Soft rock structural surface permeation grouting evolution analysis method

Abstract

The invention relates to the technical field of rock mass engineering, in particular to a soft rock structural surface permeation grouting evolution analysis method which comprises the following steps: performing a steady-state shear thinning inversion test on target slurry by using a rotational rheometer to obtain slurry performance parameters; a permeation grouting displacement test is conducted on the soft rock structural surface, and grouting parameters in the grouting process are obtained; determining grouting main section parameters of the soft rock structural surface, and constructing a grouting diffusion numerical value prediction model based on the grouting main section parameters; based on the slurry performance parameters, the grouting parameters and the grouting diffusion numerical value prediction model, establishing a simulation model of the target slurry; and performing test-simulation parameter comparison on the permeation grouting displacement test and the simulation model, and determining a grouting evolution characterization model for analyzing grouting flow pattern evolution and diffusion fluidization. According to the method, the accurate simulation model and the grouting evolution characterization model are established and optimized by combining actual measurement parameters in the test, so that the grouting process is optimized, and the engineering safety and economy are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mass engineering, and particularly relates to a method for analyzing the evolution of permeation grouting of soft rock structural planes. Background Art

[0002] The characteristics of unsteady diffusion and fluidization of grout in weakly cemented soft rock fractures are important research contents in geotechnical engineering and geological engineering, mainly involving the diffusion behavior and fluidization phenomenon of grout in weakly cemented soft rock fractures. Weakly cemented soft rock refers to rock with relatively low cementation strength, which is commonly found in sedimentary rocks or weathered rocks.

[0003] The research on the characteristics of unsteady diffusion and fluidization of grout in weakly cemented soft rock fractures aims to improve the application of grouting technology in weakly cemented soft rock, optimize grouting parameters, analyze the effects of grout diffusion and fluidization in actual engineering, summarize experience, optimize grouting technology, and enhance engineering safety and economy. At present, in this research and application work, on the one hand, there is relatively little research and application transformation work on the characteristics of unsteady diffusion and fluidization of grout in weakly cemented soft rock fractures. On the other hand, the current research and application work lack a sufficient understanding of the laws and mechanisms of grouting diffusion behavior and flow pattern evolution, and lack the analysis of the rheological shear characteristics of grout, resulting in relatively low levels of grouting technology, engineering safety, and economy in engineering applications. Summary of the Invention

[0004] In order to solve the technical problems that the grouting technology, engineering safety, and economy for weakly cemented soft rock are all relatively low, the purpose of the present invention is to provide a method for analyzing the evolution of permeation grouting of soft rock structural planes, and the specific technical solutions adopted are as follows:

[0005] The present invention provides a method for analyzing the evolution of permeation grouting of soft rock structural planes, and the method includes:

[0006] Performing an inversion test on the target grout for steady-state shear thinning using a rotational rheometer to obtain the grout performance parameters;

[0007] Performing a permeation grouting displacement test on the soft rock structural plane to obtain the grouting parameters during the grouting process;

[0008] Determining the main grouting section parameters of the soft rock structural plane, and constructing a numerical prediction model for grouting diffusion based on the main grouting section parameters;

[0009] Based on the grout performance parameters, grouting parameters, and the numerical prediction model for grouting diffusion, establishing a simulation model for the target grout;

[0010] Comparing the parameters of the permeation grouting displacement test and the simulation model to determine a grouting evolution characterization model for analyzing the evolution of grouting flow pattern and diffusion fluidization.

[0011] Further, based on the slurry performance parameters, grouting parameters, and grouting diffusion numerical prediction model, a simulation model of the target slurry is established. After that, it further includes:

[0012] Using the grouting parameters and the Rosin-Rammler distribution function, the simulation model is adjusted to obtain a corrected simulation model.

[0013] Further, the inversion test of steady-state shear thinning of the target slurry is carried out using a rotational rheometer to obtain the slurry performance parameters, including:

[0014] The target slurry is subjected to rheological tests using a rotational rheometer after standing for each preset duration to obtain the shear stress-shear rate curve;

[0015] Using a preset Bingham model to fit the shear stress-shear rate curve and inversely obtain the slurry performance parameters;

[0016] Among them, the slurry performance parameters include yield stress and plastic viscosity.

[0017] Further, the rheological test includes pre-shear test and data acquisition; the step of subjecting the target slurry to rheological tests using a rotational rheometer after standing for each preset duration includes:

[0018] During the pre-shear test, control the rotational speed of the rotational rheometer to reach the first preset rotational speed from rest within the first preset time period, and then decrease from the first preset rotational speed to rest;

[0019] During the data acquisition process, control the rotational speed of the rotational rheometer to reach the second preset rotational speed from rest within the second preset time period, and then decrease from the second preset rotational speed to rest.

[0020] Further, the permeation grouting displacement test on the soft rock structural plane is carried out to obtain the grouting parameters during the grouting process, including:

[0021] Prepare a soft rock specimen and fix the soft rock specimen in a clamping steel cylinder;

[0022] Connect a confining pressure loading device and a grouting pipeline to the end of the clamping steel cylinder for carrying the soft rock specimen, and arrange the slurry outlet hole at the geometric center of the clamping steel cylinder;

[0023] Use the confining pressure loading device to apply confining pressure to the soft rock specimen, and flow the target slurry stored in the liquid storage tank into the soft rock specimen through the grouting pipeline;

[0024] During the permeation grouting displacement test, the grouting parameters during the grouting process are monitored in real time;

[0025] Among them, the grouting parameters include pressure, flow rate, and grouting diffusion form.

[0026] Furthermore, the preparation of the soft rock sample comprises:

[0027] Processing the soft rock sample into a cylindrical specimen, and adjusting the end surface of the cylindrical specimen to a preset unevenness;

[0028] The cylindrical specimen is cut along the axial direction to form one or two parallel through-going crack surfaces, and the cut cylindrical specimen is soaked in water until it reaches a saturated state.

[0029] Furthermore, the determination of the main section parameters of the grouting of the soft rock structural surface includes:

[0030] The soft rock specimen after grouting consolidation is subjected to X-ray tomography;

[0031] The preset geometric feature recognition algorithm is used to determine the main section parameters of the grouting from the scanned soft rock sample image;

[0032] Among them, the main cross-sectional parameters of grouting include the ellipticity, roughness and major axis inclination of the particles.

[0033] Furthermore, the grouting diffusion numerical prediction model is constructed based on the grouting main section parameters, including:

[0034] A numerical prediction model for grouting diffusion is constructed using the main section parameters, particle content and gradation curve of grouting.

[0035] Furthermore, the simulation model of the target slurry is established based on the slurry performance parameters, grouting parameters and the grouting diffusion numerical prediction model, including:

[0036] The grouting diffusion numerical prediction model and the morphological diameter distribution function are used to fit the measured data of slurry particle distribution, and the particle flow calculation of the slurry performance parameters and grouting parameters is performed to obtain the simulation model of the target slurry.

[0037] Furthermore, the test-simulation parameter comparison between the permeable grouting displacement test and the simulation model to determine the grouting evolution characterization model for analyzing the grouting flow pattern evolution and diffusion fluidization includes:

[0038] Based on the slurry performance parameters of the target slurry and the main section parameters of the grouting, different grouting parameters are integrated to determine the slurry diffusion fluidization characterization corresponding to the permeation grouting displacement test and the simulation model respectively;

[0039] The slurry diffusion fluidization characterization based on the penetration grouting displacement test was compared and verified with the slurry diffusion fluidization characterization of the simulation model, and a grouting evolution characterization model for analyzing the grouting flow pattern evolution and diffusion fluidization was obtained.

[0040] The present invention has the following beneficial effects:

[0041] Starting from the physical tests of permeation grouting for weak cemented soft rock structural planes and numerical and simulation modeling, this invention combines various measured parameters in the tests to establish and optimize more accurate simulation models and specific grouting evolution characterization models. It improves the deficiencies in the research on the non-steady diffusion mechanism of grout and the analysis of the rheological shear characteristics of grout in current related technologies. From the perspective of studying the performance of dense slurries, it reveals the micro-mesoscopic water-holding structures and the evolution mechanism of dense-phase flow, which helps to more deeply understand the grouting diffusion behavior and the laws and mechanisms of flow pattern evolution, providing more reliable underlying mechanism support and specific engineering application support for optimizing the grouting process and enhancing project safety and economy, and can effectively improve the actual application effect of grouting technology in weakly cemented soft rocks. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0043] Figure 1 It is a flowchart of the steps of a method for analyzing the evolution of permeation grouting of a soft rock structural plane provided by an embodiment of the present invention;

[0044] Figure 2 It is a refined flowchart of step S1 in a method for analyzing the evolution of permeation grouting of a soft rock structural plane provided by an embodiment of the present invention;

[0045] Figure 3 It is a refined flowchart of step S2 in a method for analyzing the evolution of permeation grouting of a soft rock structural plane provided by another embodiment of the present invention;

[0046] Figure 4 It is a refined flowchart of step S3 in a method for analyzing the evolution of permeation grouting of a soft rock structural plane provided by an embodiment of the present invention;

[0047] Figure 5 It is a schematic diagram of the reconstruction of the CT tomographic scan and the reconstructed fracture grouting diffusion channel model related to the embodiment scheme of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following specifically describes, in conjunction with the accompanying drawings and preferred embodiments, a method for analyzing the evolution of permeation grouting of soft rock structural planes proposed according to the present invention, including its specific implementation manner, structure, features and effects. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0050] The following specifically describes the specific solution of a method for analyzing the evolution of permeation grouting of soft rock structural planes provided by the present invention in conjunction with the accompanying drawings.

[0051] For a method for analyzing the evolution of permeation grouting of soft rock structural planes provided by the present invention, please refer to Figure 1 , which shows the flow chart of the steps of the method for analyzing the evolution of permeation grouting of soft rock structural planes provided by an embodiment of the present invention.

[0052] The method includes:

[0053] Step S1, performing an inversion test on the target slurry for steady-state shear thinning using a rotational rheometer to obtain slurry performance parameters;

[0054] In this embodiment, the target slurry can adopt the traditional cement slurry commonly used in on-site pre-grouting, and the slurry material uses ordinary Portland cement and ordinary drinking water, and cement slurries with different water-cement ratios are prepared at room temperature.

[0055] Samples of the target slurry with different ratio parameters are grouped, and the slurry parameters are tested using a rotational rheometer. Based on the slurry rheological parameters and water-holding parameters, an inversion test on the target slurry for steady-state shear thinning is performed to obtain the slurry rheological characteristics, that is, the slurry performance parameters, providing basic data support for subsequent model construction.

[0056] Specifically, the dynamic yield stress and plastic viscosity are the main rheological performance parameters of the target slurry (here referring to the cement paste). The steady-state method is a common method for testing the dynamic yield stress and plastic viscosity of cement paste. The steady-state method refers to applying one of the variables such as changing shear rate, rotational speed, and shear stress to the freshly mixed cement paste, and the freshly mixed cement makes responses of shear stress, torque, shear rate, and rotational speed respectively. These variables can be converted into each other, and a rheological test method is required to keep the cement paste in a shear equilibrium state during data acquisition.

[0057] Regarding the rheological properties of the slurry, slump and bleeding rate tests and rheological shear tests are adopted. For the rheological tests, a general rotary rheometer is used to measure the rheological properties of the slurry. Two methods, namely fixed rate and increasing rate, are adopted to obtain the output shear stress-shear rate curve by collecting data, and rheological parameters such as the yield stress and viscosity of the target slurry at different times, that is, the slurry performance parameters, are obtained.

[0058] Specifically, please refer to Figure 2 , the step S1 includes:

[0059] Step S11, rheologically test the target slurry with a rotary rheometer after standing for each preset duration to obtain a shear stress-shear rate curve;

[0060] More specifically, the rheological test includes a pre-shear test and data collection; the step S11 includes:

[0061] During the pre-shear test, control the rotation speed of the rotary rheometer to increase from rest to a first preset rotation speed within a first preset time period, and then decrease from the first preset rotation speed to rest;

[0062] During the data collection process, control the rotation speed of the rotary rheometer to increase from rest to a second preset rotation speed within a second preset time period, and then decrease from the second preset rotation speed to rest.

[0063] In a specific embodiment, the specific steps of the rheological property test (inversion test of steady-state shear thinning) include:

[0064] After pouring the target slurry into a beaker, rheologically test it at each preset duration after standing (such as 0 min, 5 min, 10 min, 15 min, 22 min, 30 min, 40 min, 50 min). The rheological test includes two test processes: pre-shear and data collection.

[0065] During pre-shear, control the rotation speed of the rotary rheometer to increase from 0 r / min to a first preset rotation speed (such as 80 r / min) within a first preset time period (such as 20 s), and then decrease to 0 r / min within the first preset time period (such as 20 s). The purpose of pre-shear is to disperse the slurry so that each group of target slurries has a roughly the same shear state before rheological data collection. During the data collection process, control the rotation speed to increase from 0 r / min to a second preset rotation speed (such as 120 r / min) within a second preset time period (such as 60 s), and then decrease to 0 r / min within the second preset time period. Read one data point per second, a total of 120 data points are measured, and the upward and downward curves of shear stress-shear rate are obtained.

[0066] Step S12: Fit the shear stress-shear rate curve using a preset Bingham model and invert to obtain the slurry performance parameters;

[0067] Inversion analysis: For the fitting of the non-linear rheological curve (shear stress-shear rate curve) of cement-based materials, the preset modified Bingham model is more applicable. Select the modified Bingham model to fit the test data in the curve and invert to obtain slurry performance parameters such as dynamic yield stress and plastic viscosity.

[0068] The expression of the modified Bingham model is: τ = τ0 + η p γ + cγ 2

[0069] In the formula, τ is the shear stress, unit Pa, τ0 is the dynamic yield stress (Pa), η p is the plastic viscosity (Pa·s), c is the fitting constant, unit Pa·s 2 , γ is the shear rate, unit s -1 .

[0070] Step S2: Conduct a permeability grouting displacement test on the soft rock structural plane to obtain the grouting parameters during the grouting process;

[0071] Based on the obtained slurry performance parameters, design and conduct a permeability grouting displacement test on the weak cemented soft rock structural plane, and monitor and record in real time the grouting parameters such as pressure, flow rate, and grouting diffusion form during the grouting process.

[0072] For the permeability grouting displacement test, the relevant concepts and their functions are as follows:

[0073] The permeability grouting displacement experiment is an experimental technique used to study the flow of slurry in rock and soil fractures or pores and the displacement of the original fluid. Permeability grouting injects solidifying materials such as cement slurry into the pores or cracks of rock and soil through pressure to form reinforced rock and soil materials with higher strength and lower permeability coefficient.

[0074] During the grouting reinforcement in the test process, the multi-phase mixed gelling slurry (here refers to the target slurry, that is, cement slurry) is pressed into the rock mass fractures for filling and pore water displacement. During the diffusion process, the slurry is subjected to continuous shear action, accompanied by continuous changes in the microstructure and water migration, and finally cements and forms in the rock mass fractures.

[0075] Specifically, please refer to Figure 3 , the step S2 includes:

[0076] Step S21: Prepare a soft rock specimen and fix the soft rock specimen in the clamping steel cylinder;

[0077] More specifically, for how to prepare a soft rock specimen, it includes:

[0078] Process the soft rock specimen into a cylindrical specimen, and adjust the end face of the cylindrical specimen to a preset unevenness;

[0079] Cut the cylindrical specimen along the axial direction to form 1 or 2 parallel and penetrating fracture surfaces, and soak the cut cylindrical specimen in water until it reaches a saturated state.

[0080] In a specific example, it may include:

[0081] The specimen can be processed into a cylindrical specimen with a diameter of 50 mm and a height of 100 mm, and ensure that the unevenness of the specimen end face reaches the preset unevenness, and the preset unevenness is less than 0.02 mm. Cut the cylindrical specimen, cut the cylindrical specimen along its axial direction to form 1-2 parallel and penetrating fracture surfaces. Soak the cut cylindrical specimen in water 24 hours in advance to reach a saturated state, set different test conditions, confining pressure control groups (5, 10, 15 MPa), slurry flow rate control groups (3, 5, 7 mL·min -1 ) and fracture number control groups (1, 2), so as to carry out the osmotic grouting test on fractured sandstone. The above specific test parameters can be adjusted according to needs, and only examples are given here.

[0082] Step S22, connect a confining pressure loading device and a grouting pipeline to the end of the clamping steel cylinder for carrying the soft rock specimen, and arrange the slurry outlet holes at the geometric center of the clamping steel cylinder;

[0083] Step S23, use the confining pressure loading device to apply confining pressure to the soft rock specimen, and let the target slurry stored in the liquid storage tank flow into the soft rock specimen through the grouting pipeline;

[0084] Step S24, during the osmotic grouting displacement test, monitor the grouting parameters during the grouting process in real time;

[0085] Among them, the grouting parameters include pressure, flow rate and grouting diffusion form.

[0086] The osmotic grouting displacement test can be carried out on the Ztr-205 pore rock grouting test system, and the specific test steps may include:

[0087] (1) Fix the specimen with a small clamping steel cylinder, connect a confining pressure loading device and a grouting pipeline to its end. To ensure uniform slurry diffusion, arrange the slurry outlet holes at the geometric center of the clamping steel cylinder, and arrange 3 slurry outlet holes with a diameter of 3 mm along the radial direction at the top of the grouting pipe;

[0088] (2) Arrange stress and displacement sensors around the specimen, monitor the changes of the internal stress field and displacement field of the structural plane during the slurry diffusion process, open the confining pressure pump, set the test confining pressure, and realize the confining pressure loading on the specimen through the confining pressure pump;

[0089] (3) Pour the micro-expansion solidified grout prepared in a certain proportion into the liquid storage tank, turn on the constant-flow displacement pump, set the grouting slurry flow rate, and conduct the permeation grouting test;

[0090] (4) When the slurry flows out stably at the outlet of the grouting pipeline, stop the permeation grouting test, and turn off the constant-flow displacement pump and the confining pressure system.

[0091] Through the permeation grouting test, obtain and analyze grouting parameters such as the slurry injection volume, effective grouting time, and slurry filling rate of the rock under different confining pressures, different slurry flow rates, different flow rates, and different numbers of fractures.

[0092] Step S3, determine the grouting main section parameters of the soft rock structural plane, and construct a numerical prediction model for grouting diffusion based on the grouting main section parameters;

[0093] Specifically, please refer to Figure 4 , the said step S3 includes:

[0094] Step S31, conduct X-ray tomography on the soft rock specimen after grouting consolidation;

[0095] Step S32, use a preset geometric feature recognition algorithm to determine the grouting main section parameters from the scanned soft rock specimen image;

[0096] Please refer to Figure 5 for illustration. Conduct X-ray tomography on the soft rock specimen after 24 hours of grouting consolidation. Through geometric feature recognition and statistical analysis of particle distribution characteristics, collect grouting main section parameters such as the ellipticity, roughness, and long axis inclination angle of the grouting main section to reconstruct the numerical model of the seepage channel of the soft rock structural plane, and obtain the numerical prediction model for grouting diffusion.

[0097] Ellipticity refers to the degree of elliptical shape of particles. The lengths of the long axis and short axis of particles in the grouting main section can be measured through existing geometric feature recognition algorithms, and then the ellipticity can be calculated.

[0098] Roughness is used to evaluate the surface morphological characteristics of particles. By uniformly generating line segments within a 360° range and recording the distribution length of particles on each line segment and the corresponding line segment length, the roughness coefficient of particles can be calculated.

[0099] The long axis inclination angle refers to the angle between the long axis of particles and the seepage direction. The long axis inclination angle is crucial for understanding the directionality of the seepage channel and the arrangement of particles. Through the X-ray tomography image, the long axis direction of particles can be identified, and the angle between it and the seepage direction can be calculated. According to the stacking characteristics of particles in the plane, the long axis inclination angle can be directly statistically analyzed.

[0100] X-ray tomography can directly obtain all the original structural characteristics of particles without removing the particles from the specimen.

[0101] Furthermore, to identify the geometric characteristics of the main grouting section, a geometric feature identification algorithm - GIM (geometry identification method) can be used. The GIM method can accurately identify parameters such as ellipticity, roughness, and long-axis inclination angle. Analyze the CT images using the GIM method to extract the main grouting section parameters including the ellipticity, roughness, and long-axis inclination angle of the particles.

[0102] Identifying the ellipticity of particles: Obtain the minimum circumscribed ellipse of the particles, the long-axis value and short-axis value corresponding to the ellipse through the ellipse wrapping method. The formula for calculating the ellipticity of particles is:

[0103]

[0104] In the formula: L y represents the long axis of the ellipse, L x represents the short axis of the ellipse, in meters, E represents the ellipticity of the particles, and m represents the particle number.

[0105] Identifying the roughness of particles: Discretize the ellipse contour into n segments by angle equal division, starting from the center O of the ellipse and ending at the discrete point P of the ellipse contour. Construct the line segment OP, the intersection point of the line segment OP and the particle contour line is Q, and construct the line segment PQ. The formula for calculating the roughness of particles:

[0106]

[0107] In the formula, L oP , L PQ are the lengths of the line segments OP and PQ respectively, in meters, R represents the roughness of the particles, n is the discrete value of a single particle, and m represents the particle number.

[0108] In one embodiment, the method for constructing a grouting diffusion numerical prediction model based on the main grouting section parameters includes:

[0109] Construct a grouting diffusion numerical prediction model using the main grouting section parameters, particle content, and grading curve.

[0110] Use the geometric reconstruction method of Open3D software to process the images obtained by CT scanning (soft rock specimen images) and extract the geometric parameters of the cracks. Construct a numerical prediction model based on parameters such as the ellipticity and roughness of the particles and experimental data.

[0111] During the model construction process, the main grouting section parameters such as ellipticity and roughness obtained by CT tomography are used. Based on the model geometric profile and porosity parameters, the particle content is determined. Then, the short-axis particle size is determined according to the grading curve, and the corresponding particle model is generated according to the geometric characteristic parameters. Combining the above, the main grouting section parameters, particle content and grading curve, a numerical prediction model for grouting diffusion is constructed.

[0112] Step S4, based on the slurry performance parameters, grouting parameters and the numerical prediction model for grouting diffusion, establish a simulation model for the target slurry;

[0113] Specifically, the step S4 includes:

[0114] Use the numerical prediction model for grouting diffusion and the morphological diameter distribution function to fit the measured data of the slurry particle distribution, and conduct particle flow calculations on the slurry performance parameters and grouting parameters to obtain the simulation model of the target slurry.

[0115] Taking the ANSYS-Fluent and COMSOL software platforms as the simulation tools for grouting diffusion numerical values, using the numerical prediction model for grouting diffusion and adopting the morphological diameter distribution function to fit the measured data of the slurry particle distribution, dynamically couple the slurry performance parameters and grouting parameters, and establish a flow field analysis model based on the multiphase flow theory and particle flow dynamics theory to conduct simulation inversion of the permeation grouting diffusion test. Introduce the refined drag force model into the slurry diffusion fluidization system and permeability coefficient prediction model through the Rosin-Rammler function to improve the calculation convergence accuracy, obtain the preliminary simulation model, and further conduct particle flow calculations on the slurry performance parameters and grouting parameters to determine parameters such as the flow pattern evolution and phase volume fraction at different times, and establish, verify and optimize the simulation model of the target slurry.

[0116] Conduct particle flow calculations on different target slurry performance parameters and grouting parameters, specifically including:

[0117] Select the DDPM (Denoising Diffusion Probabilistic Models) in the Euler-Lagrange method that can model the collision process of particles, track particle packets, and has high calculation efficiency and accuracy.

[0118] In this simulation, use the CFD-DDPM coupling method combined with Euler-Lagrange hydrodynamics for further analysis. During the transportation simulation process, use the slurry as the dense discrete phase for particle flow tracer calculation, and monitor the movement trajectories of particles with different particle sizes and the distribution of the key areas for fracture filling.

[0119] During the numerical calculation process, the cement paste is simplified to a homogeneous paste. The following laws of mass conservation, momentum conservation, and energy conservation of fluids are followed.

[0120] Mass conservation equation of fluid:

[0121]

[0122] In the formula, α f is the volume fraction of the fluid phase, ρ f represents the density of the fluid phase, and U f represents the velocity vector.

[0123] Momentum conservation equation of fluid:

[0124]

[0125] In the formula, τ represents the viscous stress tensor, and F pf represents the force exerted by each particle on the fluid; other parameters are the same as above.

[0126] Solid-phase control equation:

[0127]

[0128]

[0129] In the formula, m i , U p,i , I i and ω i respectively represent the mass, velocity, inertial motion, and rotational velocity of particle i, and F c,ij , F d,ij and T ij respectively represent the contact force between particles, viscous damping force, and torque between particles i and j, and F c,iw , F d,iw , T iw are respectively the contact force, viscous damping force, and torque between particle i and the rock, and F f,i represents the force acting on particle i through the fluid, and other parameters are the same as above.

[0130] Since the solid particle content in the cement slurry is relatively high, the Ergun equation suitable for dense particle flow is adopted. The drag force of the fluid on the particles can be expressed as:

[0131] F p = m p D(v f - v p )

[0132]

[0133] In the formula, F p represents the drag force of the fluid on the particle, m p represents the particle mass, D represents the drag parameter, v f and v p respectively represent the liquid velocity and the particle velocity, ρ p represents the particle density, ρ f represents the fluid density, θ p represents the particle mass fraction, r p represents the particle diameter.

[0134] Cement slurry is a non-Newtonian fluid, and its rheological properties are applicable to the Bingham model. It only starts to flow when the critical value of the minimum shear stress is reached. The expression is:

[0135]

[0136] In the formula, τ represents the shear stress, τ0 represents the yield stress, represents the shear rate, and μ represents the slurry viscosity.

[0137] In addition, in another embodiment, after the step S4, the method further includes:

[0138] Using the grouting parameters and the Rosin-Rammler distribution function, adjust the simulation model to obtain a corrected simulation model.

[0139] According to the grouting parameters obtained from the measured results of the grouting displacement test and the Rosin-Rammler distribution function, correct the simulation model to achieve synchronization with the grouting test.

[0140] Specifically, according to the characteristics of the grouting diffusion process, establish an inversion objective function to quantify the difference between the grouting displacement experimental results and the simulation model. The establishment of the objective function needs to comprehensively consider the fracture structure, the diffusion range of the slurry, and the measured experimental data. Here, the Rosin-Rammler distribution function is preferably used.

[0141] Compare and analyze the slurry diffusion behavior obtained from the grouting displacement experiment with the simulation model. Through multiple groups of data obtained by monitoring, verify the accuracy of the simulation model and provide reference data for the improvement of the simulation model.

[0142] Use an iterative optimization algorithm (such as the least squares method, genetic algorithm, etc.) to solve the inversion objective function. Through multiple iterations, gradually obtain the optimal parameters to correct the key parameters in the grouting diffusion process. Combining the inversion analysis results, deeply analyze the evolution characteristics of the slurry in the fractures of the soft rock structural plane.

[0143] Based on the results of the inversion analysis, study the manifold evolution characteristics during the grouting diffusion process. By comparing the flow pattern change rules under different conditions, modify the simulation model to ensure the applicability and accuracy of the simulation model under different conditions.

[0144] Furthermore, modifying the simulation model to achieve synchronization with the grouting test also includes:

[0145] Using the morphological diameter of the curve characteristics corresponding to the Rosin-Rammler particle size distribution function as the main index, combining with the simulation model for parameter modification and inversion analysis, and then analyzing the flow pattern evolution characteristics during the grouting process. The derivation process of the Rosin-Rammler particle size distribution function includes:

[0146] The expression of the Rosin-Rammler distribution function:

[0147] G = 1 - exp[-ad n

[0148] In the formula, G represents the cumulative percentage of particles, d represents the tailings particle size, n represents the Rosin-Rammler distribution index, n > 1, and a represents the particle size coefficient.

[0149] Step S5: Compare the infiltration grouting displacement test with the simulation model in terms of test-simulation parameters to determine the grouting evolution characterization model for analyzing the grouting flow pattern evolution and diffusion fluidization.

[0150] Specifically, step S5 includes:

[0151] Based on the slurry performance parameters of the target slurry and the main grouting section parameters, fuse different grouting parameters to determine the slurry diffusion fluidization characterizations corresponding to the infiltration grouting displacement test and the simulation model respectively;

[0152] Compare and verify the slurry diffusion fluidization characterization of the simulation model based on the slurry diffusion fluidization characterization of the infiltration grouting displacement test to obtain the grouting evolution characterization model for analyzing the grouting flow pattern evolution and diffusion fluidization.

[0153] According to the above comparison and analysis of the parameters and results of the grouting displacement test and the simulation model, further optimize and verify the simulation model. Based on the slurry performance parameters of each target slurry and the main grouting section parameters, fuse the indexes such as grouting pressure, grouting flow rate, and plastic viscosity of different grouting parameters, and combine with the slurry diffusion equation to construct a slurry diffusion fluidization characterization system, and construct a flow pattern evolution index and a slurry diffusion characterization model (grouting evolution characterization model) for different slurries and different parameter schemes, providing a basis for the evaluation of the grouting infiltration and reinforcement effectiveness of weak cemented soft rock structural planes.

[0154] Among them, the expression of the grouting diffusion equation is:​

[0155]

[0156] Where: ΔP is the pressure loss value of the grout during the flow process, and P c represents the grout pressure at the center of the fracture, P is the grout pressure, τ0 is the yield stress, μ is the plastic viscosity, b is the upper wall of the fracture, q is the unit flow rate of the fluid flowing in the fracture, x represents the grout diffusion distance, and r c is the fracture radius.

[0157] Starting from two aspects of physical tests, numerical and simulation simulations of permeation grouting for weak cemented soft rock structural planes, and combining various measured parameters in the tests, this invention establishes and optimizes a more accurate simulation model and a specific grouting evolution characterization model, improves the deficiencies in the research on the non-steady diffusion mechanism of grout and the analysis of the rheological shear characteristics of grout in the current related technologies. From the perspective of studying the performance of dense slurry, it reveals the micro-meso water-holding structure and the evolution mechanism of dense-phase flow, which helps to more deeply understand the grouting diffusion behavior and the laws and mechanisms of flow pattern evolution, provides a more reliable underlying mechanism support and specific engineering application support for optimizing the grouting process and improving engineering safety and economy, and can effectively improve the actual application effect of grouting technology in weakly cemented soft rock.

[0158] It should be noted that the above sequence of embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0159] Each embodiment in this specification is described in a progressive manner. The same or similar parts between each embodiment can be referred to each other, and the key points of each embodiment are the differences from other embodiments.

[0160] The above are only the preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Any equivalent structural / method transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or directly / indirectly applied to other related technical fields, is included in the protection scope of the present invention.

Claims

1. A method for analyzing the evolution of permeation grouting in soft rock structural planes, characterized in that, The method includes: Performing an inversion test on the target slurry for steady-state shear thinning using a rotational rheometer to obtain slurry performance parameters; Performing a permeation grouting displacement test on the soft rock structural plane to obtain grouting parameters during the grouting process; Determining the grouting main section parameters of the soft rock structural plane and constructing a numerical prediction model for grouting diffusion based on the grouting main section parameters; Based on the slurry performance parameters, grouting parameters, and the numerical prediction model for grouting diffusion, establishing a simulation model of the target slurry; Comparing the test-simulation parameters of the permeation grouting displacement test and the simulation model to determine a grouting evolution characterization model for analyzing the evolution of grouting flow pattern and diffusion fluidization.

2. The method for analyzing the evolution of permeation grouting of soft rock structural planes according to claim 1, characterized in that After establishing the simulation model of the target slurry based on the slurry performance parameters, grouting parameters, and the numerical prediction model for grouting diffusion, it further includes: Adjusting the simulation model using the grouting parameters and the Rosin-Rammler distribution function to obtain a modified simulation model.

3. The method for analyzing the evolution of permeation grouting of soft rock structural planes according to claim 1, characterized in that The performing an inversion test on the target slurry for steady-state shear thinning using a rotational rheometer to obtain slurry performance parameters includes: Performing rheological tests on the target slurry using a rotational rheometer after standing for each preset duration to obtain shear stress-shear rate curves; Fitting the shear stress-shear rate curves using a preset Bingham model and inversely obtaining the slurry performance parameters; Among them, the slurry performance parameters include yield stress and plastic viscosity.

4. The soft rock structural plane permeation grouting evolution analysis method according to claim 3, characterized in that The rheological tests include pre-shear tests and data acquisition; the performing rheological tests on the target slurry using a rotational rheometer after standing for each preset duration includes: During the pre-shear test, controlling the rotational speed of the rotational rheometer to reach a first preset rotational speed from rest within a first preset time period and then decreasing from the first preset rotational speed to rest; During the data acquisition process, controlling the rotational speed of the rotational rheometer to reach a second preset rotational speed from rest within a second preset time period and then decreasing from the second preset rotational speed to rest.

5. The method for analyzing the evolution of permeation grouting in soft rock structural planes according to claim 1, characterized in that, The performing a permeation grouting displacement test on the soft rock structural plane to obtain grouting parameters during the grouting process includes: Preparing a soft rock specimen and fixing the soft rock specimen in a clamping steel cylinder; Connecting a confining pressure loading device and a grouting pipeline to the end of the clamping steel cylinder carrying the soft rock specimen, and arranging the slurry outlet hole at the geometric center of the clamping steel cylinder; Using the confining pressure loading device to apply confining pressure to the soft rock specimen and flowing the target slurry stored in the liquid storage tank into the soft rock specimen through the grouting pipeline; During the permeation grouting displacement test, real-time monitoring of the grouting parameters during the grouting process; Among them, the grouting parameters include pressure, flow rate, and grouting diffusion pattern.

6. The method for analyzing the evolution of permeation grouting in soft rock structural planes according to claim 5, wherein, The preparing the soft rock specimen includes: Processing the soft rock specimen into a cylindrical specimen and adjusting the end face of the cylindrical specimen to a preset unevenness; Cutting the cylindrical specimen along the axial direction to form 1 or 2 parallel and penetrating fracture surfaces, soaking the cut cylindrical specimen and reaching a saturated water state.

7. The method for analyzing the evolution of permeation grouting in soft rock structural planes according to claim 1, wherein The determining the grouting main section parameters of the soft rock structural plane includes: Performing X-ray computed tomography on the grouted soft rock specimen; Using a preset geometric feature recognition algorithm to determine the grouting main section parameters from the scanned image of the soft rock specimen. Among them, the main grouting section parameters include the ellipticity, roughness, and long-axis inclination angle of the particles.

8. The method for analyzing the evolution of permeation grouting in soft rock structural planes according to claim 1, characterized in that The construction of the numerical prediction model for grouting diffusion based on the main grouting section parameters includes: Construct a numerical prediction model for grouting diffusion using the main grouting section parameters, particle content, and grading curve.

9. The method for analyzing the evolution of permeation grouting of soft rock structural planes according to claim 1, characterized in that The establishment of the simulation model of the target slurry based on the slurry performance parameters, grouting parameters, and the numerical prediction model for grouting diffusion includes: Use the numerical prediction model for grouting diffusion and the morphological diameter distribution function to fit the measured data of the slurry particle distribution, and conduct particle flow calculations on the slurry performance parameters and grouting parameters to obtain the simulation model of the target slurry.

10. The method for analyzing the evolution of permeation grouting in soft rock structural planes according to claim 1, characterized in that The comparison of the test-simulation parameters between the permeation grouting displacement test and the simulation model to determine the grouting evolution characterization model for analyzing the evolution of grouting flow pattern and diffusion fluidization includes: Based on the slurry performance parameters and main grouting section parameters of the target slurry, fuse different grouting parameters to determine the slurry diffusion fluidization characterization corresponding to the permeation grouting displacement test and the simulation model respectively; Compare and verify the slurry diffusion fluidization characterization of the simulation model based on the slurry diffusion fluidization characterization of the permeation grouting displacement test to obtain the grouting evolution characterization model for analyzing the evolution of grouting flow pattern and diffusion fluidization.

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