A method for preparing multiphase transparent soil and rock samples and a visualization-based combined testing system

Abstract

This invention relates to the field of rock mechanics testing technology, and discloses a method for preparing multiphase transparent rock and soil samples and a visualization combined testing system. The sample preparation method includes the following steps: S1, mixing molten quartz sand and transparent glass sand, washing, cooling, and holding at a temperature until solidified to form a transparent skeleton structure module; S2, removing impurities from amorphous silica formed by melting natural silica, washing with water and mixing with an epoxy resin solution to form a transparent rock matrix module; S3, filling the transparent rock matrix module and the transparent skeleton structure module into a sample molding mold and mixing evenly; S4, demolding and natural cooling; S5, cleaning with anhydrous ethanol and then drying to obtain a multiphase transparent rock and soil sample. This invention achieves real-time visualization monitoring of the target sample, and realizes acoustic-optical-thermal-electrical joint monitoring of the target sample through a four-dimensional combined testing system.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics testing technology, and in particular to a method for preparing multiphase transparent rock and soil samples and a visualization-based combined testing system. Background Technology

[0002] The triaxial compression testing apparatus for rocks provides crucial rock mechanics response data for civil engineering by simulating real-world geostress environments. This technology not only measures core parameters such as compressive strength and elastic modulus but also reveals the deformation patterns and failure mechanisms of rock masses under confining pressure. Engineering structures designed based on the test results combine safety and economy, significantly reducing the risk of geological disasters and improving engineering stability. This method simultaneously advances the refinement of rock mechanics theory, becoming an indispensable technical support for deep underground engineering construction and disaster prevention.

[0003] In the field of rock mechanics testing, traditional triaxial compression testing apparatuses employ a sealed pressure chamber made of high-strength alloy steel as the core load-bearing structure. During the test, the rock specimen is completely placed within this sealed chamber, and a pressurizing medium (usually engine oil or water) is injected into the chamber via a hydraulic system, thereby applying a preset confining pressure environment around the specimen to simulate the formation stress state. Under these closed conditions, the apparatus's built-in force sensors and strain acquisition system continuously record key mechanical response parameters of the specimen, such as axial load and circumferential deformation. Simultaneously, the pressure chamber wall is an opaque solid structure, and test data signals are transmitted through an internal signal interface on the pressure chamber base.

[0004] Existing traditional triaxial compression tests are limited by the closed structure of the steel opaque pressure chamber, resulting in three core bottlenecks: 1. Deformation process is not visible: The real-time deformation behavior of rock samples under confining pressure (such as the formation of local shear bands and the propagation of tensile cracks) cannot be directly observed due to the obstruction of the solid cavity wall. The failure mode can only be indirectly inferred through mechanical data. 2. Lack of multi-physics data: Data acquisition mainly focuses on mechanical signals (stress-strain curves), while key physical field signals such as acoustic emission energy release and thermal infrared radiation are difficult to acquire synchronously due to the difficulty in sensor deployment; 3. Internal damage is invisible: The initiation and penetration of microcracks inside real rock samples (especially at the interface of multiphase media) are completely invisible due to the non-transparent nature of the material, which makes the study of damage evolution mechanism dependent on the inversion analysis of the post-failure profile.

[0005] Therefore, in order to overcome the inherent limitations of traditional triaxial testing devices and specimens, it is urgent to construct a transparent multiphysics field joint testing system. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing multiphase transparent rock and soil samples and a visualization-based joint testing system. This system will simultaneously realize real-time visualization observation of the entire process of rock deformation and failure under confining pressure, accurate acquisition of multi-physics field signals, and three-dimensional dynamic evolution analysis of the internal crack network of transparent rock and soil samples, thereby promoting the transformation of rock mass failure mechanism research from indirect speculation to in-situ observation.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for preparing multiphase transparent soil and rock samples includes the following steps. S1, First, fused silica sand and transparent glass sand are mixed in a mass ratio, and after plasma cleaning, they are placed in a template. After being injected into the mold, they are immediately transferred to a gradient freezing system to cool down to the target temperature in stages, and kept warm until the transparent skeleton structure is fully cured to form a transparent skeleton structure module. S2 involves deep impurity removal from amorphous silica formed by melting natural silica. The melt is then subjected to ultrasonic-enhanced acid washing to dissolve residual metal oxides, followed by plasma water washing and mixing with epoxy resin solution to form a transparent rock matrix module. S3, pour the transparent rock matrix module formed in step S2 into the sample shaping mold, then fill the transparent skeleton structure module formed in step S1 into the sample shaping mold, and vibrate the mold to make the transparent rock matrix module and transparent skeleton structure mix evenly. S4, demold the sample qualitative mold and allow the obtained sample to cool naturally at room temperature; S5. Clean the surface of the sample obtained in step S4 with anhydrous ethanol, and dry the cleaned sample in a drying oven to obtain a multiphase transparent rock and soil sample.

[0008] As a further feature of the present invention, in step S1, the mass ratio of molten silica sand to transparent glass is 1:1; the gradient freezing system cools the glass in stages to -20°C at a rate of 5°C / h.

[0009] As a further feature of the present invention, in step S2, the mass ratio of the amorphous silica and epoxy resin is not less than 2.5:1.

[0010] As a further feature of the present invention, in step S2, the deep impurity removal method is to achieve a removal rate of more than 99.5% for amorphous silica impurities by axial adsorption of activated carbon rods and circumferential adsorption of alumina.

[0011] A visualization-based joint testing system includes a multiphase transparent soil sample prepared using the aforementioned method, a pressure chamber base, a visualization pressure chamber, an acoustic emission signal processing device, a digital image correlation system, an infrared camera observation system, a resistance signal processing device, and a display terminal. The visualization pressure chamber is fixedly connected to the pressure chamber base to form a sealed test space. The multiphase transparent soil sample is placed in the test space and fixedly positioned at the center of the pressure chamber base. Several observation windows are provided on the side wall of the visualization pressure chamber. The digital image correlation system and the infrared camera observation system observe the multiphase transparent soil sample through the observation windows. Signal collection patches and resistance plates are provided on the multiphase transparent soil sample. The signal collection patches and resistance plates are respectively connected to the acoustic emission signal processing device and the resistance signal processing device. The acoustic emission signal processing device, the digital image correlation system, the infrared camera observation system, and the resistance signal processing device are all electrically connected to the display terminal.

[0012] As a further feature of the present invention, the pressure chamber base is a cylindrical stepped structure and includes a first step and a second step. The first step is provided with an external signal interface on the side wall outside the test space, and the second step is provided with an internal signal interface on the side wall inside the test space. The external signal interface and the internal signal structure correspond one-to-one and are electrically connected. The signal collection patch and the resistor are electrically connected to the internal signal interface through a data line.

[0013] As a further feature of the present invention, the visual pressure chamber is a cylindrical structure with one end closed and the other end open. The closed end of the visual pressure chamber is coaxially provided with a connection port, which is used to set a loading rod. The open end of the visual pressure chamber is detachably and fixedly connected to the pressure chamber base.

[0014] As a further feature of the present invention, the observation window includes a light-transmitting hole disposed on the side wall of the visualization pressure chamber, and a zinc selenide optical window is disposed at the observation port, wherein the outer surface of the zinc selenide optical window is vacuum-plated with a gold film.

[0015] As a further feature of the present invention, the surface of the multiphase transparent rock and soil sample is uniformly sprayed with titanium dioxide reflective particles.

[0016] As a further feature of the present invention, the digital image association system includes a high-speed camera, which is located at 0° and 120° azimuths of the multiphase transparent soil and rock sample, respectively, with the lens of the high-speed camera facing the observation window.

[0017] The beneficial effects of this invention are: 1. This invention provides a method for preparing multiphase transparent rock and soil samples, which can prepare transparent samples of rock and soil. When conducting triaxial tests on rock and soil, the damage on the surface and inside of the rock sample can be observed more intuitively. Compared with the traditional inversion analysis that relies on damage profiles, this method makes the study more accurate.

[0018] 2. This invention provides a visualization joint testing system that utilizes a visualization pressure chamber to directly observe the deformation process of rock samples. In addition, through external observation and internal data transmission, more comprehensive physical field data collection can be achieved. Furthermore, by making the sample transparent, the initiation and penetration process of microcracks inside the sample can be observed. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating the preparation process of the transparent rock matrix module in this embodiment; Figure 2 This is a flowchart illustrating the fabrication process of the transparent skeleton structure module in this embodiment; Figure 3 This is a front view of the multiphase transparent soil and rock sample in this embodiment; Figure 4 This is a schematic diagram of the structure of the visual joint testing system in this embodiment; Figure 5 This is a schematic diagram of the pressure chamber base structure in this embodiment; In the figure, 1. Multiphase transparent rock and soil sample, 11. Transparent rock matrix module, 12. Transparent skeleton structure module, 2. Visual pressure chamber, 21. Observation window, 3. Pressure chamber base, 31. Internal signal interface, 32. External signal interface, 4. Acoustic emission signal processing equipment, 5. Digital image correlation system, 6. Infrared camera observation system, 7. Resistance signal processing equipment, 8. Signal collection patch, 9. Loading rod, 10. Display terminal. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] A method for preparing multiphase transparent soil and rock samples, referenced Figure 1 and Figure 2 It includes the following steps, S1. First, fused silica sand and transparent glass sand are mixed in a 1:1 mass ratio and then placed in a template after plasma cleaning. Microgrooves are etched on the surface of the template to improve the roughness of the transparent skeleton. After being poured into the mold, it is immediately transferred to a -20℃ gradient freezing system and cooled to the target temperature in stages at a rate of 5℃ / h. The temperature is maintained for 24 hours to allow the transparent skeleton structure to fully solidify, forming a transparent skeleton structure module.

[0023] S2 involves deep impurity removal from amorphous silica formed after melting natural silica. This is achieved through axial adsorption with activated carbon rods and circumferential adsorption with alumina, resulting in an impurity removal rate exceeding 99.5%. The melt is then subjected to ultrasonic-enhanced acid washing (8% HCl, 40℃, 28kHz / 36h) to dissolve residual metal oxides, followed by plasma washing. Finally, amorphous silica and epoxy resin are mixed at a mass ratio of at least 2.5:1 to form a transparent rock-based matrix module.

[0024] S3, pour the transparent rock matrix formed in step S2 into a cylindrical sample shaping mold with a diameter of 50 mm and a height of 100 mm; the poured transparent rock matrix occupies 80% of the total volume of the cylindrical sample shaping mold, and then fill the cylindrical sample shaping mold with the transparent skeleton structure module formed in step S1; place the mold on the vibration table and turn on the vibration table to make the transparent rock matrix module and the transparent skeleton structure mix evenly.

[0025] S4. Demold the well-mixed sample and allow it to cool naturally at room temperature for at least 24 hours.

[0026] S5. Clean the surface of the sample obtained in step S4 with anhydrous ethanol to ensure that there is no oil or dust. Place the cleaned sample in a drying oven and dry it for more than 4 hours to obtain a multiphase transparent rock and soil sample.

[0027] The above method can be used to make transparent samples of soil and rock. The material ratio can be adjusted to suit different rock properties.

[0028] A visual joint testing system, reference Figures 3 to 5 The sample includes a multiphase transparent rock and soil sample 1 prepared by the above method, a pressure chamber base 3, a visualization pressure chamber 2, and a data acquisition device and display terminal 10. The pressure chamber base 3 is fixedly connected to the visualization pressure chamber 2, forming a sealed test space inside. The multiphase transparent soil and rock sample 1 is placed in the test space and fixedly placed in the center of the pressure chamber base 3. The pressure chamber base 3 is a cylindrical stepped structure including a first step and a second step. The diameter of the first step is larger than the diameter of the second step and the first step is located at the bottom. An external signal interface 32 is provided on the side of the first step outside the test space, and an internal signal interface 31 is provided on the side of the second step inside the test space. A data transmission line is provided inside the pressure chamber base 3 to electrically connect the external signal interface 32 and the internal signal interface 31 to each other. The visualization pressure chamber 2 is made of polymethyl methacrylate (PMMA) casting. PMMA has excellent light transmittance, allowing more than 92% of sunlight to pass through. Simultaneously, the PMMA casting of the visualization triaxial pressure chamber can withstand a pressure of 100 MPa, meeting the requirements of high confining pressure tests. The visualization pressure chamber 2 has a cylindrical structure with one closed end and one open end. The closed end of the visualization pressure chamber 2 has a coaxial connection port for mounting a loading rod 9. The loading rod 9 is used to apply pressure to the multiphase transparent soil sample 1. The open end of the visualization pressure chamber 2 is detachably and fixedly connected to the pressure chamber base 3. In this embodiment, the specific fixing method is bolt fixing; other connection methods can be used in other embodiments as long as the same technical effect is achieved. The side wall of the visualization pressure chamber 2 is provided with three observation windows 21. Each observation window 21 includes a light-transmitting hole with a diameter of 30 mm. A zinc selenide optical window is embedded in the light-transmitting hole, and the outer surface of the window is vacuum-plated with a gold film (200 nm thick) to improve the long-wave infrared emissivity to 0.95. Of the three observation windows 21, two are used for observation by the digital image association system 5, and one observation window 21 is used for observation by the infrared camera observation system 6.

[0029] The specific data acquisition equipment is as follows: Six positioning points are marked around the periphery of the multiphase transparent soil and rock sample 1. A signal collection patch 8 is set at each positioning point. The signal collection patch 8 specifically includes a nano-ferrite magnetic sheet (5 mm in diameter and 0.2 mm in thickness) pasted on the positioning point and an acoustic emission signal sensor adsorbed to the center of the nano-ferrite magnetic sheet by a neodymium magnet. The acoustic emission signal sensor pasted around the multiphase transparent soil and rock sample 1 is connected to the internal signal interface 31 of the sample base by a wire. Then, the acoustic emission signal processing device 4 is connected to the corresponding external signal interface 32 of the internal signal interface 31 by a wire. The acoustic emission signal processing device 4 is then connected to the display terminal 10 by a wire.

[0030] Titanium dioxide reflective microparticles (TiO2 particle size 5μm, coating thickness ≤10μm) are uniformly sprayed onto the surface of the multiphase transparent soil sample 1 to enhance the contrast of surface feature points and improve displacement recognition accuracy. The digital image association system 5 includes a high-speed camera. Image acquisition adopts a multi-view synchronous triggering system, using a high-speed camera with a main viewing angle of 0° and a secondary viewing angle of 120° to simultaneously capture the deformation of the multiphase transparent soil sample 1. The high-speed camera is connected to the display terminal 10 via wires.

[0031] The infrared camera observation system 6 includes an infrared thermal imager installed outside the visualization pressure chamber 2. The infrared thermal imager is fixed at a 30° angle at a distance of about 50 mm from the observation window 211. It collects thermal radiation signals through a chalcogenide glass lens and simultaneously uses a built-in laser ranging module to compensate for changes in the object distance caused by sample deformation in real time.

[0032] Three resistors are equidistantly attached to the circumferential surface of the multiphase transparent soil sample 1. The resistors are connected to the internal signal interface 31 by wires. Then, the resistor signal processing device 7 is connected to the corresponding external signal interface 32 of the internal signal interface 31 by wires. The resistor signal processing device 7 is then connected to the display terminal 10 by wires.

[0033] The internal signal interface 31 is connected to the external signal interface 32 through the wiring inside the pressure chamber base, and then connected to the display terminal 10 through the external data line.

[0034] During operation, the triaxial compression test process is initiated and the stress-strain data and multi-physics field joint observation data of the multiphase transparent rock and soil are recorded in real time. The visualization joint testing system integrates four-dimensional physical field monitoring methods, including acoustic (acoustic emission monitoring), optical (digital image correlation technology), thermal (infrared thermal imaging), and electrical (resistivity sensing), to achieve synchronous acquisition and joint analysis of multiple parameters of the target sample.

[0035] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing multiphase transparent rock and soil samples, characterized in that, Includes the following steps, S1, First, fused silica sand and transparent glass sand are mixed in a predetermined mass ratio, and after plasma cleaning, they are placed in a mold. After being poured into the mold, they are immediately transferred to a gradient freezing system to cool down to the target temperature in stages, and kept warm until the transparent skeleton structure is fully solidified to form a transparent skeleton structure module. S2 involves deep impurity removal from amorphous silica formed by melting natural silica. The melt is then subjected to ultrasonic-enhanced acid washing to dissolve residual metal oxides, followed by plasma water washing and mixing with epoxy resin solution to form a transparent rock matrix module. S3, pour the transparent rock matrix module formed in step S2 into the sample shaping mold, then fill the transparent skeleton structure module formed in step S1 into the sample shaping mold, and vibrate the mold to make the transparent rock matrix module and transparent skeleton structure mix evenly. S4, demold the sample molding mold and allow the obtained sample to cool naturally at room temperature; S5. Clean the surface of the sample obtained in step S4 with anhydrous ethanol, and dry the cleaned sample in a drying oven to obtain a multiphase transparent rock and soil sample.

2. The method for preparing a multiphase transparent rock and soil sample according to claim 1, characterized in that, In step S1, the mass ratio of molten silica sand to transparent glass is 1:1; the gradient freezing system cools the glass in stages to -20°C at a rate of 5°C / h.

3. The method for preparing a multiphase transparent rock and soil sample according to claim 1, characterized in that, In step S2, the mass ratio of the amorphous silica to the epoxy resin is not less than 2.5:

1.

4. The method for preparing a multiphase transparent rock and soil sample according to claim 1, characterized in that, In step S2, the deep impurity removal method is to achieve a removal rate of more than 99.5% for amorphous silica impurities through axial adsorption of activated carbon rods and circumferential adsorption of alumina.

5. A visual joint testing system, characterized in that, The test includes a multiphase transparent soil sample (1) prepared using any one of the multiphase transparent soil sample preparation methods described in claims 1-4, a pressure chamber base (3), a visualization pressure chamber (2), an acoustic emission signal processing device (4), a digital image correlation system (5), an infrared camera observation system (6), a resistance signal processing device (7), and a display terminal (10). The visualization pressure chamber (2) is fixedly connected to the pressure chamber base (3) to form a sealed test space. The multiphase transparent soil sample (1) is placed in the test space and fixedly placed in the center of the pressure chamber base (3). The side wall of the sample is provided with several observation windows (21). The digital image association system (5) and the infrared camera observation system (6) observe the multiphase transparent rock and soil sample (1) through the observation windows (21). The multiphase transparent rock and soil sample (1) is provided with a signal collection patch (8) and a resistor. The signal collection patch (8) and the resistor are respectively connected to the acoustic emission signal processing device (4) and the resistance signal processing device (7). The acoustic emission signal processing device (4), the digital image association system (5), the infrared camera observation system (6) and the resistance signal processing device (7) are all electrically connected to the display terminal (10).

6. The visual joint testing system according to claim 5, characterized in that, The pressure chamber base (3) is a cylindrical stepped structure and includes a first step and a second step. The first step is provided with an external signal interface (32) on the side wall outside the test space, and the second step is provided with an internal signal interface (31) on the side wall inside the test space. The external signal interface (32) and the internal signal structure correspond one-to-one and are electrically connected. The signal collection patch (8) and the resistor are electrically connected to the internal signal interface (31) through a data line.

7. The visual joint testing system according to claim 6, characterized in that, The visual pressure chamber (2) is a cylindrical structure with one end closed and the other end open. The closed end of the visual pressure chamber (2) is coaxially provided with a connection port, which is used to set a loading rod (9). The open end of the visual pressure chamber (2) is detachably and fixedly connected to the pressure chamber base (3).

8. The visual joint testing system according to claim 5, characterized in that, The observation window (21) includes a light-transmitting hole set on the side wall of the visualization pressure chamber (2), and a zinc selenide optical window is provided at the light-transmitting hole. The outer surface of the zinc selenide optical window is vacuum-plated with a gold film.

9. A visual joint testing system according to claim 5, characterized in that, The surface of the multiphase transparent rock and soil sample (1) is uniformly coated with titanium dioxide reflective particles.

10. A visual joint testing system according to claim 5, characterized in that, The digital image association system (5) includes a high-speed camera, which is located at 0° and 120° on the multiphase transparent rock and soil sample (1), respectively, and the lens of the high-speed camera is facing the observation window (21).

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