Flow velocity analysis method and system for preventing mud cakes from forming on excavation face of slurry shield, storage medium and slurry shield machine

Abstract

The invention discloses a slurry shield excavation face mud cake formation prevention flow velocity analysis method and system, a storage medium and a slurry shield tunneling machine. The method comprises the following steps that muck physical property parameters, slurry parameters and stratum parameters of current shield tunneling are obtained; the viscosity index, the undrained shear strength and the interfacial shear strength of the muck are obtained; muck adhesion force, muck cohesion force and fluid acting force borne by muck particles are obtained; establishing a critical flow velocity mathematical model of different starting modes under different working conditions; obtaining slurry critical flow rates of different starting modes under different working conditions; the critical flow velocity for preventing mud cake formation is obtained. The method can adapt to different working conditions and different starting modes, the critical flow velocity for preventing the mud cake from forming is rapidly determined, the tedious process of frequently adjusting the flow velocity of mud in traditional construction is avoided, and the construction efficiency is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of slurry shield machines, and in particular to a flow velocity analysis method, system, storage medium and slurry shield machine for preventing mud cake formation on an excavation face of a slurry shield. Background Art

[0002] During the construction of slurry shield, especially when excavating in viscous strata, the high viscosity of the slag makes it very easy for it to self-agglomerate or adhere to the cutterhead and tool surface. These two phenomena are the main mechanisms for the formation of mud cakes. Once mud cakes appear, they will not only reduce the cutting efficiency of the cutterhead, but also increase tool wear and may even cause construction safety problems. Therefore, preventing the formation of mud cakes is crucial to ensure the smooth progress of shield construction.

[0003] If the mud on the excavation surface has good fluidity, the fluid power provided by the mud movement can carry the debris and separate it from the cutterhead, thus preventing the debris from forming mud cakes. However, in actual construction, due to the large differences in geological conditions of different viscous strata, the requirements for mud fluidity are also different. It is difficult to set a fixed flow rate parameter to meet the complex scenarios affected by multiple factors. It is usually necessary to continuously adjust the mud flow rate during the construction process to adapt to different situations, but this will undoubtedly consume a lot of time and energy, seriously affecting construction efficiency. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield includes the following steps: S1, obtaining the physical property parameters of the slag, mud parameters and formation parameters of the current shield excavation; S2, obtaining the viscosity index, undrained shear strength and interface shear strength of the slag; S3, obtaining the adhesion force, cohesion force and fluid force on the slag particles; S4, establishing different starting modes under different working conditions according to the force balance of the slag particles at the critical start. The working conditions include the slag adhesion working condition and the slag cohesion working condition, and the starting modes include lifting starting, sliding starting and rolling starting; S5, obtaining the mud critical flow rate of different starting modes under different working conditions according to the critical flow rate mathematical models of different starting modes under different working conditions; S6, obtaining the minimum mud critical flow rate of slag starting under different working conditions; and taking the maximum value of the minimum mud critical flow rate of slag starting under different working conditions as the critical flow rate to prevent mud cake formation.

[0006] Furthermore, the slag physical property parameters include: slag density, particle size, Poisson's ratio, plasticity index, water content, liquid limit of slag; the mud parameters include: mud density, viscosity, Reynolds number; the formation parameters include: water and soil pressure.

[0007] Furthermore, the viscosity index of the slag is , Undrained Shear Strength , the interface shear strength a is obtained according to the following formula: ; ; ; Indicates the viscosity index of the slag. represents the liquid limit of the soil. Indicates the soil moisture content, It represents the plasticity index of the soil. It represents the undrained shear strength of the soil. represents the actual normal pressure, and a represents the interfacial shear strength of the slag soil; , , are the first correlation coefficient, the second correlation coefficient and the third correlation coefficient of undrained shear strength, respectively; , , They are the fourth, fifth and sixth correlation coefficients of the interface shear strength respectively.

[0008] Furthermore, the soil cohesion and soil adhesion Obtained by the following formula: ; ; A It indicates the contact area when the slag undergoes shear failure.

[0009] Further, step S4 includes: Establish the critical flow velocity mathematical model of lifting start-up under the condition of soil cohesion: ; The mathematical model of critical velocity of sliding start in soil cohesion condition is established: ; The mathematical model of critical velocity of rolling start under soil cohesion condition is established: ; Establish the critical flow velocity mathematical model of lifting start-up under soil adhesion condition: ; The mathematical model of critical velocity of sliding start in soil adhesion condition is established: ; The mathematical model of critical flow velocity of rolling start under soil adhesion condition is established: ; It is the critical flow velocity of the slurry for lifting start in the condition of soil cohesion; Critical flow rate of slurry during sliding start-up under soil cohesion condition; It is the critical velocity of slurry for rolling start in the condition of soil cohesion; The critical flow rate of mud for lifting start in the condition of soil adhesion; The critical velocity of the slurry during sliding start in the condition of soil adhesion; The critical velocity of the slurry for rolling start in the condition of soil adhesion; It represents the angle between the mud flow direction and the gravity direction. Indicates the angle between the movement direction of the soil particles and the gravity direction; is the density of soil, is the normal water and soil pressure; is the lift coefficient, It means that the soil is dragged by the fluid. It means that the soil is lifted by the fluid; represents the mud density, D represents the diameter of soil particles, represents the drag force coefficient; The gravity of the soil, is the buoyancy of the soil.

[0010] Further, step S6 specifically includes: The minimum starting flow rate under the condition of soil cohesion is obtained according to the following formula: : ; The minimum starting flow rate under soil adhesion conditions is obtained according to the following formula: : ; The critical flow rate to prevent mud cake formation is obtained according to the following formula: .

[0011] Furthermore, the fluid force acting on the soil particles is obtained by the following formula: ; Re Reynolds number.

[0012] The present invention also provides a flow velocity analysis system for preventing mud cake formation on the excavation face of a slurry shield, comprising: a parameter acquisition module for acquiring soil physical property parameters, mud parameters and stratum parameters of the current shield excavation; an intermediate parameter acquisition module for acquiring the viscosity index, undrained shear strength and interface shear strength of the soil; a force acquisition module for acquiring soil adhesion, soil cohesion and the fluid force on soil particles; a model establishment module for establishing different starting modes under different working conditions according to the force balance at the critical start of soil particles under different working conditions. The invention discloses a multi-operating condition critical flow rate mathematical model for the starting mode; the operating conditions include the slag adhesion operating condition and the slag cohesion operating condition, and the starting modes include lifting starting, sliding starting and rolling starting; a multi-operating condition critical flow rate acquisition module, which is used to obtain the mud critical flow rate of different starting modes under different operating conditions according to the critical flow rate mathematical model of different starting modes under different operating conditions; a critical flow rate acquisition module for preventing mud cake formation, which is used to obtain the minimum mud critical flow rate for slag starting under different operating conditions; and the maximum value of the minimum mud critical flow rate for slag starting under different operating conditions is used as the critical flow rate for preventing mud cake formation.

[0013] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the flow velocity analysis method for preventing mud cake formation on the excavation face of a mud-water shield are implemented.

[0014] The present invention also provides a slurry shield machine, comprising a flow rate analysis system for preventing mud cake formation on the excavation surface of the slurry shield machine.

[0015] The present invention has the following beneficial effects: By obtaining the viscosity index, undrained shear strength, interface shear strength, adhesion, cohesion and fluid forces of the slag, the mechanical properties of the slag under different working conditions can be accurately analyzed, providing key data support for the establishment of the critical flow velocity mathematical model, and improving the scientificity and practicality of the model. By establishing the critical flow velocity mathematical model of different starting modes under different working conditions, various possible situations of the slag in actual construction can be fully considered. The establishment of the model of multiple working conditions and multiple starting modes makes the analysis results closer to the actual construction situation, adapts to the situation of different starting modes under different working conditions, and improves the pertinence and effectiveness of preventing the formation of mud cakes. By obtaining the critical flow velocity mathematical model of different starting modes under different working conditions, the mud critical flow velocity of different starting modes under different working conditions is obtained, and the minimum mud critical flow velocity of slag starting under different working conditions is further obtained, which can scientifically determine the mud critical flow velocity to prevent the formation of mud cakes. It avoids the tedious process of frequently adjusting the mud flow rate in traditional construction, significantly improves construction efficiency and reduces construction risks: effectively prevents the formation of mud cakes, reduces the reduction of cutterhead cutting efficiency, increased tool wear and construction safety hazards caused by mud cakes, and ensures the smooth progress of shield construction. It provides scientific decision-making basis for construction personnel, reduces the uncertainty caused by human experience and judgment, and improves the controllability and stability of the construction process.

[0016] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of the overall process of the present invention. DETAILED DESCRIPTION

[0018] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0021] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] Please refer to Figure 1 A flow velocity analysis method for preventing mud cake formation on a slurry shield excavation face in a preferred embodiment of the present invention comprises steps S1, S2, S3, S4, S5 and S6.

[0023] S1, obtain the soil physical parameters, mud parameters and formation parameters of the current shield tunneling.

[0024] S2, obtain the viscosity index, undrained shear strength and interface shear strength of the soil.

[0025] S3, obtain the soil adhesion, soil cohesion and fluid force acting on soil particles. The fluid is mud.

[0026] S4, according to the force balance of different starting modes under different working conditions of slag particles at critical starting, a mathematical model of critical flow rate of different starting modes under different working conditions is established; the working conditions include slag adhesion conditions and slag cohesion conditions, and the starting modes include lifting start, sliding start and rolling start. Critical start means that the slag is in a state of force balance, and if the mud force becomes smaller at this time, the slag cannot be started, that is, it is in a critical state between starting and not starting the slag.

[0027] S5, according to the critical flow rate mathematical model of different starting modes under different working conditions, the critical flow rate of mud under different starting modes under different working conditions is obtained.

[0028] S6, obtain the minimum critical mud flow rate for starting the slag under different working conditions; the minimum critical mud flow rate is the minimum value of the critical mud flow rates of multiple starting methods under the same working condition, that is, under this working condition, only one method of starting the slag needs to be implemented, and the slag will not adhere to the surface of the cutter disc to form a mud cake, thereby preventing the mud cake. Therefore, it is only necessary to take the minimum value of the critical mud flow rates of multiple starting methods under the same working condition as the critical mud flow rate for preventing mud cake under this working condition, so as to avoid excessive flow rate judgment and increase in energy consumption. The maximum value of the minimum critical mud flow rate for starting the slag under different working conditions is used as the critical flow rate for preventing mud cake formation, that is, the flow rate meets the critical flow rate for preventing mud formation under different working conditions, which can adapt to different working conditions and ensure the effect of preventing mud.

[0029] A flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield in a preferred embodiment provided by the present invention can accurately analyze the mechanical properties of the slag under different working conditions by obtaining the viscosity index, undrained shear strength, interface shear strength, adhesion force, cohesion and fluid force on the slag particles of the slag, and provide key data support for establishing a critical flow velocity mathematical model, thereby improving the scientificity and practicality of the model. By establishing a critical flow velocity mathematical model for different starting modes under different working conditions, various possible situations of the slag in actual construction can be fully considered. The establishment of a model for multiple working conditions and multiple starting modes makes the analysis results closer to the actual construction situation, adapts to the situation of different starting modes under different working conditions, and improves the pertinence and effectiveness of preventing mud cake formation. By obtaining the critical flow velocity mathematical model for different starting modes under different working conditions, and further obtaining the minimum critical flow velocity of mud for slag starting under different working conditions, the critical flow velocity of mud for preventing mud cake formation can be scientifically determined. It avoids the tedious process of frequently adjusting the mud flow rate in traditional construction, significantly improves construction efficiency and reduces construction risks: effectively prevents the formation of mud cakes, reduces the reduction of cutterhead cutting efficiency, increased tool wear and construction safety hazards caused by mud cakes, and ensures the smooth progress of shield construction. It provides scientific decision-making basis for construction personnel, reduces the uncertainty caused by human experience and judgment, and improves the controllability and stability of the construction process.

[0030] In a specific embodiment of the present invention, the slag physical property parameters include: slag density, particle size, Poisson's ratio, plasticity index, water content, liquid limit of slag; the mud parameters include: mud density, viscosity, Reynolds number; the formation parameters include: water and soil pressure.

[0031] The viscosity index of the slag , Undrained Shear Strength , the interface shear strength a is obtained according to the following formula: ; ; ; Indicates the viscosity index of the slag. represents the liquid limit of the soil. Indicates the soil moisture content, It represents the plasticity index of the soil. It represents the undrained shear strength of the soil. represents the actual normal pressure, and a represents the interfacial shear strength of the slag soil; , , They are the first correlation coefficient, the second correlation coefficient and the third correlation coefficient of undrained shear strength, which can be obtained by fitting according to the experiment; , , are the fourth correlation coefficient, the fifth correlation coefficient and the sixth correlation coefficient of the interface shear strength, respectively, and can be obtained by fitting according to experiments. Specifically, in one embodiment, ; .in, .

[0032] Specifically, the soil cohesion and soil adhesion Obtained by the following formula: ; ; A It indicates the contact area when the soil is sheared. It represents the cohesive force between soil particles. Represents the adhesion force between soil particles and metal interface.

[0033] Contact area when the soil is sheared A can The specific steps are as follows: According to the Hertz elastic contact theory, the calculation model of slag particles is established assuming that the slag material is uniform, isotropic and completely elastic; based on the ANSYS software, the elastic modulus, Poisson's ratio, density and other parameters of the slag are set, and full displacement constraints are imposed on the contact nodes, and zero displacement constraints in the X direction are imposed on all nodes with an X coordinate of 0, and zero displacement constraints in the Y direction are imposed on all nodes with a Y coordinate of 0; loads are applied to the top nodes of the particles, and the load values ​​are set according to the normal pressure and the size of the slag; in the ANSYS post-processing, a command stream is written to calculate the particle contact radius, and then the particle contact area is calculated.

[0034] In some embodiments of the present invention, the fluid force on the soil particles is obtained by the following formula: ; ; ; represents the mud density, D represents the diameter of soil particles, is the drag coefficient, represents the flow rate of the mud fluid, Re is the Reynolds number, is the lift coefficient, It means that the soil is dragged by the fluid. Indicates that the soil is lifted by the fluid. and The formula can be used as the basis for the formula for force balance calculation in the subsequent step S4.

[0035] In some embodiments of the present invention, step S4 includes: Establish the critical flow velocity mathematical model of lifting start-up under the condition of soil cohesion: ; and The excavation surface is perpendicular to the cutter disc. At this time, the slag is in a force balance, and this balance is fragile. The mud flow rate only needs to be maintained at or greater than this time, and the slag will start to separate the cutter disc in a lifting manner.

[0036] The mathematical model of critical velocity of sliding start in soil cohesion condition is established: ; That is, the component of the difference between gravity and buoyancy in the sliding direction of the slag particles plus the component of the drag force of the fluid on the slag in the sliding direction of the slag particles is equal to the cohesive force of the slag. At this time, the slag is in force balance, and the mud flow rate only needs to be maintained at or greater than this time, and the slurry will start to separate in a sliding manner.

[0037] The mathematical model of critical velocity of rolling start under soil cohesion condition is established: .

[0038] When the soil rolling starts at the critical state, the resultant torque for: =0.

[0039] That is, the sum of the drag force of the fluid on the slag in the rolling direction of the slag particles, the difference between gravity and buoyancy in the rolling direction of the slag particles, and the moment of the lifting force of the fluid on the slag is equal to the sum of the normal water-soil pressure on the slag and the moment of the cohesive force of the slag. At this time, the mud flow rate only needs to be maintained at this time or greater than this time, and the slag will start to separate in a rolling manner.

[0040] Establish the critical flow velocity mathematical model of lifting start-up under soil adhesion condition: ; The critical flow velocity of mud for lifting start in adhesion condition and cohesion condition is the same.

[0041] The mathematical model of critical velocity of sliding start in soil adhesion condition is established: ; The mathematical model of critical flow velocity of rolling start under soil adhesion condition is established: ; It is the critical velocity of slurry for lifting start in the condition of soil cohesion; Critical velocity of slurry during sliding start-up under soil cohesion condition; It is the critical velocity of slurry for rolling start in the condition of soil cohesion; The critical flow rate of mud for lifting start in the condition of soil adhesion; The critical velocity of the slurry during sliding start in the condition of soil adhesion; The critical velocity of the slurry for rolling start in the condition of soil adhesion; It represents the angle between the mud flow direction and the gravity direction. Indicates the angle between the movement direction of the soil particles and the gravity direction; is the density of soil, is the normal soil and water pressure; represents the lifting force coefficient, which can be obtained through experimental fitting. It means that the soil is dragged by the fluid. It means that the soil is lifted by the fluid; represents the density of mud, D represents the diameter of soil particles, represents the drag force coefficient; The gravity of the soil, is the buoyancy of the soil. ; In the above formula, except , , , , and These six quantities are unknown, and the rest are known or measurable. , , , , and These six quantities.

[0042] In some embodiments of the present invention, step S6 specifically includes: The minimum starting flow rate under the condition of soil cohesion is obtained according to the following formula: : ; The minimum starting flow rate under soil adhesion conditions is obtained according to the following formula: : ; The critical flow rate to prevent mud cake formation is obtained according to the following formula : .

[0043] When the difference between gravity and buoyancy is greater than cohesion or adhesion, it means that the debris can fall off automatically. When the difference between gravity and buoyancy is less than cohesion or adhesion, mud fluid is needed to drive the debris to fall off and reduce the formation of mud cake. and This means that taking the minimum value of the critical flow rate of mud in the three starting modes under the same working conditions can at least meet the requirements of one starting mode, thus achieving slag starting and reducing mud cake formation.

[0044] The present invention also provides a flow rate analysis system for preventing mud cake formation on the excavation face of a mud-water shield, comprising a parameter acquisition module, a force acquisition module, a model building module, a multi-condition critical flow rate acquisition module and a critical flow rate acquisition module for preventing mud cake formation.

[0045] The parameter acquisition module is used to obtain the physical parameters of the slag, mud parameters and formation parameters of the current shield tunneling; the intermediate parameter acquisition module is used to obtain the viscosity index, undrained shear strength and interface shear strength of the slag; the force acquisition module is used to obtain the adhesion force, cohesion force and fluid force on the slag particles; the model establishment module is used to establish the critical flow rate mathematical model of different starting methods under different working conditions according to the force balance of the slag particles at the critical start of different starting methods under different working conditions; the working The conditions include the slag adhesion condition and the slag aggregation condition, and the starting methods include lifting start, sliding start and rolling start; a multi-condition critical flow rate acquisition module is used to obtain the mud critical flow rate of different starting methods under different working conditions according to the critical flow rate mathematical model of different starting methods under different working conditions; a critical flow rate acquisition module for preventing mud cake formation is used to obtain the minimum mud critical flow rate for slag starting under different working conditions; the maximum value of the minimum mud critical flow rate for slag starting under different working conditions is used as the critical flow rate for preventing mud cake formation.

[0046] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the flow velocity analysis method for preventing mud cake formation on the excavation face of a mud-water shield are implemented.

[0047] The present invention also provides a slurry shield machine, comprising a flow rate analysis system for preventing mud cake formation on the excavation surface of the slurry shield machine.

[0048] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield, characterized in that: The steps include: S1, obtaining the soil physical parameters, mud parameters and formation parameters of the current shield tunneling; S2, obtain the viscosity index, undrained shear strength and interface shear strength of the soil; S3, obtaining the soil adhesion force, soil cohesion force and fluid force acting on soil particles; S4, establishing a critical flow rate mathematical model of different starting modes under different working conditions according to the force balance at critical starting of different starting modes under different working conditions of slag particles; the working conditions include slag adhesion working conditions and slag cohesion working conditions, and the starting modes include lifting starting, sliding starting and rolling starting; S5, obtaining the critical flow velocity of the mud of different starting modes under different working conditions according to the critical flow velocity mathematical model of different starting modes under different working conditions; S6, obtaining the minimum critical flow rate of mud for starting the slag under different working conditions; taking the maximum value of the minimum critical flow rate of mud for starting the slag under different working conditions as the critical flow rate for preventing mud cake formation.

2. The flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield according to claim 1 is characterized in that: The slag physical property parameters include: slag density, particle size, Poisson's ratio, plasticity index, water content, and liquid limit of slag; the mud parameters include: mud density, viscosity, and Reynolds number; the formation parameters include: water and soil pressure.

3. The flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield according to claim 2 is characterized in that: The viscosity index of the slag , Undrained Shear Strength , the interface shear strength a is obtained according to the following formula: ； ； ； Indicates the viscosity index of the slag. represents the liquid limit of the soil. Indicates the soil moisture content, It represents the plasticity index of the soil. It represents the undrained shear strength of the soil. represents the actual normal pressure, and a represents the interfacial shear strength of the slag soil; , , are the first correlation coefficient, the second correlation coefficient and the third correlation coefficient of undrained shear strength, respectively; , , They are the fourth, fifth and sixth correlation coefficients of the interface shear strength respectively.

4. The flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield according to claim 3 is characterized in that: The soil cohesion and soil adhesion Obtained by the following formula: ; ； A It indicates the contact area when the slag undergoes shear failure.

5. The flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield according to claim 4 is characterized in that: Step S4 includes: Establish the critical flow velocity mathematical model of lifting start-up under the condition of soil cohesion: ； The mathematical model of critical velocity of sliding start in soil cohesion condition is established: ； The mathematical model of critical velocity of rolling start under soil cohesion condition is established: ； Establish the critical flow velocity mathematical model of lifting start-up under soil adhesion condition: ； The mathematical model of critical velocity of sliding start in soil adhesion condition is established: ； The mathematical model of critical flow velocity of rolling start under soil adhesion condition is established: ； It is the critical velocity of slurry for lifting start in the condition of soil cohesion; Critical velocity of slurry during sliding start-up under soil cohesion condition; It is the critical velocity of slurry for rolling start in the condition of soil cohesion; The critical flow rate of mud for lifting start in the condition of soil adhesion; The critical velocity of the slurry during sliding start in the condition of soil adhesion; The critical velocity of the slurry for rolling start in the condition of soil adhesion; It represents the angle between the mud flow direction and the gravity direction. Indicates the angle between the movement direction of the soil particles and the gravity direction; is the density of the soil, is the normal water and soil pressure; is the lift coefficient, It means that the soil is dragged by the fluid. It means that the soil is lifted by the fluid; represents the mud density, D represents the diameter of soil particles, represents the drag force coefficient; The gravity of the soil, is the buoyancy of the soil.

6. The flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield according to claim 5 is characterized in that: Step S6 specifically includes: The minimum starting flow rate under the condition of soil cohesion is obtained according to the following formula: : ； The minimum starting flow rate under soil adhesion conditions is obtained according to the following formula: : ； The critical flow rate to prevent mud cake formation is obtained according to the following formula: 。 7. The flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield according to claim 5, characterized in that: The fluid force on the soil particles is obtained by the following formula: ； Re Reynolds number.

8. A flow velocity analysis system for preventing mud cake formation on the excavation face of a slurry shield, used to implement the flow velocity analysis method for preventing mud cake formation on the excavation face of a slurry shield as claimed in any one of claims 1 to 7, characterized in that: include: Parameter acquisition module, used to obtain the soil physical parameters, mud parameters and formation parameters of the current shield tunneling; The intermediate parameter acquisition module is used to obtain the viscosity index, undrained shear strength and interface shear strength of the slag; A force acquisition module is used to obtain the adhesion force of the slag, the cohesion force of the slag and the fluid force acting on the slag particles; A model building module is used to establish a critical flow rate mathematical model of different starting modes under different working conditions according to the force balance at the critical start of different starting modes under different working conditions of slag particles; the working conditions include slag adhesion working conditions and slag cohesion working conditions, and the starting modes include lifting start, sliding start and rolling start; A multi-operating condition critical flow rate acquisition module is used to obtain the critical flow rate of mud under different operating conditions and different starting modes according to the critical flow rate mathematical model under different operating conditions and different starting modes; The critical flow rate acquisition module for preventing mud cake formation is used to obtain the minimum mud critical flow rate for starting slag under different working conditions; the maximum value of the minimum mud critical flow rate for starting slag under different working conditions is used as the critical flow rate for preventing mud cake formation.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the flow velocity analysis method for preventing mud cake formation on the excavation face of a mud shield according to any one of claims 1 to 7 are implemented.

10. A slurry shield machine, characterized in that: It includes the flow rate analysis system for preventing mud cake formation on the excavation face of a mud-water shield as described in claim 8.

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