A device and method for testing rock deformation characteristics under controllable periodic confining pressure impact conditions

Abstract

The present invention discloses a device and method for testing rock deformation characteristics under controllable periodic confining pressure impact conditions. This device belongs to the field of marine rock mechanical parameter measurement and includes a water tank equipped with: a base located at the bottom of the water tank for supporting a rock sample; a strain gauge disposed on the surface of the rock sample for measuring strain signals; an axial pressure rod disposed at the upper end of the rock sample for applying an axial load to the rock sample; an acoustic emission probe disposed within the axial pressure rod for detecting elastic wave signals from the rock sample; a vertically arranged scale guide rail with its bottom fixed to the water tank; a confining pressure impact component slidingly mounted on the scale guide rail; a lifting controller for controlling the elevation of the confining pressure impact component, which simulates the confining pressure impact of waves on the rock sample through free fall; and a data collection and controller for receiving elastic wave and strain signals. This invention achieves a realistic reproduction of the multi-field coupled mechanical behavior of rock in marine environments.

Description

Technical Field

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

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

[0003] For example, traditional uniaxial compression testing machines conforming to the GB / T23561.1-2009 standard can only achieve axial loading under constant confining pressure. However, in a real marine environment, wave impacts exert intense transient dynamic effects, and traditional uniaxial compression testing machines are completely unable to reproduce this complex and dynamic process. Consequently, the data obtained using such equipment cannot truly reflect the mechanical behavior of rock in a marine environment.

[0004] While the Hopkinson bar, based on the ASTM D3479-95 standard, can apply impact loads and, to a certain extent, simulate dynamic loading, it suffers from significant drawbacks. First, it lacks effective control over the confining pressure environment, a complex and variable environment for rocks in the ocean. This drawback severely impacts the accuracy of test results. Second, the Hopkinson bar has limitations on specimen size, further restricting its application in fully simulating the mechanical behavior of rocks in marine environments.

[0005] More importantly, existing equipment generally struggles to synchronize the impact confining pressure and load. In the marine environment, confining pressure and impact load interact and act synergistically on the rock. Existing equipment cannot simulate the real-world conditions of this synergistic interaction, resulting in significant deviations in test results from actual marine conditions.

[0006] Therefore, it is urgent to provide a device and method for testing 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 device and method for testing rock deformation characteristics under controllable periodic confining pressure impact conditions, which can simulate the real situation of rock under the synergistic effect of confining pressure and load.

[0008] According to a first embodiment of the technical solution of the present invention, a device for testing rock deformation characteristics under controllable periodic confining pressure impact conditions is provided, comprising a water tank, wherein the water tank is provided with:

[0009] a base, located at the bottom of the water tank, and used to support the rock sample;

[0010] a strain gauge, disposed on the surface of the rock sample, for measuring strain signals;

[0011] An axial compression rod is provided at the upper end of the rock sample and is used to apply an axial load to the rock sample. An acoustic emission probe is provided in the axial compression rod and is used to detect elastic wave signals of the rock sample.

[0012] At least one graduated guide rail is provided, which is vertically arranged and fixed to the water tank at the bottom. An annular confining pressure impact component is slidably provided on the graduated guide rail. A lifting controller is provided on the top of the graduated guide rail. The lifting 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 waves on the rock sample by free falling into water;

[0013] The data collection and controller is electrically connected to the acoustic emission probe and the strain gauge, and is used to receive the elastic wave signal and the strain signal.

[0014] In the above solution, a gasket is provided between the rock sample and the axial compression rod.

[0015] In the above solution, the base, rock sample, gasket and axial compression rod are all arranged in the middle of the water tank.

[0016] In the above solution, four strain gauges are provided and located in the middle of the rock sample, wherein two of the strain gauges are arranged symmetrically in the transverse direction and the other two are arranged symmetrically in the vertical direction.

[0017] In the above solution, four scale guide rails are provided, which are evenly distributed on the outside of the rock sample and are spaced apart from the rock sample.

[0018] In the above solution, the water tank is a cylindrical structure with an open upper end.

[0019] In the above solution, the confining pressure impact component is a circular ring structure with a diameter of 500 mm, and the secondary radius of the circular ring is 5 mm.

[0020] In the above solution, the axial pressure 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 at which the driving device applies the axial load to control the axial load value applied by the driving device.

[0021] In the above scheme, the elastic wave signal is generated according to the internal expansion crack of the rock sample. After receiving the elastic wave signal, the data collection and controller identifies the damage evolution stage of the rock sample through spectrum analysis, and after receiving the strain signal, calculates the real-time stress-strain curve in combination with the axial load value.

[0022] According to a second aspect of the technical solution of the present invention, a method for testing rock deformation characteristics under controllable periodic confining pressure impact conditions is provided, using a device for testing rock deformation characteristics under controllable periodic confining pressure impact conditions as described in any one of the above-mentioned solutions, the method comprising:

[0023] S1. Select representative rock as the sample and place it on a base with the top of the rock sample 50 mm above the water surface to simulate the wave action on real coastal rocks.

[0024] S2. Install the strain gauge on the rock specimen. After installation, adjust the axial compression rod to apply axial load.

[0025] S3. After the axial load is applied, the drop height and drop interval of the confining pressure impact component are controlled by the lifting controller. The confining pressure impact component applies periodic confining pressure impact to the rock sample through free fall. The drop height is calculated based on the target wave impact energy.

[0026] S4. Receive and analyze elastic wave signals and strain signals through data collection and controller.

[0027] Beneficial effects of the present invention:

[0028] The present invention discloses a device and method for testing rock deformation characteristics under controllable periodic confining pressure impact conditions. The controllable free-fall confining pressure impact component accurately simulates the periodic dynamic confining pressure generated by wave impact, and is combined with an axial pressure rod to synchronously apply axial loads, thereby achieving a true restoration of the multi-field coupled mechanical behavior of rocks in marine environments, breaking through the limitation of traditional static testing machines that cannot simulate transient dynamic effects. In addition, the integrated acoustic emission probe and strain gauge can monitor the development of microcracks inside the rock and surface strain data in real time, providing multi-dimensional evidence for revealing the failure mechanism; the impact height and frequency are accurately adjusted through the lifting controller, and the axial pressure loading rate is controlled by the drive device to meet the needs of different engineering scenarios. Its standardized design is suitable for a variety of rock types, and the test results directly serve the rock stability assessment of marine projects such as artificial islands and reefs, providing key technical support for geological disaster prevention and control and marine resource development and utilization, filling the gap in rock mechanics testing under dynamic confining pressure conditions, and significantly improving the safety and reliability of coastal projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0030] Figure 1 This is a diagram of the interior of a water tank in an embodiment of the present invention;

[0031] Figure 2 is a cross-sectional view of a water tank in an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the overall structure of the rock deformation characteristics testing device under controllable periodic confining pressure impact conditions in an embodiment of the present invention.

[0033] Among them, 1. Water tank; 2. Base; 3. Rock sample; 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.

[0034] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0035] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present disclosure. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

[0036] The terms "first," "second," and the like in the description and claims of the present disclosure are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present disclosure described herein can, for example, be implemented in orders other than those illustrated or described herein.

[0037] In addition, the terms "comprises" and "having" and any variations thereof are intended to cover a non-exclusive inclusion. For example, a process, method, system, product or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product or apparatus.

[0038] Multiple includes two or more.

[0039] It should be understood that the term "and / or" as used in this disclosure simply describes an association between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B simultaneously, or B alone.

[0040] like Figures 1-3 As 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, which is provided with:

[0041] The base 2 is located at the bottom of the water tank 1 and is used to support the rock sample 3; the strain gauge 4 is arranged on the surface of the rock sample 3 and is used to measure the strain signal; the 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. The axial pressure rod 6 is provided with an acoustic emission probe 10 for detecting the elastic wave signal of the rock sample 3; the scale guide rail 7 has at least one, which is arranged vertically and connected to the water tank 1 at the bottom. An annular confining pressure impact component 8 is slidingly provided on the scale guide rail 7, and a lifting controller 9 is provided on the top of the scale guide rail 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; the 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.

[0042] Rocks of a type consistent with the geological conditions of the target sea area (such as sandstone and granite) were selected and cut into appropriately sized specimens. Preferably, the specimens were cylindrical, 50 x 100 mm in size, with a smooth surface and no cracks. Rock specimen 3 used the 50 x 100 mm cylindrical specimen recommended by the International Society for Rock Mechanics. This facilitates comparison with existing research data and enhances the universality of the experimental results. Furthermore, under axial compression and dynamic confining pressure, the internal stress distribution of the cylindrical specimen is more uniform, reducing the possibility of localized premature failure and ensuring that the experimental data reflects the overall properties of the material.

[0043] 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 displacement of the sample during the experiment. Furthermore, the base 2 is 100mm high and the rock sample 3 is 50mm away from the water surface. The use of center positioning ensures that the force distribution of the rock sample 3 is symmetrical and uniform when it is subjected to axial load and periodic confining pressure impact. 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.

[0044] Furthermore, a gasket 5 is provided between the rock sample 3 and the axial compression 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 compression rod 6 .

[0045] In this embodiment, strain gauges 4 are preferably high-precision waterproof strain gauges. Four strain gauges 4 are located in the center of rock specimen 3. Two strain gauges 4 are arranged horizontally and symmetrically for real-time monitoring of radial strain; the other two strain gauges 4 are arranged vertically and symmetrically for measuring axial strain. Furthermore, the strain gauges 4 are secured with epoxy resin glue and coated with a waterproof sealing layer to ensure stability in underwater environments.

[0046] In this embodiment, preferably, four graduated guide rails 7 are provided, evenly distributed on the outside of the rock sample 3 and spaced a certain distance from the rock sample 3, thereby ensuring that the confining pressure impact component 8 remains stable and balanced during the ascending process.

[0047] The graduated guide rail 7 in the water tank 1 is graduated with the horizontal plane at 0. Preferably, the scale at the top of the tank 1 is 1m, and the scale at the bottom is -0.25m. Using a cylindrical tank minimizes the impact of wall reflections on water pressure fluctuations. A square tank can easily generate eddies or pressure wave reflections at its corners, disrupting the transmission path of the dynamic confining pressure. The continuous curvature of a cylindrical tank, however, allows the propagation of water shock waves to more closely resemble a real ocean environment.

[0048] The confining pressure impact component 8 is a torus with a diameter of 500 mm. Furthermore, the minor radius of the torus is 5 mm. The graduated guide rail 7 comprises an inner guide rail and an outer guide rail, located on the outer and inner sides of the torus, respectively. This ensures that the torus slides down in a straight line. The contact area between the torus and the graduated guide rail 7 is extremely small, and the kinetic energy consumed by friction during the fall is negligible, so the fall can be considered a free fall.

[0049] The lifting controller 9 suspends the confining pressure impact component 8 at the desired height and then allows it to fall freely into the water, simulating periodic confining pressure impacts of waves of varying strength on the rock. After sinking to the bottom, the lifting controller 9 slowly raises the confining pressure impact component 8 to the desired height for the next experiment. Thus, the lifting controller 9 controls the height and frequency of the confining pressure impact component 8 falling into the water.

[0050] The axial compression rod 6 is connected to an external drive device, which is electrically connected to a data collection and control unit 11. The data collection and control unit 11 is used to control the speed at which the drive device applies the axial load, thereby controlling the axial load value applied by the drive device. Preferably, the drive device is a servo motor, which drives the axial compression rod 6 to apply the axial load to the rock sample 3. Initially, the load is slowly applied at a rate of 0.1 MPa / s to the target value to avoid premature failure of the sample due to transient impact.

[0051] An acoustic emission probe 10, embedded within the axial compression rod 6, captures elastic wave signals generated by microcrack propagation within the rock in real time. Strain gauges 4 monitor the strain signals. The data collection and control unit 11 receives the elastic wave signals and uses spectral analysis to identify the damage evolution stage. The data collection and control unit 11 analyzes the strain signals and, combined with the axial load, calculates a real-time stress-strain curve to assess the rock's elastic modulus, Poisson's ratio, and yield strength. After the experiment, a comprehensive report is generated based on the data.

[0052] According to a second embodiment of the technical solution of the present invention, a method for testing rock deformation characteristics under controllable periodic confining pressure impact conditions is provided. Using the above-mentioned rock deformation characteristics testing device under controllable periodic confining pressure impact conditions, the method includes:

[0053] S1. Select representative rock as a specimen and place it on a base with the top of the specimen 50 mm above the water surface to simulate the wave action on real coastal rocks.

[0054] S2. Install the strain gauge on the rock specimen. After installation, adjust the axial compression rod to apply axial load.

[0055] S3. After the axial load is applied, the drop height and drop interval of the confining pressure impact component are controlled by the lifting controller. The confining pressure impact component applies periodic confining pressure impact to the rock sample through free fall. The drop height is calculated based on the target wave impact energy.

[0056] S4. Receive and analyze elastic wave signals and strain signals through data collection and controller.

[0057] Example

[0058] The present invention is based on actual engineering and prepares rock samples according to the geological conditions of the sea area; installs the rock samples and corresponding experimental equipment; selects the corresponding impact frequency and impact height according to the wave impact conditions in the target sea area to apply periodic confining pressure impact to the rock; and collects and analyzes multi-source data through a data collection and main control system to provide data support for the long-term stability prediction of coastal rock masses.

[0059] (1) Sample preparation and positioning

[0060] Select a rock type (such as sandstone or granite) consistent with the geological conditions of the target sea area and cut it into cylindrical specimens to standard dimensions (50 mm x 100 mm), ensuring a smooth surface and no cracks. The specimen is precisely placed at the center of the base at the bottom of the water tank, ensuring that the specimen axis aligns with the tank's centerline. The top of the specimen is 50 mm above the water surface to simulate the depth of rock buried by waves on real coastal shores. The base features a non-slip design to prevent specimen movement during the experiment.

[0061] (2) Strain gauge installation and axial load application

[0062] Four high-precision, waterproof strain gauges were symmetrically affixed to either side of the specimen's geometric center: two gauges were placed horizontally on the specimen's lateral surfaces for real-time monitoring of radial strain, and two gauges were placed vertically on the specimen's lateral surfaces for measuring axial strain. The horizontal and vertical gauges were spaced apart. The gauges were secured with epoxy resin and coated with a waterproof sealant to ensure stability in underwater environments. Subsequently, a custom-made gasket (made of a high-hardness alloy) was placed on top of the specimen, contacted by an axial compression rod driven by a servo motor to apply a preset axial load. The loading rate was precisely controlled by the data control system, initially at a rate of 0.1 MPa / s, slowly increasing to the target value to avoid premature failure of the specimen due to sudden impact.

[0063] (3) Cyclic confining pressure impact simulation

[0064] The lift controller activates and hovers a 500mm diameter metal ring at a designated height on a graduated guide rail. The height is selected based on the target wave impact energy. The ring's free-fall intervals are programmed to simulate wave loads of varying frequencies. The ring's impact on the water surface generates a transient pressure wave, which is transmitted through the water to the surrounding specimen, creating a cyclical confining pressure. After each impact, the lift controller automatically retracts the ring to the preset height, repeating the cycle to simulate continuous wave action.

[0065] (4) Synchronous collection and analysis of multi-source data

[0066] The data control system simultaneously receives signals from the acoustic emission probe and strain gauges. The acoustic emission probe, embedded within the axial compression rod, captures elastic wave signals generated by microcrack propagation within the rock in real time, identifying the damage evolution stage through spectral analysis. After data collection and analysis by the control system, the four-channel strain data is combined with the axial load to calculate a real-time stress-strain curve, assessing the rock's elastic modulus, Poisson's ratio, and yield strength. After the experiment, a comprehensive report is generated based on the data, including a frequency-strain response correlation diagram for confining pressure impact and a cumulative acoustic emission energy-time curve, providing a quantitative basis for predicting the long-term stability of marine rock masses.

[0067] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0068] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0069] Through the above description of the embodiments, those skilled in the art will clearly understand that the above-mentioned implementation methods can be implemented using software plus the necessary general-purpose hardware platform. Of course, hardware can also be used, but in many cases, the former is the more preferred implementation method. Based on this understanding, the technical solution of the present invention, or the portion 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, or optical disk) and includes a number of instructions for enabling a terminal (such as a mobile phone, computer, server, air conditioner, or network device) to execute the methods described in various embodiments of the present invention.

[0070] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A device for testing rock deformation characteristics under controllable periodic confining pressure impact conditions, characterized in that: The device realizes the true restoration of the multi-field coupled mechanical behavior of rocks in the marine environment and simulates the transient dynamic effect of wave impact in the real marine environment. The device includes a water tank, which is provided with: a base, located at the bottom of the water tank, and used to support the rock sample; a strain gauge, disposed on the surface of the rock sample, for measuring strain signals; An axial compression rod is provided at the upper end of the rock sample and is used to apply an axial load to the rock sample. An acoustic emission probe is provided in the axial compression rod and is used to detect elastic wave signals of the rock sample. At least one graduated guide rail is provided, which is vertically arranged and fixed to the water tank at the bottom. An annular confining pressure impact component is slidably provided on the graduated guide rail. A lifting controller is provided on the top of the graduated guide rail. The lifting controller is used to control the rise of the confining pressure impact component. The confining pressure impact component is used to simulate the periodic dynamic confining pressure impact of waves on the rock sample by free falling into water; A data collection and controller is electrically connected to the acoustic emission probe and the strain gauge, and is used to receive the elastic wave signal and the strain signal; A gasket is provided between the rock sample and the axial compression rod; The strain gauges are provided with four pieces and are located in the middle of the rock sample, wherein two of the strain gauges are arranged symmetrically in the transverse direction and the other two strain gauges are arranged symmetrically in the vertical direction; There are four scale guide rails, which are evenly distributed on the outside of the rock sample and spaced apart from the rock sample; The water tank is a cylindrical structure with an open top. The continuous curvature of the cylindrical structure makes the propagation of water shock waves closer to the real ocean environment. The confining pressure impact component is a torus structure with a diameter of 500 mm, and the minor radius of the torus is 5 mm; The axial pressure rod is connected to an external driving device, and the driving device is electrically connected to the data collection and controller, and the data collection and controller is used to control the speed at which the driving device applies the axial load to control the axial load value applied by the driving device; The elastic wave signal is generated according to the internal extension crack of the rock sample, and the data collection and controller identifies the damage evolution stage of the rock sample through spectrum analysis after receiving the elastic wave signal, and calculates the real-time stress-strain curve in combination with the axial load value after receiving the strain signal; The rock sample is a cylindrical sample of 50*100 mm; The driving device is a servo motor, which drives the axial pressure rod to apply axial load to the rock sample. In the initial stage, the load is loaded at 0.1 MPa / s to the target value.

2. The rock deformation characteristics testing device under controllable periodic confining pressure impact conditions according to claim 1 is characterized in that: The base, rock sample, gasket and axial pressure rod are all arranged in the middle of the water tank.

3. A method for testing rock deformation characteristics under controllable periodic confining pressure impact conditions, characterized in that: Using the rock deformation characteristics testing device under controllable periodic confining pressure impact conditions according to claim 1 or 2, the method includes: S1. Select representative rock as the sample and place it on a base with the top of the rock sample 50 mm above the water surface to simulate the wave action on real coastal rocks. S2. Install the strain gauge on the rock specimen. After installation, adjust the axial compression rod to apply axial load. S3. After the axial load is applied, the drop height and drop interval of the confining pressure impact component are controlled by the lifting controller. The confining pressure impact component applies periodic confining pressure impact to the rock sample through free fall. The drop height is calculated based on the target wave impact energy. S4. Receive and analyze elastic wave signals and strain signals through data collection and controller.

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