Rock mass elastic modulus and poisson's ratio co-measuring method and probe monitoring device

Abstract

The application provides a rock mass elastic modulus and Poisson's ratio co-measuring method and a probe monitoring device, and belongs to the technical field of engineering geology. The method comprises the following steps: performing probe penetration testing on a rock sample to be tested; obtaining an approximate Poisson's ratio of the rock sample according to experience estimation; obtaining an approximate elastic modulus of the rock sample to be tested by substituting the approximate Poisson's ratio into an Oliver-Pharr method; measuring key mark points in a probe penetration area by using a laser range finder, and recording experimental penetration depths of the key mark points; substituting the approximate elastic modulus and the approximate Poisson's ratio of the rock sample to be tested into a numerical model of the probe and the rock sample to be tested; optimizing the approximate elastic modulus and the approximate Poisson's ratio of the rock sample to be tested by using a simulated annealing particle swarm algorithm, and outputting an optimized Poisson's ratio and an optimized elastic modulus. The device can co-measure the elastic modulus and the Poisson's ratio of an engineering rock mass at a very low cost, and the testing process is basically not limited by the size and shape of the rock sample to be tested.

Description

Technical Field

[0001] This invention belongs to the field of engineering geology technology, specifically relating to a method for measuring the elastic modulus and Poisson's ratio of rock mass and a probe monitoring device. Background Technology

[0002] Rock, as a typical engineering material, is a core component of rock masses in deep engineering. Accurate measurement of its elastic mechanical parameters is crucial for tunnel excavation, The design, construction, operation, and maintenance of major national underground projects such as underground storage, deep mineral resource mining, and deep geothermal development are of paramount importance.

[0003] Currently, the main methods for obtaining elastic mechanical parameters of deep hard rock include laboratory testing and field monitoring. In laboratory testing, researchers typically obtain elastic modulus and Poisson's ratio through uniaxial compression tests using borehole cores, processed core samples into standard specimens, and then subjected to strain gauge bonding or prefabricated speckle fields. However, laboratory testing has significant limitations: firstly, the core sampling process for deep rock masses is complex and costly; secondly, for rock masses rich in joints and fractures, core quality is difficult to guarantee, making it difficult to prepare standard test samples; and thirdly, the testing cycle is long and the cost is high. Even if the test is successfully completed, the macroscopic mechanical parameters obtained cannot truly reflect the in-situ characteristics of the rock mass due to the influence of complex internal rock structures and fractures; furthermore, laboratory testing suffers from significant data dispersion, with some test results lacking representativeness. Field monitoring methods such as microseismic monitoring, limited by engineering costs, site conditions, and time constraints, also yield very limited data on rock mechanical parameters. In recent years, with the upgrading of instruments and equipment, probe indentation equipment has shown certain advantages. It can obtain the hardness and elastic modulus of materials with only a small number of representative samples under the condition of limited samples. However, its limitation is that it cannot obtain Poisson's ratio by means of this test alone. Researchers need to use empirical estimation methods to obtain the value of Poisson's ratio and then obtain an approximate elastic modulus, which causes a certain degree of measurement error. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application proposes a method and probe monitoring device for the joint measurement of rock mass elastic modulus and Poisson's ratio. This method can measure the elastic modulus and Poisson's ratio of rock samples simultaneously, overcoming the limitations of rock sample shape and size in traditional indoor rock mechanics experiments. It can not only obtain the elastic modulus of the rock sample, but also, by combining probe indentation testing, laser ranging technology, and numerical simulation methods, can invert and obtain the Poisson's ratio of the rock sample.

[0005] In a first aspect, the present invention provides a method for simultaneously measuring the elastic modulus and Poisson's ratio of rock mass, comprising:

[0006] A probe monitoring device was used to perform probe indentation tests on the rock samples to be tested;

[0007] The load-displacement curve of the pressure head in the probe monitoring device was collected;

[0008] The approximate Poisson's ratio of the rock sample was obtained based on empirical estimation methods;

[0009] Based on the load-displacement curve, the approximate elastic modulus of the rock sample to be tested is obtained by substituting the approximate Poisson's ratio into the Oliver-Pharr method.

[0010] A laser rangefinder was used to measure the key marker points in the probe indentation area, and the experimental indentation depth of the key marker points was recorded.

[0011] Numerical models of the probe and the rock sample to be tested are established in finite element software. The approximate elastic modulus and approximate Poisson's ratio of the rock sample to be tested are substituted into the numerical models of the probe and the rock sample to be tested to obtain the simulated indentation depth of the key marker points.

[0012] Based on the multi-objective error function, the approximate elastic modulus and approximate Poisson's ratio of the rock sample to be tested are optimized using the simulated annealing particle swarm algorithm, and the optimized Poisson's ratio and optimized elastic modulus are output. The multi-objective error function is established based on the difference between the experimental indentation depth and the simulated indentation depth of the key marker points.

[0013] The method employs a probe monitoring device to perform probe indentation testing on the rock sample to be tested, including:

[0014] The rock sample to be tested is processed and then fixed in the probe monitoring device;

[0015] A probe monitoring device was used to perform probe indentation tests on the fixed rock samples.

[0016] The processing of the rock sample to be tested includes:

[0017] The rock sample is cut, ground, and polished to form the rock sample to be tested. The height of the rock sample to be tested is <10mm.

[0018] The multi-objective error function is calculated as follows:

[0019] ;

[0020] in, For multi-objective error functions, The number of key markers, For the i-th key marker, Key markers The experimental indentation depth, Key markers The simulated indentation depth.

[0021] The load-displacement curve of the pressure head in the acquisition probe monitoring device includes:

[0022] When using a probe monitoring device to perform a probe indentation test on the rock sample to be tested, the probe randomly selects a region on the loading surface of the rock sample as the indentation region and collects the load-displacement curve of the indenter during indentation.

[0023] The step of measuring the key marker points in the indentation area using a laser rangefinder and recording the experimental indentation depth of the key marker points includes: after the probe indentation test is completed, using a laser rangefinder to measure the indentation depth of the probe at the key marker points in the indentation area, and the measured depth by the laser rangefinder is the experimental indentation depth of the key marker points.

[0024] In a second aspect, the present invention also provides a probe monitoring device, comprising: a power supply module, a power output module, a data acquisition and storage module, and a laser rangefinder;

[0025] The power supply module is connected to the data acquisition and storage module, the power output module and the laser rangefinder respectively, and is used to provide power to the probe monitoring device.

[0026] The power output module, connected to the data acquisition and storage module, includes a servo controller, a stepper motor, a ball screw, a load cell, and a probe. The servo controller is connected to the stepper motor, the stepper motor is connected to the ball screw, the ball screw is connected to the load cell, and the load cell is connected to the probe. The servo controller is equipped with a loading rate regulator to control the probe to be pressed into the rock sample to be tested at a fixed loading rate.

[0027] The acquisition and storage module is connected to the power output module and is used to store the load-displacement curve of the probe's indentation in real time.

[0028] The laser rangefinder is used to measure the key marker points in the indentation area and record the experimental indentation depth of the key marker points.

[0029] The indenter of the probe is a diamond Glass indenter.

[0030] The probe is a micrometer-scale probe.

[0031] Beneficial effects:

[0032] This application proposes a method and probe monitoring device for simultaneously measuring the elastic modulus and Poisson's ratio of rock mass. This method enables in-situ testing of the physical properties of engineering rock masses at extremely low cost. Even in engineering sites with relatively fractured rock masses, testing can be conducted with a small number of rock samples, and the testing process is largely unaffected by the size and shape of the rock samples. Only a few probe indentations are needed to obtain the elastic parameters of the rock samples, and the strength parameters can be obtained by introducing laser ranging, numerical simulation, and inversion methods. The most crucial difference between this probe and other probe indentation devices is that this device integrates a laser rangefinder, enabling high-precision measurement of the indented area. After the probe is pressed into the rock sample, it will leave an indentation area on the surface of the sample, which will be a conical pit. After the test is completed, a laser rangefinder is used to scan this indentation area to determine the coordinates of the marker point and the indentation depth at that point. Then, a finite element model and a probe model are established, and a multi-objective error function for the experimental indentation depth and the simulated indentation depth is constructed. The estimated assumed Poisson's ratio and assumed elastic modulus are input, and the true Poisson's ratio and true elastic modulus of the rock sample are obtained through inversion. Attached Figure Description

[0033] Figure 1 This is a flowchart of a method for jointly measuring the elastic modulus and Poisson's ratio of rock mass according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of a method for jointly measuring the elastic modulus and Poisson's ratio of rock mass according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of a probe monitoring device according to an embodiment of the present invention;

[0036] Figure 4 This is a magnified view of a portion of the structure near the probe in an embodiment of the present invention;

[0037] Figure 5 This is a diagram of specific marker points in the probe insertion area of ​​the laser rangefinder according to an embodiment of the present invention;

[0038] Figure 6 This is a load-displacement curve of the indenter during probe testing according to an embodiment of the present invention;

[0039] The components are: 1-Switch button, 2-Handle, 3-Power supply module, 4-Data acquisition and storage module, 5-Servo controller, 6-Loading rate regulator, 7-Stepper motor, 8-Pressure plate, 9-Pressure column, 10-Ball screw, 11-Weighing sensor, 12-Laser rangefinder, 13-Probe, 14-Rock sample placement platform, 15-Rigid base plate. Detailed Implementation

[0040] The specific implementation methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0041] Accurate measurement of rock elastic parameters is fundamental to the safe and efficient development of deep rock engineering. Current main methods for obtaining deep rock mechanical parameters fall into two categories: laboratory testing and field monitoring. For laboratory testing, researchers need to conduct core sampling in the field, then process these cores into standardized test samples for a series of mechanical property tests in the laboratory, such as uniaxial compression testing, conventional triaxial testing, and true triaxial testing. However, this method faces multiple challenges. First, core sampling of deep rock masses is extremely complex and costly, increasing the difficulty and expense of the experiments. Second, for rock masses rich in joints and fractures, the quality of core samples is often difficult to guarantee, making it difficult to prepare samples that meet testing standards. Even if laboratory tests are successfully conducted, the complex and variable structural surfaces and fractures within the rock mean that the obtained macroscopic mechanical parameters often cannot fully reflect the true characteristics of the rock mass. Furthermore, the significant dispersion of laboratory experimental data makes many experimental results lack sufficient representativeness. With the continuous upgrading of instruments and equipment, probe indentation devices have shown certain advantages. They can obtain the hardness and elastic parameters of materials with only a small number of representative samples, even under conditions of limited sample availability. However, their limitation lies in the fact that they cannot obtain the Poisson's ratio of the tested material solely through this test. Usually, the Poisson's ratio needs to be estimated to obtain the elastic modulus of the tested material, which leads to a certain degree of error in the measurement results. Similarly, field monitoring methods such as microseismic monitoring are limited by engineering costs, site conditions, and time constraints, resulting in very limited data on rock mechanics parameters that can be obtained.

[0042] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0043] Example 1:

[0044] This embodiment proposes a method for simultaneously measuring the elastic modulus and Poisson's ratio of rock mass, such as... Figure 1 , Figure 2 As shown, it includes:

[0045] Step S1: Using a probe monitoring device, perform a probe indentation test on the rock sample to be tested, including:

[0046] Step S1.1: Process the rock sample to be tested and fix the processed rock sample in the probe monitoring device;

[0047] In this embodiment, the rock sample is cut, ground, and polished to form the rock sample to be tested. The height of the rock sample to be tested is <10mm.

[0048] Step S1.2: Use a probe monitoring device to perform a probe indentation test on the fixed rock sample.

[0049] Step S2: Collect the load-displacement curve of the pressure head in the probe monitoring device;

[0050] In this embodiment, the indenter of the probe can reach the micrometer level.

[0051] The load-displacement curve of the pressure head in the acquisition probe monitoring device includes:

[0052] When using a probe monitoring device to perform a probe indentation test on the rock sample to be tested, the probe randomly selects a region on the loading surface of the rock sample as the indentation region and collects the load-displacement curve of the indenter during indentation.

[0053] Step S3: Obtain the approximate Poisson's ratio of the rock sample using empirical estimation methods;

[0054] Step S4: Based on the load-displacement curve, the Oliver-Pharr method is used to substitute the approximate Poisson's ratio to obtain the approximate elastic modulus of the rock sample to be tested.

[0055] In this embodiment, the Poisson's ratio is determined by an empirical estimation method, and the approximate elastic modulus of the rock sample to be tested is obtained by substituting the approximate Poisson's ratio into the Oliver-Pharr method.

[0056] The formulas for calculating the elastic parameters of the rock sample based on the Oliver-Pharr method are as follows:

[0057] ;

[0058] in, The first parameter is obtained by fitting using the least squares method. The second parameter is obtained by fitting using the least squares method. The third parameter is obtained by fitting using the least squares method; The probe insertion depth. The contact stiffness of the rock sample to be tested. The hardness of the rock sample. For maximum load, This refers to the contact area between the probe indenter and the rock sample being tested. The reduced elastic modulus of the rock sample. These are parameters related to the geometry of the probe indenter. This represents the approximate elastic modulus of the rock sample to be tested. The approximate Poisson's ratio of the tested rock sample (obtained by empirical estimation methods). For load, Let be Poisson's ratio. The above calculation uses a load-displacement curve to obtain the maximum load. Probe insertion depth ,like Figure 6 As shown, the loading and unloading curves of the probe indentation test are illustrated. The probe indentation test process includes a loading stage, a holding stage, and an unloading stage. The loading stage can be considered as a combination of elastic and plastic deformation, the holding stage measures the displacement change under a constant loading force, and the unloading stage is considered as the recovery process of purely elastic deformation. max h is the maximum indentation depth f P represents the indentation depth after complete unloading. max S represents the maximum load during the dotting process, and S represents the contact stiffness.

[0059] Step S5: Use a laser rangefinder to measure the key marker points in the probe indentation area and record the experimental indentation depth of the key marker points;

[0060] In this embodiment, after the test is completed, the indentation area is cleaned, a laser rangefinder is used to measure the key marker points in the probe indentation area, the indentation depth of the key marker points is recorded, and a cross-sectional view of the indentation area is constructed.

[0061] The step of measuring the key marker points in the indentation area using a laser rangefinder and recording the experimental indentation depth of the key marker points includes: after the probe indentation test is completed, using a laser rangefinder to measure the indentation depth of the probe at the key marker points in the indentation area, and the measured depth by the laser rangefinder is the experimental indentation depth of the key marker points.

[0062] like Figure 5 As shown, after the experiment, a laser scanner was used to extract the indentation depth data of the specific location coordinates of the probe indentation area. An xy coordinate system was added to extract the experimental data, laying the foundation for the subsequent inversion method. The experimental data consisted of: xy coordinate positions and indentation depth, with the indentation depth represented by b. i .

[0063] Step S6: Establish numerical models of the probe and the rock sample to be tested in the finite element software, and substitute the approximate elastic modulus and approximate Poisson's ratio of the rock sample to be tested into the numerical models of the probe and the rock sample to be tested to obtain the simulated indentation depth of the key marker points.

[0064] Step S7: Based on the multi-objective error function, use the simulated annealing particle swarm optimization algorithm to optimize the approximate elastic modulus and approximate Poisson's ratio of the rock sample to be tested, and output the optimized Poisson's ratio and optimized elastic modulus. The multi-objective error function is established based on the difference between the experimental indentation depth of the key marker points and the simulated indentation depth of the key marker points.

[0065] Among them, the optimized Poisson's ratio is the true Poisson's ratio, and the optimized elastic modulus is the true elastic modulus.

[0066] The multi-objective error function is calculated as follows:

[0067] ;

[0068] in, For multi-objective error functions, The number of key markers, For the i-th key marker, Key markers The experimental indentation depth, Key markers The simulated indentation depth.

[0069] Secondly, the present invention also provides a probe monitoring device, such as... Figure 3 As shown, it includes: a power supply module 3, a power output module, a data acquisition and storage module 4, and a laser rangefinder 12;

[0070] The power supply module 3 is connected to the data acquisition and storage module 4, the power output module and the laser rangefinder 12 respectively, and is used to provide power to the probe monitoring device.

[0071] In this embodiment, the power supply module 3 contains 6 battery packs.

[0072] The power output module is connected to the data acquisition and storage module 4 and includes a servo controller 5, a stepper motor 7, a ball screw 10, a weighing sensor 11, and a probe 13. The servo controller 5 is equipped with a loading rate regulator 6, which is used to control the probe 13 to press into the rock sample to be tested at a fixed loading rate.

[0073] In this embodiment, the loading rate regulator 6 has a control panel for controlling the data transmission between various modules. After the rock sample is placed, the loading rate is first set, the probe is started to press into the rock sample, and the data acquisition and storage module 4 records the data of the pressing process. After the pressing test is completed, the laser rangefinder 12 is operated on the loading rate regulator 6 to scan the area where the probe is pressed into the rock sample and output the depth data of the pressing area.

[0074] In this embodiment, the servo controller 5 is connected to the stepper motor 7 to control the speed of the stepper motor 7. The stepper motor 7 is connected to the ball screw 10, and the rotational motion of the stepper motor 7 is converted into the linear motion of the ball screw 10. The end of the ball screw 10 is connected to the weighing sensor 11, which is responsible for recording the probe pressing force. The probe 13 is connected to the weighing sensor 11.

[0075] The acquisition and storage module 4 is connected to the power output module and is used to store the load-displacement curve of the indenter of the probe 13 in real time.

[0076] In this embodiment, the acquisition and storage module 4 contains an SD storage card.

[0077] The laser rangefinder 12 is used to measure the key marker points in the indentation area and record the experimental indentation depth of the key marker points.

[0078] The indenter of the probe 13 is a diamond Bose indenter.

[0079] like Figure 3 As shown, switch button 1 controls the on / off state of power supply module 3, handle 2 can be used for handheld operation, and power supply module 3 supplies power to electrical components such as acquisition and storage module 4, servo controller 5, loading rate regulator 6, and stepper motor 7. Servo controller 5 receives instructions from loading rate regulator 6 to drive stepper motor 7. The pressure plate 8 has a hole in the middle to connect stepper motor 7 and ball screw 10. Ball screw 10 is connected downwards to weighing sensor 11 and probe 13 to apply pressure to the rock sample and detect pressure signals. Laser rangefinder 12 tests the pressed area after acquisition, and both signals are transmitted to acquisition and storage module 4. Pressure plate 8 is supported by pressure column 9, which is connected to rigid base plate 15. Rock sample placement platform 14 is fixed in the center of rigid base plate 15, directly below probe 13, and is used to place the rock sample to be tested.

[0080] like Figure 4 As shown in the enlarged view of the probe monitoring device, the ball screw 10 is connected to the weighing sensor 11, which also integrates a laser rangefinder 12, which can measure the indentation area after the test. The rock sample to be tested is placed on the rock sample placement platform at the bottom.

[0081] In this embodiment, the probe indentation test technology can usually only estimate the Poisson's ratio of the material to be tested, thereby obtaining the approximate elastic modulus of the rock sample, but cannot obtain the true Poisson's ratio of the material to be tested, and the measured elastic modulus also has a certain error. In this embodiment, a laser rangefinder 12 is added to the probe monitoring device, which can press the probe into the fractured area to perform laser ranging, thereby obtaining the probe indentation depth at a specific location (i.e., obtaining experimental data). By establishing a finite element model and a probe model (i.e., obtaining simulation data), a multi-objective error function for the simulated indentation depth and the experimental indentation depth is constructed, and the strength mechanical parameters in the finite element model are initialized. The mechanical parameters of the probe are already known. Under the optimization of the algorithm, the approximate elastic mechanical parameters in the finite element model are iterated, and finally the true elastic mechanical parameters of the rock sample can be obtained.

[0082] The various embodiments in this application are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0083] The scope of protection of this application is not limited to the embodiments described above. Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from the scope and spirit of this disclosure. If such modifications and variations fall within the scope of equivalent technology of this disclosure, then the intent of this disclosure also includes such modifications and variations.

Claims

1. A method for simultaneously measuring the elastic modulus and Poisson's ratio of rock mass, characterized in that, include: A probe monitoring device was used to perform probe indentation tests on the rock samples to be tested; The load-displacement curve of the pressure head in the probe monitoring device was collected; The approximate Poisson's ratio of the rock sample was obtained based on empirical estimation methods; Based on the load-displacement curve, the approximate elastic modulus of the rock sample to be tested is obtained by substituting the approximate Poisson's ratio into the Oliver-Pharr method. After the indentation test, a laser rangefinder was used to measure the key marker points in the probe indentation area, record the experimental indentation depth of the key marker points, and construct a cross-sectional view of the indentation area. Numerical models of the probe and the rock sample to be tested are established in finite element software. The approximate elastic modulus and approximate Poisson's ratio of the rock sample to be tested are substituted into the numerical models of the probe and the rock sample to be tested to obtain the simulated indentation depth of the key marker points. Based on the multi-objective error function, the approximate elastic modulus and approximate Poisson's ratio of the rock sample to be tested are optimized using the simulated annealing particle swarm algorithm, and the optimized Poisson's ratio and optimized elastic modulus are output. The multi-objective error function is established based on the difference between the experimental indentation depth of the key marker point and the simulated indentation depth of the key marker point. The multi-objective error function is calculated as follows: ； in, For multi-objective error functions, The number of key markers, For the i-th key marker, Key markers The experimental indentation depth, Key markers Simulated indentation depth; The step of measuring the key marker points in the indentation area using a laser rangefinder and recording the experimental indentation depth of the key marker points includes: after the probe indentation test is completed, using a laser rangefinder to measure the indentation depth of the probe at the key marker points in the indentation area, and the measured depth by the laser rangefinder is the experimental indentation depth of the key marker points.

2. The method for simultaneously measuring the elastic modulus and Poisson's ratio of rock mass according to claim 1, characterized in that, The method employs a probe monitoring device to perform probe indentation testing on the rock sample to be tested, including: The rock sample to be tested is processed and then fixed in the probe monitoring device; A probe monitoring device was used to perform probe indentation tests on the fixed rock samples.

3. The method for simultaneously measuring the elastic modulus and Poisson's ratio of rock mass according to claim 1, characterized in that, The processing of the rock sample to be tested includes: The rock sample is cut, ground, and polished to form the rock sample to be tested. The height of the rock sample to be tested is <10mm.

4. The method for simultaneously measuring the elastic modulus and Poisson's ratio of rock mass according to claim 1, characterized in that, The load-displacement curve of the pressure head in the acquisition probe monitoring device includes: When using a probe monitoring device to perform a probe indentation test on the rock sample to be tested, the probe randomly selects a region on the loading surface of the rock sample as the indentation region and collects the load-displacement curve of the indenter during indentation.

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