Simulation Method for Synchronous Grouting Injection at the Shield Tail during Shield Tunneling Based on CFD-DEM

Abstract

The present invention discloses a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM, which is applicable to the technical field of tunnel and underground engineering. The method includes performing CFD grid division on the geometric model of shield tail synchronous grout injection, defining various fluids including slurry-air and slurry-air-groundwater by the VOF method, controlling grout injection by pressure, and constructing a fluid CFD model; calibrating particle parameters by comparing a triaxial compression test and its DEM numerical simulation; calibrating the motion characteristics of particles by comparing an angle of repose test and its DEM numerical simulation, generating particles within the required research range of soil based on the calibration results, and constructing a soil DEM model; setting the time steps of the CFD model and the DEM model, and the coupling frequency between the two, respectively, performing coupled calculations until the set end time is reached, and obtaining the simulation results of shield tail synchronous grout injection. The present invention can provide guidance for the construction parameters of synchronous grout injection in shield construction.

Description

Technical Field

[0001] The present invention relates to the field of tunnel and underground engineering technologies, and particularly to a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM.

Background Art

[0002] The shield method is one of the common tunnel excavation methods, which has the advantages of being safe, efficient, fully automated, and having no impact on devices such as buildings on the ground and pipes underground. During the construction process, the shield machine uses an excavation blade to excavate the soil, the machine body supports the excavated soil as a temporary support, precast lining segments are assembled inside the machine body, and the tunnel structure is formed after the shield tail exits.

[0003] However, due to the size difference between the shield machine body and the lining, a certain shield tail gap is generated between the lining and the soil after the shield tail exits. During construction, a shield tail synchronous grout injection method for filling the gap is often used to reduce the disturbance of the formation caused by the existence of the gap. However, since the shield tail grout injection has a concealed nature, it is generally difficult to detect the grout injection process and effect.

[0004] Therefore, how to provide a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM, which can simulate the grout injection filling and diffusion process and provide guidance for the construction parameters of synchronous grout injection in shield construction, is a problem that those skilled in the art need to solve urgently.

Summary of the Invention

Means for Solving the Problems

[0005] In view of this, the present invention proposes a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM.

[0006] To achieve the above object, the present invention uses the following technical solutions.

[0007] A simulation method for shield tail synchronous grouting injection in shield construction based on CFD-DEM includes performing CFD grid division on the geometric model of shield tail synchronous grouting injection, defining various fluids including slurry-air and slurry-air-groundwater by the VOF method, controlling grouting injection by pressure, and constructing a fluid CFD model of shield tail synchronous grouting injection; calibrating the particle parameters required for the soil DEM model by comparing the results of triaxial compression tests of the original soil and DEM numerical simulations of triaxial compression tests; calibrating the motion characteristics of particles by comparing the results of the natural angle of repose tests of the original soil and DEM numerical simulations of natural angle of repose tests; generating particles within the required research range of the soil based on the calibration results of the particle parameters and the motion characteristics, and constructing a soil DEM model of shield tail synchronous grouting injection; setting the time step of the fluid CFD model, the time step of the soil DEM model, and the coupling frequency between the fluid CFD model and the soil DEM model, performing coupling calculations until the set end time is reached, and obtaining the simulation results of shield tail synchronous grouting injection.

[0008] Optionally, performing CFD grid division on the geometric model of shield tail synchronous grouting injection specifically includes performing density increasing processing on the grids in the area near the lining within a preset distance threshold, and adopting a sparse grid for areas other than the density increasing processing.

[0009] Optionally, defining various fluids including slurry-air and slurry-air-groundwater by the VOF method and controlling grouting injection by pressure specifically includes Set an initial area including the initial slurry area and the soil area or the initial slurry area, and the groundwater area and the soil area, Set the pressure difference between the slurry inlet and the air outlet under the initial boundary conditions so as to satisfy the control of grout injection by pressure.

[0010] Optionally, the pressure for controlling grout injection is as follows.

[0011]

Number

[0012] Here, JPEG2025521055000003.jpg6146

[0013] Optionally, by comparing the results of the triaxial compression test of the original soil and the DEM numerical simulation of the triaxial compression test, calibrating the particle parameters required for the soil DEM model specifically includes: Measure the particle grade of the original soil, conduct a triaxial compression test, and obtain the original soil stress-strain relationship curve, Mohr stress circle, and strength envelope. Conduct a DEM numerical simulation of the triaxial compression test by the discrete element method. Compare the results of the triaxial compression test and the DEM numerical simulation of the triaxial compression test, and calibrate the particle parameters required for the soil DEM model.

[0014] Optionally, by comparing the results of the angle of repose test of the original soil and the DEM numerical simulation of the angle of repose test, calibrating the motion characteristics of the particles specifically includes: Conduct an angle of repose test on the original soil. Conduct a DEM numerical simulation of the angle of repose test by the discrete element method. Compare the results of the angle of repose test and the DEM numerical simulation of the angle of repose test, and calibrate the motion characteristics of the particles.

[0015] Optionally, based on the above particle calibration results, generating particles within the required research range of the soil. Performing a density increase process on the particles in the area near the tunnel within a preset distance threshold; Further including the step of selecting particles having a diameter 2 to 3 times the average diameter of the particles in the area near the tunnel in an area where the slurry does not spread.

[0016] Optionally, the coupling calculation specifically is The fluid CFD model calculates independently based on the time step of the fluid CFD model, The soil DEM model calculates independently based on the time step of the soil DEM model, The fluid CFD model and the soil DEM model perform a coupling calculation based on the coupling frequency between the fluid CFD model and the soil DEM model. After updating the particle-fluid interaction force and the particle position, the independent calculation of the fluid CFD model and the independent calculation of the soil DEM model are respectively performed.

[0017] Optionally, the motion solution method of the fluid phase in the fluid CFD model is as follows.

[0018]

Number

[0019] Here, JPEG2025521055000005.jpg21156

[0020] Optionally, the motion control equation of the particles in the soil DEM model is as follows.

[0021]

Number

[0022]

Number

[0023] Here, JPEG2025521055000008.jpg43157

[0024] As can be seen from the above technical solutions, compared with the prior art, the present invention proposes a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM, and has the following beneficial effects.

[0025] The simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM proposed by the present invention simplifies the shield tail grout injection process in shield construction and reduces the calculation cost.

[0026] The simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM proposed by the present invention reveals the hidden process of slurry diffusion in the shield tail gap and soil.

[0027] The simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM proposed by the present invention can study the influence of grout injection construction parameters on the grout injection effect by adjusting parameters such as grout injection pressure, grout injection speed, slurry viscosity and density, and provide guidance for the process.

Effects of the Invention

[0028] The simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM proposed by the present invention can simulate different soil layer characteristics by adjusting particle grade, contact model, physical properties, etc., and can be applied to different engineering geological conditions.

Brief Description of the Drawings

[0029] To more clearly explain the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the following embodiments or prior art descriptions will be briefly introduced. Obviously, the drawings in the following descriptions are only the embodiments of the present invention. Based on the provided drawings and without the need for creative labor by those skilled in the art, other drawings can be obtained.

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0031] Hereinafter, with reference to the drawings of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, other embodiments that can be obtained without the need for creative labor by those skilled in the art all belong to the protection scope of the present invention.

Example

[0032] Example 1 of the present invention discloses a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM. As shown in FIG. 1, it includes the following.

[0033] Create a geometric model of shield tail synchronous grout injection using three-dimensional modeling software and set the size parameters of the geometric model to define the soil range to be investigated, the buried depth of the tunnel, and the sizes of the overburden and grout injection pipes. Name each boundary of the geometric model to facilitate the creation of subsequent CFD and DEM models.

[0034] Perform grid division on the geometric model of shield tail synchronous grout injection using CFD grid division software. Considering using a semi-resolved CFD-DEM model as the overall model, perform density increasing processing on the grids in the area near the overburden within a preset distance threshold, focus on the penetration and diffusion behavior of the slurry in the shield tail gap and soil, and adopt a sparse grid for areas other than the density increasing processing.

[0035] Set the basic parameters of the CFD model, including initial boundary conditions, initial fields, basic fluid properties, solution control parameters, etc. Define various fluids including slurry-air and slurry-air-groundwater using the VOF method. Setting the initial slurry region and soil region (without slurry) or the initial region including the initial slurry region, groundwater region, and soil region by using the setfields function includes setting the slurry inlet inlet and air outlet ground, and setting the pressure difference between the inlet and outlet under the initial boundary conditions to satisfy the control of grout injection by pressure and construct a fluid CFD model for shield tail synchronous grout injection.

[0036] The pressure for controlling grout injection is as follows.

[0037] [Number]

[0038] Here, JPEG2025521055000010.jpg10157

[0039] The motion solution method of the fluid phase in the fluid CFD model based on the Navier-Stokes equation is as follows.

[0040] [Number]

[0041] Here, JPEG2025521055000012.jpg20157

[0042] Perform in-situ sampling on the soil of the soil layer to be simulated to obtain sufficient undisturbed soil and prepare for the creation of the soil DEM model. Measure the particle gradation of the undisturbed soil and conduct triaxial compression tests to obtain the undisturbed soil stress-strain relationship curve, Mohr stress circle, and strength envelope. Conduct DEM numerical simulation for the triaxial compression test using the discrete element method. Calibrate the particle parameters required for the soil DEM model by comparing the results of the undisturbed soil triaxial compression test and the DEM numerical simulation of the triaxial compression test.

[0043] Further conduct the angle of repose test and perform DEM numerical simulation of the angle of repose test using the discrete element method. Calibrate the motion characteristics of the particles by comparing the results of the angle of repose test and the DEM numerical simulation of the angle of repose test.

[0044] Based on the particle correction results, set parameters related to the physical properties of the particles, generate a certain number of particles by the discrete element method, form a soil layer through natural settlement and compression, remove the excess particles above the ground surface, and construct a soil DEM model for shield tail synchronous grouting injection. Perform a density increase process on the particles in the area near the tunnel within a preset distance threshold, restore the porosity of the soil layer as much as possible based on the particle grade of the original soil, and focus on studying the slurry diffusion micro-mechanism in the soil. In other areas where the slurry does not spread, larger particles can be selected, and the diameter may be 2 to 3 times the average diameter of the particles in the density increase area. In those areas, focus on studying the soil disturbance and ground surface settlement caused by the grouting injection process.

[0045] The motion control equation of the particles in the soil DEM model is as follows.

[0046]

Number

[0047]

Number

[0048] Here, JPEG2025521055000015.jpg41155

[0049] Set the calculation parameters of the fluid CFD model and the soil DEM model, including the time step of the fluid CFD model, the time step of the soil DEM model, and the coupling frequency between the fluid CFD model and the soil DEM model. The fluid CFD model calculates independently based on the time step of the fluid CFD model, the soil DEM model calculates independently based on the time step of the soil DEM model, and the fluid CFD model and the soil DEM model perform a coupled calculation based on the coupling frequency between the fluid CFD model and the soil DEM model. After updating the particle-fluid interaction force and the particle position, perform the independent calculations of the fluid CFD model and the soil DEM model respectively, and continue until the set end time is reached and the simulation results of the shield tail synchronous grout injection are obtained. The time step and the coupling gap have a great impact on the simulation results. The overall process of the grout injection diffusion can be clearly observed from the simulation results, and other data such as the final diffusion radius can be extracted.

Example

[0050] Example 2 of the present invention discloses a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM, including the following content.

[0051] Taking the shield tail synchronous grouting injection during shield construction in gravel stratum as the research goal, a simulation is carried out. Referring to the geometric dimensions of the 4-hole synchronous grouting injection model box test of the shield tail in shield construction in gravel stratum, a geometric model of shield tail synchronous grouting injection is created using three-dimensional modeling software. In the referenced model box, based on the similarity ratio theory of the scaled model test, when the geometric similarity ratio C1 = 15, the model shield machine with a diameter of 400 mm in the test is used to simulate the actual shield machine with a diameter of 6000 mm. Here, modeling and research are carried out for half of the tunnel. The lining diameter is 370 mm, the buried depth of the tunnel is 2D (D = 400 mm). Considering the calculation cost, soil with a thickness of 50 mm in the axial direction of the tunnel is selected for research. Names (inlet, wall, outlet / ground, etc.) are assigned to each part and a geometric model is derived, as shown in Figure 2.

[0052] Grid division is performed on the geometric model of shield tail synchronous grouting injection using CFD grid division software. Since the area around the tunnel is the main diffusion range of the slurry, fine grids are adopted within the range of 0.5D (D is the tunnel diameter) around the tunnel, focusing on the movement form and free surface of the slurry, and coarse grids are adopted in other areas to reduce the calculation cost.

[0053] Two types of fluids, slurry - air, are defined using the VOF method, and the initial slurry region and soil region (without slurry) are set using the setFields function. Based on the measurement results of the model box test, the kinematic viscosity of the slurry is set to 6×10 -5 m / s 2 and the density is set to 1850 kg / m 3 respectively. Under the initial boundary conditions, the pressure difference between the slurry inlet inlet and the air outlet ground is set to meet the control of grouting injection by pressure, and a fluid CFD model of shield tail synchronous grouting injection is constructed.

[0054] The pressure for controlling grout injection is as follows.

[0055]

Number

[0056] Here, JPEG2025521055000017.jpg11157

[0057] Here, Let it be JPEG2025521055000018.jpg1020, and set the inlet slurry pressure to 21.12 kPa as follows.

[0058]

Number

[0059] The motion solution method of the fluid phase in the fluid CFD model based on the Navier-Stokes equation is as follows.

[0060]

Number

[0061] Here, JPEG2025521055000021.jpg20158

[0062] Sample the soil used in the model box test to obtain sufficient original soil and prepare for the creation of the soil particle DEM model. Measure the particle grade of the original soil and conduct a large-scale triaxial compression test to obtain the stress-strain relationship curve, Mohr stress circle, and strength envelope of the soil sample. Create a DEM numerical simulation of the triaxial compression test using the discrete element technique. As shown in Figure 3, compare the results by numerical methods and test methods, and calibrate the particle parameters.

[0063] Further perform model tests and soil angle of repose tests on the calibrated particles, and conduct DEM numerical simulations of the angle of repose test. Figure 4 is the first state diagram of the DEM numerical simulation of the angle of repose test, and Figure 5 is the second state diagram of the DEM numerical simulation of the angle of repose test. By comparing the results, further calibrate the movement characteristics of the particles.

[0064] Based on the particle calibration results, set the parameters related to the physical properties of the particles, generate a certain number of particles within the required research range of the soil selected in Example 2 of the present invention by the discrete element method, form a soil layer by natural settlement and compression, and remove the excess particles above the ground surface. Set a 300mm×600mm area near the tunnel as the area with increased particle density. Restore the porosity and compactness of the soil layer with spherical particles with a diameter in the range of 3 - 10mm within the area with increased density, and focus on studying the slurry diffusion mechanism and path in the soil. In other areas where the slurry does not spread, all particles use spherical particles with a diameter of 10mm. In those areas, focus on studying the soil disturbance and ground surface settlement caused by the grouting injection process, and construct a soil DEM model for shield tail synchronous grouting injection.

[0065] The motion control equation of the particles in the soil DEM model is as follows.

[0066]

Number

[0067]

Number

[0068] Here, JPEG2025521055000024.jpg41159

[0069] Set the time steps of CFD and DEM and the coupling frequency of both respectively. CFDdt = 0.0005 s, DEMdt = 0.000005 s, couplingInterval = 100. Start the coupled calculation. During the process, CFD and DEM calculate respectively, and perform coupled calculations at a certain time interval. After updating information such as the particle-fluid interaction force and particle position, perform independent calculations again respectively, and repeat the above process until the set end time is reached. From the simulation results, the entire process of grout injection diffusion can be clearly observed, and other data such as the final diffusion radius can be extracted. Figure 6 is the simulated grout injection effect diagram 1, Figure 7 is the simulated grout injection effect diagram 2, Figure 8 is the simulated grout injection effect diagram 3, and Figure 9 is the simulated grout injection effect diagram 4.

[0070] An embodiment of the present invention discloses a simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM. By constructing a fluid CFD model of shield tail synchronous grout injection and a soil DEM model of shield tail synchronous grout injection, and performing combined calculations, the simulation of the entire process of grout injection diffusion is realized, which not only reduces the calculation cost, but also studies the influence of grout injection construction parameters on the grout injection effect by adjusting the settings of parameters such as grout injection pressure, grout injection speed, slurry viscosity and density, and can provide guidance for the process. In addition, different soil layer characteristics can be simulated by adjusting particle grade, contact model, physical properties, etc., and it can be applied to different engineering geological conditions.

[0071] Each embodiment in this specification is described in an accumulative manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between each embodiment may be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, they are briefly described, and the relevant parts may refer to the description of the method part.

[0072] Based on the above description of the disclosed embodiments, those skilled in the art can implement or use the present invention. Various modifications to those embodiments will be apparent to those skilled in the art, and the general principles defined in the text can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to those embodiments disclosed in the text, but rather conforms to the broadest scope consistent with the principles and novel features disclosed in the text.

Claims

1. A simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM, comprising: Performing CFD grid division on the geometric model of shield tail synchronous grout injection, defining various fluids including slurry-air and slurry-air-groundwater by the VOF method, and controlling grout injection by pressure, thereby constructing a fluid CFD model of the shield tail synchronous grout injection; Calibrating the particle parameters required for the soil DEM model by comparing the results of triaxial compression tests of the original soil and DEM numerical simulations of the triaxial compression tests; Calibrating the motion characteristics of particles by comparing the results of the angle of repose tests of the original soil and DEM numerical simulations of the angle of repose tests; Generating particles within the required research range of the soil based on the calibration results of the particle parameters and the motion characteristics, and constructing a soil DEM model of the shield tail synchronous grout injection; Setting the time step of the fluid CFD model, the time step of the soil DEM model, and the coupling frequency between the fluid CFD model and the soil DEM model, and performing coupled calculations until the set end time is reached to obtain the simulation results of the shield tail synchronous grout injection. A simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM, characterized by comprising the above steps.

2. Performing CFD grid division on the geometric model of shield tail synchronous grout injection specifically means: Increasing the density of the grids in the area near the lining within a preset distance threshold; Adopting a sparse grid for areas other than the density increasing process. A simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM according to Claim 1.

3. Defining various fluids including slurry-air and slurry-air-groundwater by the VOF method and controlling grout injection by pressure specifically means: Setting initial regions including the initial slurry region and the soil region, the initial slurry region, and the groundwater region and the soil region; A method for simulating shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 1, characterized in that a pressure difference between a slurry inlet and an air outlet under initial boundary conditions is set so as to satisfy the control of grout injection by pressure.

4. The pressure for controlling grout injection is as follows: A method for simulating shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 3, characterized in that it is as follows.

5. Calibrating the particle parameters required for the soil DEM model by comparing the results of the triaxial compression test of the original soil and the DEM numerical simulation of the triaxial compression test specifically includes: Measuring the particle grade of the original soil, performing the triaxial compression test, and obtaining the original soil stress-strain relationship curve, Mohr stress circle, and strength envelope line. Performing a DEM numerical simulation of the triaxial compression test by the discrete element method. A method for simulating shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 1, characterized in that the results of the triaxial compression test and the DEM numerical simulation of the triaxial compression test are compared to calibrate the particle parameters required for the soil DEM model.

6. Calibrating the movement characteristics of particles by comparing the results of the angle of repose test of the original soil and the DEM numerical simulation of the angle of repose test specifically includes: Performing an angle of repose test on the original soil. Performing a DEM numerical simulation of the angle of repose test by the discrete element method. A method for simulating shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 1, characterized in that the results of the angle of repose test and the DEM numerical simulation of the angle of repose test are compared to calibrate the movement characteristics of particles.

7. After generating particles within the required research range of the soil based on the particle calibration results, Performing a density increasing process on the particles in the area near the tunnel within a preset distance threshold; Selecting particles having a diameter 2 to 3 times the average diameter of the particles in the area near the tunnel in the area where the slurry does not spread. A method for simulating shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 1, further comprising the above steps.

8. The combined calculation specifically includes: The fluid CFD model is calculated independently based on the time step of the fluid CFD model. The soil DEM model is calculated independently based on the time step of the soil DEM model. The fluid CFD model and the soil DEM model perform a coupled calculation based on the coupling frequency between the fluid CFD model and the soil DEM model. After updating the particle-fluid interaction force and the particle position, the independent calculation of the fluid CFD model and the independent calculation of the soil DEM model are respectively performed. The simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 1 is characterized by the above.

9. The motion solution method of the fluid phase in the fluid CFD model is as follows. Here, The simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 1 is characterized by the above.

10. The motion control equation of the particles in the soil DEM model is as follows. Here, The simulation method for shield tail synchronous grout injection in shield construction based on CFD-DEM according to claim 1 is characterized by the above.

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