechanical heterogeneity, and those with the mechanical heterogeneity coefficient K E less than 60% are classified as rock specimens with poor mechanical heterogeneity, as shown in Figure 3 .

[0101] Specifically, the method of the present invention is applied to granite experimental objects in deep shaft construction areas, including the following steps:

[0102] A1: Investigate in detail the geological structure of the formation where the granite is located, select the evaluation area, and ensure that the core has good representativeness;

[0103] A2: Investigate in detail the lithology, engineering properties, and weathering degree of the granite, and evaluate the quality grade of the surrounding rock;

[0104] A3: Vertically drill and core the formation to be evaluated for homogeneity, continuously take 5 core columns with a length of 60 - 80 cm. For the same formation, the sampling distance between core columns should not exceed 50 cm;

[0105] A4: Process the core columns obtained in the above steps into cubic rock specimens with a side length of 200 mm, thus obtaining multiple cubic rock specimens;

[0106] A5: Number and mark each surface of the cubic rock specimens obtained in the above steps, divide them into six regions, and arrange a total of 2 ultrasonic transducers on the opposite numbered surfaces of the cubic specimens. Each transducer is arranged at the center position of the numbered surface for the generation and reception of ultrasonic waves during the test;

[0107] A7: During the test of the rock specimens, use an anti - side - slip rod and an anti - tipping device to stabilize the rock specimens. Use a compression spring support to fix the ultrasonic transducers on the specimen numbered surface, and apply epoxy resin or place aluminum foil on the contact surface between the transducer and the specimen to prevent the rock specimens and transducers from becoming unstable or having poor coupling, which may affect the experimental results;

[0108] A8: Calculate the true average values of longitudinal wave and transverse wave velocities, dynamic elastic modulus, and mechanical inhomogeneity coefficient based on the data obtained from the above ultrasonic test experiment. According to the mechanical inhomogeneity coefficient, divide the rock specimens into three cases: good homogeneity, medium homogeneity, and poor homogeneity. Rock specimens with a mechanical inhomogeneity coefficient greater than or equal to 80% are classified as rock specimens with good homogeneity;

[0109] Among them, those with a mechanical inhomogeneity coefficient less than 80% and greater than or equal to 60% are classified as rock specimens with medium homogeneity, and those with a mechanical inhomogeneity coefficient less than 60% are classified as rock specimens with poor homogeneity.

[0110] In summary, the technical solution of the present invention is used to evaluate the mechanical heterogeneity of rocks. First, the formation to be measured is selected; second, a core column is obtained by drilling the formation to be measured; third, the core column is processed to obtain a rock specimen; fourth, each surface of the rock specimen is numbered and marked; fifth, two ultrasonic transducers are respectively arranged on the opposite numbered surfaces of the rock specimen, ultrasonic tests are carried out, and the types of the generator and the receiver and their arranged positions are changed for multiple tests, and the data received by the transducers on each numbered surface are recorded; finally, the true average values of the longitudinal wave and transverse wave velocities, the dynamic elastic modulus and the mechanical heterogeneity coefficient are calculated according to the recorded data, and the mechanical heterogeneity of the rock is evaluated by the mechanical heterogeneity coefficient. Under the ultrasonic test conditions of the same longitudinal wave and transverse wave frequencies, the dynamic elastic modulus and the mechanical heterogeneity coefficient of the rock are calculated according to the true average values of the longitudinal and transverse wave velocities in different directions to obtain the mechanical heterogeneity characteristics of the rock; the rock specimen can be reused, the calculation is easy, the operation is simple, the economy is good, the practicability is strong, it is helpful to quantitatively evaluate the mechanical heterogeneity inside the rock material, promote the evaluation and classification of the surrounding rock quality of deep underground engineering, and more effectively evaluate the risk of rock dynamic disasters.

[0111] The foregoing description has shown and described several preferred embodiments of the present invention. However, as previously mentioned, it should be understood that the present invention is not limited to the forms disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the application concept described herein through the above teachings or the technology or knowledge in related fields. And the changes and modifications made by those skilled in the art do not depart from the spirit and scope of the present invention.

Claims

1. A nondestructive testing and evaluation method for rock mechanics heterogeneity, characterized in that: The method comprises the following steps: S1: selecting a complete stratum to be tested, and drilling the complete stratum to be tested to obtain a core column; S2: processing the core column to obtain a rock sample, and marking the surface with numbers; S3 arranges ultrasonic longitudinal wave and shear wave transducers on different numbered surfaces of the rock sample for single-side testing, and records the wave velocity data received by the ultrasonic longitudinal wave and shear wave transducers during the test; wherein the upper and lower ends of each rock sample are connected to a pressure head that can slide along the anti-skid rod, and the ultrasonic longitudinal wave and shear wave transducers are arranged on both sides of the rock sample by using epoxy resin or aluminum foil, and each transducer is fixed by two compressed clamping springs, and the anti-skid rod is connected to the pressure head that can slide along the anti-skid rod and the compressed clamping spring; Wherein, the step S3 is specifically as follows: S31 arranging ultrasonic longitudinal wave transducers at the center of the numbered surface on the opposite side where the rock sample is numbered; S32: setting the ultrasonic longitudinal wave transducer arranged on the opposite side as a generator and a receiver respectively to perform ultrasonic testing, and then arranging the generator on all numbered surfaces except the numbered surface where the receiver is located to perform ultrasonic testing respectively, and recording the longitudinal wave velocity data received by the receiver as a single-surface test; S33: arranging the receiver to another numbered surface, repeating the above single-surface test operation, until all numbered surfaces have completed the single-surface test, and the longitudinal wave test is finished; S34: replacing the ultrasonic longitudinal wave transducer with an ultrasonic shear wave transducer, repeating the single-side test experiment, and recording the shear wave velocity data received by the receiver until the shear wave test experiment is completed; S4: obtaining a mechanical heterogeneity coefficient according to the recorded wave velocity data, and evaluating the mechanical heterogeneity of the rock by using the mechanical heterogeneity coefficient; Wherein, the step S4 is specifically as follows: S41 performs initial mean value calculation on the wave velocity data obtained during the ultrasonic test; S42 performs secondary averaging calculation based on the initial average value obtained in S41 to calculate the true average value of the ultrasonic longitudinal wave and shear wave velocity data of each numbered surface of the rock sample; S43 calculates the dynamic elastic modulus parameters of each numbered surface of the rock sample according to the true mean value obtained in S42; S44 calculates the mechanical heterogeneity coefficient of the rock sample according to the dynamic elastic modulus parameter obtained in S43; wherein the mechanical heterogeneity coefficient is the product of the ratio of the minimum value to the maximum value of the dynamic elastic modulus parameter of each numbered surface of the rock sample and the percentage; S45 evaluates the mechanical heterogeneity of the rock through the mechanical heterogeneity coefficient; wherein, when the mechanical heterogeneity coefficient is greater than or equal to 80%, the mechanical heterogeneity of the rock sample is evaluated as good; when the mechanical heterogeneity coefficient is greater than or equal to 60% and less than 80%, the mechanical heterogeneity of the rock sample is evaluated as medium; when the mechanical heterogeneity coefficient is less than 60%, the mechanical heterogeneity of the rock sample is evaluated as poor, which indirectly indicates that the mechanical heterogeneity of the rock stratum where the rock sample is located is poor.

2. The method according to claim 1, characterized in that In the step S1, vertical coring is performed on the complete formation to be tested to continuously obtain core columns.

3. The method according to claim 1, characterized in that The step S2 specifically includes: processing all the core columns to obtain the cube-shaped rock samples, and marking each surface with a number.

4. The method according to claim 1, characterized in that: In step S32, during the ultrasonic test, the generator releases ultrasonic waves every 5 seconds, and the total release time of the ultrasonic waves is set to 30 seconds.

5. A nondestructive testing and evaluation system for rock mechanics heterogeneity, the system comprising: A processor and a memory for storing executable instructions; characterized in that the processor is configured to execute the executable instructions to perform the rock mechanics heterogeneity non-destructive testing and evaluation method as described in any one of claims 1 to 4.

6. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed by a processor, the non-destructive testing and evaluation method for rock mechanics heterogeneity as described in any one of claims 1 to 4 is implemented.

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