A numerical simulation method for rainfall-induced mountain torrents and debris flows

Abstract

The present invention discloses a method for numerical simulation of flash floods and debris flows induced by rainfall, including: coupling a fluid mechanics model of a three-phase medium of water, coarse particles and fine particles based on a continuum mechanics method to obtain data required by the numerical simulation method. The present application is based on the theory of continuum mechanics, and uses a continuum mechanics method to couple a fluid mechanics model of a three-phase medium of water, coarse particles and fine particles, and uses a finite difference method to implement a method for numerical simulation of flash floods and debris flows that takes rainfall conditions into consideration. The method of the present application can simulate the formation, movement and sediment transport process of flash floods and debris flows under different rainfall conditions. The model of the present invention can realize real-time judgment of whether the fluid formed under certain rainfall conditions is a flash flood or a debris flow, as well as the density of the flash flood and debris flow based on the rainfall process, vegetation distribution and soil grading parameters, and sets corresponding prevention and control measures and management plans based on the calculated results.

Description

Technical Field

[0001] The invention belongs to the technical field of geological disaster prevention and control and hydrogeological simulation, and in particular relates to a numerical simulation method for rainfall-induced mountain torrents and debris flows. Background Art

[0002] Flash floods and debris flows are a serious natural disaster that poses a huge threat to human life, property, and the ecological environment. Accurately simulating the occurrence and development of flash floods and debris flows is of great significance for early warning, disaster prevention and mitigation, and risk management. In recent years, with the in-depth study of the occurrence mechanism of flash floods and debris flows, people have gradually realized that rainfall conditions have an important influence on the occurrence and development of flash floods and debris flows. Factors such as rainfall intensity, rainfall duration, and rainfall distribution will affect the initiation, movement, and deposition of flash floods and debris flows. However, most of the existing numerical simulation methods for flash floods and debris flows do not fully consider the influence of vegetation conditions and sediment transport processes, resulting in a large deviation between the simulation results and the actual situation. Summary of the invention

[0003] The purpose of the present invention is to provide a numerical simulation method for rainfall-induced mountain torrents and debris flows, so as to solve the problem that most of the existing numerical simulation methods for mountain torrents and debris flows do not fully consider the influence of vegetation conditions and sediment transport processes, resulting in a large deviation between the simulation results and the actual situation.

[0004] The embodiment of the present application is implemented as follows: a numerical simulation method for rainfall-induced flash floods and debris flows includes: coupling a fluid mechanics model of a three-phase medium of water, coarse particles and fine particles based on a continuous medium mechanics method to obtain data required for the numerical simulation method, wherein the data includes terrain data, time series data of rainfall, vegetation distribution data, and at least one of the volume contents of initial coarse particles and fine particles in the gully bed.

[0005] In some embodiments, the governing equation of the fluid mechanics model is:

[0006] ;

[0007] ;

[0008] ;

[0009] In the formula, Depth of mountain torrents and debris flows, unit: ;

[0010] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0011] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0012] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0013] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0014] is the density of mountain torrents and debris flows, unit: ;

[0015] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0016] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0017] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0018] is the density of particulate matter in mountain torrents and debris flows, unit: ;

[0019] is the density of clean water, unit: ;

[0020] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0021] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0022] The elevation of the terrain required for numerical simulation, unit: ;

[0023] , is the acceleration due to gravity, unit: ;

[0024] Represents effective rainfall intensity, unit: ;

[0025] is the soil permeability, unit: ;

[0026] is the total erosion rate of mountain torrents and debris flows, unit: ;

[0027] It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0028] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0029] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0030] is the total deposition rate of particulate matter in mountain torrents and debris flows, unit: ;

[0031] is the deposition rate of fine particles in mountain torrents and debris flows, unit: ;

[0032] is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ;

[0033] is time, unit: .

[0034] In some embodiments, the transport equations for water, fine particles, and coarse particles in a flash flood and debris flow are:

[0035] ;

[0036] ;

[0037] ;

[0038] In the formula, Depth of mountain torrents and debris flows, unit: ;

[0039] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0040] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0041] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0042] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0043] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0044] Represents effective rainfall intensity, unit: ;

[0045] is the soil permeability, unit: ;

[0046] It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0047] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0048] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0049] is the deposition rate of fine particles in mountain torrents and debris flows, unit: ;

[0050] is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ;

[0051] is the diffusion coefficient of fine particles in mountain torrents and debris flows, unit: ;

[0052] is time, unit: ; and / or

[0053] The evolution equation of the terrain is:

[0054] ;

[0055] In the formula, is the trench bed porosity, unit: dimensionless;

[0056] is the elevation of the terrain, in units: ;

[0057] is the total erosion rate of mountain torrents and debris flows, unit: ;

[0058] It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0059] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0060] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0061] is the total deposition rate of particulate matter in mountain torrents and debris flows, unit: ;

[0062] is the deposition rate of fine particles in mountain torrents and debris flows, unit: ;

[0063] is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ;

[0064] is the sediment transport rate per unit width along the x direction, unit: ;

[0065] is the sediment transport rate per unit width along the y direction, unit: ;

[0066] is time, unit: .

[0067] In some embodiments, in the control equation, the effective rainfall intensity The calculation formula is:

[0068] ;

[0069] In the formula, Represents effective rainfall intensity, unit: ;

[0070] is the actual rainfall intensity, in units: ;

[0071] is the vegetation coverage, unit: dimensionless;

[0072] is the vegetation penetration coefficient, unit: dimensionless;

[0073] is the crown drainage rate, in: ;

[0074] Crown drainage rate The calculation formula is:

[0075] ;

[0076] In the formula, is the crown drainage rate, in: ;

[0077] is the attenuation coefficient of the crown drainage rate, unit: ;

[0078] is the total water storage capacity of the tree crown, unit: ;

[0079] for The crown water storage at the moment, unit: ;

[0080] It is the drainage coefficient when the crown water storage reaches the total water storage capacity, unit: ;

[0081] exist Crown water storage at any time The calculation equation is:

[0082] ;

[0083] In the formula, for The crown water storage at the moment, unit: ;

[0084] is the vegetation penetration coefficient, unit: dimensionless;

[0085] is the actual rainfall intensity, in units: ;

[0086] is the vegetation coverage, unit: dimensionless;

[0087] is the crown drainage rate, in: ;

[0088] is time, unit: ; and / or

[0089] In the control equation, soil permeability The calculation formula is:

[0090] ;

[0091] In the formula, is the soil permeability, unit: ;

[0092] is the stable permeability of the soil, unit: ;

[0093] is the initial permeability of the soil, unit: ;

[0094] is a constant describing the attenuation of rainfall infiltration over time, unit: ;

[0095] is time, unit: ; and / or

[0096] In the control equation, the total erosion rate of mountain torrents and debris flows is The calculation method is:

[0097] ;

[0098] In the formula, is the total erosion rate of mountain torrents and debris flows, unit: ;

[0099] is the total sediment splashing rate of gully bed material caused by rainfall, unit: ;

[0100] is the total erosion rate of mountain torrents on ditch bed sediment, unit: ;

[0101] is the total debris flow erosion rate, unit: ;

[0102] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0103] The calculation formula of Γ is:

[0104] ;

[0105] Where α is the attenuation exponent, unit: dimensionless, value is 13.8;

[0106] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0107] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0108] It is the critical total particulate matter concentration that separates mountain torrents from debris flows. Unit: dimensionless, with a value of 0.18.

[0109] In some embodiments, Total sediment splashing rate of gully bed materials caused by moderate rainfall Including the original soil sediment splash rate and splash erosion rate of mountain torrent sediment Two parts, namely

[0110] ;

[0111] ;

[0112] ;

[0113] In the formula, is the sediment splash rate caused by rainfall, unit: ;

[0114] is the total splash erosion rate of original soil sediment caused by rainfall, unit: ;

[0115] is the total sediment splashing rate of mountain torrent sediment caused by rainfall, unit: ;

[0116] Represents the effective rainfall intensity, unit: ;

[0117] It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless;

[0118] It is the total sediment mass of mountain torrents per unit area, unit: ;

[0119] It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ;

[0120] It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ;

[0121] It is the mass of sediment required to protect the original soil from further erosion per unit area, in units of: ;

[0122] is the stripping coefficient of the original soil under the impact of raindrops, unit: dimensionless;

[0123] It is the stripping coefficient of sediment under the impact of raindrops, unit: dimensionless.

[0124] In some embodiments, the degree to which the sediment cover protects the riverbed from erosion is calculated The mass of fine-grained sediment per unit area of ​​the mountain torrent used and the mass of coarse sediment per unit area of ​​mountain torrents The calculation equations are:

[0125] ;

[0126] ;

[0127] In the formula, It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ;

[0128] It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ;

[0129] is the density of the sediment, in units of: ;

[0130] is the trench bed porosity, unit: dimensionless;

[0131] is the fine-grained sediment deposition rate, unit: ;

[0132] is the splashing rate of fine-grained sediment in mountain torrent sediment by rainfall, unit: ;

[0133] is the erosion rate of fine-grained sediment in mountain torrent sediment by mountain torrents, unit: ;

[0134] is the fine-grained sediment deposition rate, unit: ;

[0135] is the splashing rate of coarse sediment in sediment sediments by rainfall, unit: ;

[0136] is the erosion rate of coarse sediment in sediment by mountain torrents, unit: ;

[0137] is the total erosion rate of mountain torrents on ditch bed sediment, unit: ;

[0138] is the sediment transport rate of coarse particles per width along the x direction, unit: ;

[0139] is the sediment transport rate of coarse particles per width along the y direction, unit: ; and / or

[0140] Calculate the extent to which a sediment cover protects a riverbed from erosion The stripping coefficient of the original soil under the raindrop impact used The stripping coefficient of sediment under raindrop impact The calculation method is:

[0141] ;

[0142] ;

[0143] In the formula, is the stripping coefficient of the original soil under the impact of raindrops, unit: dimensionless;

[0144] is the stripping coefficient of the original soil under the impact of raindrops when there is no influence of mountain torrent runoff, unit: dimensionless;

[0145] is the stripping coefficient of sediment under raindrop impact, unit: dimensionless;

[0146] is the stripping coefficient of sediment under the impact of raindrops when there is no mountain torrent runoff, unit: dimensionless;

[0147] is the critical flash flood depth at which rainfall can directly strip away sediment particles, unit: ;

[0148] is the average diameter of rainfall drops, unit: ;

[0149] is the depth of flash flood perpendicular to the channel direction, unit: ;

[0150] is the calculated flash flood depth, unit: ;

[0151] is the channel slope, calculated from the topography, unit: °;

[0152] It is the attenuation index of the effect of flash flood depth on the rainfall drop stripping coefficient.

[0153] In some embodiments, Total erosion rate of gully bed materials by medium mountain torrents Including the erosion rate of original soil and sediment by mountain torrents and mountain torrent erosion rate of mountain torrent sediment Two parts, namely

[0154] ;

[0155] ;

[0156] ;

[0157] In the formula, is the total erosion rate of mountain torrents on gully bed materials, unit: ;

[0158] is the erosion rate of mountain torrents on the original soil sediment, unit: ;

[0159] is the erosion rate of mountain torrents on mountain torrent sediment, unit: ;

[0160] It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless;

[0161] is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ;

[0162] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0163] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0164] It is the anti-erosion capacity of the ditch bed material when mountain torrents erode the original soil, unit: ;

[0165] It is the erosion resistance of the gully bed material when the mountain torrent erodes the mountain torrent sediment, unit: ;

[0166] It is the empirical coefficient of mountain torrent erosion of original soil, unit: ;

[0167] It is the empirical coefficient of mountain torrent erosion of mountain torrent sediments, unit: ; and / or

[0168] Debris flow erosion rate Including the erosion rate of original soil and sand by debris flow The erosion rate of mountain torrent sediment and debris flow Two parts, the calculation equation is:

[0169] ;

[0170] ;

[0171] ;

[0172] In the formula, is the debris flow erosion rate, unit: ;

[0173] is the erosion rate of the original soil and sand by debris flow, unit: ;

[0174] is the erosion rate of debris flow on mountain torrent sediment, unit: ;

[0175] It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless;

[0176] is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ;

[0177] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0178] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0179] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0180] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0181] is the density of mountain torrents and debris flows, unit: ;

[0182] The calculated depth of mountain torrents and debris flows, unit: ;

[0183] It is the pore water pressure coefficient in the ditch bed material when debris flow erodes the ditch, unit: dimensionless;

[0184] is the channel slope, calculated from the topography, unit: °;

[0185] It is the friction angle of the original soil particles when the debris flow erodes the original soil in the channel, unit: °;

[0186] It is the cohesion of the original soil particles in the original soil when the debris flow erodes the original soil in the gully, unit: ;

[0187] It is the friction angle of flood-deposited granular material when debris flow erodes flood sediments in the channel, unit: °;

[0188] It is the cohesion of flood sediments when debris flow erodes flood sediments in the channel, unit: ;

[0189] is the acceleration due to gravity, unit: .

[0190] In some embodiments, in the transport equation, the erosion rate of water in the gully bed by the flash flood and debris flow is , erosion rate of coarse particles and erosion rate of fine particulate matter , are calculated by the following formulas:

[0191] ;

[0192] ;

[0193] ;

[0194] In the formula, It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0195] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0196] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0197] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0198] It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ;

[0199] It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ;

[0200] is the volume fraction of water in the original soil in the channel, unit: dimensionless;

[0201] is the volume fraction of coarse-grained material in the original soil in the channel, unit: dimensionless;

[0202] is the volume fraction of fine particulate matter in the original soil in the channel, unit: dimensionless;

[0203] is the total splash erosion rate of original soil sediment caused by rainfall, unit: ;

[0204] is the total sediment splashing rate of mountain torrent sediment caused by rainfall, unit: ;

[0205] is the erosion rate of mountain torrents on the original soil sediment, unit: ;

[0206] is the erosion rate of mountain torrents on mountain torrent sediment, unit: ;

[0207] is the erosion rate of the original soil and sand by debris flow, unit: ;

[0208] is the erosion rate of debris flow on mountain torrent sediment, unit: ;

[0209] is the trench bed porosity, unit: dimensionless; and / or

[0210] Diffusion coefficient of fine particle matter in the fine particle transport equation The calculation formula is as follows:

[0211] ;

[0212] In the formula, is the diffusion coefficient of fine particles in mountain torrents and debris flows, unit: ;

[0213] κ = 0.4 represents the von Karman constant, unit: dimensionless;

[0214] is the friction velocity of the bed surface of the mountain torrent and debris flow, unit: ;

[0215] is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ;

[0216] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0217] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0218] is the density of mountain torrents and debris flows, unit: ;

[0219] his the depth of mountain torrents and debris flows, unit: ; and / or

[0220] In the transport equations for fine and coarse particles, the deposition rates of fine and coarse sediment in flash flood runoff are calculated as follows:

[0221] ;

[0222] ;

[0223] In the formula, is the deposition rate of fine particles in flash floods, unit: ;

[0224] is the deposition rate of coarse particles in flash floods, unit: ;

[0225] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0226] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0227] It is an empirical parameter, with a value of 2.0~5.0, unit: dimensionless;

[0228] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0229] is the sedimentation rate of fine particles in mountain torrents, unit: , the calculation formula is:

[0230] ;

[0231] In the formula, is the kinematic viscosity of clean water, unit: ;

[0232] It is the representative particle size of fine particles in the process of mountain torrent movement, unit: ;

[0233] is the density of fine particles in mountain torrents and debris flows, unit: ;

[0234] is the density of clean water, unit: ;

[0235] is the acceleration due to gravity, unit: ;

[0236] is the sedimentation rate of coarse particles in mountain torrents, unit: , the calculation formula is:

[0237] ;

[0238] In the formula, is the kinematic viscosity of clean water, unit: ;

[0239] It is the representative particle size of coarse particles in the process of mountain torrent movement, unit: ;

[0240] is the density of coarse particles in mountain torrents and debris flows, unit: ;

[0241] is the density of clean water, unit: ;

[0242] is the acceleration due to gravity, unit: .

[0243] In some embodiments, the formula and The sediment transport rate of coarse particles per width along the x direction is and the sediment transport rate of coarse particles per width along the y direction The calculation methods are:

[0244] ;

[0245] ;

[0246] In the formula, is the sediment transport rate of coarse particles per width along the x direction, unit: ;

[0247] is the sediment transport rate of coarse particles per width along the y direction, unit: ;

[0248] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0249] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0250] Coarse particle single width sediment transport rate, unit: , the calculation formula is:

[0251] ;

[0252] In the formula, is the Froude number of the fluid, unit: dimensionless;

[0253] Depth of mountain torrents and debris flows, unit: ;

[0254] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0255] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0256] is the Shields number, unit: dimensionless;

[0257] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0258] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0259] is the density of coarse particles in mountain torrents and debris flows, unit: ;

[0260] is the density of clean water, unit: ;

[0261] It is the representative particle size of coarse particles in the process of mountain torrent movement, unit: ;

[0262] is the acceleration due to gravity, unit: ;

[0263] is the critical Shields number, unit: dimensionless, calculated as:

[0264] ;

[0265] In the formula, is the empirical coefficient, unit: dimensionless;

[0266] is the channel slope, calculated from the topography, unit: °;

[0267] It is the friction angle of the granular material in the channel when the debris flow erodes the channel, unit: °.

[0268] In some embodiments, flash floods and mudslides Directional bottom resistance and mountain torrents and mudslides Directional bottom resistance The calculation formula is as follows:

[0269] ;

[0270] ;

[0271] In the formula, is the density of mountain torrents and debris flows, unit: ;

[0272] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0273] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0274] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0275] is the density of particulate matter in mountain torrents and debris flows, unit: ;

[0276] is the density of clean water, unit: ;

[0277] is the roughness coefficient during the movement of mountain torrents, unit: ;

[0278] Depth of mountain torrents and debris flows, unit: ;

[0279] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0280] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0281] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0282] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0283] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0284] and The liquid phase slurry of mountain torrent debris flow is Direction and Directional bed resistance, unit: ;

[0285] and They are respectively coarse particles of mountain torrents and debris flows along the Direction and Directional bed resistance, unit: ;

[0286] is the acceleration due to gravity (unit: );

[0287] Liquid slurry of mountain torrents and debris flows Directional bottom resistance and Directional bottom resistance The calculation formulas are:

[0288] ;

[0289] ;

[0290] In the formula, Depth of mountain torrents and debris flows, unit: ;

[0291] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0292] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0293] is the dynamic viscosity of clean water, unit: Pa·s;

[0294] Represents the volume concentration of fine particles in liquid mud, unit: dimensionless;

[0295] It is the maximum allowable volume concentration of fine-grained sediment in liquid mud, unit: dimensionless, calculated as:

[0296] ;

[0297] In the formula, d i Represents the fine-grained sediment i The diameter of a particle size class, unit: dimensionless;

[0298] p i Represents the fine-grained sediment i The mass percentage of each particle size grade, unit: dimensionless;

[0299] S v0 It is the critical volume concentration at which the fluid changes from a Newtonian fluid to a Bingham fluid. Unit: dimensionless. The calculation formula is:

[0300] ;

[0301] k 0 is a correction factor, unit: dimensionless, expressed as:

[0302] ;

[0303] Coarse particles of mountain torrents and debris flows Directional bottom resistance and Directional bottom resistance The calculation formulas are:

[0304] ;

[0305] ;

[0306] In the formula, The coarse particles in the mountain torrents and debris flows The resistance to motion in the direction, in units: ;

[0307] The coarse particles in the mountain torrents and debris flows The resistance to motion in the direction, in units: ;

[0308] is the density of mountain torrents and debris flows, unit: ;

[0309] It is the density of liquid slurry composed of fine particles and water, unit: ;

[0310] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0311] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0312] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0313] is the density of particulate matter in mountain torrents and debris flows, unit: ;

[0314] is the density of clean water, unit: ;

[0315] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0316] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0317] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0318] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0319] Depth of mountain torrents and debris flows, unit: ;

[0320] The bottom edge of the mountain torrent debris flow Slope in the direction, calculated from the terrain. Unit: °;

[0321] The bottom edge of the debris flow Slope in the direction, calculated from the terrain. Unit: °;

[0322] is the friction angle between coarse particles and the bottom bed in mountain torrents and debris flows, unit: °;

[0323] is the turbulence coefficient of coarse particles in mountain torrents and debris flows, unit: ;

[0324] , is the acceleration due to gravity, unit: .

[0325] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0326] This application is based on the theory of continuum mechanics. It couples the fluid mechanics model of water, coarse particles and fine particles through the continuum mechanics method, and uses the finite difference method to realize the numerical simulation method of flash floods and debris flows considering rainfall conditions. The method of this application can simulate the formation, movement and sediment transport process of flash floods and debris flows under different rainfall conditions. The present invention explores how vegetation conditions, fine-grained sand and coarse particle transport affect the formation-movement process of flash floods and debris flows caused by runoff by establishing a quantitative analysis model. The model realizes real-time judgment of whether the fluid formed under certain rainfall conditions is a flash flood or a debris flow, as well as the density of the flash flood and debris flow based on the rainfall process, vegetation distribution and soil grading parameters, and sets corresponding prevention and control measures and management plans based on the calculated results. BRIEF DESCRIPTION OF THE DRAWINGS

[0327] Figure 1 It is the particle gradation curve of the debris flow of the present invention.

[0328] Figure 2 This is the simulation result of the formation and movement of a mountain torrent and debris flow in a ditch in Sichuan under rainfall conditions in the present invention. DETAILED DESCRIPTION

[0329] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. 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.

[0330] The technical solution of this application is as follows:

[0331] An embodiment of the present application provides a numerical simulation method for rainfall-induced flash floods and debris flows, including: coupling a fluid mechanics model of a three-phase medium of water, coarse particles and fine particles based on a continuum mechanics method to obtain data required for the numerical simulation method, wherein the data include terrain data, rainfall time series data, vegetation distribution data, and at least one of the volume contents of initial coarse particles and fine particles in the gully bed.

[0332] This application is based on the theory of continuum mechanics. It couples the fluid mechanics model of water, coarse particles and fine particles through the continuum mechanics method, and uses the finite difference method to realize the numerical simulation method of flash floods and debris flows considering rainfall conditions. The method of this application can simulate the formation, movement and sediment transport process of flash floods and debris flows under different rainfall conditions. The present invention explores how vegetation conditions, fine-grained sand and coarse particle transport affect the formation-movement process of flash floods and debris flows caused by runoff by establishing a quantitative analysis model. The model realizes real-time judgment of whether the fluid formed under certain rainfall conditions is a flash flood or a debris flow, as well as the density of the flash flood and debris flow based on the rainfall process, vegetation distribution and soil grading parameters, and sets corresponding prevention and control measures and management plans based on the calculated results.

[0333] In some embodiments, the governing equation of the fluid mechanics model is:

[0334] ;

[0335] ;

[0336] ;

[0337] In the formula, Depth of mountain torrents and debris flows, unit: ;

[0338] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0339] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0340] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0341] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0342] is the density of mountain torrents and debris flows, unit: ;

[0343] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0344] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0345] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0346] is the density of particulate matter in mountain torrents and debris flows, unit: ;

[0347] is the density of clean water, unit: ;

[0348] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0349] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0350] The elevation of the terrain required for numerical simulation, unit: ;

[0351] , is the acceleration due to gravity, unit: ;

[0352] Represents effective rainfall intensity, unit: ;

[0353] is the soil permeability, unit: ;

[0354] is the total erosion rate of mountain torrents and debris flows, unit: ;

[0355] It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0356] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0357] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0358] is the total deposition rate of particulate matter in mountain torrents and debris flows, unit: ;

[0359] is the deposition rate of fine particles in mountain torrents and debris flows, unit: ;

[0360] is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ;

[0361] is time, unit: .

[0362] In some embodiments, the transport equations for water, fine particles, and coarse particles in a flash flood and debris flow are:

[0363] ;

[0364] ;

[0365] ;

[0366] In the formula, Depth of mountain torrents and debris flows, unit: ;

[0367] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0368] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0369] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0370] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0371] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0372] Represents effective rainfall intensity, unit: ;

[0373] is the soil permeability, unit: ;

[0374] It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0375] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0376] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0377] is the deposition rate of fine particles in mountain torrents and debris flows, unit: ;

[0378] is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ;

[0379] is the diffusion coefficient of fine particles in mountain torrents and debris flows, unit: ;

[0380] is time, unit: .

[0381] In some embodiments, the evolution equation of the terrain is:

[0382] ;

[0383] In the formula, is the trench bed porosity, unit: dimensionless;

[0384] is the elevation of the terrain, in units: ;

[0385] is the total erosion rate of mountain torrents and debris flows, unit: ;

[0386] It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0387] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0388] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0389] is the total deposition rate of particulate matter in mountain torrents and debris flows, unit: ;

[0390] is the deposition rate of fine particles in mountain torrents and debris flows, unit: ;

[0391] is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ;

[0392] is the sediment transport rate per unit width along the x direction, unit: ;

[0393] is the sediment transport rate per unit width along the y direction, unit: ;

[0394] is time, unit: .

[0395] Furthermore, in the control equation, the effective rainfall intensity The calculation formula is:

[0396] ;

[0397] In the formula, Represents effective rainfall intensity, unit: ;

[0398] is the actual rainfall intensity, in units: ;

[0399] is the vegetation coverage, unit: dimensionless;

[0400] is the vegetation penetration coefficient, unit: dimensionless;

[0401] is the crown drainage rate, in: .

[0402] Furthermore, the crown drainage rate The calculation formula is:

[0403] ;

[0404] In the formula, is the crown drainage rate, in: ;

[0405] is the attenuation coefficient of the crown drainage rate, unit: ;

[0406] is the total water storage capacity of the tree crown, unit: ;

[0407] for The crown water storage at the moment, unit: ;

[0408] It is the drainage coefficient when the crown water storage reaches the total water storage capacity, unit: .

[0409] Furthermore, in Crown water storage at any time The calculation equation is:

[0410] ;

[0411] In the formula, for The crown water storage at the moment, unit: ;

[0412] is the vegetation penetration coefficient, unit: dimensionless;

[0413] is the actual rainfall intensity, in units: ;

[0414] is the vegetation coverage, unit: dimensionless;

[0415] is the crown drainage rate, in: ;

[0416] is time, unit: .

[0417] Furthermore, in the control equation, soil permeability The calculation formula is:

[0418] ;

[0419] In the formula, is the soil permeability, unit: ;

[0420] is the stable permeability of the soil, unit: ;

[0421] is the initial permeability of the soil, unit: ;

[0422] is a constant describing the attenuation of rainfall infiltration over time, unit: ;

[0423] is time, unit: .

[0424] Furthermore, in the control equation, the total erosion rate of mountain torrents and debris flows is The calculation method is:

[0425] ;

[0426] In the formula, is the total erosion rate of mountain torrents and debris flows, unit: ;

[0427] is the total sediment splashing rate of gully bed material caused by rainfall, unit: ;

[0428] is the total erosion rate of mountain torrents on ditch bed sediment, unit: ;

[0429] is the total debris flow erosion rate, unit: ;

[0430] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0431] The calculation formula of Γ is:

[0432] ;

[0433] Where α is the attenuation exponent, unit: dimensionless, value is 13.8;

[0434] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0435] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0436] It is the critical total particulate matter concentration that separates mountain torrents from debris flows. Unit: dimensionless, with a value of 0.18.

[0437] It can be understood that Γ is the transition factor from flash floods to debris flows, unit: dimensionless, representing the critical volume concentration of total sediment material that distinguishes flash floods from debris flows.

[0438] It can be understood that the ditch bed material contains two parts: original soil sediment and mountain torrent sediment. Total sediment splashing rate of gully bed materials caused by moderate rainfall Including the original soil sediment splash rate and splash erosion rate of mountain torrent sediment Two parts.

[0439] Further, Total sediment splashing rate of gully bed materials caused by moderate rainfall Including the original soil sediment splash rate and splash erosion rate of mountain torrent sediment Two parts, namely

[0440] ;

[0441] ;

[0442] ;

[0443] In the formula, is the sediment splash rate caused by rainfall, unit: ;

[0444] is the total splash erosion rate of original soil sediment caused by rainfall, unit: ;

[0445] is the total sediment splashing rate of mountain torrent sediment caused by rainfall, unit: ;

[0446] Represents the effective rainfall intensity, unit: ;

[0447] It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless;

[0448] It is the total sediment mass of mountain torrents per unit area, unit: ;

[0449] It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ;

[0450] It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ;

[0451] It is the mass of sediment required to protect the original soil from further erosion per unit area, in units of: ;

[0452] is the stripping coefficient of the original soil under the impact of raindrops, unit: dimensionless;

[0453] It is the stripping coefficient of sediment under the impact of raindrops, unit: dimensionless.

[0454] Furthermore, the extent to which the sediment cover protects the riverbed from erosion is calculated. The mass of fine-grained sediment per unit area of ​​the mountain torrent used and the mass of coarse sediment per unit area of ​​mountain torrents The calculation equations are:

[0455] ;

[0456] ;

[0457] In the formula, It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ;

[0458] It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ;

[0459] is the density of sediment, in units of: ;

[0460] is the trench bed porosity, unit: dimensionless;

[0461] is the fine-grained sediment deposition rate, unit: ;

[0462] is the splashing rate of rainfall on fine-grained sediment in mountain torrent sediment, unit: ;

[0463] is the erosion rate of fine-grained sediment in mountain torrent sediment by mountain torrents, unit: ;

[0464] is the fine-grained sediment deposition rate, unit: ;

[0465] is the splashing rate of coarse sediment in sediment sediments by rainfall, unit: ;

[0466] is the erosion rate of coarse sediment in sediment by mountain torrents, unit: ;

[0467] is the total erosion rate of mountain torrents on ditch bed sediment, unit: ;

[0468] is the sediment transport rate of coarse particles per width along the x direction, unit: ;

[0469] is the sediment transport rate of coarse particles per width along the y direction, unit: .

[0470] Understandably, is the splashing rate of fine-grained sediment in mountain torrent sediment by rainfall, unit: , it is assumed here that rainfall only causes splash erosion on the gully bed material.

[0471] Furthermore, the extent to which the sediment cover protects the riverbed from erosion is calculated. The stripping coefficient of the original soil under the raindrop impact used The stripping coefficient of sediment under raindrop impact The calculation method is:

[0472] ;

[0473] ;

[0474] In the formula, is the stripping coefficient of the original soil under the impact of raindrops, unit: dimensionless;

[0475] is the stripping coefficient of the original soil under the impact of raindrops when there is no influence of mountain torrent runoff, unit: dimensionless;

[0476] is the stripping coefficient of sediment under raindrop impact, unit: dimensionless;

[0477] is the stripping coefficient of sediment under the impact of raindrops when there is no mountain torrent runoff, unit: dimensionless;

[0478] is the critical flash flood depth at which rainfall can directly strip away sediment particles, unit: ;

[0479] is the average diameter of rainfall drops, unit: ;

[0480] is the depth of flash flood perpendicular to the channel direction, unit: ;

[0481] is the calculated flash flood depth, unit: ;

[0482] is the channel slope, calculated from the topography, unit: °;

[0483] It is the attenuation index of the effect of flash flood depth on the rainfall drop stripping coefficient.

[0484] It can be understood that the ditch bed material contains two parts: original soil sediment and mountain torrent sediment. Total erosion rate of gully bed materials by medium mountain torrents (unit: ) includes the erosion rate of original soil and sediment by mountain torrents (unit: ) and mountain torrent erosion rate of mountain torrent sediment (unit: ) two parts.

[0485] Furthermore, Total erosion rate of gully bed materials by medium mountain torrents Including the erosion rate of original soil and sediment by mountain torrents and mountain torrent erosion rate of mountain torrent sediment Two parts, namely

[0486] ;

[0487] ;

[0488] ;

[0489] In the formula, is the total erosion rate of mountain torrents on gully bed materials, unit: ;

[0490] is the erosion rate of mountain torrents on the original soil sediment, unit: ;

[0491] is the erosion rate of mountain torrents on mountain torrent sediment, unit: ;

[0492] It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless;

[0493] is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ;

[0494] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0495] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0496] It is the anti-erosion capacity of the ditch bed material when mountain torrents erode the original soil, unit: ;

[0497] It is the erosion resistance of the gully bed material when the mountain torrent erodes the mountain torrent sediment, unit: ;

[0498] It is the empirical coefficient of mountain torrent erosion of original soil, unit: ;

[0499] It is the empirical coefficient of mountain torrent erosion of mountain torrent sediments, unit: .

[0500] Understandably, for and The maximum value of two numbers.

[0501] Furthermore, Debris flow erosion rate Including the erosion rate of original soil and sand by debris flow The erosion rate of mountain torrent sediment and debris flow Two parts, the calculation equation is:

[0502]

[0503] ;

[0504] ;

[0505] In the formula, is the debris flow erosion rate, unit: ;

[0506] is the erosion rate of the original soil and sand by debris flow, unit: ;

[0507] is the erosion rate of debris flow on mountain torrent sediment, unit: ;

[0508] It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless;

[0509] is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ;

[0510] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0511] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0512] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0513] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0514] is the density of mountain torrents and debris flows, unit: ;

[0515] The calculated depth of mountain torrents and debris flows, unit: ;

[0516] It is the pore water pressure coefficient in the ditch bed material when debris flow erodes the ditch, unit: dimensionless;

[0517] is the channel slope, calculated from the topography, unit: °;

[0518] It is the friction angle of the original soil particles when the debris flow erodes the original soil in the channel, unit: °;

[0519] It is the cohesion of the original soil particles in the original soil when the debris flow erodes the original soil in the gully, unit: ;

[0520] It is the friction angle of flood-deposited granular material when debris flow erodes flood sediments in the channel, unit: °;

[0521] It is the cohesion of flood sediments when debris flow erodes flood sediments in the channel, unit: ;

[0522] is the acceleration due to gravity, unit: .

[0523] Furthermore, in the transport equation, the erosion rate of water in the gully bed by mountain torrents and debris flows is , erosion rate of coarse particles and erosion rate of fine particulate matter , are calculated by the following formulas:

[0524] ;

[0525] ;

[0526] ;

[0527] In the formula, It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ;

[0528] is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ;

[0529] is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ;

[0530] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0531] It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ;

[0532] It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ;

[0533] is the volume fraction of water in the original soil in the channel, unit: dimensionless;

[0534] is the volume fraction of coarse-grained material in the original soil in the channel, unit: dimensionless;

[0535] is the volume fraction of fine particulate matter in the original soil in the channel, unit: dimensionless;

[0536] is the total splash erosion rate of original soil sediment caused by rainfall, unit: ;

[0537] is the total sediment splashing rate of mountain torrent sediment caused by rainfall, unit: ;

[0538] is the erosion rate of mountain torrents on the original soil sediment, unit: ;

[0539] is the erosion rate of mountain torrents on mountain torrent sediment, unit: ;

[0540] is the erosion rate of the original soil and sand by debris flow, unit: ;

[0541] is the erosion rate of debris flow on mountain torrent sediment, unit: ;

[0542] is the porosity of the trench bed, unit: dimensionless.

[0543] It can be understood that Γ is the transition factor from mountain torrents to debris flows, unit: dimensionless; it represents the critical factor of the total sediment material that distinguishes mountain torrents from debris flows.

[0544] Furthermore, the diffusion coefficient of fine particle matter in the fine particle transport equation is The calculation formula is as follows:

[0545] ;

[0546] In the formula, is the diffusion coefficient of fine particles in mountain torrents and debris flows, unit: ;

[0547] κ = 0.4 represents the von Karman constant, unit: dimensionless;

[0548] is the friction velocity of the bed surface of the mountain torrent and debris flow, unit: ;

[0549] is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ;

[0550] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0551] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0552] is the density of mountain torrents and debris flows, unit: ;

[0553] h is the depth of mountain torrents and debris flows, unit: ;

[0554] It can be understood that since the sediment particles are fully mixed and have strong integrity during the movement of debris flow, the sediment particles are negligible, and only the sedimentation of fine and coarse sediment particles during the movement of mountain torrents is considered. Therefore, the calculation method of the deposition rate of fine and coarse sediment particles in the mountain torrent runoff in the transport equation of fine and coarse particles is as follows:

[0555] Furthermore, in the transport equations of fine and coarse particles, the deposition rates of fine and coarse sediment in flash flood runoff are calculated as follows:

[0556] ;

[0557] ;

[0558] In the formula, is the deposition rate of fine particles in flash floods, unit: ;

[0559] is the deposition rate of coarse particles in flash floods, unit: ;

[0560] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0561] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0562] It is an empirical parameter, with a value of 2.0~5.0, unit: dimensionless;

[0563] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0564] is the sedimentation rate of fine particles in mountain torrents, unit: , the calculation formula is:

[0565] ;

[0566] In the formula, is the kinematic viscosity of clean water, unit: ;

[0567] It is the representative particle size of fine particles in the process of mountain torrent movement, unit: ;

[0568] is the density of fine particles in mountain torrents and debris flows, unit: ;

[0569] is the density of clean water, unit: ;

[0570] is the acceleration due to gravity, unit: ;

[0571] is the sedimentation rate of coarse particles in mountain torrents, unit: , the calculation formula is:

[0572] ;

[0573] In the formula, is the kinematic viscosity of clean water, unit: ;

[0574] It is the representative particle size of coarse particles in the process of mountain torrent movement, unit: ;

[0575] is the density of coarse particles in mountain torrents and debris flows, unit: ;

[0576] is the density of clean water, unit: ;

[0577] is the acceleration due to gravity, unit: .

[0578] Furthermore, the formula and The sediment transport rate of coarse particles per width along the x direction is and the sediment transport rate of coarse particles per width along the y direction The calculation methods are:

[0579] ;

[0580] ;

[0581] In the formula, is the sediment transport rate of coarse particles per width along the x direction, unit: ;

[0582] is the sediment transport rate of coarse particles per width along the y direction, unit: ;

[0583] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0584] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0585] Coarse particle single width sediment transport rate, unit: , the calculation formula is:

[0586] ;

[0587] In the formula, is the Froude number of the fluid, unit: dimensionless;

[0588] Depth of mountain torrents and debris flows, unit: ;

[0589] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0590] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0591] is the Shields number, unit: dimensionless;

[0592] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0593] For mountain torrents and mud-rock flows Directional bed resistance, unit: ;

[0594] is the density of coarse particles in mountain torrents and debris flows, unit: ;

[0595] is the density of clean water, unit: ;

[0596] It is the representative particle size of coarse particles in the process of mountain torrent movement, unit: ;

[0597] is the acceleration due to gravity, unit: ;

[0598] is the critical Shields number, unit: dimensionless, calculated as:

[0599]

[0600] In the formula, is the empirical coefficient, unit: dimensionless;

[0601] is the channel slope, calculated from the topography, unit: °;

[0602] It is the friction angle of the granular material in the channel when the debris flow erodes the channel, unit: °.

[0603] Furthermore, in the control equation, the flash flood and debris flow along Directional bottom resistance and mountain torrents and mudslides Directional bottom resistance The calculation formula is as follows:

[0604] ;

[0605] ;

[0606] In the formula, is the density of mountain torrents and debris flows, unit: ;

[0607] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0608] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0609] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0610] is the density of particulate matter in mountain torrents and debris flows, unit: ;

[0611] is the density of clean water, unit: ;

[0612] is the roughness coefficient during the movement of mountain torrents, unit: ;

[0613] Depth of mountain torrents and debris flows, unit: ;

[0614] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0615] , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0616] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0617] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0618] Γ is the transition factor from flash flood to debris flow, unit: dimensionless;

[0619] and The liquid phase slurry of mountain torrent debris flow is Direction and Directional bed resistance, unit: ;

[0620] and They are respectively coarse particles of mountain torrents and debris flows along the Direction and Directional bed resistance, unit: ;

[0621] is the acceleration due to gravity (unit: ).

[0622] Furthermore, the liquid phase of the mountain torrent debris flow Directional bottom resistance and Directional bottom resistance The calculation formulas are:

[0623] ;

[0624] ;

[0625] In the formula, Depth of mountain torrents and debris flows, unit: ;

[0626] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0627] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0628] is the dynamic viscosity of clean water, unit: Pa·s;

[0629] Represents the volume concentration of fine particles in liquid mud, unit: dimensionless;

[0630] is the maximum allowable volume concentration of fine-grained sediment in liquid mud, unit: dimensionless, calculated as

[0631]

[0632] In the formula, d i Represents the fine-grained sediment i The diameter of a particle size class, unit: dimensionless;

[0633] p i Represents the fine-grained sedimenti The mass percentage of each particle size grade, unit: dimensionless;

[0634] S v0 It is the critical volume concentration at which the fluid changes from a Newtonian fluid to a Bingham fluid. Unit: dimensionless. The calculation formula is:

[0635] ;

[0636] k 0 is a correction factor, unit: dimensionless, expressed as:

[0637] ;

[0638] Understandably, It is the maximum allowable volume concentration of fine-grained sediment in liquid mud. Unit: dimensionless. This parameter is usually related to the specific surface area of ​​the particles.

[0639] Furthermore, the coarse particles of mountain torrents and debris flows are Directional bottom resistance and Directional bottom resistance The calculation formulas are:

[0640] ;

[0641] ;

[0642] In the formula, The coarse particles in the mountain torrents and debris flows The resistance to motion in the direction, in units: ;

[0643] The coarse particles in the mountain torrents and debris flows The resistance to motion in the direction, in units: ;

[0644] is the density of mountain torrents and debris flows, unit: ;

[0645] It is the density of liquid slurry composed of fine particles and water, unit: ;

[0646] is the volume concentration of water in the flash flood and debris flow, unit: dimensionless;

[0647] is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless;

[0648] is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless;

[0649] is the density of particulate matter in mountain torrents and debris flows, unit: ;

[0650] is the density of clean water, unit: ;

[0651] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0652] For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ;

[0653] For mountain torrents and mud-rock flows Directional flow velocity, unit: ;

[0654] For mountain torrents and mud-rock flows Flow velocity in direction, unit: ;

[0655] Depth of mountain torrents and debris flows, unit: ;

[0656] The bottom edge of the mountain torrent debris flow Slope in the direction, calculated from the terrain. Unit: °;

[0657] The bottom edge of the debris flow Slope in the direction, calculated from the terrain. Unit: °;

[0658] is the friction angle between coarse particles and the bottom bed in mountain torrents and debris flows, unit: °;

[0659] is the turbulence coefficient of coarse particles in mountain torrents and debris flows, unit: ;

[0660] , is the acceleration due to gravity, unit: .

[0661] Experimental example

[0662] A simulation was carried out using a ditch in Sichuan as an example. In August 2023, the ditch source was triggered by heavy rain to form a debris flow. The vegetation coverage rate of the ditch is 0.55, the vegetation penetration coefficient is 0.35, and the canopy drainage rate attenuation coefficient is 0.0039. , the total water storage capacity of the canopy is 0.002 When the crown water storage reaches the total water storage capacity, the drainage coefficient is 5×10 -5 ; The peak rainfall intensity of the rainstorm is 60 , lasting 1200 ; The stable permeability of the soil is 40 , the initial permeability of the soil is 3 ; The constant of the rainfall infiltration decay process over time is 0.5 ; The mass of sediment required per unit area to protect the original soil from further erosion is 3 The stripping coefficient of the original soil under the impact of raindrops without the influence of mountain torrent runoff is 3.4, the stripping coefficient of the silt sediment under the impact of raindrops is 154.7, the attenuation index of the effect of mountain torrent depth on the stripping coefficient of rainfall raindrops is 1.13, and the average diameter of rainfall raindrops is 0.003 ; When mountain torrents erode the original soil, the erosion resistance of the ditch bed material is 50 , the erosion resistance of gully bed materials when mountain torrents erode mountain torrent sediments is 10 The empirical coefficient of mountain torrents eroding the original soil is 0.00059 The empirical coefficient of mountain torrent erosion of mountain torrent sediments is 0.00062 When the debris flow erodes the original soil in the ditch, the friction angle of the original soil particles is 35°, and the cohesion of the original soil particles is 1000. The friction angle of flood-deposited granular material when debris flows erode flood sediments in the channel is 28°. The cohesion of flood sediments in the channel of debris flow erosion is 300 ; The roughness coefficient of rainfall and mountain torrent runoff in the channel is 0.06 . Volume percentage of water in the bottom channel is 0.35 (unit: dimensionless), the volume percentage of coarse particles in the bottom channel material 0.38 (unit: dimensionless), the volume percentage of fine particles in the bottom channel material is 0.27 (unit: dimensionless), the bottom bed porosity The value is 0.35 (unit: dimensionless). During the movement of mountain torrents, the empirical parameters of particle sedimentation are , with a value of 3.0 (unit: dimensionless). The density of flash flood particulate matter , the density of clean water The friction angle between coarse particles and the bottom of debris flow is 28°, and the turbulence coefficient of coarse particles in debris flow is 25.5 ; Representative particle size of coarse particles during flash flood movement The value is 0.008 , the representative particle size of fine particles during flash flood movement The value is 0.0005 ; Friction angle between channel particles at coarse particle single width sediment transport rate is 30°. The particle grading curve of debris flow is as follows Figure 1 According to the 1:10000 topographic map of the ditch, a digital elevation model (DEM) of the debris flow ditch basin was established. The above parameters were input into the numerical model to obtain the formation and movement process of mountain torrent debris flow under rainfall conditions. Figure 2 The calculation results show that under the above parameter conditions, the maximum density of mountain torrents and debris flows is 1759 , successfully realizing the transformation process of mountain torrents into debris flows under rainfall conditions.

[0663] Figure 2 In the figure, (a) the depth distribution of mountain torrent debris flow in 15 minutes; (b) the velocity distribution of mountain torrent debris flow in 15 minutes; (c) the volume concentration distribution of coarse particles of mountain torrent debris flow in 15 minutes; (d) the volume concentration distribution of fine particles of mountain torrent debris flow in 15 minutes.

[0664] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A numerical simulation method for rainfall-induced mountain torrents and debris flows, characterized in that: include: Based on the fluid mechanics model of the three-phase medium of water, coarse particles and fine particles coupled by the continuum mechanics method, the data required by the numerical simulation method are obtained, wherein the data include at least one of the topographic data, the time series data of rainfall, the vegetation distribution data, and the volume content of the initial coarse particles and fine particles in the ditch bed; The governing equations of the fluid mechanics model are: ； ； ； In the formula, Depth of mountain torrents and debris flows, unit: ; , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; For mountain torrents and mud-rock flows Flow velocity in direction, unit: ; is the density of mountain torrents and debris flows, unit: ; is the volume concentration of water in the flash flood and debris flow, unit: dimensionless; is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless; is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless; is the density of particulate matter in mountain torrents and debris flows, unit: ; is the density of clean water, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; The elevation of the terrain required for numerical simulation, unit: ; , is the acceleration due to gravity, unit: ; Represents effective rainfall intensity, unit: ; is the soil permeability, unit: ; is the total erosion rate of mountain torrents and debris flows, unit: ; It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ; is the total deposition rate of particulate matter in mountain torrents and debris flows, unit: ; is the deposition rate of fine particles in mountain torrents and debris flows, unit: ; is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ; is time, unit: ; In a flash flood and debris flow, the transport equations for water, fine particles, and coarse particles are: ； ； ； In the formula, Depth of mountain torrents and debris flows, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; For mountain torrents and mud-rock flows Flow velocity in direction, unit: ; is the volume concentration of water in the flash flood and debris flow, unit: dimensionless; is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless; is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless; Represents effective rainfall intensity, unit: ; is the soil permeability, unit: ; It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ; is the deposition rate of fine particles in mountain torrents and debris flows, unit: ; is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ; is the diffusion coefficient of fine particles in mountain torrents and debris flows, unit: ; is time, unit: ; and / or The evolution equation of the terrain is: ； In the formula, is the trench bed porosity, unit: dimensionless; is the elevation of the terrain, in units: ; is the total erosion rate of mountain torrents and debris flows, unit: ; It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ; is the total deposition rate of particulate matter in mountain torrents and debris flows, unit: ; is the deposition rate of fine particles in mountain torrents and debris flows, unit: ; is the deposition rate of coarse particles in mountain torrents and debris flows, unit: ; is the sediment transport rate per unit width along the x direction, unit: ; is the sediment transport rate per unit width along the y direction, unit: ; is time, unit: .

2. The numerical simulation method of rainfall-induced mountain torrents and debris flows according to claim 1 is characterized in that: In the control equation, the effective rainfall intensity The calculation formula is: ； In the formula, Represents effective rainfall intensity, unit: ; is the actual rainfall intensity, in units: ; is the vegetation coverage, unit: dimensionless; is the vegetation penetration coefficient, unit: dimensionless; is the crown drainage rate, in: ; Crown drainage rate The calculation formula is: ； In the formula, is the crown drainage rate, in: ; is the attenuation coefficient of the crown drainage rate, unit: ; is the total water storage capacity of the tree crown, unit: ; for The crown water storage at the moment, unit: ; It is the drainage coefficient when the crown water storage reaches the total water storage capacity, unit: ; exist Crown water storage at any time The calculation equation is: ； In the formula, for The crown water storage at the moment, unit: ; is the vegetation penetration coefficient, unit: dimensionless; is the actual rainfall intensity, in units: ; is the vegetation coverage, unit: dimensionless; is the crown drainage rate, in: ; is time, unit: ; and / or In the control equation, soil permeability The calculation formula is: ； In the formula, is the soil permeability, unit: ; is the stable permeability of the soil, unit: ; is the initial permeability of the soil, unit: ; is a constant describing the attenuation of rainfall infiltration over time, unit: ; is time, unit: ; and / or In the control equation, the total erosion rate of mountain torrents and debris flows is The calculation method is: ； In the formula, is the total erosion rate of mountain torrents and debris flows, unit: ; is the total sediment splashing rate of gully bed material caused by rainfall, unit: ; is the total erosion rate of mountain torrents on ditch bed sediment, unit: ; is the total debris flow erosion rate, unit: ; Γ is the transition factor from flash flood to debris flow, unit: dimensionless; The calculation formula of Γ is: ； Where α is the attenuation exponent, unit: dimensionless, value is 13.8; is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless; is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless; It is the critical total particulate matter concentration that separates mountain torrents from debris flows. Unit: dimensionless, with a value of 0.

18.

3. The numerical simulation method of rainfall-induced mountain torrents and debris flows according to claim 2 is characterized in that: Total sediment splashing rate of gully bed materials caused by moderate rainfall Including the original soil sediment splash rate and splash erosion rate of mountain torrent sediment Two parts, namely ； ； ； In the formula, is the sediment splash rate caused by rainfall, unit: ; is the total splash erosion rate of original soil sediment caused by rainfall, unit: ; is the total sediment splashing rate of mountain torrent sediment caused by rainfall, unit: ; Represents the effective rainfall intensity, unit: ; It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless; It is the total sediment mass of mountain torrents per unit area, unit: ; It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ; It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ; It is the mass of sediment required to protect the original soil from further erosion per unit area, in units of: ; is the stripping coefficient of the original soil under the impact of raindrops, unit: dimensionless; It is the stripping coefficient of sediment under the impact of raindrops, unit: dimensionless.

4. The numerical simulation method of rainfall-induced mountain torrents and debris flows according to claim 3 is characterized in that: Calculate the extent to which a sediment cover protects a riverbed from erosion The mass of fine-grained sediment per unit area of ​​the mountain torrent used and the mass of coarse sediment per unit area of ​​mountain torrents The calculation equations are: ； ； In the formula, It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ; It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ; is the density of the sediment, in units of: ; is the trench bed porosity, unit: dimensionless; is the fine-grained sediment deposition rate, unit: ; is the splashing rate of fine-grained sediment in mountain torrent sediment by rainfall, unit: ; is the erosion rate of fine-grained sediment in mountain torrent sediment by mountain torrents, unit: ; is the fine-grained sediment deposition rate, unit: ; is the splashing rate of coarse sediment in sediment sediments by rainfall, unit: ; is the erosion rate of coarse sediment in sediment by mountain torrents, unit: ; is the total erosion rate of mountain torrents on ditch bed sediment, unit: ; is the sediment transport rate of coarse particles per width along the x direction, unit: ; is the sediment transport rate of coarse particles per width along the y direction, unit: ; and / or Calculate the extent to which a sediment cover protects a riverbed from erosion The stripping coefficient of the original soil under the raindrop impact used The stripping coefficient of sediment under raindrop impact The calculation method is: ； ； In the formula, is the stripping coefficient of the original soil under the impact of raindrops, unit: dimensionless; is the stripping coefficient of the original soil under the impact of raindrops when there is no influence of mountain torrent runoff, unit: dimensionless; is the stripping coefficient of sediment under raindrop impact, unit: dimensionless; is the stripping coefficient of sediment under the impact of raindrops when there is no mountain torrent runoff, unit: dimensionless; is the critical flash flood depth at which rainfall can directly strip away sediment particles, unit: ; is the average diameter of rainfall drops, unit: ; is the depth of flash flood perpendicular to the channel direction, unit: ; is the calculated flash flood depth, unit: ; is the channel slope, calculated from the topography, unit: °; It is the attenuation index of the effect of flash flood depth on the rainfall drop stripping coefficient.

5. The numerical simulation method of rainfall-induced mountain torrents and debris flows according to claim 4 is characterized in that: Total erosion rate of gully bed materials by medium mountain torrents Including the erosion rate of original soil and sediment by mountain torrents and mountain torrent erosion rate of mountain torrent sediment Two parts, namely ； ； ； In the formula, is the total erosion rate of mountain torrents on gully bed materials, unit: ; is the erosion rate of mountain torrents on the original soil sediment, unit: ; is the erosion rate of mountain torrents on mountain torrent sediment, unit: ; It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless; is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; It is the anti-erosion capacity of the ditch bed material when mountain torrents erode the original soil, unit: ; It is the erosion resistance of the gully bed material when the mountain torrent erodes the mountain torrent sediment, unit: ; It is the empirical coefficient of mountain torrent erosion of original soil, unit: ; It is the empirical coefficient of mountain torrent erosion of mountain torrent sediments, unit: ; and / or Debris flow erosion rate Including the erosion rate of original soil and sand by debris flow The erosion rate of mountain torrent sediment and debris flow Two parts, the calculation equation is: ； ； ； In the formula, is the debris flow erosion rate, unit: ; is the erosion rate of the original soil and sand by debris flow, unit: ; is the erosion rate of debris flow on mountain torrent sediment, unit: ; It refers to the degree to which the sediment cover protects the riverbed from erosion. Unit: dimensionless; is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; is the density of mountain torrents and debris flows, unit: ; The calculated depth of mountain torrents and debris flows, unit: ; It is the pore water pressure coefficient in the ditch bed material when debris flow erodes the ditch, unit: dimensionless; is the channel slope, calculated from the topography, unit: °; It is the friction angle of the original soil particles when the debris flow erodes the original soil in the channel, unit: °; It is the cohesion of the original soil particles in the original soil when the debris flow erodes the original soil in the gully, unit: ; It is the friction angle of flood-deposited granular material when debris flow erodes flood sediments in the channel, unit: °; It is the cohesion of flood sediments when debris flow erodes flood sediments in the channel, unit: ; is the acceleration due to gravity, unit: .

6. The numerical simulation method of rainfall-induced mountain torrents and debris flows according to claim 5 is characterized in that: In the transport equation, the erosion rate of water in the gully bed by mountain torrents and debris flows is , erosion rate of coarse particles and erosion rate of fine particulate matter , are calculated by the following formulas: ； ； ； In the formula, It is the erosion rate of water in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of coarse particles in the movement of mountain torrents and debris flows, unit: ; is the erosion rate of fine particles in the movement of mountain torrents and debris flows, unit: ; Γ is the transition factor from flash flood to debris flow, unit: dimensionless; It is the mass of fine-grained sediment deposited by mountain torrents per unit area, unit: ; It is the mass of coarse sediment deposited by mountain torrents per unit area, unit: ; is the volume fraction of water in the original soil in the channel, unit: dimensionless; is the volume fraction of coarse-grained material in the original soil in the channel, unit: dimensionless; is the volume fraction of fine particulate matter in the original soil in the channel, unit: dimensionless; is the total splash erosion rate of original soil sediment caused by rainfall, unit: ; is the total sediment splashing rate of mountain torrent sediment caused by rainfall, unit: ; is the erosion rate of mountain torrents on the original soil sediment, unit: ; is the erosion rate of mountain torrents on mountain torrent sediment, unit: ; is the erosion rate of the original soil and sand by debris flow, unit: ; is the erosion rate of debris flow on mountain torrent sediment, unit: ; is the trench bed porosity, unit: dimensionless; and / or Diffusion coefficient of fine particle matter in the fine particle transport equation The calculation formula is as follows: ； In the formula, is the diffusion coefficient of fine particles in mountain torrents and debris flows, unit: ; κ = 0.4 represents the von Karman constant, unit: dimensionless; is the friction velocity of the bed surface of the mountain torrent and debris flow, unit: ; is the combined resistance of the bottom bed of mountain torrents and debris flows, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; is the density of mountain torrents and debris flows, unit: ; h is the depth of mountain torrents and debris flows, unit: ; and / or In the transport equations for fine and coarse particles, the deposition rates of fine and coarse sediment in flash flood runoff are calculated as follows: ； ； In the formula, is the deposition rate of fine particles in flash floods, unit: ; is the deposition rate of coarse particles in flash floods, unit: ; is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless; is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless; It is an empirical parameter, with a value of 2.0~5.0, unit: dimensionless; Γ is the transition factor from flash flood to debris flow, unit: dimensionless; is the sedimentation rate of fine particles in mountain torrents, unit: , the calculation formula is: ； In the formula, is the kinematic viscosity of clean water, unit: ; It is the representative particle size of fine particles in the process of mountain torrent movement, unit: ; is the density of fine particles in mountain torrents and debris flows, unit: ; is the density of clean water, unit: ; is the acceleration due to gravity, unit: ; is the sedimentation rate of coarse particles in mountain torrents, unit: , the calculation formula is: ； In the formula, is the kinematic viscosity of clean water, unit: ; It is the representative particle size of coarse particles in the process of mountain torrent movement, unit: ; is the density of coarse particles in mountain torrents and debris flows, unit: ; is the density of clean water, unit: ; is the acceleration due to gravity, unit: .

7. The numerical simulation method of rainfall-induced mountain torrents and debris flows according to claim 4 is characterized in that: formula and The sediment transport rate of coarse particles per width along the x direction is and the sediment transport rate of coarse particles per width along the y direction The calculation methods are: ； ； In the formula, is the sediment transport rate of coarse particles per width along the x direction, unit: ; is the sediment transport rate of coarse particles per width along the y direction, unit: ; For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; Coarse particle single width sediment transport rate, unit: , the calculation formula is: ； In the formula, is the Froude number of the fluid, unit: dimensionless; Depth of mountain torrents and debris flows, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; For mountain torrents and mud-rock flows Flow velocity in direction, unit: ; is the Shields number, unit: dimensionless; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; For mountain torrents and mud-rock flows Directional bed resistance, unit: ; is the density of coarse particles in mountain torrents and debris flows, unit: ; is the density of clean water, unit: ; It is the representative particle size of coarse particles in the process of mountain torrent movement, unit: ; is the acceleration due to gravity, unit: ; is the critical Shields number, unit: dimensionless, calculated as: ； In the formula, is the empirical coefficient, unit: dimensionless; is the channel slope, calculated from the topography, unit: °; It is the friction angle of the granular material in the channel when the debris flow erodes the channel, unit: °.

8. The numerical simulation method of rainfall-induced mountain torrents and debris flows according to claim 1, characterized in that: Mountain floods and mudslides Directional bottom resistance and mountain torrents and mudslides Directional bottom resistance The calculation formula is as follows: ； ； In the formula, is the density of mountain torrents and debris flows, unit: ; is the volume concentration of water in the flash flood and debris flow, unit: dimensionless; is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless; is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless; is the density of particulate matter in mountain torrents and debris flows, unit: ; is the density of clean water, unit: ; is the roughness coefficient during the movement of mountain torrents, unit: ; Depth of mountain torrents and debris flows, unit: ; , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; , for mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; For mountain torrents and mud-rock flows Flow velocity in direction, unit: ; Γ is the transition factor from flash flood to debris flow, unit: dimensionless; and The liquid phase slurry of mountain torrent debris flow is Direction and Directional bed resistance, unit: ; and They are respectively coarse particles of mountain torrents and debris flows along the Direction and Directional bed resistance, unit: ; is the acceleration due to gravity, unit: ; Liquid slurry of mountain torrents and debris flows Directional bottom resistance and Directional bottom resistance The calculation formulas are: ； ； In the formula, Depth of mountain torrents and debris flows, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; For mountain torrents and mud-rock flows Flow velocity in direction, unit: ; is the dynamic viscosity of clean water, unit: Pa·s; Represents the volume concentration of fine particles in liquid mud, unit: dimensionless; is the maximum allowable volume concentration of fine-grained sediment in liquid mud, unit: dimensionless, calculated as ； In the formula, d i Represents the fine-grained sediment i The diameter of a particle size class, unit: dimensionless; p i Represents the fine-grained sediment i The mass percentage of each particle size grade, unit: dimensionless; S v0 It is the critical volume concentration at which the fluid changes from a Newtonian fluid to a Bingham fluid. Unit: dimensionless. The calculation formula is: ； k 0 is a correction factor, unit: dimensionless, expression: ； Coarse particles of mountain torrents and debris flows Directional bottom resistance and Directional bottom resistance The calculation formulas are: ； ； In the formula, The coarse particles in the mountain torrents and debris flows The resistance to motion in the direction, in units: ; The coarse particles in the mountain torrents and debris flows The resistance to motion in the direction, in units: ; is the density of mountain torrents and debris flows, unit: ; It is the density of liquid slurry composed of fine particles and water, unit: ; is the volume concentration of water in the flash flood and debris flow, unit: dimensionless; is the volume concentration of coarse particles in flash floods and debris flows, unit: dimensionless; is the volume concentration of fine particles in flash floods and debris flows, unit: dimensionless; is the density of particulate matter in mountain torrents and debris flows, unit: ; is the density of clean water, unit: ; For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; For mountain torrents and mud-rock flows Single-width flow in a direction, unit: ; For mountain torrents and mud-rock flows Directional flow velocity, unit: ; For mountain torrents and mud-rock flows Flow velocity in direction, unit: ; Depth of mountain torrents and debris flows, unit: ; The bottom edge of the mountain torrent debris flow Slope in the direction, calculated from the terrain. Unit: °; The bottom edge of the debris flow Slope in the direction, calculated from the terrain. Unit: °; is the friction angle between coarse particles and the bottom bed in mountain torrents and debris flows, unit: °; is the turbulence coefficient of coarse particles in mountain torrents and debris flows, unit: ; , is the acceleration due to gravity, unit: .

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