A dynamic numerical identification process of ice lake outburst type mountain torrents and debris flow

Abstract

The present application relates to a kind of ice lake breaching type mountain torrents and dynamic numerical identification process of debris flow, belong to mountain disaster prevention technical field, the numerical classification process includes: S1, obtain the basic data of ice lake and the river basin where it is located;S2, establish ice lake breaching mathematical model by the basic data, and calculate the breaching hydraulic characteristics of ice lake;S3, establish the water-soil coupling fluid motion equation on the channel of target river basin by the basic data, by simulating ice lake breaching process and the evolution process of fluid on channel, describe the fluid motion state, then according to water-soil coupling fluid motion parameter, calculate the volume concentration of glacial material source in fluid;S4, select glacial material source classification volume concentration as classification index.The dynamic numerical identification process of ice lake breaching type mountain torrents and debris flow is calculated by ice dam, channel and multiple dimensions of hydraulic characteristics, the nature of ice lake breaching fluid is characterized by numerical operation, improve the accuracy of ice lake breaching fluid property judgment, realize the dynamic classification of ice lake breaching type mountain torrents and debris flow.

Description

Technical Field

[0001] This invention belongs to the field of mountain disaster prevention technology, and specifically relates to a dynamic numerical identification process for glacial lake outburst floods and debris flows. Background Technology

[0002] Glacial lake outburst floods and debris flows fall under the responsibility of the water resources and natural resources departments, respectively. Identifying the type of glacial lake outburst flood and debris flow is crucial for emergency management decision-making. Currently, the determination of glacial lake outburst floods and debris flows is often made by measuring the weight per unit volume of samples. However, glacial lake outburst floods and debris flows typically occur in high-altitude continental glacial areas, their outbreaks are sudden and short-lived, making it difficult to promptly identify the type of disaster. Furthermore, glacial lake outburst floods and debris flows can transform into each other under different geological environments. The interconversion between glacial lake outburst floods and debris flows increases the difficulty of determining the nature of glacial lake outburst fluids and poses challenges to the prevention and control of glacial lake outburst floods and debris flows. Chinese patent CN202011624869.5 provides a method, device, and storage medium for post-earthquake glacial lake outburst flood early warning. This patent points out that the determination of whether a fluid is a debris flow or a flood is made by comparing the longitudinal gradient of the channel in the early warning basin and the abundance of loose material sources with the corresponding set thresholds. However, the determination of whether a flood or a debris flow is a flood or a debris flow is not only related to the parameter information of the target basin, but also has an inseparable relationship with the parameter information of the glacial moraine dam. Therefore, the existing methods for classifying the nature of outburst fluids need to be improved. Summary of the Invention

[0003] This invention provides a dynamic numerical identification process for glacial lake outburst floods and debris flows, which solves the technical problems of non-real-time and inaccurate classification of fluid properties in existing glacial lake outburst floods.

[0004] This invention is achieved through the following technical solution: a dynamic numerical identification process for glacial lake outburst floods and debris flows, comprising the following steps:

[0005] S1, Obtain basic data on the glacial lake and its watershed;

[0006] S2, Establish a mathematical model of glacial lake outburst using the aforementioned basic data, and calculate the outburst hydraulic characteristics of the glacial lake;

[0007] S3. Based on the basic data, establish the water-soil coupled fluid motion equation on the channel of the target watershed. By simulating the glacial lake outburst process and the evolution process of the fluid on the channel, describe the water-soil coupled fluid motion state, and then calculate the volume concentration of glacial till source in the fluid based on the water-soil coupled fluid motion parameters.

[0008] S4. Select the volume concentration of glacial moraine source as the classification index. When the volume concentration of glacial moraine source in the fluid is greater than or equal to the volume concentration of glacial moraine source, the fluid is determined to be a debris flow. When the volume concentration of glacial moraine source in the fluid is less than the volume concentration of glacial moraine source, the fluid is determined to be a flash flood.

[0009] Optionally, to better implement the present invention, the basic data includes the geometric characteristics of the glacial till, the material characteristics of the glacial till, the channel slope of the target watershed, the source characteristics of the glacial till in the channel, and the inflow characteristics. Based on the basic data, the water and sediment hydraulic characteristics are calculated using the following formula:

[0010] ;

[0011] In the formula, E is the glacial till source pickup flux, representing the volume of glacial till source initiated per unit area of ​​channel per unit time; d 50 ρ is the median grain size of the glacial till source; g is the gravitational acceleration; s is the relative density; D denoted as dimensionless parameters of the glacial till source particles, and T is a dimensionless parameter characterizing the motion state of the glacial till source particles.

[0012] Optionally, to better implement the present invention, the solid material in the fluid includes a glacial till source, and the formula for calculating the volume concentration of the glacial till source in the fluid is:

[0013] ;

[0014] In the formula, c b denoted as ρ, where ρ is the volume concentration of the glacial till source in the fluid; u is the fluid velocity; h is the fluid depth; E is the glacial till source pick-up flux; D is the volume concentration of the glacial till source. Dimensionless parameters of the source particles of glacial till, where T is a dimensionless parameter characterizing the motion state of the source particles of glacial till; d 50 The median particle size of the glacial till source is given.

[0015] Optionally, in order to better implement the present invention, the glacial lake outburst mathematical model includes a transverse outburst model and a vertical outburst model, wherein the transverse outburst model represents the transverse erosion rate of the breach and the vertical outburst model represents the incision erosion rate of the breach.

[0016] Optionally, to better implement the present invention, the erosion formula of the transverse collapse model is:

[0017] ;

[0018] In the formula, k represents the erosion rate. d Let τ be the erosion coefficient. b For fluid shear stress, τ c The critical starting shear stress of the glacial till source particles.

[0019] Optionally, to better implement the present invention, the erosion formula of the vertical collapse model is:

[0020] ;

[0021] In the formula, n loc Here are the parameters for the breach location (2 for breaches in the middle of the glacial tillage dam, and 1 for breaches at the abutment of the glacial tillage dam), β is the toe angle of the breach slope, and Δz is the location parameter. b This represents the increment in erosion depth.

[0022] Optionally, to better implement the present invention, the volume concentration of the glacial till source is 27%.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] This invention provides a dynamic numerical identification process for glacial lake outburst floods and debris flows: S1, acquiring basic data on the glacial lake and its watershed; S2, establishing a mathematical model of glacial lake outburst floods using the basic data and calculating the hydraulic characteristics of the glacial lake outburst; S3, establishing water-soil coupled fluid motion equations on the channels of the target watershed using the basic data, describing the water-soil coupled fluid motion state by simulating the glacial lake outburst process and the fluid evolution process on the channels, and then calculating the volume concentration of glacial moraine source in the fluid based on the water-soil coupled fluid motion parameters; S4, selecting the glacial moraine source classification volume concentration as a classification index. When the glacial moraine source volume concentration in the fluid is greater than or equal to the glacial moraine source classification volume concentration, the fluid is determined to be a debris flow; when the glacial moraine source volume concentration in the fluid is less than the glacial moraine source classification volume concentration, the fluid is determined to be a flash flood.

[0025] Through the above steps, the dynamic numerical identification process for glacial lake outburst floods and debris flows provided by this invention improves the accuracy of judging the fluid properties of glacial lake outburst floods through multi-parameter calculation, and realizes the dynamic classification of glacial lake outburst floods and debris flows. Specifically, the study obtains information on the morphological characteristics of glacial moraine dams and the source composition of glacial moraine on the surface of the dams to facilitate the establishment of a mathematical model for the glacial lake outburst process. This model allows for the calculation of the impact of glacial moraine dams on the classification of outburst fluid properties. Furthermore, it obtains information on the channel slope and source composition of the target watershed to facilitate the establishment of outburst hydraulic characteristics and water-soil coupled fluid motion equations during the glacial lake outburst process. By combining the glacial lake outburst process with the fluid evolution in the channel, the study describes the water-soil coupled fluid motion state. The study then uses numerical methods to calculate the source content of glacial moraine in the outburst fluid, determining the critical glacial moraine source content value between debris flows and flash floods. This value is compared with the calculated source content value to determine whether the outburst fluid is a flash flood or a debris flow. Therefore, the dynamic numerical identification process for glacial lake outburst floods and debris flows calculates the characteristics of glacial lake outburst fluids from multiple dimensions, including glacial lakes, channels, and hydraulic features. It characterizes the properties of glacial lake outburst fluids through numerical calculations, thereby improving the accuracy of judging the properties of glacial lake outburst fluids and realizing the dynamic classification of glacial lake outburst floods and debris flows. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of dynamic numerical identification of glacial lake outburst floods and debris flows provided in an embodiment of the present invention;

[0028] Figure 2 This is a discrete distribution diagram of the numerical experiments in the embodiments of the present invention;

[0029] Figure 3 This is a fluid property judgment diagram from a numerical experiment in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] Example

[0032] This embodiment provides a dynamic numerical identification process for glacial lake outburst floods and debris flows, addressing the existing technical problems of non-real-time and inaccurate classification of fluid properties in glacial lake outburst floods. The numerical classification process includes the following steps:

[0033] S1. Obtain basic data on the glacial lake and its watershed. Before obtaining the basic data, the location of the glacial lake and its watershed are determined in advance. Then, regional geological maps and topographic maps are obtained through field surveys and remote sensing interpretation to obtain the corresponding basic data, which will serve as data support for the subsequent classification of the properties of the glacial lake outburst fluid.

[0034] S2. Establish a mathematical model of glacial lake outburst using basic data and calculate the outburst hydraulic characteristics of glacial lakes. The outburst hydraulic characteristics can be calculated using hydrodynamic equations such as the Navier-Stokes equation, the shallow water equation, or the wave equation, based on a clear outburst mathematical model.

[0035] S3 establishes the water-soil coupled fluid motion equations in the channels of the target watershed using basic data. By simulating the glacial lake outburst process and the fluid evolution in the channels, the water-soil coupled fluid motion state is described. Then, based on the water-soil coupled fluid motion parameters, the volume concentration of glacial till in the fluid is calculated. The calculation methods for the hydraulic characteristics of the glacial lake outburst and the hydraulic characteristics of the channels are similar. The real-time volume concentration of glacial till in the fluid is characterized by analyzing the evolution of the glacial lake and channels during the outburst process.

[0036] S4. The volume concentration of glacial moraine source is selected as the classification index. When the volume concentration of glacial moraine source in the fluid is greater than or equal to the volume concentration of glacial moraine source, the fluid is determined to be a debris flow. When the volume concentration of glacial moraine source in the fluid is less than the volume concentration of glacial moraine source, the fluid is determined to be a flash flood.

[0037] Through the above steps, the dynamic numerical identification process for glacial lake outburst floods and debris flows provided in this embodiment improves the accuracy of judging the fluid properties of glacial lake outburst floods through multi-parameter calculation, and realizes the dynamic classification of glacial lake outburst floods and debris flows. Specifically, the morphological characteristics of glacial moraine dams and the source composition of glacial moraine on the surface of glacial moraine dams are obtained to facilitate the establishment of a mathematical model for the glacial lake outburst process, thereby calculating the impact of glacial moraine dams on the classification of outburst fluids. The channel slope and source composition of the target watershed are also obtained to facilitate the establishment of outburst hydraulic characteristics and water-soil coupled fluid motion equations during glacial lake outburst processes. Combining the glacial lake outburst process and the fluid evolution process in the channel, the motion state of water-soil coupled fluids is described. The content of glacial moraine in the outburst fluid is calculated numerically, and the critical glacial moraine content value between debris flows and flash floods is determined. This content value is compared with the calculated glacial moraine content value to determine whether the outburst fluid is a flash flood or a debris flow. Therefore, the dynamic numerical identification process for glacial lake outburst floods and debris flows calculates the characteristics of glacial lake outburst fluids from multiple dimensions, including glacial lakes, channels, and hydraulic features. It characterizes the properties of glacial lake outburst fluids through numerical calculations, thereby improving the accuracy of judging the properties of glacial lake outburst fluids and realizing the dynamic classification of glacial lake outburst floods and debris flows.

[0038] An optional implementation method of this embodiment is as follows: The basic data includes the geometric characteristics of the glacial moraine dam, the glacial moraine source characteristics of the glacial moraine dam, the channel slope of the target watershed, the glacial moraine source characteristics of the channel, and the inflow characteristics. The water and sediment hydraulic characteristics are calculated based on the basic data, and the calculation formula is as follows:

[0039] ;

[0040] In the formula, E is the glacial till source pickup flux, representing the volume of glacial till source initiated per unit area of ​​channel per unit time; d 50 ρ is the median grain size of the glacial till source; g is the gravitational acceleration; s is the relative density; D denoted as dimensionless parameters of the glacial till source particles, and T is a dimensionless parameter characterizing the motion state of the glacial till source particles.

[0041] Optionally, the formula for calculating the volume concentration of glacial till source in the fluid is:

[0042] ;

[0043] In the formula, c b denoted as ρ, where ρ is the volume concentration of the glacial till source in the fluid; u is the fluid velocity; h is the fluid depth; E is the glacial till source pickup flux; D is the volume concentration of the glacial till source. Dimensionless parameters of the source particles of glacial till, where T is a dimensionless parameter characterizing the motion state of the source particles of glacial till; d 50 The median particle size of the glacial till source is given.

[0044] An optional implementation of this embodiment is as follows: The mathematical model of glacial lake outburst flooding includes a horizontal outburst flooding model and a vertical outburst flooding model. The horizontal outburst flooding model represents the horizontal erosion rate of the breach, and the vertical outburst flooding model represents the downward erosion rate of the breach.

[0045] Alternatively, the erosion formula for the lateral collapse model is:

[0046] ;

[0047] In the formula, k represents the erosion rate. d Let τ be the erosion coefficient. b For fluid shear stress, τ c The critical starting shear stress of the glacial till source particles.

[0048] Optionally, the erosion formula for the vertical collapse model is:

[0049] ;

[0050] In the formula, n loc Here are the parameters for the breach location (2 for breaches in the middle of the glacial tillage dam, and 1 for breaches at the abutment of the glacial tillage dam), β is the toe angle of the breach slope, and Δz is the location parameter. b This represents the increment in erosion depth.

[0051] An optional implementation of this embodiment is as follows: the classification volume concentration is 27%. Thus, when the solid volume concentration in the fluid is less than 27%, the fluid is identified as a flash flood, and when the volume concentration of glacial till in the fluid is greater than 27%, the fluid is identified as a debris flow. Therefore, the nature of the fluid is determined by establishing a mathematical model to analyze the volume concentration of glacial till in the fluid.

[0052] To better understand the technical solution and verify the effectiveness of the method, a water tank was used instead of a real ice lake outburst flood tank test to dynamically identify the properties of the outburst fluid:

[0053] The experimental water tank includes a lifting system, a water supply device, a rectangular cross-section water tank, and a waste collection device. The experimental water tank is 12m long, 0.3m wide, and 1m high. Referring to the characteristics of glacial till, coarse sand was used as the experimental material, with a median particle size d. 50 The thickness is 1.75 mm, and the uniformity coefficient is 1.75. The paving density of both the dam body and the riverbed is set to 1.5 g / cm³, the riverbed slope θ is set to 11°, the paving length of the movable bed is set to 5 m, and the paving thickness of the riverbed is set to 5 cm. The inflow rate is set to 6.6 L / s.

[0054] After the collapse, samples of the water-source particle mixture were taken at designated locations at regular intervals. The total volume and mass of the samples were recorded. The source particles in the samples were then dried to obtain their mass and volume. Finally, the fluid volume concentration could be obtained using the following formula:

[0055] ;

[0056] In the formula, c is the volume concentration, and V 砂 and V 总 These represent the volume of the source particles in the sample and the total volume of the sample, respectively.

[0057] Numerical experiments were conducted using MATLAB to compare the measured volume concentration values ​​from physical experiments with the calculated values, thus verifying the accuracy of the proposed method. The MATLAB simulation was set within a rectangular river channel in the range [0m, 12m]. The bed elevation was set as a slope condition, and the friction term was considered in the shallow water equations, with a CFL coefficient of 0.8. The upstream boundary condition was an inflow boundary, and the downstream boundary condition was an open boundary. The initial upstream water depth was 0m, the initial upstream velocity was 0m / s, and the initial upstream inflow unit width discharge was also set to 0m³ / s. 2 / s; The initial time of the model's computation is set to the time of water release, and the computation of the model ends when the glacial lake is completely destroyed.

[0058] The results of the numerical and physical experiments are attached. Figure 2 As shown, the measured and calculated values ​​of volume concentration are quite close, indicating that the method established in this invention is correct and can effectively describe the formation and evolution of glacial lake outburst floods and debris flows. Furthermore, according to the appendix... Figure 3 It can be seen that in the early stage of the collapse (around 9.5 seconds), the outflow volume concentration is relatively high, and the fluid at this stage is a debris flow; after 9.5 seconds, the fluid volume concentration decreases rapidly and remains below c. b =0.27, the fluid is a flash flood.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope described in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dynamic numerical identification process for glacial lake outburst floods and debris flows, characterized in that, The steps include the following: S1, Obtain basic data on the glacial lake and its watershed; S2, Establish a mathematical model of glacial lake outburst using the aforementioned basic data, and calculate the outburst hydraulic characteristics of the glacial lake; The mathematical model for glacial lake outburst flooding includes a horizontal outburst model and a vertical outburst model. The horizontal outburst model represents the horizontal erosion rate of the breach, and the vertical outburst model represents the downward erosion rate of the breach. The erosion formula of the lateral collapse model is: ； In the formula, For the erosion rate, The erosion coefficient is... For fluid shear stress, The critical initiation shear stress for glacial till source particles; The erosion formula for the vertical collapse model is: ； In the formula, For the location parameter of the rupture, The angle at the toe of the breach slope. For the increment of erosion depth; S3. Based on the basic data, establish the water-soil coupled fluid motion equation on the channel of the target watershed. By simulating the glacial lake outburst process and the evolution process of the fluid on the channel, describe the water-soil coupled fluid motion state, and then calculate the volume concentration of glacial till in the fluid based on the water-soil coupled fluid motion parameters. S4. Select the volume concentration of glacial moraine source as the classification index. When the volume concentration of glacial moraine source in the fluid is greater than or equal to the volume concentration of glacial moraine source, the fluid is determined to be a debris flow. When the volume concentration of glacial moraine source in the fluid is less than the volume concentration of glacial moraine source, the fluid is determined to be a flash flood.

2. The dynamic numerical identification process for glacial lake outburst floods and debris flows according to claim 1, characterized in that, The basic data includes the geometric characteristics of the glacial till, the material characteristics of the glacial till, the channel slope of the target watershed, the source characteristics of the glacial till in the channel, and the inflow characteristics. Based on this basic data, the water and sediment hydraulic characteristics are calculated using the following formula: ； In the formula, The moraine source pickup flux represents the volume of moraine source activated per unit area of ​​channel per unit time. The median grain size of the glacial till source material; It is the acceleration due to gravity; For relative density, These are dimensionless tillite source particle parameters. Dimensionless parameters characterizing the motion state of glacial till source particles.

3. The dynamic numerical identification process for glacial lake outburst floods and debris flows according to claim 2, characterized in that, The solid matter in the fluid includes the glacial till source, and the volume concentration of the solid matter in the fluid is calculated using the following formula: ； In the formula, This represents the volume concentration of solid substances in the fluid. The fluid velocity; The fluid depth.

4. The dynamic numerical identification process for glacial lake outburst floods and debris flows according to claim 1, characterized in that: The volume concentration of the glacial till source was 27%.

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