Rock deformation characteristic testing device and method under controllable periodic confining pressure impact condition

Abstract

The invention discloses a rock deformation characteristic testing device and method under a controllable periodic confining pressure impact condition, and belongs to the field of ocean rock mechanical parameter measurement, the rock deformation characteristic testing device comprises a water tank, the water tank is internally provided with a base located at the bottom of the water tank, and the base is used for bearing a rock sample; the strain gauge is arranged on the surface of the rock sample and is used for measuring a strain signal; the axial compression rod is arranged at the upper end of the rock sample and used for applying an axial load to the rock sample, and an acoustic emission probe is arranged in the axial compression rod and used for detecting an elastic wave signal of the rock sample; the scale guide rail is vertically arranged, the bottom of the scale guide rail is fixed to the water tank, a confining pressure impact component is slidably arranged on the scale guide rail, a lifting controller is arranged on the scale guide rail and used for controlling the confining pressure impact component to ascend, and the confining pressure impact component simulates confining pressure impact of sea waves on the rock sample through free falling into water; and the data collection and control device is used for receiving the elastic wave signal and the strain signal. According to the method, the real restoration of the rock multi-field coupling mechanical behavior in the marine environment is realized.

Description

Technical Field

[0001] The present invention relates to the field of measuring marine rock mechanical parameters, and in particular to a test device and method for rock deformation characteristics under controllable periodic confining pressure impact conditions. Background Art

[0002] In the current scope of rock mechanics research, most rock mechanics test equipment is designed based on static or quasi-static loading conditions. This characteristic results in obvious limitations when simulating the coupling effects of periodic dynamic loads such as waves and tides in the marine environment on rocks.

[0003] Taking the traditional uniaxial compression testing machine that follows the GB / T23561.1-2009 standard as an example, it can only achieve axial loading under constant confining pressure conditions. However, in the real marine environment, the impact of ocean waves has a strong transient dynamic effect, and the traditional uniaxial compression testing machine is completely unable to reproduce this complex and dynamic process. Therefore, the data obtained through such equipment is difficult to truly reflect the mechanical behavior of rocks in the marine environment.

[0004] For the Hopkinson bar that follows the ASTM D3479-95 standard, although it can apply impact loads and simulate dynamic loading conditions to a certain extent, it has significant defects. First, it lacks effective control of the confining pressure environment, and the confining pressure environment where rocks are located in the ocean is complex and variable, which seriously affects the accuracy of test results. Second, the Hopkinson bar has limitations on the specimen size, which further restricts its application in the research on comprehensively simulating the mechanical behavior of rocks in the marine environment.

[0005] More importantly, existing devices generally have difficulty in synchronously regulating the impact confining pressure and load. In the marine environment, the confining pressure and impact load interact and act on rocks synergistically. Existing equipment cannot simulate the real situation of the synergistic action of confining pressure and load, resulting in a significant deviation between the test results and the actual marine environment.

[0006] Therefore, there is an urgent need to provide a solution for a test device and method for rock deformation characteristics under controllable periodic confining pressure impact conditions. Summary of the Invention

[0007] In order to solve the above problems, the technical solution of the present invention provides a test device and method for rock deformation characteristics under controllable periodic confining pressure impact conditions, which can simulate the real situation of the synergistic action of confining pressure and load on rocks.

[0008] According to the first aspect embodiment of the technical solution of the present invention, a test device for rock deformation characteristics under controllable periodic confining pressure impact conditions is provided, including a water tank, and the water tank is provided with: A base, located at the bottom of the water tank, and the base is used to carry a rock specimen; A strain gauge is arranged on the surface of the rock specimen for measuring strain signals; An axial compression rod is arranged at the upper end of the rock specimen for applying an axial load to the rock specimen. An acoustic emission probe is arranged inside the axial compression rod for detecting elastic wave signals of the rock specimen; At least one scale guide rail is arranged vertically, with the bottom fixed to the water tank. A ring-shaped confining pressure impact component is slidably arranged on the scale guide rail. An elevation controller is arranged at the top of the scale guide rail, and the elevation controller is used to control the rise of the confining pressure impact component. The confining pressure impact component is used to simulate the confining pressure impact of ocean waves on the rock specimen by free fall; A data collection and controller is electrically connected to the acoustic emission probe and the strain gauge for receiving the elastic wave signals and strain signals.

[0009] In the above solution, a gasket is arranged between the rock specimen and the axial compression rod.

[0010] In the above solution, the base, the rock specimen, the gasket and the axial compression rod are all arranged in the middle of the water tank.

[0011] In the above solution, 4 strain gauges are arranged in the middle of the rock specimen. Among them, two of the strain gauges are symmetrically arranged horizontally, and the other two strain gauges are symmetrically arranged vertically.

[0012] In the above solution, four scale guide rails are arranged evenly outside the rock specimen and are spaced from the rock specimen.

[0013] In the above solution, the water tank is a cylindrical structure with an open upper end.

[0014] In the above solution, the confining pressure impact component is a toroidal structure with a diameter of 500 mm, and the minor radius of the torus is 5 mm.

[0015] In the above solution, the axial compression rod is connected to an external driving device, and the driving device is electrically connected to the data collection and controller. The data collection and controller is used to control the speed of the driving device applying the axial load to control the value of the axial load applied by the driving device.

[0016] In the above solution, the elastic wave signals are generated according to internal propagating cracks in the rock specimen. After receiving the elastic wave signals, the data collection and controller identifies the damage evolution stage of the rock specimen through spectral analysis, and calculates the real-time stress-strain curve by combining the received strain signals with the value of the axial load.

[0017] According to the second aspect embodiment of the technical solution of the present invention, a method for testing the deformation characteristics of rocks under controllable periodic confining pressure impact is provided. The method uses the device for testing the deformation characteristics of rocks under controllable periodic confining pressure impact described in any one of the above solutions. The method includes: S1. Select a representative rock as the specimen, place the rock specimen on the base, and keep the top of the rock specimen 50 mm away from the water surface to simulate the action of waves on real coastal rocks; S2. Install strain gauges on the rock specimen. After installation, adjust the axial load rod to apply axial load; S3. After starting to apply the axial load, use the lifting controller to control the falling height and falling interval of the confining pressure impact component. The confining pressure impact component applies periodic confining pressure impact on the rock specimen through free fall. Among them, the falling height is converted according to the target wave impact energy; S4. Receive and analyze elastic wave signals and strain signals through the data collection and controller.

[0018] Beneficial effects of the present invention: A device and method for testing the deformation characteristics of rocks under controllable periodic confining pressure impact disclosed by the present invention. The confining pressure impact component with controllable free fall accurately simulates the periodic dynamic confining pressure generated by wave impact, and combines with the axial load rod to synchronously apply axial load, realizing the true restoration of the multi-field coupling mechanical behavior of rocks in the marine environment and breaking through the limitation that traditional static testing machines cannot simulate transient dynamic effects. And integrating acoustic emission probes and strain gauges can monitor the development of internal microcracks and surface strain data of rocks in real time, providing multi-dimensional evidence for revealing the failure mechanism; accurately adjusting the impact height and frequency through the lifting controller, and controlling the axial load loading rate through the driving device to meet the requirements of different engineering scenarios. Its standardized design is suitable for various rock types, and the test results directly serve the evaluation of the rock mass stability of marine engineering such as artificial reefs, providing key technical support for geological disaster prevention and control and the development and utilization of marine resources, filling the blank of rock mechanics testing under dynamic confining pressure conditions, and significantly improving the safety and reliability of coastal engineering. Description of the drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0020] Figure 1 It is the internal view of the water tank in the embodiment of the present invention; Figure 2 It is the sectional view of the water tank in the embodiment of the present invention; Figure 3 This is the overall schematic diagram of the rock deformation characteristic testing device under controllable periodic confining pressure impact conditions in the embodiments of the present invention.

[0021] Among them, 1. water tank; 2. base; 3. rock specimen; 4. strain gauge; 5. gasket; 6. axial pressure rod; 7. scale guide rail; 8. confining pressure impact component; 9. lifting controller; 10. acoustic emission probe; 11. data collection and controller.

[0022] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific embodiments

[0023] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0024] The terms "first", "second", etc. in the specification and claims of the present disclosure are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein.

[0025] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] Multiple means including two or more.

[0027] And / or, it should be understood that for the term "and / or" used in the present disclosure, it is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0028] As Figures 1 to 3 shown, an embodiment of the technical solution of the present invention provides a rock deformation characteristic testing device under controllable periodic confining pressure impact conditions, including a water tank 1, and the water tank 1 is provided with: A base 2 is located at the bottom of the water tank 1, and the base 2 is used to carry the rock sample 3; a strain gauge 4 is arranged on the surface of the rock sample 3 and is used to measure the strain signal; an axial pressure rod 6 is arranged at the upper end of the rock sample 3 and is used to apply an axial load to the rock sample 3. An acoustic emission probe 10 is arranged in the axial pressure rod 6 and is used to detect the elastic wave signal of the rock sample 3; a scale guide 7 is provided with at least one, which is vertically arranged and connected to the water tank 1 at the bottom. An annular confining pressure impact component 8 is slidably provided on the scale guide 7, and a lifting controller 9 is provided on the top of the scale guide 7. The lifting controller 9 is used to control the rise of the confining pressure impact component 8. The confining pressure impact component 8 is used to simulate the confining pressure impact of waves on the rock sample 3 by free falling into water; a data collection and controller 11 is electrically connected to the acoustic emission probe 10 and the strain gauge 4 and is used to receive elastic wave signals and strain signals.

[0029] Among them, the rock type (such as sandstone, granite, etc.) that is consistent with the geological conditions of the target sea area is selected and cut into samples of appropriate size. Preferably, the sample size is a cylindrical sample of 50*100mm with a flat surface and no cracks. Rock sample 3 uses a cylindrical sample of 50*100mm recommended by the International Society for Rock Mechanics, which is convenient for comparison with existing research data and enhances the universality of the experimental results. Under the action of axial compression and dynamic confining pressure, the internal stress distribution of the cylindrical sample is more uniform, reducing the possibility of local premature failure and ensuring that the experimental data reflects the overall characteristics of the material.

[0030] The base 2, rock sample 3, gasket 5 and axial pressure rod 6 are all arranged in the middle of the water tank 1. In this embodiment, the water tank 1 is a cylindrical structure with an open upper end and a diameter of 1.5m. The base 2, rock sample 3, gasket 5 and axial pressure rod 6 are all arranged at the center of the water tank 1, and ensure that the axis of the sample coincides with the center line of the water tank 1. The base 2 adopts an anti-slip design to avoid sample displacement during the experiment. Furthermore, the base 2 is 100mm high and the rock sample 3 is 50mm from the water surface. The center positioning is adopted to make the force distribution of the rock sample 3 symmetrical and uniform when it is subjected to axial load and periodic confining pressure shock. If the rock sample 3 deviates from the center, it may cause uneven transmission of the confining pressure shock wave (such as excessive pressure on one side), induce local stress concentration, and affect the accuracy of the experimental results.

[0031] Furthermore, a gasket 5 is provided between the rock sample 3 and the axial pressure rod 6 . The gasket 5 is made of a high-hardness alloy so that the rock sample 3 is subjected to uniform force when axially loaded by the axial pressure rod 6 .

[0032] Preferably, in this embodiment, the strain gauge 4 is a high-precision waterproof strain gauge. There are 4 strain gauges 4, located in the middle of the rock specimen 3. Among them, two strain gauges 4 are symmetrically arranged horizontally for real-time monitoring of radial strain; the other two strain gauges 4 are symmetrically arranged vertically for measuring axial strain. Further, the strain gauge 4 is fixed with epoxy resin glue and a waterproof sealing layer is coated to ensure stability in the underwater environment.

[0033] Preferably, in this embodiment, there are four scale guide rails 7, which are evenly distributed outside the rock specimen 3 and have a certain interval from the rock specimen 3. This ensures that the confining pressure impact component 8 remains stable and balanced during the rising process.

[0034] The scale of the scale guide rail 7 in the water tank 1 is based on the horizontal plane as 0. Preferably, the top scale of the water tank 1 is 1 m, and the bottom scale of the water tank 1 is -0.25 m. Using a cylindrical water tank can minimize the influence of wall reflection on water pressure fluctuations. If a square water tank is used, eddies or pressure wave reflections are likely to occur at the corners, interfering with the transmission path of the dynamic confining pressure; while the continuous curvature of the cylindrical water tank makes the propagation of the water flow shock wave closer to the real ocean environment.

[0035] The confining pressure impact component 8 is a toroidal structure with a diameter of 500 mm. Further, the minor radius of the torus is 5 mm. The scale guide rail 7 has an inner guide rail and an outer guide rail, which are respectively located outside the outer ring and inside the inner ring of the toroidal structure to ensure that the toroidal structure slides down in a straight line. The contact area between the toroidal structure and the scale guide rail 7 is extremely small, and the kinetic energy consumed by friction during the falling process can be ignored. Therefore, the fall can be considered a free fall.

[0036] The lifting controller 9 hovers the confining pressure impact component 8 at the required height and then allows it to fall freely into the water, which is used to simulate the periodic confining pressure impact of different intensity waves on the rock; after the confining pressure impact component 8 sinks to the bottom, the lifting controller 9 slowly lifts the confining pressure impact component 8 to the height required for the next experiment. Therefore, the lifting controller 9 controls the falling height and falling frequency of the confining pressure impact component 8.

[0037] The axial pressure rod 6 is connected to an external driving device, and the driving device is electrically connected to the data collection and controller 11. The data collection and controller 11 is used to control the speed of the driving device applying the axial load to control the value of the axial load applied by the driving device. Preferably, the driving device is a servo motor. The axial pressure rod 6 is driven by the servo motor to apply an axial load to the rock specimen 3. In the initial stage, it is slowly loaded to the target value at 0.1 MPa / s to avoid premature failure of the specimen caused by instantaneous impact.

[0038] The acoustic emission probe 10 is embedded inside the axial compression bar 6 to capture in real time the elastic wave signals generated by the propagation of microcracks inside the rock. The strain gauge 4 is used to monitor the strain signals. After receiving the elastic wave signals, the data collection and controller 11 identifies the damage evolution stage through spectral analysis; after receiving the strain signals, the data collection and controller 11 analyzes them and calculates the real-time stress-strain curve in combination with the axial load value to evaluate the elastic modulus, Poisson's ratio and yield strength of the rock. After the experiment, a comprehensive report is generated based on the data.

[0039] According to the second aspect embodiment of the technical solution of the present invention, a method for testing the deformation characteristics of rock under controllable periodic confining pressure impact is provided. Using the above-mentioned testing device for the deformation characteristics of rock under controllable periodic confining pressure impact, the method includes: S1. Select a representative rock as the specimen, place the rock specimen on the base, and the top of the rock specimen is 50 mm away from the water surface to simulate the action of waves on real coastal rocks. S2. Install strain gauges on the rock specimen, and after installation, adjust the axial compression bar to apply axial load. S3. After starting to apply the axial load, use the lifting controller to control the falling height and falling interval of the confining pressure impact component. The confining pressure impact component applies periodic confining pressure impact to the rock specimen through free fall. Among them, the falling height is converted according to the target wave impact energy. S4. Receive and analyze the elastic wave signals and strain signals through the data collection and controller.

[0040] Embodiment Based on actual engineering, the present invention prepares rock specimens according to the geological conditions of the sea area; installs the rock specimens and corresponding experimental equipment; selects the corresponding impact frequency and impact height according to the wave impact conditions of the target sea area to apply periodic confining pressure impact to the rock; collects and analyzes multi-source data through the data collection and main control system to provide data support for the long-term stability prediction of coastal rock masses.

[0041] (1) Specimen preparation and positioning Select a rock type that conforms to the geological conditions of the target sea area (such as sandstone, granite, etc.), cut it into a cylindrical specimen according to the standard size (50 mm × 100 mm), and ensure that the surface is flat and free of cracks. Place the specimen accurately at the center of the base at the bottom of the water tank to ensure that the axis of the specimen coincides with the center line of the water tank. The top of the specimen is 50 mm away from the water surface to simulate the burial depth condition of real coastal rocks under the action of waves. The base is designed with anti-slip to avoid displacement of the specimen during the experiment.

[0042] (2) Strain gauge installation and axial load application Four high-precision waterproof strain gauges are symmetrically pasted on both sides of the geometric center of the specimen: two are arranged horizontally on the side surface of the specimen for real-time monitoring of radial strain; two are arranged longitudinally on the side surface of the specimen for measuring axial strain. Among them, there is a certain interval between the horizontally arranged strain gauges and the longitudinally arranged strain gauges. The strain gauges are fixed with epoxy resin glue and a waterproof sealing layer is coated to ensure stability in the underwater environment. Subsequently, a special gasket (made of high-hardness alloy) is placed on the top of the specimen, and the axial compression rod contacts the gasket. The servo motor is used to drive the axial compression rod to apply a preset axial load. The loading rate is precisely controlled by the data main control system. In the initial stage, it is slowly loaded to the target value at 0.1 MPa / s to avoid premature failure of the specimen caused by instantaneous impact.

[0043] (3) Simulation of periodic confining pressure impact Start the lifting controller and hover a metal ring with a diameter of 500 mm at the specified height on the scale guide rail. The height is selected based on the conversion of the target wave impact energy. The interval time for the free fall of the ring is set through the program to simulate wave loads of different frequencies. When the ring falls instantaneously and impacts the water surface, a transient pressure wave is generated, which is transmitted through the water body to form a periodic confining pressure around the specimen. After each impact, the lifting controller automatically retracts the ring to the preset height, and the cycle operation is performed to simulate the continuous action of ocean waves.

[0044] (4) Synchronous acquisition and analysis of multi-source data The data main control system synchronously receives the signals from the acoustic emission probe and the strain gauges: the acoustic emission probe is embedded inside the axial compression rod to capture the elastic wave signals generated by the propagation of microcracks inside the rock in real time, and the damage evolution stage is identified through spectrum analysis; after the four-way strain data are analyzed by the data collection and main control system, the real-time stress-strain curve is calculated in combination with the axial load value to evaluate the elastic modulus, Poisson's ratio and yield strength of the rock. After the experiment, a comprehensive report is generated based on the data, including the correlation map of confining pressure impact frequency-strain response, the acoustic emission cumulative energy-time curve, etc., providing a quantitative basis for the long-term stability prediction of marine rock masses.

[0045] It should be noted that in this article, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including that element.

[0046] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

[0047] Through the description of the above embodiments, those skilled in the art can clearly understand that the above implementation methods can be realized by means of software plus a necessary general hardware platform. Of course, they can also be realized by hardware. However, in many cases, the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions for causing a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in various embodiments of the present invention.

[0048] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative rather than restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the claims of the present invention. These all belong to the protection scope of the present invention.

Claims

1. A test device for the deformation characteristics of rocks under controllable periodic confining pressure impact, characterized in that, It includes a water tank, and inside the water tank are provided with: a base located at the bottom of the water tank, and the base is used for carrying the rock specimen; strain gauges arranged on the surface of the rock specimen for measuring strain signals; an axial compression rod arranged at the upper end of the rock specimen for applying an axial load to the rock specimen, and an acoustic emission probe is arranged inside the axial compression rod for detecting the elastic wave signals of the rock specimen; at least one scale guide rail is vertically arranged, the bottom of which is fixed to the water tank. A ring-shaped confining pressure impact component is slidably arranged on the scale guide rail, and a lifting controller is arranged at the top of the scale guide rail. The lifting controller is used to control the rise of the confining pressure impact component, and the confining pressure impact component is used to simulate the confining pressure impact of ocean waves on the rock specimen by free fall of water; a data collection and controller is electrically connected to the acoustic emission probe and the strain gauges for receiving the elastic wave signals and strain signals.

2. The test device for rock deformation characteristics under controllable periodic confining pressure impact conditions according to claim 1, wherein A gasket is arranged between the rock specimen and the axial compression rod.

3. The rock deformation characteristic testing device under controllable periodic confining pressure impact conditions according to claim 1, wherein The base, the rock specimen, the gasket and the axial compression rod are all arranged in the middle of the water tank.

4. The test device for rock deformation characteristics under controllable periodic confining pressure impact according to claim 1, characterized in that, There are 4 strain gauges arranged in the middle of the rock specimen. Among them, two of the strain gauges are symmetrically arranged horizontally, and the other two strain gauges are symmetrically arranged vertically.

5. The test device for rock deformation characteristics under controllable periodic confining pressure impact conditions according to claim 1, wherein There are four scale guide rails evenly distributed outside the rock specimen and having a gap with the rock specimen.

6. The test device for rock deformation characteristics under controllable periodic confining pressure impact conditions according to claim 1, wherein, The water tank is a cylindrical structure with an open upper end.

7. The test device for rock deformation characteristics under controllable periodic confining pressure impact conditions according to claim 1, wherein The confining pressure impact component is a toroidal structure with a diameter of 500 mm, and the minor radius of the toroid is 5 mm.

8. The test device for rock deformation characteristics under controllable periodic confining pressure impact conditions according to claim 1, wherein The axial compression rod is connected to an external driving device, and the driving device is electrically connected to the data collection and controller. The data collection and controller is used to control the speed of the axial load applied by the driving device to control the value of the axial load applied by the driving device.

9. The test device for rock deformation characteristics under controllable periodic confining pressure impact conditions according to claim 8, characterized in that, The elastic wave signals are generated according to the internal propagation cracks of the rock specimen. After receiving the elastic wave signals, the data collection and controller identifies the damage evolution stage of the rock specimen through spectral analysis, and calculates the real-time stress-strain curve by combining the axial load value after receiving the strain signals.

10. A test method for the deformation characteristics of rocks under controllable periodic confining pressure impact, characterized in that, Using the test device for the deformation characteristics of rocks under controllable periodic confining pressure impact according to any one of claims 1-9, the method includes: S1. Select a representative rock as the specimen, place the rock specimen on the base, and the top of the rock specimen is 50 mm away from the water surface to simulate the action of waves on real coastal rocks; S2. Install strain gauges on the rock specimen, and adjust the axial load applied by the axial compression rod after installation; S3. After starting to apply the axial load, use the lifting controller to control the falling height and falling interval of the confining pressure impact component. The confining pressure impact component applies periodic confining pressure impact to the rock specimen by free fall, wherein the falling height is converted according to the target wave impact energy; S4. Receive and analyze the elastic wave signals and strain signals through the data collection and controller.

Images