Device and testing method for fracture deformation-seepage cross-scale visualization experiment

Abstract

The invention provides a fracture deformation-seepage cross-scale visualization experiment device and a test method, and relates to the technical field of hydraulic rock mechanics and measurement. Comprising a macroscopic observation assembly, a microscopic observation assembly, a microscopic seepage model, a temperature-stress-seepage loading system, a monochromatic coaxial light source and a data acquisition and analysis system, the microscopic seepage model is used for placing a fractured rock mass; the temperature-stress-seepage loading system is used for injecting fluid with fluorescent microspheres into the microcosmic seepage model, applying load, regulating and controlling temperature and collecting data; the data acquisition and analysis system is used for processing data and images. By arranging the macroscopic observation assembly and the microcosmic observation assembly, double-scale synchronous observation is achieved, the whole process of fracture internal fluid interface evolution and rock mass deformation can be obtained in real time under the multi-physics field coupling conditions of temperature, stress, seepage and the like, visual correlation of deformation, flow and stress is achieved, and the measurement accuracy is improved. And an experimental basis is provided for establishing a fracture multi-field coupling mechanism model.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic rock mechanics and measurement, in particular to a device and a testing method for fracture deformation-seepage cross-scale visualization experiment. BACKGROUND

[0002] Fracture deformation-multiphase seepage process and its coupling mechanism are the core problems in the fields of carbon dioxide geological storage, geothermal resource development, high-level radioactive nuclear waste disposal, etc. The key lies in how the micro process between rock mass deformation and multiphase fluid in fractures under the action of stress and seepage controls the evolution of its macro characteristics.

[0003] At present, the experiments for testing the coupling characteristics of fracture deformation-seepage mainly focus on the rock mass scale, that is, the standard rock sample (φ50 × h100 mm) is broken under pressure and then the permeability test is carried out. The data obtained by this kind of experiment only reflect the macro statistical characteristics, which belongs to black box test and it is difficult to reveal the real-time coupling mechanism of fluid flow and deformation in fractures. Although acoustic emission (AE) technology can reflect the fracture behavior by monitoring the acoustic signals when the crack is formed, it cannot obtain the coupling relationship between fluid flow state and stress-seepage. Although X-ray CT scanning and nuclear magnetic resonance (MRI) technology can be used for internal structure reconstruction, their time resolution is usually in seconds and spatial resolution is in tens of microns, which makes it difficult to realize real-time observation of the interface between multiphase fluid seepage and chemical reaction.

[0004] Optical imaging technology has the advantages of high time and space resolution and has been widely used in biomechanics and material science. In recent years, this method has been introduced into the field of rock mechanics to observe crack evolution, but there is still a lack of systematic device that can realize micro and macro imaging in the processes of deformation, seepage and chemical reaction. Therefore, developing an experimental platform that can realize cross-scale visualization observation of fracture deformation-seepage process under complex stratum conditions is a key technical problem to be solved at present. SUMMARY

[0005] The purpose of the present application is to provide a device and a testing method for fracture deformation-seepage cross-scale visualization experiment, which can solve the problems raised in the background art.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows: A device for fracture rock mass deformation-seepage cross-scale visualization experiment, comprising a macro observation assembly, a micro observation assembly, a micro seepage model, a temperature-stress-seepage loading system, a monochromatic coaxial light source and a data acquisition and analysis system. The micro seepage model is used to place the fractured rock mass. The temperature-stress-seepage loading system is used for placing the micro seepage model, injecting the fluid with fluorescent microspheres into the micro seepage model, applying the load, regulating the temperature and collecting the data. The monochromatic coaxial light source is used for providing the bright field for the fractured rock mass; the micro observation assembly is used for collecting the image of the local area of the fractured rock mass; and the macro observation assembly is used for collecting the image of the overall deformation and seepage of the fractured rock mass. The data collection and analysis system is used for controlling the micro observation assembly, the macro observation assembly, the temperature-stress-seepage loading system and analyzing the data collected by the temperature-stress-seepage loading system and the images collected by the micro observation assembly and the macro observation assembly.

[0007] Further, the micro observation assembly comprises a first camera, an optical sleeve, a fluorescent filter module and a complex apochromatic microscope objective, the first camera is connected with the fluorescent filter module through the optical sleeve, and the fluorescent filter module is connected with the complex apochromatic microscope objective.

[0008] Further, the micro seepage model comprises two pieces of transparent bottom flexible plates arranged oppositely, two pieces of side flexible plates arranged oppositely and two pieces of one-way seepage capillary plates arranged oppositely, the transparent bottom flexible plates, the side flexible plates and the one-way seepage capillary plates are bonded and sealed with each other, and the micro seepage model is internally provided with a first cavity for placing the fractured rock mass. The one-way seepage capillary plate is provided with capillary holes in communication with the first cavity.

[0009] Further, the temperature-stress-seepage loading system comprises a temperature loading device, a stress loading device, a seepage loading device, a loading platform and a three-axis electric translation stage, the loading platform is fixedly placed on the three-axis electric translation stage through a two-way locking valve, and the three-axis electric translation stage is used for adjusting the position of the loading platform; the loading platform is internally provided with a second cavity for placing the micro seepage model, the temperature loading device is used for regulating the temperature of the second cavity, the stress loading device is used for applying the load to the micro seepage model, and the seepage loading device is used for injecting the fluid with fluorescent microspheres into the micro seepage model.

[0010] Further, the temperature loading device comprises a low-temperature controller, a high-temperature controller and a temperature sensor, and the low-temperature controller and the high-temperature controller are both connected with the second cavity through heat conduction pipes.

[0011] Further, the seepage loading device comprises an injection device, an injection pipeline, an outflow pipeline and a first pressure sensor, the injection device is connected with the second cavity through the injection pipeline, one end of the outflow pipeline is connected with the second cavity, and the other end of the outflow pipeline extends from the inside of the loading platform to the outside of the loading platform. The first pressure sensor is used for detecting the seepage pressure in the micro seepage model.

[0012] Further, the loading platform comprises a shell, the shell is hollow, and the top surface and the bottom surface of the shell are symmetrically provided with openings, and sapphire windows are sealingly arranged in the openings. The shell is provided with two side walls of the second cavity, and the two side walls are oppositely and spacedly arranged.

[0013] Further, the stress loading device comprises a pressure controller, a displacement controller, a rigid mechanical bearing end, a servo mechanical bearing, a second pressure sensor and a displacement sensor, the rigid mechanical bearing end is located in the loading platform and connected with the shell through the servo mechanical bearing, and the rigid mechanical bearing end is slidingly connected with the inner wall of the shell. The pressure controller and the displacement controller are connected with the servo mechanical bearing through a control circuit. The displacement sensor is used for detecting the displacement of the rigid mechanical bearing end, and the second pressure sensor is used for detecting the pressure value of the micro seepage model received by the rigid mechanical bearing end.

[0014] Further, the macroscopic observation assembly comprises a second camera and a zoom lens, and the zoom lens is connected with the second camera.

[0015] A crack deformation-seepage cross-scale visualized experimental testing method, comprising the following steps: S1. configuring a seepage fluid, assembling and debugging a crack rock mass deformation-seepage cross-scale visualized testing device; S2. placing the crack rock mass in the micro seepage model, then mounting the micro seepage model in the second cavity, starting the pressure loading device to simulate the underground stress state; S3. starting the seepage loading device, establishing a stable one-way seepage path and testing the system sealing property and fluid communication property; S4. adjusting the temperature field through the temperature loading device; S5. turning on the monochromatic coaxial light source, starting the macroscopic observation assembly and the micro observation assembly to collect images, and starting the pressure loading device to apply axial load to the micro seepage model; S6. the data acquisition and analysis system processes the collected images and collected pressure data and displacement data to obtain a stress nephogram of a local flow field.

[0016] The present application has at least the following advantages or beneficial effects: 1. The present application realizes the synchronous optical observation of the micro-macro cross-scale seepage and chemical reaction process under the action of heat and force. The present application integrates the micro observation assembly and the macro observation assembly to realize double-scale synchronous observation, can obtain the whole process of the fluid interface evolution in the crack and the rock mass deformation in real time under the coupling conditions of temperature, stress and seepage, and realizes the cross-scale and cross-physical field synchronous visualization which cannot be simultaneously considered in the prior art.

[0017] 2. Synchronous acquisition of double-scale images, which can directly output deformation-flow-stress coupling atlas. Through joint analysis of digital image correlation (DIC) and particle image velocimetry (PIV) on image sequences obtained by the first camera and the second camera, the deformation field, the flow velocity field and the stress distribution of the rock mass can be synchronously acquired, the visualization correlation of deformation, flow and stress is realized, and experimental basis for establishing a crack multi-field coupling mechanism model is provided. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0019] Figure 1 The device structure diagram of the crack deformation-seepage cross-scale visualization experiment provided by the present application is shown in the figure. Figure 2 The internal structure diagram of the loading platform provided by the present application is shown in the figure. Figure 3 The double-scale imaging optical path diagram is shown in the figure. Figure 4 The structure diagram of the micro seepage model provided by the present application is shown in the figure.

[0020] Figure: 100, air floating shock isolation platform; 101, vertical optical support; 110, macroscopic observation assembly; 111, second camera; 113, zoom lens; 200, microscopic observation assembly; 201, first camera; 203, optical sleeve; 205, fluorescence filter module; 207, apochromatic microscope objective; 209, lens mounting frame; 300, micro seepage model; 301, fractured rock mass; 303, transparent bottom flexible plate; 305, side flexible plate; 307, one-way seepage capillary plate; 309, capillary hole; 400, monochromatic coaxial light source; 500, data acquisition and analysis system; 601, low-temperature controller; 603, high-temperature controller; 605, low-temperature resistant liquid nitrogen heat pipe; 607, high-temperature resistant metal heat pipe; 701, pressure controller; 703, displacement controller; 705, rigid mechanical bearing end; 707, servo mechanical bearing; 801, injection device; 803, injection pipeline; 805, outflow pipeline; 807, first pressure sensor; 900, loading platform; 901, shell; 902, three-axis electric translation stage; 903, sapphire window; 904, two-way locking valve; 905, side wall; 906, wastewater collection device; 907, second cavity. DETAILED DESCRIPTION

[0021] So that the purposes, technical solutions and advantages of the embodiments of the present application are more apparent, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0022] Please refer to Figures 1 to 4 The device for the deformation-seepage cross-scale visualization test of fractured rock mass shown in the figure includes a macroscopic observation assembly 110, a microscopic observation assembly 200, a microscopic seepage model 300, a temperature-stress-seepage loading system, a monochromatic coaxial light source 400 and a data acquisition and analysis system 500. The present embodiment further includes an air-floating vibration isolation platform 100 and a vertical optical support 101 installed on the air-floating vibration isolation platform 100. The microscopic seepage model 300, part of the temperature-stress-seepage loading system, the monochromatic coaxial light source 400 and the macroscopic observation assembly 110 are sequentially installed along the vertical optical support 101 in the height direction from top to bottom, and a spacing is provided between the above-mentioned parts. Part of the temperature-stress-seepage loading system is arranged on the air-floating vibration isolation platform 100. The microscopic seepage model 300 is used to place a fractured rock mass 301, and the microscopic seepage model 300 is placed in the temperature-stress-seepage loading system. The temperature-stress-seepage loading system injects fluid with fluorescent microspheres into the microscopic seepage model 300, applies a load, controls the temperature and acquires data. The light beam emitted by the monochromatic coaxial light source 400 can pass through the temperature-stress-seepage loading system and the microscopic seepage model 300 to irradiate on the fractured rock mass. The fractures of the fractured rock mass penetrate through the rock mass, and part of the light beam can excite the fluid fluorescence through the gap. The excited fluid fluorescence can pass through the microscopic seepage model 300 and the temperature-stress-seepage loading system to be collected by the upper microscopic observation device, and the reflected light beam is collected by the lower macroscopic observation device.

[0023] The microscopic observation assembly 200 is used to collect the image of the local area of the fractured rock mass 301, which is collected by the fluorescence emitted by the fluorescent microspheres. The macroscopic observation assembly 110 is used to collect the deformation and seepage image of the whole fractured rock mass 301, which is collected by the light reflected by the fractured rock mass 301 from the monochromatic coaxial light source 400.

[0024] The data acquisition and analysis system 500 is arranged on the vertical optical support 101, and the macroscopic observation assembly 110, the microscopic observation assembly 200, the temperature-stress-seepage loading system and the monochromatic coaxial light source 400 are electrically connected with the data acquisition and analysis system 500. The data acquisition and analysis system 500 is used for controlling the microscopic observation assembly 200, the macroscopic observation assembly 110 and the temperature-stress-seepage loading system and analyzing and processing the data collected by the temperature-stress-seepage loading system and the images collected by the microscopic observation assembly 200 and the macroscopic observation assembly 110.

[0025] The macroscopic observation assembly 110 and the microscopic observation assembly 200 are arranged, and double-scale synchronous observation is realized on the air floating isolation platform 100, the full process of fluid interface evolution in a fracture and rock mass deformation can be obtained in real time under the condition of coupling of multiple physical fields such as temperature, stress and seepage, and cross-scale and cross-physical field synchronous visualization that cannot be simultaneously considered in the prior art is realized.

[0026] Specifically, the microscopic observation assembly 200 comprises a first camera 201, an optical sleeve 203, a fluorescent filter module 205 and a complex achromatic microscope objective 207. The first camera 201 is a high-quantum-efficiency scientific research camera, which is arranged on the top of the vertical optical support 101. The first camera 201 is connected with the fluorescent filter module 205 through the optical sleeve 203, and the fluorescent filter module 205 is connected with the complex achromatic microscope objective 207. Preferably, a lens mounting frame 209 is further arranged on the vertical optical support 101, the complex achromatic microscope objective 207 penetrates through the lens mounting frame 209 and is fixedly connected with the lens mounting frame 209, and the lens mounting frame 209 can fix the complex achromatic microscope objective 207, so that the complex achromatic microscope objective 207 is prevented from being deviated due to its own weight. The light passing through the fracture excites fluid fluorescence, the excited fluorescence enters the first camera 201 through the high-power complex achromatic microscope objective 207 and the fluorescent filter module 205, and high-resolution imaging of the fluid is realized.

[0027] Please refer to Figure 1 and Figure 2 The temperature-stress-seepage loading system comprises a temperature loading device, a stress loading device, a seepage loading device, a loading platform 900 and a three-axis electric translation stage 902.

[0028] The loading platform 900 comprises a shell 901, and the shell 901 is hollow. Openings are symmetrically arranged on the top surface and the bottom surface of the shell 901, and sapphire windows 903 are sealingly arranged in the openings. Side walls 905 are arranged in the shell 901, and the two side walls 905 are oppositely and spacedly arranged. The two sapphire windows 903 and the two side walls 905 jointly form a second cavity 907 with two notches in the shell 901, and the second cavity 907 is used for placing the microscopic seepage model 300.

[0029] The loading platform 900 is fixed on the three-axis electric translation stage 902 through the bidirectional locking valve 904. The three-axis electric translation stage is arranged on the vertical optical support 101, and the three-axis electric translation stage can realize micron-level movement of the loading platform 900 in the horizontal direction and the vertical direction.

[0030] The temperature loading device is used for regulating the temperature in the second cavity 907 to realize dynamic balance. The temperature loading device comprises a low-temperature controller 601, a high-temperature controller 603 and a temperature sensor. The low-temperature controller 601 is a liquid nitrogen low-temperature controller, which is connected with a joint port on the shell through a controller connection cable. The joint port can be an electromagnetic valve, which is externally connected with a liquid nitrogen storage device. The joint port is connected with the second cavity 907 through a low-temperature-resistant liquid nitrogen heat conduction pipe 605. The high-temperature controller 603 is an electric heating high-temperature controller, which is connected with the joint port through a controller connection cable. The joint port is externally connected with an electric heating device, and is connected with the second cavity 907 through a high-temperature-resistant metal heat conduction pipe 607. The temperature sensor is arranged inside the second cavity 907, and is electrically connected with the data acquisition and analysis system 500. The temperature sensor can collect the temperature inside the second cavity 907 in real time and transmit the temperature to the data acquisition and analysis system 500, so that the data acquisition and analysis system 500 controls the temperature loading device, and then regulates the temperature inside the second cavity 907 to provide a constant-temperature environment for the micro seepage model 300.

[0031] Further, the seepage loading device comprises an injection device 801, an injection pipeline 803, an outflow pipeline 805 and a first pressure sensor 807. The injection device 801 is a precision injection pump and a micro-sampler, which are connected through a pipeline. The injection device 801 is connected with the second cavity 907 through the injection pipeline 803 (a high-pressure-resistant capillary tube), and one end of the outflow pipeline 805 (a high-pressure-resistant capillary tube) is connected with the second cavity 907. The other end of the outflow pipeline 805 extends from the inside of the loading platform 900 to the outside of the loading platform 900, and is externally connected with a wastewater collection device 906, such as a beaker. The first pressure sensor 807 is installed on the pipeline between the precision injection pump and the micro-sampler, and is electrically connected with the data acquisition and analysis system 500, and is used for monitoring the seepage driving pressure. When the micro seepage model 300 is installed in place in the second cavity 907, the injection pipeline 803 and the outflow pipeline 805 are both connected with the micro seepage model 300. The injection device 801 can input the fluid of the fluorescent microspheres into the micro seepage model 300, and the fluid flows out through the outflow pipeline 805.

[0032] Further, the stress loading device comprises a pressure controller 701, a displacement controller 703, a rigid mechanical bearing end 705, a servo mechanical bearing 707, a second pressure sensor and a displacement sensor.

[0033] The pressure controller 701 and the displacement controller 703 are installed on the air floating isolation platform 100, and the pressure controller 701 and the displacement controller 703 are connected with the servo-mechanical bearing 707 through a control line, and the pressure controller 701 and the displacement controller 703 are used for controlling the servo-mechanical bearing 707 to start and stop. The rigid mechanical bearing end 705 is located in the loading platform 900, and is connected with the shell 901 through the servo-mechanical bearing 707. When the servo-mechanical bearing 707 works, the rigid mechanical bearing end 705 can move along the length direction of the servo-mechanical bearing 707, and is in sliding connection with the inner wall of the shell 901. The rigid mechanical bearing end 705 is in T-shaped structure, and two symmetrically arranged. The second cavity 907 is located between the two rigid mechanical bearing ends 705, and the end portions of the two rigid mechanical bearing ends 705 extend into the second cavity 907 through two notches of the second cavity 907, and are in sealed sliding connection with the side wall 905 and the sapphire window 903, and together form the sealed second cavity 907. When the two rigid mechanical bearing ends 705 are close to each other, the micro seepage model 300 installed in the second cavity 907 can be abutted and pressed.

[0034] The displacement sensor is arranged between the port of the displacement controller 703 and the servo-mechanical bearing 707, and is used for measuring the displacement of the rock mass compression and the rigid mechanical bearing end in real time. The second pressure sensor is arranged on the inner cavity wall of the second cavity 907 in contact with the micro seepage model 300, and is used for detecting the pressure value of the micro seepage model 300 subjected to the rigid mechanical bearing end.

[0035] Please refer to Figure 4The micro seepage model 300 includes two pieces of transparent bottom flexible plate 303 arranged oppositely, two pieces of side flexible plate 305 arranged oppositely, and two pieces of one-way seepage capillary plate 307 arranged oppositely. The transparent bottom flexible plate 303, the side flexible plate 305, and the one-way seepage capillary plate 307 are bonded to each other and sealed by viscous encapsulation glue. The micro seepage model 300 is internally provided with a first cavity for placing the fractured rock mass 301. The transparent bottom flexible plate 303 can realize that the light emitted by the monochromatic coaxial light source 400 irradiates the fractured rock mass 301 and the light passing through the fracture is captured by the micro observation assembly 200. The one-way seepage capillary plate 307 is provided with a capillary hole 309 in communication with the first cavity. The capillary hole 309 on one of the one-way seepage capillary plates 307 is connected with the output end of the injection pipeline 803. The one-way seepage capillary plate 307 adopts a porous ceramic structure, the pore diameter is designed to be smaller than the oil phase breakthrough radius, and the water phase can enter in one direction and the oil phase is blocked by the interfacial tension under the joint action of the capillary force and the micro positive pressure maintained by the syringe pump; the outlet end of the one-way seepage capillary plate 307 allows the oil-water mixed phase to flow out, but also prevents external fluid from entering in reverse due to the pore diameter and pressure difference, thereby forming stable one-way flow. Correspondingly, the capillary hole 309 of the other one-way seepage capillary plate 307 is connected with the outflow pipeline 805. The one-way seepage capillary plate 307 allows the water phase and the oil phase to enter the outflow pipeline 805 from the fracture, and the water phase and the oil phase cannot enter the seepage into the rock fracture from the outflow pipeline 805 in reverse. The outflow pipeline 805 is provided with an electromagnetic valve for controlling the on-off of the fluid in the outflow pipeline 805.

[0036] Please refer again to Figure 1 The macro observation assembly 110 includes a second camera 111 and a zoom lens 113 connected with the second camera 111. The second camera 111 is a high-speed high-resolution scientific research camera, and the zoom lens 113 is a variable focal length working distance lens. The light reflected by the fractured rock mass 301 passes through the zoom lens 113 and enters the second camera 111, so that the DIC (differential interference contrast imaging) of the deformation of the fractured rock mass 301 and the observation of the macro flow characteristics of the multiphase fluid in the fracture can be realized.

[0037] The data acquisition and analysis system 500 is divided into hardware and software two parts. The hardware includes a high-performance workstation (Dell Precision 5820), an image monitor, an electrical cable, etc. The software includes an image acquisition code developed based on Python, an open source PIVLab software library for processing particle velocity field measurement, and an open source PyDIC software library for processing rock mass deformation field.

[0038] A fractured deformation-seepage cross-scale visualization experimental testing method, comprising the following steps: S1. Configuration of seepage fluid, disperse fluorescent tracer microspheres with a diameter of about 10 μm in deionized water at a set concentration, stir uniformly and stand for degassing, if necessary, remove air bubbles under vacuum conditions, then inject the solution into the micro-injection device for standby, to obtain the visualization seepage tracer fluid.

[0039] Assemble and debug the fracture rock mass deformation-seepage cross-scale visualization test device, start the control system and check the working state and communication connectivity of each unit (loading, temperature control, optical imaging, data acquisition).

[0040] S2. Place the fractured rock mass in the microseepage model, then install the microseepage model in the second cavity, ensure that the capillary pores on the two one-way seepage capillary plates are respectively sealed and connected with the corresponding injection pipeline or outflow pipeline; start the pressure loading device, make the rigid mechanical bearing end 705 contact the model surface at a speed of 0.02 mm / s by displacement control mode, switch to stress control mode when the initial stress signal is detected, maintain the loading stress at about 0.2 MPa and the target formation confining pressure, to simulate the underground stress state.

[0041] In this step, the specific rock is polished into a rock piece with a length of 40 mm, a width of 40 mm and a thickness of 5 mm, a CO2 laser etching is used to form a preset fracture morphology, and the fracture needs to penetrate the rock mass. Then, the rock piece and the one-way seepage capillary plate, the transparent bottom flexible plate and the side flexible plate are sequentially cleaned with ethanol and acetone, and are bonded and packaged into a sealed seepage model after plasma cleaning treatment, to ensure that the fracture channel is continuous and the inlet and outlet directions are consistent.

[0042] S3. Start the seepage loading device, inject the fluorescent tracer fluid into the fracture model inlet, establish a stable one-way seepage path and test the system sealing and fluid connectivity; S4. Adjust the temperature field by the temperature loading device; use the electric heating high-temperature controller and the liquid nitrogen low-temperature controller to jointly regulate the temperature field, to heat up to the target temperature at a rate of about 0.2 ℃ / min and maintain the temperature for 30 min, to ensure that the rock sample and the seepage fluid reach thermodynamic equilibrium.

[0043] S5. Turn on the monochrome coaxial light source, start the macroscopic observation assembly and the microscopic observation assembly, adjust the focal length, observation area (RoI) and frame rate of the first camera and the second camera, to realize real-time imaging of fracture deformation and seepage. Start the pressure loading device to apply axial load to the microseepage model; in the displacement control mode, apply axial load at a rate of 0.001 mm / min, while injecting seepage fluid at a flow rate of 20 μL / min. Maintain a constant pressure difference at the inlet end, and constant pressure or set back pressure at the outlet end, to form a one-way stable flow. The effluent is collected by the outflow pipeline.

[0044] Pressure and displacement sensors simultaneously acquire strain-stress and flow-pressure data from fractured rock samples. The displacement sensor monitors the displacement change at the loading end, while the first and second pressure sensors record the driving pressure difference and confining pressure, achieving temporal synchronization of mechanical and seepage signals and providing data support for subsequent curve analysis.

[0045] S6. Data acquisition and analysis system: Plot strain-stress curves based on acquired data ( σ - ε ), fluid flow-pressure curve ( Q - P By combining Darcy's law with the measured flow rate and pressure difference, and taking into account the sample size, the equivalent permeability under this stress state can be calculated. And by connecting the permeability corresponding to each strain point, we obtain the time series curve of permeability evolution of fractures during rock mass deformation. - t This allows for a direct and intuitive understanding of the dynamic changes in permeability during the deformation process; The above calculations are based on the formula:

[0046] in: The equivalent permeability of the rock sample is given. This refers to the fluid volumetric flow rate. For fluid dynamic viscosity, The length of the rock sample. The cross-sectional area of ​​the rock sample is... The pressure difference is the pressure difference between the two ends of the fluid passing through the rock sample.

[0047] Images acquired using the second camera are preprocessed to optimize image quality, and digital image correlation (DIC) and particle image velocimetry (PIV) calculations are performed to plot the deformation field cloud map of the rock mass under stress and the evolution cloud map of the flow field within the entire fracture.

[0048] Using images captured by the first camera, a two-dimensional velocity field was obtained through particle image velocimetry (PIV), and an evolution cloud map of the flow field under the influence of local fracture morphology was plotted. A digital elevation model of the fracture was calculated using digital image correlation (DIC), and a stress cloud map of the local flow field was calculated based on the Navier-Stokes equations.

[0049] The obtained images are preprocessed. The images obtained by the first camera are subjected to digital image correlation (DIC) and the images obtained by the second camera are subjected to particle image velocimetry (PIV) to generate cloud maps of rock mass deformation field and flow field evolution. Based on the two-dimensional velocity field inversion, the local stress distribution is inverted and a digital elevation model of the fracture is established to realize the coupled visualization analysis of deformation-flow-stress.

[0050] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A device for fracture deformation-percolation cross-scale visualization experiment, characterized in that, The macroscopic observation assembly, the microscopic observation assembly, the microscopic seepage model, the temperature-stress-seepage loading system, the monochromatic coaxial light source and the data acquisition and analysis system are provided. The microscopic seepage model is used for placing the fractured rock mass. The temperature-stress-seepage loading system is used for placing the microscopic seepage model, injecting the fluid with fluorescent microspheres into the microscopic seepage model, applying the load, adjusting the temperature and collecting the data. The monochromatic coaxial light source is used for providing the bright field for the fractured rock mass. The microscopic observation assembly is used for collecting the image of the local area of the fractured rock mass, and the macroscopic observation assembly is used for collecting the image of the overall deformation and seepage of the fractured rock mass. The data acquisition and analysis system is used for controlling the microscopic observation assembly, the macroscopic observation assembly, the temperature-stress-seepage loading system and analyzing the data collected by the temperature-stress-seepage loading system and the images collected by the microscopic observation assembly and the macroscopic observation assembly.

2. The device for fracture deformation-hydraulic cross-scale visualization experiment according to claim 1, characterized in that, The microscopic observation assembly comprises a first camera, an optical sleeve, a fluorescent filter module and a complex achromatic microscope objective, the first camera is connected with the fluorescent filter module through the optical sleeve, and the fluorescent filter module is connected with the complex achromatic microscope objective.

3. The apparatus for fracture deformation-hydraulic cross-scale visualization experiment according to claim 1, characterized in that, The microscopic seepage model comprises two pieces of transparent bottom flexible plates arranged oppositely, two pieces of side flexible plates arranged oppositely and two pieces of one-way seepage capillary plates arranged oppositely, the transparent bottom flexible plates, the side flexible plates and the one-way seepage capillary plates are bonded and sealed with each other, and a first cavity for placing the fractured rock mass is arranged in the microscopic seepage model. The one-way seepage capillary plate is provided with capillary holes in communication with the first cavity.

4. The apparatus for fracture deformation-hydraulic cross-scale visualization experiment according to claim 1, characterized in that, The temperature-stress-seepage loading system comprises a temperature loading device, a stress loading device, a seepage loading device, a loading platform and a three-axis electric translation stage, the loading platform is fixedly arranged on the three-axis electric translation stage through a two-way locking valve, the three-axis electric translation stage is used for adjusting the position of the loading platform, a second cavity for placing the microscopic seepage model is arranged in the loading platform, the temperature loading device is used for adjusting the temperature of the second cavity, the stress loading device is used for applying the load to the microscopic seepage model, and the seepage loading device is used for injecting the fluid with fluorescent microspheres into the microscopic seepage model.

5. The apparatus for fracture deformation-hydraulic cross-scale visualization experiment according to claim 4, characterized in that, The temperature loading device comprises a low-temperature controller, a high-temperature controller and a temperature sensor, and the low-temperature controller and the high-temperature controller are connected with the second cavity through heat conduction pipes.

6. The apparatus for fracture deformation-hydraulic cross-scale visualization experiment according to claim 4, characterized in that, The seepage loading device comprises an injection device, an injection pipeline, an outflow pipeline and a first pressure sensor, the injection device is connected with the second cavity through the injection pipeline, one end of the outflow pipeline is connected with the second cavity, and the other end of the outflow pipeline extends from the inside of the loading platform to the outside of the loading platform. The first pressure sensor is used for detecting the seepage pressure in the microscopic seepage model.

7. The apparatus for fracture deformation-hydraulic cross-scale visualization experiment according to claim 4, characterized in that, The loading platform comprises an outer shell, the outer shell is hollow, and the top surface and the bottom surface of the outer shell are symmetrically provided with openings, and sapphire windows are sealingly arranged in the openings. The housing is provided with two side walls of the second cavity, and the two side walls are oppositely and spacedly arranged.

8. The apparatus for fracture deformation-hydraulic cross-scale visualization experiment according to claim 7, characterized in that, The stress loading device comprises a pressure controller, a displacement controller, a rigid mechanical bearing end, a servo mechanical bearing, a second pressure sensor and a displacement sensor, the rigid mechanical bearing end is located in the loading platform and connected with the housing through the servo mechanical bearing, and the rigid mechanical bearing end is in sliding connection with the inner wall of the housing; the end of the rigid mechanical bearing end is located in the second cavity and in sealed sliding connection with the side wall and the sapphire window; The pressure controller and the displacement controller are connected with the servo mechanical bearing through a control line; The displacement sensor is used for detecting the displacement of the rigid mechanical bearing end, and the second pressure sensor is used for detecting the pressure value of the micro seepage model subjected to the rigid mechanical bearing end.

9. The apparatus for fracture deformation-hydraulic cross-scale visualization experiment according to claim 3, characterized in that, The macroscopic observation assembly comprises a second camera and a zoom lens, and the zoom lens is connected with the second camera.

10. A fracture deformation-seepage cross-scale visualization experimental test method, based on the device of fracture deformation-seepage cross-scale visualization experiment of any one of claims 1-9, characterized in that, The method comprises the following steps: S1. configuring seepage fluid, assembling and debugging the fracture rock mass deformation-seepage cross-scale visualization test device; S2. placing the fracture rock mass in the micro seepage model, and then installing the micro seepage model in the second cavity; Starting the pressure loading device to simulate the underground stress state; S3. starting the seepage loading device, establishing a stable one-way seepage path and checking the system sealing property and fluid communication property; S4. adjusting the temperature field through the temperature loading device; S5. opening the monochrome coaxial light source, starting the macroscopic observation assembly and the microcosmic observation assembly to collect images, and starting the pressure loading device to apply axial load to the micro seepage model; S6. the data acquisition and analysis system processes the collected images and collected pressure data and displacement data to obtain a stress nephogram of a local flow field.

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