Covering layer grouting visualization test device and test method

Abstract

The invention discloses a cover layer grouting visualization test device and method, and relates to the technical field of grouting tests.The cover layer grouting visualization test device comprises a model box and a grouting structure, the model box is used for containing a cover layer simulation structure, the cover layer simulation structure is of a transparent structure, a grouting hole is formed in the model box, and the grouting hole is communicated with the cover layer simulation structure; the grouting hole is used for being connected with a grouting structure, the grouting structure pours grout into the model box through the grouting hole, a laser is arranged above the model box, a camera is arranged on one side of the model box and electrically connected with a computer, a camera is arranged on the other side of the model box and electrically connected with the computer, and the laser is used for emitting laser. A speckle field is generated after the laser acts on the covering layer simulation structure, the camera is used for shooting the speckle field, and the camera is used for shooting grouting diffusion. The cover layer grouting visualization test device and test method provided by the invention can realize visualization and non-contact monitoring of grouting.

Description

Technical Field

[0001] The invention relates to the technical field of grouting tests, and in particular to a cover layer grouting visualization test device and a test method. Background Art

[0002] In the construction of water conservancy infrastructure projects, the foundation is particularly important. The rock and soil structure of the overburden is loose, the inter-particle voids are large, it is easy to be damaged, easy to be hydrated, and has poor stability. When constructing large-scale engineering facilities under such foundation conditions, if they are not handled properly, it will cause unpredictable consequences, which will not only affect the economic effect of the project, but may even lead to dam collapse and embankment crossing, causing great harm to the safety of life and property of the country and the people.

[0003] Grouting is a commonly used method for treating overburden. With the needs of dam construction, more and more deep overburden foundations need to be treated. Grouting projects are extremely concealed. There is a great deal of uncertainty in the distribution of pores, cracks, bedding, joints, etc. in the strata. It is a black box system, which brings great difficulties to the grouting design and grouting slurry mechanism analysis. Grouting model tests can adjust the influencing factors of grouting, control stratum changes, and reproduce the grouting process, thereby effectively verifying the correctness of theoretical analysis and numerical calculation results, and providing a basis for design parameters to guide the construction of grouting projects. It has important theoretical value and practical significance. Due to the complexity of slurry materials, the diversity of grouting construction, and the invisibility of the overburden, the study of grouting mechanism is relatively difficult.

[0004] Traditional grouting data monitoring methods rely on pre-buried sensors, which not only have low accuracy but are also difficult to link with grouting stratum changes. Data such as grouting diffusion form can only be measured by excavating the slurry stone body after the grouting is completed. Summary of the invention

[0005] The purpose of the present invention is to provide a visual test device and a test method for cover layer grouting, so as to solve the problems existing in the above-mentioned prior art and realize visualization and non-contact monitoring of grouting.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a cover layer grouting visualization test device, comprising: a model box and a grouting structure, wherein the model box is used to hold a cover layer simulation structure, the cover layer simulation structure is a transparent structure, a grouting hole is arranged in the model box, the grouting hole is used to be connected with the grouting structure, the grouting structure pours grouting liquid into the model box through the grouting hole, a laser is arranged above the model box, a camera is arranged on one side of the model box, the camera is electrically connected to a computer, a camera is arranged on the other side of the model box, the camera is electrically connected to the computer, the laser is used to emit laser, a speckle field is generated after the laser acts on the cover layer simulation structure, the camera is used to shoot the speckle field, and the camera is used to shoot grouting diffusion.

[0008] Preferably, the cover layer simulation structure is made of quartz sand particles and pore fluid, the pore fluid is made of white oil and isododecane, and the ratio between the white oil and the isododecane makes the refractive index of the pore fluid the same as the refractive index of the quartz sand particles.

[0009] Preferably, the vertical line of the camera is perpendicular to the axis of the laser source of the laser, and the intersection of the vertical line of the camera and the axis of the laser source of the laser is located in the area where the cover layer simulation structure is located in the model box.

[0010] Preferably, the grouting structure includes a grouting pump, a first valve and a first pressure transmitter connected through a grouting pipe, the grouting pump is used to transport the slurry in the slurry storage structure, the first pressure transmitter is connected to the grouting hole, the first pressure transmitter is used to monitor the pressure of the slurry entering the grouting hole, the first pressure transmitter is electrically connected to a data recorder, and the data recorder is electrically connected to a computer.

[0011] Preferably, a second valve, a pressure limiting valve, a second pressure transmitter and a flow meter are further provided on the grout inlet pipe between the grouting pump and the first valve, and the second pressure transmitter and the flow meter are electrically connected to the data recorder;

[0012] It also includes a slurry return pipe, one end of which is connected to the slurry inlet pipe between the flow meter and the first valve, the other end of which is connected to the grouting pump, and a third valve is provided on the slurry return pipe;

[0013] It also includes a regulating pipe, one end of which is connected to the grouting pump, and the other end of which is connected to the grouting pipe between the grouting pump and the second valve. A fourth valve is also provided on the regulating pipe.

[0014] Preferably, it also includes a camera, which is located on the other side of the model box and is electrically connected to the computer.

[0015] Preferably, an osmometer is arranged in the model box, and a displacement sensor is also arranged on the model box. The osmometer and the displacement sensor are both electrically connected to a data recorder, and the data recorder is electrically connected to a computer.

[0016] Preferably, the model box is made of a transparent material, a plurality of support rods are arranged between the front wall and the rear wall of the model box, and a reinforcement frame is arranged outside the model box.

[0017] Preferably, a hollow tube is provided between the front wall and the rear wall of the model box, the hollow tube is located at the center of the model box, one end of the hollow tube is used to connect with the grouting structure, a plurality of grouting holes are opened in the middle part of the hollow tube along the circumference of the hollow tube, and the grouting holes are used to communicate with the model box.

[0018] Preferably, a filter plate is provided on the model box, and the filter plate is located above the covering layer simulation structure. The pore size of the filter plate can allow porous fluid to pass through. An overflow hole is opened on the side wall of the model box, and the overflow hole is connected to a recovery box. A filter structure is provided in the recovery box. After passing through the filter plate, the porous fluid can enter the overflow hole and then enter the recovery box.

[0019] The present invention also discloses a test method using the cover layer grouting visualization test device, comprising:

[0020] Formulate cover layer simulation structure and slurry;

[0021] Turn on the laser and adjust the laser power and incident angle;

[0022] Adjust the grouting pressure of the grouting structure and carry out grouting;

[0023] A camera is used to capture the speckle field generated by the interaction between the laser and the simulated structure of the covering layer, and a camera is used to capture the grouting diffusion image.

[0024] Compared with the prior art, the present invention has achieved the following technical effects:

[0025] The present invention adopts a transparent covering layer simulation structure for testing, which is convenient for observation, and adopts lasers, cameras and video cameras to realize non-contact, non-destructive and continuous observation. The grouting strategy can be changed during the test to study the grouting form and reinforcement mechanism of the covering layer. The obtained data is used to evaluate and analyze the grouting reinforcement effect, in order to provide a theoretical basis for the selection of slurry, determination of grouting parameters and optimization of grouting process in actual engineering.

[0026] The present invention provides guidance and reference for the research on overburden grouting strategy and grouting process control technology, has important engineering application value, and is of great significance for in-depth understanding of the overburden grouting mechanism, improving the matching and anti-seepage sealing effect of on-site grouting process, and ensuring the stability and safety of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the cover layer grouting visualization test device of the present invention;

[0029] Figure 2 It is a schematic diagram of a model box of the present invention;

[0030] Figure 3 It is a schematic diagram of the front wall of the model box of the present invention;

[0031] Figure 4 is a schematic diagram of the pore fluid of the present invention;

[0032] Figure 5 Schematic diagram of quartz sand particles of the present invention;

[0033] Figure 6 It is a schematic diagram of the transparent soil mixing process of the present invention;

[0034] In the figure: 100-cover grouting visualization test device, 1-model box, 2-laser, 3-camera, 4-camera, 5-computer, 6-grouting pump, 7-first valve, 8-first pressure transmitter, 9-second valve, 10-pressure limiting valve, 11-second pressure transmitter, 12-flow meter, 13-data recorder, 14-third valve, 15-osmometer, 16-displacement sensor, 17-fourth valve, 18-front wall of the model box, 19-hollow tube, 20-filter plate, 21-reinforcement frame, 22-ribbed reinforcement base. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The purpose of the present invention is to provide a visual test device and a test method for cover layer grouting, so as to solve the problems existing in the above-mentioned prior art and realize visualization and non-contact monitoring of grouting.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Embodiment 1

[0039] like Figures 1 to 6 As shown, this embodiment provides a cover grouting visualization test device 100, which is particularly suitable for wide-graded cover layers. The particles of the wide-graded cover layers range from clay particles to coarse gravel (or crushed stone, block stone), and basically include all intermediate particle sizes. The cover grouting visualization test device 100 includes: a model box 1 and a grouting structure. The model box 1 is used to hold the cover layer simulation structure. The cover layer simulation structure is a transparent structure. The model box 1 is provided with grouting holes. The grouting holes are used to connect with the grouting structure. The grouting structure pours slurry into the model box 1 through the grouting holes. A laser 2 is arranged above the model box 1. A camera 3 is arranged on one side of the model box 1. The camera 3 is electrically connected to a computer 5. A camera 4 is arranged on the other side of the model box 1. The camera 4 is electrically connected to the computer 5. The laser 2 is used to emit laser. The laser generates a speckle field after interacting with the cover layer simulation structure. The camera 3 is used to shoot the speckle field. The camera 4 is used to shoot the grouting diffusion.

[0040] Specifically, in this embodiment, the covering layer simulation structure is made of transparent soil, and the transparent soil is made of quartz sand particles and pore fluid, the pore fluid is made of white oil and isododecane, and the ratio between white oil and isododecane makes the refractive index of the pore fluid the same as the refractive index of the quartz sand particles.

[0041] In this embodiment, the transparent soil has a visible thickness of 250 mm in a translucent state, which can meet the requirements of slurry diffusion tracking and stratum deformation observation during the grouting process of the covering layer. The quartz sand particles are fused quartz sand produced by Jiangsu Fucai Factory, with a chemical composition of silicon dioxide (SiO2) and a refractive index of 1.458. Its physical and mechanical properties are closer to natural sand. Based on the principle of similarity of particle gradation, fused quartz sand particles of different particle sizes are selected according to the actual engineering stratum particle composition, and the transparent soil skeleton material is configured according to the geological report parameters to achieve the purpose of simulating the physical and mechanical properties of the wide-gradation covering layer; the quartz sand produced by Morunk Company is used as the raw material for the transparent soil skeleton material. 15# Industrial white oil produced by Japan Idemitsu Co., Ltd. is mixed with isododecane solution in proportion, the volume ratio of 15# white oil to isododecane is 5:1, the mixed pore fluid is a colorless transparent liquid at room temperature (25°C), and the refractive index of the mixed pore fluid is measured by Abbe refractometer to be 1.458 to match the refractive index of fused quartz sand; in the preparation process, the transparent soil is saturated as much as possible, and the fused quartz sand is mixed with the pore fluid by layered sand falling method (each layer does not exceed 10cm), to obtain a transparent soil sample with physical and mechanical properties similar to those of the simulated covering layer, and the physical characteristics of the transparent soil such as density and porosity are measured.

[0042] In this embodiment, quartz sand particles are proportioned in five different sizes (2mm, 1mm, 0.5mm, 0.2mm and 0.1mm respectively) to simulate a wide-graded cover layer, and the proportions of the five sizes of quartz sand particles are the same as those in the wide-graded cover layer. Fused quartz sand is used to simulate the composition of the cover layer with various particle gradations, and the changes in grouting pressure, injection volume, stratum lift, and pressure in the stratum under different particle gradations are studied. The effects of slurry materials, grouting construction parameters, and stratum gradation on the slurry diffusion morphology are studied, and the slurry diffusion form and reinforcement mechanism are explored. The law of grouting disturbance on the surrounding strata is summarized, and the grouting parameters and the maximum deformation timing are determined, providing data support for the determination of grouting construction parameters and process control.

[0043] The quartz sand particles represent natural soil particles, while the pore fluid represents various properties of the pore fluid and provides a basis for visualization. This special composition reduces refraction and reflection when light propagates in transparent soil, thereby achieving a transparent visualization effect. As a light-transmitting medium, transparent soil has almost negligible absorption of light by transparent solid particles or transparent pore fluids in the visible light range. This allows light to pass through the transparent soil, thereby achieving visualization. The solid particles and pore fluid of transparent soil have matching refractive indices, which can reduce the refraction of light between solid particles and pore fluid, allowing light to pass through the transparent soil more smoothly.

[0044] In this embodiment, fused quartz sand, white oil and isododecane solution are used to prepare a transparent soil material with good visualization to simulate a wide-graded covering layer. By adjusting the components of white oil and isododecane solution to match the refractive index of fused quartz sand, a transparent soil material with stable performance and relatively low price is formed, which solves the problem of invisible grouting of the dam foundation and allows intuitive observation of the slurry diffusion morphology and diffusion process.

[0045] In this embodiment, the slurry displaces the pore fluid in the pores under pressure, and cement, water, water reducer, and bentonite are mixed in a certain proportion. The cement is P.O42.5 ordinary Portland cement, the water reducer is the third generation pure water-reducing polycarboxylic acid water reducer, and the bentonite is sodium bentonite. The sodium bentonite is soaked, stirred, and left to stand for 4 hours in water before preparation; and the water separation rate test is used to find the ratio with the lowest water separation rate, and fresh slurry is prepared according to this ratio; the physical and mechanical indicators such as the density, Marsh funnel viscosity, water separation rate, stone body strength, and rotational viscometer viscosity of the slurry are measured, which is of great significance for the calculation of slurry fluidity, diffusion distance calculation, and grouting pressure setting scheme. At the same time, the slurry ratio can also be appropriately adjusted according to the measured physical and mechanical indicators to adapt to more strata. Before grouting, the cement slurry is stirred and prepared and stored in the slurry storage structure, and the stirring is maintained at a uniform speed during the grouting process.

[0046] In this embodiment, laser 2, camera 3 and camera 4 form a digital image system. Camera 3 uses a Sony α6100 camera with an effective pixel of 24.2 million. Camera 3 takes pictures of the front of the model box 1, and realizes the timed continuous acquisition control of the image through the timed shutter line. Camera 3 is used to capture the speckle field before and after deformation and combined with digital image post-processing technology to study the displacement of particles; the camera performs continuous grouting diffusion monitoring on the back of the model box 1; laser 2 uses a 2500mw green laser generator, and laser 2 is placed on a linear slide, and the moving direction of the linear slide is parallel to the long side of the model box 1. In the test, the vertical line of camera 3 is perpendicular to the axis of the laser source of laser 2, and the intersection of the vertical line of camera 3 and the axis of the laser source is located in the area where the cover layer simulation structure is located, providing a guarantee for the smooth progress of the test. A ruler is placed on the surface of the model box 1 for transparent soil image processing identification calibration.

[0047] This embodiment transmits the images collected by the digital imaging system to the image analysis system of the PIV measurement system, adopts PIV (Particle Image Velocimetry) technology, collects and stores the images in real time through dedicated software, and performs data processing and analysis to obtain information such as flow field velocity distribution.

[0048] In this embodiment, the model box 1 is made of transparent organic glass, the model box 1 is a rectangular parallelepiped, the length × height × width of the model box 1 is 700mm × 700mm × 80mm, and a plurality of parallel support rods are arranged between the front wall 18 and the rear wall of the model box, and the support rods are fixed to the front wall 18 and the rear wall of the model box by bolts. In order to improve the overall strength of the model box 1 and ensure that the model box 1 meets the use requirements under various grouting pressures during the test, a reinforcement frame 21 is added to the outside of the model box 1: the reinforcement frame 21 uses four angle steels with a length × width × thickness of 30mm × 30mm × 4mm as frame columns, and perforated plates are welded on the frame columns, and then the perforated plates on the adjacent frame columns are clamped with Φ12 extended bolts; a rubber cushion with a thickness of 3mm is used for buffering between the reinforcement frame 21 and the model box 1, and a ribbed reinforcement base 22 is provided at the bottom of the model box 1.

[0049] In this embodiment, a hollow tube 19 is arranged between the front wall 18 and the rear wall of the model box. The hollow tube 19 is located at the center of the model box 1. One end of the hollow tube 19 is used to connect with the grouting structure. A plurality of grouting holes are opened in the middle part of the hollow tube 19 along the circumference of the hollow tube 19. The grouting holes are used to communicate with the model box 1.

[0050] In this embodiment, the upper end of the model box 1 is open, and a filter plate 20 with a hole diameter of 1 mm is arranged on the model box 1. The filter plate 20 is located above the cover layer simulation structure. The aperture of the filter plate 20 can allow the porous fluid to pass through. An overflow hole is opened on the side wall of the model box 1, and the overflow hole is connected to the recovery box. A regulating valve is arranged between the overflow hole and the recovery box. A filter structure is arranged in the recovery box. The filter structure includes two layers, the upper layer is a steel wire filter mesh, and the lower layer is a permeable mold bag. The filter structure is bonded to the side wall of the recovery box using an underwater adhesive. After the porous fluid passes through the filter plate 20, it can enter the overflow hole and then enter the recovery box.

[0051] In this embodiment, a piezometer 15 is provided in the model box 1. The piezometer 15 is protected by a sheath tube, and the wire of the piezometer 15 is led out. The piezometer 15 is preferably a immersion piezometer. The piezometer 15 is used to monitor the formation pressure. A displacement sensor 16 is also provided on the model box 1. The displacement sensor 16 is located above the filter plate 20. The displacement sensor 16 is preferably a linear displacement sensor. The displacement sensor 16 is used to monitor the surface lift. The piezometer 15 and the displacement sensor 16 are both electrically connected to the data recorder 13. The data recorder 13 is a paperless recorder. The data recorder 13 is electrically connected to the computer 5.

[0052] In this embodiment, the grouting structure includes a grouting pump 6, a first valve 7 and a first pressure transmitter 8 connected through a grouting pipe. The grouting pump 6 is used to transport the slurry in the slurry storage structure. The grouting pump 6 adopts a G20-1 single screw pump with a flow rate of 0-0.8m 3 / h, motor power 0.75kw, the first pressure transmitter 8 is connected to the grouting hole, the first pressure transmitter 8 is used to monitor the pressure of the slurry entering the grouting hole, the first pressure transmitter 8 is electrically connected to the data recorder 13, and the data recorder 13 is electrically connected to the computer 5; the slurry inlet pipe between the grouting pump 6 and the first valve 7 is also provided with a second valve 9, a pressure limiting valve 10, a second pressure transmitter 11 and a flow meter 12, the pressure limiting valve 10 is used to prevent excessive pressure from destroying the simulated structure of the covering layer in the model box 1, the flow meter 12 is preferably an electromagnetic flow meter, and the second pressure transmitter 11 and the flow meter 12 are electrically connected to the data recorder 13;

[0053] It also includes a slurry return pipe, one end of which is connected to the slurry inlet pipe between the flow meter 12 and the first valve 7, and the other end of which is connected to the grouting pump 6. A third valve 14 is provided on the slurry return pipe;

[0054] It also includes a regulating pipe, one end of which is connected to the grouting pump 6, and the other end of which is connected to the grouting pump 6 and the slurry inlet pipe between the grouting pump 6 and the second valve 9. A fourth valve 17 is provided on the regulating pipe.

[0055] When the grouting structure of this embodiment is working, the first valve 7, the second valve 9, and the third valve 14 are closed, and the fourth valve 17 is opened and opened to the maximum to ensure that the slurry moves in the loop between the grouting pump and the fourth valve 17; the fourth valve 17 is gradually reduced, and the second valve 9 and the third valve 14 are opened. The slurry passes through the grouting pump, the second valve 9, the pressure limiting valve 10, the second pressure transmitter 11, the flow meter 12 and the third valve 14, and moves in the loop formed by the grouting pump, the second valve 9, the pressure limiting valve 10, the second pressure transmitter 11, the flow meter 12 and the third valve 14. Check the second pressure transmitter 11, adjust the second valve 9 and the third valve 14, control the slurry to reach the specified pressure, adjust the pressure limiting valve 10 to the specified pressure, after the slurry runs stably, open the first valve 7, the slurry enters the model box 1, and by adjusting the third valve 14, check the pressure data of the first pressure transmitter 8 to reach the preset grouting pressure value, and grouting is carried out. A double-circulation pipeline is used to provide a continuous and stable power for the grouting hole. The double-circulation pipeline is a loop between the grouting pump and the fourth valve 17 and a loop formed by the grouting pump, the second valve 9, the pressure limiting valve 10, the second pressure transmitter 11, the flow meter 12 and the third valve 14.

[0056] In this embodiment, the first pressure transmitter 8, the second pressure transmitter 11, the flow meter 12, the displacement sensor 16, the piezometer 15 and the data recorder 13 constitute a data acquisition system. The first pressure transmitter 8 can collect the pipeline pressure of the slurry inlet pipe in real time, the piezometer 15 collects the formation pressure, the displacement sensor 16 collects the surface lift, and the flow meter 12 collects the grouting volume; the direction indicated by the arrow of the electromagnetic flowmeter must be consistent with the slurry flow direction. During grouting, the data recorder 13 is connected to the corresponding interfaces of the first pressure transmitter 8, the second pressure transmitter 11, the flow meter 12, the displacement sensor 16, and the piezometer 15 through the three-wire method to read and record the 4-20mA signal data output by each sensor during the test.

[0057] Grouting mechanism of wide-graded overburden: During the grouting process of wide-graded overburden, the slurry first enters the voids and cracks through the penetration and filling mechanism, and the energy consumption in this stage is relatively low. Subsequently, the slurry begins to exert pressure and squeeze the surrounding rock and soil, which is manifested as a compaction grouting mechanism. When the pressure increases to a certain level and exceeds the splitting strength of the rock and soil, splitting or stratum lifting occurs, which is manifested as a splitting grouting mechanism. The entire grouting process is actually a composite effect of these three mechanisms, in which energy consumption is mainly concentrated in the compaction stage and the splitting stage. Compaction grouting: The grouting material is injected into the cracks or pores of the overburden using air pressure or hydraulic principles. The grouting pressure needs to be controlled within an appropriate range to ensure that the slurry is fully diffused and fills the cracks. The slurry diffuses under pressure, and its range is affected by factors such as grouting pressure, slurry properties, and crack size. In the wide-graded overburden, the slurry forms an accumulation between particles, which helps to fill cracks and pores, improve the grouting effect, and squeeze the dam body, improve its stress state, and enhance deformation stability. Grouting in the splitting stage: Under a certain grouting pressure, the dam body is split in a specific direction (usually the direction of the dam axis). The direction, length and width of the splitting depend on the stress state of the original dam body and the grouting pressure. During the splitting process, the slurry fills the original cracks and holes, improves the integrity of the dam, and reduces leakage channels. Reasonable control of grouting pressure is the key to ensure effective diffusion and filling of the slurry. At the same time as splitting, slurry suitable for engineering reinforcement requirements is poured. After the slurry solidifies, it forms an anti-seepage wall that is firmly bonded to the dam body, improves the anti-seepage capacity of the dam body, and effectively solves the leakage problem. Therefore, the study of grouting pressure plays an important role in practical applications.

[0058] By adopting the visualization test device 100 of the overburden grouting of the present embodiment, according to the monitoring parameters over time such as slurry flow rate and slurry pressure, combined with the movement law of the slurry-stratum front and the expansion law of the slurry veins in the wide-graded overburden obtained by digital image processing technology, the slurry injection effect is analyzed and summarized, and the difference between the slurry movement and diffusion forms under different grouting pressures is summarized. The grouting reinforcement mechanism of the wide-graded overburden is summarized, and the effective reinforcement range of grouting is quantitatively analyzed by calculating the slurry diffusion range of the irrigated formation and the change in the formation porosity, and the evaluation criteria for the slurry grouting effect are given.

[0059] The grouting process of this embodiment is visualized: based on the simulated structure of the overburden layer, fused quartz sand and pore fluid with matching refractive index are prepared, and the proportions of the various components of the pore fluid are adjusted to make the simulated structure of the overburden layer visible. During the slurry injection process, the migration law of the contact front between the slurry and the formation can be reflected, and the diffusion form and diffusion range of the slurry can be observed in real time.

[0060] This embodiment can simulate a wide-graded covering layer receiving body: by selecting fused quartz sand of five typical covering layer particles through particle screening, the particles are mixed and stirred according to a certain particle grading to simulate a variety of covering layer grading curves, thereby achieving the purpose of simulating the physical properties of the original wide-graded covering layer on the basis of retaining the particle characteristics.

[0061] This embodiment is suitable for the study of various grouting pressures and various slurry diffusion forms: by setting a reinforcement frame 21 on the outside of the model box 1, the model box 1 can withstand a greater grouting pressure to meet the airtightness and stability requirements of the model box 1 under various grouting pressures, which is sufficient to support the study of various diffusion forms of grouting slurry.

[0062] This embodiment adopts digital image measurement technology: the camera 3 is used to collect images of slurry diffusion and stratum movement during the grouting process, and the non-contact PIV velocity measurement technology is combined to improve the grouting measurement accuracy, analyze the slurry front migration in the early, middle and late stages of grouting under a certain pressure, as well as the slurry vein diffusion morphology and diffusion distance, to provide a quantitative analysis basis for the slurry injection situation.

[0063] This embodiment can provide a new way to evaluate the grouting effect: based on the PIV velocity measurement technology, the relative displacement of the grouting formation under the action of slurry pressure is studied, the porosity change is calculated, and the influence of formation compaction and slurry on the improvement of the anti-seepage effect of the wide-graded covering layer under different slurry pressures is explored. At the same time, the grouting effect can be evaluated in real time and quantitatively.

[0064] This example explores the slurry flow and diffusion morphology based on the wide-graded covering layer under the grouting pressure, and verifies the feasibility of using visualization materials + digital image analysis technology to study the grouting problem of the wide-graded covering layer; the collected data are used to analyze the spatial and temporal distribution characteristics of slurry migration in the wide-graded covering layer, explore the diffusion mechanism of the grouting of the wide-graded covering layer, and comprehensively evaluate the reinforcement effect of grouting on the covering layer.

[0065] This embodiment constructs a double-circulation pipeline for slurry flow and adopts stable slurry materials, which can reduce the segregation of slurry during the grouting process while retaining the real diffusion characteristics of the slurry; the control is simple, and the slurry injection pressure can be controlled by adjusting the valve operation; the maximum grouting pressure in the pipeline is controlled by adjusting the pressure-limiting valve 10, thereby simulating various diffusion forms and progressive diffusion processes of the slurry; the measurement accuracy is high, the reliability is strong and the degree of automation is high, and the measurement data such as the formation lift and grouting pressure in the test device can be displayed, monitored and stored in real time; based on the digital image system, the time-series image of the visualized diffusion of the slurry front during the grouting process can be accurately obtained, thereby replacing the traditional monitoring method of the built-in sensor.

[0066] Embodiment 2

[0067] A test method using the cover grouting visualization test device 100 of the first embodiment includes:

[0068] Prepare transparent soil for simulating the structure of the covering layer and put it into the model box 1, and prepare slurry;

[0069] The preparation of transparent soil for the simulated structure of the covering layer mainly includes the following steps: (1) pre-washing and drying the fused quartz sand; (2) weighing and mixing 50 kg of fused quartz sand of various particle sizes in batches according to the predetermined gradation, and mixing and stirring; (3) preparing the pore fluid, and letting the prepared pore fluid stand for about 3 minutes at room temperature 25°C; (4) weighing the fused quartz sand and the pore fluid in a bucket and stirring and mixing them. After the mixing is completed, they are loaded into the model box 1 in layers and pre-pressed in layers; (5) after the pre-pressing is completed, the reinforcement frame 21 is vibrated to remove large bubbles in the simulated structure of the covering layer, and some fine bubbles are retained for subsequent use as tracer bubbles; (6) standing in the air for 4 to 8 hours;

[0070] The slurry uses a stable slurry with a water-cement ratio of 0.8, and uses the third-generation polycarboxylate water reducer and sodium-based bentonite materials. The ratio of water, cement, bentonite, and water reducer is 1:0.8:0.03:0.05;

[0071] Check the smoothness and tightness of the switches of each valve, and check the integrity of each signal connection line; turn on the laser 2, adjust the power and incident angle of the laser 2 to form a high-quality speckle field, and ensure that the laser section, the center line of the model box 1 and the center line of the hollow tube 19 coincide with each other; adjust the camera 3 and the camera 4 so that the shooting surface has a good imaging effect;

[0072] Prepare stable cement slurry, stir it and place it in the slurry storage structure, connect all pipelines, adjust the opening of the pressure limiting valve 10 to adjust the maximum grouting pressure according to the test plan, open the first valve 7, and grouting, gradually pressurize to the specified pressure using the pressure-stabilizing grouting method, and after the slurry vein expansion shape is stable, screen the slurry for 3 minutes;

[0073] Camera 3 is used to capture the speckle field generated by the interaction between the laser and the simulated structure of the covering layer, and camera 4 is used to capture the grouting diffusion image;

[0074] Data processing: After the grouting flow rate is stable, the PIV velocity measurement technology is used to collect the deformation data of the corresponding position (obtained by processing the photos taken by the camera) as the initial value of the deformation. The displacement sensor collects data according to the set acquisition frequency and transmits it to the data acquisition instrument. The data management and analysis system in the computer reads the data of the data recorder, and draws the relationship curves of grouting pressure, grouting rate, diffusion distance, and formation deformation based on the monitoring data (formation lift, grouting pressure, formation pressure, and image data after PIV processing) to study the law of grouting on the disturbance of the overburden. Based on digital image processing technology, combined with the formation structure characteristics (tortuosity, porosity), the relationship between slurry diffusion and pressure during the grouting process is obtained, and predicted and analyzed. The abnormal value is given in real time by comparing the predicted value with the monitored value to determine the maximum disturbance of grouting and the timing of action.

[0075] Model cleaning and recycling: After the grouting diffusion test is completed, close the first valve 7, the second valve 9, the third valve 14 and the fourth valve 17, and disconnect the power supply of the grouting pump 6 and other electrical appliances. Remove the pipelines, rinse the grouting pump 6 and the pipelines with clean water to prevent the slurry from clogging the pipelines; use a shovel to shovel out the transparent soil and the slurry in the model box 1, and fully clean the inner wall of the model box 1; after the overall cleaning is completed, remove the pipelines and the connecting bolts at the corresponding positions, remove the filter plate 20 and the filter structure, and clean them for the next model test.

[0076] In this embodiment, according to the simulation test requirements and engineering experience, appropriate cover layer parameters (quartz sand particle grading, particle shape, particle size), transparent soil preparation (selecting the appropriate quartz sand particle size corresponding to the pore fluid ratio), grouting hole diameter, slurry ratio (the respective ratios of cement, water, and clay), and a model test scheme corresponding to a combination of construction parameters (grouting pressure, pulsation frequency) are set to study the relationship between grouting pressure and porosity ratio, cover layer compressive resistance, and permeability.

[0077] The series of model test schemes are numbered one by one, and model tests are carried out in batches according to the numbers to study the diffusion law of the grouting pressure mode on the overburden slurry under different formation parameter conditions and the disturbance law of the grouting on the surrounding formations. After the transparent soil grouting test is completed, the model box 1 is cleaned, reassembled and the model test is carried out according to the series of model test schemes to improve the utilization rate of the device.

[0078] Then, combining discrete element modeling technology, a discrete element test model of overburden grouting was established according to the particle grading of the simulated structure of the overburden and compared with the experiment.

[0079] Based on the results of a series of model tests, the matching performance of the transparent soil cover grouting effect and the orifice grouting process is evaluated, and the reasonable grouting pressure and grouting materials are determined according to the influence of the cover layer parameters and the grouting control pressure on the slurry diffusion performance. According to the law of the grouting disturbance on the surrounding strata, the appropriate grouting pressure, grouting rate and control strategy are determined to reduce the grouting disturbance on the surrounding strata.

[0080] After all tests were carried out according to the model test plan, the corresponding test results were analyzed to study the effects of formation parameters (tortuosity, porosity) and grouting pressure control strategies (grouting pressure, pulsation frequency) on slurry diffusion and the strength of stone bodies (cement stone formed after slurry solidification and high-strength mixture formed by cement and transparent soil material wrapped in cement hydration), providing a basis for adjusting grouting materials and processes.

[0081] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A visual test device for overburden grouting, characterized in that: include: A model box and a grouting structure, wherein the model box is used to hold a cover layer simulation structure, the cover layer simulation structure is a transparent structure, a grouting hole is provided in the model box, the grouting hole is used to connect with the grouting structure, the grouting structure pours slurry into the model box through the grouting hole, a laser is provided above the model box, a camera is provided on one side of the model box, the camera is electrically connected to a computer, a camera is provided on the other side of the model box, the camera is electrically connected to a computer, the laser is used to emit laser, a speckle field is generated after the laser interacts with the cover layer simulation structure, the camera is used to shoot the speckle field, and the camera is used to shoot the grouting diffusion.

2. The visual test device for covering grouting according to claim 1, characterized in that: The cover layer simulation structure is made of quartz sand particles and pore fluid, the pore fluid is made of white oil and isododecane, and the ratio between the white oil and the isododecane makes the refractive index of the pore fluid the same as the refractive index of the quartz sand particles.

3. The visual test device for covering grouting according to claim 1, characterized in that: The vertical line of the camera is perpendicular to the axis of the laser source of the laser, and the intersection of the vertical line of the camera and the axis of the laser source of the laser is located in the area where the cover layer simulation structure is located in the model box.

4. The visual test device for covering grouting according to claim 1, characterized in that: The grouting structure includes a grouting pump, a first valve and a first pressure transmitter connected through a grouting pipe, the grouting pump is used to transport the slurry in the grouting storage structure, the first pressure transmitter is connected to the grouting hole, the first pressure transmitter is used to monitor the pressure of the slurry entering the grouting hole, the first pressure transmitter is electrically connected to a data recorder, and the data recorder is electrically connected to a computer.

5. The visual test device for covering grouting according to claim 4 is characterized in that: A second valve, a pressure limiting valve, a second pressure transmitter and a flow meter are also provided on the grout inlet pipe between the grouting pump and the first valve, and the second pressure transmitter and the flow meter are electrically connected to the data recorder; It also includes a slurry return pipe, one end of which is connected to the slurry inlet pipe between the flow meter and the first valve, the other end of which is connected to the grouting pump, and a third valve is provided on the slurry return pipe; It also includes a regulating pipe, one end of which is connected to the grouting pump, and the other end of which is connected to the grouting pipe between the grouting pump and the second valve. A fourth valve is also provided on the regulating pipe.

6. The visual test device for covering grouting according to claim 1, characterized in that: An osmometer is arranged in the model box, and a displacement sensor is also arranged on the model box. The osmometer and the displacement sensor are both electrically connected to a data recorder, and the data recorder is electrically connected to a computer.

7. The visual test device for covering grouting according to claim 1, characterized in that: The model box is made of a transparent material, a plurality of support rods are arranged between the front wall and the rear wall of the model box, and a reinforcement frame is arranged outside the model box.

8. The visual test device for covering grouting according to claim 1, characterized in that: A hollow tube is arranged between the front wall and the rear wall of the model box, and the hollow tube is located at the center of the model box. One end of the hollow tube is used to be connected with the grouting structure, and a plurality of grouting holes are opened in the middle part of the hollow tube along the circumference of the hollow tube, and the grouting holes are used to communicate with the model box.

9. The visual test device for covering grouting according to claim 1, characterized in that: A filter plate is provided on the model box, and the filter plate is located above the cover layer simulation structure. The pore size of the filter plate can allow porous fluid to pass through. An overflow hole is opened on the side wall of the model box, and the overflow hole is connected to a recovery box. A filter structure is provided in the recovery box. After passing through the filter plate, the porous fluid can enter the overflow hole and then enter the recovery box.

10. A test method using the cover grouting visualization test device according to any one of claims 1 to 9, characterized in that: include: Formulate cover layer simulation structure and slurry; Turn on the laser and adjust the laser power and incident angle; Adjust the grouting pressure of the grouting structure and carry out grouting; A camera is used to capture the speckle field generated by the interaction between the laser and the simulated structure of the covering layer, and a camera is used to capture the grouting diffusion image.

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