Debris flow channel coarse particle fluid force measuring and calculating and critical starting identifying method and application

Abstract

The invention discloses a debris flow channel coarse particle fluid force measuring and calculating and critical starting identifying method and application. Aiming at the defect that in the prior art, the influence of non-Newtonian fluid characteristics of slurry and the influence of the'falling 'state of the coarse particles on the critical state change of the slurry are not considered, the method for measuring and calculating the fluid force of the coarse particles is a fluid force calculation model which fully considers the slurry characteristics including the flow state characteristics and the influence of the change of the slurry characteristics; the measured fluid force is the starting acting force of the comprehensively measured slurry on the coarse particles. According to the coarse particle critical starting identification method, two kinds of problems of isolated coarse particles and associated coarse particles are divided according to distribution characteristics, the isolated coarse particles construct moment balance in a slurry fluid force environment, and the associated coarse particles construct moment balance in a fluid force and coarse particle mutual contact acting force environment. The method provided by the invention provides a scheme for measuring and identifying the motion state of the coarse particles in consideration of factors such as special flow state characteristics of the slurry, sinking depth of the coarse particles and the position of a rotating center.

Description

Technical Field

[0001] The present invention relates to a geological disaster measurement technology, in particular to a measurement method and application of hydrodynamic response characteristic parameters of particulate matter in debris flow channels. It belongs to the technical fields of electrical digital data processing applicable to specific functions, geological disaster monitoring and prevention. Background Art

[0002] Debris flow is a solid-liquid-gas three-phase fluid containing a large amount of sediment, stones and boulders, and is in a moving state such as viscous laminar flow or dilute turbulent flow. The initiation and formation of debris flow are the results of the coupling action of high-intensity water and soil conditions in the upper reaches of the channel. Therefore, along with the occurrence of debris flow, strong hydrodynamic conditions will be generated in the channel at the same time, causing various solids in the channel to be carried into the debris flow. Among them, the coarse particles originally staying in the loose accumulations in the channel move at high speed due to the transportation effect, generating impact loads with large mass, large volume and high speed on downstream structures or buildings, and increasing the destructive power of debris flow. Therefore, the motion state, characteristic identification and measurement of coarse particles during debris flow often become an important basis for debris flow hazard identification and one of the basic problems in debris flow disaster prevention.

[0003] The prior art "Establishment and calculation of debris flow velocity model in the reservoir area of Wudongde Hydropower Station based on PPA" discloses a starting force analysis model PPA for debris flow to transport and carry particles, and uses the moment balance analysis under the limit equilibrium state of the solid particle force to solve the problem of measuring the critical conditions for debris flow particle initiation. Based on the analysis assumption that only the roughness of the debris flow channel bottom needs to be considered to determine the length of each force arm during the calculation of the force arm, the method does not consider the influence of the rheological properties of the debris flow slurry on the moment balance, nor does it consider the particularity of the force exerted on the coarse particles by the debris flow slurry as a non-Newtonian fluid during the movement process; on the other hand, the method does not consider that due to the self-weight of the coarse particles and the looseness of the channel bed, the coarse particles are in a "sunk" state when staying in the debris flow channel, so the moment balance analysis system should not be simplified based on a similar solid horizontal plane. Summary of the Invention

[0004] The purpose of the present invention is to provide a technical solution for measuring the motion state of coarse particles in a debris flow channel and thus identifying its initiation in view of the deficiencies of the prior art.

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

[0006] A method for calculating the hydrodynamic force of coarse particles in a debris flow channel, characterized in that:

[0007] First, conduct a field investigation of the gully to obtain basic data of the gully. The basic data includes: gully characteristic parameters, debris flow movement characteristics under rainfall conditions, coarse particle characteristic parameters, and debris flow slurry characteristic parameters.

[0008] Secondly, use the basic data to calculate the debris flow slurry pressure P, debris flow slurry velocity U, and debris flow slurry shear rate at the time T when the position of the coarse particles moves along the debris flow slurry to reach the runoff confluence point of the gully.

[0009] Finally, calculate the debris flow slurry hydrodynamic force F acting on the coarse particles according to the model. IB ,

[0010]

[0011] In the formula, F IB —the debris flow slurry hydrodynamic force acting on the coarse particles, unit N,

[0012] -the gradient operator of the debris flow slurry pressure P, constructed using the slurry pressure P,

[0013] k-the consistency coefficient of the debris flow slurry, dimensionless, determined according to the debris flow slurry characteristics,

[0014] —the debris flow slurry shear rate, unit m / s,

[0015] n-the flowability index of the debris flow slurry, dimensionless, determined according to the debris flow slurry characteristics,

[0016] τ 0 -the yield stress of the debris flow slurry, unit Pa, determined according to the debris flow slurry characteristics,

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

[0018] V-the volume of the coarse particles, unit m 3 , the coarse particle characteristic parameters.

[0019] The above method for calculating the hydrodynamic force of coarse particles in a debris flow gully first obtains various basic data through field investigations and prepares each input item of Model Equation 1. The basic data mainly includes the characteristics of the debris flow gully, the movement characteristics of the debris flow under rainfall conditions, the characteristics of the coarse particles in the flow-through area, and the characteristics of the debris flow slurry. Then, use the basic data to calculate the debris flow slurry pressure P and debris flow slurry velocity U at the position of the coarse particles. Finally, use Model Equation 1 to calculate the debris flow slurry hydrodynamic force F acting on the coarse particles. IB . Model Equation 1 comprehensively considers various main acting forces generated by the debris flow slurry acting on the coarse particles. Therefore, the calculated hydrodynamic force FIB It is the combined force exerted by the debris flow slurry on the coarse particles. The main principle of the analysis framework of Model 1 is as follows: The debris flow slurry is regarded as a non-Newtonian fluid. This is because, at the initial stage of rainfall, the fine particles in the gully are impacted by runoff and start to move, forming part of the debris flow slurry. As more and more fine particles are incorporated, the rheological properties of the runoff change substantially and become a non-Newtonian fluid. Therefore, in the analysis and measurement of the liquid force exerted by the slurry on the coarse particles, the impact caused by the change in the rheological properties of the runoff must be considered. Model 1 effectively simulates this impact by introducing the rheological parameters of the debris flow slurry and the gradient operators of pressure and velocity.

[0020] Based on the above method for measuring the flow force of coarse particles in a debris flow gully, the present invention also provides a method for identifying the critical starting condition of coarse particles in a debris flow gully. The technical solution is as follows.

[0021] A method for identifying the critical starting condition of coarse particles in a debris flow gully, characterized in that:

[0022] Step S100: Investigate the distribution of coarse particles in the debris flow gully and determine the solitary coarse particles;

[0023] Step S200: Use the method for measuring the flow force of coarse particles in a debris flow gully according to any one of claims 1 to 5 to measure the F of the solitary coarse particles IB ;

[0024] Step S300: Calculate the torque M of the debris flow slurry acting on the solitary coarse particles f , the resistance torque M of the solitary coarse particles to the debris flow slurry 0 ,

[0025] M f = F ul R sin(β - α) + F ht R cos(β - α) Equation 2

[0026] M 0 = GR sin(β - α) Equation 3

[0027] In the formula, F ul , F ht - are the components of F IB in the horizontal direction and the vertical direction respectively, with the unit of N,

[0028] R - the radius of the coarse particle, with the unit of m, determined according to the characteristic parameters of the coarse particle,

[0029] α - the inclination angle of the debris flow gully, with the unit of °, determined according to the characteristic parameters of the gully,

[0030] β - The angle between the coarse particle geometric analysis straight line oa and the ray o, unit: °. The straight line oa is the line connecting the sphere center point o and the rotation center point a. The ray o is the ray passing through the sphere center point o and perpendicular to the groove bed surface. It is determined based on the analysis of the coarse particle characteristic parameters.

[0031] G - gravity of coarse particles, determined by the characteristic parameters of coarse particles, unit: m / s 2 ;

[0032] Step S400, calculating the starting torque M of the orphan coarse particle, and judging whether the orphan coarse particle is in a critical state of starting with the debris flow slurry according to the critical state judgment condition expressed by M,

[0033] M=M f -M 0 Formula 4.

[0034] The above-mentioned method for identifying the critical start of coarse particles in debris flow channels is based on the method for calculating the fluid force of coarse particles in debris flow channels of the present invention. IB Based on the measurement problem, the moment balance equation of 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 the coarse particles staying in the channel, due to the self-weight of the coarse particles and the looseness of the channel bed, the coarse particles are actually in a "trapped" state when they are stationary in the debris flow channel. Therefore, the moment balance system should consider the position of the rotation center point a and the angle β at the same time. β is affected by the sinking depth of the coarse particles in the debris flow channel and can be defined according to formula 7, where h is the sinking depth of the coarse particles in the debris flow channel (unit: m).

[0035]

[0036] In the above-mentioned identification method of 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. According to the distribution of coarse particles in the channel flow area obtained in the channel field survey, the coarse particles in the channel are divided into two categories: one is solitary coarse particles, which refer to coarse particles distributed alone in the channel bed and not in contact with any coarse particles; the other is associated coarse particles, which refer to N (N≥2) coarse particles distributed in the channel bed in a clustered and mutually contacting manner.

[0037] The above-mentioned method for identifying the critical start of coarse particles in debris flow channels solves the problem of identifying the start of solitary coarse particles in the channel, and its further optimization is to solve the problem of identifying the critical start of associated coarse particles in the channel.

[0038] For the associated coarse particles, the Newton's third law analysis framework is first established to calculate the interaction force F between the associated coarse particles. p 、F pThe included angle γ with the direction of gravity, and then measure the F of each associated coarse particle IB , and then calculate the fluid momentum M of the debris flow slurry acting on each associated coarse particle according to Equation 5 and Equation 6 respectively f , the resistance moment M of each associated coarse particle to the debris flow slurry 0 . Finally, calculate the starting moment M of each associated coarse particle according to Equation 4, and also determine whether the associated coarse particle is in the critical state of starting with the debris flow slurry according to the critical state identification condition expressed by M

[0039] M f = F ul R sin(β - α) + F ht R cos(β - α) + F P R sinγcos(β - α) Equation 5

[0040] M 0 = GRsin(β - α) + F P R cosγsin(β - α) Equation 6

[0041] In the formula, F p - The interaction force between associated coarse particles, unit N

[0042] γ - The included angle between F p and the direction of gravity, unit °

[0043] The key to measuring the critical state of associated coarse particles is to consider the influence of the interaction force F p generated by the mutual contact between coarse particles on the moment balance of N coarse particles. The above method solves this problem by constructing a Newton's third law analysis framework around N associated coarse particles

[0044] The present invention also provides an application solution of the above-mentioned critical starting identification method for coarse particles in debris flow channels

[0045] The application of the above-mentioned critical starting identification method for coarse particles in debris flow channels is characterized in that: it is applied to the starting monitoring of coarse particles in debris flow channels, or applied to the hazard monitoring and / or assessment of debris flow

[0046] In the above application solution, the application to the starting monitoring of coarse particles in debris flow channels can be a monitoring method or a monitoring system

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Starting from the analysis of the change process from precipitation runoff to debris flow slurry formation in the channel flow area, the present invention discovers that due to the continuous entrainment and incorporation of fine particles, the flow state characteristics of the debris flow slurry undergo an essential change, constituting non-Newtonian characteristics, thereby greatly affecting the role played by the slurry in changing the state of coarse particles. Based on this principle, the method for calculating the hydrodynamic force of coarse particles in the debris flow channel of the present invention constructs a hydrodynamic force calculation model that fully considers the characteristics of the debris flow slurry and its change effects, including flow state characteristics. (2) The method for calculating the hydrodynamic force of coarse particles in the debris flow channel of the present invention uses the comprehensive action force to measure the hydrodynamic force of the debris flow slurry on the initiation of coarse particles. Compared with the prior art's technical idea of decomposing the action of the debris flow slurry on coarse particles into drag forces, lift forces, etc. in multiple directions, the calculation amount is simplified and the operation efficiency is improved. (3) The critical initiation identification method for coarse particles in the debris flow channel of the present invention provides a method that divides the moment balance of the starting force of coarse particles into two types of problems: solitary coarse particles and associated coarse particles based on the distribution characteristics of coarse particles in the channel. The former only considers the moment balance of coarse particles in the hydrodynamic force environment of the slurry, and the latter further considers the moment balance in the environment of mutually contacting coarse particles. Compared with the prior art's treatment method of only constructing the moment balance for solitary coarse particles, new technical problems are solved, which has practical significance for complex channel environments. (4) The critical initiation identification method for coarse particles in the debris flow channel of the present invention combines the two characteristics of the large self-weight of coarse particles and the large looseness of the channel bed deposits, and constructs a moment balance system considering the subsidence depth of coarse particles and the rotation center, which is more in line with the characteristics of the change of the state of coarse particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the meanings of some parameters in Part 1 of the embodiment.

[0049] Figure 2 It is Figure 1 The P-value and U-value curve graphs of point b.

[0050] Figure 3 It is Figure 1 of point b ΔU curve graph.

[0051] Figure 4 It is the F of the coarse particles in Example 1 IB curve graph.

[0052] Figure 5 It is the M curve graph of the coarse particles in Example 1.

[0053] Figure 6 It is a schematic diagram of the meanings of some parameters in Example 2.

[0054] Figure 7 It is Figure 6P-value and U-value curve graphs of point b.

[0055] Figure 8 is Figure 6 of point b ΔU curve graph.

[0056] Figure 9 is the F IB curve graph of the coarse particles in the second embodiment.

[0057] Figure 10 is the M curve graph of the coarse particles in the second embodiment. Detailed implementation manners

[0058] The preferred embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0059] Embodiment 1

[0060] As Figures 1 to 5 shown, the critical incipient motion identification of the coarse particles in a certain debris flow gully is implemented by the method of the present invention.

[0061] 1. Obtain basic data through on-site investigation

[0062] Obtain the topographic map of the debris flow gully (through UAV three-dimensional scanning or satellite photography), and extract the gully characteristic parameters.

[0063] Through on-site observation of the gully and in combination with the historical disaster data, determine the debris flow motion characteristic parameters at the runoff confluence position under rainfall conditions, including the gully flow rate Q at the runoff confluence point of the gully or the debris flow slurry velocity U at the runoff confluence point of the gully 0 .

[0064] Through on-site investigation of the gully, obtain the characteristic parameters of each coarse particle in the gully flow area. Among them, the average density ρ of the coarse particles p is determined through indoor tests after on-site sampling. In this example, the coarse particle object is controlled as large boulders with a radius R≥1m.

[0065] Collect samples of the fine particles of the debris flow in the gully in the field (preferably samples in the accumulation area), configure them into debris flow slurry through indoor experiments, and measure the density ρ of the debris flow slurry f .

[0066] Set up an indoor rheological experiment for the debris flow slurry, use the Herschel-Bulkley model in non-Newtonian fluids to express the rheological properties of the debris flow slurry, substitute the data of the density ρ of the debris flow slurry f , and obtain the rheological parameters of the debris flow slurry, including the yield viscosity μ 0 , consistency coefficient k, flow behavior index n, and yield stress τ 0 .

[0067] Table 1 Basic data table

[0068]

[0069]

[0070] Figure 1 It is a schematic diagram of the meaning of some parameters in the embodiment. In the figure, F f indicates frictional force.

[0071] 2. Measure the debris flow slurry pressure P and flow velocity U at the position of coarse particles

[0072] Construct the fluid motion momentum equation and continuity equation of the debris flow slurry (for the specific construction process, reference can be made to the existing technology: Ferziger, J.H., M., Street, R.L., *Computational Methods for Fluid Dynamics (Fourth Edition)*, Springer, 2020, https: / / doi.org / 10.1007 / 978-3-319-99693-6, page 183), and use the basic data to determine the initial conditions of the equations (α, B, H, L, R, h, (x, y), l, ρ p , ρ f , μ 0 , k, n, τ 0 , U 0 ). Obtain the debris flow slurry pressure P, debris flow slurry velocity U, and debris flow slurry shear rate at the time T when the coarse particles reach the confluence point of the channel runoff along the movement of the debris flow slurry through the output of the equations

[0073] Taking the moving contact point b ( Figure 1 midpoint b) of the coarse particle 1 as an example, Figure 2 is Figure 1 the curve graph of the P value and U value at point b.

[0074] 3. Measure the hydrodynamic force F of the debris flow slurry on the coarse particles IB

[0075] In this embodiment, the F of the solitary coarse particles is measured IB .

[0076] Taking a solitary coarse particle (denoted as coarse particle 1) as an example, its characteristics specifically include: the volume V of the coarse particle = 36.82 m 3 , the radius R of the coarse particle = 2.5 m, and the gravity G of the coarse particle = 103083.51 m / s 2, the subsidence depth h of the coarse particles in the debris flow channel is 1 m, the position (x, y) of the coarse particles in the debris flow channel, and the distance l of the coarse particles from the runoff confluence point is 50 m.

[0077] Substitute each variable into Model Equation 1 to calculate and output the debris flow slurry hydrodynamic force F borne by the coarse particle 1 IB , see Figure 2 . In Model Equation 1, is obtained by performing calculation on P, that is, performing a gradient operation on the surface of the coarse particles. ΔU is obtained by performing a Δ calculation on U, that is, performing a Laplace operation on U on the surface of the coarse particles. The debris flow slurry shear rate is obtained by calculating through the momentum equation and the continuity equation.

[0078] Figure 3 is Figure 1 the ΔU curve graph of point b.

[0079] Figure 4 is the F IB curve graph of the coarse particle 1 in Example 1.

[0080] 3. Measure the M of the solitary coarse particles f , M 0

[0081] Respectively calculate the debris flow slurry hydrodynamic moment M borne by the solitary coarse particles according to Equation 2 and Equation 3 f , and its resistance moment M 0 against the debris flow slurry. The included angle β is calculated according to Equation 7.

[0082] Continuing with the coarse particle 1 as an example, the calculation data is omitted.

[0083] 4. Calculate the starting moment M of the coarse particles

[0084] Calculate the starting moment M of the coarse particles according to Equation 4. Continuing with the coarse particle 1 as an example, the change in the starting moment M is shown in Figure 5 . Figure 5 is the M curve graph of the coarse particle 1 in Example 1.

[0085] In this example, the critical state identification condition of the coarse particles is expressed according to Equation 8.

[0086] M>0 Equation 8

[0087] Thus, it is determined that the coarse particle 1 will start in the channel, and the specific time is 2.43 s after the debris flow slurry reaches the runoff confluence point.

[0088] Based on the above measurement results, the key time nodes of the change in the impact destructiveness of the debris flow during the debris flow process can be judged.

[0089] Example 2

[0090] As Figures 6 to 10 shown, the critical incipient motion identification of coarse particles in a debris flow gully is implemented using the method of the present invention. This example and Example 1 are in the same gully environment, and the same content will not be repeated. The critical incipient motion of the associated coarse particles in the gully is identified in this example.

[0091] Figure 6 is a schematic diagram of the meanings of some parameters in Example 2. In the figure, F f indicates the frictional force.

[0092] 1. Measure the hydrodynamic force F of the debris flow slurry acting on the coarse particles IB

[0093] For the associated coarse particles (N aggregated coarse particles) in the gully, their characteristic parameters are determined respectively.

[0094] Taking a group of associated coarse particles (N = 2) as an example, associated coarse particle 1 (denoted as coarse particle G 1 ) is located at (x 1 , y 1 ) in the debris flow gully, and each characteristic is the same as that of coarse particle 1 in Example 1; the characteristics of associated coarse particle 2 (denoted as coarse particle G 2 ) specifically include: volume V 2 = 36.82 m 3 , radius R 2 = 2.5 m, gravity G 2 = 103083.51 m / s 2 , the subsidence depth h 2 = 1 m in the debris flow gully, the location (x 2 , y 2 ) in the debris flow gully, and the distance l 2 = 45 m from the runoff catchment point.

[0095] Measure the hydrodynamic force F of the debris flow slurry acting on each associated coarse particle using the same method as in Example 1 IB .

[0096] Taking the moving contact point b ( 2 midpoint b) of coarse particle G Figure 6 as an example, Figure 7 is Figure 6 the P - value and U - value curve graph of point b, Figure 8 is Figure 6 the ΔU curve graph of point b.

[0097] Figure 9 is the F IB curve graph of the coarse particles in Example 2.

[0098] 2. Measure the M of associated coarse particles f , M 0

[0099] For any group of associated coarse particles, establish a force balance system among N converging coarse particles according to Newton's third law, and calculate the interaction force F between the associated coarse particles p , and determine F p and the included angle γ with the direction of gravity

[0100] This example belongs to the analysis framework of F with N = 2, and the determination of F p is more intuitive. When N > 2, the determination of F p can adopt the treatment method of force composition to simplify the operation. That is: for any coarse particle in the association, the forces exerted on it from different directions by the remaining N - 1 coarse particles are combined into one F p , and then the included angle γ is determined p

[0101] Calculate the fluid moment M of the debris flow slurry acting on each associated coarse particle respectively according to Equation 5 and Equation 6 f , and its resistance moment M 0 on the debris flow slurry

[0102] Continue to take the coarse particle G 1 , the coarse particle G 2 as an example to calculate and determine F p = 0, γ = 15°, and the calculation data of M f and M 0 are omitted

[0103] 3. Calculate the starting moment M of the associated coarse particles

[0104] Calculate the starting moment M of the coarse particles according to Equation 4 Figure 10 is the M curve graph of the coarse particles in Example 2

[0105] In this example, the critical state identification condition of the coarse particles is expressed according to Equation 8. Thus, the coarse particle G 2 can start in the channel and starts 2.24 s after the debris flow slurry reaches the runoff convergence point, and the coarse particle G 1 starts 2.31 s after the debris flow slurry reaches the runoff convergence point

[0106] According to the above measurement results, the key time nodes of the change in the impact destructiveness of the debris flow during the debris flow process can be judged​

Claims

1. A method for calculating the fluid force of coarse particles in debris flow channels, characterized by: First, conduct a field survey of the channel to obtain basic channel data, including channel characteristic parameters, debris flow movement characteristics under rainfall conditions, coarse particle characteristic parameters, and debris flow slurry characteristic parameters; Secondly, the basic data are used to calculate the debris flow slurry pressure P, debris flow slurry velocity U, and debris flow slurry shear rate at the time T when the coarse particles move along the debris flow slurry to reach the channel runoff confluence point. Finally, the debris flow fluid force F acting on the coarse particles is calculated according to the model. IB , In the formula, F IB —The debris flow slurry fluid force on coarse particles, unit N, - Gradient operator of debris flow slurry pressure P, constructed using slurry pressure P, k - debris flow slurry consistency coefficient, dimensionless, determined according to debris flow slurry characteristics, - Shear rate of debris flow slurry, unit: m / s, n - debris flow slurry fluidity index, dimensionless, determined according to the debris flow slurry characteristics, τ0 - debris flow slurry yield stress, unit Pa, determined according to the debris flow slurry characteristics, ΔU - Laplace operator of debris flow slurry velocity U, constructed using slurry flow velocity U, V - volume of coarse particles, unit: m 3 , characteristic parameters of coarse particles.

2. The method for calculating the fluid force of coarse particles in debris flow channels according to claim 1 is characterized by: Construct the fluid motion momentum equation and continuity equation of debris flow slurry, substitute the initial conditions into the equations, and use the equation output to obtain the pressure P, flow velocity U, and shear rate 3. The method for calculating the fluid force 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 of debris flow slurry fluid motion, the channel flow rate Q or the debris flow slurry velocity U0 is the flow rate or debris flow slurry velocity at the channel runoff confluence position under rainfall conditions.

4. The method for calculating the fluid force of coarse particles in debris flow channels according to claim 1, characterized in that: An indoor rheological experiment of debris flow slurry was set up, and the Herschel-Bulkley model in non-Newtonian fluid was used to simulate and calculate the rheological properties of debris flow slurry, so as to obtain the rheological parameters of debris flow slurry, including the consistency coefficient k, yield stress τ0, and fluidity index n of debris flow slurry.

5. The method for calculating the fluid force of coarse particles in debris flow channels according to claim 4, characterized in that: The debris flow slurry density ρ required in the simulation calculation f The acquisition method is: sampling in the channel accumulation area, configuring the fine particle samples of the debris flow into slurry, and measuring and determining the density of the debris flow slurry ρ f .

6. A method for identifying the critical start of coarse particles in debris flow channels, characterized by: Step S100, investigating the distribution of coarse particles in the debris flow channel to determine the orphaned coarse particles; Step S200, using the method for calculating the fluid force of coarse particles in the debris flow channel according to any one of claims 1 to 5 to calculate the F of the orphaned coarse particles. IB ; Step S300: Calculate the fluid moment M of the debris flow slurry acting on the isolated coarse particles. f , the resistance moment M0 of isolated coarse particles to debris flow slurry, M f =F ul R sin(β-α)+F ht R cos(β-α) Equation 2 M0=GR sin(β-α) Formula 3 In the formula, F ul 、F ht - F IB Components in the horizontal and vertical directions, in N, R - radius of coarse particles, unit: m, determined by the characteristic parameters of coarse particles. α - debris flow channel inclination, unit: °, according to channel characteristic parameters, β - The angle between the coarse particle geometric analysis straight line oa and the ray o, unit: °. The straight line oa is the line connecting the sphere center point o and the rotation center point a. The ray o is the ray passing through the sphere center point o and perpendicular to the groove bed surface. It is determined based on the analysis of the coarse particle characteristic parameters. G - Gravity of coarse particles, determined by the characteristic parameters of coarse particles, unit: m / s 2 ; Step S400, calculating the starting torque M of the orphan coarse particle, and judging whether the orphan coarse particle is in a critical state of starting with the debris flow slurry according to the critical state judgment condition expressed by M, M=M f -M0 type 4.

7. The method for identifying critical start of coarse particles in debris flow channels according to claim 6, characterized in that: The step S100 is to investigate the distribution of coarse particles in the debris flow channel, determine the associated coarse particles, and obtain the interaction force F between the associated coarse particles. p 、F p Angle γ with the direction of gravity; The step S200 is to measure the F of each associated coarse particle. IB ; The step S300 is to calculate the fluid moment M of the debris flow slurry on each associated coarse particle. f , the resistance moment M0 of each associated coarse particle to the debris flow slurry, M f =F ul R sin(β-α)+F ht R cos(β-α)+F P R sinγcos(β-α) Equation 5 M0=GRsin(β-α)+F P R cosγsin(β-α) Equation 6 In the formula, F p - The interaction force between the associated coarse particles, unit N, γ-F p The angle with the direction of gravity, unit: °; In step S400, the starting torque M of the associated coarse particles is calculated according to formula 4, and the critical state identification condition expressed by M is used to determine whether the associated coarse particles are in a critical state of starting with the debris flow slurry.

8. The method for identifying critical start of coarse particles in debris flow channel according to claim 6 or 7, characterized in that: The angle β is calculated according to Formula 7, Where, h is the sinking depth of coarse particles in the debris flow channel, in meters, determined by the characteristic parameters of coarse particles.

9. The method for identifying critical start of coarse particles in debris flow channel according to claim 6 or 7, characterized in that: The critical state identification condition is expressed according to formula 8: M>0 formula 8.

10. Application of the method for identifying critical start of coarse particles in debris flow channels according to claim 6 or 7, 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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