Splitting grouting discrete element numerical simulation method based on slurry viscosity time-varying characteristic

Abstract

The invention provides a splitting grouting discrete element numerical simulation method based on slurry viscosity time-varying characteristics, and belongs to the technical field of splitting grouting simulation. Comprising the following steps: performing a slurry viscosity time-varying characteristic indoor test to obtain the time-varying characteristic of slurry viscosity; constructing a slurry DEM particle viscosity time-varying contact model based on the time-varying characteristics; carrying out splitting grouting simulation based on a slurry DEM particle viscosity time-varying contact model; under a fixed working condition, an obtained simulation result is compared with a test result of an indoor test, and the slurry DEM particle contact model is calibrated; and the calibrated slurry DEM particle contact model is utilized to carry out splitting grouting simulation under multiple working conditions. According to the device and the method, the viscosity time-varying characteristic and the phase change consolidation mechanism of the slurry can be effectively coupled, and the dynamic influence of the rheological characteristic of the slurry in a pore injected medium on the splitting diffusion process can be accurately simulated; and a beneficial method is provided for improving the accuracy and scientificity of the splitting grouting diffusion process of the tunnel and underground engineering.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of splitting grouting simulation, and particularly relates to a splitting grouting discrete element numerical simulation method based on time-varying characteristics of slurry viscosity. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] With the continuous expansion of tunnel construction scale, engineering is constantly advancing to complex strata such as deep, high ground stress and water-rich soft surrounding rock, and geological disasters such as mud gushing and water gushing occur frequently, which seriously threatens construction safety and engineering stability. For areas with more complex geological conditions, soft rock is more prone to instability and failure. To cope with this challenge, key technologies such as advanced geological prediction, intelligent monitoring and grouting reinforcement are being continuously strengthened. In particular, the widespread application of splitting grouting technology in water inrush disaster control can provide strong support for tunnel construction in complex strata and improve the safety and resilience of infrastructure construction.

[0004] Water-rich soft surrounding rock is composed of granular soil, with small and discrete internal pores, which meets the characteristics of pore being injected medium. Due to poor pore connectivity, groundwater is stored in pore space and is prone to sudden changes in water pressure under external disturbance. During tunnel excavation, the stress redistribution of surrounding rock under the influence of excavation disturbance can easily lead to an increase in pore water pressure, resulting in rock mass structure damage and further inducing mud gushing and water gushing disasters. Especially in areas with high ground stress or poor strata stability, the risk of mud gushing and water gushing increases significantly, and measures such as grouting reinforcement are needed to improve the stability of surrounding rock and ensure construction safety.

[0005] Splitting grouting diffusion mode is a key way in grouting reinforcement engineering, especially suitable for reinforcement of soft surrounding rock and fractured rock mass. Under high pressure, the slurry overcomes the confining stress of surrounding rock, expands along the microfracture and forms a splitting channel, and after the slurry solidifies, a splitting slurry vein skeleton is formed in the injected medium, which can improve the overall strength and impermeability of the rock mass. Compared with permeation grouting, splitting grouting is more suitable for low permeability strata and exhibits superior reinforcement effect in complex geological conditions, and is widely used in mud gushing and water gushing disaster control and tunnel stability control.

[0006] However, the splitting slurry diffusion process is a black box process in both laboratory tests and field tests and cannot be directly observed. The flow characteristics of the slurry are influenced by strata heterogeneity, stress state and slurry properties, making it difficult to accurately control and predict. Although transparent soil tests can simulate slurry expansion, there are significant differences in material mechanical properties between transparent soil tests and real strata, and the diffusion mode of slurry in complex geological conditions cannot be truly reproduced. In addition, transparent soil tests have strict requirements on the experimental environment and cannot accurately reflect the actual engineering situation, and their results have certain limitations, affecting the in-depth understanding of the splitting grouting diffusion and reinforcement mechanism.

[0007] The diffusion and reinforcement mechanism of split grouting is often studied by numerical simulation methods due to its invisibility and complex fluid-structure coupling characteristics, in order to reveal the grout expansion mechanism and optimize the grouting design. However, the common finite element method (FEM), finite volume method (FVM) and volume of fluid method (VOF) have limitations in split grouting simulation. For example, FEM is based on the continuous medium assumption, which is difficult to accurately describe the discrete fractures of rock mass and the intermittent expansion characteristics of grout, affecting the accurate simulation of the grout migration path; FVM is suitable for fluid conservation problems, but its ability to describe the non-uniform permeability of grout and the splitting process is limited and easily affected by mesh division; VOF is mainly used for free interface flow simulation, and it is difficult to effectively describe the mechanical effect of grout on the injected medium and the evolution process of the splitting channel. In contrast, the discrete element method (DEM) is based on the discrete particle assumption, which can naturally simulate the initiation, expansion of the splitting channel and the splitting-compaction process of grout on the injected medium, and can dynamically track the stress evolution of the grout-rock interaction, making it suitable for grouting simulation in highly heterogeneous strata and providing a more detailed mechanical model expression for split grouting in complex geological conditions.

[0008] Therefore, even though there are many methods for numerically simulating split grouting in the prior art, these methods all have the following technical problems: (1) The time-varying effect of grout viscosity is ignored. Ignoring the time-varying effect of grout viscosity will lead to deviations in the simulation of fluidity and diffusion range. The initial viscosity of grout is low and it diffuses quickly, then the viscosity increases and eventually solidifies. If the numerical simulation uses a constant viscosity assumption, the diffusion range may be overestimated or underestimated, affecting the prediction of the reinforced area. For example, if the viscosity is too low, the simulation result may exaggerate the grout permeation range; if the viscosity is too high, the initial diffusion capacity of the grout may be underestimated.

[0009] (2) The phase change process of grout cannot be accurately described. The inability to accurately describe the phase change process of grout will affect the simulation of the solidification mechanism. Grout gradually changes from a liquid state to a gel state and then solidifies. If the numerical simulation does not consider this evolution process and assumes that the grout maintains a fixed viscosity, it cannot truly reproduce the solidification process, leading to distorted evaluation of the mechanical strength, bearing capacity and other reinforcement effects.

[0010] (3) Ignoring the time-varying effect of grout viscosity will affect the interaction between grout and surrounding rock. As the viscosity increases, the grout's permeability decreases and the diffusion pattern changes, which in turn affects the degree of fracture filling and the reinforcement effect. If the simulation does not take this factor into account, it may overestimate the distribution range of grout in the fracture, thereby affecting the evaluation of engineering safety and stability. Therefore, in the numerical simulation of split grouting, it is crucial to reasonably couple the time-varying characteristics of grout viscosity. SUMMARY

[0011] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a splitting grouting discrete element numerical simulation method based on time-varying characteristics of slurry viscosity, which can effectively couple time-varying characteristics of slurry viscosity and phase change consolidation mechanism, realize effective simulation of the dynamic influence of the rheological properties of the slurry in the pore injected medium on the splitting diffusion process, and further provide effective guidance for improving the scientificity and applicability of tunnel and underground engineering grouting reinforcement design.

[0012] In order to achieve the above-mentioned purpose, one or more embodiments of the present application provide the following technical solutions: The present application provides a splitting grouting discrete element numerical simulation method based on time-varying characteristics of slurry viscosity.

[0013] The splitting grouting discrete element numerical simulation method based on time-varying characteristics of slurry viscosity comprises: Performing a slurry viscosity time-varying characteristic laboratory test, and obtaining time-varying characteristics of slurry viscosity according to the test results; Based on the obtained time-varying characteristics, a slurry DEM particle contact model is constructed; and splitting grouting simulation is performed based on the constructed slurry DEM particle contact model; Under fixed working conditions, the simulation results obtained by the splitting grouting simulation are compared with the test results of the laboratory test, and the slurry DEM particle contact model is calibrated according to the comparison results; The calibrated slurry DEM particle contact model is used to perform splitting grouting simulation under multiple working conditions.

[0014] Further, the laboratory test comprises a cement neat slurry funnel flowability determination test, a cement neat slurry flat plate flowability test, and a slurry viscosity time-varying characteristic paddle rotor test.

[0015] Further, in the cement neat slurry funnel flowability determination test, the viscosity growth characteristics are characterized by the change of the slurry flow-out time from the standard funnel; In the cement neat slurry flat plate flowability test, the expansion limiting effect of slurry viscosity growth is obtained by measuring the expansion diameter of the slurry on the flat plate; In the slurry viscosity time-varying characteristic paddle rotor test, the viscosity change curve of the slurry with time is depicted by measuring the shear viscosity of the slurry at different time points.

[0016] Further, the construction of the slurry DEM particle contact model comprises: injection medium environment simulation, servo ground stress loading, slurry particle generation, particle parameter assignment, multi-field physical information monitoring, slurry viscosity time-varying initial condition design, global particle contact parameter traversal, slurry viscosity time-varying characteristic determination and iterative update, slurry phase change critical condition, and slurry initial setting strength improvement update.

[0017] Further, based on the injected medium environment simulation, a numerical model of the pore medium conforming to the actual geological conditions is constructed; in the process of monitoring the multi-field physical information, the detected physical information includes the pressure change in the slurry, the slurry injection amount change and the pore change between the injected media during the slurry diffusion process.

[0018] Further, when the global particle contact parameters are traversed, the contact parameter assignment command based on the discrete element method is used to gradually adjust the inter-particle force by using the trial-and-error method to simulate the diffusion form of the slurry in the pore medium; the slurry viscosity time-varying characteristic determination and iterative update, that is, according to the slurry flow state and the shear stress condition, the slurry viscosity parameter is dynamically adjusted, so that the simulation result is consistent with the actual grouting process.

[0019] Further, the slurry phase change critical condition is set based on the slurry initial setting time and the rheological property.

[0020] Further, under the fixed working condition, the simulation results obtained by the splitting grouting simulation are compared with the test results of the indoor test; wherein the test results obtained by the indoor test include the form results, the physical performance results and the mechanical performance results.

[0021] Further, the obtained form results are: under the fixed working condition in the physical test, the splitting grouting test results are observed, the form of the slurry splitting diffusion is obtained, the development direction, the maximum diffusion range and the average width of the slurry vein of the slurry splitting diffusion are measured; The obtained physical performance results are: in terms of the overall physical performance of the grouting reinforcement body, the permeability and the compactness are tested; The obtained mechanical performance is: the strength and deformation characteristics of the reinforcement body are evaluated by using the triaxial compression test and the direct shear test.

[0022] Further, the multiple working conditions include the ground stress condition, the grouting pressure and the slurry ratio.

[0023] The above one or more technical solutions have the following beneficial effects: (1) The present application can dynamically simulate the time-varying characteristic of the slurry viscosity. The present application is based on the time-varying characteristic of the slurry viscosity obtained by the indoor test, and constructs a slurry DEM particle contact model; and based on the constructed slurry DEM particle contact model, the splitting grouting simulation is carried out. By introducing the simulation method of the slurry viscosity changing with time, the influence of the phase change process of the slurry from low viscosity to high viscosity, and from liquid state to gel state and then to consolidation on the splitting diffusion process can be more scientifically and accurately described. This has important significance for improving the flowability prediction of the slurry under complex geological conditions and the reinforcement effect evaluation, and breaks through the limitation that the traditional DEM numerical simulation method cannot fully consider the time-varying characteristic of the viscosity.

[0024] (2) The present application combines the discrete element method with experimental data to optimize the slurry DEM particle contact model: by developing a contact model with strong adaptability in the discrete element method, the diffusion process of slurry in porous media can be accurately simulated, that is, the time-varying characteristics of parameters such as the bonding force between slurry particles and the flow resistance. This optimization makes the simulation results closer to the actual situation, thereby providing more reliable numerical basis for grouting reinforcement design. Through numerical simulation evolution, the phase change process of slurry can be accurately described.

[0025] (3) The present application compares the simulation results obtained by simulating the splitting grouting under fixed working conditions with the test results of indoor tests, and calibrates the slurry DEM particle contact model according to the comparison results; using the calibrated slurry DEM particle contact model, the splitting grouting under multiple working conditions is simulated. The present application verifies the accuracy and reliability of the numerical simulation through multi-field physical information monitoring and verification, that is, comparing and checking the results based on physical tests and simulation results to ensure the accuracy and reliability of the numerical simulation. Through comparison with the splitting slurry flow, pressure evolution law with time measured in physical tests, and the final splitting diffusion shape and overall physical and mechanical properties of the reinforcement body, the rationality of the simulation results is verified, which provides a strong scientific basis for grouting reinforcement in actual engineering and helps to guide tunnel construction and safety reinforcement under complex geological conditions. At the same time, under the calibration of the model, the consideration of multiple working conditions and the comparison of multiple test results, the influence of the time-varying effect of slurry viscosity on the interaction between slurry and surrounding rock can be better reflected, thereby providing better guarantee for engineering safety and stability evaluation.

[0026] The advantages of the additional aspects of the present application will be partially given in the following description, partially will become apparent from the following description, or will be understood by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the application and explanations thereof serve to explain the application, and do not constitute an improper limitation of the application.

[0028] Figure 1 The flow chart of the splitting grouting discrete element numerical simulation method based on the time-varying characteristics of slurry viscosity in the embodiment one of the present application.

[0029] Figure 2 The schematic diagram of the time-varying parameters of the splitting slurry viscosity in the embodiment one of the present application.

[0030] In the figure, 1, the pore is injected with a medium; 2, the vertical ground stress servo loading boundary; 3, the horizontal ground stress servo loading boundary; 4, the grouting pipe boundary; 5, the splitting slurry injection channel; 6, the surface viscosity parameter between slurry particles; 7, the slurry outlet; 8, the development direction of the splitting slurry. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0032] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit the exemplary embodiments according to the present application.

[0033] In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0034] The overall idea of the present application is that the time-varying effect of slurry viscosity is an important property of grouting material, which directly affects the flowability of slurry, the diffusion range and the reinforcement mechanical properties of the medium being grouted. The slurry usually undergoes dynamic evolution from low viscosity to high viscosity and phase change consolidation during the grouting process. Therefore, in numerical simulation, this complex time-varying process must be reasonably described to accurately reflect the diffusion mechanism and reinforcement effect of the slurry in the surrounding rock. However, in the existing discrete element method (DEM) simulation of the slurry splitting and diffusion process, there are still great technical challenges. DEM is mainly suitable for the motion and contact mechanics calculation of particle discrete bodies, and the existing technology cannot accurately express the phase change process of the slurry from liquid to gel and then to consolidation. At the same time, DEM relies on the particle interaction model, but the existing model still has limitations in describing the time evolution of slurry viscosity, the change of rheological properties and the interaction between slurry and surrounding rock interface. Therefore, it is still a difficult problem to effectively couple the time-varying characteristics of slurry viscosity and the phase change and consolidation mechanism in the DEM framework in the numerical simulation of splitting grouting. Therefore, the splitting grouting discrete element numerical simulation method based on the time-varying characteristics of slurry viscosity proposed in the present application effectively describes the dynamic influence of the rheological properties of the slurry in the pore medium on the splitting and diffusion process, breaks through the limitation of the existing discrete element method that cannot describe the phase change process of the slurry, provides a more accurate numerical calculation means for the splitting grouting mechanism research under complex geological conditions, improves the scientificity and applicability of the grouting reinforcement design of tunnels and underground engineering, and has beneficial engineering application value and theoretical guiding significance.

[0035] Embodiment one This embodiment discloses a discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity. Based on discrete element (DEM) theory and combined with experimental results of the flowability and time-varying characteristics of different types of grout in laboratory tests, this method further develops a contact model for the time-varying characteristics of grout viscosity. This enables effective simulation of the dynamic influence of grout rheological properties on the splitting diffusion process in porous grouting media. This invention provides a reference approach for the effective expression of the time-varying characteristics of grout viscosity and the phase transformation consolidation mechanism in discrete element simulation methods for splitting grouting in porous media.

[0036] like Figure 1 As shown, the discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity includes: Step S1: Conduct indoor tests on the time-varying characteristics of slurry viscosity, and obtain the time-varying characteristics of slurry viscosity based on the test results; Step S2: Based on the obtained time-varying characteristics, construct a particle contact model of the slurry DEM; perform fracturing grouting simulation based on the constructed slurry DEM particle contact model; Step S3: Under fixed working conditions, compare the simulation results obtained from the split grouting simulation with the test results from the indoor test, and calibrate the grout DEM particle contact model based on the comparison results. Step S4: Using the calibrated grout DEM particle contact model, perform splitting grouting simulation under multiple working conditions.

[0037] Based on the above method, this invention can effectively couple the time-varying characteristics of grout viscosity and the phase change consolidation mechanism, achieving effective simulation of the dynamic influence of grout rheological properties on the splitting and diffusion process in the pore-filled medium; thus providing effective guidance for improving the scientificity and applicability of grouting reinforcement design for tunnels and underground engineering. To facilitate understanding of the technical solution of this invention, the specific implementation methods of this invention will be further explained and described below.

[0038] Step S1: Conduct indoor tests on the time-varying characteristics of slurry viscosity, and obtain the time-varying characteristics of slurry viscosity based on the test results.

[0039] The laboratory tests for the time-varying characteristics of slurry viscosity include: cement paste funnel flowability test, cement paste plate flowability test, and slurry viscosity time-varying characteristic paddle rotor test, used to summarize the time-varying characteristics of slurry viscosity. Specifically, this can be achieved through steps S101-S104: Step S101: Cement paste funnel flowability test.

[0040] The initial fluidity and thickening trend of cement paste over time can be quickly obtained by measuring the fluidity of the paste using a funnel. In the experiment, the change in the time it takes for the paste to flow out of the standard funnel reflects its viscosity growth characteristics, thus characterizing the rheological behavior of the paste in the initial stage of grouting.

[0041] As an optional embodiment, the cement paste funnel flow test can be used to evaluate the initial flowability of the paste and the rheological changes over time. Specifically, the test uses a standard flow funnel to measure the flow time of a certain volume of paste through the funnel opening; a shorter flow time indicates better initial flowability of the paste, while the flow time increases over time, reflecting the gradual thickening of the paste. This test can quantitatively characterize the thixotropy and early setting tendency of the paste, providing basic data for simulating the time-varying viscosity characteristics.

[0042] Step S102, cement paste flat plate flow test.

[0043] The cement paste flat plate flow test is used to measure the spreadability of the paste at different time points, and then to characterize the effect of viscosity increase on the flow range of the paste. In the test, the restriction of viscosity growth on the spreading ability of the paste can be obtained by measuring the spreading diameter of the paste on the flat plate.

[0044] As an optional embodiment, the cement paste flat plate flow test can be used to measure the spreading ability of the paste on a horizontal surface to evaluate its dilution degree and time dependence. Specifically, in the test, the paste is poured onto a standard glass plate or metal plate to form a circular spreading area under the action of its own gravity, and the flow performance of the paste is determined by measuring the change in spreading diameter. A larger initial flowability indicates a more dilute paste, while the spreading diameter gradually decreases over time, indicating that the paste has increased rheological properties and gradually increased viscosity. This test method is suitable for paste with low water-cement ratio and can intuitively reflect the trend of viscosity change over time.

[0045] Step S103, paddle rotor test of time-varying viscosity characteristics of paste.

[0046] The paddle rotor test of time-varying viscosity characteristics of paste is a direct measurement of the shear viscosity of the paste at different time points, which can accurately depict the viscosity change curve of the paste over time and provide key parameter support for numerical simulation.

[0047] The paddle rotor test of time-varying viscosity characteristics of paste is a precise method for directly measuring the viscosity of the paste. In actual implementation, by rotating the paddle rotor, the viscosity change of the paste under different shear rates can be measured, and then the shear thinning or shear thickening characteristics of the paste can be analyzed, and the time-varying viscosity change before setting of the paste can be quantified. This test can provide the viscosity evolution curve of the paste from the initial to the final setting, providing key input parameters for numerical simulation.

[0048] Step S104, summary of time-varying viscosity characteristics of paste.

[0049] Through the above three tests, the contact properties between the slurry particles in the discrete element simulation, such as the bonding force and flow resistance between the particles, can be accurately calibrated to ensure that the slurry diffusion process in the simulation is consistent with the actual situation. This calibration method enables the discrete element simulation structure to truly reflect the mechanical behavior in the slurry splitting and diffusion, thereby improving the reliability of the simulation results.

[0050] Based on the test results of steps S101-S104, the time-varying characteristics of the slurry viscosity can be summarized as follows: the slurry has a low viscosity and high flowability in the initial stage, and as time goes on, the hydration reaction occurs, the internal structure gradually forms and strengthens, resulting in an increase in viscosity and a decrease in flowability. The growth rate of the slurry viscosity is closely related to the water-cement ratio, admixtures, and types of additives. Through the test data, a time-varying mathematical model of the slurry viscosity can be established to provide accurate physical property parameter input for numerical simulation of the splitting grouting, and to guide the optimization of slurry proportioning and construction time control in engineering practice, thereby improving the grouting effect and engineering stability.

[0051] The viscosity of the cement-based slurry changes with time and is mainly affected by factors such as hydration reaction, temperature, and additives. The calculation formula of the exponential growth model of the time-varying characteristics of the cement-based slurry viscosity can be expressed as: ; wherein, represents the viscosity of the slurry at time t, with the unit of Pa·s; represents the initial viscosity of the slurry, with the unit of Pa·s; represents the viscosity growth rate, and t is the time.

[0052] Step S2, based on the obtained time-varying characteristics, a slurry DEM particle contact model is constructed; and based on the constructed slurry DEM particle contact model, splitting grouting simulation is performed.

[0053] The construction of the slurry DEM particle contact model includes: injection medium environment simulation, servo ground stress loading, slurry particle generation, particle parameter assignment, multi-field physical information monitoring, slurry viscosity time-varying initial condition design, global particle contact parameter traversal, slurry viscosity time-varying characteristic determination and iterative update, slurry phase change critical condition, and slurry strength improvement update after initial setting. The following steps S201-S210 can be used to achieve the above: Step S201, injection medium environment simulation.

[0054] In the injection medium environment simulation stage, a numerical model of the pore medium that conforms to the actual geological conditions is constructed, including parameters such as rock and soil particle distribution, porosity, and permeability.

[0055] ​According to the engineering background and the properties of the injected medium in physical tests, a numerical model of the porous medium is constructed in accordance with the actual geological conditions. Specifically, the particle discrete element method (DEM) is used to establish the injected medium particles, including defining the particle size, porosity, particle grading, contact model and contact parameters, etc. The necessary properties are generated by the command stream and Fish language code to generate the injected medium particles, so that the numerical model can accurately reflect the true formation characteristics and provide a reasonable injected medium environment for slurry diffusion.

[0056] Step S202, servo ground stress loading.

[0057] The servo ground stress loading is performed to ensure that the stress state of the medium in the numerical simulation process is consistent with the field conditions, and to provide a real stress boundary for slurry diffusion.

[0058] Further, the servo-controlled ground stress boundary condition is applied in the DEM model to make the stress state of the calculation domain consistent with the field. By setting the force and deformation constraints of the boundary particles, the initial stress balance of the surrounding rock before grouting is realized, and a real stress environment is provided for the slurry splitting diffusion.

[0059] Step S203, slurry particle generation.

[0060] In the slurry particle generation stage, the slurry particles are constructed by numerical generation method to have appropriate contact parameters in the initial state.

[0061] Further, DEM is known as the particle flow method in practical application, which can form and express the splitting slurry flow characteristics in the injected medium by a number of particle particles. In the initial state, the slurry particles should have fluid characteristics, which are characterized by the Hertz model. Or consider the JKR model of the attractive force caused by the van der Waals effect, the mutual attraction between particles is represented by surface energy, and the attraction between particles only exists on the contact surface, which can best represent the contact characteristics between wet particles, and is often used to represent the bonding effect between wet and fine particles to ensure that it can simulate the flow behavior of low viscosity slurry in the early stage.

[0062] Step S204, particle parameter assignment.

[0063] Based on the experimental data, the contact stiffness, viscous damping coefficient and other parameters between particles are determined to ensure the reasonableness of slurry diffusion in the simulation process.

[0064] Further, the contact parameters between the slurry particles and the rock-soil particles are set according to the test data, including contact stiffness, viscous damping, friction coefficient, etc. The viscoelastic contact model is used to calculate the interaction force between the injected medium particles, and the Hertz model or JKR model is used to calculate the interaction force between the slurry particles and the injected medium particles, to ensure that the slurry can accurately simulate the rheological properties during diffusion.

[0065] The contact parameter setting method is as follows: first, the name of the required parameter in the help file of the applicable inter-particle contact model such as the Hertz model or the JKR model is inquired, and the value range of each parameter is inquired; second, according to the physical test results of the cement paste funnel flowability test, the cement paste flat plate flowability test, the paddle rotor test of the time-varying characteristics of the slurry viscosity and the like, the numerical test results under a certain working condition are made consistent with the physical test results by means of trial and error, and at this time, it can be considered that the contact parameters adopted are scientific and reasonable.

[0066] Step S205, multi-field physical information monitoring.

[0067] The monitored physical information includes the pressure change in the slurry, the slurry injection volume change, the inter-injected medium pore change and the like in the slurry diffusion process, and is used to provide data support for subsequent analysis.

[0068] Further, in the DEM calculation process, the internal pressure of the slurry particle, the slurry injection volume and the like are monitored in real time, and the porosity change and the like in the injected medium are monitored by means of measurement of a circle. Combined with the stress distribution and the crack propagation, the splitting diffusion path and the filling degree of the slurry in the medium are analyzed, and a scientific basis is provided for the slurry diffusion and reinforcement mechanism research.

[0069] Step S206, slurry viscosity time-varying initial condition design.

[0070] In the slurry viscosity time-varying initial condition design stage, the slurry viscosity change curve with time is set according to the test data, and the value is assigned in the numerical calculation.

[0071] Further, according to different grouting processes (orifice mixing, hole bottom mixing and the like), the initial trigger condition of the slurry viscosity time-varying is set. The initial judgment and trigger condition of the rheological parameter evolution of the slurry particle with time is realized by writing a user-defined function (Fish language).

[0072] Step S207, global particle contact parameter traversal.

[0073] In the global particle contact parameter traversal, the particle interaction force is gradually adjusted by means of trial and error through the contact parameter assignment command of the discrete element method, so as to simulate the diffusion form of the slurry in the pore medium.

[0074] Further, the parameter sensitivity analysis method is adopted, the key parameters such as the contact stiffness, the shear strength and the viscous coefficient are adjusted in sequence in the DEM calculation, the diffusion state of the simulated slurry in different stages is ensured to be consistent with the actual state, and the model parameters are optimized to improve the simulation precision.

[0075] Step S208, slurry viscosity time-varying characteristic judgment and iterative update.

[0076] The time-varying viscosity characteristics of the slurry are determined and iteratively updated, and the viscosity parameters of the slurry are dynamically adjusted according to the flow state and shear stress conditions of the slurry, so that the simulation results are consistent with the actual grouting process.

[0077] Further, the viscosity variation trend of the slurry is determined according to the shear stress, flow rate and temperature conditions, and the inter-particle viscous damping coefficient is dynamically adjusted. In combination with the time-varying effect curve of the slurry viscosity, a time step control algorithm is used to make the slurry viscosity evolve with time, so as to ensure that the simulation results are consistent with the actual situation.

[0078] Step S209, setting the critical condition of slurry phase change.

[0079] The setting of the critical condition of slurry phase change is mainly based on the initial setting time and rheological characteristics of the slurry, so as to ensure that the slurry gradually completes the transition from fluid to solid during the diffusion process.

[0080] Further, according to the gel time and phase change characteristics of the slurry, the threshold value of the sudden change of the inter-particle interaction force with time is set. When the viscosity reaches the phase change point, the inter-particle contact stiffness and shear strength are gradually adjusted to make the slurry transition from fluid to solid and form the slurry vein structure.

[0081] Step S210, strength improvement update after initial setting of slurry vein.

[0082] In the strength improvement update stage after the initial setting of the slurry vein, the particle contact parameters are adjusted by considering the mechanical properties of the solidified slurry to reflect the improvement of the bearing capacity of the solidified slurry vein, so as to ensure that the model can accurately describe the whole process of slurry diffusion and solidification.

[0083] Further, after solidification, the particle contact model is adjusted by parameter setting or code command to improve the contact stiffness, friction coefficient and tensile strength to simulate the bearing capacity after consolidation. In combination with experimental data, the mechanical parameters of the slurry vein are corrected to ensure that the numerical model can accurately reflect the reinforcement effect of the split grouting.

[0084] The steps S201 to S210 are related to each other and jointly build a split grouting process simulation system that truly restores the time-varying viscosity characteristics of the slurry.

[0085] Step S3, under the fixed working condition, the simulation results obtained by the split grouting simulation are compared with the test results of the indoor test, and the slurry DEM particle contact model is calibrated according to the comparison results.

[0086] In the fixed working condition, the test and the simulation splitting diffusion final form and the grouting reinforcement physical and mechanical properties results are compared and checked; wherein, the test results obtained by the indoor test include the form results, the physical performance results and the mechanical performance results, namely: the simulation results are compared with the final form results of the splitting grout diffusion direction and range, the channel tension and the like in the physical test, and compared with the anti-permeability and the like physical performance of the grouting reinforcement, and compared with the triaxial compression or direct shear and the like mechanical performance test results. The specific implementation can be realized by the following steps S301-S303: Step S301, comparison and checking of the splitting grout diffusion form.

[0087] Under the condition of a certain fixed working condition in the physical test, the indoor or field high-pressure splitting grouting test results are observed, the grout splitting diffusion form is obtained, the grout splitting diffusion development direction, the maximum diffusion range and the average width of the grout vein are measured. By comparing the simulation results, it is judged whether the directionality, consistency and spatial distribution of the grout splitting diffusion in the simulation are consistent with the physical test, and then the rationality of the numerical simulation is checked.

[0088] As an optional embodiment, in the physical test, the grout diffusion direction, range and channel tension are obtained by the high-pressure splitting grouting test, and the profile cutting or CT scanning technology is used to measure the grout vein form. In the numerical simulation, the grout diffusion path, the maximum diffusion radius and the grout vein form parameters are extracted, the simulation results are compared with the test data, and it is judged whether the splitting directionality, consistency and spatial distribution are consistent. If there is a deviation, adjust the grout viscosity time-varying model or the particle contact parameters, optimize the numerical model, and improve the reliability of the simulation.

[0089] Step S302, comparison and checking of the anti-permeability and the like physical performance of the grouting reinforcement.

[0090] In terms of the overall physical performance of the grouting reinforcement, the test mainly includes the indicators such as permeability and density, the permeability test is used to measure the impermeability coefficient of the grouting reinforcement, and the simulation results are compared, and it is judged whether the simulation results are similar to the physical test results in terms of the physical performance of the reinforcement.

[0091] As an optional embodiment, the permeability test is used in the physical test to measure the permeability coefficient of the reinforcement, and the density, microstructure and the like characteristics are evaluated. In the numerical simulation, the permeability coefficient is calculated by using the seepage analysis, and the pore distribution after the grout vein consolidation is simulated. By comparing the permeability coefficients and the flow field distribution obtained by the test and the simulation, it is judged whether the simulation results are accurate in terms of the impermeability performance, and if necessary, the parameters in the solidification stage are optimized to match the physical performance of the actual reinforcement.

[0092] Step S303, comparison and checking of the triaxial compression or direct shear and the like mechanical performance.

[0093] In terms of mechanical properties, the strength and deformation characteristics of the reinforced body are evaluated through triaxial compression tests or direct shear tests, and the key parameters such as peak strength, deformation modulus, and shear strength obtained from the tests are compared with the simulation values to analyze the accuracy of the numerical model in stress-strain response.

[0094] As an optional embodiment, physical tests are used to determine the strength, deformation modulus, and shear strength of the reinforced body through triaxial compression tests or direct shear tests. Numerical simulation obtains stress-strain curves, peak strength, and shear failure modes through mechanical calculations. By comparing test data and simulation results, the accuracy of the simulation in the mechanical properties of the reinforced body is analyzed. If there are differences, adjust the slurry solidification model or particle contact stiffness parameters to optimize the mechanical response of the numerical simulation.

[0095] Through the verification of multiple types of tests in steps S301-S303, it can be ensured that the simulation method can more realistically reflect the actual diffusion behavior and reinforcement effect of the split grouting, and the reliability of the simulation results is improved.

[0096] Step S4, using the calibrated slurry DEM particle contact model, perform split grouting simulation under multiple working conditions.

[0097] Extended working condition split diffusion numerical simulation. Based on the verified numerical model in step S3, perform split diffusion simulation of slurry under more extended working conditions; among them, the extended multiple working conditions include geostress conditions, grouting pressure and slurry ratio, etc.

[0098] After completing the comparison and verification of physical tests and simulation results under certain working conditions, it is considered that the established slurry discrete element contact model can more accurately reflect the split diffusion process of the slurry. Based on this model, further simulation research under extended working conditions can be carried out under different geostress field distributions, surrounding rock properties, time-varying characteristics of slurry viscosity and grouting pressure, etc. The influence of different environmental variables on the diffusion range of slurry, the shape of slurry vein and the reinforcement effect can be analyzed. In the extended working condition simulation, by adjusting the parameters of the numerical model, the flow trend, split path and termination diffusion range of the slurry under different grouting pressures are predicted, and then the split grouting design under different stratum conditions is optimized, and the construction adaptability and engineering safety under complex environment are improved. This can be achieved through the following steps S401-S402: S401, extended working condition simulation based on the calibrated model.

[0099] After verifying and checking the contact parameters in step S3, the established numerical model for grout fracturing and diffusion can be used for simulation studies under different working conditions. By adjusting key parameters such as the in-situ stress field, grouting pressure, and grout mix ratio, their influence on the grout diffusion range, fracturing path, and reinforcement effect can be analyzed. For example, under different surrounding rock strength or permeability conditions, the study investigates how the grout penetrates, expands, and solidifies, revealing the sensitive factors of grout diffusion. This process helps to understand the fracturing grouting mechanism under complex geological conditions and provides a scientific basis for further design optimization.

[0100] S402, Engineering Applications and Optimization Design.

[0101] Extended working condition simulation not only helps reveal the diffusion law of grout but also provides guidance for practical engineering. By simulating the diffusion characteristics under different grouting parameters, grouting pressure, grout parameters, and mix proportions can be optimized to improve reinforcement effects and reduce grout loss. Furthermore, in projects such as tunnel surrounding rock reinforcement, slope treatment, and mine backfilling, numerical simulation can be used to predict the grouting range, optimize construction techniques, improve construction efficiency and safety, thereby reducing engineering risks and achieving refined grouting design.

[0102] like Figure 2 As shown in the figure, the time-varying parameters of the splitting grout viscosity are obtained by the discrete element numerical simulation method based on the time-varying characteristics of grout viscosity. It can be seen that: 1) The existence environment of the pore-injected medium 1 under in-situ stress conditions was simulated and recreated under the constraints of biaxial geostress (i.e., vertical geostress servo loading boundary 2 and horizontal geostress servo loading boundary 3). Among them, the surface viscosity parameter 6 between the grout particles moves downward in the splitting grout injection channel 5 within the grouting pipe boundary 4, and after leaving the grout outlet 7, it develops in the splitting grout development direction 8 (the direction of the major principal stress).

[0103] 2) The time-varying viscosity characteristics between slurry particles are illustrated using the surf_adh parameter in the JKR contact model as an example. Figure 2 In the middle, the right side is a schematic diagram of the surface energy contact parameter values. The darker the color (closer to black), the closer the surface energy contact parameter is to 16, and the lighter the color (closer to white), the closer the surface energy contact parameter is to 0.

[0104] This shows that the slurry viscosity is relatively low (tending towards its initial viscosity) near the point where the slurry particles leave the grouting pipe, and gradually increases as the diffusion time increases (as the particles move further away from the grouting pipe). This demonstrates that the time-varying effect of slurry viscosity has been effectively simulated.

[0105] Those skilled in the art should understand that the modules or steps of the present application described above can be realized by general computer devices, or alternatively, they can be realized by program codes executable by the computer devices, so that they can be stored in the storage devices and executed by the computer devices, or they can be respectively manufactured into individual integrated circuit modules, or a plurality of modules or steps among them can be manufactured into a single integrated circuit module. The present application is not limited to any specific combination of hardware and software.

[0106] The specific embodiments of the present application described above in conjunction with the accompanying drawings are not intended to limit the protection scope of the present application. Those skilled in the art should understand that various modifications or changes made on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. A discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity, characterized in that, include: Indoor tests were conducted on the time-varying characteristics of slurry viscosity, and the time-varying characteristics of slurry viscosity were obtained based on the test results. Based on the obtained time-varying characteristics, a particle contact model of slurry DEM is constructed; and fracturing grouting simulation is performed based on the constructed slurry DEM particle contact model. Under fixed working conditions, the simulation results obtained from the split grouting simulation were compared with the test results from the laboratory test, and the grout DEM particle contact model was calibrated based on the comparison results. Using the calibrated grout DEM particle contact model, we conducted multi-condition fracturing grouting simulation.

2. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 1, characterized in that, The indoor tests include: cement paste funnel flowability test, cement paste plate flowability test, and slurry viscosity time-varying characteristic paddle rotor test.

3. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 2, characterized in that: In the test of cement paste flowability in a funnel, the change in the time it takes for the paste to flow out of a standard funnel characterizes the viscosity growth. In the cement paste plate fluidity test, the limiting effect of slurry viscosity growth on the spread is obtained by measuring the spread diameter of the slurry on the plate. In the time-varying viscosity test of the paddle rotor, the viscosity change curve of the slurry over time is plotted by measuring the shear viscosity of the slurry at different time points.

4. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 1, characterized in that, The construction of the slurry DEM particle contact model includes: simulation of the injected medium environment, servo-driven stress loading, slurry particle generation, particle parameter assignment, multi-field physical information monitoring, design of time-varying initial conditions for slurry viscosity, traversal of global particle contact parameters, determination and iterative update of time-varying characteristics of slurry viscosity, critical conditions for slurry phase change and update of strength enhancement after initial setting of slurry veins.

5. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 4, characterized in that, Based on the simulation of the injected medium environment, a numerical model of porous media that conforms to the actual geological conditions is constructed. During the multi-field physical information monitoring process, the detected physical information includes the changes in grout pressure, grout volume, and porosity between injected media during the grout diffusion process.

6. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 4, characterized in that: When traversing the global particle contact parameters, the interparticle forces are gradually adjusted using the trial-and-error method based on the contact parameter assignment command of the discrete element method to simulate the diffusion pattern of slurry in porous media. The determination and iterative update of the time-varying characteristics of grout viscosity involves dynamically adjusting the grout viscosity parameters based on the grout flow state and shear stress conditions to ensure that the simulation results match the actual grouting process.

7. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 4, characterized in that, The critical condition for phase change of slurry is set based on the initial setting time and rheological properties of the slurry.

8. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 1, characterized in that, Under fixed working conditions, the simulation results obtained from the splitting grouting simulation are compared with the test results from the laboratory test; the test results obtained from the laboratory test include morphological results, physical property results and mechanical property results.

9. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 8, characterized in that: The morphological results obtained are as follows: Under the fixed working conditions in the physical test, the results of the high-pressure splitting grouting test are observed to obtain the morphology of grout splitting and diffusion, and the development direction, maximum diffusion range and average width of grout veins of grout splitting and diffusion are measured. The obtained physical properties results are as follows: the overall physical properties of the grouting solidified body were tested, including permeability and density; The obtained mechanical properties are as follows: the strength and deformation characteristics of the reinforced body are evaluated by triaxial compression test and direct shear test.

10. The discrete element numerical simulation method for splitting grouting based on the time-varying characteristics of grout viscosity as described in claim 1, characterized in that, The multiple working conditions include ground stress conditions, grouting pressure, and grout mix ratio.

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