Slurry diffusion visual test system applied to rock and soil grouting and use method thereof

Abstract

The invention provides a slurry diffusion visualization test system applied to rock and soil grouting and a use method thereof, and particularly relates to the technical field of geotechnical engineering test equipment. The test system comprises a control cabinet, a simulation box, a thermal infrared imager, a heating mechanism, a cooling liquid storage tank and a liquid cooling pipe, the thermal infrared imager is arranged right above the simulation box; the heating mechanism is laid on the top of the simulation box; a simulation tunnel is arranged in the inner cavity of the simulation box along the length direction; a plurality of high-frequency induction coils are arranged on the outer surface of the simulation box corresponding to the simulation tunnel; a plurality of thermocouples are arranged in the simulation box at equal intervals; a stratum grouting mechanism is arranged along the periphery of the simulation tunnel; a plurality of electromagnets distributed in a matrix are arranged in an inner cavity of the simulation box; the residual space of the inner cavity of the simulation box is filled with a simulation soil layer. A traditional transparent box body and a soil body are replaced, planning and visualization of the slurry path and control over the solidification time can be achieved at the same time, and the slurry diffusion dynamic three-dimensional map generated in real time is utilized and is more visual.

Description

Technical Field

[0001] This invention patent relates to the technical field of geotechnical engineering test equipment, and particularly relates to a visualization test system for slurry diffusion applied to geotechnical grouting and its usage method. Background Art

[0002] In the field of geotechnical engineering, grouting technology is widely used in aspects such as foundation reinforcement, tunnel leakage blocking, and geological disaster prevention and control. Existing grouting test equipment and patented technologies mainly simulate the slurry diffusion process through physical models, but they have significant deficiencies in the complex environment simulation ability, multi-field coupling control accuracy, and dynamic monitoring means.

[0003] The common existing technologies have the following defects: 1. Lack of authenticity in simulation: The realization of the visualization of the slurry diffusion of existing geotechnical grouting mainly relies on transparent boxes and transparent similar materials to simulate the soil body. However, traditional transparent model boxes cannot simulate the non-transparent characteristics of the real stratum, and it is difficult to replace all the mechanical properties of the soil body due to the limitations of transparent similar materials; 2. Uncontrollable path: Traditional grouting tests rely on fixed pressure and flow parameters and cannot correct the slurry diffusion path in real time, resulting in the penetration range exceeding the designed area; 3. Material limitations: Conventional slurries lack the ability to respond to external physical fields and are difficult to achieve dynamic rheological property adjustment; 4. Insufficient monitoring accuracy: Existing systems mostly use a single pressure sensor, lack the ability of multi-dimensional data fusion analysis, and cannot obtain three-dimensional slurry diffusion data. Summary of the Invention

[0004] To overcome the above-mentioned deficiencies of the existing technologies, the present invention provides a visualization test system for slurry diffusion applied to geotechnical grouting and its usage method. The specific technical solutions are as follows:

[0005] A slurry diffusion visualization test system applied to geotechnical grouting, comprising a control cabinet, a simulation box, an infrared thermal imager, a heating mechanism, a coolant storage tank and a liquid cooling pipe; a PID control system, a data processing and analysis system, a magnetic induction tomography system, a lock-in amplifier, a magnetic field controller, a distributed optical fiber temperature measurement system and a temperature controller are arranged in the control cabinet; a simulated tunnel is arranged in the inner cavity of the simulation box along its length direction; the infrared thermal imager is arranged directly above the top of the simulation box; the heating mechanism is laid on the top of the simulation box; a plurality of high-frequency induction coils are arranged at equal intervals on the left and right outer side walls, front and rear outer side walls and the top wall of the heating mechanism corresponding to the position of the simulated tunnel; a plurality of thermocouples are arranged at equal intervals directly above and directly below the simulated tunnel along the length direction in the simulation box; a stratum grouting mechanism is arranged along the periphery of the simulated tunnel; a plurality of electromagnets distributed in a matrix are arranged in the inner cavity of the simulation box along the X, Y and Z axes; the plurality of electromagnets are respectively fixed at anchor points preset on the inner side wall of the simulation box through a plurality of fixing frames; the electromagnets are connected to the fixing frames through bolts; a copper foil layer is pasted on the outer surface of each electromagnet avoiding the bolt connection points; the liquid cooling pipe is sequentially fixed on one side of a plurality of bolts through a plurality of buckles and has a gap with the copper foil layer on the surface of the electromagnet; the inlet of the liquid cooling pipe is connected to the outlet of the coolant storage tank through an outlet pipe; the outlet of the liquid cooling pipe is connected to the inlet of the coolant storage tank through an inlet pipe; the remaining space in the inner cavity of the simulation box is filled with simulated soil layer.

[0006] Preferably, the distance between the lens of the infrared thermal imager and the top of the simulation box is 0.5 - 1m.

[0007] Preferably, the magnetic induction intensity range of each electromagnet is 0.1 - 1.5T; the thickness of the copper foil layer is 0.5mm.

[0008] Preferably, the heating mechanism is composed of a plurality of heating plates with a thickness of 25 - 30mm spliced together, and each heating plate forms an independent temperature control area; a heat insulation layer with a width of 5mm and a thickness of 25 - 30mm is arranged between two adjacent heating plates; the heating temperature range of the heating plate is from room temperature to 150°C, the power is 1.8 - 3.75KW, and the accuracy is ±0.5°C; the heating plate includes a heating layer and a heat conduction layer from top to bottom in sequence; nickel-chromium alloy wires are distributed in a grid shape in the heating layer; the heat conduction layer is made of aluminum nitride ceramic material.

[0009] Also preferably, the formation grouting mechanism includes a number of grouting unit components arranged at equal intervals along the length direction of the simulated tunnel; the number of the grouting unit components are all divided into an upper half grouting part and a lower half grouting part with the same structure; the upper half grouting part or the lower half grouting part both include a slurry delivery pipe communicated with the outlet of a micro-injection pump outside the model box, one end of the slurry delivery pipe close to the simulated tunnel is provided with an arc-shaped pipe adapted to the outer surface of the simulated tunnel, and a number of grouting perforated pipes are connected in series at equal intervals on the arc-shaped pipe; a number of slurry outlet holes are formed on the surface of the grouting perforated pipe, and a foam rubber layer is fixed on the surface of the number of slurry outlet holes through rubber nylon wires; independent valves are arranged at one ends of the slurry delivery pipes far away from the model box; optical fiber grating sensors are spirally wound on the surfaces of the number of grouting unit components; the slurry delivery pipe, the arc-shaped pipe and the grouting perforated pipe are all communicated with each other.

[0010] Also preferably, the spatial resolution of the optical fiber grating sensor is 0.1 m, and the temperature accuracy is ±0.1 °C.

[0011] Further preferably, the grouting slurry in the slurry delivery pipe is mixed with magnetite magnetic nanoparticles with a particle size of 10 - 30 nm and accounting for 5% - 8% of the total mass of the slurry, and thermosensitive microcapsules with a diameter of 10 - 50 μm and accounting for 3% - 5% of the total mass of the slurry; wherein, the surface of the magnetite magnetic nanoparticles is coated with silicon hydroxyl groups generated by hydrolysis of silane coupling agent, which combine with the particle surface to form a physical barrier; the thermosensitive microcapsules sequentially include a shell and a core from outside to inside, and the shell is made of polyurethane material; the core is made of a paraffin stearic acid composite phase change material, and the dissolution temperature of the core is 40 - 80 °C; a solidification catalyst made of a sulfoaluminate material is filled in the core.

[0012] Also further preferably, the gap width between the liquid cooling pipe and the copper foil layer on the surface of the electromagnet is 1 mm, and four layers of ceramic fiber gaskets are stacked in the gap; the density of each layer of the ceramic fiber gaskets ≥ 128 kg / m 3 、with a thickness of 0.25 mm; the adjacent two layers of ceramic fiber gaskets are stacked with left - right dislocation and the offset ≥ 5 mm; the copper foil layer and the electromagnet, and the ceramic fiber gasket close to the copper foil layer and the surface of the copper foil layer are both bonded through conductive adhesive; the rest of the ceramic fiber gaskets are bonded and fixed through high - temperature resistant silica gel with a working temperature of - 60 - 300 °C.

[0013] Even more preferably, the infrared thermal imager, the temperature controller, the heating mechanism, a number of thermocouples, the lock - in amplifier, a number of high - frequency induction coils, the magnetic induction tomography system, the magnetic field controller, a number of electromagnets, the distributed optical fiber temperature measurement system, the optical fiber grating sensor, and the data processing and analysis system are all electrically connected to the PID control system.

[0014] A method for using a slurry diffusion visualization test system for rock and soil grouting, using the slurry diffusion visualization test system, specifically includes the following steps:

[0015] S1. Preparation stage:

[0016] S1.1 Install and connect all components and equipment, set test parameters, and complete filling of the simulation chamber cavity with simulated strata to ensure that the soil is uniform and in close contact with the inner wall of the simulation chamber;

[0017] S1.2 Prepare the grouting slurry and stir it thoroughly to ensure that the slurry is evenly mixed;

[0018] S2. Experimental phase:

[0019] S2.1 Divide the heating mechanism into several independent temperature control zones according to the length of the simulation chamber. Divide the simulated formation into several grouting zones according to the number of temperature control zones. Turn on the micro-injection pump and start grouting in the first zone.

[0020] S2.2 starts the magnetic field controller and dynamically adjusts the coil current, magnetic field strength, and direction of each electromagnet in the first region through a PID algorithm according to the preset slurry diffusion path, thereby forming a magnetic field gradient in the first region and guiding the slurry to migrate in a directional manner;

[0021] S2.3 using a high-frequency induction coil located at the first region to monitor the distribution of the ferroferric oxide magnetic nanoparticles in the slurry by electromagnetic coupling;

[0022] S2.4 monitors the amplitude and phase difference of the high-frequency induction coil voltage signal located in the first region through a lock-in amplifier and transmits the data to a magnetic induction tomography system. Using the Landweber iteration method, a three-dimensional image of the concentration distribution of ferroferric oxide magnetic nanoparticles in the slurry is constructed, achieving three-dimensional visualization of the slurry diffusion.

[0023] S2.5 When the magnetic induction tomography system indicates that the slurry has reached a designated area, the temperature of the designated area is increased by a temperature controller until the core material of the thermosensitive microcapsule melts, causing the shell to expand and crack. The coagulation catalyst in the core material is released into the slurry, accelerating the coagulation of the slurry and shortening the local coagulation time of the slurry, thereby achieving coagulation control;

[0024] S2.6 uses thermocouples and fiber Bragg grating sensors located in the first area to detect temperature changes at the interface between the slurry and the soil, generating a temperature field cloud map. An infrared thermal imager monitors the temperature field distribution. A magnetic induction tomography system generates a real-time three-dimensional image of the slurry diffusion dynamics within the first area, completing the test in the first area and ending the grouting in that area.

[0025] S2.7 Just complete the slurry visualization tests in other areas in sequence;

[0026] S3. Test data collation:

[0027] Comprehensively analyze the collected data, evaluate the slurry diffusion path, setting time and state, and temperature distribution, compare with the preset targets, and complete optimization and improvement.

[0028] The beneficial effects of the present invention are as follows:

[0029] 1. By changing the current, magnetic field strength and direction of the electromagnet coil and cooperating with the magnetic iron oxide nanoparticles in the slurry, the present invention can effectively control the slurry diffusion path;

[0030] 2. The infrared thermal imager of the present invention can ensure that the field of view covers the entire heating area and understand the temperature change in real time;

[0031] 3. By setting a high-frequency induction coil in combination with a lock-in amplifier, the present invention can, on the premise of not affecting the magnetic field control, collect the induced voltage signal generated by the high-frequency induction coil during the slurry diffusion process, and realize the visualization imaging of the slurry diffusion process;

[0032] 4. By setting a heating plate connected to a temperature controller in cooperation with a thermocouple, the present invention can effectively monitor and regulate the temperature, and further control the solidification speed of the slurry in the target area. Description of the Drawings

[0033] The attached drawings constituting the description of the present invention are used to provide a further understanding of the present application and do not constitute an improper limitation to the present application.

[0034] Figure 1 It is a schematic diagram of the overall structure of the present invention (partial box plates are omitted);

[0035] Figure 2 It is a front view of the internal structure of the simulation box after removing the formation grouting mechanism;

[0036] Figure 3 It is a side view of the internal structure of the simulation box after removing the formation grouting mechanism;

[0037] Figure 4 It is a side view of the formation grouting mechanism;

[0038] In the figure, 1 - simulation box; 2 - simulation tunnel; 3 - slurry delivery pipe; 301 - grouting perforated pipe; 4 - control cabinet; 5 - infrared thermal imager; 6 - heating plate; 7 - heat insulation layer; 8 - electromagnet; 9 - fixing rack; 10 - liquid cooling pipe; 11 - coolant storage tank; 1101 - liquid outlet pipe; 1102 - liquid inlet pipe; 12 - high-frequency induction coil; 13 - thermocouple. Specific Embodiments

[0039] The specific embodiments of a slurry diffusion visualization test system and its usage method for geotechnical grouting provided by the present invention are further described in conjunction with the accompanying drawings and embodiments.

[0040] As Figure 1 shown, a slurry diffusion visualization test system for geotechnical grouting includes a simulation box 1, a control cabinet 4, an infrared thermal imager 5, a heating mechanism, a liquid cooling pipe 10, and a coolant storage tank 11.

[0041] Preferably, the control cabinet 4 is provided with a PID control system, a data processing and analysis system, a magnetic induction tomography (MIT) system, a lock-in amplifier, a magnetic field controller, a distributed optical fiber temperature measurement system, and a temperature controller.

[0042] Preferably, a simulation tunnel 2 is arranged along the length direction of the inner cavity of the simulation box 1; the infrared thermal imager 5 is arranged directly above the top of the simulation box 1 at a position 0.5 - 1 m away from the top of the simulation box to ensure that the field of view can cover the entire heating mechanism, monitor the surface temperature field distribution of the model box, and calibrate the heat conduction uniformity of the heating plate 6.

[0043] Preferably, the heating mechanism is laid on the top of the simulation box 1 and is divided into several independent temperature control areas according to the length of the simulation box 1, which is convenient for observing grouting in different areas. Specifically, the heating mechanism is composed of several heating plates 6 with a thickness of 25 - 30 mm spliced together; a heat insulation layer 7 with a width of 5 mm and a thickness of 25 - 30 mm is arranged between adjacent two heating plates 6 to block the lateral heat conduction interference between the heating plates 6. Among them, the heating temperature range of the heating plate 6 is from room temperature to 150 °C, the power is 1.8 - 3.75 KW, and the accuracy is ±0.5 °C.

[0044] Preferably, in order to improve the heat conductivity of the heating mechanism, the heating plate 6 includes a heating layer and a heat conduction layer from top to bottom in sequence; nickel-chromium alloy wires for improving heating uniformity are distributed in a grid pattern in the heating layer; the heat conduction layer is made of aluminum nitride ceramic material with high heat conductivity.

[0045] Preferably, a number of high-frequency induction coils 12 are evenly arranged at equal intervals on the left and right outer walls, front and rear outer walls of the simulation box 1, and the top wall of the heating mechanism corresponding to the position of the simulation tunnel 2, which are used to excite the magnetic nanoparticles of magnetite in the slurry, obtain the slurry diffusion information, and collect the amplitude and phase difference of the induced voltage signals generated by the high-frequency induction coils 12 during the slurry diffusion process through a lock-in amplifier, eliminate the environmental electromagnetic noise, and then transmit these signals to the magnetic induction tomography (MIT) system, and use the Landweber iterative method to generate a dynamic three-dimensional image of the slurry diffusion, realizing the visualization of the slurry diffusion process.

[0046] Preferably, a plurality of thermocouples 13 are equidistantly arranged directly above and directly below the simulation box 1 along the length direction of the simulation tunnel 2, so as to monitor the temperature change of the simulated formation outside the simulation tunnel 2.

[0047] Preferably, a formation grouting mechanism is further arranged along the periphery of the simulation tunnel 2, and is used for pouring and reinforcing the gaps between the simulated formations.

[0048] As Figures 2 - 3 shown, a plurality of electromagnets 8 distributed in a matrix are arranged in the inner cavity of the simulation box 1 along the X, Y, and Z axes. Preferably, the magnetic induction intensity of each electromagnet 8 is 0.1 - 1.5 T; among them, the plurality of electromagnets 8 are respectively fixed at the preset anchor points on the inner side wall of the simulation box 1 through a plurality of fixing frames 9 made of aluminum alloy materials. Preferably, each electromagnet 8 is connected to the fixing frame 9 through bolts; a copper foil layer with a thickness of 0.5 mm is pasted on the outer surface of each electromagnet 8 avoiding the bolt connection positions; the liquid cooling pipes 10 are sequentially fixed on one side of a plurality of bolts through a plurality of buckles, ensuring that each electromagnet 8 has a liquid cooling pipe 10 passing through. There is a 1 - mm gap between the installation position of the liquid cooling pipe 10 and the copper foil layer on the surface of each electromagnet 8; four layers of ceramic fiber gaskets are stacked in the gap; the density of each layer of the ceramic fiber gasket ≥ 128 kg / m 3 , thickness is 0.25 mm; the adjacent two layers of ceramic fiber gaskets are stacked with left - right dislocation and the offset ≥ 5 mm to avoid the heat bridge effect caused by the overlap of joints. Between the copper foil layer and the electromagnet 8, and between the ceramic fiber gasket close to the copper foil layer and the surface of the copper foil layer (it is necessary to ensure that this layer of ceramic fiber gasket is closely attached to the surface of the copper foil layer, and press to exhaust air), they are bonded through conductive glue; between the remaining ceramic fiber gaskets, they are bonded and fixed through high - temperature resistant silica gel with an operating temperature of - 60 - 300 °C. It should be noted here that the copper foil layer forms a closed shielding layer through its high conductivity, effectively attenuating the interference of the electromagnetic field on the surrounding circuits, and realizing a magnetic field strength suppression of ≥ 70% in the magnetic field core area; the double - layer shielding design of the copper foil layer combined with the misaligned ceramic fiber gaskets further reduces the eddy current effect and ensures the electromagnetic compatibility of the system.

[0049] Preferably, the inlet of the liquid cooling pipe 10 is connected to the outlet of the coolant storage tank 11 through the liquid outlet pipe 1101; the outlet of the liquid cooling pipe 10 is connected to the inlet of the coolant storage tank 11 through the liquid inlet pipe 1102, thereby completing the circulation of the cooling system, and effectively dissipating heat from the surface of the electromagnet, avoiding the influence of overheating of the electromagnet surface on the magnetic field strength and system stability.

[0050] After installing the above - mentioned various components, the remaining space in the inner cavity of the simulation box 1 is filled with simulated soil layer. During filling, it is necessary to ensure that the soil body is uniform and in close contact with the inner wall of the simulation box 1 to ensure the accuracy of the test results.

[0051] As Figure 4 shown, the stratum grouting mechanism includes a number of grouting unit components arranged at equal intervals along the length direction of the simulated tunnel 2; the number of grouting unit components are evenly divided into an upper half grouting part and a lower half grouting part with the same structure. Among them, both the upper half grouting part or the lower half grouting part include a slurry delivery pipe 3 connected to the outlet of a micro-injection pump outside the model box 1. One end of the slurry delivery pipe 3 close to the simulated tunnel 2 is provided with an arc-shaped pipe adapted to the outer surface of the simulated tunnel 2. A number of grouting perforated pipes 301 are connected in series at equal intervals on the arc-shaped pipe; the slurry delivery pipe, the arc-shaped pipe and the grouting perforated pipe are all connected. A number of slurry outlet holes are formed on the surface of the grouting perforated pipe 301, and a foam rubber layer is fixed on the surface of the number of slurry outlet holes through rubber nylon wires; when grouting, the slurry pressure squeezes the foam rubber layer to deform outward, opening the slurry outlet channel; after the grouting is completed, the foam rubber layer retracts to fit the surface of the skeleton of the arc-shaped pipe 301 due to the elastic restoring force, closing the slurry outlet holes and preventing the backflow of the slurry.

[0052] It is worth noting here that in order to separately observe the slurry diffusion process in several heating zones, an independent valve is provided at one end of each slurry delivery pipe 3 away from the model box 1, which is convenient for targeted grouting.

[0053] Preferably, optical fiber grating sensors with a spatial resolution of 0.1 m and a temperature accuracy of ±0.1 °C are spirally wound on the surfaces of the number of grouting unit components, and the winding interval is 5 cm; the optical fiber grating sensors are electrically connected to the PID control system through a distributed optical fiber temperature measurement system, and are used to monitor the temperature change of the slurry in each grouting unit component.

[0054] To achieve controllable slurry diffusion paths, the slurry used in the slurry delivery pipe 3 is mixed with 5% to 8% of the total slurry mass ratio of ferroferric oxide magnetic nanoparticles with a particle size of 10 to 30 nm, and 3% to 5% of the total slurry mass ratio of thermosensitive microcapsules with a diameter of 10 to 50 μm. The surface of the ferroferric oxide magnetic nanoparticles is coated with silanol groups produced by the hydrolysis of a silane coupling agent, which bind to the particle surface to form a physical barrier, effectively reducing the agglomeration of the ferroferric oxide magnetic nanoparticles, improving the dispersion of the ferroferric oxide magnetic nanoparticles in the slurry, and inhibiting particle sedimentation or aggregation. Furthermore, the thermosensitive microcapsules comprise, from the outside to the inside, an outer shell and a core material. The outer shell is made of polyurethane; the core material is made of a paraffin stearic acid composite phase change material with a dissolution temperature of 40 to 80°C; and the core material is filled with a coagulation catalyst made of a sulphoaluminate material. When the temperature rises to the melting temperature of the core material, the molten volume of the core material expands, causing the shell to rupture. At this time, the solidification catalyst in the core material will flow into the slurry through the cracks in the shell and undergo a hydrolysis reaction with the sodium silicate in the slurry to consume OH- ions, lower the pH value, and thus shorten the local solidification time of the slurry.

[0055] More preferably, the infrared thermal imager 5, temperature controller, heating mechanism, multiple thermocouples 13, lock-in amplifier, multiple high-frequency induction coils 12, magnetic induction tomography system, magnetic field controller, multiple electromagnets 8, distributed optical fiber temperature measurement system, optical fiber Bragg grating sensor, and data processing and analysis system are all electrically connected to the PID control system.

[0056] A method for using a slurry diffusion visualization test system for rock and soil grouting, using the slurry diffusion visualization test system, specifically includes the following steps:

[0057] S1. Preparation stage:

[0058] S1.1 Install and connect all components and equipment, set test parameters, and complete filling of the simulation chamber cavity with simulated strata to ensure that the soil is uniform and in close contact with the inner wall of the simulation chamber;

[0059] S1.2 Prepare the grouting slurry and stir it thoroughly to ensure that the slurry is evenly mixed;

[0060] S2. Experimental phase:

[0061] S2.1 Divide the heating mechanism into several independent temperature control zones according to the length of the simulation chamber. Divide the simulated formation into several grouting zones according to the number of temperature control zones. Turn on the micro-injection pump and start grouting in the first zone.

[0062] S2.2 Start the magnetic field controller. According to the preset slurry diffusion path, dynamically adjust the coil current, magnetic field strength and direction of each electromagnet in the first area through the PID algorithm to form a magnetic field gradient in the first area, thereby guiding the directional migration of the slurry;

[0063] S2.3 Use the high-frequency induction coil located in the first area to monitor the distribution of magnetite magnetic nanoparticles in the slurry by electromagnetic coupling;

[0064] S2.4 Monitor the amplitude and phase difference of the voltage signal of the high-frequency induction coil located in the first area through a lock-in amplifier, and transmit the data to the magnetic induction tomography system. Use the Landweber iterative method to construct a three-dimensional image of the concentration distribution of magnetite magnetic nanoparticles in the slurry to achieve three-dimensional visualization of slurry diffusion;

[0065] S2.5 When the magnetic induction tomography system shows that the slurry reaches the specified area, heat up the specified area through the temperature controller until the core material of the thermosensitive microcapsule melts, causing the volume of the outer shell to expand and crack, and the solidification catalyst located in the core material is released into the slurry, accelerating the solidification speed of the slurry, shortening the local solidification time of the slurry, and achieving solidification control;

[0066] S2.6 Detect the temperature change data of the contact surface between the slurry and the soil through the thermocouple and fiber Bragg grating sensor located in the first area to generate a temperature field cloud map; monitor the temperature field distribution through an infrared thermal imager; use the magnetic induction tomography system to generate a dynamic three-dimensional image of the slurry diffusion in the first area in real time, and then complete the test of the first area and end the grouting of this area;

[0067] S2.7 Just complete the slurry visualization tests of other areas in turn;

[0068] S3. Test data arrangement:

[0069] Comprehensively analyze the collected data, evaluate the slurry diffusion path, solidification time and state, and temperature distribution, compare with the preset target, and improve and optimize the test system by means of changing the size of the electromagnet, optimizing the grouting system, updating the PID algorithm, etc.

[0070] Example:

[0071] Taking the size of the simulation box as 3m×2m×2m as an example, there are 4 layers of internal cavity electromagnets arranged along the Y-axis direction of the simulation box. Along the X-axis direction, 6 electromagnets are arranged at equal intervals on each layer. Along the Z-axis direction, 4 electromagnets are arranged at equal intervals on each layer. The length, width and height of a single electromagnet are 0.1m×0.05m×0.03m, and the magnetic field strength in the central area of a single electromagnet is 1.5T; the liquid cooling pipe is made of a stainless steel corrugated pipe with an outer diameter of 5mm and a bending radius ≥25mm; the heating mechanism is divided into 5 heating plates, that is, divided into 5 independent temperature control areas (each area is 60cm long).

[0072] During the test, grouting is carried out in each independent temperature control area respectively. The coil current (0 - 100A) in each electromagnet is independently adjusted through the PID algorithm to form a magnetic field gradient (0.1 - 1.5T / m) in the current grouting area: if the slurry needs to deflect to the left, the current of the right electromagnet group increases (magnetic field strength 1.2T), and the current on the left decreases (0.8T), then a magnetic field gradient from right to left can be formed, and the Fe3O4 nanoparticles in the slurry generate a magnetization force under the magnetic field gradient to drive the slurry to migrate to the high magnetic field strength area; when the magnetic induction tomography (MIT) system detects that the slurry deviates from the preset path (deviation > 5mm), the current of adjacent electromagnets is adjusted dynamically in time, and the slurry direction is corrected with a gradient increment of 0.1T / m, so as to realize the control of the slurry diffusion path (the specific process of how to control the slurry to deflect to the right will not be elaborated here).

[0073] When the slurry reaches the set area, it enters the thermal trigger stage (to promote the rupture of thermosensitive microcapsules): the frequency of the electromagnet group in the current grouting area is reduced to 500Hz (that is, the power is reduced by 50%), and the heating plate is heated to above 60℃ at a rate of 10℃ / min at full power (using the PID algorithm to dynamically adjust the power of the temperature zone, and cooperating with the real-time feedback of the thermocouple, the temperature difference can be controlled within ±1℃). The solidification catalyst in the core material reacts with sodium silicate in the slurry after entering the slurry to consume OH- ions, reduce the PH value, and shorten the local solidification time of the slurry by 30% - 70%.

[0074] The high-frequency induction coil is controlled by a Magneto-Inductive Tomography (MIT) system to sequentially emit alternating magnetic fields. A lock-in amplifier is used to extract the voltage amplitude ΔV and phase difference Δφ (sensitivity 1 μV / °) generated by the high-frequency induction coil during the slurry diffusion process, eliminate environmental electromagnetic noise, and transmit the data to the Magneto-Inductive Tomography (MIT) system. Then, the Landweber iterative algorithm is used to generate a dynamic three-dimensional image of the slurry diffusion in the grouting area, magnetic field intensity contour lines (showing the magnetic field gradient distribution, identifying the driving direction and intensity difference of the electromagnet array on the slurry. The strong magnetic field area, i.e., the area where the contour lines are dense, corresponds to the main migration path of the slurry, which is the diffusion path), and a temperature field cloud map (generated by using the data collected by thermocouples and fiber Bragg grating sensors through a data processing and analysis system, and its displayed temperature color scale differentiates the slurry states of the solidified / high-temperature area and the flowing / low-temperature area). The collected data is comprehensively analyzed to evaluate the slurry diffusion path, solidification time and state, temperature change and distribution, compare with the preset target, and complete optimization and improvement.

[0075] The present invention replaces the traditional transparent box body and soil body, can simultaneously realize the planning, visualization of the slurry path and the control of the solidification time, and is more intuitive by using the dynamically generated three-dimensional map of the slurry diffusion.

[0076] In the present invention, terms such as "upper", "lower", "bottom", "top", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings. They are only relational terms determined to facilitate the description of the structural relationship of each component or element of the present invention, and do not specifically refer to any component or element in the present invention, and should not be construed as a limitation to the present invention. Terms such as "connected" and "joined" should be understood in a broad sense, indicating that it can be a fixed connection, an integral connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate medium. For those skilled in the relevant scientific research or technology in this field, the specific meanings of the above terms in the present invention can be determined according to specific circumstances, and should not be construed as a limitation to the present invention.

[0077] Certainly, the above description is not a limitation to the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the technical field of the present invention within the substantial scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A visualization test system for slurry diffusion applied to geotechnical grouting, characterized in that, It includes a control cabinet, a simulation box, an infrared thermal imager, a heating mechanism, a coolant storage tank and a liquid cooling pipe; The control cabinet is provided with a PID control system, a data processing and analysis system, a magnetic induction tomography system, a lock-in amplifier, a magnetic field controller, a distributed optical fiber temperature measurement system and a temperature controller; A simulation tunnel is arranged along the length direction of the inner cavity of the simulation box; The infrared thermal imager is arranged directly above the top of the simulation box; the heating mechanism is laid on the top of the simulation box; a number of high-frequency induction coils are equidistantly arranged at positions corresponding to the simulation tunnel on the left and right outer walls, front and rear outer walls and the top wall of the heating mechanism of the simulation box; A number of thermocouples are equidistantly arranged at positions directly above and directly below the simulation tunnel along the length direction of the simulation box; a stratum grouting mechanism is arranged along the periphery of the simulation tunnel; A number of electromagnets distributed in a matrix are arranged along the X, Y, and Z axes in the inner cavity of the simulation box; a number of the electromagnets are respectively fixed at anchor points preset on the inner side wall of the simulation box through a number of fixing frames; the electromagnets are connected to the fixing frames by bolts; a copper foil layer is pasted on the outer surface of each electromagnet avoiding the bolt connection positions; The liquid cooling pipe is sequentially fixed on one side of a number of bolts through a number of buckles and has a gap with the copper foil layer on the surface of the electromagnet; the inlet of the liquid cooling pipe is connected to the outlet of the coolant storage tank through an outlet pipe; the outlet of the liquid cooling pipe is connected to the inlet of the coolant storage tank through an inlet pipe; The remaining space in the inner cavity of the simulation box is filled with simulated soil layer.

2. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 1, characterized in that, The distance between the lens of the infrared thermal imager and the top of the simulation box is 0.5 - 1m.

3. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 2, characterized in that, The magnetic induction intensity range of each electromagnet is 0.1 - 1.5T; the thickness of the copper foil layer is 0.5mm.

4. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 3, characterized in that, The heating mechanism is composed of a number of heating plates with a thickness of 25 - 30mm spliced together, and each heating plate forms an independent temperature control area; a heat insulation layer with a width of 5mm and a thickness of 25 - 30mm is arranged between adjacent two heating plates; The heating temperature range of the heating plate is from room temperature to 150°C, the power is 1.8 - 3.75KW, and the accuracy is ±0.5°C; The heating plate includes a heating layer and a heat conduction layer from top to bottom in sequence; nickel-chromium alloy wires are distributed in a grid shape in the heating layer; the heat conduction layer is made of aluminum nitride ceramic material.

5. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 4, characterized in that, The stratum grouting mechanism includes a number of grouting unit components equidistantly arranged along the length direction of the simulation tunnel; a number of the grouting unit components are all divided into an upper half grouting part and a lower half grouting part with the same structure; Both the upper half grouting part or the lower half grouting part include a slurry delivery pipe communicated with the outlet of a micro-injection pump outside the model box, one end of the slurry delivery pipe close to the simulation tunnel is provided with an arc-shaped pipe adapted to the outer surface of the simulation tunnel, and a number of grouting perforated pipes are connected in series at equal intervals on the arc-shaped pipe; a number of slurry outlet holes are formed on the surface of the grouting perforated pipe, and a foam rubber layer is fixed on the surface of a number of the slurry outlet holes through rubber nylon wires; Independent valves are arranged at one ends of the slurry delivery pipes far away from the model box; A fiber Bragg grating sensor is spirally wound on the surfaces of a number of the grouting unit components; The slurry delivery pipes, the arc-shaped pipes and the grouting perforated pipes are all communicated with each other.

6. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 5, characterized in that, The spatial resolution of the fiber Bragg grating sensor is 0.1 m, and the temperature accuracy is ±0.1°C.

7. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 5, characterized in that, The grouting slurry in the slurry delivery pipe is doped with 5% to 8% of the total mass ratio of the slurry and 10 to 30 nm of ferroferric oxide magnetic nanoparticles, and 3% to 5% of the total mass ratio of the slurry and 10 to 50 μm of diameter of thermosensitive microcapsules; The surface of the ferroferric oxide magnetic nanoparticles is coated with silanol groups generated by the hydrolysis of a silane coupling agent, which are combined with the particle surface to form a physical barrier; The thermosensitive microcapsule comprises an outer shell and a core material from the outside to the inside, wherein the outer shell is made of polyurethane material; the core material is made of paraffin stearic acid composite phase change material, and the dissolution temperature of the core material is 40-80°C; The core material is filled with a solidification catalyst made of sulphoaluminate material.

8. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 1, characterized in that, The width of the gap between the liquid cooling tube and the copper foil layer on the surface of the electromagnet is 1 mm, and four layers of ceramic fiber gaskets are stacked in the gap; The density of each layer of the ceramic fiber gasket ≥ 128 kg / m 3 , and the thickness is 0.25 mm; the adjacent two layers of ceramic fiber gaskets are stacked with left - right dislocation, and the offset ≥ 5 mm; The copper foil layer and the electromagnet, and the ceramic fiber gasket close to the copper foil layer and the surface of the copper foil layer are bonded by conductive adhesive; the remaining ceramic fiber gaskets are bonded and fixed by high-temperature resistant silica gel with a working temperature of -60 to 300°C.

9. The slurry diffusion visualization test system applied to geotechnical grouting according to claim 6, characterized in that, The infrared thermal imager, temperature controller, heating mechanism, several thermocouples, lock-in amplifier, several high-frequency induction coils, magnetic induction tomography system, magnetic field controller, several electromagnets, distributed optical fiber temperature measurement system, optical fiber Bragg grating sensor, and data processing and analysis system are all electrically connected to the PID control system.

10. A method of using a slurry diffusion visualization test system for geotechnical grouting, which uses the slurry diffusion visualization test system described in any one of the above claims 1-9, characterized in that, The specific steps include: S1. Preparation stage: S1.1 Install and connect all components and equipment, set test parameters, and complete filling of the simulation chamber cavity with simulated strata to ensure that the soil is uniform and in close contact with the inner wall of the simulation chamber; S1.2 Prepare the grouting slurry and stir it thoroughly to ensure that the slurry is evenly mixed; S2. Experimental phase: S2.1 Divide the heating mechanism into several independent temperature control zones according to the length of the simulation chamber. Divide the simulated formation into several grouting zones according to the number of temperature control zones. Turn on the micro-injection pump and start grouting in the first zone. S2.2 starts the magnetic field controller and dynamically adjusts the coil current, magnetic field strength, and direction of each electromagnet in the first region through a PID algorithm according to the preset slurry diffusion path, thereby forming a magnetic field gradient in the first region and guiding the slurry to migrate in a directional manner; S2.3 using a high-frequency induction coil located at the first region to monitor the distribution of the ferroferric oxide magnetic nanoparticles in the slurry by electromagnetic coupling; S2.4 monitors the amplitude and phase difference of the high-frequency induction coil voltage signal located in the first region through a lock-in amplifier and transmits the data to a magnetic induction tomography system. Using the Landweber iteration method, a three-dimensional image of the concentration distribution of ferroferric oxide magnetic nanoparticles in the slurry is constructed, achieving three-dimensional visualization of the slurry diffusion. S2.5 When the magneto - inductive tomography system shows that the slurry reaches the specified area, the temperature of the specified area is increased through the temperature controller until the core material of the thermosensitive microcapsule melts, causing the volume of the outer shell to expand and generate cracks, and the solidification catalyst located in the core material is released into the slurry, accelerating the solidification speed of the slurry, shortening the local solidification time of the slurry, and achieving solidification control; S2.6 The temperature change data of the contact surface between the slurry and the soil body are detected by the thermocouple and the fiber - Bragg grating sensor located in the first area to generate a temperature - field cloud map; the temperature - field distribution is monitored by an infrared thermal imager; the dynamic three - dimensional image of the slurry diffusion in the first area is generated in real time by using the magneto - inductive tomography system, and the test of the first area can be completed, and the grouting of this area is ended; S2.7 Just complete the slurry visualization tests of other areas in turn; S3. Test data collation: Comprehensively analyze the collected data, evaluate the slurry diffusion path, solidification time and state, and temperature distribution, compare with the preset target, and complete optimization and improvement.

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