Method for calculating fluid force of coarse particle in debris flow channel and its application in critical starting identification

Abstract

The application discloses a method for measuring fluid force of coarse particles in debris flow channel and judging critical starting of coarse particles and application thereof. In view of the defect that the prior art does not consider the influence of non-Newtonian body characteristics of slurry and the'sinking' state of coarse particles on the change of critical state, the method for measuring fluid force of coarse particles is a fluid force calculation model fully considering the characteristics of slurry including flow state characteristics and the influence of the change thereof, and the fluid force obtained by measurement is the starting force of slurry on coarse particles which is comprehensively measured. The method for judging critical starting of coarse particles divides two problems of isolated coarse particles and associated coarse particles according to distribution characteristics, constructs moment balance under the fluid force environment of slurry for the former, and constructs moment balance under the fluid force and mutual contact force environment of coarse particles for the latter. The method provides a measurement and judgment scheme of the motion state of coarse particles considering the special flow state characteristics of slurry, the sinking depth of coarse particles, the position of the rotating center and other factors.

Description

Technical Field

[0001] This invention relates to a geological hazard measurement technology, and more particularly to a method for measuring the hydrodynamic response characteristic parameters of particulate matter in debris flow channels and its application. It belongs to the technical fields of electronic digital data processing, geological hazard monitoring, and prevention applicable to specific functions. Background Technology

[0002] Debris flows are three-phase fluids consisting of a large amount of mud, sand, rocks, and boulders, exhibiting viscous laminar or dilute turbulent flow patterns. The initiation and formation of debris flows is a result of the coupled effects of high-intensity water and soil conditions upstream of the gully. Therefore, strong hydrodynamic conditions are simultaneously generated within the gully during a debris flow, causing various solid materials to be carried into the flow. Among these, coarse particles originally contained in the loose sediment of the gully undergo high-speed movement due to transport, generating large-mass, large-volume, and high-velocity impact loads on downstream structures or buildings, thus amplifying the destructive force of the debris flow. Therefore, the identification and measurement of the motion state and characteristics of coarse particles during a debris flow are often crucial for debris flow hazard identification and are one of the fundamental issues in debris flow disaster prevention and control.

[0003] The existing technology, "Establishment and Calculation of Debris Flow Velocity Model in Wudongde Hydropower Station Reservoir Area Based on PPA" (Huang Miao, Jilin University, 2011), discloses a PPA (Power Process Analysis Model) for the initiation of debris flow particles. This model utilizes torque balance analysis under the limit equilibrium state of solid particles to solve the problem of calculating the critical conditions for debris flow particle initiation. The main shortcomings of this method are twofold: First, based on the analytical assumption that only the roughness of the debris flow channel bottom needs to be considered to determine the length of each lever arm during calculation, the method does not consider the influence of the rheological properties of the debris flow slurry on the torque balance, nor does it consider the special characteristics of the debris flow slurry as a non-Newtonian fluid exerting force on coarse particles during its movement. Second, the method does not consider that due to the weight of the coarse particles and the looseness of the channel bed, coarse particles are in a "trapped" state when they remain in the debris flow channel; therefore, its torque balance analysis system should not be simplified to a foundation similar to a solid horizontal surface. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a technical solution for measuring the movement state of coarse particles in debris flow channels, thereby identifying their initiation.

[0005] To achieve the above objectives, the present invention first provides a method for measuring groundwater level elevation, the technical solution of which is as follows.

[0006] A method for calculating the fluid dynamics of coarse particles in debris flow channels, characterized by:

[0007] First, conduct on-site investigations of the gullies to obtain basic data, including: gully characteristic parameters, debris flow movement characteristics under rainfall conditions, coarse particle characteristic parameters, and debris flow slurry characteristic parameters.

[0008] Secondly, using basic data, calculate the debris flow slurry pressure P, debris flow slurry velocity U, and debris flow slurry shear rate within the time T it takes for coarse particles to travel along the debris flow slurry to reach the runoff point in the channel. ;

[0009] Finally, the hydrodynamic forces of the debris flow slurry on the coarse particles were calculated based on the model. ,

[0010] Formula 1

[0011] In the formula, —The hydrodynamic force exerted on coarse particles by the debris flow slurry, in N.

[0012] - The gradient operator for the slurry pressure P in debris flow is constructed using the slurry pressure P.

[0013] k – Consistency coefficient of debris flow slurry, dimensionless, determined based on the characteristics of the debris flow slurry.

[0014] - Debris flow slurry shear rate, in m / s.

[0015] n – Debris flow slurry fluidity index, dimensionless, determined based on debris flow slurry characteristics.

[0016] - Yield stress of debris flow slurry, in Pa, determined based on the characteristics of the debris flow slurry.

[0017] ΔU – the Laplace operator for the velocity U of the debris flow slurry, constructed using the slurry velocity U.

[0018] V – Volume of coarse particles, in meters (m³) 3 Characteristic parameters of coarse particles.

[0019] The above-mentioned method for calculating the hydrodynamic forces of coarse particles in debris flow channels first involves obtaining various basic data through field investigations to prepare the input items for Model Equation 1. The basic data mainly includes the characteristics of the debris flow channel, the movement characteristics of the debris flow under rainfall conditions, the characteristics of coarse particles in the flow zone, and the characteristics of the debris flow slurry. Then, the pressure P and velocity U of the debris flow slurry at the location of the coarse particles are calculated using the basic data. Finally, Model Equation 1 is used to calculate the hydrodynamic forces exerted on the coarse particles by the debris flow slurry. Model 1 comprehensively considers the various main forces generated by the debris flow slurry on coarse particles, thus the calculated fluid forces are... This refers to the combined forces exerted by debris flow slurry on coarse particles. The main principle of the analytical framework of Model 1 is to treat the debris flow slurry as a non-Newtonian fluid. This is because fine particles within the channel move under the impact of runoff in the early stages of rainfall, forming the debris flow slurry. As fine particles are continuously incorporated, the rheological properties of the runoff change substantially, transforming it into a non-Newtonian fluid. Therefore, the influence of the change in runoff rheological properties must be considered in the analysis and calculation of the hydrodynamic forces exerted by the slurry on coarse particles. Model 1 effectively simulates this influence by introducing the rheological parameters of the debris flow slurry and gradient operators for pressure and velocity.

[0020] Based on the above-mentioned method for calculating the hydrodynamics of coarse particles in debris flow channels, this invention also provides a method for identifying the critical initiation of coarse particles in debris flow channels, the technical solution of which is as follows.

[0021] A method for identifying the critical initiation of coarse particles in debris flow channels, characterized by:

[0022] Step S100: Investigate the distribution of coarse particles in the debris flow channel and identify isolated coarse particles;

[0023] Step S200: Using the above-mentioned hydrodynamic calculation method for coarse particles in debris flow channels, calculate the solitary coarse particles. ;

[0024] Step S300: Calculate the fluid torque of the debris flow slurry on the solitary coarse particles. The resistance torque of solitary coarse particles to debris flow slurry ,

[0025] Formula 2

[0026] Formula 3

[0027] In the formula, , - They are respectively Components in the horizontal and vertical directions, in N.

[0028] R – Radius of coarse particles, in meters, determined based on the characteristic parameters of coarse particles.

[0029] α – Inclination angle of debris flow channel Based on the channel characteristic parameters,

[0030] β – The angle between the geometric analysis line oa and ray o for coarse particles. The straight line oa is the line connecting the center point o of the sphere and the center of rotation a, and the ray o is the ray passing through the center point o and perpendicular to the surface of the trench. This is determined based on the analysis of the characteristic parameters of the coarse particles.

[0031] G – Gravity of coarse particles, determined based on the characteristic parameters of coarse particles, in m / s². 2 ;

[0032] Step S400: Calculate the starting torque M of the solitary coarse particles, and determine whether the solitary coarse particles are in the critical state of starting with the debris flow slurry based on the critical state identification conditions expressed by M.

[0033] Formula 4.

[0034] The above-mentioned method for identifying the critical initiation of coarse particles in debris flow channels is based on the fluid dynamics calculation method for coarse particles in debris flow channels of this invention, and addresses the fluid dynamics of debris flow slurry acting on coarse particles. Based on the measurement problem, a torque balance equation for the rolling of coarse particles is further established to calculate the starting torque M of the coarse particles. The key point of this method is that for coarse particles stationary in the gully, due to their own weight and the looseness of the gully bed, they are essentially in a "trapped" state when stationary in the debris flow gully. Therefore, the torque balance system should simultaneously consider the position of the rotation center point a and the included angle β. β is affected by the depth of the coarse particles' subsidence within the debris flow gully and can be defined according to Equation 7, where h is the depth of the coarse particles' subsidence within the debris flow gully (in meters).

[0035] Formula 7

[0036] In the aforementioned method for identifying the critical initiation of coarse particles in debris flow channels, solitary coarse particles are determined based on the distribution characteristics of coarse particles in the channel. Based on the distribution of coarse particles in the channel's flow area obtained from field surveys, coarse particles in the channel are divided into two categories: one is solitary coarse particles, which refer to coarse particles that are distributed alone in the channel bed and not in contact with any other coarse particles; the other is associated coarse particles, which refer to N (N≥2) coarse particles that are distributed in the channel bed in a clustered and mutually contacting manner.

[0037] The above-mentioned method for identifying the critical initiation of coarse particles in debris flow channels solves the problem of identifying the initiation of isolated coarse particles in channels. Further optimization of this method is to solve the problem of identifying the critical initiation of coarse particles that are associated with each other in channels.

[0038] For coarse particles, we first establish the analytical framework of Newton's third law to calculate the interaction forces between the coarse particles. , The angle γ with the direction of gravity is then used to calculate the value of each associated coarse particle. Then, calculate the fluid torque of the debris flow slurry on each associated coarse particle according to Equations 5 and 6 respectively. The resistance torque of each associated coarse particle to the debris flow slurry Finally, the starting torque M of each associated coarse particle is calculated according to Equation 4, and the critical state identification condition expressed by M is used to determine whether the associated coarse particles are in the critical state of starting with the debris flow slurry.

[0039] Formula 5

[0040] Formula 6

[0041] In the formula, - Interaction forces between coarse particles, in N.

[0042] γ- The angle with the direction of gravity, .

[0043] The key to measuring the critical state of coarse particles is to consider the interaction forces generated between the coarse particles due to their contact. The influence on the torque balance among N coarse particles. The above method addresses this problem by constructing an analytical framework based on Newton's third law around the N associated coarse particles.

[0044] The present invention also provides an application scheme for the above-mentioned method for identifying the critical start-up of coarse particles in debris flow channels.

[0045] The application of the above-mentioned method for identifying the critical initiation of coarse particles in debris flow channels is characterized by its application to the monitoring of the initiation of coarse particles in debris flow channels, or to the monitoring and / or assessment of debris flow hazards.

[0046] In the above application scheme, the monitoring of coarse particles in debris flow channels can be either a monitoring method or a monitoring system.

[0047] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention starts from the analysis of the change process of precipitation runoff in the channel flow area to the formation of debris flow slurry. It finds that due to the continuous entrainment and influx of fine particles, the flow state characteristics of debris flow slurry undergo an essential change, forming non-Newtonian body characteristics, which greatly affects the role of slurry in changing the state of coarse particles. Based on this principle, the fluid force calculation method for coarse particles in debris flow channels of the present invention constructs a fluid force calculation model that fully considers the characteristics of debris flow slurry and their changes, including flow state characteristics. (2) The fluid force calculation method for coarse particles in debris flow channels of the present invention adopts a comprehensive force measurement of the fluid force of debris flow slurry on coarse particles. Compared with the prior art, which decomposes the effect of debris flow slurry on coarse particles into drag force, lifting force, etc. in multiple directions, the calculation is simplified and the calculation efficiency is improved. (3) The critical initiation identification method for coarse particles in debris flow channels of the present invention provides a method based on the distribution characteristics of coarse particles in the channel, which divides the initiation torque balance of coarse particles into two categories: isolated coarse particles and associated coarse particles. The former only considers the torque balance of coarse particles in the fluid dynamic environment of the slurry, while the latter further considers the torque balance in the environment of coarse particles in contact with each other. Compared with the existing technology, which only constructs the torque balance for isolated coarse particles, this method solves a new technical problem and has practical significance for complex channel environments. (4) The critical initiation identification method for coarse particles in debris flow channels of the present invention combines the characteristics of coarse particles' heavy weight and the looseness of the channel bed deposits to construct an initiation torque balance system that considers the sinking depth of coarse particles and the rotation center, which is more in line with the characteristics of changes in the state of coarse particles. Attached Figure Description

[0048] Figure 1 This is a schematic diagram illustrating the meaning of some parameters in the embodiment.

[0049] Figure 2 yes Figure 1 P-value and U-value curves for point b.

[0050] Figure 3 yes Figure 1 Point B ΔU curve diagram.

[0051] Figure 4 It is the coarse-grained particle of Example 1 Line graph.

[0052] Figure 5 This is the M-curve diagram of coarse particles in Example 1.

[0053] Figure 6 This is a schematic diagram illustrating the meaning of some parameters in Example 2.

[0054] Figure 7 yes Figure 6P-value and U-value curves for point b.

[0055] Figure 8 yes Figure 6 Point B ΔU curve diagram.

[0056] Figure 9 It is the coarse-grained particle of Example 2 Line graph.

[0057] Figure 10 This is the M-curve diagram of coarse particles in Example 2. Detailed Implementation

[0058] The preferred embodiments of the present invention will now be further described with reference to the accompanying drawings.

[0059] Example 1

[0060] like Figures 1-5 As shown, the method of the present invention is used to identify the critical initiation of coarse particles in a debris flow channel.

[0061] 1. Conduct on-site investigations to obtain basic data.

[0062] Obtain topographic maps of debris flow channels (through UAV 3D scanning or satellite imagery) and extract channel feature parameters.

[0063] By combining field observations of the gully with historical disaster data, characteristic parameters of debris flow movement at the gully runoff confluence point under rainfall conditions were determined, including the gully flow rate Q at the runoff confluence point or the debris flow slurry velocity at the runoff confluence point. .

[0064] Field surveys were conducted along the gully to obtain characteristic parameters for each coarse particle in the gully's flow area. Among these parameters was the average density of the coarse particles. This was determined through indoor testing following on-site sampling. In this example, coarse-grained objects were defined as large stones with a radius R ≥ 1m.

[0065] Fine particles of debris flow were collected from the gully in the field (preferably from the deposition area). These particles were then prepared into debris flow slurry through laboratory experiments, and the density of the debris flow slurry was measured. .

[0066] An indoor rheological experiment was conducted on debris flow slurry. The Herschel-Bulkley model for non-Newtonian fluids was used to describe the rheological properties of the debris flow slurry, with the density of the debris flow slurry substituted into the model. Data was collected to obtain rheological parameters of debris flow slurry, including yield viscosity. Consistency coefficient k, fluidity index n, yield stress .

[0067] Table 1 Basic Data Table

[0068]

[0069] Figure 1 This is a schematic diagram illustrating the meaning of some parameters in the embodiment. This indicates friction.

[0070] 2. Calculate the pressure P and velocity U of the debris flow slurry at the location of coarse particles.

[0071] Constructing the fluid momentum equations and continuity equations for debris flow slurries (the specific construction process can refer to existing technologies): Author of *Computational Methods in Fluid Dynamics (4th Edition)*, Springer Publishing, 2020. https: / / doi.org / 10.1007 / 978-3-319-99693-6 (Page 183), using basic data to determine the initial conditions of the equation (α, B, H, L, R, h, (x, y), l, , , ,k,n, , The equation outputs the following parameters: the pressure P of the debris flow slurry, the flow velocity U of the debris flow slurry, and the shear rate of the debris flow slurry. .

[0072] With coarse particles 1 moving at contact point b ( Figure 1 Taking midpoint b) as an example, Figure 2 yes Figure 1 P-value and U-value curves for point b.

[0073] 3. Calculate the hydrodynamic forces exerted on coarse particles by the debris flow slurry.

[0074] This embodiment measures the size of solitary coarse particles. .

[0075] Taking a solitary coarse particle (denoted as coarse particle 1) as an example, its specific characteristics include: the volume of the coarse particle V = 36.82 m³. 3 The radius of the coarse particles is R = 2.5 m, and the weight of the coarse particles is G = 103083.51 m / s². 2 The depth of the coarse particles in the debris flow channel is h = 1m; the position of the coarse particles in the debris flow channel (x, y); and the distance of the coarse particles from the runoff collection point is l = 50m.

[0076] Substituting the variables into Model 1, the fluid force exerted by the debris flow slurry on the coarse particle 1 is calculated and output. ,See Figure 2 In model 1, It is for P The calculated gradient is obtained by performing gradient calculations on the surface of coarse particles. ΔU is obtained by performing a Δ calculation on U, i.e., by performing a Laplace operation on U over the surface of coarse particles. This represents the shear rate of the debris flow slurry. It is calculated using the momentum equation and the continuity equation.

[0077] Figure 3 yes Figure 1 Point B ΔU curve diagram.

[0078] Figure 4 It is the coarse particles 1 in Example 1 Line graph.

[0079] 3. Calculate the size of solitary coarse particles ,

[0080] Calculate the fluid torque of the debris flow slurry on solitary coarse particles according to Equations 2 and 3 respectively. and its resistance torque to debris flow slurry The included angle β is calculated according to Equation 7.

[0081] Continuing with the example of coarse particle 1, the calculation data is omitted.

[0082] 4. Calculate the starting torque M of coarse particles

[0083] The starting torque M of the coarse particles is calculated according to Equation 4. Continuing with coarse particle 1 as an example, the change in starting torque M is shown in [reference needed]. Figure 5 . Figure 5 This is the M-curve diagram of coarse particles 1 in Example 1.

[0084] In this example, the critical state identification condition for coarse particles is expressed according to Equation 8.

[0085] Formula 8

[0086] Therefore, it was determined that coarse particles 1 would be initiated within the channel, specifically 2.43 seconds after the debris flow slurry reached the runoff rendezvous point.

[0087] Based on the above measurement results, the key time points of the impact and destructive changes of debris flow during the debris flow process can be determined.

[0088] Example 2

[0089] like Figures 6-10 As shown, the method of this invention is used to identify the critical initiation of coarse particles in a debris flow channel. This example uses the same channel environment as Example 1, and the same content will not be repeated. This example identifies the critical initiation of coarse particles associated with the channel.

[0090] Figure 6 This is a schematic diagram illustrating the meaning of some parameters in Example 2. This indicates friction.

[0091] 1. Calculate the hydrodynamic forces exerted on coarse particles by debris flow slurry.

[0092] For the coarse particles (N clustered coarse particles) that coexist in the channel, their characteristic parameters are determined respectively.

[0093] Taking a group of associated coarse particles (N=2) as an example, the associated coarse particle 1 (denoted as coarse particle G1) is located at (x1, y1) in the debris flow channel, and its characteristics are the same as those of coarse particle 1 in Example 1; the characteristics of associated coarse particle 2 (denoted as coarse particle G2) specifically include: volume V2 = 36.82 m³. 3 Radius R2 = 2.5 m, gravity G2 = 103083.51 m / s² 2 The depth of subsidence within the debris flow channel is h2 = 1 m, the location within the debris flow channel is (x2, y2), and the distance from the runoff collection point is l2 = 45 m.

[0094] The hydrodynamic forces of the debris flow slurry on each associated coarse particle were measured using the same method as in Example 1. .

[0095] With coarse particles G2 moving at contact point b ( Figure 6 Taking midpoint b) as an example, Figure 7 yes Figure 6 The P-value and U-value curves for point b. Figure 8 yes Figure 6 Point B ΔU curve diagram.

[0096] Figure 9 It is the coarse-grained particle of Example 2 Line graph.

[0097] 2. Calculate the associated coarse particles ,

[0098] For any group of coarse particles, establish a force equilibrium system among N clustered coarse particles according to Newton's third law, and calculate the interaction forces among the coarse particles. and determine The angle γ between the direction of gravity and the direction of gravity.

[0099] This example belongs to the case where N=2. Analysis framework The determination is relatively straightforward. When N>2, The determination of the force composition can be simplified by using the force composition method. That is, for any coarse particle that is accompanied by other particles, the force exerted on it by the other N-1 coarse particles from different directions will be combined into a single force composition. Then determine the included angle γ.

[0100] Calculate the fluid torque of the debris flow slurry on each associated coarse particle according to Equations 5 and 6 respectively. and its resistance torque to debris flow slurry .

[0101] Continuing with coarse particles G1 and G2 as examples, the calculations are determined. =0, γ=15º, and Calculation data omitted.

[0102] 3. Calculate the starting torque M of the associated coarse particles.

[0103] Calculate the starting torque M of coarse particles according to Formula 4. Figure 10 This is the M-curve diagram of coarse particles in Example 2.

[0104] In this example, the critical state identification condition for coarse particles is expressed according to Equation 8. Thus, coarse particle G2 can be initiated within the channel, starting 2.24 s after the debris flow slurry reaches the runoff recurrence point, while coarse particle G1 is initiated 2.31 s after the debris flow slurry reaches the runoff recurrence point.

[0105] Based on the above measurement results, the key time points of the impact and destructive changes of debris flow during the debris flow process can be determined.

Claims

1. A method for calculating the hydrodynamics of coarse particles in debris flow channels, characterized by: First, a field survey of the gully was conducted to obtain basic data, including: gully characteristic parameters, debris flow movement characteristics under rainfall conditions, coarse particle characteristic parameters, and debris flow slurry characteristic parameters. The debris flow slurry characteristic parameters included: collecting fine debris flow particle samples from the gully in the field, preparing debris flow slurry through indoor experiments, and measuring the density of the debris flow slurry. An indoor rheological experiment was conducted on debris flow slurry. The Herschel-Bulkley model for non-Newtonian fluids was used to describe the rheological properties of the debris flow slurry, with the density of the debris flow slurry substituted into the model. Data was collected to obtain rheological parameters of debris flow slurry, including yield viscosity. Consistency coefficient k, fluidity index n, yield stress ; Secondly, using basic data, calculate the debris flow slurry pressure P, debris flow slurry velocity U, and debris flow slurry shear rate within the time T it takes for coarse particles to travel along the debris flow slurry to reach the runoff point in the channel. ; Finally, the hydrodynamic forces of the debris flow slurry on the coarse particles were calculated based on the model. , Formula 1 In the formula, —The hydrodynamic force exerted on coarse particles by the debris flow slurry, in N. - The gradient operator for the slurry pressure P in debris flow is constructed using the slurry pressure P. k – Consistency coefficient of debris flow slurry, dimensionless, determined based on the characteristics of the debris flow slurry. - Debris flow slurry shear rate, in m / s. n – Debris flow slurry fluidity index, dimensionless, determined based on debris flow slurry characteristics. - Yield stress of debris flow slurry, in Pa, determined based on the characteristics of the debris flow slurry. ΔU – the Laplace operator for the velocity U of the debris flow slurry, constructed using the slurry velocity U. V – Volume of coarse particles, in meters (m³) 3 Characteristic parameters of coarse particles.

2. The method for calculating the hydrodynamics of coarse particles in debris flow channels according to claim 1, characterized in that: Construct the momentum and continuity equations for the fluid motion of the debris flow slurry, substitute the initial conditions into the equations, and use the equation outputs to obtain the pressure P, velocity U, and shear rate. .

3. The method for calculating the hydrodynamics of coarse particles in debris flow channels according to claim 2, characterized in that: In the initial conditions of the momentum equation and continuity equation for debris flow slurry fluid motion, the channel flow rate is... or debris flow slurry velocity It refers to the flow rate or debris flow velocity at the confluence of gully runoff under rainfall conditions.

4. A method for identifying the critical initiation of coarse particles in debris flow channels, characterized by: include: Step S100: Investigate the distribution of coarse particles in the debris flow channel and divide the coarse particles in the flow area into solitary coarse particles and associated coarse particles. For solitary coarse particles, perform steps S200a to S300a, and then perform step S400; for associated coarse particles, perform steps S200b to S30b, and then perform step S400. Step S200a: Using the hydrodynamic calculation method for coarse particles in debris flow channels as described in any one of claims 1 to 3, calculate the solitary coarse particles. ; Step S300a: Calculate the fluid torque of the debris flow slurry on the solitary coarse particles. The resistance torque of solitary coarse particles to debris flow slurry , Formula 2 Formula 3 In the formula, , - They are respectively Components in the horizontal and vertical directions, in N. R – Radius of coarse particles, in meters, determined based on the characteristic parameters of coarse particles. α – Inclination angle of debris flow channel Based on the channel characteristic parameters, β – The angle between the geometric analysis line oa and ray o for coarse particles. The straight line oa is the line connecting the center point o of the sphere and the center of rotation a, and the ray o is the ray passing through the center point o and perpendicular to the surface of the trench. This is determined based on the analysis of the characteristic parameters of the coarse particles. G – Gravity of coarse particles, determined based on the characteristic parameters of coarse particles, in m / s². 2 ; Step S200b: For any group of associated coarse particles, obtain the interaction forces between the associated coarse particles. , The angle γ with the direction of gravity is calculated using the hydrodynamic calculation method for coarse particles in debris flow channels as described in any of claims 1 to 3, to determine the hydrodynamic force of each associated coarse particle. ; Step S300b: Calculate the fluid torque of the debris flow slurry on each associated coarse particle. The resistance torque of each associated coarse particle to the debris flow slurry , Formula 5 Formula 6 In the formula, - Interaction forces between coarse particles, in N. γ- The angle with the direction of gravity, ; Step S400: Calculate the starting torque M of solitary coarse particles or associated coarse particles, and determine whether they are in the critical state of starting with the debris flow slurry based on the critical state identification conditions expressed by M. Formula 4.

5. The method for identifying the critical initiation of coarse particles in debris flow channels according to claim 4, characterized in that: The included angle β is calculated according to Equation 7. Formula 7 In the formula, h represents the depth of the coarse particles in the debris flow channel, in meters, which is determined based on the characteristic parameters of the coarse particles.

6. The method for identifying the critical initiation of coarse particles in debris flow channels according to claim 4, characterized in that: The critical state identification condition is expressed according to Equation 8. Formula 8.

7. The application of the critical initiation identification method for coarse particles in debris flow channels according to claim 4, characterized in that: It is used for monitoring the initiation of coarse particles in debris flow channels, or for monitoring and / or assessing the hazard of debris flows.

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